Projection type image display device

专利摘要:
A light source 1, an image display panel 8 having a plurality of pixel regions each of which can modulate light, and light control means 4 for condensing light from the light source 1 to corresponding pixel regions according to the wavelength range 6) and optical systems 9 and 11 for forming an image on the projection surface 13 by the light modulated by the image display panel 8. Further, a circuit for generating data of a plurality of subframe images from the data of each frame constituting the image, and displaying the plurality of subframe images by time division by the image display panel, and selecting the selected subframe image. An image shift element 11 for shifting on the projection surface is provided, and the same region on the projection surface 13 is sequentially irradiated with light belonging to different wavelength ranges modulated in different pixel regions of the image display panel 8. Thereby, a projection image display apparatus suitable for realizing a bright and high resolution uniform display and miniaturization and cost reduction is provided.
公开号:KR20030010731A
申请号:KR1020027017165
申请日:2001-06-13
公开日:2003-02-05
发明作者:가토흐히로미；나카니시히로시；하마다히로시；진다아키히토；카와무라타다시；시바타니타카시
申请人:샤프 가부시키가이샤；
IPC主号:

专利说明:

Projection type image display device {PROJECTION TYPE IMAGE DISPLAY DEVICE}
[2] A conventional projection image display apparatus using a liquid crystal display panel will be described.
[3] Such a projection image display device does not emit light, and therefore, it is necessary to provide a light source separately. However, compared with a projection image display device using a CRT, the projection image display device has a wider color reproduction range, and is compact, lightweight, and convergence. It has very good features such as no adjustment.
[4] Performing full color display by a projection type image display apparatus using a liquid crystal display panel includes a three-plate type using three liquid crystal display panels according to three primary colors, and a single-plate type using only one sheet.
[5] In a three-plate projection image display apparatus, an optical system for dividing white light into three primary colors of red (R), green (G), and blue (B), and modulating light of R, G, and B colors, respectively, Using three liquid crystal display panels for forming an image, full color display is realized by optically superimposing respective images of R, G, and B colors.
[6] In the three-panel projection type image display apparatus, the light emitted from a white light source can be effectively used, but since the optical system is complicated and the number of parts is increased, in general, the projection type image display of a single plate type in view of cost and size It is more disadvantageous than the device.
[7] The single-panel projection image display apparatus uses a single liquid crystal display panel provided with color filters of three primary colors arranged in a mosaic or stripe form. Then, the full color image displayed by the liquid crystal display panel is projected onto a projection surface such as a screen by a projection optical system. Such a single-plate projection image display apparatus is described, for example, in Japanese Patent Application Laid-Open No. 84-230383. In the case of the single plate type, since one liquid crystal display panel is used, the optical system is also simpler than the case of the three plate type, and is suitable for providing a small projection image display device at low cost.
[8] However, in the case of the single plate type using the color filter, light absorption in the color filter occurs, so that the brightness of the image is reduced to about 1/3 compared with the case of the three plate type using the equivalent light source. In addition, since three pixel areas corresponding to R, G, and B of the liquid crystal display panel become one set, and display of one pixel is required, the resolution of the image is also reduced to 1/3 of the resolution of the three-plate type.
[9] Although brightening the light source is one solution to the decrease in brightness, it is not preferable to use a light source with a large power consumption when using it for public use. In addition, in the case of using an absorption type color filter, the energy of light absorbed by the color filter is changed to heat. Therefore, lightening the light source unnecessarily not only causes the temperature rise of the liquid crystal display panel but also accelerates the fading of the color filter. Therefore, how to effectively use a given light is an important problem in improving the usable value of the projection image display apparatus.
[10] In order to improve the brightness of an image by a single-panel projection type image display device, a liquid crystal display device that performs full color display without a color filter has been developed (Japanese Patent Laid-Open No. 92-60538). In this liquid crystal display device, white light emitted from a light source is divided into light beams of R, G, and B by a dielectric mirror such as a dichroic mirror, and at different angles to the microlens array arranged on the light source side of the liquid crystal display panel. Let it enter. Each light beam incident on the microlens is focused on the pixel region corresponding to the incident angle by transmitting the microlens. For this reason, the separated luminous fluxes of R, G, and B are modulated in individual pixel areas and used for full color display.
[11] Instead of using the dielectric mirror, a display device which improves light utilization by using a hologram element of transmission type corresponding to R, G, and B light is disclosed in Japanese Patent Laid-Open No. 93-249318. Japanese Patent Application Laid-Open No. 94-222361 discloses a device in which a corresponding periodic structure is provided in a transmissive hologram element, and a function of a dielectric mirror and a microlens is provided.
[12] Regarding the resolution which is another problem of the single plate type, by adopting the field sequential method, the resolution equivalent to the three plate type can be obtained by one liquid crystal display panel. In the field sequential method, a phenomenon in which the color of each time-divided image is constituted by additive mixed color is used by switching the color of the light source at a speed that cannot be resolved by human vision (continuous additive color).
[13] A projection image display device that performs full color display by the field sequential method has the configuration shown in FIG. 76, for example. In this display device, a disk composed of R, G, and B color filters is rotated at high speed in accordance with the vertical scanning period of the liquid crystal display panel, and image signals corresponding to the color of the color filter are sequentially input to the driving circuit of the liquid crystal display panel. do. In the human eye, a composite image of an image for each color is recognized.
[14] According to such a field-sequential display device, unlike the single-plate method, since the R, G, and B images are displayed by time division in each pixel of the liquid crystal display panel, the resolution is equivalent to that of the three-plate type.
[15] As another display device of the field sequential method, a projection image display device for irradiating different areas of the liquid crystal display panel at the luminous fluxes of R, G, and B is disclosed in IDW'99 (P989 to P992). In this display device, white light emitted from a light source is separated into light beams of R, G, and B by a dielectric mirror, and different regions of the liquid crystal display panel are irradiated with light beams of R, G, and B. FIG. The light irradiation positions of R, G, and B with respect to the liquid crystal display panel are sequentially switched by rotating the prism in the form of a cube.
[16] In addition, in the projection type image display apparatus described in JP-A-97-214997, the same method is used by using the same liquid crystal display apparatus as that described in JP-A-92-60538. Thus, white light is divided into luminous flux for each color, and each luminous flux is incident on the pixel region at different angles. In this projection type image display apparatus, in order to achieve both high light utilization efficiency and high resolution, each frame image is time-divided into a plurality of subframe images, and the incident angle of the light beam is synchronized with the vertical scanning period of the liquid crystal display panel. Is switching periodically.
[17] However, according to the apparatuses described in Japanese Patent Application Laid-Open No. 92-60538, Japanese Patent Application Laid-Open No. 93-249318, Japanese Patent Application Laid-Open No. 94-222361 and the like, the brightness is certainly improved, but the resolution is 3 1/3 of the plate is the same. This is because three pixels for R, G, and B, which are spatially separated, are used as a set even when displaying one pixel (dot).
[18] In contrast, in the case of the normal field sequential method, the resolution is improved to the same level as the resolution of the three-plate type. However, the brightness of an image has the same problem as that of the conventional single plate type.
[19] On the other hand, in the display device described in IDW'99, it is necessary to prevent the light irradiation positions of R, G, and B from overlapping each other, but for this purpose, illumination light with excellent parallelism is required. Therefore, the utilization efficiency of light falls by regulation of the parallelism degree of illumination light.
[20] As mentioned above, in the above-mentioned prior art, in order to improve both the brightness and the resolution which are the subject of a single plate type, all are not realized.
[21] The present applicant has disclosed in Japanese Laid-Open Patent Publication No. 97-214997 which intends to solve the above problems. According to the display device disclosed in Japanese Patent Application Laid-Open No. 97-214997, it is necessary to sequentially switch the angle of incidence of the light beam to the liquid crystal panel in synchronization with the vertical scanning actuator of the liquid crystal panel. In this apparatus, it is necessary to secure a special space between the liquid crystal display panel and the light source to drive two sets of hologram elements or mirrors in order to perform such a switching.
[22] In such a display device, a plurality of movable parts are required to switch the incident light angle, which makes the control complicated. In addition, since each pixel of the liquid crystal display panel sequentially displays all colors, color-specific adjustment cannot be performed in the liquid crystal display panel.
[23] This invention is made | formed in view of the said situation, The main objective is to provide a projection type image display apparatus suitable for realizing a bright and high resolution uniform display, and miniaturization and cost reduction.
[1] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display apparatus, and more particularly, to a single-panel projection type image display apparatus that can perform color display using one image display panel without using a color filter. The present invention can be suitably used for compact projection type color liquid crystal television systems and information display systems.
[76] 1 is a schematic diagram of a projection image display apparatus of the present invention.
[77] 2 is a schematic cross-sectional view of a liquid crystal display panel.
[78] 3 is a spectroscopic characteristic of the dichroic mirror.
[79] 4 is a diagram for explaining a method for generating a color-coded image frame from an original image frame.
[80] 5 is a diagram for explaining the difference in principle between the conventional color display and the color display of the present invention.
[81] FIG. 6 is a diagram for explaining a method of generating three subframe data from data of a color-coded image frame.
[82] Fig. 7 is a diagram showing an aspect of shift (image shift) of a subframe image.
[83] 8 is a diagram showing the composition of a plurality of subframe images.
[84] 9 is a front view of a rotating plate constituting the image shift element.
[85] 10 is a sectional view of a rotating plate constituting the image shift element.
[86] 11 is a graph showing the response curve of the liquid crystal display panel.
[87] 12 is a diagram showing another aspect of the shift of a subframe image.
[88] FIG. 13 is a front view of an improvement example of a rotating plate constituting the image shift element of FIG.
[89] 14 is a sectional view of a reflective liquid crystal display panel.
[90] Fig. 15 is a diagram showing another embodiment of the image shift.
[91] Fig. 16 is a front view of another rotating plate constituting the image shift element.
[92] 17 is a front view of another rotating plate constituting the image shift element.
[93] 18 is a diagram showing another aspect of the image shift.
[94] Fig. 19 is a diagram showing another embodiment of the image shift.
[95] 20 is a diagram showing another aspect of the image shift.
[96] Fig. 21 is a diagram showing another embodiment of the image shift.
[97] Fig. 22 is a front view of still another rotating plate constituting the image shift element.
[98] Fig. 23 is a partial front view of an image display panel showing a state in which subframe images are switched by line scanning.
[99] 24 is a front view of still another rotating plate constituting the image shift element.
[100] 25 is a front view of still another rotating plate constituting the image shift element.
[101] Fig. 26 is a diagram showing that the switching of subframe images and the timing of the image shift are shifted in accordance with the position of the image.
[102] Fig. 27 is a front view of the transparent plate constituting the image shift element.
[103] FIG. 28 is a diagram showing a method of driving the transparent plate of FIG.
[104] 29 is a cross-sectional view of the image shift element.
[105] 30 is a diagram showing the operation of the image shift element.
[106] Fig. 31 is a front view of the image shift element.
[107] 32 is a perspective view of an image shift element.
[108] 33 is a perspective view of the image shift element.
[109] 34 is a perspective view of the image shift element.
[110] 35 is a perspective view of the image shift element.
[111] 36 is a sectional view of an image shift element.
[112] Fig. 37 is a block diagram showing a system configuration example of a projection image display apparatus according to the present invention.
[113] FIG. 38 is a diagram schematically showing a circuit arrangement for generating a subframe image. FIG.
[114] 39 is a timing chart showing a procedure for generating a subframe image.
[115] 40 is a configuration diagram showing an embodiment of a projection type image display apparatus using two image display panels.
[116] Fig. 41A is a diagram showing an image shift when there is no observer's eye shift, and Fig. 41B is a diagram showing an image shift when the observer's eye movement is shifted, and Fig. 41C is a shift of the eye line. It is a figure which shows the state of the image shift seen from the observer to make.
[117] 42A to 42C are graphs showing local points of a frequency spectrum obtained by Fourier transforming a pixel array (shift pattern) in a y-t space.
[118] Fig. 43 is a diagram showing six kinds of subsets 1A to 3A and 1B to 3B that can constitute a shift pattern of a subframe image.
[119] FIG. 44 is a diagram showing a shift pattern of a subframe image having one period by six subframe images (subset 1A and subset 2B).
[120] FIG. 45 is a diagram showing a rotating plate constituting the image shift element capable of realizing the shift pattern of FIG.
[121] 46 is a diagram showing an example of the pixel arrangement of the image display panel employed in the embodiment of the present invention.
[122] Fig. 47 is a diagram showing another example of the pixel arrangement of the image display panel.
[123] FIG. 48A is a graph showing local points of the frequency spectrum in the Fourier space of the pixel array in FIG. 46, and FIG. 48B is a graph showing local points of the frequency spectrum in the Fourier space of the pixel array in FIG. to be.
[124] FIG. 49 is a diagram showing a shift pattern of a subframe image in which one period is composed of 18 subframe images (six subsets).
[125] 50 is a diagram showing a rotating plate constituting the image shift element capable of realizing the shift pattern of FIG.
[126] Fig. 51 is a graph showing the response curve of the liquid crystal layer used for the image shift element.
[127] Fig. 52 is a diagram showing a phenomenon that occurs excessively when image shift is performed by arranging two sets of image shift elements in series on an optical path.
[128] Fig. 53 is a perspective view showing a configuration example of an image shift element.
[129] 54 is a perspective view showing another configuration example of the image shift element.
[130] FIG. 55 is a diagram showing the state change of the image shift element in FIG.
[131] 56 is a diagram showing the state change of the image shift element in FIG.
[132] FIG. 57 is a diagram showing the state change of the image shift element in FIG. 54; FIG.
[133] FIG. 58 is a diagram showing the state change in the image shift element of FIG.
[134] FIG. 59 is a diagram showing the polarization direction in the image shift element of FIG.
[135] Fig. 60 is a diagram showing a subframe image shift pattern in which one cycle is composed of six subframe images (two subsets) and the pixel shift amount is changed.
[136] Fig. 61 is a diagram showing a subframe image shift pattern in which one cycle is composed of six subframe images (two subsets) and the pixel shift amount is constant.
[137] Fig. 62 is a diagram showing a shift pattern of a subframe image in which one cycle is composed of six subframe images (two subsets).
[138] Fig. 63 is a front view of the rotating plate constituting the image shift element.
[139] 64 is a diagram showing a subframe image shift pattern in which one cycle is composed of 12 subframe images (four subsets) and the image shift amount is constant.
[140] FIG. 65 is a diagram showing the state change in the image shift element in which the image shift element in FIG. 54 is further improved.
[141] FIG. 66 is a diagram showing the state change in the image shift element in which the image shift element in FIG. 54 is further improved.
[142] FIG. 67 is a view showing the state change in the image shift element in which the image shift element in FIG. 54 is further improved.
[143] FIG. 68 is a view showing the state change in the image shift element in which the image shift element in FIG. 54 is further improved.
[144] Fig. 69 is a block diagram showing another example of the system configuration of a projection image display apparatus according to the present invention.
[145] 70 is a front view showing the relationship between the color separation direction and the screen.
[146] Fig. 71 is a diagram showing the polarizing plate in parallel Nicols arrangement and the liquid crystal sandwiched between the polarizing plates.
[147] FIG. 72 is a graph showing the voltage transmittance characteristics in the configuration shown in FIG.
[148] Fig. 73 is a graph showing that the voltage transmittance characteristic changes depending on the liquid crystal temperature.
[149] 74 is a graph showing that the voltage transmission characteristic changes depending on the wavelength of light.
[150] 75A is a perspective view schematically showing the configuration of an image shift for shifting an image in a direction different from the polarization direction of incident light, and FIG. 75B is a side view thereof. Fig. 75C is a view of the display panel and the elements constituting the image shift element viewed in a direction perpendicular to the optical axis.
[151] Fig. 76 is a diagram showing a conventional field sequential projection type image display apparatus.
[24] A projection image display apparatus according to the present invention includes a light source, an image display panel having a plurality of pixel regions each of which can modulate light, and a corresponding pixel among the plurality of pixel regions according to a wavelength range of light from the light source. A projection type image display apparatus having a light control means for condensing an area and an optical system for forming an image on a projection surface by light modulated by the image display panel, comprising: from the data of each frame image constituting the image; A circuit for generating data of a plurality of subframe images and time-divisionally displaying the plurality of subframe images by the image display panel; and a selected subframe image among the plurality of subframe images displayed by the image display panel. An image shift element for shifting the shift on the projected surface, and changing the shift in different pixel areas of the image display panel. The sequentially irradiated with the same area on the projection plane P by the light belonging to a different wavelength range.
[25] In a preferred embodiment, the direction in which the subframe image constituting the n + 1th frame (n is a positive integer) on the projected surface is shifted in the nth frame image. It is the same as the direction of shifting the subframe image constituting the above on the projection surface.
[26] In a preferred embodiment, the direction in which the subframe image constituting the n + 1th frame (n is a positive integer) on the projected surface is shifted in the nth frame image. The first subframe image of the n + 1th frame image is not shifted with respect to the last subframe image of the nth frame image in a direction opposite to the direction of shifting the subframe image constituting the subframe image on the projected surface. Do not.
[27] In some preferred embodiments, the number of subframe images constituting each frame image is two, and each subframe image is sequentially displayed at two different positions on the projected surface.
[28] In some preferred embodiments, the number of subframe images constituting each frame image is two, each subframe image is sequentially displayed at three different positions on the projected surface, and the period of shift of the subframe image is a frame. 1.5 times the period.
[29] In some preferred embodiments, the number of subframe images constituting each frame image is four or more, and each subframe image is sequentially displayed at three different positions on the projected surface, and the four constituting each frame image. At least two subframe images of the above subframe images are displayed at the same position on the projected surface.
[30] In some preferred embodiments, the at least two subframe images displayed at the same position on the projected surface comprise subframe images of black display.
[31] In a preferred embodiment, the at least two subframe images displayed at the same position on the projected surface include subframe images with reduced luminance.
[32] In some preferred embodiments, the movement pattern pattern of the subframe shifted on the projected surface has a periodicity, and one cycle of the movement pattern includes movement of about two pixel pitches at least twice.
[33] In a preferred embodiment, one period of the motion pattern of the subframe consists of a combination of a plurality of subsets selected from six kinds of subsets defined by the movement of three subframes, each of which is sequentially displayed. The six kinds of subsets belong to any of the two groups symmetrical with respect to the direction of movement.
[34] In some preferred embodiments, one period of the motion pattern of the subframe alternately includes a subset selected from each of the two groups.
[35] In a preferred embodiment, one period of the motion pattern of the subframe consists of 18 subframes that are sequentially displayed, and alternately includes six subsets selected from each of the two groups. .
[36] In a preferred embodiment, one period of the motion pattern of the subframe consists of movement of six subframes displayed sequentially, and includes two subsets selected one from each of the two groups. .
[37] In a preferred embodiment, the motion pattern of the subframe image shifted on the projected surface has a periodicity, and the motion pattern shifts the subframe image to four or more different positions on the same straight line. It includes.
[38] In some preferred embodiments, the shift amount between successive subframe images is not more than about twice the pixel pitch measured along the direction of the shift on the projected surface.
[39] In a preferred embodiment, one period of the motion pattern of the subframe image is composed of 12 subframe images that are sequentially displayed, and the amount of shift between successive subframe images that is continuously displayed is on the projected surface. In this case, the pixel pitch is not more than about twice the pixel pitch measured along the shift direction.
[40] In a preferred embodiment, one period of the motion pattern of the subframe image is composed of six subframe images that are sequentially displayed, and the amount of shift between successive subframe images that is continuously displayed is on the projected surface. In this case, the pixel pitch is not more than about twice the pixel pitch measured along the shift direction.
[41] It is preferable that the shift amount of the subframe on the projection surface is about an integer multiple of the pixel pitch measured along the direction of the shift on the projection surface.
[42] In some preferred embodiments, when the subframe image displayed by the image display panel is switched to the next subframe, the light is blocked so that the light modulated by the image display panel does not reach the projected surface. .
[43] In a preferred embodiment, the light control means directs the light from the light source in different directions included in the same plane according to the wavelength band, and the image shift element is arranged in the direction parallel to the plane. Shift the frame image.
[44] In a preferred embodiment, the shift direction of the subframe image by the image shift element coincides with the short side direction of the display screen in the image display panel.
[45] An image display apparatus according to the present invention is an image display apparatus having an image display panel each having a plurality of pixel areas capable of modulating light, and forming an image by the light modulated by the image display panel. A circuit for generating data of a plurality of subframe images from the frame image constituting the image, and displaying the plurality of subframe images by time division by the image display panel, and the plurality of displayed by the image display panel An image shift element for shifting the optical path of the selected subframe image among the subframe images of , And combining light belonging to different wavelength ranges modulated by different pixel regions of the image display panel by shifting the subframe; The circuit may include a first storage area for storing data relating to a first color constituting the frame image; A second storage area for storing data relating to a second color constituting a frame image, and a third storage area for storing data relating to a third color constituting the frame image, wherein the first storage area is provided with: a first memory area; By selectively combining data read out from each of the second storage area and the third storage area in a preset order, data of each of the plurality of subframes is generated.
[46] An image display apparatus according to the present invention is an image display apparatus having an image display panel each having a plurality of pixel areas capable of modulating light, and forming an image by the light modulated by the image display panel. A circuit for generating data of a plurality of subframe images from the frame image constituting the image, and displaying the plurality of subframe images by time division by the image display panel, and the plurality of displayed by the image display panel An image shift element for shifting the optical path of the selected subframe image among the subframe images, and combining light belonging to different wavelength ranges modulated by different pixel regions of the image display panel by shifting the subframe; And the circuit comprises a plurality of storage areas for storing data of the plurality of subframe images. In the plurality of storage areas, data relating to a first color constituting the frame image, data relating to a second color constituting the frame image, and data relating to a third color constituting the frame image are configured. The data to be stored is stored.
[47] In the image display device according to the present invention, a pixel region for a first color belonging to a first wavelength region, a pixel region for a second color belonging to a second wavelength region, and a pixel region for a third color belonging to a third wavelength region are periodically arranged. An image display apparatus comprising an image display panel having an optical modulator, further comprising an image shift element capable of periodically shifting an optical path of light modulated by the optical modulator, on an imaginary plane that traverses the optical path. The color of the first pixel of is light modulated in the first color pixel region in a first period, light modulated in the second color pixel region in a second period, and in the third color pixel region in a third period. The color of the second pixel defined by the modulated light and adjacent to the first pixel on the virtual plane is light modulated in the pixel region for the second color in the first period, and the color in the second period. In the pixel area for three colors The color of the third pixel which is defined by the modulated light and the light modulated in the pixel region for the first color in the third period, and adjacent to the second pixel on the virtual plane is determined in the first period. The light modulated in the third color pixel region, the light modulated in the first color pixel region in the second period, and the light modulated in the second color pixel region in the third period.
[48] A circuit device according to the present invention includes a first storage area for storing data relating to a first color constituting a frame image displayed by an image display apparatus having an image display panel, and a second color constituting the frame image. A circuit device having a second memory area for storing data and a third memory area for storing data relating to a third color constituting the frame image, wherein the first memory area, the second memory area, and the third memory area are provided. By combining the data read out from each of the storage areas in a predetermined order, each data of a plurality of subframes to be time-divided and displayed is generated.
[49] In a preferred embodiment, the data relating to the first color, the data relating to the second color, and the data relating to the third color for a certain pixel constituting the image are included in each of the plurality of subframe images. Assign.
[50] In a preferred embodiment, by shifting a selected subframe image of the plurality of subframe images on a certain surface, the same region on the surface is sequentially sequential by light belonging to different wavelength ranges modulated in different pixel regions of the image display panel. Can be investigated.
[51] The circuit device according to the present invention comprises data relating to a first color constituting a frame image displayed by an image display apparatus having an image display panel, data relating to a second color constituting the frame image, and the frame image. A circuit device having a plurality of storage areas for storing a plurality of subframes composed of data relating to a third color to be configured, wherein the data relating to the first color, the data relating to a second color, and the third color Data is written to the plurality of storage areas in a predetermined order, and the data of each storage area is sequentially read, thereby generating respective data of a plurality of subframe images to be time-divisionally displayed.
[52] The image shift element according to the present invention periodically shifts an optical path of a subframe image modulated by an image display panel, thereby causing the subframe image to be separated by one pixel pitch or more on the same straight line in a certain plane. An image shift element which can be selectively changed to at least one position, comprising: a refraction member for shifting the optical path by refraction; and a driving device for periodically changing a relative positional relationship of the refraction member with respect to the optical path. The refraction member is composed of a plurality of regions in which the shift amount of the optical path is different.
[53] In a preferred embodiment, the refractive member is composed of a rotating plate having a plurality of transparent regions having at least one of a refractive index and a thickness different from each other, and is rotatably supported by an arrangement in which the optical path is inclined and traversed. The apparatus rotates the rotating plate such that a plurality of transparent regions of the rotating plate sequentially cross the optical path.
