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  • 专利说明
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    • 专利摘要:
    The present invention relates to an inspection method and system, the inspection system comprising a camera (330) comprising multiple pixels having a pixel width; a mechanical stage (310), for the introduction of a movement between an inspected object (300) and an optic (320) of the inspection system; the inspected object (300) being expected to move a distance which is substantially equal to the pixel width during a period of pixel movement; an illumination module (317) and an optic (320) for illuminating inspected portions of the inspected object (300) and directing light from the inspected portions to the camera (330); and the camera (330) being arranged to acquire multiple acquired images of the inspected portions during each period of pixel movement, at least two acquired images partially overlapping.
    公开号:BE1019646A3
    申请号:E2010/0621
    申请日:2010-10-20
    公开日:2012-09-04
    发明作者:Shalem Tal；Shapirov Diaha
    申请人:Camtek Ltd；
    IPC主号:
    专利说明:

    INSPECTION SYSTEM AND METHOD FOR HIGH SPEED IMAGING
    In the field of automatic optical inspection of printed circuit boards (PCBs), wafers and other electronic workpieces (as well as possibly other optical inspection systems), linear scanning techniques are commonly used.
    A conventional linear scanning apparatus comprises a line scan camera, an acquisition card, a processor (eg a personal computer (PC), which may include additional components such as a monitor, etc.), an optical, an illuminating device, an object moving plate, and a hardware motion control unit.
    The two-dimensional image formation by linear scanning is based on a scanned object movement. The camera clock and, therefore, the camera line reading period, are synchronized with the pixel size equivalent moving object position, which in turn is governed by the programmable motion control signal (PEG). ) from a location encoder. The exposure period can be either fixed or programmable (externally or internally). The essence of the classical approach is that the single PEG corresponds to the single camera reading, namely the single linear sampling, and therefore, the single image acquisition, for example as shown in FIG. 1.
    Fig. 1 is a timing chart showing three images 20, 22 and 24 which are obtained during three different camera clock cycles 10, 12 and 14 - each camera clock cycle is slightly longer than a period camera exposure. The images are read from the camera in a pipelined manner - the images obtained during the i th camera exposure period are emitted during the (i + 1) th camera exposure period. Figure 1 also shows three PEG signal pulses denoted PEG (i-1), PEG (i) and PEG (i + 1).
    These non-superimposed images form a two-dimensional image of the inspected object.
    The longitudinal axis of the camera is referred to as the camera direction or X axis, while the scanning direction is referred to as the Y axis.
    PEG signals can be generated in fixed time intervals or after the inspected object has moved a fixed distance.
    The main features of the conventional image acquisition approaches mentioned above are: (i) Geometric resolution. The camera direction resolution (X axis) is defined by the pixel size of the camera and the optical magnification provided by the optics. The scan direction resolution (Y axis) is defined by the camera line period which is fully synchronized with the PEG signals generated by the moving object encoder.
    (ii) Image quality. X-axis sharpness (X-MTF) is significantly influenced by the playback and sampling camera noise. Y-axis sharpness (Y-MTF) is mainly determined by the ratio of line periods to exposure.
    (iii) The gray level signal of the raw image is determined by the camera sensitivity and the selected exposure period (given the constant conditions of reflectance / transmittance and object illumination).
    (iv) Information Dimension: A single line provides unique dimension information per pixel of obj and.
    The acquisition technique described above has (i) a significant impact of digital sampling noise, especially at high spatial frequency; (ii) a modulation transfer function (MTF) significantly lowered at the high spatial frequency; and (iii) a comparatively low signal-to-noise ratio under low illumination conditions due to significant separation of read noise.
    There is therefore a need for systems and methods that would improve the image quality without changing a geometric resolution and / or a scan rate. An improvement is desired, among others, in the following parameters:
    Image sharpness, visualization of tiny defects, signal-to-noise ratio under low illumination conditions and image stability.
    According to one embodiment, the invention relates to an inspection system. The inspection system may include a camera; a mechanical stage, for introducing a movement between an inspected object and an optical inspection system; the inspected object being expected to move a distance that is substantially equal to a pixel width during a pixel motion period; an illumination module and an optic for illuminating inspected portions of the inspected object and for directing a light from the inspected portions to the camera; and the camera being arranged to acquire multiple acquired images of the inspected portions during each pixel motion period, at least two acquired images partially overlapping one another.
