• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The problems of the known time-domain short-coherence method with complex and unstable interference states of the eye and their low compatibility with the prior art corneal topography are solved by using a complete space-time domain short-coherence interferogram. The interferometric matching takes place on the one hand visually or by means of digital image pattern recognition and on the other hand on the basis of image pairs of the front-illuminated eye with antiphase space-time domain short-coherence interferograms. To register the space-time domain interferogram, a two-dimensional detector array is used. The result is a very sensitive and adjustment-tolerant method, which also has the potential for implementation as a handheld device. A pixel sum A-Scan signal derived from the image pairs is used to synthesize tomograms that provide increased security in reading the desired distances.
    公开号:AT511740A2
    申请号:T10542011
    申请日:2011-07-18
    公开日:2013-02-15
    发明作者:Adolf Friedrich Dr Fercher
    申请人:Adolf Friedrich Dr Fercher；
    IPC主号:
    专利说明:

    I • ·
    Dr. Adolf Friedrich Fercher, Hassreitersteig 3/11, 1230 Vienna
    Patent Application: Methods and Arrangements for Space-Time Domain Short-coherence interferometry for partial ophthalmic length measurement and corneal topography
    DESCRIPTION 1. Technical Field of the Invention.
    Partial ophthalmic length measurements and corneal topography (photokeratoscopy or videokeratography) are used in ophthalmology to determine the ablation parameters of the cornea and to size intraocular lens implants for refractive surgery. 2. State of the art.
    Partial ophthalmic length measurement and corneal topography provide data such as eye length and anterior chamber depth as well as the power distribution on the cornea. 2.1 Short-coherence interferometric segment length measurement in ophthalmology.
    These techniques work with the interferometric matching of path lengths or transit times as well as path length differences or transit time differences in short-coherence interferometers. Length and time are equivalent because of the known speed of light.
    Interferometric adjustment.
    Short-coherence interferometry methods are based on a comparison of the size to be measured in the measurement object with corresponding known quantities in the interferometer. This interferometric path adjustment is noted when tuning the interferometric path difference between the reference beam and the object beam via the occurrence of an interferogram at the interferometer output. An interferogram occurs when the optical lengths {= geometric length multiplied by the group index) of the reference beam and the object beam within the coherence length are the same or, in other words, the reference mirror is within the interference path. Hereinafter, this state is simplified as "interference status". (of the interferometer). The length of the 1 patent 50th
    I
    Interference distance corresponds to the coherence length 61 = c.6t of the used light; c light velocity, 6t = coherence time. An interferogram is observed during propagation time differences of the two interfering light beams within the coherence time 6t, as illustrated by detail 100 in FIG. 1, although rather rarely, as here, formed from circular interference fringes.
    Reflectometer technique: In this variant of short-coherence interferometry, the object (eye) is located in the measuring arm of a Michelson interferometer and is illuminated by the measuring beam while the other interferometer arm forms the interferometric reference arm (reference beam). The measurement is based here on a transit time or path length adjustment between a reference beam of known length and the object beam emerging from the object. For this purpose, the interferometric path difference or transit time of the light of the interfering beams by means of beam retarder, such as a movable retroreflector (235) at the end of the reference arm of the reflectometer or by means of other "delay lines". (for example, described in the article "Optical Coherence Tomography" in: Progress in Optics, Editor E. Wolf, Vol. 44, pp. 215-302).
    Dual-Beam Interferometry: The short-coherence interferometric dual-beam length measurement preferred today is based on the interferometric comparison of transit time or path length difference in the eye with transit time or path length differences of known magnitude in a two-beam interferometer. Here, the eye is illuminated by two measuring beams ("Dual Beam") with a delay line generated in the interferometer and known delay time or distance difference. Both measuring beams are reflected, for example, both on the cornea and the fundus. This results in four object beams with additional path difference equal to one eye segment length. One finds among the object beams two, whose runtime or path difference generated in the measurement object (eye) can be compensated by the transit time or path difference generated in the interferometer, so that there is time coherence between them. This interferometric path difference comparison between the two measuring beams and two eye reflection points is also controlled by the occurrence of an interferogram in the interference status. An interferogram is also observed here, as shown in FIG. (This procedure is used in the lOL-Master of the company Carl Zeiss Meditec.) 2 Patent
    "
    In both interferometry methods, a so-called time domain interferogram forms the basis for interferometric matching. The intensity of this interferogram is registered photoelectrically as a function of the transit time difference or the corresponding path difference. In general, an interferogram only occurs if the path difference of interfering beams remains smaller than its coherence length. Thus one obtains from the easily measurable path length of the reference beam in the reflectometer method, or from the known path differences of the illuminating measuring beams in the dual-beam technique, the eye segment length - up to the coherence length exactly. Suitable light sources for this purpose emit light of short coherence length or time coherence and possibly full spatial coherence.
    Interferometry domains.
    Space Domain Short-coherence Interferometry: Considering only the spatial structure of the interferogram at the interferometer output, so for example the Fresnel-like interference fringes in Figure 1, we speak of space-domain interferometry. The structure of this interferogram is determined by the different optical transit times or optical lengths of transversely adjacent light paths in the measuring beam. Space domain Interferograms provide data on the transversal spatial structure of the media or optical components passed through by the measuring beams. This is one of the most important measurement techniques of optical technology; an analogous principle is also part of the present invention for corneal topography.
    Time domain Short-coherence interferometry: Today, almost exclusively short-coherence interferometry in the time domain is used for partial length ophthalmological measurements. Here, the length measurement by interferometric transit time compensation of those rays that produce a single point of the space interferogram. Time domain Interferograms provide data on the depth structure of the media or optical components passing through the measurement beam. This technique is used for length measurement, for example in optical fiber technology and in ophthalmology; An analogous principle is also part of the present invention for partial length measurement. A-scan signal. When tuning the interferometric path difference or transit time of the light of the interfering beams by means of beam retarders or delay lines, the in each 3 Patent 50 · · *
    Temporal intensity change caused by the point of the space interferogram, the time domain interferogram, from which the optical time domain A-scan signal (term analogous to the corresponding ultrasound technique) is derived. The electronic A-scan signal is obtained from the photoelectric signal of the time domain optical interferogram essentially by bandpass filtering and rectification. Maxima of the A-Scan signal strength mark interference status, the reference mirror (235, 340, 341) is located within the interference path, there is coincidence between transit times in the reflectometer or propagation time differences in the dual-beam interferometer with those caused by the eye. The A-Scan signal forms the basis of the current interferometric segment measurement.
    Space-time domain Interferometry: In fact, the space domain interferogram in each of its points also has a temporal domain, which becomes visible when the path difference of the interferometer is tuned. Basically, there is always a space-time domain interferogram (RZI) in the interferometric segment length measurement, the two domains have been used so far but independently of each other; the present invention utilizes their complementary properties simultaneously to the span measurement.
    The measurement accuracy of the space-time domain interferometry in the beam direction is determined by the
    Depth extension of the RZI, that is, given by the coherence length oil, given: 61 = c.Öt = 2.Ιη2.λο7 (π.Δλ). (1) Δλ is the half-width, λ0 is the mean wavelength of the light used (for simplicity, a common Gaussian spectrum was assumed). Today, the coherence length of light sources used for this purpose is typically in the micrometer range, as in broadband superluminescent diodes and many solid-state lasers. The measurement accuracy in the transverse direction is determined by the diameter of the measurement beam focus, or in the case of Gauss beams by the diameter of the beam waist. 2.2 corneal topography.
