Optical coherence metrology and tomography with improved recording

Abstract

Methods and apparatus are provided for optical coherence metrology or tomography with improved registration across an extended region of an eye. At least two optical coherence tomographic images are acquired, where each tomographic image contains data from at least partially overlapping regions of the anterior surface of the eye, and data from one or more deeper structures such as the retina or the anterior or posterior lens surface. The tomographic images are then processed to register the data from the overlapping portions of the anterior surface regions, thereby registering the data from the deeper structures. In certain embodiments, the reference arm of the apparatus includes a compound reflector having at least two axially separated reflective surfaces for applying differential delays to different portions of the reference beam. The depth of field of the apparatus is thereby extended to enable measurement of the length of the eye. In certain embodiments, measurement of the length of the eye at multiple angles of incidence provides information about the overall shape of the eye.

Description

[0001] This application is a divisional application of the Chinese national phase application of PCT application filed on January 20, 2018, with international application number PCT / AU2018 / 050038 and invention title "Optical Coherence Metrology and Tomography with Improved Recording". The Chinese national phase application entered the Chinese national phase on August 14, 2019, with application number 201880011934.1.

[0002] Cross-references to related applications

[0003] This application claims priority to Australian Provisional Patent Application No. 2017900245, filed on January 28, 2017, entitled “Optical Coherence Metrology and Tomography with Improved Registration,” the contents of which are incorporated herein by reference. Technical Field

[0004] This invention relates to apparatus and methods for ocular metrology, and more particularly for measuring the shape of the human eye using optical coherence tomography (OCT) technology. However, it will be understood that the invention is not limited to this particular field of application. Background Technology

[0005] Any discussion of prior art throughout the specification should never be considered an admission that such prior art is well-known or forms part of common knowledge in the art.

[0006] Measurements of many (if not all) optical surfaces of the human eye, as well as the overall shape of the eye, provide important information about the progression of various diseases and conditions. Specifically, myopia development has become an area of ​​particular concern due to the rapid increase in the prevalence of myopia, particularly in East Asia. In a Nature News feature entitled “The Myopia Boom,” E. Dolgin, Nature 519, 276-278, March 2015, it was reported that the prevalence of myopia (i.e., nearsightedness) in China rose from less than 20% of the population to approximately 90% of young adults and adolescents in 60 years. This condition can lead to deformation and thinning of the inner eye, increasing the incidence of retinal detachment, cataracts, glaucoma, and blindness. The gold standard for the challenging task of measuring overall eye shape is magnetic resonance imaging (MRI), as described, for example, in “Eye Shape in Emmetropia and Myopia” by Atchison et al. (Investigative Ophthalmology & Visual Science 45(10), 3380-3386, October 2004). However, MRI requires expensive and complex equipment and lacks the accuracy needed to track small developmental changes over weeks and months.

[0007] Measuring eye shape using optical techniques would be appealing. Optical coherence tomography (OCT) is a widely used interferometric technique used to study biological samples, including in vivo tissues such as the human eye, with lateral and depth resolution using information contained within the amplitude and phase of reflected or scattered light. While spectral-domain OCT has proven effective in providing measurements of individual eye layers and depths, existing OCT techniques are not well-suited for obtaining accurate information about the overall eye shape for several reasons. One reason is the difficulty in measuring eye length (defined as the distance between the corneal apex and the fundus) in a single exposure. This is because the size of an adult eye is typically around 20 mm, significantly exceeding the depth of field or Nyquist range of typical spectral-domain OCT systems. [The last sentence appears to be incomplete and possibly refers to a separate topic:] Having [something] in the dispersion direction... N Depth of field measurement system using a detector array of individual pixels or photodiodes and a light source with a center wavelength λ and a half-width Δλ. Z Depend on Z = N ·λ 2 / (4·Δλ) is given. Therefore, it has NA system with a value of 1000, λ = 840 nm, and Δλ = 40 nm would have a measurement depth of approximately 4.4 mm, much smaller than the typical eye length. A fundamental problem is the need for a wide source bandwidth (i.e., a large Δλ) to provide the short coherence length required for depth resolution, but for a given detector array, this limits the depth range at which the sample beam can interfere with the reference beam.

[0008] U.S. Patent No. 7,982,881, entitled "Apparatus and method for interferometric measurement of a sample," discloses several techniques for extending the axial depth of an OCT system by providing multiple reference paths that can be interfered with by light reflected from different depths of the eye. This allows for axial measurements at multiple points at different depths. However, due to limitations in maximum exposure or available optical power in clinical settings, measurements cannot always be obtained within a sufficiently short time period (i.e., less than a few milliseconds) to prevent eye movement. This is especially important when relative accuracy of a few micrometers or smaller is required between many lateral sampling points. Patent No. 7,982 does not provide any guidance on how to achieve high signal-to-noise ratio measurements when sampling over a large area of ​​the eye, because it is not possible to calculate the lateral and axial positions of the eye from a limited dataset to accurately co-record the lateral and axial positions on the eye of the various enhanced axial scans described. Therefore, several important optical properties of the eye cannot be calculated from the obtained set of axial scans. For example, when planning intraocular lens (IOL) surgery, it is often advantageous to know accurately the optical power and astigmatism of the anterior and posterior corneal surfaces, as well as the axial length and lens thickness and curvature.

[0009] U.S. Patent No. 8,534,838, entitled "Optical coherence reflectometry with depth resolution," describes an apparatus using a "birefringent optical system" designed to simultaneously project line focal points onto the eye and retina, and similarly onto two reference paths of different lengths. All four returning line focal points are combined, stray light is suppressed through a slit aperture, and then dispersed onto a 2-D sensor array. The "birefringent optical system" can be polarization-based (e.g., using birefringent lenses) or diffraction-based (e.g., using a diffractive optical system). While line scanning systems allow for positioning of the scan location on the cornea along one axis to some extent, it is not possible to definitively ensure the slice position for recording a series of slices to construct a more complete and correctly recorded image of the optical interface in the eye. Furthermore, while the slit aperture provides high-resolution axial scanning, it does not provide a means of removing crosstalk from different lateral locations. In particular, in areas of the human cornea where high-intensity specular reflections transform into low-intensity scattering, it is difficult to prevent excessive lateral crosstalk from high-intensity areas and the disruption of results from adjacent points at different depths. Therefore, it would be advantageous to provide a recording method that overcomes crosstalk limitations by providing openings around the point of interest, and also to provide a three-dimensional point grid for recording, thereby enabling the construction of high signal-to-noise ratio images.