    The inspection system may include an image processing unit for processing the acquired images to provide processed images; and a fault detection unit for detecting defects based on processed image processing.
    The image processing unit can merge different acquired images obtained during a single period of pixel motion.
    The image processing unit can generate multiple processed images, each processed image comprising acquired images obtained during different pixel motion periods, each of the acquired images being obtained at the same time difference from a start of the period of pixel motion during which the acquired image was obtained.
    The illumination module may be arranged to perform at least one modification of at least one illumination characteristic during each pixel motion period.
    The illumination module may be arranged to illuminate, during a single period of pixel motion, different parts of objects inspected by light beams which differ from one another by the wavelength.
    The inspection system may further be capable of illuminating, during a single period of pixel motion, different parts of objects inspected by light beams which differ from each other by an angle of incidence.
    The illumination module may be arranged to illuminate, during a single period of pixel motion, different parts of objects inspected by light beams which differ from each other by the wavelength and angle of the light. impact.
    The camera may be arranged to obtain at least three acquired images of the inspected portions during each pixel motion period.
    The mechanical stage can be arranged to move the inspected object by a movement which is characterized by speed variations; and the inspection system may further comprise: a signal generator, for generating trigger pulses at a fixed frequency regardless of velocity variations; a mechanical platen location generator, for providing location information indicative of a location of the mechanical platen at time points that are determined by the firing pulses; the camera being arranged to obtain images acquired in response to the trigger pulses; and the image processing unit can be arranged to associate location information with the acquired images.
    According to one embodiment, the invention relates to a method. The method may include introducing motion between an inspected object and an optics of an inspection system; the inspected object being expected to move a distance that is substantially equal to a pixel width during a pixel motion period; the illumination of the inspected parts of the inspected object and the direction of a light of the inspected parts towards a camera; and acquiring, by the camera having pixels of pixel width, multiple acquired images of the inspected portions during each pixel motion period, at least two acquired images partially overlapping.
    The method may include processing the acquired images to provide processed images; and detecting defects based on processed image processing.
    The method may include merging different acquired images obtained during a single period of pixel motion.
    The method may include generating multiple processed images, each processed image comprising acquired images obtained during different pixel motion periods, each of acquired images being obtained at the same timing difference from a start of the motion period. pixel during which the acquired image was obtained.
    The method may include providing at least one modification of at least one illumination characteristic during each pixel motion period.
    The method may include illuminating, during a single period of pixel motion, different parts of objects inspected by light beams that differ from one another by the wavelength.
    The method may include illuminating, during a single period of pixel motion, different parts of objects inspected by light beams that differ from one another by an angle of incidence.
    The method may include illuminating, during a single period of pixel motion, different portions of objects inspected by light beams that differ from each other in wavelength and angle of incidence.
    The method may include obtaining at least three acquired images of the inspected portions during each pixel motion period.
    The method may include moving the inspected object with a motion that is characterized by velocity variations; the method may also include generating trigger pulses at a fixed frequency regardless of velocity variations; providing location information indicative of a location of the mechanical stage at time points which are determined by the trip pulses; obtaining images acquired in response to the trigger pulses; and associating location information with the acquired images.
    The present invention therefore relates to an inspection system, comprising: - a camera; A mechanical turntable for introducing a movement between an inspected object and an optical system of the inspection system; the inspected object being expected to move a distance that is substantially equal to a pixel width during a pixel motion period; An illumination module and an optic for illuminating inspected portions of the inspected object and for directing a light from the inspected portions to the camera; and characterized in that the camera is arranged to acquire multiple acquired images of the inspected portions during each pixel motion period, at least two acquired images partially overlapping one another.
    The system may further include: an image processing unit for processing the acquired images to provide processed images; and a fault detection unit for detecting defects based on processed image processing.
    The image processing unit can merge different acquired images obtained during a single period of pixel motion.
    The image processing unit can generate multiple processed images, each processed image comprising acquired images obtained during different pixel motion periods, each of the acquired images being obtained at the same time difference from a start of the period of pixel motion during which the acquired image was obtained.
    The illumination module may be arranged to effect at least one modification of at least one illumination characteristic during each pixel motion period.
    The illumination module may be arranged to illuminate, during a single period of pixel motion, different parts of objects inspected by light beams which differ from one another by the wavelength.
    The system may further be capable of illuminating, during a single period of pixel motion, different parts of objects inspected by light beams which differ from one another by an angle of incidence.