[54] In a preferred embodiment, the refractive member is composed of a transparent plate having a plurality of transparent regions having at least one of a refractive index and a thickness different from each other, and is supported by a disposition traversing the optical path so as to be movable. The driving device moves the transparent plate so that a plurality of transparent regions of the transparent plate sequentially cross the optical path.
[55] The image shift element according to the present invention periodically shifts an optical path of a subframe image modulated by an image display panel, thereby causing the subframe image to be separated by one pixel pitch or more on the same straight line in a certain plane. An image shift element that can be selectively switched to more than one position, the image shift element having a first element for modulating the polarization direction of the subframe image modulated by the image display panel, and a second element having a different refractive index in accordance with the polarization direction of the light; And a light incident side having at least two sets of the first element and the second element, arranged to be arranged in series on the optical path, and shifting the subframe image to an adjacent position among the three or more positions. The selection of the voltage application state for the first element disposed in the device is different depending on the direction in which the subframe image is then shifted. It characterized.
[56] The image shift element according to the present invention periodically shifts an optical path of a subframe image modulated by an image display panel, thereby causing the subframe image to be separated by one pixel pitch or more on the same straight line in a certain plane. An image shift element that can be selectively switched to more than one position, the image shift element having a first element for modulating the polarization direction of a subframe image modulated by the image display panel, and a second element having an index of refraction or higher according to the polarization direction of light; And a light incident side having at least two sets of the first element and the second element, arranged to be arranged in series on the optical path, and shifting the subframe image to the center of the three or more positions. To make the state of applying the voltage to the first element arranged in the same as the state of applying the voltage to the first element arranged on the light exit side. Gong.
[57] The image shift element according to the present invention periodically shifts an optical path of a subframe image modulated by an image display panel, thereby causing the subframe image to be separated by one pixel pitch or more on the same straight line in a certain plane. An image shift element that can be selectively switched to at least one position, the image shift element comprising a first image shift portion and a second image shift portion disposed on the optical path, wherein the first and second image shift portions are respectively the image. A first element for modulating the polarization direction of the subframe image modulated by the display panel, a second element having a different refractive index according to the polarization direction of light, and a shift amount of the subframe image by the first image shift element, The shift amounts of the subframe images by the second image shift element are different from each other.
[58] In a preferred embodiment, the shift amount of the subframe image by the image shift portion located on the side where light first enters on the optical path is shifted to the image shift portion located on the side where light subsequently enters on the optical path. This is twice the shift amount of the subframe image.
[59] In some preferred embodiments, the combination of applied voltages driving the plurality of elements does not include a transition from ON to OFF and a transition from OFF to ON at the same time.
[60] The image shift element according to the present invention periodically shifts an optical path of a subframe image modulated by an image display panel, whereby the plurality of subframe images are separated by at least one pixel pitch on the same straight line in a plane. An image shift element that can be selectively changed to the position of , And has a first element for modulating the polarization direction of the subframe image modulated by the image display panel, and a second element having a different refractive index depending on the polarization direction of light, The first element includes a liquid crystal element capable of switching the polarization state of light in response to application of a voltage, and the second element includes an optical birefringence element for shifting the optical axis position in accordance with the polarization state of light. In order to switch the polarization state of light, the voltage of the several level applied to the said liquid crystal element has a non-zero value all.
[61] In a preferred embodiment, the liquid crystal element emits a first polarization when a first voltage included in the voltages of the plurality of levels is applied, and when a second voltage included in the voltages of the plurality of levels is applied, The second polarized light in which the polarization plane is substantially rotated by 90 ° with respect to the first polarized light is emitted.
[62] In a preferred embodiment, the first voltage has an offset value controlled according to the temperature of the liquid crystal element.
[63] The first voltage has an offset value set based on the voltage transmittance characteristic of visible light passing through the liquid crystal element.
[64] In a preferred embodiment, the first voltage has an offset value set based on the voltage transmittance characteristic of the green light passing through the liquid crystal element.
[65] In a preferred embodiment, the first voltage has an offset value optimized based on the voltage transmittance characteristic of red light passing through the liquid crystal element, the voltage transmittance characteristic of green light, and the voltage transmittance characteristic of blue light.
[66] The image shift element according to the present invention periodically shifts an optical path of a subframe image modulated by an image display panel, whereby the plurality of subframe images are separated by at least one pixel pitch on the same straight line in a plane. An image shift element that can be selectively changed to the position of , And has a first element for modulating the polarization direction of the subframe image modulated by the image display panel, and a second element having a different refractive index depending on the polarization direction of light, The first element has a first polarization modulator and a second polarization modulator, and the second element has a first birefringent element and a second birefringent element, and the first polarization modulator is the first polarization modulator. Emitting normal or abnormal light to one birefringent element, and the second polarization modulator emits normal or abnormal light to the second birefringent element, and The refractive element shifts the image by a distance a in a direction of θ ° with respect to a certain reference plane including the optical path, and the second birefringent element shifts the image by a distance b in a direction of θ '° with respect to the reference plane. Shift and tan = A / b.
[67] In some preferred embodiments, the relationship of θ '= θ + 90 ° is established.
[68] In some preferred embodiments, the relationship of θ '= θ holds.
[69] In some preferred embodiments, the θ is 45 °.
[70] The image shift element according to the present invention periodically shifts an optical path of a subframe image modulated by an image display panel, thereby causing the subframe image to be separated by one pixel pitch or more on the same straight line in a certain plane. An image shift element that can be selectively switched to at least one position, and having a liquid crystal layer exhibiting two or more different refractive indices with respect to polarized light, and two substrates sandwiching the liquid crystal layer, wherein any one of the two substrates is provided. A microprism or a diffraction grating is formed on the surface of the liquid crystal side.
[71] In some preferred embodiments, the microprism or diffraction grating is formed of a material having a refractive index substantially equal to the refractive index of at least one of the two or more refractive indices.
[72] In a preferred embodiment, the liquid crystal layer and the two substrates have at least two sets, the groups are arranged in series on the optical path, and the subframe image is shifted to an adjacent position among the three or more positions. In this case, the subframe image is shifted only by selecting the voltage applied to the image shift element arranged on the light output side.
[73] An image shift element according to the present invention comprises at least two sets of image shift elements arranged in series on an optical path, each set of image shift elements each including two displacement elements, and each displacement element is polarized light. It has a liquid crystal layer which shows two or more different refractive index with respect to light, and two board | substrates which hold | maintain the said liquid crystal layer, The microprism or a diffraction grating is formed in the liquid crystal side surface of any one board | substrate of the said two board | substrates, The refractive angles of the microprisms or diffraction gratings formed on the substrate included in the same tank are the same, and the refractive angles of the microprisms or diffraction gratings formed on the substrate included in the tank positioned on the side where light first enters on the optical path are the same. 2 times the angle of refraction by the microprism or diffraction grating formed on the substrate of the jaw positioned on the side where light is later incident on the optical path The.
[74] An image shift element according to the present invention comprises at least two sets of image shift elements arranged in series on an optical path, each set of image shift elements each including two displacement elements, and each displacement element is polarized light. It has a liquid crystal layer which shows two or more different refractive index with respect to light, and two board | substrates which hold | maintain the said liquid crystal layer, The microprism or a diffraction grating is formed in the liquid crystal side surface of any one board | substrate of the said two board | substrates, The angles of refraction of the microprisms or diffraction gratings formed on the substrate included in the same bath are equal to each other, and the distance of the substrate included in the bath located on the side where light first enters on the optical path is located on the side where light subsequently enters on the optical path. It is twice the distance of the board | substrate of the group to make.
[75] The image shift element according to the present invention periodically shifts an optical path of a subframe image modulated by an image display panel, thereby causing the subframe image to be spaced at least one pixel pitch on the same straight line in a plane. An image shift element that can be selectively switched to two positions, the first shift element being arranged in series on the optical path and the second shift element, wherein the shift amount of the subframe image by the first shift element is It is set to twice the shift amount of the subframe image by the first shift element.
[152] In the present invention, for example, in a single-panel projection type image display apparatus that does not use a color filter, a plurality of subframe image data are generated from data of each frame image constituting the image, and a plurality of subframe image data are generated by the image display panel. The subframe image is displayed in time division. By sequentially shifting these subframe images on the projected surface, the same region on the projected surface is sequentially irradiated by light (R, G, B light) belonging to different wavelength ranges modulated in different pixel regions of the image display panel. This achieves high resolution full color display.
[153] In the case of the present invention, when a particular area corresponding to one pixel on the projected surface is noticed, in a display period of a subframe (hereinafter referred to as a "subframe period"), the specific area thereof is, for example, red light (R light). Is irradiated with green light (G light) in the next subframe period, and is irradiated with blue light (B light) in the next subframe period. Thus, according to this invention, the color of each pixel on a to-be-projected surface is prescribed | regulated by time division irradiation of R, G, and B light.
[154] There is a remarkable difference between the projection color image display device using the conventional field sequential method and the present invention as described below.
[155] In the case of the conventional field sequential method, the image display panel is irradiated alternately by R, G, and B light. Therefore, in any one subfield period, all the pixel areas of the image display panel are irradiated by any one of the R, G, and B light. As a result, each subframe image on the projection surface is constituted by pixels composed of one color of R, G, and B light, but the subframe for R image, the subframe for G image, and the subframe for B image are human. Since the time-division display is carried out in short time units of less than or equal to the time resolution of the visual time, a color image is recognized by the human eye.
[156] In contrast, each of the subframe images used in the present invention is constituted by a combination of R, G, and B lights as described later. That is, in one subframe period, the projection surface is irradiated with the R, G, and B light modulated by the image display panel. The R, G, and B light modulated by the image display panel respectively irradiate different positions of the projected surface for each subframe period, and are synthesized in time to display a full color frame image.
[157] In the present invention, the temporal suitability of such R, G, and B light is performed by the image shift element. The image shift element is disposed between the image display panel and the projection surface, and periodically changes the path (optical path) of light modulated by the image display panel.
[158] The scope of application of the present invention is not limited to a projection type image display apparatus, but is also suitably applied to a direct view type image display apparatus such as a viewer, a head mount display, or the like. In the following, a projection image display apparatus is used as an example. The preferred embodiment of the present invention will be described.
[159] First, the apparatus configuration according to the first embodiment will be described with reference to FIG.
[160] (Example 1)
[161] In the projection image display device of this embodiment, light control for condensing light from the light source 1, the liquid crystal display panel 8, and the light source 1 to the corresponding pixel region of the liquid crystal display panel 8 according to the wavelength range. Means and a projection optical system for projecting the light modulated by the liquid crystal display panel 8 onto the projection surface.
[162] This projection type image display apparatus further includes a spherical mirror 2 reflecting forward light (white light) emitted from the light source 1 forward, and a condenser lens whose light from the light source 1 and the spherical mirror 2 is a parallel light flux. (3) and dichroic mirrors 4 to 6 that separate the light beams into a plurality of light beams in accordance with the wavelength range. Light reflected by the dichroic mirrors 4 to 6 is incident on the microlens array 7 at different angles depending on the wavelength range. The microlens array 7 is mounted on the light source side substrate of the liquid crystal display panel 8, and light incident on the microlens 7 at different angles is focused on corresponding pixel regions at different positions, respectively.
[163] The projection optical system of the present projection image display device is composed of a field lens 9 and a projection lens 11, and the light beam 12 transmitted through the liquid crystal display panel 8 is transferred to the screen (projected surface) 13. Project. In this embodiment, the image shift element 10 is disposed between the field lens 9 and the projection lens 11. In Fig. 1, the light beams 12a and 12b shifted in the direction parallel to the projection surface by the image shift element 10 are shown. In order to shift the light beam, the image shift element 10 may be inserted at any position between the liquid crystal display panel 8 and the screen 13, and is disposed between the projection lens 11 and the screen 13. You may be.
[164] Next, each component of the present projection image display apparatus will be described in sequence.
[165] In this embodiment, as the light source 1, a metal halide lamp having a light output of 150 W, an arc length of 5 mm, and an arc diameter of 2.2 mm is used, and the lamps are arranged so that the arc length direction is parallel to the surface of the drawing. have. As the light source 1, in addition to the metal halide lamp, a halogen lamp, an ultrahigh pressure mercury lamp, a xenon lamp, or the like may be used. The light source 1 used in the present embodiment emits white light including light of three wavelength bands corresponding to three primary colors.
[166] A spherical mirror 2 is disposed on the rear surface of the light source 1, and a condenser lens 3 having a diameter of 80 mm phi and a focal length of 60 mm is disposed on the front surface of the light source 1. The spherical mirror 2 is arranged so that its center coincides with the center of the light emitting part of the light source 1, and the condenser lens 3 is arranged so that its focus coincides with the center of the light source 1.
[167] With this arrangement, the light emitted from the light source 1 is parallelized by the condenser lens 3 to illuminate the liquid crystal display panel 8. The parallelism of the light passing through the condenser lens 3 is, for example, about 2.2 ° in the arc length direction (direction parallel to the surface of Fig. 1) and about 1 ° in the arc diameter direction.
[168] The liquid crystal display panel 8 used in this embodiment is a transmissive liquid crystal display element in which a microlens array 7 is arranged on a transparent substrate on the light source side. Although the kind and operation mode of a liquid crystal are arbitrary, it is preferable that it can operate at high speed. In this embodiment, it operates in TN (twisted nematic) mode. The liquid crystal display panel 8 is provided with a plurality of pixel areas for modulating light, and the term "pixel area" in the present specification means individual light modulators spatially separated in the image display panel. In the case of the liquid crystal display panel 8, a voltage is applied to a corresponding portion of the liquid crystal layer by pixel electrodes corresponding to individual pixel regions, and light modulation is performed by changing the optical characteristics of the portion.
[169] In this liquid crystal display panel 8, for example, a scanning line of 768 (H) x 1024 (V) is driven by non-interlace. The pixel areas of the liquid crystal display panel 8 are two-dimensionally arranged on the transparent substrate, and in this embodiment, the pitch of the pixel areas is 26 μm measured in the horizontal direction or measured in the vertical direction. . In the present embodiment, the pixel areas for R, G, and B are arranged in a stripe form along the horizontal direction of the screen, respectively, and each microlens has three pixel areas (for R, G, and B). Pixel area).
[170] As shown in FIG. 1, the R, G, and B lights irradiating the liquid crystal display panel 8 separate white light emitted from the light source 1 by dichroic mirrors 4, 5, and 6. Incident on the microlens array 7 on the liquid crystal display panel 8 at different angles. By appropriately setting the incidence angles of the R, G, and B light, as shown in Fig. 2, the microlenses 7 can be appropriately distributed in the pixel regions corresponding to the respective wavelength ranges. In this embodiment, the focal length of the microlens 7 is 255 µm, and the angle formed by each light beam is designed to be 5.8 °. More specifically, R light is incident perpendicularly to the liquid crystal display panel 8, and B light and G light are respectively incident at an angle of 5.8 ° with respect to the R light.
[171] The dichroic mirrors 4, 5, and 6 have spectral characteristics as shown in Fig. 3, and selectively reflect light of green (G), red (R), and blue (B), respectively. . The wavelength range of G light is 520-580 nm, the wavelength range of R light is 600-650 nm, and the wavelength range of B light is 420-480 nm.
[172] In the present embodiment, dichroic mirrors 4 to 6 and microlens arrays 7 are used to focus light of three primary colors into corresponding pixel regions, but other optical means (e.g., diffraction and spectroscopy of light) are used. Transmissive hologram).
[173] As described above, since the liquid crystal display panel 8 is driven by non-interlace, 60 frames of images are displayed between one second, and the time (frame period) T allocated to each frame is 1/60 seconds, that is, T = 1/60 (seconds) ≒ 16.6 (milliseconds).
[174] In the case of driving by interlace, the scan lines in the screen are divided into even lines and odd lines and displayed alternately, so that T = 1/30 (seconds) ≒ 33.3 (milliseconds). Further, the time (one field period) allocated to each of the even and odd fields constituting each frame is 1/60 6.6 16.6 (milliseconds).
[175] In this embodiment, the information (data) of each frame image constituting the image is sequentially stored in the frame memory, and a plurality of subframe images are sequentially formed based on the information selectively read out from the frame memory. Hereinafter, a method of forming a subframe image will be described in detail.
[176] For example, an image (frame image) of a certain frame is called an image as shown in Fig. 4A. This frame image should be displayed in color, and the color of each pixel is determined based on the data defining the frame image. In the case of interlaced driving, an image of a certain field can be treated similarly to a "frame image" in the present specification.
[177] In the case of the conventional three-panel projection image display device, the R, G, and B light data are separated from the data for each pixel, and as shown in Figs. 4B, 4C, and 4D, an R image frame is shown. , Data for each G picture frame and a B picture frame are generated. Using the three image display panels for R, G, and B, the R image frame, the G image frame, and the B image frame are respectively displayed at the same time and superimposed on the projected surface. Fig. 5A schematically shows how the R, G, and B image frames overlap with respect to a specific pixel on the projection surface 13.
[178] In contrast, in the conventional single-plate projection type image display apparatus, the pixel regions for R, G, and B are provided at separate positions in one display panel. Then, light is modulated in the R, G, and B pixel areas based on each of the R, G, and B data, thereby forming a color image on the projection surface. In this case, since R, G, and B light are irradiated in a region smaller than the spatial resolution of human vision on the projected surface, even though the R, G, and B light are spatially separated from each other, The eye is recognized as if one pixel is composed. FIG. 5B schematically shows the pattern of irradiation of R, G, and B light with respect to a specific pixel on the projection surface 13.
[179] Unlike the conventional method described above, in this embodiment, R, G, and B light modulated in different pixel areas of one image display panel 8 are sequentially irradiated to the same area on the projection surface 13, and the same area. One pixel is displayed on the screen. That is, when attention is paid to any pixel on the projection surface 13, display of the pixel is performed in a manner similar to that of the field sequential method. However, the R, G, and B light constituting one pixel are significantly different from the conventional field sequential method in that they are modulated in different pixel areas of one image display panel. Fig. 5C schematically shows how the R, G, and B lights irradiated with time division are synthesized over one frame period with respect to a specific pixel on the projection surface 13. The screen shown in the left part of FIG. 5C corresponds to three different subframe images in one image display panel 8. FIG.
[180] As is clear from Figs. 5A to 5C, according to this embodiment, full color display can be realized with the same high resolution and brightness as in the three-plate type, using only one display panel.
[181] Next, the configuration of the subframe image will be described in detail with reference to FIG.
[182] In the left part of Fig. 6, data of R, G, and B image frames stored in the R, G, and B frame memories are shown. In the right part of Fig. 6, display subframes 1 to 3 are shown. According to this embodiment, in the first third period (first subframe period) of a certain frame, the image of the display subframe 1 is displayed on the projected surface on the projected surface. Then, the image of the display subframe 2 is displayed in the next third period (second subframe period), and the display subframe 3 in the last third period (third subframe period). The image of is displayed. In this embodiment, these three subframe images are shifted as shown in Fig. 7, and synthesized while shifting in time, so that the human eye can recognize the original image as shown in Fig. 4A.
[183] Next, the data structure of the subframe image will be described in detail using the display subframe 1 as an example.
[184] First, the data for the first row pixel region of the display subframe 1 is formed of data relating to the first row pixel R1 stored in the R frame memory, as shown in FIG. The second row pixel area data of the display subframe 1 is formed of data relating to the second row pixel G2 stored in the G frame memory. The third row pixel area data of the display subframe 1 is formed of data relating to the third row pixel B3 stored in the B frame memory. The data for the fourth row pixel region of the display subframe 1 is formed of data relating to the fourth row pixel R4 stored in the R frame memory. Hereinafter, data of the display subframe 1 is configured in the same order.
[185] The data of the display subframes 2 and 3 is also configured in the same manner as in the case of the display subframe 1. For example, in the case of the display subframe 2, the data for the 0th row pixel region is formed of data relating to the first row pixel B1 stored in the frame memory for B, and the first row pixel region of the display subframe 2 is used. The application data is formed of data relating to the second row pixel R2 stored in the R frame memory. The second row pixel area data of the display subframe 2 is formed of data relating to the third row pixel G3 stored in the G frame memory, and the third row pixel area data of the display subframe 2 is B. It is formed of data relating to the fourth row pixel B4 stored in the frame memory.
[186] In this way, by combining the data read out from each of the R, G, and B frame memories in a preset order, data of each of the subframes displayed in time division display is generated. As a result, each of the subframe data includes information on all the colors of R, G, and B, but spatially one third of the entire area of each of R, G, and B. It only has information about. More specifically, in the case of the display subframe 1, the information of R is clear from the first, fourth, seventh, tenth,... It's only about the pixels in the row. The information of R for the pixels in the other rows of the frame image is allocated to the display subframes 2 and 3.
[187] In the present embodiment, information of the same color is always displayed in each pixel area of the image display panel, but frame images can be synthesized by shifting and projecting an image between each subframe. As can be seen from Fig. 6, the total number of rows of the pixel region of the image display panel is two more than the total number of rows of the pixels constituting one subframe image. These two rows serve as a margin of image shift.
[188] Next, referring to Figures 8 and 9, a description will be given of how the shifted plurality of subframe images synthesize one frame image.
[189] First, reference is made to FIG. Fig. 8A is a perspective view showing a part of three subframe images projected onto a projected surface such as a screen. The display subframes 1 to 3 and the synthesized frame images are schematically shown in order from the left in the figure. 8B shows corresponding pixel regions of the pixel display panel, and shows corresponding portions of the display subframes 1 to 3 in order from the left. The third to seventh rows of the display subframe 1, the second to sixth rows of the display subframe 2, and the first to the fifth rows of the display subframe 3 are spatially displaced and spaced apart on the projected surface. By superimposing, one frame image is formed.
[190] The positions of the pixel areas for R, G, and B on the image display panel are fixed as shown in Fig. 8B, but the optical path of the subframe image is caused by the operation of the image shift element disposed between the image display panel and the projection surface. Is shifted so that the synthesis of subframe images as shown in Fig. 8A is achieved.
[191] Next, the subframe image shift method will be described.
[192] In this embodiment, an image shift element made of a disk-shaped glass plate (refractive member) 20 having three transparent areas A to C as shown in Fig. 9 is employed. The disk-shaped glass plate 20 is formed of BK7 glass having a refractive index of 1.52, the thickness of the transparent region A is set to 0.7 mm, the thickness of the transparent region B is 1.1 mm, and the thickness of the transparent region C is set to 1.5 mm. This glass plate is supported by the state which can be rotated centering on the center of a disk, and is arrange | positioned so that the main surface of a glass plate may form an angle of 70.2 degrees between an optical axis. Fig. 10 shows a partial schematic view of the cross section of the glass plate across the optical axis. When the angle between the surface perpendicular to the optical axis and the main surface of the glass plate is θ ₀ , the glass thickness is d, and the refractive index of the glass is n _g , the shift amount Δx of the optical axis due to refraction is expressed by the following equation.
[193]
[194] In this embodiment, the glass thickness d is designed to have a different value in each of the transparent regions A to C, and the shift amount Δx of the optical axis changes periodically with the rotation of the glass plate 20.
[195] The light beam modulated by the image display panel passes through any of the transparent areas A to C of the glass plate 20 which is rotated by a driving device (motor or the like) not shown, and reaches the projection surface. In the case of this embodiment, the optical path of the light beam transmitted through the transparent area B is shifted by 26.1 μm with respect to the optical path of the light beam transmitted through the transparent area A. Similarly, with respect to the optical path of the light beam transmitted through the transparent region B, the optical path of the light beam transmitted through the transparent region C is shifted by 26.1 μm. The shift amount (= 26.1 μm) is a value converted as the shift amount on the image display panel, and the image shift element is designed to correspond to the vertical pitch of the pixel region. This shift amount can be changed to another arbitrary value by adjusting the thickness of each transparent region A-C. For example, when the thickness of each of the transparent areas A to C is 1.4 times, the shift amount is 26.1 x 1.4 µm.
[196] In this embodiment, the direction (shift direction) in which the shift X of the luminous flux occurs is the same as the vertical direction of the image. However, the shift direction of the luminous flux may be the same as the horizontal direction of the image or may be an inclined direction. An important point is that the shift amount has a size in pixels, and the pixels of each subframe image are substantially overlapped on the projected surface. In other words, the shift amount of the image on the projection surface may be about an integral multiple of the pixel pitch measured along the shift direction on the projection surface.
[197] When making the shift direction of the luminous flux equal to the horizontal direction of the image, for example, the glass plate of Fig. 10 may be rotated 90 degrees about the optical axis, so that the shift of the luminous flux is performed along the horizontal direction of the image.