    The keratoscope used so far is based on a so-called Placido disc, a ring system of concentric, arranged at regular intervals, alternately differently colored rings, placed in front of the eye and mirrored from the cornea front surface 4 Patent 50. Through a small opening in the center of the Placido disk, the virtual mirror image of these rings is observed on the cornea and from their geometry, the distribution of the radius of curvature and thus the refractive power distribution over the corneal surface is calculated. The most commonly used photokeratoscope today is equipped with a digital camera for the photographic documentation of the rings. In computer assisted photokeratoscopy, image processing programs are used to determine from the shape of the Placido ring patterns in addition to the refractive power distribution further geometric parameters of the corneal shape. 3. Technical task. 3.1 Short-coherence interferometry.
    Basically, line-like measuring beams would be ideal for section length measurement in order to precisely define the transversal position of the measuring location. In fact, however, the measuring beams used always have larger diameters. Even with the physical ideal of the Gaussian beam, for example, the diameter increases with the distance from the beam waist along the beam axis, indirectly proportional to the beam waist diameter. For example, the asymptotic divergence angle is already ± 0.1 rad at a light wavelength of 0.8 pm and a beam waist diameter of 5 pm. Outside the beam waist, therefore, the transverse distribution of amplitude and phase of the object beam is influenced by an increasingly larger environment. Therefore, an RZI in uniform interference state does not occur at the interferometer output. This can be seen from the associated space interferogram (100), which indicates different interference states due to interference fringes because different path differences exist across its area. However, for a well-modulated electronic signal, the entrance pupil of the photodetector must not be much larger than the distance of two interference fringes in the space-domain interferogram, otherwise the photodetector averages over several interferogram points with different phases and the electronic measurement signal disappears. For these reasons, only a very small part of the still very moving space interferogram is suitable as a measuring point for the photoelectric detection of the time-domain interferogram. 5 Patent 50
    In addition, the eye is very unstable. It constantly performs movements, even when fixing a target object. The search process for the constantly moving interferogram in the two-dimensional pupil makes it much more difficult for subjects to take measurements. In addition, because of the initially not known eye length, an optical A-scan over a larger path difference (a few millimeters) is required. The result is that once a position of a measuring point for photoelectric detection of the time interferogram is lost again. The search for the exit point of the object beam and then a suitable measuring point in the associated interferogram as well as the proper movements of the eye lead to longer and therefore cost-driving measurement processes and to reduced measurement quality.
    Furthermore, the eye is not a centered optical system. The optical axes of the light-reflecting interfaces of cornea and lens and the normal of the retinal surface do not coincide. Therefore, object rays usually do not pass through the same location of the eye pupil through which the measurement beam has entered. Furthermore, the object light, which results from reflection on differently curved eye structures, practically always has different radii of curvature than the reference light. Therefore, space interferograms with different spatial basic structures occur.
    The above-mentioned methods are complex to handle and, in particular, do not provide a definite measure as a result.
    The technical problem is to provide a short-coherence interferometry part length measurement technique that overcomes the above disadvantages. 3.2 Cornea topography.
    Since the corneal topography usually occurs together with the partial length measurement, a common measurement of both sizes with a device is important. Due to the risk of fatigue for patients who are often elderly and disabled, it is important to avoid lengthy measuring procedures with the risks of misplacement and inattention when fixing targets. A combination of currently used (computer assisted) photokeratoscopy with short-coherence interferometry is difficult and expensive because of very different and largely incompatible measurement techniques. 6 Patent 50
    The technical task is therefore to specify a short-coherence interferometry part length measurement technique that allows to perform cornea topography. 4. Invention 4.1 Space-Time Domain Short-coherence interferometric length measurement on the eye.
    The Justierprobleme the optical short-coherence interferometric length measurement on the eye, in the interferometric comparison of maturities or path lengths in the eye with known maturities or path lengths in the interferometer in the reflectometer technology, or of transit time differences or path length differences in the eye with known transit time differences or path length differences in the interferometer In the case of the dual-beam method, partial distances of the eye are measured, according to the invention, the interferometric matching takes place on the basis of a complete space-time domain of short-coherence interferograms in the eye pupil, in its surroundings or in an image thereof.
    Basically, the presence of the space-time domain short coherence interferogram (RZI) serves as a criterion for the presence of interferometric matching. This type of short-coherence interferometry is new and, against the background of previous methods, unexpected and surprising. It is easy to understand in retrospect, has a whole range of new and advantageous features and has not yet been described.
    For the detection of the RZI, a reference beam (232) and object beam (243, 244) is registered in the short-coherence interferometry reflectometer, or a two-dimensional detector array (246) registering the object double beams (426, 427) in the case of the dual beam interferometer Eye pupil arranged. Since the RZI is so largely independent of its position and shape in the pupil is detected, the length measurement of moderate movements and structural variations of the RZI is not affected
    The presence of the interferometric matching or interference status can be assessed visually or by means of digital pattern recognition of line-type structures on the basis of the entire image detected by the detector array (246), namely RZI including its vicinity, in a preliminary version of the invention. In a more sophisticated version of the invention, the presence of interferometric matching or interference
    7 Patent SO »· I ·
    Status assessed with the help of coherent versus incoherent (RZI versus environment) distinction. For this purpose, two images of the RZI registered by the detector array 246 with their closer surroundings, hereinafter referred to as "array image", are used. (and depicted as monitor image 248 in Figures 2, 3, and 5) is processed into an interferogram difference image. The interferogram difference image is formed as a difference between two temporally as short as possible successive antiphase array images; this will be explained in more detail below. In this interferogram difference image, both the RZI and the environment disappear outside the interference state (of the interferometer); within the interference state, only the environment that remains RZI disappears. This makes the decision on the presence of an interferometric comparison quite easy even with a visual assessment. The image signal present only in the case of interference status triggers the reading of the relevant reference-mirror position and thus makes it possible to display the relevant partial-segment length by means of the display (290).
    Finally, the presence of interferometric matching is judged by pixel sums PS formed from the pixel amounts of the interferogram difference image. These pixel sums also disappear outside the interference status and outside the interferogram regions (251, 262). Applying these pixel sums along the interferometric path difference yields a pixel-sum RZI A-Scan signal analogous to the classic short-coherence A-scan. 4.2 Interferometric corneal topography.
    The low compatibility of current short-coherence interferometric segment length measuring techniques with today's corneal topography is inventively solved in that, like the segment measurement, the cornea-topographic shape measurement on the basis of a complete space-time domain short-coherence interferogram in the cornea he follows.
    The interferometric corneal topogram is the spatial portion of the RZI located in the cornea. It reflects the lengths of all sections, in particular also the off-axis, to the cornea front surface, based on the reference beam at the reflectometer or relative to an optical leg of the eye in the dual beam method. The invention thus makes it possible to carry out the corneal topography with the same interferometer which has been patented for 50 * *
    The length measurement is used, whereby only two parameters of the interferometer illumination, namely coherence length and measuring beam diameter, are to be adapted. 4.3 RZI-based tomography. RZI-A-Scan signals also form the basis for new tomographic imaging methods, as they provide, similar to optical coherence tomography, line elements derived from laterally adjacent zones for the synthesis of tomographic images. From these RZI tomography images you get the sought lengths and sectional images through the cornea topography. Because of the two-dimensional mapping of the measurement environment, the reading reliability and interpretation of the measured values, figures 5, increases.