    The illumination module may be arranged to illuminate, during a single period of pixel motion, different parts of objects inspected by light beams which differ from each other by the wavelength and by an angle of impact.
    The camera may be arranged to obtain at least three acquired images of the inspected portions during each pixel motion period.
    The mechanical stage can be arranged to move the inspected object by a movement which is characterized by speed variations; the inspection system further comprising: - a signal generator, for generating trigger pulses at a fixed frequency regardless of velocity variations; A mechanical platen location generator, for providing location information indicative of a location of the mechanical platen at time points that are determined by the firing pulses; The camera being arranged so as to obtain images acquired in response to the triggering pulses; and - the image processing unit being arranged to associate location information with the acquired images.
    The present invention also relates to an inspection method, characterized in that it comprises: the introduction of a movement between an inspected object and an optical inspection system; the inspected object being expected to move a distance that is substantially equal to a pixel width during a pixel motion period; - the illumination of inspected parts of the inspected object and the direction of a light of the parts inspected towards a camera; and acquiring, by the camera which has pixels of a pixel width, multiple acquired images of the inspected portions during each pixel motion period, at least two acquired images partially overlapping one another.
    The method may further include processing the acquired images to provide processed images; and detecting defects based on processed image processing.
    The method may further include merging different acquired images obtained during a single period of pixel motion.
    The method may furthermore comprise the generation of multiple processed images, each processed image comprising acquired images obtained during different periods of pixel motion, each of the acquired images being obtained at the same time difference from a beginning of the period of pixel motion during which the acquired image was obtained.
    The method may further include providing at least one modification of at least one illumination characteristic during each pixel motion period.
    The method may further include illuminating, during a single period of pixel motion, different portions of objects inspected by light beams which differ from one another by the wavelength.
    The method may further include illuminating, during a single period of pixel motion, different portions of objects inspected by light beams that differ from one another by an angle of incidence.
    The method may further include illuminating, during a single period of pixel motion, different portions of objects inspected by light beams that differ from each other in wavelength and angle of incidence.
    The method may further include obtaining at least three acquired images of the inspected portions during each pixel motion period.
    The method may further include moving the inspected object with a motion that is characterized by velocity variations; the method further comprising: generating trigger pulses at a fixed frequency regardless of velocity variations; Providing location information indicative of a location of the mechanical stage at time points that are determined by the trigger pulses; Obtaining images acquired in response to the triggering pulses; and - associating the location information with the acquired images.
    The subject of the present invention is particularly specified in the description. The invention, however, both with respect to the organization and method of operation, as well as the objects, features and advantages thereof, will be better understood with reference to the following detailed description taken in conjunction with the drawings. attached.
    Figure 1 is a timing diagram that shows three images that are obtained for three different camera clock cycles; Figure 2 shows three acquired images that are acquired during a single pixel motion period, according to one embodiment of the invention; Figure 3 shows a test pattern, acquired images, and scanned images according to an embodiment of the invention; Fig. 4 shows an image processor unit which averages the acquired three acquired images for each PMP to provide a single image processed by PMP; Figure 5 shows an inspection system which generates acquired red, green and blue images, according to one embodiment of the invention; Figure 6 shows an inspection system that changes the illumination angle, according to an embodiment of the invention; Fig. 7 shows an inspection method, according to an embodiment of the invention; Figure 8 shows an illumination step of an inspected object, according to one embodiment of the invention; and Figure 9 shows an inspection system, according to an embodiment of the invention.
    It will be appreciated that for reasons of simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for reasons of clarity. In addition, where this is considered appropriate, reference figures may be repeated among
    Figures for indicating corresponding or analogous elements.
    In the following detailed description, many specific details are stated to allow a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention can be practiced without these specific details. In other examples, well known methods, procedures and components have not been described in detail so as not to obscure the present invention.
    The term pixel motion period (PMP) refers to a period during which an inspected object is moved relative to an optical (or camera) inspection system a distance that is substantially equal to a pixel width. It should be noted that at least one of the inspected object, the optics and the camera can be moved. The pixel width is the dimension (width) of an optically enlarged pixel of the camera along a camera scan direction. Thus, if the sensor has pixels that are X microns wide and the magnification of the optics disposed between the sensor and the inspected object is Y, then the pixel width is X / Y microns.