[0010] The ability of OCT to measure overall eye shape is also affected by the eye's focusing ability. For example, small-beam arrays designed to measure lateral resolution features at the posterior part of the eye (e.g., the retina) are unsuitable for creating feature maps at the anterior part of the eye (e.g., the cornea). To form small beams at the retina, the cornea must be irradiated with a collimated beam, which lacks the precision required for mapping the anterior surface of the eye. Furthermore, parallel-beam arrays used to measure the anterior portion of the eye will focus on a single area of ​​the retina and therefore cannot provide a topographic map of the posterior part of the eye. An additional difficulty in measuring eye shape using OCT is that the apparent curvature of the retina is affected by the position of the OCT instrument relative to the eye. Therefore, improved OCT systems and methods are needed for measuring overall eye shape.

[0011] Unless the context explicitly requires otherwise, throughout the specification and claims, the words “comprising,” “including,” etc., should be interpreted in an inclusive sense, rather than an exclusive or exhaustive sense. That is, they should be interpreted as “including but not limited to.”

[0012] Purpose of the invention

[0013] One object of the present invention is to overcome or improve upon at least one limitation of the prior art, or to provide a useful alternative. Another object of the present invention is to provide, in a preferred form, a spectral-domain OCT apparatus and method capable of measuring the overall shape of the eye. Yet another object of the present invention is to provide, in a preferred form, a spectral-domain OCT apparatus and method for ocular metrology or tomographic imaging with improved recording capabilities. Summary of the Invention

[0014] According to a first aspect of the present invention, a method for performing optical coherence metrology across an extended region of the eye is provided, the method comprising the following steps:

[0015] (i) Acquire a first optical coherence tomography image of the eye within a single frame of a two-dimensional sensor array, the first optical coherence tomography image containing data from a first region of the anterior surface of the eye and data from a third region of the eye;

[0016] (ii) Acquiring a second optical coherence tomography (OCT) image of the eye within a single frame of the two-dimensional sensor array, the second OCT image comprising data from a second region of the anterior surface that at least partially overlaps with the first region and data from a fourth region of the eye; and

[0017] (iii) Process the first optical coherence tomography image and the second optical coherence tomography image to record the overlapping portion of the first and second regions of the anterior surface, thereby recording data from the third and fourth regions of the eye.

[0018] Preferably, at least one of the first and second regions of the anterior surface includes a portion of the anterior sclera. More preferably, at least one of the first and second regions of the anterior surface includes a portion of the limbus.

[0019] Each of the first optical coherence tomography (OCT) image and the second OCT image is preferably acquired within a time period of 2 milliseconds or less, more preferably within a time period of 1 millisecond or less, and even more preferably within a time period of 100 microseconds or less.

[0020] Each of the first and second optical coherence tomographic images preferably contains data from a plurality of discrete points within a corresponding region of the anterior surface. In some embodiments, each of the third and fourth regions of the eye includes a region of the retina. In other embodiments, each of the third and fourth regions of the eye includes a plurality of discrete points on the retina.

[0021] In some embodiments, the position of the apparatus for acquiring the first and second optical coherence tomographic images is adjusted relative to the eye between the acquisition of the first and second optical coherence tomographic images. In other embodiments, the internal delay in the apparatus for acquiring the first and second optical coherence tomographic images is adjusted between the acquisition of the first and second optical coherence tomographic images. In still other embodiments, one or more lenses in the apparatus for acquiring the first and second optical coherence tomographic images are varied between the acquisition of the first and second optical coherence tomographic images.

[0022] In some embodiments, the method further includes the step of applying a predetermined optical path length difference on a laterally spaced first portion and a second portion of a reference beam or a sample beam while acquiring at least one of a first optical coherence tomography image and a second optical coherence tomography image, wherein the processing step further includes taking into account the predetermined optical path length difference. The predetermined optical path length difference is preferably applied on the laterally spaced first portion and the second portion of the reference beam. More preferably, the predetermined optical path length difference is applied by a composite reflector having axially separated first and second reflective surfaces for reflecting the laterally spaced first and second portions of the reference beam.

[0023] According to a second aspect of the invention, an apparatus is provided for performing optical coherence metrology across an extended region of the eye, the apparatus comprising:

[0024] An interferometer is used to acquire a first optical coherence tomography (OCT) image and a second OCT image of an eye within a single frame of a two-dimensional sensor array. The first OCT image contains data from a first region of the anterior surface of the eye and data from a third region of the eye, and the second OCT image contains data from a second region of the anterior surface and data from a fourth region of the eye, wherein the first and second regions at least partially overlap.

[0025] A computer is used to process a first optical coherence tomography (OCT) image and a second OCT image to record the overlapping portion of a first region and a second region of the anterior surface, thereby recording data from a third region and a fourth region of the eye.

[0026] Preferably, the interferometer is configured such that, in use, at least one of the first and second regions of the anterior surface includes a portion of the anterior sclera. More preferably, the interferometer is configured such that, in use, at least one of the first and second regions of the anterior surface includes a portion of the limbus. In some embodiments, the interferometer is configured such that, in use, each of the third and fourth regions of the eye includes a region of the retina.

[0027] The device is preferably configured such that each of the first optical coherence tomography image and the second optical coherence tomography image can be acquired within a time period of 2 milliseconds or less, more preferably within a time period of 1 millisecond or less, and even more preferably within a time period of 100 microseconds or less.

[0028] Preferably, the interferometer includes a spatial sampling element for providing an array of small beams, such that in use, each of the first and second optical coherence tomography (OCT) images contains data from a plurality of discrete points in a corresponding region of the anterior surface. In some embodiments, the spatial sampling element is configured to provide focusing of different small beams at different depths in the eye. The spatial sampling element preferably comprises a two-dimensional microlens array. In some embodiments, the device further includes a structured aperture septum for suppressing crosstalk between small beams returning from the eye. The structured aperture septum preferably includes a first member having a plurality of apertures for allowing on-axis small beams returning from the eye to pass through. More preferably, the structured aperture septum includes a second member extending substantially parallel to the propagation direction of the on-axis small beams for suppressing the passage of off-axis light. In some embodiments, the interferometer and the spatial sampling element are configured such that in use, each of the third and fourth regions of the eye includes a plurality of discrete points on the retina.