[198] Fig. 11 shows a response curve of light transmittance with respect to voltage application in the portion (each pixel area) for modulating light in the image display panel 8. In this embodiment, each pixel region has a structure in which the liquid crystal layer is sandwiched between the electrodes, and the response speed of the liquid crystal is finite, so that the light transmittance does not reach the maximum value at the start of voltage application. That is, it is delayed from the start of voltage application that the light transmittance reaches the maximum level and the change from the dark state to the bright state is completed. In addition, a time delay also occurs from the stop point of voltage application until the light transmittance reaches a minimum value (zero).
[199] In this embodiment, as shown in Fig. 8B, it is necessary to display different subframe images on the image display panel for each subframe period. If the display of the subframe image requires a time that cannot be ignored, the brightness of the subframe image is insufficient in the first portion of each subframe period, and the subframe period (voltage application period) is over. Even after this, the subframe image is unnecessarily displayed for a while. Therefore, even if the subframe image is shifted, the image of the previous subframe may be displayed due to the delay in the response speed of the image display panel, or the image of the previous subframe may be displayed superimposed on the image of the next subframe. In such a case, bleeding or ghosting (double stamping) occurs in the outline or the like in the synthesized frame image.
[200] Referring to Fig. 12, the reason for the above bleeding or ghost will be explained. Fig. 12 shows a specific pixel string of a subframe image constituting the nth (n is a positive integer) frame image, and a subframe image constituting the n + 1th frame image. Corresponding pixel columns are shown schematically. Each pixel column is up and down because the optical path of the subframe image is shifted up and down by the image shift element. In Fig. 12, there is shown a pixel which is delayed in transition from the bright state to the dark state due to the delay of the response of the image display panel. For example, in the first subframe image constituting the nth frame image, the "B" pixel in the bright state is shifted downward by one pixel in the next subframe, but is still completely dark. It has not changed. In the next subframe, the image is shifted downward by one pixel and completely changed to a dark state. However, in this subframe, the "G" pixel above is slightly maintained. If such a response delay exists, color unevenness occurs in the pixel adjacent to the pixel ("W" pixel) of the white display of FIG. 12 and the pixel separated by one pixel.
[201] In order to prevent color bleeding and ghosting caused by the response delay of the image display panel, when the subframe image is switched in the image display panel, light modulated in the pixel region where the response delay occurs is projected. Do not project on the. For this purpose, only part of the light path (light path from the light source to the projection surface) is temporarily blocked using a light shielding device such as a liquid crystal shutter or a mechanical shutter only during a period in which a response delay occurs, or the light source is temporarily turned off. You may turn it off or off.
[202] The same problem occurs not only in the period in which the response of the image display panel is delayed, but also in the period in which the timing of the display timing and the image shift of the image display panel is shifted. Therefore, the optical path may be interrupted in a period in which such timing deviation occurs or in a period in which timing deviation may occur.
[203] Instead of using the above-described light shielding device in particular, the image shifting device of FIG. 9 may be improved to provide the "light shielding function" to the image shifting device itself. For example, as shown in FIG. 13, when the light shielding area 21 is disposed in the portion of the glass plate 20 that crosses the light beam in the response delay period or the timing deviation of the image display panel, the color blur of FIG. And generation of ghost can be suppressed, and a higher quality image can be obtained. The center angle of the fan light shielding area 21 is determined according to the magnitude of the response delay of the image display panel. The smaller the ratio of the light shielding area 21 to the entire glass plate 20 is, the brighter the image displayed on the projected surface is.
[204] The relation on the time axis of the period from the start of the response of the image display panel to the end of the image shift until the start of the next image shift, that is, the timing of the image shift period is, for example, It is preferable to adjust as shown in FIG. That is, it is preferable to shift an image in synchronization with the period in which each pixel area of an image display panel shows sufficient brightness.
[205] In the present embodiment, a liquid crystal display panel of TN (twisted nematic) mode is used as the image display panel. However, the present invention is not limited thereto, and other various liquid crystal display panels may be used. By employing a display panel capable of responding at a higher speed, the area ratio of the light shielding area provided to the image shift element can be reduced, thereby making it possible to obtain a brighter and higher quality image.
[206] According to the projection image display device of the present embodiment, three sub-frame images are generated in each frame period and synthesized while optically shifting those images, which is compared with a single-plate projection image display device using a conventional color filter. Thus, the light utilization rate is greatly improved, and three times the resolution can be realized.
[207] In this embodiment, although a transmissive display panel is used as the image display panel, a reflective liquid crystal display panel as shown in Fig. 14 may be used. The reflective liquid crystal display panel shown in Fig. 14 is disclosed, for example, in Japanese Patent Laid-Open No. 97-189809. In the case of using such a reflective image display panel, the white light from the light source does not need to be spectroscopically detected by a dichroic mirror, and the transmissive hologram on the display panel diffracts and splits the white light into R, G, and B light, The light is focused on the reflective electrode (pixel electrode) of the corresponding pixel region. The light reflected from the pixel electrode transmits the hologram according to the amount of change in the polarization component. Such a transmissive hologram is produced by laminating an R holographic lens array layer, a G holographic lens array layer, and a B holographic lens array layer.
[208] In the case of the reflective type, since the transistor region can be provided on the back side (bottom side) of the reflective electrode, it is suitable for the case where the switching of subframe images is carried out collectively.
[209] As described above, in the present invention, information of the same color is always displayed in each pixel area of the image display panel. However, by shifting and projecting the selected subframe image, information of each pixel area can be displayed at different positions (pixels) for each subframe. As a result, high resolution is realized.
[210] (Example 2)
[211] Next, Example 2 of the present invention will be described.
[212] The projection image display apparatus of this embodiment also basically has the same configuration as that of the first embodiment, and the main difference lies in the subframe image shifting method. Therefore, below, only this difference point is demonstrated.
[213] In the first embodiment, as shown in Fig. 12, the direction for shifting the subframe image constituting the n + 1th (n is a positive integer) frame image is the nth Although the same direction as the direction for shifting the subframe image constituting the frame image of , In this embodiment, the direction for shifting the subframe image constituting the n + 1th frame image as shown in FIG. It is opposite to the direction for shifting the subframe image constituting the nth frame image. That is, in the nth frame, the subframe image is shifted downward, and in the n + 1th frame, the subframe image is shifted upward. Nevertheless, in the present embodiment, the first subframe image of the n + 1th frame and the last subframe image of the nth frame are projected at the same position on the projection surface.
[214] In this embodiment, one cycle of image shift is equal to two frame periods, but only four image shifts occur within the two frame periods. For this reason, the image quality deterioration which may be caused by the response delay of the image display panel or the timing shift of the image shift can be reduced. In addition, there are no pixels to be smeared other than the adjacent pixels, and the subfields in which the pixels are smeared are also reduced to two thirds as compared with the case of the first embodiment, and no ghost is generated.
[215] In this way, in order not to shift the subframe image at the time of switching of frames, the operation of the light beam by the image shift element under the same condition is performed in the last subframe in each frame and the first subframe in the next frame. Or stop the movement of the image shift element.
[216] 16 shows an example of an image shift element for performing such image shift. This image shift element is provided with the glass plate 22 which has transparent areas A-F. Transparent regions E and F are formed of FK5 glass having a refractive index of 1.49, transparent regions A and D are formed of BaK4 glass having a refractive index of 1.57, and transparent regions B and C are formed of SF2 glass having a refractive index of 1.64. Each transparent region has a thickness of 2.0 mm.
[217] The disk-shaped glass plate 22 having such a configuration allows the main surface to form an angle of 65 ° with respect to the optical axis. Then, the glass plate 22 is rotated by synchronizing the timing at which each transparent region crosses the optical path with the timing for switching to the corresponding subframe. By doing this, the optical path is shifted by 34.0 µm in the transparent regions A and D and the optical path is shifted by 26.6 µm in the transparent regions B and C with respect to the transparent regions A and D.
[218] It is assumed that the transparent region F corresponds to, for example, the first subframe of the nth frame shown in FIG. In this case, the transparent area A corresponds to the next subframe of the nth frame, and the transparent area B corresponds to the last subframe of the nth frame. The transparent area C corresponds to the first subframe of the n + 1th frame, the transparent area D corresponds to the next subframe of the n + 1th frame, and the transparent area E corresponds to the last subframe of the n + 1th frame. Corresponds to the frame.
[219] Since the transparent region B and the transparent region C have the same refractive index and thickness, the shift amount of the optical path is also the same, and as shown in Fig. 15, no shift occurs between the corresponding two subframe images. The same thing happens between the transparent region E and the transparent region F, too.
[220] Here, the transparent regions B and C or the transparent regions E and F are divided into two regions for convenience of explanation (indicated by broken lines in FIG. 16), but in reality, each of the continuous regions is one continuous line. It can be comprised by a member. Therefore, the disk-shaped glass plate 22 of FIG. 16 can be manufactured by combining four fan-shaped transparent members.
[221] Also in this embodiment, timing shift may occur between image shift and subframe switching due to response delay of the image display panel or the like. Therefore, as shown in Fig. 17, it is preferable to provide the light shielding area 21 in an appropriate portion of the glass plate 22. In FIG. 17, the light shielding area 21 may be provided at the boundary (two sides of each of the transparent areas A and D) to which the image shift should be performed.
[222] Also in this embodiment, although the liquid crystal display panel of TN mode is used as an image display panel, you may use the liquid crystal display panel of other various modes. By employing a display panel that can respond at a higher speed, the area ratio of the light shielding area provided to the image shift element can be reduced, thereby making it possible to obtain a brighter and higher quality image. In this embodiment, a transmissive display panel is used as the image display panel, but a reflective liquid crystal display panel as shown in Fig. 14 may be used.
[223] Even in the projection image display apparatus of this embodiment, since three subframe images are generated in each frame period using an image display panel without color filters, and synthesized while optically shifting those images, a conventional color filter is used. Compared to the single-panel projection image display device, the light utilization rate is greatly improved, and three times the resolution can be realized.
[224] In addition, since the subframe image is not shifted at the time of frame switching, color blurring and ghost caused by the above-described response delay of the image display panel can be greatly reduced.
[225] (Example 3)
[226] Next, Embodiment 3 of the present invention will be described.
[227] The projection image display apparatus of this embodiment also basically has the same configuration as that of the first embodiment, and the main differences are in the configuration and the shift method of the subframe image. This difference will be described below.
[228] In this embodiment, as shown in Fig. 18, the number of subframe images constituting each frame image is two, and each subframe image is sequentially displayed at two different positions on the projected surface. In each frame, by a total of three pixels of one pixel in the first subframe image and two pixels in the second subframe image projected in the vicinity thereof, One pixel on the projection surface is constituted. On the other hand, with respect to the other one pixel adjacent to the one pixel on the projected surface, two pixels in the first subframe image and one pixel in the second subframe image Synthesizing By doing in this way, although the resolution of the image formed in a to-be-projected surface falls slightly, since each frame can be comprised by two subframes, it is not necessary to drive an image display panel at high speed, and the color resulting from a response delay Smears are also reduced.
[229] In this embodiment, an image shift element configured to display a subframe image at two different positions on the projected surface is used. This image shift element is comprised, for example with the glass plate which has two types of transparent areas from which at least one of refractive index and thickness differs.
[230] Also in this embodiment, although the liquid crystal display panel of TN mode is used as an image display panel, you may use the liquid crystal display panel of other various modes. By employing a display panel that can respond at a higher speed, the area ratio of the light shielding area provided to the image shift element can be reduced, thereby making it possible to obtain a brighter and higher quality image. In this embodiment, a transmissive display panel is used as the image display panel, but a reflective liquid crystal display panel as shown in Fig. 14 may be used.
[231] According to the projection type image display apparatus of this embodiment, since two subframe images are generated in each frame period using an image display panel without color filters, and synthesized while optically shifting those images, a conventional color filter is used. Compared with the single-panel projection image display device, the light utilization rate is greatly improved, and higher resolution can be realized.
[232] (Example 4)
[233] Next, Example 4 of the present invention will be described.
[234] The projection image display apparatus of this embodiment also basically has the same configuration as that of the first embodiment, and the main differences are in the configuration and the shift method of the subframe image. This difference will be described below.
[235] In this embodiment, as shown in Fig. 19, the number of subframe images constituting each frame image is two, and each subframe image is sequentially displayed at three different positions on the projection surface. Since each frame can be composed of two subframes, it is not necessary to drive the image display panel at high speed, and color bleeding due to response delay is also reduced.
[236] According to this embodiment, as shown in Fig. 19, although the number of subframe images constituting each frame image is two, each subframe image is sequentially displayed at three different positions on the projected surface, so that image shift is performed. The period of is 1.5 times the frame period. As a result, since the pixel information of R, G, and B overlaps in each pixel on the projection surface, an image with a higher resolution than that in the third embodiment can be obtained.
[237] In the present embodiment, the two subframe images correspond to the subframes constituting the original frame of the video signal, respectively, but the subframe constituting the original frame of the video signal and the display subframes are displayed. There is no need to match the timing exactly. If the display timing of the next subframe is completed, even if the display of the last subframe constituting the original frame of the video signal is completed, the first sub constituting the new original frame is discarded by discarding the video signal of the remaining original frame. You can display the frame. In a normal video, no significant change occurs in the image information between frames or between subframes, so that even if there is a difference between the frequency of the frame to be displayed and the frequency of the original frame, the display can be performed without discomfort. Therefore, according to the present embodiment, the device configuration can be simplified without significantly degrading the display quality.
[238] In addition, unlike the third embodiment, since the image shift element of the present embodiment displays subframe images at three different positions on the projection surface, the image shift element used in the first embodiment is used as it is, and the rotational speed is set to three. It is good to reduce to 2 / min.
[239] Also in this embodiment, although the liquid crystal display panel of TN mode is used as an image display panel, you may use the liquid crystal display panel of other various modes. By employing a display panel that can respond at a higher speed, the area ratio of the light shielding area provided to the image shift element can be reduced, thereby making it possible to obtain a brighter and higher quality image. In this embodiment, a transmissive display panel is used as the image display panel, but a reflective liquid crystal display panel as shown in Fig. 14 may be used.
[240] According to the projection image display apparatus of this embodiment, since two subframe images are generated in each frame period using an image display panel without using a color filter, and synthesized while optically shifting those images, the conventional color is used. Compared with the single-plate projection type image display device using a filter, the light utilization rate is greatly improved, and higher resolution can be realized.
[241] (Example 5)
[242] Next, Example 5 of the present invention will be described.
[243] The projection image display apparatus of this embodiment also basically has the same configuration as that of the first embodiment, and the main differences are in the configuration and the shift method of the subframe image. This difference will be described below.
[244] In this embodiment, the number of subframe images constituting each frame image is four, and each subframe image is sequentially displayed at three different positions on the projected surface, and two out of four subframe images constituting each frame image are displayed. The subframe images are displayed at the same position on the projected surface. That is, the subframe of the present embodiment displays the second subframe in each frame again and again in the data of the generated subframes as in the first embodiment, and displays each frame image in four subframes in total. It consists.
[245] This point will be described in more detail below with reference to FIG.
[246] The image shift in this embodiment is usually performed by one pixel pitch, and the first and third subframe images are respectively positioned on the basis of the second and fourth subframe images in each frame. Direction and downward direction. That is, each frame is composed of four subframes, and one cycle is shifted by four image shifts.
[247] In this embodiment, since the image is reciprocated on a frame basis, it is possible to always shift the image to three different positions in units of one pixel. In addition, since it is possible to shift the image always in units of pixels, even in the frame and also between the frames, the generation of ghost can be prevented as shown in FIG.
[248] In addition, as shown in Fig. 21, when the fourth display subframe is called black display, the number of displays of each color in each frame is the same, so that the color balance between pixels is improved.
[249] Each frame may be composed of five or more subframe images. In that case, it is preferable to disperse | distribute the some subframe image which performs black display in each frame so that the display frequency of each color may become the same in each frame.
[250] In this way, instead of inserting the subframe image to be displayed in each frame into two frames, the two subframe images displayed at the same position on the projection surface may be configured as subframe images with reduced luminance. Specifically, the display image signal may be corrected so that the total light amount of the second and fourth subframe images in each frame is equal to the light amount of the first or third subframe image. . This improves the color balance between the pixels, and also reduces the flickering feeling because the pixels are always displayed. Since the correction amount of the display image signal is always the same correction in all the pixels and each frame, it can be realized with a simple circuit configuration.
[251] The image shift element used in this embodiment is composed of a glass plate 23 having four transparent regions, as shown in FIG. Transparent region A is formed of FK5 glass having a refractive index of 1.49, transparent regions B and D are formed of BaK4 glass having a refractive index of 1.57, and transparent region C is formed of SF2 glass having a refractive index of 1.64. The thicknesses of the transparent areas A to D are all 2.0 mm. The glass plate 23 traverses the optical path with its main surface at an angle of 65 ° with respect to the optical axis, and rotates so that each of the transparent areas A to D corresponds to the subframe image. With respect to the transparent areas B and D, the luminous flux is shifted upward by 34.0 µm in the transparent region A, and the luminous flux is shifted by 26.6 µm in the transparent region C.
[252] Also in this embodiment, although the liquid crystal display panel of TN mode is used as an image display panel, you may use the liquid crystal display panel of other various modes. By employing a display panel that can respond at a higher speed, the area ratio of the light shielding area provided to the image shift element can be reduced, thereby making it possible to obtain a brighter and higher quality image. In this embodiment, a transmissive display panel is used as the image display panel, but a reflective liquid crystal display panel as shown in Fig. 14 may be used.
[253] According to the projection type image display apparatus of this embodiment, since four subframe images are generated in each frame period using an image display panel without color filters, and synthesized while optically shifting those images, conventional color filters are used. Compared to the single-panel projection image display device, the light utilization rate is greatly improved, and three times the resolution can be realized.
[254] As described above, in the projection image display apparatus of the present invention, the original frame images are synthesized by time-dividing each frame image into a plurality of subframe images and superimposing the subframe images while shifting them. The timing for shifting the subframe image is preferably performed in synchronization with the timing for switching the subframe image by the image display panel.
[255] There are two types of methods for switching subframe images. The first method is a "line scan" method. According to this method, a plurality of pixel areas arranged in a matrix form in an image display panel are driven one row or several rows, and are directed from the top to the bottom of the screen. Display a new subframe image vertically. The method of dividing the screen into blocks into several blocks and scanning each row is also included in the "prescan method." On the other hand, the second method is the "surface (collective) writing method". According to this method, all of the plurality of pixel areas arranged in a matrix form in the image display panel are collectively driven to simultaneously drive the entire screen. Display a new subframe image.
[256] The present invention is not limited to the type of scanning method. Below, the Example of a "line scan method" is demonstrated first.
[257] (Example 6)
[258] 23A to 23G show a mode in which the subframe image switching is performed by line scanning in the image display panel. FIG. 23A shows a state in which only the pixel region in the first row of the display panel is switched to display of a new subframe image (for example, the second subframe image). At this point in time, the pixel areas in the second row and later continue to display the old subframe image (for example, the first subframe image). In Figs. 23B to 23G, the scanning lines are moved to the bottom of the screen one by one, and the display area of the new subframe image is enlarged with this. In Fig. 23G, a new subframe image is displayed in the pixel areas of the first to seventh rows.
[259] As described above, in the image display panel driven by the normal scanning line, the boundary line between the new subframe image and the old subframe image moves by one horizontal (1H) period by switching the subframe image. In this case, the start time of applying the voltage in Fig. 11 is shifted at regular intervals for each scan line (row).
[260] Therefore, in the case of using an image display panel driven by a scanning line, it is preferable to synchronize the timing of starting display of a new subframe image and the timing of starting the optical path shift by the image shift element for each pixel. For that purpose, it is preferable that the speed at which the display area of the new subframe image increases (scanning line moving speed) and the speed at which the shift area by the image shift element increases.
[261] Hereinafter, various aspects of the image shift element suitable for such an operation will be described.
[262] The image shift element of this embodiment is composed of a glass plate 24 having six transparent regions, as shown in FIG. Transparent regions A and D are formed of FK5 glass having a refractive index of 1.49, transparent regions B and E are formed of BaK4 glass having a refractive index of 1.57, and transparent regions C and F are formed of SF2 glass having a refractive index of 1.64. All were unified to 2.0 mm in thickness.
[263] By inserting the image shift element so that the main surface of the glass plate 24 has an angle of 65 ° with respect to the optical axis, the image is shifted by 34.0 μm in the transparent areas B and E and 26.6 μm in the transparent areas C and F with respect to the transparent areas A and D. Has been shifted. Each transparent area corresponds to a display subframe. In this image shift element, since the thickness of the glass plate 24 is made constant, it is stable and rotates quietly even at high speed.
[264] In addition, in order to suppress the color bleeding caused by the response delay or the like of the image display panel described with respect to the above-described embodiment, it is preferable to provide the light shielding area 21 between the transparent areas as shown in FIG. Do.
[265] In addition, similarly to the glass plate 20 of FIG. 9, only inexpensive BK7 glass may be used as a glass material. In this case, since the thickness of each transparent region can be selected relatively freely, a more accurate image shift element can be obtained at low cost.
[266] As an improvement of the image shift element, BK7 glass having a refractive index of 1.52 may be used for the transparent areas A and D as the cutout portions of the glass plate 24 and the remaining transparent areas. In this case, if the thicknesses of the transparent regions B and E are set to 0.7 mm and the thicknesses of the transparent regions C and F are set to 1.4 mm, the image shift element is inserted such that the main surface of the glass plate 24 forms an angle of 83.8 ° with respect to the optical axis. With respect to the transparent areas A and D, image shift of 26.0 μm in the transparent areas B and E and 26.0 μm in the transparent areas C and F in the transparent areas B and E can be realized. By adopting such a configuration, the image shift element can be reduced in weight. In addition, since the subframe images corresponding to the transparent areas A and D do not penetrate the glass, the effect of sharpening is also achieved.
[267] As another image shift element, the structure of the glass plate 24 which has six transparent areas may be as follows. That is, the transparent areas A and D are formed of FK5 glass having a refractive index of 1.49, and the thickness thereof is 2.0 mm. The transparent areas B and E are formed of BK7 glass having a refractive index of 1.52 and the thickness thereof is 2.09 mm. Transparent areas C and F are formed of SF2 glass having a refractive index of 1.64, and the thickness thereof is 2.0 mm. In this case, when the glass plate is inserted at an angle of 65 ° with respect to the optical axis, it is 25.9 μm in the transparent areas B and E for the transparent areas A and D, and 26.8 μm in the transparent areas C and F for the transparent areas B and E. Image shift can be realized. Thus, by selecting the glass plate which is easy to mass-produce and adjusting the thickness, it becomes possible to manufacture the image shift element of higher precision at low cost, while making the difference of the thickness between transparent areas comparatively small.
[268] In addition, although the main part of the said image shift element is comprised from the transparent plate all formed from the glass material, the image shift element in this invention is not limited to this. As long as it is a transparent material which causes refraction of an optical path, resin, such as plastic, may be sufficient.
[269] As described above, in order to shift the optical path of the subframe image using the transparent plate which is inclined with respect to the optical axis, a transparent plate having a plurality of transparent regions having at least one of a refractive index and a thickness may be produced. The thickness of the transparent plate can be easily adjusted by techniques such as surface polishing and etching.
[270] When the main surface of the transparent plate is inclined at an angle of 45 to 85 degrees with respect to the optical axis, it is possible to select an appropriate value in the range of about 1.45 to 1.7 refractive index to realize the required image shift amount. Since the transparent plate having such a refractive index can be formed of a general glass material, an image shift element can be manufactured at low cost.
[271] When the main surface of the transparent plate is inclined at an angle of 66 to 88 ° with respect to the optical axis, it is possible to select an appropriate value in the range of about 0.5 to 2.0 mm in thickness of the transparent plate to realize the required image shift amount. When the main surface of the transparent plate is inclined at an angle of 61 to 80 ° with respect to the optical axis, an appropriate value is selected in the range of about 0.5 to 2.0 mm and the refractive index of about 1.45 to 1.7. It is possible to realize the required image shift amount.
[272] (Example 7)
[273] In the case of pre-scanning in the vertical direction of the screen, the boundary (image switching boundary) of the nth subframe image and the n + 1th subframe image is shown by horizontal line segments as shown in FIG. This segment moves from top to bottom.
[274] When image shift is performed using the rotating plate as described above, as shown in Fig. 26, the boundary line (the boundary of the image shift area) of adjacent transparent areas in the glass plate 24 is centered on one point. Because of this rotation, the boundary line and the switching part of the subframe image do not become parallel and may be shifted. When such a deviation occurs, the part of the subframe image to be shifted is not shifted correctly, and the part of the old subframe image which should not be shifted is shifted.
[275] In order to eliminate such a problem, as described with respect to Embodiment 1, the light emitted from the image display panel may not be projected onto the projection surface only during a period in which the timing deviation occurs using various methods.