    The following explanation of the invention is based on the following figures:
    FIG. 1: Snapshot of a space-time domain interferogram 100 taken in front of the exit pupil of the eye; 100 '= enlarged drawn version of the space-time domain interferogram 100. The here annular interference fringes form a Fresnel-like structure of about 1 mm in diameter, because the interferometric path difference is determined in transversally adjacent points by the spherical shape of the cornea surface reflecting the measuring beam , Not always is the center of the stripe system in the middle of the observable interferogram and not always are the interference fringes circular. Due to the tissue pulsation, the interference fringes move periodically in the radial direction by a few stripes per second. The circular outer edge 101 is generated by a circular aperture. The speckle structure 102 within this edge is generated by the corneal reflexes.
    FIG. 2: Reflectometer-based ophthalmic space-time interferometry with simple projection of the space-time interferogram onto the detector array.
    FIG. 3: Reflectometer-based ophthalmic space-time interferometry with imaging of the space-time interferogram onto the detector array.
    FIG. 4: Ophthalmic space-time interferometry on the basis of a reflectometer with step reference mirror.
    FIG. 5: Dual-beam ophthalmic space-time interferometry.
    9 Patent SO * * 6. Description, embodiments.
    The methods of the invention relate to short-coherence interferometric length measurement based on the RZ1, topography and tomography using this technique. 6.1 Space-time domain interferometer based on the reflectometer technique.
    The transverse intensity distribution at the interferometer output is registered by means of a two-dimensional detector array over an interferometric path difference including the possible eye lengths; Thus, there is a space-time domain A-scan. At regular path difference distances that are less than or equal to the coherence length, the presence of interference, ie the occurrence of the RZ1, is checked by image pattern recognition and image processing on the array image. From the reference mirror positions of the detected RZl one obtains the optical path lengths. This eliminates the time-consuming and time-consuming search for a useful measuring point and the difficult pursuit of this measuring point in the space domain interferogram during the course of the measurement. In principle, it suffices for the object and reference beams to strike one another superposed on the two-dimensional detector array.
    FIG. 2 outlines the scheme of an implementation of the method according to the invention on a reflectometer basis. The ophthalmic short-coherence interferometer used here consists of a Michelson interferometer 21 with the eye 240 in the measuring arm, and the monitor 250 (shown in box 22).
    The light beam 228 coming from the short-coherence light source 227, for example a superluminescent diode with a beam collimator or another short-coherence light source at the interferometer input, is collimated by the zoomable telescope 229 consisting of the optics 221 and 222 and connected to the eye pupil 253 or for interferometric corneal topography - adapted to the corneal diameter. The beam splitter 210 splits this light beam into measuring beam 231 and reference beam 232. The reference beam is directed by the 90 ° reflector 234 onto the retroreflector 235 and reflected by it. The retroreflector 235 is mounted on a displacement unit 236, for example a scan table equipped with stepper motors or with piezo linear drive. The retroreflector 235 is continuous or with regular stepsizes, in particular 10 patent 50 < · T I · ► * · *
    I * I t * ·· »· H • > * * * * ·; By odd multiples of quarters of the central wavelength, controlled by the computer 249 moves and so agrees the path difference in the interferometer in the sense of a delay line. The respective position of the reference mirror is reported by - the state of the art - encoders or displacement sensors to the computer 249 or another computer 290, which calculates the partial route length from 2 such data based on the relationship between position code and metric mirror position and the result on a display 290 indicates.
    The 90 * reflector 234 is mounted on a displacement unit 237, such as a piezo actuator for short distances. The latter allows the deflecting mirror 234 to generate an antiphase space-time interferograms for the interference detection by an odd number of λο / 4 in the direction of the beam 232 (double arrow 238) to move. Mounting of the retroreflector 235 and displacement distance of the displacement unit 236 are designed so that the reference beam 232 can be scanned by the expected maximum partial distances TS plus a few millimeters (TS +) (eg 60 mm).
    The partial beam reflected by the beam splitter 210 is the measuring beam 231. It is partially reflected at all boundary surfaces of the measuring object (eye) 240, as indicated in FIG. 2 for the cornea front surface 241 and the fundus surface 242. The object beams 243 and 244 reflected at these interfaces pass through the beam 210 to the two-dimensional detector array 246 located in front of the eye pupil, where they overlap the interferometric reference beam 232 reflected by the retroreflector 235.
    The result is a light spot 251 or 262, in which one can observe the RZI 252 in the case of interference status. The computer 249 registered with the aid of the detector array 246, the array image at regular intervals with the associated interferometer path difference and presented - at adjusted beam path - first its not further processed version in the monitor image 248 with the light spots 251 and 262 and RZI 252 (Figures 2, 3 and 5). A separate illumination of the eye, for example by means of an LED 260 via the partially transparent 45 ° reflector 230, helps with the adjustment process (also in the other interferometer arrangements outlined here). 11 Patent 50 • * • · • · * ** < F t
    In interferometric matching, a reference mirror position zR in FIGS. 2, 3 and 4 corresponds to a specific object depth position, both calculated along the associated beams in optical lengths from the beam splitter 210. In the dual beam beam path of FIG. 5, a position yR of the reference mirror 235 corresponds to an optical path difference 2.WD in the Michelson interferometer and thus a corresponding path (WD) in the object. The reference mirror position is detected, for example, by a stepper of the respective displacement unit (236 in Figures 2, 3 and 5, 337 in Figure 4) and registered by the computer 249.
    All the two-beam interferograms used here, see equations (2) and (3) below, depend only on the phase difference Δφ from object beam to reference beam. It is therefore possible to carry out the required path length changes and phase shifts in both the reference beam and in the measuring beam in all interferometric beam paths, as in any two-beam interferometer. For example, devices such as delay lines, which accomplish the tuning of the optical length or phase of the reference beam, or actuators for obtaining an antiphase RZI.
    FIG. 3 also outlines the scheme of an implementation of the method according to the invention on a reflectometer basis. In order to avoid that object beams (265 in FIG. 3) miss the photodetector array 246 because of too large an angle to the optical axis 239, a plane in, in front of or behind the eye pupil 253 from an optic 254 to the two-dimensional detector array (FIG. 246). In the arrangement according to FIG. 3, the interferogram, which occurs virtually in one plane in, in front of or behind the eye pupil (253), is imaged onto the detector array 246. It is thus also possible-depending on the position and focal length of this optics-to adapt the interferogram size and the strip density to the detector array 246 and at the same time to image the surroundings of the eye pupil. The latter facilitates the adjustment process considerably.
    Space-time interferometry based on a reflectometer with step reference mirror. The
    Stabilization of the eye during the measuring time in an optimal measuring position succeeds with a shorter measuring time obviously easier than with a long one. A shortening of the measurement time can be achieved by a Michelson interferometer with step reference mirror according to Figure 4: In the already described in connection with Figures 2 and 3 length measurement on the eye
    12 Patent SO
    the reference mirror 235 is in principle moved along the entire length of the eye. However, since almost all optical eye lengths are between 30 mm and 40 mm, it is possible to shorten the reference mirror path in the interferometer for eye length measurement by making the reference beam hit different levels of a staircase reference mirror with mirror levels offset in the beam direction while tuning its length , During the movement of the reflected reference beam 232 along the surface of the single mirror stage from the 90 ° reflector 334 to the step mirror (equipped with the 2 mirror stages 340 and 341 in FIG. 4), the reference beam length only becomes due to the movement of the 90 ° reflector in the y direction modulated. If the reference beam hits the step, the reference beam length additionally changes by twice the step height (2.F). Thus one can provide one or more fixed path differences, for example 2.F = 50 mm, to the object beam and need only mechanically scan the remaining distance of about 15 mm.