[0029] In some embodiments, the interferometer includes one or more lenses adapted to interchange between acquiring a first optical coherence tomography image and acquiring a second optical coherence tomography image.

[0030] In some embodiments, the interferometer includes a multi-length delay element for applying a predetermined optical path length difference over laterally spaced first and second portions of a reference beam or sample beam when acquiring at least one of a first optical coherence tomography (OCT) image and a second OCT image, wherein a computer is configured to take the predetermined optical path length difference into account when processing the respective OCT image. The multi-length delay element is preferably configured to apply the predetermined optical path length difference over the laterally spaced first and second portions of the reference beam. More preferably, the multi-length delay element includes a composite reflector having axially separated first and second reflective surfaces for reflecting the laterally spaced first and second portions of the reference beam. In a preferred embodiment, the composite reflector includes a medium selected to have dispersion that at least partially compensates for the dispersion of the eye. Preferably, the composite reflector is selected such that the predetermined optical path length difference substantially compensates for the axial depth of the eye.

[0031] According to a third aspect of the present invention, a method for measuring eye shape is provided, the method comprising the following steps:

[0032] (i) In the first acquisition, an optical coherence tomography apparatus with a first optical repeater is used to measure the anterior segment of the eye and the axial depth of the eye;

[0033] (ii) Calculate the refractive characteristics of the anterior segment of the eye based on the data obtained in the first acquisition;

[0034] (iii) In the second acquisition, the optical coherence tomography apparatus having a second optical repeater calibrated to the first optical repeater is used to capture an image of the retina of the eye on a dot grid;

[0035] (iv) Determine the axial and angular positions of the second acquisition relative to the first acquisition; and

[0036] (v) Using the calculated refractive properties of the anterior segment of the eye, determine the corrected retinal shape based on a correction formula or by using an optical model.

[0037] Preferably, the anterior segment is measured simultaneously on a dotted grid during the first acquisition. The axial depth is preferably measured to the retinal pigment epithelium at the fovea of ​​the eye. Preferably, the fovea of ​​the eye is identified from an image of the retina.

[0038] According to a fourth aspect of the present invention, an optical coherence tomography apparatus for measuring the shape of an eye is provided, the apparatus being configured to:

[0039] In the first acquisition using the first optical repeater, the anterior segment of the eye and the axial depth of the eye are measured;

[0040] The refractive characteristics of the anterior segment of the eye are calculated based on the data obtained in the first acquisition;

[0041] An image of the eye's retina is captured on a dot grid during a second acquisition using a second optical repeater calibrated to the first optical repeater;

[0042] Determine the axial and angular positions of the second acquisition relative to the first acquisition; and

[0043] Using the calculated refractive properties of the anterior segment of the eye, the corrected retinal shape is determined based on a correction formula or by using an optical model.

[0044] The device is preferably configured to simultaneously measure the anterior segment on a dotted grid during the first acquisition. Preferably, the device is configured to measure the axial depth of the retinal pigment epithelium up to the fovea of ​​the eye. Preferably, the device is configured to identify the fovea of ​​the eye from an image of the retina.

[0045] According to a fifth aspect of the present invention, a method for performing optical coherence metrology or tomographic imaging of a sample is provided, the method comprising the following steps:

[0046] (i) Split the light from the light source into a sample beam and a reference beam;

[0047] (ii) Apply a predetermined optical path length difference to the first and second portions of the sample bundle or the reference bundle that are laterally spaced apart;

[0048] (iii) Guide the sample bundle onto the sample to interact with the axially separated first and second regions of the sample, and collect light reflected or transmitted from the axially separated first and second regions of the sample;

[0049] (iv) Mix the reference beam with reflected or transmitted light;

[0050] (v) Detecting the interference signal generated by the mixing of the reference beam with reflected or transmitted light; and

[0051] (vi) Process the detected interference signal to provide an optical coherence tomography image of the sample.

[0052] The predetermined optical path length difference at least partially compensates for the axial spacing between the first and second regions of the sample.

[0053] Preferably, the sample beam comprises an array of small beams for interacting with multiple discrete points within a first or second region of the sample. A predetermined optical path length difference is preferably applied to laterally spaced first and second portions of the reference beam. More preferably, the predetermined optical path length difference is applied by a composite reflector having axially separated first and second reflective surfaces for reflecting the laterally spaced first and second portions of the reference beam.

[0054] According to a sixth aspect of the present invention, an apparatus for performing optical coherence metrology or tomographic imaging of a sample is provided, the apparatus comprising:

[0055] light source;

[0056] Interferometer, used for:

[0057] The light from the light source is split into a sample beam and a reference beam;

[0058] The sample beam is guided onto the sample to interact with axially separated first and second regions of the sample, and to collect light reflected or transmitted from the axially separated first and second regions of the sample; and

[0059] The reference beam is mixed with reflected or transmitted light;

[0060] A detector is used to detect interference signals generated by the mixing of a reference beam with reflected or transmitted light;

[0061] A multi-length delay element for applying a predetermined optical path length difference on a laterally spaced first and second portion of the sample beam or the reference beam; and

[0062] A processor is used to process the detected interference signals to provide an optical coherence tomography image of the sample.

[0063] The multi-length delay element is selected such that the predetermined optical path length difference at least partially compensates for the axial spacing between the first and second regions of the sample.

[0064] The device preferably includes a spatial sampling element for generating a small array of beams from a sample beam for interacting with multiple discrete points within a first or second region of the sample. Preferably, the spatial sampling element includes a microlens array. In a preferred embodiment, a multi-length delay element is configured to apply a predetermined optical path length difference over laterally spaced first and second portions of a reference beam. Preferably, the multi-length delay element includes a composite reflector having axially separated first and second reflective surfaces for reflecting the laterally spaced first and second portions of the reference beam. The multi-length delay element preferably includes a medium selected to have dispersion that at least partially compensates for the dispersion of the sample.