    New systems and methods for image acquisition are disclosed and can be used for optical inspection, in particular - for example - an electronic circuit such as a printed circuit board, a wafer, etc.
    The systems and methods implement multiple scanning: a movement of the inspected object is synchronized with a line period of a camera in a special mode: n acquired images are acquired per unique pixel motion period (e.g. each PEG cycle). It should be noted that the systems and the method do not necessarily generate a PEG signal or do not necessarily trigger the acquisition of images based on a PEG signal generation.
    The systems and methods can satisfy the following equation: # EP <n * LP <PMP, where: EP is the camera exposure period (period during which the camera is open to obtain radiation to generate a single acquired image); LP is the camera line period - which may be equal to (or larger than) EP, PMP is the pixel motion period; and n is the number of multiple images acquired (number of images acquired, acquired by PMP).
    If n acquired images are acquired by PMP, then these n acquired images can be viewed as a set of multiple n acquired images and can be used for the formation of an n-dimensional processed image. For example, during a PMP, three acquired images can be acquired - a red acquired image, a green acquired image and a blue acquired image (by applying a sequence of red illumination, green illumination and blue illumination) then these three acquired images (as well as images acquired during additional PMPs) can be processed to produce a single image processed in three dimensions (or three images processed in a single dimension). This also applies for n> 3 acquired multispectral images.
    The acquired images can also be processed while being subjected to some reduction of n -> m data, where n> m, to provide a smaller processed image with the prescribed properties. For example, n acquired images can be reduced by averaging over a single processed (synthetic) image with a wider dynamic range, less noise, and higher sharpness. In this case m = 1.
    Usually, n is higher (the number of multiple images acquired by single PMP) and the higher the data reduction ratio (eg n -> 1), the higher the image quality (sharpness, signal-to-noise ratio) and viewing tiny defects) can be achieved.
    According to one embodiment of the invention, the invention relates to a method for inspection (and / or imaging).
    The method includes scanning multiple parts (n) of an object inspected by unique PMP. This may include receiving a single PEG encoder, and in response obtaining multiple acquired images (eg - by scanning multiple lines), receiving the PEG encoder and scanning being reiterated. The method may also include transmitting PEG, for example in response to timing information and / or other types of information (eg a camera position sensor). The transmission can be suitably performed by a system motion control encoder, an external unit, etc. It should be noted that the acquisition of multiple images may be triggered by signals other than PEG signals.
    According to one embodiment of the invention, for each PMP, the method comprises obtaining, by a linear scanning camera, n images acquired by linear scanning of parts of the inspected object.
    Acquired images can be obtained and processed to provide one or more (m) processed images. A single processed image may comprise up to mxn acquired images, where m is the number of images processed by single PEG, and n is the number of PEG signals generated by the motion control encoder or the number of PMPs allocated for obtaining acquired images that form the basis of the processed image.
    The process can continue with the transfer of each set of acquired images (which may possibly overlap partially with each other) to an image processing unit (either the same system or an external system).
    The method may continue with the generation (eg by the image processing unit) of at least one processed image of the inspected object (or parts thereof) in response to the acquired images. In various embodiments of the invention, various types of images and methods for generating them can be implemented.
    According to one embodiment of the invention, the method can be continued with the detection, in response to the at least one processed image, of defects in the inspected object (for example a slice, a diced slice, a printed circuit boards, etc.), for example in an inspection system.
    Figure 2 shows three acquired images that are acquired during a single pixel motion period, according to one embodiment of the invention. For example, during a first PMP 10, three acquired images 71, 72 and 73 are acquired. There is a 2/3 pixel superposition between two adjacent acquired images. The acquired images are acquired at each line period 70 which is one-third of the PMP.
    Generally, when n images are acquired by PMP, there may be a superposition of about (n-1) / n pixels between two adjacent images.
    Yet for another example, during a second PMP 12, three acquired images 74, 75 and 76 are acquired. There is a 2/3 pixel superposition between two adjacent acquired images. The acquired images are acquired at each line period 70 which is one-third of the PMP.
    Figure 2 also shows acquired images that are processed to provide processed images that are formed from acquired images that are not superimposed (or barely superimposed).
    The first acquired image (71, 74, 77) of each PMP can be processed to form a first processed image 81. The second acquired image (72, 75, 78) of each PMP can be processed to form a second processed image 82. The third acquired image (73, 76, 79) of each PMP can be processed to form a third processed image 83.