    In FIG. 4, the 90 ° reflector 334 is mounted on a displacement unit 337. During the tuning of its length, the 90 ° reflector deflects the reference beam one after the other onto the two mirror stages 340 and 341 offset in the beam direction, which predefine the fixed path difference 2.F. The width of the mirrors 340 and 341 is about twice the beam diameter plus the distance 336 by which the reference beam is to be scanned additively to the fixed path difference in its length. In this way, a large piece (F) of the axis length can be skipped without time-delay scanning. The retroreflector pair 340 and 341 is also mounted on a translation stage 338 with a piezo drive 339. This device is used here, as well as in the arrangements of Figure 2 and 3, for generating anti-phase space-time interferograms for the interference detection, as described below.
    In the boxes 41 and 42 of Figure 4 arrangements are indicated which combine 2 light sources as interferometer illumination (227). In box 41, the light sources 401 and 402 by means of beam splitter 403, in the box 42 the light sources 701 and 702 by fiber coupler 700. These devices make it possible to illuminate the interferometer concerned, for example, with light 2er different central Wellenkängen and / or with light of two different coherence lengths. 13 Patent 50 * »·· t« · · · • * * · · · · * * * * * * ♦♦ · · · · * * * t »· · # ♦« · ·
    Furthermore, FIG. 4 shows a region 43 in the beam path, which allows a device to visually observe the plane imaged by an optical system 254 on the two-dimensional detector array (246) in, in front of or behind the eye pupil 253. This is done by means of a beam splitter 280, which projects this image onto a line cross 281 or a similar device, and an eyepiece 282, which helps the observer 283 to view this image. In place of the eyepiece can also be an electronic camera with associated monitor occur. Such an observation device may also be helpful in the arrangements according to FIGS. 2, 3 and 5.
    The computer 249 in FIGS. 2, 3 and 4 controls the translation tables 236 or 338 and the actuators 237 and 339, respectively, and performs the image processing described below on the measurement data recorded by the array 246.
    The step mirror method can be extended analogously by the use of front and rear surfaces of the reflectors 340 and 341 and by using additional reflectors in its flexibility. 6.2 Ra um-time domain interferometer based on the dual-beam technique.
    The scheme of a corresponding implementation of the method on the basis of dual-beam interferometry is shown in FIG. 5. This implementation consists of a Michelson interferometer 51, here implemented in fiber optics, the coupling unit 52 to the eye 240 and the computer 249 controlling the interferometer and processing the measurement data with the monitor 250.
    Again, according to the invention, the intensity distribution in the RZI in or near the eye pupil is registered with its surroundings by means of a two-dimensional detector array 246 over an interferometric path difference including the possible eye lengths. Likewise, in path difference steps of odd multiples of Xg / 2 and equal to or smaller than the coherence length, visually, or by image pattern recognition and image processing at the RZI, the presence of interference is also checked here. Individual reference mirror positions of the detected space-time interferograms here already result in optical path lengths WD or depth distances of a first light-reflecting object structure relative to a second light-reflecting object structure. 14 Patent 50 «* · · ·» · · · fl * * * ♦ «* ·· • ♦ * · t ·» · I ♦ • ·· ·· * »» «· ·
    The core of the fiber optic Michelson interferometer is a fiber coupler 404. Its input fiber 405 is optically coupled from coupler 404 to fiber 406. The light coupled into the fiber 405 by the short-coherence light source 227 is distributed by the coupler 404 to both fibers and, when collimated by the collimators 408 and 409, illuminates the retroreflector 413 and the retroreflector 235, respectively, as the light beam 410 and 411, respectively. The retroreflector 413 is on one Displacement unit 237 mounted, which allows shifts in the beam direction by odd numbers of λο / 4 for generating anti-phase space-time interferograms for interference detection. 237 is, for example, a piezoelectric actuator. The retroreflector 235 is mounted on a displacement unit 236 so that the optical path differences (WD) of the two light beams passing from the fibers 405 and 406 from the point of division in the coupler 404 to the respective retroreflectors 413 and 235 are slightly more than the size can distinguish the measured distance TS on the eye. It is used to tune the interferometric path difference in step sizes less than or equal to the coherence length and / or odd multiples of Aq / 2.
    The beams 410 and 411 reflected at the reflectors 413 and 235 are combined by the fiber coupler 404 and guided as a measuring double beam 420 from the fiber 406 to the coupling unit 52. The measuring double beam emerging from the fiber 406 is directed by the collimator 421 parallel to the interferometer input and, after passing through the plane plate 600, the beam splitter 210 and the partially transparent mirror 230, strikes the measuring object 240. There the double beam is partially reflected at all interfaces, as indicated in the figure 5 for the cornea front surface 241 and the fundus surface 242. The object double beams 426 and 427 reflected at these interfaces are reflected by the beam splitter 210 via the optics 254 to the detector array 246, superimposed there, and form a bright light spot (251, 262), in which the spatial Time Interferogram 252 can observe.
    Again, the respective position of the reference mirror of - corresponding to the prior art - encoders or displacement sensors to the computer 249 or another computer 290 is reported. Here, however, each reference mirror position already corresponds to a section length. This is calculated on the basis of the relationship between the position code and the metric mirror position and the result is displayed by the display 290. 15 Patent 50 • «* * * * * * t • # *« I * «II ·« I «·« fl · »·· *
    Again, one can shorten the reference mirror path, analogous to the arrangement in Figure 4, by a step reference mirror.
    FIG. 5 also indicates a computer 249 which controls the translation stage 236 and the actuator 237, registers their positions and performs the image processing described below on the measurement data recorded by the array 246.
    Because of the tissue pulsation, individual RZI from the two-dimensional detector array (246) must be recorded within a few milliseconds for all of the short-coherence interferometry techniques noted here (which is not technically significant). 6.3 Adjustment.
    Prerequisite for measurements is a measuring beam directed somewhat towards the center of the eye pupil. Otherwise, object beams reflected from the eye at a larger angle to the optical axis 239, for example the beam 261 in FIG. 2, miss the photo detector array 246. This is done with the aid of the detector array 246 positioned at the interferometer output on the associated monitor 250 of the monitor image 248 of the eye is first visually checked on the then observable light reflections (251, 262).
    A first step for interferometric matching is the overlapping of the object beams 243 and 244 with the reference beam 232 (or dual beams 426 and 427 in the case of the dual beam technique) on the detector array 246 (light spots 251 and 262) in the image 255 of the eye pupil 253 the monitor 250. This is achieved mainly by suitable positioning of the subject's eye. Particularly advantageous here is the arrangement according to FIG. 3, where the point of the eye pupil 253 illuminated by the measuring beam 231 is imaged onto the detector array 246 by means of the optics 254. If one still ensures that the reference beam 235 is reflected in itself by the reference mirror, a corresponding point of the reference beam on the detector array 246 is thus simultaneously imaged. In the dual-beam technique, the two double beams 426 and 427 reflected by the eye are imaged by the optics 254 from the pupil plane onto the detector array 246, which already largely ensures overlap there.
    In the second step for interferometric matching, the length of the reference beam is equal to the odd multiple of until the interference status in step sizes is reached
    16 patent 5D «« · λο / 2 to vote; An occurring RZI can be recognized visually on the monitor 250 as well as via an array image in the computer via image pattern recognition.
    Finally, the RZI and reference mirror positions are to be visually or computer detected in interference status at the translator's position transmitter and recorded by the computer 249 for further processing. Apart from a fixation light (such can be realized with the aid of a light source 451, as indicated in FIG. 4 and explained in more detail below), separate illumination of the eye is also helpful for these adjustment steps, for example by means of LED 260 via the partially transmissive 90 ° reflector 230th
    The need to maintain alignment for a longer period of time may be facilitated in the interferometry techniques used herein by using multiple light sources of different coherence lengths which illuminate the interferometer at the location of the individual light source 227 simultaneously or in chronological order. For example, one will first make an orienting measurement with a large coherence length to facilitate the adjustment and then perform a more accurate measurement with a small coherence length in the environment of the interferences. For this purpose, an arrangement is analogous to that indicated in the box 42 of Figure 4, in which case the light sources 401 and 402 have different coherence lengths. The same is achieved by means of a light source 227 with a variable coherence length.