[0065] According to a seventh aspect of the invention, an article of manufacture is provided, comprising a computer-usable medium having computer-readable program code configured to implement the method according to the first, third, or fifth aspect, or to operate the apparatus according to the second, fourth, or sixth aspect. Attached Figure Description

[0066] Preferred embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, wherein the same reference numerals are used in different drawings to indicate similar or identical items or features.

[0067] Figure 1A A spectral-domain OCT device for ocular metrology or tomographic imaging with intraocular interface recording, according to an embodiment of the present invention, is illustrated in schematic form.

[0068] Figure 1B It shows Figure 1A It is part of the reference arm of the spectral domain OCT device, in which the compound mirror is in a "plane" position rather than a "hole" position.

[0069] Figure 1C The schematic floor plan shows the use of Figure 1A The device allows for advantageous positioning of 2-D sample bundle arrays on the pupil, iris, and anterior sclera of the sample eye.

[0070] Figure 2A Depicting the use Figure 1A A flowchart of a method for constructing a synthetic image of an eye using a device.

[0071] Figure 2B Depicting the use Figure 1A A flowchart of another method for constructing synthetic images of eyes using a device.

[0072] Figure 2C The partial overlap of the sample illuminated by the 2-D small beam array in a separate measurement is shown in schematic form.

[0073] Figure 3 A schematic oblique view shows the use of Figure 1A An alternative lighting system for the device.

[0074] Figure 4 The sample arm optics of an OCT device according to an embodiment of the present invention are shown in schematic form.

[0075] Figure 5A The sample arm optics of an OCT device according to another embodiment of the present invention are shown in schematic form.

[0076] Figure 5B It shows Figure 5A The image shows an enlarged view of the opening portion of the sample arm optics.

[0077] Figure 6 Depicting the use Figure 1A The flowchart shown illustrates a method for measuring the eye at different incident angles using the apparatus.

[0078] Figure 7A The projection of three combined beams onto a 2-D sensor array is shown in schematic form.

[0079] Figure 7B It shows that for Figure 7A The graphs showing the intensity of different pixel rows versus the number of pixels in one of the beam projections of a 2-D sensor array illustrate the effect of pixel saturation.

[0080] Figure 8 The “B scan”, a coarse sample of the anterior segment of the sample eye, is shown, which consists of a row of 56 A scans at a 0.3 mm spacing extracted from one of 144 frames of a set of raster scans.

[0081] Figure 9A and Figure 9B Typical A-scan curves of the cornea and anterior sclera of the eye are shown respectively.

[0082] Figure 9C The filter templates derived from multiple A-scans of the anterior sclera of the eye are shown.

[0083] Figure 10 The grid positions of multiple A-scans on the anterior sclera on both sides of the cornea are depicted schematically.

[0084] Figure 11 The translation vector used to record data acquired from a sample eye across 144 frames of a set of raster scans is shown.

[0085] Figure 12 It shows the use of Figure 11The translation vector shown was extracted from a volume-averaged dataset obtained from 144 frames. Figure 8 B-scan of the sample eyes.

[0086] Figure 13A The “B scan” shows a coarse sample of the lens region of the sample eye, which consists of a row of 56 A scans at a 0.3 mm pitch extracted from one of 144 frames of a set of raster scans.

[0087] Figure 13B The figure shows the extraction from the volume average dataset obtained from 144 recorded frames. Figure 13A B-scan of the sample eye, showing the anterior and posterior lens surfaces.

[0088] Figure 14 This demonstrates the results obtained by jointly recording two separate volume average datasets. Figure 13A Another B-scan of the sample eye, the dataset was obtained by changing the instrument position to focus at different depths.

[0089] Figure 15 This demonstrates the use of classical geometric optics to determine the apparent shape of the retina based on the instrument position, allowing for correction of the effects of the OCT instrument's position relative to the eye.

[0090] Figure 16 The diagram shows a correction term for axial depth calculated using a ray tracing algorithm, used to correct for changes in instrument position to adjust for retinal shape.

[0091] Figure 17 A flowchart is depicted for an improved measurement used to determine eye shape, in which the influence of the instrument's position relative to the eye is corrected.

[0092] Figure 18A and Figure 18B Two variants of a transmission multi-length delay element for applying differential delay to different portions of a sample bundle or sample bundle array are shown in schematic form. Detailed Implementation

[0093] The first aspect of the invention relates to a spectral domain OCT apparatus and method with increased depth of field, and in particular to a spectral domain OCT apparatus and method with sufficient depth of field for single-shot measurements of eye structure and including parameters such as eye length. Figure 1AA spectral domain OCT device 100 according to a first embodiment of the present invention is illustrated schematically. This device is suitable for intraocular metrology or tomography recording intraocular structures such as the anterior lens surface 102 or posterior lens surface 103 or choroid 104 to anterior sclera 106 of a sample eye 108. Light 112 from a broadband light source 114, such as a superluminescent diode with a center wavelength of 840 nm and a bandwidth of 40 nm, is collimated by a collimating element 116, such as a lens or parabolic mirror, linearly polarized by a polarizer 118, and then split into a reference beam 122 and a sample beam 150 by a polarization beam splitter cube (PBS) 120. In a preferred embodiment, the reference arm includes a multi-length delay element in the form of a compound reflector 110, and a quarter-wave plate 124 for polarization transformation, such that light reflected from the compound reflector 110 passes through the PBS 120 and enters the detection arm. The reference arm may also include a relay element and a dispersion matching component.