    Alternatively, acquired images can be processed to provide processed images that include acquired images that include important overlays. Thus, a single processed image can be generated by PMP by the average of all the images acquired during the PMP - as represented by processed images 91, 92 and 93.
    It should be noted that other combinations and methods for processing acquired images can be obtained. For example, processed images can be obtained by processing acquired images which overlap more or less.
    According to various embodiments of the invention, image processing may be performed in one or more of the following locations: within the camera (for example, similarly to a portion of a processing unit of programmable image of "smart camera"); inside an acquisition card, externally to the camera, etc.
    In systems and methods according to the invention, the camera operates at a higher frequency than a system setting clock which determines the PMP, so as to provide multiple samplings of the same object for each PMP.
    Figure 3 shows a test pattern 100, acquired images 104, 111 to 113 and digitized images 106 and 116 according to one embodiment of the invention.
    A test pattern 100 comprises a sequence of black and white bands. An ideal digital image 102 represents an idealized digitized image of the test pattern, the ideal digitized image alternating between a maximum level and a minimum level.
    A camera generates an acquired image 104 that includes a variety of gray level bands-including white bands, black bands, and gray bands of different values. The differences between the ideal digital image 102 and the acquired image 104 may contribute to the noise and imperfection of the image acquisition method. A graph 106 illustrates the gray levels of the acquired image 104. It deviates greatly from the ideal digital image 102.
    According to one embodiment of the invention, a camera can obtain three acquired images 111 to 113, each comprising a variety of gray level bands - including white bands, black bands, and gray bands of different values. An average of all three acquired images 111 to 113 is averaged and a graph 116 represents the gray levels of the average image. The graph 116 is closer to the ideal digital image 102 compared to the graph 106.
    Figure 4 shows an image processing unit 340 and three buffers 331 to 333, each buffer receiving a single image acquired by PMP. The image processing unit 340 retrieves the acquired images and averages the three acquired images (e.g., acquired images 71-73) that are acquired for each PMP to provide a single image processed by PMP such that processed image 91. Thus, an average is made for each set of three acquired images (71-73), (74-76) and (77-79) to provide a single processed image, such as a processed image 91. PMP may be equal to 90 ßs, the linear camera scan period may be equal to 30 μβ and the exposure period may be equal to 29.7 μβ.
    The image processing unit 340 may be implemented, for example, on a graphic ALTERA, a CPU (central processing unit), a GPU (graphic processing unit) or any type of processor or ASIC.
    According to various embodiments of the invention, optical conditions (such as, but not limited to, an angle of incidence, a spectrum, a light beam shape, a light beam intensity profile, an angle of collection, attenuation and the like), can be set during each PMP, can be changed from one PMP to another or can be changed (one or more times) by PMP.
    Figure 5 shows an inspection system that generates acquired red, green and blue images, according to an embodiment of the invention. Figure 5 also includes a timing diagram which represents the acquisition of acquired red, blue and green images.
    The inspected object 300 is positioned on a mechanical stage 310 and moves along a horizontal axis. The movement of the mechanical stage 310 can be monitored by an encoder 315 which can generate a PEG for each PMP. The inspection system can provide synchronization between the PEG and the acquired image acquisition or alternatively control the timing of the image acquisition by a controller 318.
    Figure 5 shows the controller 318 being coupled to a signal generator 319 which can output trip pulses in fixed time intervals. The controller 318 may additionally or alternatively receive PEGs or location information from a mechanical stage positioning generator such as an encoder 315. The location information indicates a location of the mechanical stage. 310 at time points that are determined by the trigger pulses.
    The inspected object 300 is repeatedly illuminated by a sequence of a red pulse 301, a green pulse 302 and a blue pulse 303. This illumination causes the camera 330 to acquire red acquired images, acquired images green and acquired blue images. These acquired images can be sent to different buffers 331 to 333. These buffers can be accessed by an image processing unit 340. The image processing unit 340 is coupled to a fault detection unit 350. It should be noted that the image processing unit 340 and the fault detection unit 350 can be integrated.
    Figure 5 shows three sequences of these pulses by PMP. Thus, the acquired images 341 to 349 are acquired by a single PMP - an image per camera linear scan period 340. The acquired images 341, 344 and 347 are acquired red images, the acquired images 342, 345 and 348 are acquired green images, and acquired images 343, 346 and 349 are acquired blue images.