    In all of the measuring arrangements for length measurement described here, a fixation light may also be required to stabilize the eye position. Such can be realized with the aid of a light source 451, whose light beam 450 is collimated by means of optics 452 into a parallel beam and directed to the eye via a cardanically mounted (partially indicated by 2 curved double arrows 454 and 455) 90 ° reflector 453 , This is indicated in FIG. By shifting the optic 452 in the beam direction, ametropia of the subject's eye 240 can be compensated. Such a fixation device can also be arranged in front of the subject eye in the other beam paths. 17 Patent 50
    6.4 Interferometric corneal topography based on the space-time domain interferometry.
    The above short-coherence interferometers can be used by adapting the interferometer illumination to the interferon-corneal topography. The basis for this is the RZI localized in or near the cornea as well as the interferogram difference image derived therefrom or the interferogram difference image: a. If the reference beam and the measuring beam are oriented approximately along the axis of the eye, the resulting RZI can easily be interpreted as a quasi-placido topogram or corneal contour image analogous to the classical Placido ring pattern. From this, after recording by the photodetector array 246 in the computer 249, the refractive power distribution of the cornea can be determined. However, with light from the most commonly used visible light or near infrared light, a very line-rich, hard-to-resolve topogram is obtained. b. In order to reduce its line density, according to the invention, the interferometer is illuminated simultaneously with light of several wavelengths, for example two (λχ and λ2), as indicated by the light sources 401 and 402 in the box 41 in FIG. The beams emitted by these (here 2) light sources are coupled collinearly by means of beam splitters 403. Similarly, based on the beam paths of Figures 2, 3 and 5 interferometer based on the corneal topography can be adjusted. Interferometer illumination with multiple wavelengths of light can also be realized by simultaneously illuminating the interferometer with multiple (two) medium wavelengths of light by means of multiple light sources (701, 702) connected by fiber couplers 700 (box 42 in FIG. 4).
    With light of two wavelengths one obtains an effective wavelength of Λ = λι.λ2 / | λι-λ2 |; For example, for the wavelengths 780 nm and 782 nm, an effective wavelength of * 0.3 mm with correspondingly reduced height layer line density. However, one first obtains a moiré pattern from the single interferograms; From this, spatial RZI can be obtained by spatial high-pass filtering, which corresponds to the effective wavelength Λ. The width of the height-layer lines can be reduced by using more than 2 light sources with different emission wavelengths for a more precise height characterization. c. The measuring beam diameter can be adapted to the corneal diameter by appropriately zooming the focal lengths of the telescope 229 of the interferometer illumination. 18 Patent 50 ··· * · · * · * «♦ * ·« t «· · * I i» * · »· t i * d. The depth measuring range can be adapted to the depth extent of the cornea by means of correspondingly long coherence lengths of the light source (227). This is possible for example by means of laser diodes whose coherence length increases with the strength of the pumping current. So you can realize with simple laser diodes a coherence length range of a few pm up to a few mm. Alternatively, a superluminescent diode with a very short coherence length (at position 401) and a laser diode with a large coherence length (at position 402) can also be illuminated simultaneously or alternately via a device as shown in box 41 of FIG. e. The RZI-based corneal topography can also be performed with the dual beam interferometer; In this case, the double beam illuminating the eye must have a path difference approximately equal to the axis of the eye in order to avoid interferogram interferences by - apart from the corneal reflex - other reflexes originating from larger intraocular surfaces.
    Because of the two orders of magnitude lower reflectivity of the rear in comparison to the anterior corneal surface, their Höhenschichtlinienbild does not bother. Non-rotationally symmetric RZIs that result from eccentric cornea illumination can be computationally transformed into easily interpretable rotationally symmetric quasi-placido topograms. 6.5 Measurement data acquisition and preprocessing. a. Measurement procedure (RZI-A-Scan). In the actual measurement process, the measurement path is tuned in steps of odd multiples of λο / 2 by means of a delay line, for example with a reference mirror (235, 340, 341), which is controlled by the computer 249 (in FIGS. 2, 3 and 4 in FIG z direction, in the figure 5 in the y direction). The computer 249 further controls the actuator (237, 339), registers the position of the reference mirror, registers the associated image data of the array detector 246, and executes the image processing described below. In order not to overlook interference status positions, it is necessary to register the RZI in path difference steps less than coherence length 61, or corresponding phase steps when using another delay line. b. Interference status. In the reflectometer technique, the optical distance of the reference mirror (235, 340, 341) from the beam splitter 210 and the optical distance of a patent 50
    In the dual-beam method, the path difference in the interferometer 51 coincides with the path difference between two light-reflecting points in the eye, the RZI 252 occurs at the detector array 246. The position of the respective reference mirror (in the case of interference status) is the "interference position". IP. This interferometric comparison is the basis for both the length measurement - where IP forms the result - as well as for the corneal topography - there is the RZI or form the RZI derived interferogram images at the IP for the cornea the result.
    In FIG. 3, the interference position of the reference mirrors is, for example, for the cornea front surface at position 235 'and for the fundus surface at position 235 " indicated. In FIG. 5, interference status is present when the path difference (2.WD) produced in the double beam 420 by the illuminating Michelson interferometer 51 is equal to the optical path difference of two eye structures. If the length of the reference beam is changed by other methods than moving the reference mirror, "reference position" means the phase equivalent to the reference beam length concerned.
    First, it is possible to visually recognize the interference status from the monitor image 248 while tuning the interferometric path difference by the occurrence of the RZI. Furthermore, the occurrence of the RZI in the interference status-in other words, the presence of interferometric matching-can be detected in the computer (249) in the pupil image registered by the detector array by means of digital image pattern recognition of line-like structures, for example with commercial software. It does not need to be searched for certain line patterns, but it is sufficient to determine the presence of line-like structures in general. For the length measurement, the respective reference mirror interference position IP, or in the topographic measurement, the RZI is registered by the computer 249. c. Interference status detection by coherent / incoherent discrimination. Visual and digital detection of an RZI can be accelerated by preprocessing the monitor image 248 by removing all incoherent image structures that are not caused by interference in the computer from the array image. According to the invention, this is achieved on the basis of the difference between each of the anti-phase array images. Forming the Pixel 20 Patent 50
    Difference of such array images, all pixels based on incoherent image portions disappear. Remaining pixels represent the interference term image of the RZI; the presence of which is to trigger the storage of the interference positions of the reference mirror (for example 235 'and 235 "in FIG. 3) supplied by positioners of the displacement units (236, 337), or the recording of the RZI in the interference positions for the topographic Measurement by computer 240 (possibly taking averaging over the RZI in the interference positions).