[0094] In the illustrated embodiment, the composite reflector 110 includes a transparent medium 128 of thickness Δ, which has a first open-aperture reflective surface 130 on its front surface to reflect a first portion 138 of the reference beam 122, and a second reflective surface 132 on its rear surface to reflect a second portion 134 of the reference beam 122 passing through the aperture 136 of the first reflective surface 130. The reflective surfaces 130 and 132 can be, for example, metal or a thin-film multilayer coating. In the illustrated “aperture” location, the composite reflector 110 thus functions as a dual-length delay element, wherein the delay received by the first portion 138 of the reference beam 122 (in this case, the outer portion) is smaller by an amount equal to 2Δ than the delay received by the second portion 134 (in this case, the central portion). n (λ), where n (λ) is the wavelength-dependent refractive index of medium 128. In a preferred embodiment, the medium is selected to have a dispersion that at least partially compensates for the dispersion of eye 108, and may be, for example, water or low-refractive-index glass. In this way, the delay of the first portion 138 and the second portion 134 of the reference beam 122 can be adjusted, and thus its coherence characteristics can be tuned, to match the coherence requirements with respect to various structures or regions (such as lens 140, retina 144, choroid 104, cornea 146, or anterior sclera 106) at different depths in the eye 108 being measured. In a preferred embodiment, the composite reflector 110 is mounted on the mechanical stage 126 such that its position can be adjusted laterally 125 and axially 127. For example, the composite reflector 110 can be adjusted from... Figure 1A The position of the "hole" shown is moved laterally by 125 degrees. Figure 1BThe “planar” position shown (where all portions of reference beam 122 are reflected from front surface reflector 130, thus there is no differential delay on reference beam 122). Axial movement 127 of composite reflector 110 can be used to adjust the path length of the reference arm, i.e., adjust the internal delay in device 100, for example, to match different sample locations in subsequent tomographic images or to obtain information about structures at different depths in the eye. Alternatively or additionally, the entire device 100 can be axially moved relative to eye 108 to adjust the distance from the eye to the device, and thus adjust the path length of the sample arm.

[0095] For eye samples, conveniently, the composite reflector 110 is in the form of a circular, square, or rectangular plate of transparent material 128, with a centrally located circular aperture 136 in the front reflective surface 130. In some embodiments, the front surface of the composite reflector 110 is coated with an anti-reflective coating in the aperture region 136 to minimize front surface reflection of light in the second portion 134 of the reference beam 122. In other embodiments, the aperture region 136 remains uncoated, in which case a small fraction of the light in the second portion 134 (typically 4% of the normal incident light at the air / glass interface) will be reflected from the front surface, thus experiencing the same delay as the light in the first portion 138. This can be useful, for example, for obtaining interference signals from the cornea 146 and retina 144. In still other embodiments, the reflectivity of the aperture region 136 is adjusted to select portions of the reference beam light in the second portion 134 that experience different delays.

[0096] The sample arm includes a spatial sampling element in the form of a two-dimensional (2-D) microlens array 148 to generate a 2-D array of sample sub-beams 152 from the sample bundle 150, which are relayed to the eye 108 via a 4F lens system 154. In some embodiments, the sub-beams 152 have the same focal length, while in other embodiments, the microlens array 148 is designed to adjust the focal length of the sub-beams according to their position in the array, for example, thereby providing appropriate focusing of various sub-beams at different depths of the eye. Advantageously, as Figure 1CAs schematically illustrated, the 2-D array of small beams 152 can be positioned relative to the eye 108, such that some beams 184 enter through the pupil 186 to reach the interior of the eye, while other beams 188 strike one or more anterior surfaces of the eye (preferably including the anterior sclera 106). For the purposes of this specification, we define the “anterior surface” of the eye as any surface in front of the vitreous fluid 105, including but not limited to the posterior lens surface 103 and the anterior lens surface 102, and surfaces in the anterior segment 142 (including the posterior surface of the iris 191, the anterior sclera 106, and the posterior and anterior surfaces of the cornea 146). Light scattered or reflected from various structures of the eye 108 is returned by the relay lens system 154, then refocused by the small lens array 148, and reflected by the PBS 120 into the detection arm after a polarization transformation at the quarter-wave plate 156. It will be observed that the path length of the returned sample light will depend on the distance from where it entered the eye 108 to where it was scattered or reflected. For example, the small beams 188 reflected or scattered from the anterior sclera 106 will have a shorter path length than the small beams 184 that pass through the pupil 186 and are reflected or scattered, for example, from the posterior lens surface 103 or the retina 144. Typically, the number of small beams 152 relayed to the eye 108 depends on the design of the 2-D microlens array 148, and in some embodiments, there may be, for example, 100 or 1000 small beams in a square or rectangular pattern, with a density of, for example, 4 to 100 small beams per square millimeter.

[0097] The reflected sample beam 153 is combined with the reference beam 122 and the combined beam obtained by analysis by polarizer 158 to interfere with the light from the sample and reference paths. The resulting interference pattern is relayed by lens system 160 and optional aperture 162 to remove stray light for spectral analysis in spectrometer 168 at a spatial location grid determined by spatial sampling elements in the form of a 2-D microlens array 164 and a corresponding 2-D aperture array 166. Typically, these two microlens arrays 148, 164 are aligned such that the returning sample beam 153 from microlens array 148 is guided into spectrometer 168. Recalling that the interference between the sample and reference beam in an OCT system depends on the relative delay between the sample and reference paths, it can be seen that the different delays imposed by the compound reflector 110 on different portions of the reference beam 122 at the “aperture” location can compensate for the different delays of the beams reflected or scattered from structures or regions at different depths in eye 108. In one particular embodiment, the composite reflector 110 is designed such that the optical path length difference between the first portion 138 and the second portion 134 of the reference beam 122 is 2·Δ· n(λ) is essentially equal to the difference in optical path length between the sample beams 188, 184 reflected or scattered from the anterior sclera 106 on one hand and from the retina 144 on the other. In other words, the composite reflector 110 can be designed such that the axial spacing Δ between the reflecting surfaces 130, 132 and the refractive index of the medium 128 at the designed wavelength λ are equal. n (λ) provides a predetermined optical path length difference that substantially compensates for the axial depth difference of the eye. This enables the measurement of various axially separated structures or regions of the eye, i.e., structures or regions at significantly different optical depths, within a single frame of the 2-D sensor array 178. We note that a given composite reflector can, for example, be optimized for measuring the eyes of adults or children.