[276] In this embodiment, instead of providing the light shielding portion, the image shift element is constituted by the glass plate 25 having three transparent regions as shown in FIG. ) Is reciprocated in the vertical direction by the drive device, thereby realizing the shift of the image.
[277] In the present embodiment, the transparent region A of the glass plate 25 is formed of FK5 glass having a refractive index of 1.49, the transparent region B is formed of BaK4 glass having a refractive index of 1.57, and the transparent region C is formed of SF2 having a refractive index of 1.64. The thickness of each transparent region is all set to 2.0 mm. When the glass plate 24 is inserted into the optical path with the main surface at an angle of 65 ° with respect to the optical axis, an image shift of 34.0 μm in the transparent region B with respect to the transparent region A and 26.6 μm in the transparent region C with respect to the transparent region B is obtained. Is done.
[278] According to the present embodiment, it is possible to match the boundary position (boundary of the image shift area) of the adjacent transparent area in the glass plate 25 with the boundary of image switching. Therefore, since all the pixels displaying the information of the new subframe image are shifted at an appropriate timing, an image with less color blur can be obtained.
[279] Further, even in the case of using the image shift element of the present embodiment, depending on the image display panel, problems such as color bleeding due to response delay may occur. In such a case, it is preferable to provide a light shielding area (not shown) at the boundary of each of the transparent areas A to C shown in FIG.
[280] According to the present embodiment, image shift is performed in synchronization with switching of images while keeping the scanning lines of the image display panel and the boundary lines of the plurality of transparent regions substantially parallel. In order to realize such an image shift, in the present embodiment, the glass plate 25 as shown in Fig. 27 is reciprocated, but other means can be maintained as long as the boundary line of each transparent area can maintain a parallel relationship with the scanning line of the image display panel. May be used. For example, the transparent regions A to C shown in FIG. 27 may be formed of individual glass plates 26, and the glass plates 27 may be operated by the driving apparatus shown in FIG. Even with this operation, the boundary lines of the plurality of transparent regions can be moved in synchronization with the line scanning while maintaining a substantially parallel relationship with the scanning lines of the image display panel. The same effect can also be achieved by arranging the transparent plates corresponding to the transparent areas A to C on the same optical path and rotating them while being placed on the optical path sequentially.
[281] (Example 8)
[282] Next, another embodiment of the image shift element will be described with reference to FIGS. 29-31. The image shift element of this embodiment is composed of a plurality of microprisms or diffraction gratings and the like designed so that the shift amount on the projected surface is different, and the image shift element is moved in and out on the optical path.
[283] First, reference is made to FIG.
[284] In this embodiment, the prism surface of the microprism plate formed of the glass of refractive index n1 is covered with the resin material of refractive index n2. When the light incident perpendicularly to the non-prism surface (smooth surface) of this microprism plate changes to the optical path at an angle θ ₁ , the image is shifted by one pixel on the projection surface. The pitch of the pixel region on the image display panel 8 is P, and the distance between the pixel region surface of the image display panel 8 and the prism surface (refractive surface) is Z. In this embodiment, the structure of the microprism plate is designed so that θ ₁ = tan ⁻¹ (P / Z).
[285] In this embodiment, FK5 glass is used as the material of the microprism plate, and Loctite's Loctite 363 is used as the UV curable resin on the surface of the prism face, and the prism face side leveling is performed.
[286] If the pitch P of the pixel region is 26 μm, the distance Z is 5 mm, the inclination angle of the microprism is θ ₂ (= incident angle of the light beam to the inclined plane of the microprism), and the emission angle of the light beam after refraction by the microprism is θ ₃ , Θ ₁ is 0.3 ° from the above equation.
[287] Here, since the refractive index of glass is n1 and the resin has n2, the relationship between θ2 and θ3 depends on Snell's law (n1 · sinθ ₃ = n2 · sinθ ₂ ), and the relationship of θ ₂ = θ ₃ + θ ₁ There is. For this reason, when the refractive index of FK5 glass is 1.487 and the refractive index of Loctite 363 is 1.520, when the inclination-angle (theta) ₂ of a microprism is set to 13.7 degrees, the shift amount equivalent to pitch P can be obtained.
[288] In addition, if various parameters are selected so as to satisfy the above formula, the material and numerical values of the present embodiment are not limited. In addition, leveling a prism surface with resin is indispensable, and may be abbreviate | omitted.
[289] When the prism plate or diffraction grating shown in Fig. 29 is used as the image shift element, the distance between the image display panel 8 and the image shift element is defined by a constant distance Z. After the above-described optical design is completed, It is not possible to change the distance to any size.
[290] Without this limitation, in order to obtain an image shift element that can be inserted at any position on the optical path, as shown in FIG. 30, the aforementioned microprism plate or diffraction grating may be opposed to each other. What is necessary is just to fill between a pair of microprism boards, or between a pair of diffraction gratings with the resin material etc. which have refractive index n2 different from these materials. Two microprism plates can be formed, for example, from SF2 glass, and these two microprisms can be bonded using, for example, Loctite's UV curable resin Loctite 363. The distance Z between the microprism plates is, for example, 1 mm. In this case, since the refractive index of SF2 glass is 1.64 and the Loctite 363 is 1.52, when the inclination angle θ of the microprism is 19.6 °, the shift amount ΔD of the optical path is about 26 μm.
[291] In order to display a subframe image between three different points on the projection surface, an element 27 in which the elements shown in Figs. 29 and 30 are combined, for example, as shown in Fig. 31 may be produced. This element 27 is designed such that the region A and the region B each have different shift amounts ΔD. If such an element 27 is periodically operated so as not to be inserted into the optical path in one subframe period and inserted into the optical path in another subframe period, an appropriate image shift can be executed.
[292] In the example of Figs. 29 and 30, the shift of the luminous flux occurs in the in-plane direction of the drawing, but since the shifting direction of the boundary line of the shift area and the shifting direction of the luminous flux can be considered independently, the shifting direction of the luminous flux is It is not limited to the example shown.
[293] The light beams passing through the image shift element are irradiated onto the projected surface through different optical paths by the transparent areas to be transmitted. For this reason, the optical path length between the image display panel and the projection surface varies for each subframe, and it becomes impossible to focus on an image corresponding to all of the transparent areas, thereby degrading the image quality. In order to prevent such deterioration of image quality, inserting a transparent plate to compensate the difference in optical path length due to the transparent plate of the image shift element into the optical path and operating (rotating or moving) while synchronizing with the transparent plate of the image shift element. desirable. By doing so, a homogeneous picture quality can be obtained in each subframe.
[294] (Example 9)
[295] When switching of the subframe image is performed almost simultaneously in the entire screen of the image display panel, it is preferable that the shift of the subframe image is also performed simultaneously in the entire screen. By doing so, it is difficult to cause timing shift between switching of the subframe image and image shift, and deterioration of image quality is prevented.
[296] Such image shift is preferably performed within the vertical blanking period. However, in consideration of the delay of the response of the image display panel, the image shift may be executed at a timing delayed from the start of switching of the subframe image.
[297] The configuration of an image shift element that is suitably employed in the case of the screen batch writing method will be described below.
[298] First, reference is made to FIG. 32 and FIG. The illustrated image shift element includes a first element (liquid crystal element) g1 for modulating the polarization direction of a subframe image modulated by the image display panel, and a second element (crystal plate) having a different refractive index depending on the polarization direction of light. has (g2) In this specification, the phrase "polarization direction" means the vibration direction of the electric field vector of light. The polarization direction is perpendicular to the propagation direction k of light. In addition, the plane containing both an electric field vector and the propagation direction k of light shall be called a "vibration surface" or a "polarization surface."
[299] In the example shown, the light exiting the image display panel is polarized in the vertical direction (polarization direction = screen vertical direction). When no voltage is applied to the liquid crystal layer of the liquid crystal element g1, as shown in FIG. 32, the polarization plane of the light exiting the image display panel does not rotate in the course of the light passing through the liquid crystal element g1. Do not. On the other hand, when an appropriate level voltage is applied to the liquid crystal layer of the liquid crystal element g1, as shown in Fig. 33, the polarization plane of the light exiting the image display panel is rotated by 90 degrees by the liquid crystal layer. In addition, although the case where a rotation angle is 90 degrees is illustrated here, according to the design of a liquid crystal layer, it is possible to set a rotation angle arbitrarily.
[300] The crystal plate g2 is a single crystal (positive crystal) and has birefringence, and thus shows a refractive index different depending on the direction. The quartz plate g2 is disposed so that its light incident surface is perpendicular to the optical axis (parallel to the propagation direction k) of the incident light. The optical axis of the quartz plate g2 is included in the vertical plane in FIGS. 32 and 33, but is inclined from the light incidence plane of the quartz plate g2. For this reason, as shown in Fig. 32, when light having a perpendicular polarization direction is incident on the crystal plate g2, the light is refracted in the plane including the optical axis in accordance with the inclination of the optical axis in the crystal plate, and the light is in the vertical direction. Is shifted to. In this case, the plane (henceforth a "major end surface") containing both the optical axis of the quartz plate g2 and the optical axis of incident light is in parallel with the polarization plane of incident light. The incident light in which the polarization plane is parallel to the main end face in this manner is "ideal light" in the quartz plate g2.
[301] On the other hand, as shown in Fig. 33, when light in which the polarization plane is horizontally transversely incident on the quartz plate g2, since the polarization plane is orthogonal to the optical axis (or main end surface) of the quartz plate g2, the light is refracted. And no shift of the luminous flux occurs. In this case, the light incident on the quartz plate g2 is "normal light" in the quartz plate g2.
[302] In this way, the polarization direction of the light incident on the quartz plate g2 can be controlled according to whether or not a voltage is applied to the liquid crystal element g1 to adjust the shift of the luminous flux.
[303] Here, the thickness of the quartz plate g2 is now t, and the refractive indices of the abnormal light and the normal light of the quartz plate g2 are n _e1 and n _o1 , respectively. In addition, when the optical axis is inclined at 45 ° from the incident surface in the main end surface, the shift amount ΔD of the light beam is expressed by the following equation.
[304]
[305] From this equation, it can be seen that the shift amount ΔD of the luminous flux and the thickness t of the quartz plate g2 are proportional to each other. By adjusting the thickness t of the quartz plate g2, the shift amount of the subframe image can be set to an arbitrary value.
[306] In the image shift element of this embodiment, the liquid crystal layer is sandwiched by a pair of transparent electrodes, whereby an appropriate voltage can be applied to the entire liquid crystal layer at once. For this reason, when this image shift element is used, an appropriate image shift can be realized even in the screen batch write mode.
[307] In addition, if the electrode structure provided in the liquid crystal device is improved, a voltage can be applied only to a selected region of the liquid crystal layer. By using a liquid crystal element having such an electrode, an image shift element that can be applied even when driven by the above-described line scanning method can be constituted.
[308] In the present embodiment, an example in which the polarization direction of incident light is rotated by 90 ° when a predetermined voltage is applied to the liquid crystal element and the polarization direction is not rotated when no voltage is applied is described. You may make it.
[309] (Example 10)
[310] Next, reference is made to FIGS. 34 and 35. The illustrated element has a liquid crystal layer i5 and two transparent substrates sandwiching the liquid crystal layer i5, and a microprism array is formed on the liquid crystal side surface of one transparent substrate. More specifically, the image shift element of this embodiment includes a transparent substrate on which a microprism array i3 is covered with a transparent electrode i1 and an alignment film i2, and a transparent electrode i1 and an alignment film i2. It is a liquid crystal element in which the nematic liquid crystal layer i5 is sandwiched by a transparent substrate on which a surface is covered. The liquid crystal layer i5 is oriented homogeneously, and when a voltage is applied between the two transparent electrodes i1, the liquid crystal layer i5 is aligned in a direction perpendicular to the substrate as shown in FIG. 34, but in a state where no voltage is applied. 35, it is in a homogeneous alignment state as shown in FIG. The refractive index of the liquid crystal layer i5 when no voltage is applied is set to n _e2 , and the refractive index of the liquid crystal layer i5 when the voltage is applied is set to n _o2 . In this embodiment, the _microprism array i3 is formed of a material having a refractive index close to n _o2 .
[311] Since no difference in refractive index occurs between the liquid crystal layer and the microprism array i3 when no voltage is applied, the luminous flux incident on the microprism array i3 is refracted according to Snell's law. In contrast, when a voltage is applied, the refractive index difference between the liquid crystal layer and the microprism array i3 decreases according to the magnitude of the applied voltage. As the refractive index difference decreases, the refractive angle of the light beam incident on the microprism array i3 also decreases.
[312] When the right angle of the microprism is θ ₄ and the refractive index of the microprism array i3 is n ₂ , the refractive angle δ of the light beam when no voltage is applied to the liquid crystal layer i5 is expressed by the following equation. It is expressed as
[313]
[314] Moreover, in order to enlarge a refractive angle, it is preferable to use the liquid crystal layer with large refractive index anisotropy.
[315] When the two elements are combined and arranged as shown in Fig. 36, the image shift element of this embodiment is formed. The shift amount [Delta] D of the image by this image shift element is expressed by the following expression when the distance between two microprism arrays is L. FIG.
[316]
[317] In this embodiment, after the on-time (頂角) θ ₄ of the thickness of a glass sheet 0.5 mm, minute prism array spacing 1.0mm, a minute prism 10 °, Merck Corporation's serial number of the liquid crystal material BL-009 I use it. In this case, the refractive index n _e2 is 1.82, the refractive index n _O2 is 1.53, and the range of the shift amount ΔD is 0 to 50.7 μm. That is, according to the image shift element of this embodiment, the shift of about two pixels is possible.
[318] In place of the microprism array i3, a diffraction grating having a predetermined lattice spacing may be provided on the transparent substrate. By selecting an appropriate grating interval in accordance with the wavelength of the incident light, the light can be diffracted at a desired diffraction angle.
[319] In addition, even in the case of the screen batch writing method, if the response delay of the image display panel occurs, the above-described problem of color bleeding and ghosting occurs. Therefore, it is preferable to arrange | position a light shielding device, such as a liquid crystal shutter and a mechanical shutter, on an optical path, and to block the light from an image display panel, while delaying the response in an image display panel.
[320] Also for the image shift element of the present embodiment, an image display panel of a type that performs the switching of subframe images on a screen sequentially by providing a circuit for dividing the electrode into a plurality of portions and sequentially driving the plurality of divided portions. It is possible to combine with. In this case, it is applicable not only when the switching of the image is performed by the scanning line but also when the switching of the image is performed in units of blocks consisting of a plurality of rows or a plurality of columns of pixels.
[321] (Example 11)
[322] Next, with reference to FIG. 37, the structural example of the system of the projection type image display apparatus by this invention is demonstrated.
[323] 37, the image signal processing circuit 100, an illumination optical system (light source, etc.) 102, an image display panel (liquid crystal display element) 104, and an image shift element 106 are shown in FIG. , An image shift element control circuit 108, and a projection lens 110.
[324] Since the illumination optical system 102, the image display panel 104, the image shift element 106, and the projection lens 110 have already been described, the image signal processing circuit 100 and the image shift element control will be described below. The relationship of each component is demonstrated centering on the circuit 108. As shown in FIG.
[325] The video signal processing circuit 100 in this embodiment includes an input signal selection circuit 120, an image demodulation circuit 122, a Y / C separation circuit 124, a scaling circuit 126, and a frame rate. It consists of a conversion circuit 128, a frame memory circuit 130, a system control circuit 132, and a color signal selection circuit 134.
[326] The input signal selection circuit 120 can receive a plurality of types of video signals, and performs processing according to the type of the video signals. The video signal includes signals divided into R, G, and B (RGB signals), luminance signals Y and chrominance signals BY and RY (Y / C signals), and color signals C and luminances in which color carriers are modulated into chrominance signals. And a composite video signal (composite signal) obtained by frequency multiplexing the signal Y.
[327] The Y / C signal is demodulated by the image demodulation circuit 122 past the input signal selection circuit 120. The composite signal is passed through the input signal selection circuit 120, separated by the luminance signal Y and the color signal by the Y / C separation circuit 124, and then transmitted to the image demodulation circuit 122 and demodulated. The video demodulation circuit 122 outputs the RGB signal demodulated from the video signal.
[328] The RGB signal input to the input signal selection circuit 120 and the RGB signal output from the image demodulation circuit 122 are transmitted to the scaling circuit 126. The scaling circuit 126 converts the number of pixels of various input signals into the number of pixels of the image display panel 104. The frame rate conversion circuit 128 converts the frame rate of the input video signal into a frame rate suitable for the operation of the system.
[329] The frame memory circuit 130 is composed of three frame memories for storing each of the R signal, the G signal, and the B signal. The data read out sequentially from each frame memory is selected by the color signal selection circuit 134 in an appropriate order and sent to the drive circuit portion of the image display panel 104. The image display panel 104 displays a subframe image based on the data output from the color signal selection circuit 134.
[330] The system control circuit 132 controls the operations of the input signal selection circuit 120, the frame memory 130, the color signal selection circuit 134, and the image shift element control circuit 108.
[331] The image shift element control circuit 108 controls the operation of the image shift element 106 to synchronize with the display of the subframe image based on the signal output from the system control circuit 132.
[332] Next, the procedure of reading data from the frame memory of the RGB signal will be described with reference to FIGS. 38 and 39. FIG.
[333] The rate (frequency f _in ) of signal writing to the frame memory depends on the input signal, but the rate (frequency f _out ) of signal reading from the frame memory is defined by the clock frequency of this system. The frequency f _in is, for example, 60 hertz (Hz), and the frequency f _out is, for example, 180 Hz.
[334] In response to the control signal output from the system control circuit 132, the R signal from the R frame memory 130a, the G signal from the G frame memory 130b, and the B signal from the B frame memory 130c. The B signal is read. The read rate of these signals is f _out as described above, and the read operation from each frame memory 130a to 130c is repeatedly executed three times in each frame period.
[335] Reference is made to FIG. 39 next. The illustrated timing chart corresponds to the case of forming three types of subframe images shown in FIG. The numerals shown at the top of Fig. 39 are the scanning line numbers of the original frame.
[336] When displaying the first sub-frame image on the image display panel, data stored at an address corresponding to the scanning line number 1 of each frame memory 130a to 130c is read out simultaneously. Since the start signal is output at this timing, the line scanning of the image display panel 104 is started. Data (R, G, and B signals) read out from each of the frame memories 130a to 130c are transferred to the color signal selection circuit 134 shown in FIG. 38, but only the R signal is selected by the color signal selection circuit 134. FIG. Then, it is sent to the image display panel 104. The color signal selection circuit 134 has R, G, and B switching elements that operate according to the R, G, and B selection signals, and only the switching elements that receive the logic high selection signal output the input signal to the output. To pass. In the example of Fig. 39, only the R signal is selected, and is given to the first row pixel area (the pixel area for R) of the image display panel 104.
[337] After the elapse of one horizontal scanning period (1H period), the R selection signal changes to logic low and at the same time, only the G selection signal changes to logic High. For this reason, of the data stored in the address corresponding to the scanning line number 2 of the original frame in each of the frame memories 130a to 130c, only the G signal read out from the G frame memory passes the color signal selection circuit 134 and the image. It is transmitted to the display panel 104. Based on this G signal, display of the second row pixel area (G pixel area) of the image display panel 104 is performed.
[338] By the same procedure as below, data for the first subframe image is sequentially generated, and the subframe image as described on the right side of FIG. 6 is displayed on the image display panel.
[339] In the case of displaying the second subframe image, as shown in Fig. 39, the timing of applying the start pulse signal and the selection signal is delayed by 1H period. That is, among the data corresponding to the scanning line number 2 of the original frame, the R signal stored in the R frame memory is selected by the color signal selection circuit 134. Then, based on this R signal, the first row image area (the pixel area for R) in the image display panel 104 is displayed. Subsequently, the same operation is repeated, so that the second subframe image as shown in FIG. 6 is displayed on the image display panel 104.
[340] In the case of displaying the third subframe image, the application timing of the start pulse signal and the selection signal is delayed for another 1H period. As a result, the third subframe image as shown in Fig. 6 can be displayed.
[341] As described above, instead of leaving the application timing of the start signal for each subframe, the read start address of the frame memory may be traversed among a plurality of addresses corresponding to the scanning lines Nos.
[342] In this example, the case where each of the R, G, and B pixel areas are arranged to be parallel to the scanning line is described. However, the present invention is not limited to such a system. If the 1H period is replaced with a period of dot clock, it corresponds to the system operation in the case of using an RGB longitudinal stripe type image display panel in which each of the R, G, and B pixel areas is arranged to be orthogonal to the scanning line.
[343] The circuit of Fig. 38 is not provided with a special frame memory for storing the data of the subframe image. However, such a frame memory may be provided to temporarily store the subframe image.
[344] (Example 12)
[345] Hereinafter, an embodiment of a projection type image display apparatus provided with two image display panels will be described. In the projection image display device of this embodiment, as shown in Fig. 40, a plurality of liquid crystal display panels 18 are provided with light from the light source 1, the liquid crystal display panel 18, and the light source 1 according to the wavelength range. Light control means for condensing on the corresponding pixel region in the pixel region of the pixel region, and a projection optical system for projecting the light modulated by the liquid crystal display panel 18 onto the projection surface. Moreover, the apparatus of this embodiment is further provided with one liquid crystal display panel 28, and the light of a specific wavelength range among the white light emitted from the light source 1 is irradiated to the liquid crystal display panel 28. FIG.
[346] This apparatus is provided with the dichroic mirrors 14-16, and the light of the wavelength range selectively reflected by the dichroic mirror 14 is reflected by the mirror 40, and then the liquid crystal display panel (28) is investigated. On the other hand, the light reflected by the dichroic mirrors 15 to 16 is incident on the microlens array 17 of the liquid crystal display panel 18 at different angles depending on the wavelength range. Light incident on the microlenses 17 at different angles is focused on corresponding pixel regions at different positions, respectively.
[347] Light modulated by the first liquid crystal display panel 18 passes through the field lens 9a, the image shift element 10, the polarizing beam splitter (or dichroic prism) 42, and the projection lens 11. After that, it is projected onto the screen 13. In contrast, the light modulated by the second liquid crystal display panel 28 passes through the field lens 9b, the polarizing beam splitter 42, and the projection lens 11, and is then projected onto the screen 13. .
[348] In this embodiment, the image shift element 10 shifts the light modulated by the first image display panel 18 by the same method as the method described with respect to the other embodiments. In the first image display panel 18, two subframe images composed of, for example, R and B colors are displayed, and the shift amount between the subframe images is set to be substantially equal to the pixel pitch measured along the shift direction. The data of each subframe image is produced by combining the data (R and B signals) of the R picture frame and the B picture frame shown in Figs. 4B and 4D.
[349] In contrast, the second image display panel 28 displays an image composed of only G colors, for example. This image has a pattern as shown in Fig. 4C and reflects data of G color for all pixels of the frame image.
[350] In the second image display panel 28, since it is not necessary to display the image by dividing it into subframes, the first image display panel is, for example, in order to make the balance of the R, G, and B color lights for illuminating the projection surface appropriate. It is necessary to compensate for the luminance or compensate the display period between the 18 and the second image display panel 28. For example, the display period of the image emitted from the second image display panel 28 and projected onto the screen may be limited to about one half of one frame period, and the luminance may be reduced instead.
[351] According to this embodiment, only two colors of the R, G, and B colors are displayed on the first image display panel 18. The remaining colors are displayed on the second image display panel 28. In the first image display panel 18, each of the microlenses separates incident light into two colors and focuses them on the corresponding pixel region. Therefore, the pitch and focal length of the microlens 17 can be set to two thirds of the pitch and focal length of the single-plate type microlens 7.
[352] As described above, in the present invention, a frame image is obtained by shifting a subframe image and superimposing a plurality of subframe images in time. When the viewing line of observation is substantially fixed, as shown in Fig. 41A, the superposition of the pixels of RGB is appropriately and surely achieved. However, as shown in Fig. 41B, when the observer's eye shifts in accordance with the shift of the subframe image, the observer's retina overlaps in time as if the subframe image is not sufficiently shifted. When the speed of eye movement is close to the shift speed of the subframe image, as shown in Fig. 41C, the observer seems to have lowered the shift speed of the subframe image. When the speed of eye movement and the shift speed of the subframe image are almost the same, the subframe image appears not to be shifted. As a result, the pixel arrangement on the image display panel is observed, and the resolution is reduced to the extent of the pixel arrangement constituting the image display panel.
[353] This phenomenon occurs because the eye movement direction and the speed substantially coincide with the shift direction and the shift speed of the subframe image. For this reason, by studying the pattern of shift of the subframe image, it becomes possible to reduce the influence of this phenomenon. The effect of the reduction can be evaluated by examining the spatial frequency characteristics (frequency spectrum) of the pattern of two-dimensional pixel arrays arranged along the time axis (t-axis) of pixels in one column along the shift direction (for example, y direction) of the subframe image. Can be. This two-dimensional pixel array expresses the shift pattern of the subframe up and down in the y-axis direction in a space (y-t space) in which the vertical axis is the y axis and the horizontal axis is the time axis (t axis). In order to analyze the motion pattern of the subframe image shifted in the y-axis direction on the projection surface, a two-dimensional Fourier transform is performed on the pixel array in the yt space, and the spectrum regarding the spatial frequency in the y-axis direction and the spatial frequency in the t-axis direction It is effective to evaluate it. Since the pixel arrangement of the y-t space has a regular pattern side by side on the lattice point, the frequency spectrum thereof is represented as a local point in the Fourier space (fy-ft space).
[354] As an example, a spectrum obtained by Fourier transforming the pixel array in the y-t space shown in FIG. 15 is shown in FIG. 42A. In Fig. 42A, each local point indicated by a circle corresponds to the spatial frequency of the pixel arrangement in the y-t space.