    Explanation. For the sake of simplicity, the intensities li of the reference beam and l2 of the object beam are set equal for the following principle consideration. According to the general law of interference, coherent superimposition of the reference beam and the object beam l2 with the intensities li or l2 at a point (ξ, η) of the array image yields the sum: 1 {ξ, η; Δφ) = Ιι (ξ, η) + Ι2 (ξ, η) + Μξ, η, Δφ). (2) 3ι2 (ξ, η; Δφ) = 2. [Ιι (ξ, η) .Ι2 (ξ, η] 1/2. Cos Δφ (3) is the interference term dependent on the phase difference Δφ of the 2 waves (M Born and E. Wolf, Principles of Optics, Cambridge University Press, Chapter 10), where for in-phase (phase difference rt) interference terms: Μξ, η, Δφ) = - .Ιι2 (ξ, η; Δφ + τι). (4)
    Difference and amount. If one takes the difference ΔΙ (ξ, η) of two antiphase interferograms whose phase differences Δφ differ by ix, one obtains the double interference term of the RZI, the interferogram difference image 256: ΔΙ (ξ, η) = Ι (ξ, η Δφ) - Ι (ξ, η; Δφ + n) = second reference term (of coherent origin). (5)
    On the other hand, the difference between two intensities of incoherent origin, such as the image of the eye outside the RZI, gives ΔΙ (ξ, η) = 0. (6)
    In the computer, the difference between two temporally short consecutive array images with antiphase RZI, but otherwise unchanged image structure, is formed: in this interferogram difference image disappear all pixels incoherent origin. This is illustrated in FIGS. 2, 3 and 5 in the sub-images 22, 32 and 53, in each case in the right-hand part of FIG.
    Column of the monitor images: upper field in interference status, lower field outside the interference status (256 = 2 x interference term, 247 = image part of incoherent origin.) These interferogram difference images can be obtained very quickly because all pixel operations (generation of the antiphase These images already allow a quick visual recognition of an interference status and also reduce the expense of digital image pattern recognition due to the reduced number of pixels remaining.
    Is the differential amount | ΔΙ (ξ, η) | antiphase space-time domain images, one obtains as a result the interferogram difference image, a slightly altered interferogram difference image (with double stripe density), which is characterized mainly by unipolar positive pixel values. The presence of the interferometric adjustment can first be detected by the occurrence of the interferogram difference amount image as described above for the interferogram difference image.
    Pixel sum RZI A-Scan signal. However, the interferogram difference amount image can do even more: If one forms the sum of the pixel values PS of the interferogram difference amount image along the respective path lengths, path differences or depth positions in the object and applies these pixel sums PS over the object depth position z, one obtains one Pixel sum RZI A-Scan signal - PS (z), which corresponds to the classical time-domain A-Scan signal. This signal can be "as usual". be used for length measurement. d. Display of the section length. The image signal occurring alone in the interferogram difference image and in the interferogram difference amount image in the case of interference status triggers read-out of the reference-mirror position in the computer 249. From these positions, the calculator calculates the link length based on the relationship between the position code and the metric position. This is displayed via monitor or separate display (290). The same applies to the pixel sum RZI A scan signal. This is also shown after conversion of the position code into metric positions, by monitor or separate display. 22 Patent 50
    6.6 Partial Length Measurement and Cornea Topography Using RZI Tomography.
    Here, RZI-A scans form the basis for a new OCT imaging process. Pixel sum signals from both the reflectometer and the dual beam method can be used as brightness values of laterally adjacent line elements for the synthesis of tomographic images as a function of the z position from adjacent (x- or y-direction) adjacent object zones. For this purpose, pixel sum RZI A scan signals PS (P) from the pixels of the interferogram difference images or the interferogram difference amount images along the reference mirror position P at the reflectometer or along the interferometer path difference WD in the dual beam method are suitable , These signals are obtained from laterally adjacent object zones and used as brightness values of laterally adjacent line elements for the synthesis of such images.
    For this purpose, the measuring beam 231 or, in the case of the dual beam technique, the measuring beam 420 is directed laterally in a temporally successive order onto the object and tuned. The easiest way to move laterally is achieved by a tiltable plane plate 600 in the illumination beam (such as in FIG. 5) or in the measurement beam (as in FIGS. 2, 3 and 4) interspersed by the relevant measuring beam and controlled by the computer 249, whose tilting axis is normal is oriented to the beam direction, as indicated by the double arrow 601. Alternatively, such a displacement is also achieved in that the measuring beam directed at the object first encounters a rotating mirror controlled by the computer 249 via a galvanometer drive, which is in the focus of an optical system which in turn moves the measuring beam parallel to the optical axis (239 ) is aimed at the measuring object (eye).
    These arrangements provide the data for sagittal RZI-based sectional images from cornea to fundus. Therefore, partial distance lengths can be derived from these images. Since a cross-sectional view of the eye is obtained in this procedure, additional evidence is obtained about the position of the measured partial sections or topographies. This may be crucial, especially for severe irregularities in the eye structure and in very fragile patients. 23 Patent 50 * ··· · ·· «* # · · * ·» M · «· · · · · ·« 7. On (ine and off line.
    The stated methods of length measurement and corneal topography can be done on-line in real time or with the aid of image memories or other image-recording aids or off line after the RZIs, interferogram difference images or the pixel sum RZI A-scan signal by computer have been stored. 8. Advantages achieved by the invention.
    Since the entire RZI is used, significantly more light is available than the previously used classical time-domain method with or without dual-beam technology. It can be expected with much greater sensitivity {- + 20dB). Furthermore, the often tedious search for the space interferogram within the eye pupil (or within its image), the subsequently required search for a suitable measuring point within the space interferogram, and the often hardly possible tracking of the photodetector after the measuring point are omitted. Another advantage is the common measuring principle for length measurement and topography. This makes it easy to implement both measurement methods in one device. Finally, the RZI signals can also form the basis for obtaining RZI-based tomographic images.
    This results in a very effective and adjustment-tolerant method. In particular, based on the dual-beam technique, a particularly effective and adjustment-insensitive eye-part measurement method can be realized, which also has the potential for implementing length measurement and corneal-tography in a hand-held device. 24 Patent 50
    权利要求:
    Claims (36)
    [1]
    ν 'ν' c · «· · # *« * »« * # * f «* ··· · · · ·« «· · · · · 4 * 9 * 4« («Dr. Adolf Friedrich Fercher, Hassreitersteig 3/11, 1230 Wien Patent Application: Methods and Arrangements for the Space-Time Domain Short-coherence Interferometry for Partial Ophthalmic Length Measurement and Corneal Topography PATENT REQUIREMENTS 1. Method for short-coherence interferometric length measurement on the eye, in which the eye is guided by a measuring beam is illuminated from the front and by an interferometric comparison of maturities or path lengths in the eye with known maturities or path lengths in the interferometer in the reflectometer technology, or of transit time differences or path length differences in the eye with known transit time differences or path length differences in the interferometer in the dual beam method, sections of the eye be measured, characterized in that the interferometric comparison using the space-time domain short-coherence inter ferogram (RZI) in the eye pupil, in its environment or a picture thereof.
    [2]
    2. A method for short-coherence interferometric length measurement on the eye, in which the eye is illuminated by a measuring beam from the front and by an interferometric comparison of maturities or path lengths in the eye with known maturities or path lengths in the interferometer in the reflectometer technology, or of transit time differences or Path length differences in the eye with known transit time differences or path length differences in the interferometer in the dual beam method, partial distances of the eye to be measured, characterized in that the interferometric comparison based on the occurrence of the space-time domain short-coherence interferogram (RZI) in the eye pupil, in their environment or a picture of it.
    [3]
    3. A method for short-coherence interferometric length measurement on the eye, in which the eye is illuminated by a measuring beam from the front and by an interferometric comparison of maturities or path lengths in the eye with known maturities or path lengths in the interferometer in the reflectometer technology, or of transit time differences or Path length difference in the eye with known transit time differences or path length differences in the interferometer in the dual beam method, partial distances of the eye to be measured, characterized in that the interferometric matching on the basis of a patent 50 difference image formed from two array images in or near the pupil plane of the illuminated Eye with antiphase space-time domain short-coherence interferograms (RZI) takes place.