[0098] Spectrometer 168 is a compact reflectance spectrometer capable of simultaneously or at least within a single frame of a 2-D sensor array 178 analyzing multiple grid points, beams, or small beams dispersed by a wavelength dispersive element in the form of a transmission grating 170. In the illustrated embodiment, the spectrometer is used to analyze multiple beams formed by interfering multiple returned sample small beams 153 with a reference beam 122. In this embodiment, interference occurs when polarizer 158 analyzes the polarization states because the returned sample small beams and the reference beam are orthogonally polarized. In other embodiments, a polarization-independent beam combiner can be used to interfere beams in the same polarization state, as is known in the art. After entering spectrometer 168, the interfered beam is redirected by PBS 180 to lens 172, which collimates the beam for dispersion by grating 170, and then passes twice through quarter-wave plate 174 via reflection from mirror 176, thereby rotating the polarization state by 90 degrees. In the combination, quarter-wave plate 174 and mirror 176 form a polarization transformation system that, in this case, applies a 90-degree rotation. After passing through the PBS 180, the dispersive spectral components of the reflected light are imaged by lens 172 onto a 2-D sensor array 178, such as a CMOS camera. The interference image detected by the 2-D sensor array is read out in a single frame for subsequent analysis by a computer 182 equipped with suitable computer-readable program code. The computer can, for example, apply known Fourier transform techniques to obtain a depth-resolved image, i.e., a three-dimensional (3-D) image of the eye 108. In a preferred embodiment, the grating 170 is oriented relative to a spatial grid defined by the 2-D microlens array 164 and the corresponding 2-D aperture array 166, such that each combined beam entering the spectrometer 168 is dispersed into individual pixel groups of the 2-D sensor array 178, as described in U.S. Patent Application Publication No. US 2016 / 0345820 A1 entitled “High resolution 3-D spectral domain optical imaging apparatus and method,” the contents of which are incorporated herein by reference.

[0099] In a preferred embodiment, the spectrometer 168 is configured such that each combined beam is dispersed onto a plurality of parallel pixel groups of the 2-D sensor array 178. For example, Figure 7AThe projections 702 of three combined beams dispersed onto a portion 704 of a 2-D sensor array are shown schematically. Each projection extends across several pixel rows 706 in a direction perpendicular to the dispersion axis 708 and will generally have an approximately Gaussian intensity curve 710 in that direction. In a direction parallel to the dispersion axis 708, the projections 702 of the combined beams of dispersion will have intensity curves indicating variations in interference fringes within that beam. Importantly, the intensity curves of the interference fringes will be reproduced across several pixel rows 706, such that reading out any or all of the relevant pixel rows will produce substantially the same information without saturation. However, the finite dynamic range of individual pixels, determined by the number of photoelectrons that can be stored in each pixel within a single frame, can lead to some pixel saturation. This can occur, for example, if some small beams contain relatively strong specular reflections (e.g., from the cornea). To demonstrate this effect, Figure 7B for Figure 7A The representative beam projection 702 shows graphs 712 and 714, respectively, for the intensity contrast of the number of pixels for the center pixel row 716 and the outer pixel row 718. It can be seen that the interference fringe 712 at the center pixel row 716 is clipped at its maximum value (normalized to 1 here), while the interference fringe 714 at the outer pixel row 718 remains unsaturated. The effect of clipping can also be seen in graph 720, which shows the sum of the detected intensities from the center and outer pixel rows. Sudden changes in the detected intensities (such as the transition 722 to a constant intensity value in graph 712 or the abrupt slope change 724 in graph 720) will result in many higher-order frequency components in the spectral domain, which can manifest as artifacts or streaks in the A-scan corresponding to this small beam. This can be avoided by using unclipped data from the outer pixel row. For example, the analysis can be restricted to using only uncapped pixel data, or the pixel data can be processed in such a way that the regions of capped data 726 are optionally replaced with the corresponding uncapped data 728 by some scaling determined from the unsaturated regions, thereby producing a corrected intensity profile 730. These modified analyses typically sacrifice signal-to-noise ratio to a very small extent, but the reduction in artifacts allows for a better estimation of surface boundaries in specular reflection regions.

[0100] This artifact reduction technique can also be applied when the dispersion axis 708 is at an angle relative to the pixels in the 2-D sensor array, provided that the beam projection 702 extends across multiple pixels in a direction perpendicular to the dispersion axis 708. For each beam projection, there are still at least two groups of pixels extending parallel to the dispersion axis, which receive the same interference fringe information but have different intensities.

[0101] It should be noted that this artifact reduction technique cannot be applied to OCT devices that obtain spatially resolved image data from illumination lines or areas (e.g., as in U.S. Patent No. 8,534,838) because in these cases, the intensity curve from a given sample area will not be reproduced across several pixel rows or groups, isolated from the intensity curves corresponding to other sample areas. This represents the effect of using one or more discrete beams (e.g., from...) Figure 1A The small lens array 164 shown in the figure has the advantage of presenting interferometric data to a 2-D sensor array in the form of interferometric data.

[0102] Figure 1A Several variations of the apparatus 100 shown are possible. For example, the splitting and recombination of the sample beam 150 and the reference beam 122 can be achieved using an optical fiber coupler or a non-polarizing beam splitter. The apparatus can also be used to split the source light 112 into the sample beam 150 and the reference beam 122 using a PBS 120 and to recombine the beams after they have passed through the sample using a separate beam combiner, suitable for a transmissive sample rather than a reflective sample (such as an eye 108). A composite reflector 110 with three or more axially spaced reflective surfaces designed for, for example, precise path length matching of light scattered or reflected from the anterior sclera 106, the anterior lens surface 102, and the retina 144 can also be used. In another variation, the 2-D array of sample beams 152 can be generated by spatial sampling elements in the form of aperture masks, MEMS mirror arrays, or diffractive optical elements instead of the microlens array 148. Similarly, the microlens array 164 preceding the spectrometer 168 can be replaced by aperture masks, MEMS mirror arrays, or diffractive optical elements. In another variant, a 1-D array of small sample bundles can be generated using spatial sampling elements in the form of a 1-D small lens array or similar, but generally, 2-D arrays are preferred for obtaining data across a larger sample area in a single frame.

[0103] We note that the device does not necessarily need to generate an array of sample bundles 152 for illuminating the eye 108. That is, different parts of the eye can alternatively be illuminating with unstructured sample bundles 150. However, using bundles to illuminate multiple discrete points in or on the eye and obtaining data from them is not only advantageous as reference... Figure 7A and Figure 7B The aforementioned method alleviates pixel saturation and also facilitates achieving a suitable signal-to-noise ratio for the weakly scattering structure of the eye, because the sample light is directed to a higher intensity discrete region, and the returned light can be captured from a larger numerical aperture, thus providing a stronger signal. As previously mentioned, it is also beneficial to be able to adjust the microlens array 148 or other spatial sampling elements to focus different beams 152 at different depths within the eye.