[355] In the case where the subframe image is shifted in a relatively monotonous pattern as shown in Fig. 15, when the line of sight moves at a specific speed in a specific direction, the above-mentioned phenomenon suddenly occurs. To avoid this, it is necessary to complicate the shift pattern of the subframe image and to distribute the spatial frequency into a plurality of components. Specifically, in the yt space, for example, a portion in which the pixels of R rise and fall in parallel with the portions arranged in parallel with the portions in which the pixels of R rise upwards and extends in a straight line is included. The arrangement is preferable because the spatial frequency of the pixel arrangement is dispersed. When the spatial frequency of the pixel array in the y-t space is dispersed, the local point of the spectrum in the Fourier space is also dispersed.
[356] Therefore, if the local point in the Fourier space (fy-ft space) determines the pattern of the pixel arrangement in the y-t space so as to be more dispersed, it is easy to suppress the disadvantage that the above phenomenon occurs at a specific eye movement speed.
[357] In addition, if the pattern of the pixel arrangement in the y-t space is determined so that the local point in the Fourier space is symmetrical with respect to the fy axis, it is easy to suppress the disadvantage that the above phenomenon occurs in a specific eye movement direction.
[358] Further, if the pattern of pixel arrays in the y-t space is determined so that the local point in the Fourier space is located in the region of fy <ft as much as possible, the above phenomenon hardly occurs at a relatively slow eye movement speed.
[359] In the present invention, since three pixels of RGB are superimposed temporally, a pixel of a desired color is formed, so that an image is constructed by combining three subframe images shifted with each other as a unit. 43 shows six kinds of subsets 1A to 3A and 1B to 3B each composed of three subframes. The shift patterns that can be employed in the present invention are all obtained by combining the six kinds of subsets in FIG. The six kinds of subsets are classified into an A group including the subsets 1A to 3A and a B group including the subsets 1B to 3B. The A group and the B group are in opposite (symmetrical) shift directions. For example, in the subset 1A, the subframe images are shifted by one pixel in the + y direction, whereas in the subset 1B, the subframe images are shifted by one pixel in the -y direction. Similarly, the subset 2A is a subset. Symmetric with 2B and subset 3A is symmetric with subset 3B.
[360] In the embodiments described later, a combination of these subsets is appropriately combined to form a shift pattern to suppress the deterioration of display quality due to the observer's eye movement.
[361] In addition, the effect of the phenomenon due to the eye movement can be reduced by studying the pixel arrangement of the image display panel. That is, this phenomenon occurs most remarkably when the shift of the subframe image and the movement of the gaze are completely coincident, but in this case, the actual pixel array on the image display panel is observed by the viewer. For this reason, it is possible to perform Fourier transform on the pixel array (x-y space) on the image display panel and to evaluate in the Fourier space. Specifically, while satisfying the condition that three pixels of RGB are linearly arranged along the shift direction, in the Fourier space of the pixel array (xy space), a pixel array in which local points exist as far from the origin as possible ( xy space). By adopting such pixel arrangement (x-y space), the spatial resolution for each color is improved.
[362] In view of this, an embodiment in which the shift pattern of the subframe image is improved to be more preferable will be described below.
[363] (Example 13)
[364] The projection image display apparatus of this embodiment basically has the same configuration as that of the first embodiment, and the main difference lies in that a shift pattern of a subframe image that can alleviate the above-described phenomenon is adopted. . Therefore, below, only this difference is demonstrated.
[365] In the case of the first embodiment, as shown in Fig. 12, there are three subframe images constituting the n + 1th (n is positive integer) frame images, and the direction in which they are shifted. Is the same as the direction in which the subframe image constituting the nth frame image is shifted, but in this embodiment, as shown in FIG. 44, the shift pattern of the subframe image has six subframe images (subset). One cycle is made by 1A and subset 2B). By combining the subset 1A and the subset 2B as shown in Fig. 44, one period of the shift pattern includes two shifts of two pixels (two times in the + y direction and the -y direction). The shift pattern in FIG. 44 has a local point of spectrum as shown in FIG. 42B in the corresponding Fourier space. Comparing this with the case of Fig. 42A, it can be seen that the local point shown in Fig. 42B is dispersed even though one cycle of the shift pattern is configured in the same number of subframes. As a result, in the present embodiment, the above-described phenomenon is less likely to occur than in the case of the first embodiment in the specific eye movement direction and the specific movement speed. In addition, since one period is composed of six subframes, one period is relatively short, and the configuration of the image shift element is also relatively simple.
[366] According to the shift pattern of the subframe image used in this embodiment, one frame may be composed of two subframes or three subframes.
[367] 45 shows an example of an image shift element for performing such image shift. This image shift element is provided with the glass plate 22e which has transparent areas A-F. Transparent areas A and D are formed of FK5 glass having a refractive index of 1.49, transparent areas B and F are formed of BaK4 glass having a refractive index of 1.57, and transparent areas C and E are formed of SF2 glass having a refractive index of 1.64. Each transparent region has a thickness of 2.0 mm.
[368] The disk-shaped glass plate 22e having such a configuration allows the main surface to form an angle of 65 ° with respect to the optical axis. Then, the glass plate 22e is rotated by synchronizing the timing at which each transparent region crosses the optical path with the timing for switching to the corresponding subframe. In this way, the optical path is shifted by 34.0 µm in the transparent regions B and F with respect to the transparent regions A and D, and the optical path is shifted by 26.6 µm in the transparent regions C and E with respect to the transparent regions B and F. FIG.
[369] It is assumed that the transparent area A corresponds to, for example, the first subframe shown in FIG. In this case, the transparent area B corresponds to the next subframe, and the transparent area C also corresponds sequentially after the transparent area C. FIG.
[370] Also in this embodiment, timing shift may occur between image shift and subframe switching due to response delay of the image display panel or the like. Therefore, as shown in Fig. 17, it is preferable to provide the light shielding area 21 in an appropriate portion of the glass plate 22. In FIG. 17, the light shielding area 21 may be provided at the boundary (two sides of each of the transparent areas A and D) to which the image shift should be performed.
[371] Of course, as the image shift element, there is no problem even with the image shift element described in another embodiment.
[372] In this embodiment, the pixel arrangement as shown in Fig. 46 is adopted as the pixel arrangement of the image display panel. For example, the shapes of the pixel array as shown in Fig. 47 and the Fourier space of the pixel array in Fig. 46 are shown in Figs. 48A and 48B, respectively. It can be seen that the local shop is located farther from the origin in Fig. 48A. This means that in Fig. 46 and Fig. 47, the interval between straight lines connecting pixels of the same color is narrower in Fig. 46, that is, the spatial frequency of each color is high. As can be seen from the above, even when the pixel arrangement of the image display panel is visually recognized by adopting the pixel arrangement as shown in Fig. 46 and the visual shift and the subframe image shift are almost identical, the adverse effect on the image quality is less. Lose.
[373] Even in the projection image display apparatus of this embodiment, three sub-frame images are generated in each frame period using an image display panel without color filters, and are synthesized while optically shifting those images. Compared to the single-panel projection image display device, the light utilization rate is greatly improved, and three times the resolution can be realized. Of course, two sub-frame images may be generated in each frame period and synthesized while optically shifting those images. Although there is a slight awkward movement in the moving image, the rate of subframe switching is so slow that the liquid crystal responds sufficiently, and a state with better transmittance can be obtained.
[374] (Example 14)
[375] The projection image display apparatus of this embodiment also basically has the same configuration as that of the thirteenth embodiment, and the main difference lies in the shift pattern of the subframe image. Therefore, below, only this difference is demonstrated.
[376] In the thirteenth embodiment, as shown in FIG. 44, one period of the shift pattern of the subframe image is composed of six subframe images (subsets 1A and 2B). In this embodiment, FIG. 49 As shown in Fig. 1, one period of a shift pattern of a subframe image is composed of 18 subframe images (six subsets). In this embodiment, subset 1A and subset 3A are selected from the group A of the subset, subset 1B and subset 2B are selected from the group B of the subset, and then the subset of group A and the group B are selected. The subsets are alternately placed. Arranging the subset of the A group and the subset of the B group alternately means performing the shift in the + y direction and the shift in the -y direction alternately by about the same number of times. As a result, even if the observer moves the gaze in one direction, the possibility that the gaze moving direction and the image shift direction coincide is halved, and even if their directions coincide, for example, the coinciding time exceeds three sub-frame periods. There is nothing continuous.
[377] The shape in the Fourier space of the shift pattern in FIG. 49 is shown in FIG. 42C. Compared with the local point of FIG. 42B, it can be seen that the local point of FIG. 42C is further dispersed. Therefore, in the present embodiment, the above phenomenon is less likely to occur at a specific eye movement speed.
[378] In the case where 60 frames of images are displayed in one second, when one frame is composed of three subframes, the period of one subframe is 1/180 seconds. Since one period of the shift pattern of the present embodiment is composed of 18 subframes, one period of the shift pattern is 1/180 seconds x 18 = 1/10 seconds. It was not possible to visually confirm the influence on the display by the shift pattern being repeated at 10 Hz. It is also possible to configure one cycle of the shift pattern with a number of subframes exceeding 18. However, if one cycle becomes too long, it is possible to visually check the periodic change of the shift pattern, which may cause deterioration of display quality. have. For this reason, it is preferable that one period of the shift pattern is composed of 18 or less subframes.
[379] According to the shift pattern of the subframe image used in this embodiment, one frame may be composed of two subframes or three subframes.
[380] An example of an image shift element that can be suitably used in this embodiment is shown in FIG.
[381] This image shift element is provided with the glass plate 22k which has transparent areas A-R. Transparent areas A, D, H, L, N and P are formed of FK5 glass having a refractive index of 1.49, and transparent areas B, F, I, K, O and R are formed of BaK4 glass having a refractive index of 1.57, and transparent area C , E, G, J, M and Q are formed of SF2 glass with a refractive index of 1.64. Each transparent region has a thickness of 2.0 mm.
[382] The disk-shaped glass plate 22k having such a configuration allows the main surface to form an angle of 65 ° with respect to the optical axis. Then, the glass plate 22k is rotated by synchronizing the timing at which each transparent region crosses the optical path with the timing for switching to the corresponding subframe. By doing so, the optical path is shifted by 34.0 µm in the transparent areas B, F, I, K, O and R with respect to the transparent areas A, D, H, L, N and P, and the transparent areas B, F, I, K The optical path shifts by 26.6 µm in the transparent regions C, E, G, J, M, and Q with respect to, O, and R.
[383] It is assumed that the transparent area A corresponds to, for example, the first subframe shown in FIG. In this case, the transparent area B corresponds to the next subframe, and the transparent area C also corresponds sequentially after the transparent area C. FIG.
[384] (Example 1 of Improvement of Image Shift Device)
[385] Next, an improvement example of the image shift element will be described.
[386] As described above, the image shift element having the liquid crystal layer is an image shift element that can be suitably employed in any of the image display panels of the line scanning method as well as the image display panel of the screen collective writing method. However, as long as the liquid crystal layer is provided, since the response characteristic (response speed) when voltage is applied to the liquid crystal is different at the time of voltage ON and OFF, the difference in the response speed affects the response characteristic of the image shift element. That is, a difference occurs in the shift direction due to the switching of the subframe image and the timing shift of the image shift, resulting in deterioration of image quality.
[387] When the front and rear of the liquid crystal layer are sandwiched by a polarizing plate of parallel Nicole, and the transmittance for voltage application is measured, there is a difference in the response speed of the liquid crystal layer at ON and OFF as shown in FIG. For this reason, when shifting a subframe image from one position on the projection surface to another position, the time required for changing the state of the liquid crystal is different between the case of changing from ON to OFF and the case of changing from OFF to ON. .
[388] Here, an example in which image shift is performed by arranging two image shift elements in series is considered. The case where the voltage applied to the liquid crystal layer on the light incidence side is turned from OFF to ON and the voltage applied to the liquid crystal layer on the light exit side is switched from ON to OFF is considered. In this case, the state change of the liquid crystal on the light exit side is later than the state change of the liquid crystal on the light incident side. As a result, at some point in time, even though the liquid crystal on the light incidence side has already changed to the ON state, a situation in which the liquid crystal on the light exit side has not yet changed from ON to OFF may occur. Fig. 52 schematically shows this situation. The arrow in Fig. 52 indicates the passage of time, and the combinations of "0N" and "OFF" in the figure indicate the state of the liquid crystal on the light incidence side (the lower part of the spherical shape) and the light exit side (the upper part of the spherical shape). Is showing how the transition. As shown in Fig. 52, there is a period in which both liquid crystals are turned ON due to the response characteristics of the liquid crystals. When both liquid crystals are temporarily turned on, only at that time, the image is temporarily displayed in double or triple phase, and there is a concern that the image quality is significantly degraded.
[389] Therefore, when two or more liquid crystal layers are used and three different positions are selected in the voltage application state for each liquid crystal layer, the image quality should not deteriorate even if a transition delay from ON to OFF occurs. It is necessary to drive the same shift element.
[390] Hereinafter, an improved method of driving the image shift element will be described so as not to cause the above problem.
[391] (Example 15)
[392] The image shift element of this embodiment is obtained by preparing two elements as shown in FIG. 32 (or FIG. 33) and arranging these two elements in series on an optical path as shown in FIG. In this embodiment, an image shift element is formed by using a crystal plate g3 and a crystal plate g4 having birefringence. According to this image shift element, three different positions on the projection surface can be selected according to the voltage application state to the two liquid crystal layers positioned on the light incidence side and the light exit side on the optical path. The three different positions to be selected are based on a combination of the voltage application state (ON / OFF) for the first liquid crystal layer (light incidence side) and the voltage application state (ON / OFF) for the second liquid crystal layer (light exit side). Is determined by
[393] Fig. 55 schematically shows the state change in the voltage application state to the liquid crystal layer on the light incident side and the light exit side. For example, there are two states depending on whether or not voltage is applied to the liquid crystal layer on the light incidence side, and the state is further subdivided according to the voltage application state from each state to the liquid crystal layer on the light exit side next. .
[394] Here, since the direction of the polarization plane of light entering the liquid crystal layer on the light exit side is changed by 90 ° in accordance with the state of voltage application on the light incident side, the voltage on the light exit side according to the voltage application state on the light incident side. The change in state relative to the state of authorization is exactly the opposite. Therefore, as the state change for the combination of the voltage application state on the light incidence side and the light exit side, two kinds of pairs can be considered as shown in FIG.
[395] In this specification, the said 2 types of combination shall be called "type A" and "type B", respectively. The positions of three different subframe images are represented by states A, B, and C. In addition, in order to express the voltage application state of two liquid crystals, the case where the voltage application state of the liquid crystal of light incident order is 0N and the voltage application state of the light exit side is OFF shall be described as "ON * OFF". .
[396] In this case, in type A, the state A becomes "OFF-ON", the state B in "OFF-OFF" or "ON-OFF", and the state C becomes "ON-ON". On the other hand, in the type B, the state A is changed from "OFF OFF" to the state B from "OFF ON" or "ON ON", and the state C is changed from "ON OFF". In addition, here, states A, B, and C may correspond to any of three different positions on a to-be-projected surface.
[397] Now, in case of type A, the change of state A-state B is performed, and in type B, the case where the change between states B-C is performed is considered. In type A, a transition occurs between state A defined by "OFF-ON" and state B prescribed by "ON-OFF". In addition, in type B, a transition will occur between the state B prescribed by "OFF * ON" and the state C prescribed by "ON * OFF".
[398] In this case, due to the response characteristics of the liquid crystal described with reference to Figs. 51 and 52, in the type A, both liquid crystal layers are temporarily energized in the process of changing the state A-state B ("ON" ON '' state). Similarly, in the type B, while the change between the states B ⇔ C is performed, there is a state in which both liquid crystal layers are temporarily energized (“ON ON” state). "0N 占 0N" defines state C in type A, and state B in type B, as indicated by the thick arrow in FIG. Therefore, in the type A, the subframe image of the state C other than the states A and B is temporarily displayed in the process of changing the state A-state B. This deteriorates the display quality. In contrast, in the type B, in the process of changing the state B ⇔ state C, a subframe image of the state B is temporarily displayed, but this is only a slight slow change in the state B ⇔ state C, The subframe picture is not displayed.
[399] In order to solve the above-mentioned problem in type A, when changing from state A to state B or from state B to state A, if state B is realized by "OFF / OFF", state C will occur transiently. Can be prevented.
[400] Next, consider the case of changing from state C to state B. In this case, a change from "ON ON" to "ON OFF" and a change from "ON ON" to "OFF OFF" may be considered. In consideration of the difference in response characteristics between the two liquid crystal layers, it is generally preferable to change only the voltage application state to one liquid crystal layer. It is preferable to select the change from "ON * ON" to "ON * OFF" by this. However, if the state B is realized by "ON-OFF", the above-described problem occurs when the state B transitions from the state B to the state A. Therefore, if it changes from state C to state B, and then changes to state A, it realizes state B by "OFF * OFF", and if it returns to state C after state B again, "ON" OFF ”to realize state B. As a result, image degradation in the transition process can be minimized.
[401] In the type B, when the state B is defined as "OFF-ON", in the process of changing from the state B to the state C or from the state C to the state B, as in the case of the type A, the "ON-ON" There is a condition. However, in the state of "ON * ON", as shown in Fig. 56, since the state B is realized, no deterioration in image quality as in the case of type A occurs. As a result, in the combination of type B, there is no deterioration in image quality due to the response characteristic difference in any of the transition processes.
[402] According to the image shift element shown in Fig. 53, the relationship between the crystal plate g3 having the birefringence on the light incidence side and the crystal plate g4 having the birefringence on the outgoing side is positive in birefringence and negative. Type A can be realized as long as it has a birefringence relationship. That is, as shown in Fig. 59, when the light beam shifting direction (left side in the drawing) and the light exiting side (right side in the drawing) are the same in the shift direction of the light beams, What is necessary is just a relationship in which the polarization direction of the shifted light beam differs 90 degrees. On the other hand, if the directions of the crystal plates g3 and g4 are matched on the light incidence side and the light outgoing side, Type B is realized. In this embodiment, the states A to C in Fig. 55 correspond to the shift positions of the upper and lower positions of the subframe image on the projection surface.
[403] (Example 16)
[404] The image shift element of this embodiment is obtained by preparing two elements shown in FIG. 36 and arranging these two elements as shown in FIG.
[405] This image shift element is similar to the image shift element of the fifteenth embodiment in that the image shift direction is determined in accordance with the ON / OFF application of voltage to each liquid crystal layer. 57 and 58, a characteristic point in this embodiment will be described.
[406] Fig. 57 schematically shows the state change in the voltage application state to the liquid crystal layer on the light incident side and the light exit side. For example, two states are taken by applying or not applying a voltage to the liquid crystal layer on the light incidence side, and the subdivided state is determined according to the voltage application state from each state to the liquid crystal layer on the light exit side.
[407] Here, as shown in FIG. 52, a change in the voltage application state of both liquid crystal layers is shown by a thick arrow in FIG. On the other hand, the "ON * 0N" state which temporarily occurs in the process of changing the voltage application state to both liquid crystal layers is shown by the thick arrow in FIG.
[408] As is apparent from Figs. 57 and 58, in the present embodiment, when the configuration of the type B is adopted, there is no combination of changes occurring temporarily in the process of state transition. In other words, by adopting the configuration of type B, it is possible to prevent a separate state from appearing in the transition process, thereby making it possible to prevent image quality deterioration.
[409] Next, the shift amount of the subframe image is examined. As described above, when the response speed of the display panel is slow, the timing shift may occur between the shift of the image and the switching of the display image. If such timing misalignment occurs, the image is displayed twice on the projected surface.
[410] According to the subset 1A shown in Fig. 43, since the images are sequentially shifted in the + y direction by one pixel, the images shifted in the + y direction by one pixel are slightly displayed according to the response difference. On the other hand, according to the subset 1B of Fig. 43, images shifted in the -y direction by one pixel are superimposed and displayed. That is, the blurring of the outline of the image occurs in an area of about one pixel.
[411] In contrast, since the subsets 2A, 2B, 3A, and 3B include image shifts of two pixels, the images shifted by two pixels are superimposed and displayed, respectively. As a result, blurring of the outline is observed in the area of two pixels. Even when two pixel image shifts occur between the subsets, similar blurring of outlines may occur.
[412] In order to suppress the blurring of the outline, it is preferable to reduce the amount of shift between the subframe images displayed in succession as much as possible. In addition, in order to solve the above-described problem caused by the eye movement direction and speed substantially coinciding with the shift direction and the shift speed of the subframe image, it is preferable to increase the number of shift positions included in one period of the shift pattern.
[413] Here, now, an image in which the luminance greatly changes every other pixel along the shift direction is considered. Such images include, for example, images including horizontal stripes, diagonal lines, cross hatches, and the like. When such an image is shifted by a plurality of shift amounts (for example, the shift amount for one pixel and the shift amount for two pixels), a difference occurs in the display quality as compared with the case where the image is always shifted by the shift amount for about one pixel. Fig. 60 shows a pattern in which the image is shifted. In the example of FIG. 60, the image is shifted by a plurality of shift amounts (shift amount for one pixel and shift amount for two pixels). In this way, when the image is shifted by two kinds of shift amounts, the repetition period of light and dark in any pixel of interest is not constant.
[414] Since the subframe image is switched to a frequency two times or more of the frame frequency of the video signal, if the contrast is repeated in a short period, the liquid crystal of the display device cannot sufficiently respond within the subframe period. On the contrary, if the bright or dark period is long over a plurality of subframe periods, the liquid crystal can sufficiently respond. As a result, when image shift occurs with a different shift amount, the brightness (darkness) of the pixel of interest varies depending on the subframe. Since the brightness change of the pixel caused by the difference in the shift amount is generated repeatedly in the period of the shift pattern, the observer feels as if the image is flickering.
[415] In contrast, Fig. 61 shows a pattern in which the image is always shifted by a shift amount of one pixel. According to the shift pattern shown in Fig. 61, the repetition of light and dark in any pixel of interest is constant. In this case, since the liquid crystal does not sufficiently respond within each subframe period, it is not sufficiently bright (dark). However, because the contrast is repeated regularly, no flickering feeling occurs.
[416] From the above considerations, it can be seen that maintaining the amount of one pixel shift to about one pixel brings about a desirable effect.
[417] An embodiment of executing a shift pattern suitable for obtaining a clear image will be described below.
[418] (Example 17)
[419] The projection image display device of the present embodiment basically has the same configuration as that of the first embodiment, and the main difference lies in that a shift pattern of a subframe image suitable for obtaining a clearer image is adopted. Therefore, below, only this difference is demonstrated.
[420] In the case of the first embodiment, as shown in Fig. 12, there are three subframe images constituting the n + 1th (n is positive integer) frame images, and the direction in which they are shifted. Is the same as the direction in which the subframe image constituting the nth frame image is shifted. However, in this embodiment, as in the thirteenth embodiment, the shift pattern of the subframe image is 1 by six subframe images. It becomes a cycle. In Example 13, one cycle of shift patterns was constructed by combining subsets 1A and 2B as shown in FIG. As a result, one period of this shift pattern includes two shifts of two pixels (two times in the + y direction and the -y direction).
[421] In contrast, in the present embodiment, the shift pattern shown in Fig. 62 is adopted. One period of this shift pattern is composed of a pattern in which six subframe images shift four positions on the immediately preceding one, and the size of each shift is only one pixel.
[422] The shift pattern shown in FIG. 62 is equivalent to the shift pattern of FIG. 44 in the corresponding Fourier space. Therefore, the spectral localization point of the shift pattern shown in FIG. 62 is the same as that shown in FIG. 42B. That is, according to this embodiment, the effect by Example 13 can be acquired. In addition, according to the present embodiment, the effect that the blurring of the contour can be halved from ± 2 pixels to ± 1 pixels is obtained. Further, even when one frame is divided into two or three subframes, the shift pattern shown in Fig. 62 can be employed.
[423] 63 shows an example of an image shift element for executing such a shift pattern. This image shift element is provided with the glass plate 22e which has transparent areas A-F. As the glass material, only inexpensive BK7 glass is used, and the transparent areas A have a thickness of 0.7 mm, the transparent areas B and F have a thickness of 1.4 mm, the transparent areas C and E have a thickness of 2.1 mm, and the transparent areas D have a thickness of 2.8 mm. It is formed. The refractive index of each transparent area is all 1.52.
[424] The disk-shaped glass plate 22e having such a configuration allows the main surface to form an angle of 83.8 ° with respect to the optical axis. Then, the glass plate 22e is rotated by synchronizing the timing at which each transparent region crosses the optical path with the timing for switching to the corresponding subframe. By doing so, the optical path is shifted by 26.0 μm in the transparent areas B and F with respect to the transparent area A, and the optical path is shifted by 26.0 μm in the transparent areas C and E with respect to the transparent areas B and F, In the transparent region D, the optical path is further shifted by 26.0 µm.
[425] It is assumed that the transparent area A corresponds to, for example, the first subframe shown in FIG. In this case, the transparent area B corresponds to the next subframe, and the transparent area C also corresponds sequentially after the transparent area C. FIG.
[426] Of course, there is no problem as the image shift element even if it is the image shift element described in another embodiment.
[427] Also in this embodiment, the pixel arrangement as shown in Fig. 46 is adopted as the pixel arrangement of the image display panel. Therefore, similarly to the thirteenth embodiment, even if the eye movement and the subframe image shift are substantially coincident with the pixel arrangement of the image display panel, the adverse effect on the image quality is reduced.
[428] Even in the projection image display apparatus of this embodiment, three sub-frame images are generated in each frame period using an image display panel without color filters, and are synthesized while optically shifting those images. Compared to the single-panel projection image display device, the light utilization rate is greatly improved, and three times the resolution can be realized. Of course, two sub-frame images may be generated in each frame period and synthesized while optically shifting those images. Although there is a slight awkward movement in the moving image, the switching rate of the subframe image is slowed by that much, so that the liquid crystal responds sufficiently and a state with better transmittance can be obtained. In addition, the blur of the outline of the image due to the timing shift occurring between the image shift and the switching of the subframe can be suppressed to the blur within one pixel.
[429] (Example 18)
[430] The projection image display apparatus of this embodiment also basically has the same configuration as that of the seventeenth embodiment, and the main difference lies in the shift pattern of the subframe image. Therefore, below, only this difference is demonstrated.