    [4]
    4. A method for short-coherence interferometric length measurement on the eye, in which the eye is illuminated by a measuring beam from the front and by an interferometric comparison of maturities or path lengths in the eye with known maturities or path lengths in the interferometer bet the reflectometer technology, or of transit time differences or Path length differences in the eye with known transit time differences or path length differences in the interferometer in the dual beam method, partial distances of the eye to be measured, characterized in that the interferometric matching based on two array images in or near the pupil plane of the illuminated eye with antiphase space-time domain Short-coherence interferograms {RZI).
    [5]
    5. A method for short-coherence interferometric length measurement on the eye, in which the eye is illuminated by a measuring beam from the front and by an interferometric comparison of maturities or path lengths in the eye with known maturities or path lengths in the interferometer in the reflectometer technology, or of transit time differences or Path length differences in the eye with known transit time differences or path length differences in the interferometer in the dual beam method, partial distances of the eye to be measured, characterized in that the interferometric matching on the basis of the difference amount of two array images in or near the pupil plane of the illuminated eye with antiphase space-time Domain short-coherence interferograms (RZI).
    [6]
    6. A method for short-coherence interferometric length measurement on the eye, in which the eye is illuminated by a measuring beam from the front and by an interferometric comparison of maturities or path lengths in the eye with known maturities or path lengths in the interferometer in the reflectometer technique, or of transit time differences or Path length differences in the eye with known transit time differences or path length differences in the interferometer in dual beam method, partial distances of the eye to be measured, characterized in that the interferometric matching based on the pixel by pixel difference of two images of the illuminated eye with antiphase space-time domain short-coherence interferograms ( RZI) takes place in or near the pupil. 2 Patent SO 4 «* •« 4 ί * ♦ * * ♦ • * * ♦ • · ψ · »· · * · • # * I · • · ·» «
    [7]
    7. A method for short-coherence interferometric length measurement on the eye, in which the eye is illuminated by a measuring beam from the front and by an interferometric comparison of maturities or path lengths in the eye with known maturities or path lengths in the interferometer in the reflectometer technology, or of transit time differences or Path length differences in the eye with known transit time differences or path length differences in the interferometer in the dual beam method, partial distances of the eye are measured, characterized in that the interferometric matching based on the sum of the pixel values of the interferogram difference amount image of the illuminated eye with out of phase space-time Domain short-coherence interferograms (RZ1) takes place in or near the pupil.
    [8]
    8. An arrangement for short-coherence interferometric length measurement on the eye, according to the above claims, characterized in that a device is provided which changes the optical length of the measuring beam or the object beam or the reference beam by odd multiples of half the central wavelength.
    [9]
    9. An arrangement for short-coherence interferometric length measurement on the eye according to the above claims, characterized in that a displacement device for a mirror or reflector is provided which changes the optical length of the measuring beam or the object beam or the reference beam by odd multiples of half the central wavelength.
    [10]
    10. An arrangement for short-coherence interferometric length measurement on the eye according to the above claims, characterized in that a delay line is provided which changes the optical length of the measuring beam or the object beam or the reference beam by odd multiples of half the central wavelength.
    [11]
    11. Arrangement for short-coherence interferometric length measurement on the eye according to the above claims, characterized in that a two-dimensional detector array (246) is arranged in front of the eye pupil so that superimposed on it object reflected or backscattered object beams and reference beams interferometrically.
    [12]
    12. An arrangement for short-coherence interferometric length measurement on the eye according to the above claims, characterized in that between the two-dimensional detector array (246) and the eye pupil an optic (254) is arranged, which virtually in a plane 3 Patent 50 • # · »» Ft ft ft ft ft · · · · · · · · · C C C C · · ·,,,,,,,,,,,,,,,,,,,,,,. 253) images the interferogram occurring on the detector array.
    [13]
    13. An arrangement for short-coherence interferometric length measurement on the eye according to the above claims, characterized in that a staircase-shaped reference mirror with offset in the beam direction mirror stages (340, 341) is provided, meets on the different stages of the reference beam during the tuning of its length.
    [14]
    14. An arrangement for short-coherence interferometric length measurement on the eye according to the above claims, characterized in that a monitor 250 is provided which makes the pupil image registered by a detector array (246) visible, so that the presence of the interferometric matching by the occurrence line-like structures in the overlap region (251, 262) of object and reference beam in the image 255 of the eye pupil 253 can be visually detected.
    [15]
    15. Arrangement for short-coherence interferometric length measurement on the eye according to claims 1 to 13, characterized in that a computer (249) is arranged, which with software for digital image pattern recognition of line-like structures on the pupil image registered by the detector array (246), the presence of Determines interference status.
    [16]
    16. A method for short-coherence interferometric length measurement on the eye according to the above claims 1 to 13, characterized in that the presence of the interferometric matching using an RZI-A-scan signal, formed as a sum of the pixel values of the interferogram difference amount image plotted above the object depth position, visually detected by monitor or in the computer.
    [17]
    17. A method for short-coherence interferometric length measurement on the eye according to the above claims 1 to 13, characterized in that from two short consecutive antiphase array images, a difference image or a difference amount image is calculated and that the remaining at interference status image signal that Reading the reference mirror position triggers and causes its conversion to metric sizes and subsequent presentation in a display (290).
    [18]
    18. Method of space-time domain Short-coherence interferometric length measurement according to claims 1 to 13, characterized in that the optical compensation based on the 4 patent 50th

    Sum of the pixel values of the interferogram difference amount image along the respective path lengths, path differences or depth positions in the object is assessed.
    [19]
    19. Arrangement for optical partial length measurement on the eye according to the above claims, characterized in that in the reference beam path devices from deflecting mirrors and retroreflectors (234, 235, 334, 340, 341, 413) on displacement units (236, 237, 337, 338, 339) are arranged, which the deflecting levels! and Retroreflektoren stepwise, in particular by odd multiples of a quarter of the central wavelength, move in the beam direction.
    [20]
    20. Arrangement for optical partial length measurement on the eye according to the above claims, characterized in that devices in the measuring beam path from deflecting mirrors and retroreflectors (234, 235, 334, 340, 341) on displacement units (236, 237, 337, 338, 339) are arranged, which shift the deflecting mirrors and retroreflectors stepwise, in particular by odd multiples of a quarter of the central wavelength in the beam direction.
    [21]
    21. Arrangement for optical partial length measurement on the eye according to the above claims, characterized in that a light source (227) with high spatial coherence and variable coherence length are provided as the interferometer illumination.
    [22]
    22. Arrangement for optical partial length measurement on the eye according to the above claims, characterized in that two or more discrete light sources (401, 402, 701, 702) with high spatial coherence and different coherence lengths are provided as the interferometer illumination.
    [23]
    23. A method of corneal topography for measuring the shape and refractive power distribution of the cornea, characterized in that the cornea-topographic shape and refractive power measurement on the basis of a space-time domain short-coherence interferogram (RZI) is carried out in the cornea.
    [24]
    24. Method of the space-time domain Short-coherence interferometric corneal topography according to claim 23, characterized in that the optical compensation is determined on the basis of the occurrence of an interferogram difference image of the RZI with its surroundings. 5 Patent 50 • i:. :: :: .. = ....... "
    [25]
    25. Method of the space-time domain Short-coherence interferometric corneal topography according to claim 23, characterized in that the optical compensation is determined on the basis of the occurrence of an interferogram difference-amount image of the RZI with its surroundings.
    [26]
    26. Method of the space-time domain Short-coherence interferometric corneal topography according to claim 23, characterized in that the optical compensation is determined on the basis of the sum of the pixel values of the interferogram difference-sum image.