[0104] Figure 2A Depicting the use Figure 1A The flowchart illustrates a method for constructing a synthetic image or synthetic tomographic image of the eye using the apparatus 100 shown. In step 202, the composite reflector 110 is moved to a "planar" position, as... Figure 1B As shown, and in step 204, the anterior region of the eye 108 is measured to provide a first image or tomographic image (Image A). Reference Figure 1A and Figure 1C The 2D array of small beams 152 shown in the image A is positioned on the eye. For this image A, at least some of the outer small beams 188 measure a first region of the anterior surface of the eye, preferably including a portion of the anterior sclera 106, while at least some of the more central small beams 184 measure a third region of the eye, for example including the cornea 146 or the anterior lens surface 102. In step 206, the composite reflector 110 is moved to the "aperture" position, as... Figure 1A As shown in the diagram. In step 208, a second image or tomographic image (Image B) is obtained by measuring a second region of the anterior surface of the eye, preferably including a portion of the anterior sclera 106, using at least some outer small bundles 188, and measuring a fourth, deeper region of the eye (such as the retina 144) using at least some more central small bundles 184. The corresponding anterior surface regions in Images A and B should at least partially overlap. Figure 2C As shown, this means that the first front surface region 201-A measured by certain small beams 188-A in image A should at least partially overlap with the second front surface region 201-B measured by certain small beams 188-B in image B. When images A and B are acquired, there may be some overlap between the discrete points illuminated by the individual small beams, but this is certainly not necessary. In step 210, the differential delay 2·Δ· applied to the reference beam 122 by the composite reflector 110 is... n (λ), adjusting a portion of image B obtained from the fourth, deeper region of the eye relative to the portion obtained from the second anterior region. Then, in step 212, a synthetic image or synthetic tomographic image (image C) is created by allowing relative translation or rotation between the "A" and "B" images to minimize the fitting error of the overlapping anterior portions of the two images (e.g., using local regression or nonparametric fitting), thereby recording data from the third and fourth regions of the eye. In step 214, it is determined whether further image depth is needed. If so, in step 216, another composite reflector with a larger or smaller differential delay is placed in the reference arm, and the process returns to step 208 to obtain and compute additional "B" and "C" images. Alternatively, multiple "B" images can be obtained with different composite reflectors before computing the composite "C" image. Figure 2AMost (if not all) steps in the flowchart will typically be performed by computer 182 equipped with appropriate computer-readable program code, although some steps, such as moving the composite reflector 110, can be performed manually.

[0105] Figure 2B Depicting the use of Figure 1A A flowchart of another method for constructing a synthetic image or synthetic tomographic image of the eye using device 100, wherein the composite reflector 110 is positioned as follows: Figure 1B The indicated "planar" position indicates that there is no differential delay across reference beam 122. In step 218, a first optical coherence tomography image or image of the eye 108 is acquired. Reference Figure 1A as well as Figure 1C The 2-D array of small beams 152 shown is positioned on the eye. This first tomographic image or image may contain data from a first region of the anterior sclera 106 measured by at least some of the outer small beams 188, and data from a third region of the eye (including, for example, the first region of the anterior lens surface 102) measured by at least some of the more central small beams 184. In step 220, the device 100 or eye 108 is adjusted, for example by moving a fixed target or by rotating the device around the eye, such that the small beams 152 strike different parts of the eye, and in step 221, the distance from the eye to the device is optionally adjusted to control the sample path length. In step 222, a second optical coherence tomographic image or image is acquired. This second tomographic image or image may contain data from the anterior sclera 106 at least partially consistent with the data referenced above. Figure 2C The data includes the data from the first region overlapping the second region, and the data from the fourth region of the eye, including, for example, the second region of the anterior lens surface 102. Finally, in step 224, the first and second tomographic images are processed to record the overlapping portion of the first and second regions of the anterior sclera 106, thereby recording data from the third and fourth regions of the eye. Recording the overlapping portion of the first and second regions of the anterior sclera 106 may, for example, include local regression or nonparametric fitting to compensate for the relative translation or rotation between the first and second tomographic images. If data from other regions of the eye (e.g., other regions of the anterior lens surface 102) is required, steps 220 through 224 can be repeated. Alternatively, several tomographic images or images of the individual eye regions can be obtained before recording data from the overlapping portion of the anterior sclera. Similarly, Figure 2B Most (if not all) of the steps in the flowchart will typically be performed by a computer 182 equipped with appropriate computer-readable program code.

[0106] Figure 2BThe method depicted in the flowchart can also be applied to retinal measurements, where the compound reflector 110 is in an "aperture" position, such that the first portion 138 of the reference beam 122 has a shorter path length than the second portion 134. Reference Figure 1A as well as Figure 1C The 2-D array of small beams 152 shown is positioned on the eye, in which at least some of the more central small beams 184 measure different regions of the retina 144 in the first and second tomographic images, which can be recorded by recording the overlapping portion of the anterior sclera measured by at least some of the outer small beams 188. If the depth of field of the device 100 is generally insufficient, the differential delay applied to the reference beam 122 by the compound reflector 110 can also be beneficial for obtaining data from other relatively deep parts of the eye (such as the posterior lens surface 103) or even from the anterior lens surface 102.

[0107] exist Figure 2A or Figure 2B Each image or tomographic image acquired in the method described herein should be acquired within a sufficiently short time period so that the effect of eye movement is negligible, for example, within 2 milliseconds, more preferably within 1 millisecond. Even more preferably, each image or tomographic image is acquired within 100 microseconds to reduce streaking caused by eye movement. Eye movement occurring between the acquisition of tomographic images is irrelevant, as this can be compensated for by recording the overlapping front of the corresponding images or tomographic images. When compensating for the effect of eye movement, the optical effects of the eye on the small beams propagating within the eye can be directly calculated, which will be apparent to those skilled in the art.