    It should be noted that only one red, green and blue (RGB) sequence, two RGB sequences, or more than three RGB sequences can be generated by PMP.
    It should be noted that although FIG. 5 each represents red, blue or green light pulses as being generated in a non-overlapping manner, different combinations (simultaneous illumination by two-color pulses) can be applied.
    It should also be noted that instead of using different light pulses, different filters (or a configurable filter) can be used to filter different spectral components of light.
    It is further noted that although optics 320 is shown as being parallel to the inspected object this is not necessarily the case. The optics 320 may include a conventional objective lens, a reflective imaging network.
    The camera 33 may be a line scan camera or a zone camera. It can obtain multiple images acquired by PMP and can emit these multiple images obtained by PMP. The camera may perform certain forms of processing (such as filtering, averaging, compression, and the like) on images acquired prior to transmission of these images. The camera 330 may include a network of CCDs or CMOS sensors, and may include multiple lines (e.g., it may include a red sensor line, a green sensor line and a blue sensor line) and may be a TDI (time delayed integration) camera or any network camera operating in a linear scan mode.
    Figure 6 shows an inspection system that changes the illumination angle, according to one embodiment of the invention. Figure 6 also includes a timing diagram.
    An inspection system of Figure 6 differs from an inspection system of Figure 5 in that it illuminates the inspected object 300.
    The inspection system of FIG. 6 illuminates the inspected object 300 by a sequence (a) of an illumination on axis 351 (eg normal incidence) to provide an acquired image on the axis such as 371, 374, and 377, (b) left off-axis illumination 352 to provide left off-axis images such as 372, 375 and 378, and (c) right off-axis illumination 353 to provide right off-axis images such as 373, 376 and 379.
    Figure 6 shows three sequences of these pulses per PMP. Thus, acquired images 371-379 are acquired by a single PMP-image per linear scanning period of camera 370.
    It should be noted that only one sequence, two or more sequences of three sequences can be generated by PMP.
    It should be noted that although FIG. 6 represents illumination pulses 351, 352 and 353 as being generated in a non-overlapping manner, different combinations (simultaneous illumination by pulses of different illumination angles) can be applied.
    It should also be noted that, in connection with FIGS. 5 and 6, different combinations of illumination angles, illumination spectrum or collection can be used.
    Any of the inspection systems of Figures 5 and 6 may include an illumination module 317 that can apply pulsed illumination or continuous illumination (CC). An illumination module may include one or more light sources. Different light sources may differ from each other in their illumination spectrum, intensity, phase, angle and the like. For example, the illumination module 317 may have a red light source, a blue light source and a green light source or a set of configurable filters that filter red, blue or green illumination. This can also apply mutatis mutandis to the illumination module.
    Generally, different acquired images may include additional physical information of the inspected object of any nature: multispectral, polarization, 3D vision, reflectance properties (bidirectional reflectance distribution function).
    Figure 9 shows an inspection system that acquires four images acquired by PMP, according to one embodiment of the invention. Figure 9 also includes a timing diagram.
    In Fig. 9, the inspected object carries the reference numeral 600, the camera the reference numeral 360, the image processing unit carries the reference numeral 640 and the illumination pulses 601.
    The inspection system of Figure 9 differs from the inspection system of Figure 5 by the number of acquired images that is acquired by PMP - four images (such as images acquired 641 to 644) and by the fact that have four buffers 331 to 334. The inspection system of Figure 9 is arranged to maintain the fixed optical parameters by PMP.
    It should be noted that a single inspection system can be configured to function as either of the inspection systems in Figure 5, 6 and 9.
    Figure 7 shows a method 900 for inspection, according to an embodiment of the invention.
    The process 900 starts with a sequence of steps. For reasons of simplicity of explanation, step 910 is illustrated as being followed by steps 920, 930, 940, 950 and 960 although a repetition of these different steps may be performed in parallel or in a pipeline manner. . For example, an inspected object can be moved in a continuous manner and during this movement multiple images are obtained, transmitted and processed. In addition, an acquired image can be obtained while a previously acquired image is transmitted or processed.
    Step 910 includes introducing motion between an inspected object and an optical inspection system. The inspected object is expected to move a distance that is substantially equal to a pixel width during a pixel motion period. Step 910 may include moving the inspected object, moving the optics, or both.
    Step 920 includes illuminating inspected portions of the inspected object and the direction of light of the inspected portions to a camera.