    [27]
    27. Method of the space-time domain Short-coherence interferometric corneal topography according to the above claims, characterized in that the optical compensation is evaluated on the basis of the sum of the pixel values of the interferogram difference-sum image along the respective path lengths, path differences or depth positions in the object ,
    [28]
    28 arrangement for short-coherence interferometric corneal topography according to claims 23 to 27, characterized in that at the Interferometereingang a zoomable telescope (229) is provided which adapted by zooming its focal lengths the measuring beam diameter of the interferometer illumination to the cornea diameter.
    [29]
    29. An arrangement for short-coherence interferometric corneal topography on the eye according to claims 23 to 27, characterized in that a delay line is provided for the reference beam and / or the measuring beam whose length can be locked in discrete positions so that the RZI in the cornea can be located.
    [30]
    30. Arrangement for short-coherence interferometric corneal topography according to claims 23 to 29, characterized in that in the dual beam interferometer, the tuning of the path differences causing retroreflector (235) can be set to a path difference of about eye axis length of each patient fixed ,
    [31]
    31. An arrangement for short-coherence interferometric corneal topography according to claims 23 to 30, characterized in that the interferometer input a beam splitter is provided, via which the interferometer simultaneously with light from a plurality, in particular two sources (401,402), with different average wavelength, is illuminated. 6 Patent 50

    • *
    [32]
    32. Arrangement for short-coherence interferometric corneal topography according to claims 23 to 30, characterized in that the interferometer input is illuminated by light of a plurality of medium wavelengths, which is combined by fiber coupler (700) from a plurality of light sources (701, 702).
    [33]
    33. Method of the space-time domain Short-coherence interferometric length measurement and corneal topography based on the interferometric comparison using the space-time domain short coherence interferogram (RZI), characterized in that the reflectometer or the dual beam method pixel sum RZI -A scan signals depending on the object depth or z position from the side (x or y direction) adjacent object zones are used as brightness values for laterally adjacent line elements for the synthesis of tomographic images from which in the computer (246) or from the From this generated tomographic image the desired intraocular distances can be obtained.
    [34]
    34. Arrangement for short-coherence interferometric corneal topography according to claim 33, characterized in that the measuring object illuminating measuring beams (231, 420) controlled by the computer (249) tiltable plane plate (600) whose tilt axis (601) normal to Beam direction is oriented to transversely adjacent positions on the measuring object (eye).
    [35]
    35. An arrangement for short-coherence interferometric corneal topography according to claim 33, wherein a rotating mirror controlled by a computer via a galvanometer drive is provided in the focus of an optic which illuminates the measuring beams (231, 420 ) is directed parallel to the optical axis (239) to transversely adjacent positions on the measurement object (eye).
    36. Arrangement for short-coherence interferometric length measurement and corneal topography on the eye, according to the above claims, characterized in that a device (43) for observing the space-time domain short-coherence interferograms (RZI) and the associated environment on the eye provided is. 7 Patent 50
    [36]
    36. Arrangement for short-coherence interferometric partial distance measurement and corneal topography according to the above claims, characterized in that both measurements are carried out with the same interferometer. 8 Patent SO
    类似技术:
    公开号 | 公开日 | 专利标题
    EP2346386B1|2013-04-10|Optical coherence reflectometry with depth resolution
    EP1232377B1|2004-03-31|Method and device for measuring the optical properties of at least two regions located at a distance from one another in a transparent and/or diffuse object
    EP1494575B1|2007-09-19|Measurement of optical properties
    EP2367469B1|2017-10-25|Device and method for swept-source optical coherence domain reflectometry
    DE19624167B4|2007-07-19|Coherence Biometry and Tomography with Dynamic Coherent Focus
    EP1959816B1|2011-07-20|Interferometric sample measurement
    CH697225B1|2008-07-31|A process for obtaining tomograms topographs and the eye structure.
    EP2799002B1|2020-04-29|Method and analysis system for performing ophthalmic examinations
    US10398306B2|2019-09-03|Optical imaging device and method for imaging a sample
    DE102010051281A1|2012-05-16|Method for the model-based determination of the biometry of eyes
    WO2012084170A9|2013-06-20|Device for interferometrically measuring the eye length and the anterior eye segment
    WO2011137985A1|2011-11-10|System for the improved imaging of eye structures
    DE102011011277A1|2012-08-16|Optimized device for swept source Optical Coherence Domain Reflectometry and Tomography
    EP0563454A1|1993-10-06|Method and apparatus for investigating the eyes
    AT511740B1|2014-02-15|PROCEDURE AND ARRANGEMENTS FOR SPACE-TIME DOMAIN SHORT COHERENCE INTERFEROMETRY FOR OPHTHALMOLOGICAL PARTIAL LENGTH MEASUREMENT AND CORNEA TOPOGRAPHY
    EP3585245A1|2020-01-01|Method and arrangement for high-resolution topography of the cornea of an eye
    WO2008151821A1|2008-12-18|Device and method for determining the anterior chamber depth and eye length of an eye
    EP2384692A1|2011-11-09|Method and device for interferometry
    WO2017191128A1|2017-11-09|Ophthalmological length measurement by means of dual-beam space-time domain wavelength tuning low-coherence interferometry
    EP1969995A1|2008-09-17|Eye testing device
    DE102012011880A1|2013-07-18|Contactless measuring device for ophthalmic calculation and selection of intraocular lenses, has keratometer arrangement that is provided for determining corneal curvature of eye
    JP2019063242A|2019-04-25|Oct apparatus and ophthalmologic image processing program
    AT507140B1|2013-03-15|MULTIPLE-A-SCAN SHORT COHERENCE INTERFEROMETRIC DISTANCE MEASUREMENT AT EYE
    AT511014B1|2014-02-15|OPTICAL ADAPTER FOR A DOUBLE JETTING SHORT COHERENCE INTERFEROMETRY PROCEDURE AND ARRANGEMENT FOR INTRAOCULAR DISTANCE MEASUREMENT
    DE10113070A1|2002-06-06|Apparatus for tomography- and topography measurement of the eye, employs short-coherence interferometer measurement beam with focusing- and scanning optics
    同族专利:
    公开号 | 公开日
    AT511740A3|2014-02-15|
    AT511740B1|2014-02-15|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    AT518602A1|2016-05-03|2017-11-15|Friedrich Dr Fercher Adolf|Ophthalmic length measurement using a double-beam space-time domain Wavelength Tuning Short-coherence interferometry|DE102008029479A1|2008-06-20|2009-12-24|Carl Zeiss Meditec Ag|Short-coherence interferometry for distance measurement|DE102016218290A1|2016-07-15|2018-01-18|Carl Zeiss Meditec Ag|Method for the highly sensitive measurement of distances and angles in the human eye|
    法律状态:
    2017-03-15| MM01| Lapse because of not paying annual fees|Effective date: 20160718 |
    优先权:
    申请号 | 申请日 | 专利标题
    AT10542011A|AT511740B1|2011-07-18|2011-07-18|PROCEDURE AND ARRANGEMENTS FOR SPACE-TIME DOMAIN SHORT COHERENCE INTERFEROMETRY FOR OPHTHALMOLOGICAL PARTIAL LENGTH MEASUREMENT AND CORNEA TOPOGRAPHY|AT10542011A| AT511740B1|2011-07-18|2011-07-18|PROCEDURE AND ARRANGEMENTS FOR SPACE-TIME DOMAIN SHORT COHERENCE INTERFEROMETRY FOR OPHTHALMOLOGICAL PARTIAL LENGTH MEASUREMENT AND CORNEA TOPOGRAPHY|
    [返回顶部]