[431] In the seventeenth embodiment, as shown in FIG. 62, one period of the shift pattern of the subframe image is composed of six subframe images. In this embodiment, as shown in FIG. 63, the subframe One period of the shift pattern of the image is composed of 12 subframe images.
[432] The pattern in the Fourier space of the shift pattern in FIG. 63 is more dispersed than the shape in the Fourier space in the shift pattern in FIG. Therefore, in the present embodiment, compared with the seventeenth embodiment, the above phenomenon is less likely to occur at a specific eye movement speed.
[433] According to the shift pattern of the subframe image used in the present embodiment, since a pattern that is not shifted between subframes necessarily spans an even subframe to an odd subframe, one frame may consist of two subframes. It is also possible to configure three subframes.
[434] An example of an image shift element that can be suitably used in this embodiment is shown in FIG.
[435] This image shift element is provided with the glass plate 22k which has transparent areas A-L. Use only inexpensive BK7 glass as the glass material, and the transparent areas A and L have a thickness of 0.7 mm, the transparent areas B and B, D, I and K have a thickness of 1.4 mm, and the transparent areas C, E, H and J have a thickness. Is 2.1 mm, and the transparent areas F and G are 2.8 mm thick. The refractive index of each transparent area is all 1.52.
[436] The disk-shaped glass plate 22k having such a configuration allows the main surface to form an angle of 83.8 ° with respect to the optical axis. Then, the glass plate 22k is rotated by synchronizing the timing at which each transparent region crosses the optical path with the timing for switching to the corresponding subframe. By doing so, the optical path is shifted by 26.0 μm in the transparent areas B, D, I, and K with respect to the transparent areas A, L, and in the transparent areas C, E, H, and J with respect to the transparent areas B, D, I, and K. The optical path is shifted by 26.0 µm, and the optical path is shifted by 26.0 µm in the transparent regions F and G with respect to the transparent regions C, E, H and J.
[437] It is assumed that the transparent area A corresponds to, for example, the first subframe shown in FIG. In this case, the transparent area B corresponds to the next subframe, and the transparent area C also corresponds sequentially after the transparent area C. FIG.
[438] (Example 2 of Improvement of Image Shift Device)
[439] Next, another improvement example of an image shift element is demonstrated.
[440] As described above, the image shift element having the liquid crystal layer is an image shift element that can be suitably employed in any of the image display panels of the line scanning method as well as the image display panel of the screen collective writing method.
[441] In the case where the position of the subframe image is shifted in three places on the same straight line in the projection surface, as described above, two image shift elements are arranged directly on the optical axis, and the shift amount is made by each image shift element. It is good to match almost.
[442] On the other hand, when the position of the subframe image is shifted at four positions on the same straight line in the projection surface, the shift amounts by the two image shift elements may be set differently.
[443] Hereinafter, a driving method of such an image shift element will be described.
[444] (Example 19)
[445] The image shift element of the present embodiment can shift the position of the subframe image by one pixel at four positions on the same straight line in the projection surface, and is suitably used to realize the shift patterns shown in Figs. This image shift element is provided with two elements as shown in FIG. 32 (or 33), and these two elements are arranged in series on the optical path as shown in FIG. It is obtained by changing the amount.
[446] In this embodiment, since the image shift element is constituted by using the birefringent crystal plate g3 and the crystal plate g4, the image shift amount can be easily changed by changing the thickness of these crystal plates. According to this image shift element, four different positions on the projection surface can be selected according to the voltage application state to the two liquid crystal layers positioned on the light incidence side and the light exit side on the optical path. The four different positions to be selected are a combination of the voltage application state (ON / OFF) for the first liquid crystal layer (light incidence side) and the voltage application state (ON / OFF) for the second liquid crystal layer (light exit side). Is determined accordingly.
[447] The aspect of the shift in this case differs depending on whether the amount of image shift on the light incident side is large or small in comparison with the amount of image shift on the light exit side. The case where the image shift amount on the light incidence side is relatively large is shown in FIG. 65, and the case where the image shift amount on the light exit side is relatively large is shown in FIG. 65 and 66 schematically show the state change in the voltage application state to the liquid crystal layer on the light incident side and the light exit side. For example, there are two states depending on whether or not a voltage is applied to the liquid crystal layer on the light incidence side, and the state is further subdivided according to the voltage application state from each state to the liquid crystal layer on the light exit side next. do.
[448] Here, since the direction of the polarization plane of the light entering the liquid crystal layer on the light exit side changes by 90 ° according to the state of voltage application on the light incident side, the voltage application state on the light exit side depends on the voltage application state on the light incident side. The change in state is exactly the opposite. Therefore, as the state change with respect to the combination of the voltage application state on the light incidence side and the light outgoing side, two kinds of pairs are considered as shown in the upper and lower portions of Figs.
[449] Here, the above two types of combinations are referred to as "type A" and "type B", respectively. The positions of four different subframe images are represented by states A, B, C, and D. In addition, in order to express the voltage application state of two liquid crystals, the case where the voltage application state of the liquid crystal of light incident order is ON and the voltage application state of the light exit side is OFF shall be described as "ON * OFF". .
[450] In this case, in type A in Fig. 65, the state A becomes "OFF-ON", the state B in "OFF-OFF", the state C in "ON-OFF", and the state D in "ON-ON". On the other hand, in the type B, the state A is changed to "OFF-OFF", the state B is "OFF-ON", the state C is "ON-ON", and the state D is "ON-OFF". In addition, here, the states A, B, C, and D may correspond to any of four different positions on the immediately preceding side on the projection surface. The case in FIG. 66 can be considered similarly.
[451] Here, the state change from "ON-OFF" to "OFF-ON" or "OFF-ON" to "ON-OFF" is considered. In the example of Fig. 65, the state change from "ON-OFF" to "OFF-ON" or "OFF-ON" to "ON-OFF" corresponds to the change of state A-state C in type A. On the other hand, the state change corresponds to the change of state B-state D in type B. Similarly, in the case of the example of Fig. 66, the state change corresponds to the change of state A-state B in type A and to the change of state C-state D in type B.
[452] In view of the above, in the example of FIG. 65, it is understood that the shift of two pixels is performed by the state change from "ON * OFF" to "OFF * N" or "OFF * ON" to "ON * OFF". Can be. On the other hand, in the example of Fig. 66, the shift of one pixel is performed by the state change from "ON-OFF" to "OFF-ON" or "OFF-ON" to "ON-OFF".
[453] Since the image shift amount in the shift patterns of Figs. 62 and 64 is one pixel, in the configuration of Fig. 65, from "ON OFF" to "OFF 0N" and "OFF ON" from "ON OFF" State change does not occur. As a result, the problem caused by the response delay of the image shift element is avoided.
[454] In the case of employing the image shift element shown in Fig. 53, the relationship between the crystal plate g3 having the birefringence property on the light incidence side and the crystal plate g4 having the birefringence property on the outgoing side is positive birefringence and negative. Type A can be realized as long as the relationship has birefringence. That is, as shown in Fig. 59, when the light beam shifting direction (left side in the drawing) and the light exiting side (right side in the drawing) are the same in the shift direction of the light beams, What is necessary is just a relationship in which the polarization direction of the light beam shifted differs 90 degrees. On the other hand, if the directions of the crystal plates g3 and g4 are matched on the light incidence side and the light outgoing side, Type B is realized.
[455] When the thicknesses of the crystal plates g3 and g4 are set to 2: 1, the image shift amount of each image shift element is 2: 1. Then, the shift positions A, B, C, and D in Figs. 65 and 66 are equally spaced, so that a shift in one pixel pitch is possible.
[456] (Example 20)
[457] Similarly to the sixteenth embodiment, the image shift element of this embodiment is also obtained by preparing two elements shown in FIG. 36 and arranging these two elements as shown in FIG.
[458] This image shift element is similar to the image shift element of the fifteenth embodiment in that the image shift direction is determined in accordance with the ON / OFF application of voltage to each liquid crystal layer. 67 and 68, a characteristic point in this embodiment will be described.
[459] Fig. 67 schematically shows the state change in the voltage application state to the liquid crystal layer on the light incident side and the light exit side. For example, two states are taken depending on whether or not a voltage is applied to the liquid crystal layer on the light-incident side, and the state subdivided according to the voltage application state from each state to the liquid crystal layer on the light exit side is determined. do.
[460] Here also, the case where the state changes from "ON * OFF" to "OFF * ON" or "OFF * ON" to "ON * OFF" is considered. In the example of FIG. 67, in the type A, the change of the state B-state C occurs due to the state change from "ON-OFF" to "OFF-ON" or "OFF-ON" to "ON-OFF". In Type B, a change occurs in state A ⇔ state D. Similarly, in the example of Fig. 68, the state change causes a change in state B 'state C in type A and a change in state A-state D in type B.
[461] As described above, in the examples of FIGS. 67 and 68, the shift of one pixel in type A is changed from "ON OFF" to "OFF ON", or "OFF ON" to "ON OFF". Although it may occur, in the type B, a state change from "ON OFF" to "OFF ON" or "OFF ON" to "ON OFF" occurs only when shifting by three pixels is performed.
[462] In the case of employing the shift patterns of Figs. 62 and 64, since the pixel shift amount is one pixel, adopting the configuration of type B can prevent a separate state from appearing during the transition process, so as not to cause deterioration in image quality. It becomes possible.
[463] As mentioned above, various embodiments of the present invention have been described with reference to a projection type image display apparatus using a liquid crystal display element (LCD) as an image display panel, but the present invention is not limited thereto. The present invention is also applicable to a projection type image display apparatus using a display element other than a liquid crystal display element, for example, a DMD (digital micromirror device) or the like for an image display panel.
[464] The present invention is also applicable to a direct view type image display apparatus. In this case, an image display panel of a type that performs full color display by a color filter may be used. In the case of a normal direct view type that does not use an optical system for imaging, a projection surface such as a screen is unnecessary, but in the direct view type where the image is viewed through the eyepiece, the retina of the eye functions as the projection surface of the image.
[465] The present invention can also be applied to a direct view type or a projection type image display apparatus using a self-luminous image display element that does not require a light source as an image display panel.
[466] In addition, as an embodiment of the image shift element, an example of an element in which the optical path is periodically changed by the refractive member has been described. However, at least a part of the light source or the optical system may be moved to thereby change the optical path. For example, even if the projection lens 11 shown in Fig. 1 is vibrated, image shift is possible.
[467] (Example 21)
[468] In the system configuration of the projection image display apparatus in Example 11, three subframe memories each stored data relating to three kinds of colors. In the eleventh embodiment, even when each frame is composed of two subframes, three subframe memories are required because image data of three colors is always stored in the frame memory. In this embodiment, a system that can increase the use efficiency of the memory is adopted when each frame is composed of two subframes.
[469] An example of the configuration of a system of a projection image display apparatus according to the present invention will be described with reference to FIG.
[470] This embodiment also mainly includes a video signal processing circuit 100, an illumination optical system (light source, etc.) 102, an image display panel (liquid crystal display element) 104, an image shift element 106, an image shift element control circuit 108 ), And the projection lens 110.
[471] Since the illumination optical system 102, the image display panel 104, the image shift element 106, and the projection lens 110 have already been described, the image signal processing circuit 100 and the image shift element control will be described below. The relationship between each component centering on the circuit 108 is the same as that of the eleventh embodiment.
[472] The video signal processing circuit 100 in this embodiment includes an input signal selection circuit 120, an image demodulation circuit 122, a Y / C separation circuit 124, a scaling circuit 126, and a frame rate conversion circuit ( 128, a system control circuit 132, a color signal selection circuit 1340, and a frame memory circuit 1300.
[473] The system control circuit 132 controls the operations of the input signal selection circuit 120, the color signal selection circuit 1340, the frame memory 1300, and the image shift element control circuit 108.
[474] The image shift element control circuit 108 controls the operation of the image shift element 106 to synchronize with the display of the subframe image based on the signal output from the system control circuit 132.
[475] Since the main difference between the present embodiment and the eleventh embodiment lies in the configuration of the frame memory circuit 1300 and the color signal selection circuit 1340, this point will be described below.
[476] In this embodiment, the R signal, the G signal, and the B signal are stored in the frame memory circuit 1300 in the proper order by the color signal selection circuit 1340 shown in FIG. The image display panel 104 displays a subframe image based on the data sent out from the frame memory circuit 1300.
[477] Although the rate (frequency fin) of signal writing to the frame memory depends on the input signal, the rate (frequency fout) of signal reading from the frame memory is defined by the clock frequency of this system. The frequency fin is eg 60 hertz (Hz) and the frequency fout is eg 180 Hz.
[478] In response to the control signal output from the system control circuit 132, the R signal, the G signal, and the B signal are stored in the plurality of frame memories. At that time, each frame memory stores the data of the subframe image. For this reason, in this embodiment, when one frame is composed of two subframes, it is sufficient to have two frame memories, and three frame memories are unnecessary.
[479] The read rate of these signals is fout as described above, and the read operation from each frame memory is repeatedly executed two or three times in each frame period.
[480] In the eleventh embodiment, each color signal is stored in three frame memories in total, and then, by the color signal selection circuit 134, necessary signals are sequentially read from the three frame memories to generate respective subframe images. However, as described above, in the present embodiment, each color signal is mapped to the frame memory circuit 1300 by the color signal selection circuit 1340, and each subframe image is stored in the corresponding frame memory. The subframe image data stored in each frame memory is read out sequentially.
[481] As described above, when one frame is composed of two subframes, according to the eleventh method, all data of each frame is stored regardless of the number of subframes included in one frame. In total, three frame memories are required for each color signal. However, according to this embodiment, since the subframe image is directly mapped to the frame memory, only necessary data of the subframe image may be stored in the frame memory. As a result, when one frame consists of two subframes, there is an advantage that the number of frame memories or the memory capacity is two thirds of the eleventh embodiment.
[482] (Example 22)
[483] Next, a preferred shift direction of an image will be described, taking as an example an image shift element having at least one combination of a liquid crystal element and a birefringent element.
[484] In the case of a single-panel projection display using a microlens array as shown in Fig. 2, the angle of incidence in the pixel region differs for each color of RGB. For this reason, the angle of the light exiting from the display panel and incident on the birefringent element in the image shift element is also different for each RGB. The birefringent element has an optical axis inclined from the light incidence plane, and light incident perpendicularly to the light incidence plane is shifted in a direction parallel to the plane (major end face) including the optical axis and the incident light axis. In this case, the image shift direction is parallel to the main end surface of the birefringent element. However, when the incidence angle with respect to the incidence plane of the birefringent element differs for each RGB, the shift direction or the shift amount of light changes.
[485] First, consider a case where the color separation direction of RGB and the image shift direction coincide. In this case, since light of each color of RGB enters in parallel to the main end surface of the birefringent element, the shift direction of the light does not differ depending on RGB, but the shift amount changes. Since the difference in the shift amount is slight, it can be ignored.
[486] Next, consider a case where the color separation direction of RGB and the image shift direction do not coincide. In this case, the direction of the image shift is shifted for each RGB, and as a result, there arises a problem that the light of each color does not overlap at the same place. Therefore, it is preferable that the color separation direction of RGB and the image shift direction substantially match.
[487] As shown in Fig. 70, the normal display screen has a rectangular shape in which the short side S1 is in the vertical direction (y direction) and the long side S2 is in the horizontal direction (x direction). In this case, the scanning line moves along the short side direction y of the display screen. Therefore, when the color separation direction 700 of RGB coincides with the short side direction y of the display screen, the color separation direction 700 of RGB, that is, the image shift direction, coincides with the short side direction y of the screen. For this reason, there is an advantage that the dichroic mirror for color separation can be designed smaller.
[488] (Example 23)
[489] As shown in FIG. 71, when the TN liquid crystal 703 is inserted between the polarizing plate (polarizer) 701 and the polarizing plate (analyzer) 702 in a parallel Nicole arrangement state, and the voltage transmittance characteristic is measured, FIG. The result as shown is obtained. The term "transmittance" as used herein refers to the intensity ratio of linearly polarized light transmitted through the analyzer 702 with respect to the intensity of linearly polarized light incident on the liquid crystal 703.
[490] As can be seen from Fig. 72, even when no voltage is applied to the TN liquid crystal 703, light is slightly transmitted, and when the voltage of several volts is applied to the liquid crystal layer, the amount of light transmission is minimized. The leakage of light generated when no voltage is applied to the TN liquid crystal layer 703 occurs because the linearly polarized light incident on the TN liquid crystal 702 is slightly elliptically polarized due to residual linear light dispersion in the TN liquid crystal. When polarized light having an elliptical polarization component is incident on the birefringent element, the incident light is separated into normal light and abnormal light, so that the image is doubled and the resolution is lowered. This problem is not inherent to TN liquid crystals, but may occur in other liquid crystals.
[491] This embodiment is characterized in that a non-zero offset voltage is applied to the liquid crystal element even when the liquid crystal element is turned off in the image shift element.
[492] In addition, in this specification, when the voltage for polarization direction control is applied to the liquid crystal element, and as a result, the polarization plane of the light emitted from the liquid crystal element is rotated by about 90 degrees as compared with the case where no voltage is applied, the "liquid crystal element is in an ON state". It is said to be ". Then, a voltage sufficiently smaller than the magnitude (absolute value) of the voltage required to bring the liquid crystal element into the "ON state" is applied to the liquid crystal of the liquid crystal element, and as a result, the polarization plane of the emitted light obtained when the liquid crystal element is in the "ON state". When light having a polarization plane substantially orthogonal to is emitted from the liquid crystal element, the "liquid crystal element is in an OFF state".
[493] In each of the above-described embodiments, when the liquid crystal element was in the "OFF state", the magnitude of the voltage applied to the liquid crystal layer of the liquid crystal element was zero. In contrast, the present embodiment is characterized in that a voltage (offset voltage) having a non-zero value (for example, 2.5 volts) is applied even when the liquid crystal element in the image shift element is set to the "OFF state".
[494] 73, the preferable value of the offset voltage differs depending on the temperature of the liquid crystal. In the case of the projection display device, since light having high illuminance is incident on the image shift element, the temperature of the liquid crystal tends to rise. For this reason, even if the offset voltage optimized at room temperature is applied to a liquid crystal, elliptical polarization component will generate | occur | produce by the temperature rise of a liquid crystal. For this reason, it is preferable to measure the temperature of a liquid crystal element with a temperature sensor, and to control the magnitude | size of an offset voltage suitably according to the measured temperature.
[495] The preferred magnitude of the offset voltage also differs depending on the wavelength range of light, as shown in FIG. For this reason, it is preferable to set an offset voltage so that the value (alpha) regarding G light which belongs to the wavelength range which is the most sensitive to human vision is the smallest. However, the offset voltage may be set so that the difference between the respective values α is the smallest in the three primary colors of RGB.
[496] When the offset voltage changes depending on the temperature of the liquid crystal element, the value of the offset voltage may be zero, but in this specification, the applied voltage at this time is also referred to as "offset voltage".
[497] (Example 24)
[498] As described above, the birefringent element can separate incident light into normal light and abnormal light in the "main cross section" including the optical axis. Therefore, when the polarization direction of the light incident on the birefringent element is perpendicular to the main cross section, only the normal ray component is obtained. On the other hand, when the polarization direction of the light incident on the birefringent element is parallel to the main end surface, only the abnormal light component is obtained. When the polarization direction of the incident light is switched in the direction perpendicular or horizontal to the main end surface of the birefringent element using a liquid crystal element or the like, the incident light can be shifted in the main end surface of the birefringent element.
[499] The image shift element according to the ninth embodiment described above can shift the image in the screen vertical direction. This image shift element receives incident light having a polarization direction in the screen vertical direction or horizontal direction, and performs the shift operation of such incident light.
[500] However, depending on the display panel, the polarization direction of the light emitted from the panel may form 45 ° as well as the case of forming 0 ° or 90 ° with respect to the horizontal direction of the display screen. In particular, in the single plate method using the microlens array, since it is necessary to display a wide view in the color separation direction, it is preferable to set the polarization direction of the light emitted from the liquid crystal display element to 45 ° with respect to the horizontal direction of the display screen. Do.
[501] Even when the polarization direction of the light emitted from the display panel is inclined with respect to the horizontal direction of the screen, the image shift element may cause the image to be shifted in the vertical or horizontal direction of the screen. However, when the light inclined in the horizontal direction is incident on the image shift element shown in Fig. 32 or the like, light including both the normal light component and the abnormal light component is incident on the birefringent element in the image shift element. . As a result, there arises a problem that the incident light is separated into two.
[502] In order to solve this problem, the polarization direction of the light is rotated by a phase difference plate or the like until the light from the display panel is incident on the image shift element, and this polarization direction is directed to the surface containing the optical axis of the birefringent element. What is necessary is just to make it become 0 degree or 90 degree relationship.
[503] However, in the case where the polarization state is adjusted by the retardation plate, it is necessary to rotate the polarization direction in the same manner over the entire visible range or the entire specific wavelength range. According to the actual retardation plate, it is difficult to rotate the polarization direction equally over the entire visible region, and as the wavelength deviates from the center wavelength, it is elliptically polarized, and both the normal light component and the abnormal light component for the birefringent element Is incident. As a result, part of the light beam is shifted in an undesired direction and the image is doubled, so the resolution is lowered.
[504] In the image shift element of the present embodiment, in order to solve the above problems, a plurality of birefringent elements for shifting the image in the oblique direction are used in combination, thereby shifting the image in the screen vertical direction.
[505] See Figs. 75A to 75C. Light (linearly polarized light) having a polarization direction inclined with respect to the screen horizontal direction (or vertical direction) is emitted from the display panel 740 and is incident on the first element (first liquid crystal element) 741. The first liquid crystal element 741 switches between a state in which the polarization direction of incident light is rotated by 90 degrees and a state in which the polarization direction is not rotated, in accordance with the applied voltage.
[506] In this embodiment, two birefringent elements 742, 744 having optical axes parallel or perpendicular to the polarization plane of the light emitted from the liquid crystal element 741 are disposed, and the second liquid crystal element 743 is disposed between the two birefringent elements 742, 744. ) Is arranged. The second liquid crystal element 743 also switches between a state in which the polarization direction of incident light is rotated 90 degrees and a state in which the polarization direction is not rotated, in accordance with the applied voltage.
[507] In this embodiment, the main end surface (plane including both the optical axis and the optical axis of the incident beam) of the birefringent element (first birefringent element) 742 disposed at a position close to the first liquid crystal element 741, It has a relationship orthogonal to the main end surface of the birefringent element (second birefringent element) 744 disposed at a position relatively far from the first liquid crystal element 741. In other words, the optical axis of the first birefringent element 742 and the optical axis of the second birefringent element 744 are in a relationship of being rotated 90 degrees (or -90 degrees) around the optical axis of the incident light.
[508] The main cross section of the first birefringent element 742 forms an angle of θ ° with respect to a certain reference plane (here, the "horizontal plane"), and the main cross section of the second birefringent element θ '° (= It is assumed that an angle of θ ° + 90 °) is formed. Now consider the case where light in which the polarization direction is parallel to the main end face of the first birefringent element is incident on the birefringent element 742. In this case, the optical axis of the incident light is first shifted in the direction (θ direction) parallel to the optical axis of the first birefringent element 742. After the polarization direction is rotated by 90 ° by the second birefringent element 744, the polarization direction is shifted in a direction parallel to the optical axis of the second birefringent element 744 (θ 'direction).
[509] Here, the shift amount (movement distance) by the first birefringent element 742 is a, and the shift amount (movement distance) by the second birefringent element 744 is b. In this case, when the relationship between a and b satisfies tanθ = a / b, the final shift direction by the first and second birefringent elements 742 and 744 is perpendicular to the reference plane (= "horizontal plane") (screen Vertical direction). The image shift amount in the screen vertical direction at this time is equal to the parallel root of (a ² + b ² ). Further, the distances a and b each have a magnitude proportional to the thickness of the first birefringent element 742 and the thickness of the second birefringent element 744.
[510] In the above embodiment, when θ ° is 45 °, θ 'becomes 135 °. At this time, since the relationship of tan45 ° = a / b = 1 may be satisfied, the first and second birefringent elements can be manufactured using two birefringent plates of the same thickness made of the same material.
[511] In addition to the liquid crystal of the TN mode, a vertical alignment mode liquid crystal, an OCB mode liquid crystal, a ferroelectric liquid crystal, or the like can be used for the first element.
[512] In the display panel 740, pixels of the same color (for example, pixels of R color) may be arranged in a direction inclined with respect to the screen horizontal direction. In this case, the image shift direction should match the direction perpendicular to the same pixel column. This image shift is performed by stacking two birefringent plates of the same thickness made of the same material, matching the directions of their optical axes (θ = θ '), arranging the directions of the same color pixel columns and the θ direction to be orthogonal to each other. It is not necessary to switch the polarization direction by the liquid crystal element. In this case, one birefringent element may be used, and the structure which removed the 2nd liquid crystal element 743 may be employ | adopted.
[513] In the image display apparatus of the present invention, the light from the light source is divided into luminous fluxes of three primary colors, for example, R, G, and B, and the luminous flux of each color is incident on the corresponding pixel region of the image display panel, whereby R in each pixel region. , G, and B are modulated. Then, by sequentially switching the optical path of the light emitted from the image display panel to time division, the display image is sequentially switched in correspondence thereto, whereby a high resolution color image display can be realized while increasing the utilization of light.