    Step 910 may include moving the inspected object through a motion that is characterized by velocity variations. In this case step 920 may include step 926 of generating trigger pulses at a fixed frequency regardless of velocity variations; providing location information indicative of a location of the mechanical stage at time points that are determined by the trip pulses; obtaining images acquired in response to the trigger pulses; and associating location information with the acquired images.
    Step 930 comprises acquiring, by the camera that has pixels of a pixel width, multiple acquired images of the inspected portions during each pixel motion period, at least two acquired images partially overlapping one another.
    Step 930 may include obtaining at least three acquired images of the inspected portions during each pixel motion period.
    Step 940 includes transmitting images acquired from the camera.
    ; Step 950 includes processing the acquired images to output processed images. It should be noted that the processing or part of the processing can be performed before the camera emits images and in this case step 940 will include the transmission of images processed or partially processed by the camera.
    Step 960 includes the detection of defects based on processed image processing. This may include chip-on-chip, chip-on-chip, chip-to-database, and any other fault detection algorithm.
    Step 950 may include merging different acquired images obtained during a single pixel motion period to provide one or more processed images.
    Step 950 may comprise the generation of multiple processed images, each processed image comprising acquired images obtained during different periods of pixel motion, each of the acquired images being obtained at the same time difference from a start of the period of pixel motion during which the acquired image was obtained. For example, each of the processed images 81 to 83 in Figure 2 includes acquired images that were obtained at the same time within different PMPs.
    Step 920 may comprise a step 921 of performing at least one modification of at least one illumination characteristic during each pixel motion period. Figure 8 shows step 921 according to one embodiment of the invention.
    Step 921 may comprise at least one of steps 922, 923, 924 and 925.
    Step 922 includes illuminating, during a single period of pixel motion, different parts of objects inspected by light beams that differ from one another by the wavelength. An example of such a change is shown in Figure 5.
    Step 923 includes illuminating, during a single period of pixel motion, different parts of objects inspected by light beams that differ from one another by an angle of incidence. An example of such a change is shown in Figure 6.
    Step 924 includes collecting light from different parts of the inspected object, during a single period of pixel motion, at different collection angles.
    Step 925 includes illuminating, during a single period of pixel motion, different parts of objects inspected by light beams that differ from each other by their wavelength and angle of incidence.
    Each of the inspection systems 295-296 and the method 900 may have one or more of the following characteristics: (a) an improved CCD aliasing parameter and an enhanced MT F CCD parameter (decreased read noise leads to sharper edges eg, black-white transitions, and thus at a higher contrast); (b) a reduction in CCD read noise when the number of processed images (m) is less than the number (n) of acquired images that are processed to provide the processed images; (c) a reduction in persistence of movement with a shorter exposure period; (d) a dynamic range increased by noise reduction when n> m while maintaining the intensity of pixel signals; (e) improved detection of tiny defects by general MTF enhancement (particularly at high spatial frequencies): means of high spatial frequency (tiny objects, meaning regular patterns of high density and defects, which are characterized by a weak signal and, therefore, a low signal-to-noise ratio, a noise reduction leads to a higher signal-to-noise ratio and a better contrast of tiny objects; (f) image stability enhancement by averaging shot noise when n> m; and (g) obtaining multiple image information when applying special illumination conditions.
    While certain features of the invention have been shown and described in this specification, many modifications, many replacements, changes, and the like may occur to those skilled in the art. These fall within the scope and scope of the present invention.
    权利要求:
    Claims (20)
    [1]
    An inspection system, comprising: - a camera (330; 360); a mechanical stage (310) for introducing a movement between an inspected object (300; 600) and an optical system (320) of the inspection system; the inspected object (300; 600) being expected to move a distance that is substantially equal to a pixel width during a pixel motion period; an illumination module (317) and an optic (320) for illuminating inspected portions of the inspected object (300; 600) and for directing a light from the inspected portions to the camera (330; 360); and characterized in that the camera (330; 360) is arranged to acquire multiple acquired images of the inspected portions during each pixel motion period, at least two acquired images overlapping one another.
    [2]
    2. An inspection system according to claim 1, characterized in that it comprises: an image processing unit (340; 640) for processing the acquired images to provide processed images; and a fault detection unit (350) for detecting defects based on processed image processing.
    [3]
    3. Inspection system according to claim 2, characterized in that the image processing unit (340; 640) merges different acquired images obtained during a single period of pixel motion.
    [4]
    4. Inspection system according to claim 2, characterized in that the image processing unit (340; 640) generates multiple processed images, each processed image comprising acquired images obtained during different periods of pixel motion. , each acquired image being obtained at the same time difference from a start of the pixel motion period during which the acquired image was obtained.
    [5]
    5. Inspection system according to claim 1, characterized in that the illumination module (317) is arranged to achieve at least one modification of at least one illumination characteristic during each period of pixel movement.
    [6]
    6. Inspection system according to claim 1, characterized in that the illumination module (317) is arranged to illuminate, during a single period of pixel movement, different parts of the object inspected (300; 600 ) by light beams that differ from each other by the wavelength.
    [7]
    7. Inspection system according to claim 1, characterized in that it is also able to illuminate, during a single period of pixel movement, different parts of the object inspected (300; 600) by light beams which differ from each other by an angle of incidence.
    [8]
    8. Inspection system according to claim 1, characterized in that the illumination module (317) is arranged to illuminate, during a single period of pixel movement, different parts of the object inspected (300; 600 ) by light beams which differ from each other by the wavelength and by an angle of incidence.
    [9]
    An inspection system according to claim 1, characterized in that the camera (330; 360) is arranged to obtain at least three acquired images of the inspected portions during each pixel motion period.
    [10]
    10. Inspection system according to claim 1, characterized in that the mechanical plate (310) is arranged to move the inspected object (300; 600) by a movement which is characterized by variations in speed; the inspection system further comprising: - a signal generator, for generating trigger pulses at a fixed frequency regardless of velocity variations; A mechanical platen location generator (310), for providing location information indicative of a location of the mechanical platen (310) at time points that are determined by the firing pulses; The camera (330; 360) being arranged to obtain images acquired in response to the triggering pulses; and - the image processing unit (340; 640) being arranged to associate location information with the acquired images.
    [11]
    11. A method of inspection, characterized in that it comprises: - the introduction of a movement between an inspected object and an optical system inspection; the inspected object being expected to move a distance that is substantially equal to a pixel width during a pixel motion period (910); - the illumination of inspected parts of the inspected object and the direction of a light of the inspected parts towards a camera (920); and acquiring, by the camera that has pixels of a pixel width, multiple acquired images of the inspected portions during each pixel motion period, at least two acquired images partially overlapping (930).
    [12]
    12. The method of claim 11, characterized in that it comprises the processing of acquired images to provide processed images (950); and detecting defects based on processed image processing (960).
    [13]
    13. The method of claim 12, characterized in that it comprises the merging of different acquired images obtained during a single period of pixel movement.
    [14]
    14- Method according to claim 12, characterized in that it comprises the generation of multiple processed images, each processed image comprising acquired images obtained during different periods of pixel movement, each of the acquired images being obtained at the same difference of timing from a start of the pixel motion period during which the acquired image has been obtained.
    [15]
    15. The method of claim 11, characterized in that it comprises the embodiment of at least one modification of at least one illumination characteristic during each pixel movement period (921).
    [16]
    16. The method of claim 11, characterized in that it comprises the illumination, during a single period of pixel movement, of different parts of object inspected by light beams which differ from each other by the length of the light. wave (922).
    [17]
    17. A method according to claim 11, characterized in that it comprises illuminating, during a single period of pixel movement, different parts of objects inspected by light beams which differ from each other by an angle d incidence (923).
    [18]
    18. Method according to claim 11, characterized in that it comprises the illumination, during a single period of pixel movement, of different parts of objects inspected by light beams which differ from each other by the length of the light. wave and an angle of incidence (925).
    [19]
    19. The method of claim 11, characterized in that it comprises obtaining at least three images acquired parts inspected during each period of pixel movement.
    [20]
    20. The method of claim 11, characterized in that it comprises the movement of the inspected object by a movement which is characterized by variations in speed; the method further comprising: generating trigger pulses at a fixed frequency regardless of velocity variations; Providing location information indicative of a location of the mechanical stage at time points that are determined by the trigger pulses; Obtaining images acquired in response to the triggering pulses; and - associating the location information with the acquired images (926).
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    同族专利:
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    法律状态:
    2013-04-30| RE| Patent lapsed|Effective date: 20121031 |
    优先权:
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    US25309909P| true| 2009-10-20|2009-10-20|
    US25309909|2009-10-20|
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