权利要求:
Claims (60)
[1" claim-type="Currently amended] Light Source,
An image display panel each having a plurality of pixel areas capable of modulating light,
Light control means for condensing light from the light source to a corresponding pixel region of the plurality of pixel regions according to a wavelength range;
A projection image display apparatus having an optical system for forming an image on a projection surface by light modulated by the image display panel,
A circuit which generates data of a plurality of subframe images from data of each frame image constituting the image, and displays the plurality of subframe images by time division by the image display panel; and
An image shift element for shifting a selected subframe image among the plurality of subframe images displayed by the image display panel on the projected surface,
And a projection type image display device that sequentially irradiates the same area on the projected surface by light belonging to different wavelength ranges modulated in different pixel areas of the image display panel.
[2" claim-type="Currently amended] The projection type image display apparatus according to claim 1, wherein the display of the subframe is switched by writing the surface of the image display panel, and the shift operation by the image shift element is performed in synchronization with the switching.
[3" claim-type="Currently amended] The projection type image display apparatus according to claim 1, wherein the display of the subframe is switched by prescan of the image display panel, and the shift operation by the image shift element is performed in synchronization with the switching.
[4" claim-type="Currently amended] The projection type image display apparatus according to claim 3, wherein the shift direction of the subframe on the projected surface is the same as the scanning direction of the image display panel.
[5" claim-type="Currently amended] The projection type image display apparatus according to claim 3, wherein the shift direction of the subframe on the projected surface does not coincide with the scanning direction of the image display panel.
[6" claim-type="Currently amended] 4. The projection image display apparatus according to claim 3, wherein a speed at which a display area of the subframe image increases and a speed at which a shift area by the image shift element increases on the projected surface.
[7" claim-type="Currently amended] The projection image display apparatus according to any one of claims 3 to 6, wherein the time interval between the start of scanning and the start of optical path shift by the image shift element is variable for each row of the pixel region.
[8" claim-type="Currently amended] The projection type image display apparatus according to any one of claims 3 to 6, wherein the time interval between the start of scanning and the start of optical path shift by said image shift element is preset for each row of said pixel region. .
[9" claim-type="Currently amended] 9. The projection image display apparatus according to claim 8, wherein the start of the optical path shift by the image shift element is delayed for each row of the pixel region rather than the start of scanning.
[10" claim-type="Currently amended] The direction of shifting the subframe image constituting the n + 1th (n is a positive integer) frame image on the projected surface according to claim 1, wherein the direction of shifting the nth frame image. And a projection image display device which is the same as the direction in which the subframe image to be constructed is shifted on the projected surface.
[11" claim-type="Currently amended] The direction of shifting the subframe image constituting the n + 1th (n is a positive integer) frame image on the projected surface according to claim 1, wherein the direction of shifting the nth frame image. Opposite to the direction of shifting the constituting subframe image on the projected surface,
The first subframe image of the nth + 1th frame image is not shifted with respect to the last subframe image of the nth frame image.
[12" claim-type="Currently amended] The projection type image display apparatus according to claim 1, wherein the number of subframe images constituting each frame image is two, and each subframe image is sequentially displayed at two different positions on the projected surface.
[13" claim-type="Currently amended] The method of claim 1, wherein the number of subframe images constituting each frame image is two,
Each subframe image is displayed in sequence at three different positions on the projected surface,
And the period of the shift of the subframe image is 1.5 times the frame period.
[14" claim-type="Currently amended] The method according to claim 1, wherein the number of subframe images constituting each frame image is four or more,
Each subframe image is displayed in sequence at three different positions on the projected surface,
And at least two subframe images of the four or more subframe images constituting each frame image are displayed at the same position on the projected surface.
[15" claim-type="Currently amended] 7. The projection image display apparatus according to claim 6, wherein the at least two subframe images displayed at the same position on the projected surface include subframe images of black display.
[16" claim-type="Currently amended] 7. The projection image display apparatus according to claim 6, wherein the at least two subframe images displayed at the same position on the projected surface include subframe images with reduced luminance.
[17" claim-type="Currently amended] The projection type image display apparatus according to claim 1, wherein the movement pattern of the subframe image shifted on the projection surface has a periodicity, and one cycle of the movement pattern includes movement of approximately two pixel pitches at least twice. .
[18" claim-type="Currently amended] 10. The method of claim 9, wherein one period of the motion pattern of the subframe image is composed of a combination of an even number of subsets selected from six kinds of subsets defined by movement of three subframe images, each of which is sequentially displayed. There is,
The six kinds of subsets belong to any of two groups symmetrical with respect to the moving direction.
[19" claim-type="Currently amended] 19. The projection image display apparatus according to claim 18, wherein one period of the movement pattern of the subframe image alternately includes a subset selected from each of the two groups.
[20" claim-type="Currently amended] 19. The apparatus of claim 18, wherein one period of the motion pattern of the subframe image is composed of 18 subframe images which are sequentially displayed.
And a six subset selected from each of the two groups in turn.
[21" claim-type="Currently amended] 19. The method of claim 18, wherein one period of the motion pattern of the subframe image is composed of movement of six subframe images sequentially displayed.
And two subsets selected one from each of the two groups.
[22" claim-type="Currently amended] The motion pattern of the subframe image shifted on the projection surface has a periodicity,
And the movement pattern comprises shifting the subframe image to four or more different positions on the same straight line.
[23" claim-type="Currently amended] 23. The projection image display apparatus according to claim 22, wherein the shift amount between successive subframe images is not more than about twice the pixel pitch measured along the direction of the shift on the projection surface.
[24" claim-type="Currently amended] 24. The method of claim 22, wherein one period of the motion pattern of the subframe image is composed of 12 subframe images sequentially displayed.
A projection type image display apparatus in which the shift amount between successive subframe images is not more than about twice the pixel pitch measured along the direction of the shift on the projection surface.
[25" claim-type="Currently amended] 23. The apparatus of claim 22, wherein one period of the motion pattern of the subframe image is composed of six subframe images sequentially displayed.
A projection type image display apparatus in which the shift amount between successive subframe images is not more than about twice the pixel pitch measured along the direction of the shift on the projection surface.
[26" claim-type="Currently amended] The shift amount of the subframe on the projection surface is about an integer multiple of the pixel pitch measured along the direction of the shift on the projection surface. Projection type image display device.
[27" claim-type="Currently amended] The light modulated surface according to any one of claims 1 to 25, wherein the light modulated by the image display panel is changed when the subframe image displayed by the image display panel is switched to the next subframe. Projection type image display device for blocking the light so as not to reach.
[28" claim-type="Currently amended] The light control means according to claim 1, wherein the light control means directs the light from the light source in different directions included in the same plane according to the wavelength band,
And the image shift element shifts the subframe image in a direction parallel to the plane.
[29" claim-type="Currently amended] 29. The projection image display apparatus according to claim 28, wherein a shift direction of the subframe image by the image shift element coincides with a short side direction of a display screen in the image display panel.
[30" claim-type="Currently amended] An image display apparatus comprising an image display panel having a plurality of pixel regions each of which can modulate light, wherein the image display apparatus forms an image by light modulated by the image display panel.
A circuit which generates data of a plurality of subframe images from data of frame images constituting the image, and displays the plurality of subframe images by time division by the image display panel; and
An image shift element for shifting an optical path of a selected subframe image among the plurality of subframe images displayed by the image display panel,
Light belonging to different wavelength ranges modulated by different pixel regions of the image display panel is synthesized by shifting the subframe,
The circuit comprises a first storage area for storing data relating to a first color constituting the frame image, a second storage area for storing data relating to a second color constituting the frame image, and the frame image. A third storage area for storing data relating to the third color
And each data of the plurality of subframes is generated by selectively combining data read out from each of the first storage area, the second storage area, and the third storage area in a predetermined order.
[31" claim-type="Currently amended] An image display apparatus comprising an image display panel having a plurality of pixel regions each of which can modulate light, wherein the image display apparatus forms an image by light modulated by the image display panel.
A circuit which generates data of a plurality of subframe images from data of frame images constituting the image, and displays the plurality of subframe images by time division by the image display panel; and
An image shift element for shifting an optical path of a selected subframe image among the plurality of subframe images displayed by the image display panel,
Light belonging to different wavelength ranges modulated by different pixel regions of the image display panel is synthesized by shifting the subframe,
The circuit includes a plurality of storage areas for storing data of the plurality of subframe images.
The plurality of storage areas include data relating to a first color constituting the frame image, data relating to a second color constituting the frame image, and data relating to a third color constituting the frame image. An image display apparatus.
[32" claim-type="Currently amended] And an image display panel having a light modulator in which a first color pixel area belonging to a first wavelength range, a second color pixel area belonging to a second wavelength band, and a third color pixel area belonging to a third wavelength band are periodically arranged. In one image display apparatus,
And an image shift element capable of periodically shifting the optical path of the light modulated by the optical modulator,
The color of the first pixel on a virtual plane across the optical path includes light modulated in the first color pixel region in a first period, light modulated in the second color pixel region in a second period, and Defined by light modulated in the third color pixel region in three periods,
The color of the second pixel adjacent to the first pixel on the virtual plane is light modulated in the pixel region for the second color in the first period, and light modulated in the pixel region for the third color in the second period. And by light modulated in the pixel region for the first color in the third period,
The color of the third pixel adjacent to the second pixel on the virtual surface is light modulated in the third color pixel area in the first period, and light modulated in the pixel area for the first color in the second period. And light modulated by the second color pixel region in the third period.
[33" claim-type="Currently amended] A first storage area storing data relating to a first color constituting a frame image displayed by an image display apparatus having an image display panel, and a second storage area storing data relating to a second color constituting the frame image And a third storage area for storing data relating to a third color constituting the frame image,
A circuit device for generating respective data of a plurality of subframes to be time-divisionally displayed by combining data read out from each of the first storage area, the second storage area, and the third storage area in a predetermined order.
[34" claim-type="Currently amended] 34. The apparatus according to claim 33, wherein the data relating to the first color, the data relating to the second color, and the data relating to the third color for any pixel constituting the image are assigned to each of the plurality of subframe images. Circuitry made.
[35" claim-type="Currently amended] 35. The method according to claim 33 or 34, wherein by shifting a selected subframe image of the plurality of subframe images on a certain surface, the same image on the surface by light belonging to different wavelength ranges modulated in different pixel regions of the image display panel. Circuit device capable of sequentially irradiating areas
[36" claim-type="Currently amended] Data relating to a first color constituting a frame image displayed by an image display apparatus having an image display panel, data relating to a second color constituting the frame image, and data relating to a third color constituting the frame image. In a circuit device having a plurality of storage areas for storing a plurality of subframes composed of
The data relating to the first color, the data relating to the second color, and the data relating to the third color are written in the plurality of storage areas in a preset order;
A circuit device for generating respective data of a plurality of subframe images to be time-divisionally displayed by sequentially reading data of each storage area.
[37" claim-type="Currently amended] By periodically shifting the optical path of the subframe image modulated by the image display panel, the subframe image can be selectively changed into three or more positions separated by one pixel pitch or more on the same straight line in a plane. In the image shift element,
A refraction member for shifting the optical path by refraction, and
And a driving device for periodically changing the relative positional relationship of the refractive member with respect to the optical path,
And said refractive member is composed of a plurality of regions having different shift amounts of the optical path.
[38" claim-type="Currently amended] The said refractive member is comprised from the rotating plate which has a some transparent area | region which differs in at least one of refractive index and thickness, and is rotatably supported by the arrangement which inclines and crosses the said optical path,
And the driving device rotates the rotating plate such that a plurality of transparent regions of the rotating plate sequentially cross the optical path.
[39" claim-type="Currently amended] The said refractive member is comprised from the transparent board which has a some transparent area | region which differs in at least one of refractive index and thickness, and is supported by the arrangement | positioning which traverses the said optical path so as to be movable,
And the driving device moves the transparent plate so that a plurality of transparent regions of the transparent plate sequentially cross the optical path.
[40" claim-type="Currently amended] By periodically shifting the optical path of the subframe image modulated by the image display panel, it is possible to selectively change the subframe image into three or more positions separated by one pixel pitch or more on the same straight line in a plane. In the image sheet device,
A first element for modulating the polarization direction of the subframe image modulated by the image display panel, and a second element having a different refractive index in accordance with the polarization direction of the light,
Having at least two sets of the first element and the second element, and arranged to be arranged in series on the optical path,
When shifting the subframe image to an adjacent position among the three or more positions, the selection of the voltage application state for the first element arranged on the light incident side is dependent on the direction in which the subframe image is then shifted. An image shift element characterized by being different.
[41" claim-type="Currently amended] By periodically shifting the optical path of the subframe image modulated by the image display panel, it is possible to selectively change the subframe image into three or more positions separated by one pixel pitch or more on the same straight line in a plane. In the image shift element,
A first element for modulating the polarization direction of the subframe image modulated by the image display panel, and a second element having a different refractive index in accordance with the polarization direction of the light,
Having at least two sets of the first element and the second element, and arranged to be arranged in series on the optical path,
When the subframe image is shifted to the position of the center portion among the three or more positions, the state of applying voltage to the first element disposed on the light incidence side is determined by applying the voltage to the first element disposed on the light exit side. An image shift element characterized by the same as the state.
[42" claim-type="Currently amended] By periodically shifting the optical path of the subframe image modulated by the image display panel, it is possible to selectively change the subframe image into three or more positions separated by one pixel pitch or more on the same straight line in a plane. In the image shift element,
A first image shift portion and a second image shift portion disposed on the optical path,
The first and second image shift portions each have a first element for modulating the polarization direction of the subframe image modulated by the image display panel, and a second element having a different refractive index in accordance with the polarization direction of light,
And a shift amount of the subframe image by the first image shift element and a shift amount of the subframe image by the second image shift element are different from each other.
[43" claim-type="Currently amended] 43. The shift amount of the subframe image by the image shift portion located on the side where light first enters on the optical path is determined by the image shift portion located on the side where light subsequently enters on the optical path. An image shift element which is twice the shift amount of a subframe image.
[44" claim-type="Currently amended] 44. The image shift element according to claim 42 or 43, wherein the combination of the applied voltages for driving the plurality of elements does not include a transition from ON to OFF and a transition from OFF to ON at the same time.
[45" claim-type="Currently amended] An image in which the optical path of the subframe image modulated by the image display panel is periodically shifted, whereby the subframe image can be selectively changed into a plurality of positions separated by one pixel pitch or more on the same straight line in a plane. In the shift element,
A first element for modulating the polarization direction of the subframe image modulated by the image display panel, and a second element having a different refractive index in accordance with the polarization direction of the light,
The first device includes a liquid crystal device that can switch the polarization state of light in response to the application of voltage,
The second element includes an optical birefringent element for shifting the optical axis position in accordance with the polarization state of the light,
An image shift element, wherein the voltages of plural levels applied to the liquid crystal element in order to switch the polarization state of the light all have non-zero values.
[46" claim-type="Currently amended] The liquid crystal device of claim 45, wherein the liquid crystal element emits first polarized light when a first voltage included in the voltages of the plurality of levels is applied, and when a second voltage included in the voltages of the plurality of levels is applied, The image shift element which emits the 2nd polarization which the polarization plane rotated substantially 90 degrees with respect to 1st polarization.
[47" claim-type="Currently amended] 47. The image shift element according to claim 46, wherein said first voltage has an offset value controlled in accordance with a temperature of said liquid crystal element.
[48" claim-type="Currently amended] 48. The image shift element according to claim 46 or 47, wherein the first voltage has an offset value set based on a voltage transmittance characteristic of visible light passing through the liquid crystal element.
[49" claim-type="Currently amended] 48. The image shift element according to claim 46 or 47, wherein the first voltage has an offset value set based on a voltage transmittance characteristic of green light passing through the liquid crystal element.
[50" claim-type="Currently amended] The said 1st voltage has an offset value optimized based on the voltage transmittance characteristic of red light which passed through the said liquid crystal element, the voltage transmittance characteristic of green light, and the voltage transmittance characteristic of blue light, Image shift element.
[51" claim-type="Currently amended] An image in which the optical path of the subframe image modulated by the image display panel is periodically shifted, whereby the subframe image can be selectively changed into a plurality of positions separated by one pixel pitch or more on the same straight line in a plane. In the shift element,
A first element for modulating the polarization direction of the subframe image modulated by the image display panel, and a second element having a different refractive index in accordance with the polarization direction of the light,
The first element has a first polarization modulator and a second polarization modulator, and the second element has a first birefringent element and a second birefringent element,
The first polarization modulator emits normal or abnormal light with respect to the first birefringent element,
The second polarization modulator emits normal light or abnormal light with respect to the second birefringent element,
The first birefringent element shifts the image by a distance a in the direction of θ ° with respect to a certain reference plane including the optical path,
The second birefringent element shifts the image by a distance b in the direction of θ '° with respect to the reference plane,
An image shift element with a relationship of tan θ = a / b.
[52" claim-type="Currently amended] The image shift element according to claim 51, wherein a relationship of θ '° = θ ° + 90 ° is established.
[53" claim-type="Currently amended] The image shift element according to claim 51, wherein a relationship of θ '° = θ ° is established.
[54" claim-type="Currently amended] 54. The image shift element according to claim 52 or 53 wherein θ is 45.
[55" claim-type="Currently amended] By periodically shifting the optical path of the subframe image modulated by the image display panel, it is possible to selectively change the subframe image into three or more positions separated by one pixel pitch or more on the same straight line in a plane. In the image shift element,
A liquid crystal layer exhibiting at least two different refractive indices with respect to the polarized light, and
It has two board | substrates which clamp the said liquid crystal layer,
An image shift element in which a microprism or a diffraction grating is formed on a liquid crystal side surface of one of the two substrates.
[56" claim-type="Currently amended] The image shift element according to claim 55, wherein the microprism or diffraction grating is formed of a material having a refractive index substantially the same as the refractive index of at least one of the two or more refractive indices.
[57" claim-type="Currently amended] 56. The apparatus of claim 55, further comprising at least two sets of said liquid crystal layer and said two substrates, said sets being arranged in series on said optical path,
And the subframe image is shifted only by selecting voltage applied to the image shift element arranged on the light output side when the subframe image is shifted to an adjacent position among the three or more positions.
[58" claim-type="Currently amended] At least two sets of image shift elements arranged in series on an optical path,
Each set of image shift elements includes two displacement elements,
Each displacement element has a liquid crystal layer exhibiting two or more different refractive indices with respect to polarized light, and two substrates which hold | maintain the said liquid crystal layer, and the microprism or diffraction is carried out on the liquid crystal side surface of any one board | substrate of the said two substrates. A grid is formed,
The refractive angles of the microprisms or diffraction gratings formed on the substrate included in the same bath are the same,
The angle of refraction by the microprism or diffraction grating formed on the substrate included in the jaw positioned on the side where light first enters on the optical path is the microprism or diffraction formed on the substrate of the jaw located on the side where light enters later on the optical path. An image shift element having twice the refraction angle by the lattice.
[59" claim-type="Currently amended] At least two sets of image shift elements arranged in series on an optical path,
Each set of image shift elements includes two displacement elements,
Each displacement element has a liquid crystal layer exhibiting two or more different refractive indices with respect to polarized light, and two substrates which hold | maintain the said liquid crystal layer, and the microprism or diffraction is carried out on the liquid crystal side surface of any one board | substrate of the said two substrates. A grid is formed,
The refractive angles of the microprisms or diffraction gratings formed on the substrate included in the same bath are the same,
And the distance of the substrate included in the jaw positioned on the side where light first enters on the optical path is twice the distance of the substrate of the jaw positioned on the side where light enters later on the optical path.
[60" claim-type="Currently amended] An image in which the optical path of the subframe image modulated by the image display panel is periodically shifted, whereby the subframe image can be selectively changed into four positions separated by one pixel pitch or more on the same straight line in a plane. In the shift element,
Having a first shift element and a second shift element arranged in series on the optical path,
And the shift amount of the subframe image by the first shift element is set to twice the shift amount of the subframe image by the first shift element.

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同族专利:

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公开号 | 公开日

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CN1449505A|2003-10-15|

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WO2001096932A1|2001-12-20|

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KR100533611B1|2005-12-05|

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US20030090597A1|2003-05-15|

---

DE60125183T2|2007-10-11|

---

EP1306712A1|2003-05-02|

---

DE60125183D1|2007-01-25|

---

EP1306712B1|2006-12-13|

---

US7202917B2|2007-04-10|

---

CN100417230C|2008-09-03|

---

EP1306712A4|2005-05-04|

引用文献:

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公开号 | 申请日 | 公开日 | 申请人 | 专利标题

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法律状态:
2000-06-16|Priority to JPJP-P-2000-00181223

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2000-06-16|Priority to JPJP-P-2000-00181302

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2000-06-16|Priority to JPJP-P-2000-00181290

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2000-06-16|Priority to JP2000181223

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2000-06-16|Priority to JP2000181302A

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2000-06-16|Priority to JP2000181290A

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2000-11-17|Priority to JPJP-P-2000-00351635

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2000-11-17|Priority to JP2000351635

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2001-03-05|Priority to JP2001059644

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2001-03-05|Priority to JPJP-P-2001-00059644

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2001-05-30|Priority to JPJP-P-2001-00163301

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2001-05-30|Priority to JP2001163301A

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2001-06-13|Application filed by 샤프 가부시키가이샤

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2001-06-13|Priority to PCT/JP2001/005041

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2003-02-05|Publication of KR20030010731A

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2005-12-05|Application granted

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2005-12-05|Publication of KR100533611B1

优先权:

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申请号 | 申请日 | 专利标题

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JPJP-P-2000-00181290|2000-06-16|

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JP2000181223|2000-06-16|

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JP2000181302A|JP3722205B2|2000-06-16|2000-06-16|Projection-type image display device|

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JP2000181290A|JP3722204B2|2000-06-16|2000-06-16|Projection-type image display device|

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JPJP-P-2000-00181223|2000-06-16|

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JPJP-P-2000-00181302|2000-06-16|

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JPJP-P-2000-00351635|2000-11-17|

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JP2000351635|2000-11-17|

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JP2001059644|2001-03-05|

---

JPJP-P-2001-00059644|2001-03-05|

---

JPJP-P-2001-00163301|2001-05-30|

---

JP2001163301A|JP3784279B2|2000-06-16|2001-05-30|Projection-type image display device|

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PCT/JP2001/005041|WO2001096932A1|2000-06-16|2001-06-13|Projection type image display device|