[0108] For recording various images or tomographic images acquired from eye 108 (e.g., "A" image and one or more "B" images), using information from the anterior sclera 106 (preferably including the limbus 192, i.e., the interface between the cornea 146 and the sclera) instead of, for example, information from the cornea itself has many advantages. For example, the anterior sclera scatters more strongly than the cornea, providing a larger signal. Furthermore, the shape of the anterior sclera generally provides stronger identifiable geometry than the cornea, particularly at the limbus 192, which improves rotational recording of images or tomographic images. It will be understood that because the cornea 146 has only a slight change in curvature and is substantially rotationally symmetric, it would be more difficult to rotationally align images or tomographic images using only a small bundle of data from the cornea. For the purposes of this specification, the limbus 192 is considered to be part of the anterior sclera 106.

[0109] We will now use a broadband source 114 with (840 ± 30) nm and a 2-D CMOS camera 178. Figure 1AThe apparatus is described in some embodiments for constructing synthetic images or synthetic tomographic images of the eye. Since the depth of field of the apparatus is sufficient for the area of ​​interest in these embodiments (from the vertex of the cornea 146 to the posterior lens surface 103), differential delay across the reference beam 122 is not required.

[0110] Figure 8 A representative coarse-sampled “B-scan” of the anterior segment of the eye is shown, in which portions of the cornea 146, iris 191, and anterior sclera 106 can be identified. This B-scan image consists of a row of 56 A-scans at a 0.3 mm spacing, extracted from a coarse-sampled grid of 18 × 56 small bundles captured in a single frame from a CMOS camera. In this embodiment, the recorded volume will consist of a total of 144 frames sampled at a rate of 44 F / s. The small bundle grid is patterned with a 25 μm step size, such that after 144 frames, each small bundle covers an area of ​​0.3 mm × 0.3 mm, and the total area covered by all small bundles is 5.4 mm × 16.8 mm.

[0111] Recording 144 frames was achieved by finding appropriate translations and rotations for each frame. For accurate frame recording, we prefer to use a reference surface that provides a relatively strong signal and has a distinct slope and range. This takes into account the difference in signal-to-noise ratio (SNR) between individual frames, such as... Figure 8 It is evident that the anterior scleral regions 106 along the x-axis from approximately 0 to 2.5 mm and from 14 mm to 16.5 mm have relatively high SNR and slope suitable for recording purposes. The final surface measurements were obtained from the recorded volumetric images.

[0112] It should be noted that the "surface" used for recording purposes may not necessarily correspond to the actual interface of the eye or the actual interface within the eye, depending on the interaction between the sample light and the interface in question. By way of example, Figure 9A A typical A-scan curve 902 of the cornea at a distance of 0.6 mm from the vertex is shown, obtained by alignment and averaging the A-scan across multiple frames. Figure 9B The corresponding A-scan curve 904 obtained from the anterior sclera is shown. From these curves, both obtained using light at (840 ± 30) nm, it is evident that while a conventional edge filter can be applied to detect either of the clearly defined transitions 906, 908 corresponding to the anterior and posterior corneal surfaces, it is less suitable for detecting the less clearly defined edge 910 of the scleral A-scan curve 904. It will be understood that the term "surface" should be interpreted as the depth region close to the physical interface. Figure 9BThe specific embodiment of the scleral A-scan curve 904 shown has a depth region of approximately ±0.2 mm around the physical interface (but can be larger, for example, up to ±1 mm). Instead of using an edge filter to determine the scleral surface, a filter that more closely matches the shape of a typical scleral A-scan curve is preferably used, such as one obtained by averaging multiple scleral A-scans. Figure 9C The filter template 912 shown is applied to a small beam of A-scan corresponding to the scleral region. Figure 10 The grid positions 1002 of the cornea 146 in the image are schematically shown on both sides. The surface height of each A-scan is determined by the peak value of the filtered signal. We note that, in this case, the scleral surface used for recording is not merely an offset of the air / tear film interface, but depends on the volume distribution of the surface.

[0113] An approximate initial reference surface can be obtained from a single frame, and the relationship between surface height variation and translation and rotation vectors can be linearized using a small scan range. The solutions Δx, Δy, Δz, and Δθ can then be found using an efficient least-squares method. x , Δθ y and Δθ z The inputs are the gradient of the reference surface and the surface height for each frame, which are evaluated for all scleral A scans. For higher accuracy, the relatively low computational cost of this linearization method allows for a second iteration, where the output from the first iteration is used as the reference recording surface for the second iteration. Additionally, the results from the first-level recording can be used to provide an axial window to minimize the chance of outliers selected for the second-level surface detection. Record computation typically produces a “volume-averaged” dataset, where sparse volume data corresponding to the measurement parameters are binned into voxels or distributed across multiple voxels, and the resulting voxels are given as the average or weighted average assigned to each bin.

[0114] For the purposes of this embodiment, we use data from the anterior sclera to limit the recording to translation only. The resulting translation vector is as follows: Figure 11 As shown, the periodic pattern with amplitudes of -0.3 mm on the x and y axes reflects the combination of the scan pattern and eye movement during scanning. Generally, we find a maximum body movement of 1 mm / s, and in the illustrated embodiment, the axial movement, as shown in the Δz curve, is on the order of 0.1 mm within approximately 3 seconds required to capture 144 frames at 44 F / s.

[0115] Figure 12 This image shows a B-scan of a sample eye extracted from a volume-averaged dataset obtained from 144 recorded frames. The image reveals several eye structures with excellent clarity compared to the individual frames (where...). Figure 8 (The corneal surface is representative), including the air-tear film interface 1202, the posterior iris surface 1204, and the anterior lens surface 102. By using an appropriate filter for identification, the air-tear film interface 1202 can be identified, and corneal curvature data consistent with conventional techniques can be obtained.

[0116] In the second embodiment, Figure 13A A coarsely sampled B-scan of the lens extracted from a single frame of 18 × 56 A-scans with a 0.3 mm pitch is shown, similar to... Figure 8 As in the previous embodiment, the anterior scleral region 106 is used to record a total of 144 frames. Figure 13B The image presents a B-scan extracted from a volume-averaged recording frame, clearly showing the anterior lens surface 102 and the posterior lens surface 103. An anterior scleral reference provided the recording information when calculating this image. Figure 14 This is a volume-averaged B-scan, showing the cornea 146 and lens 140 obtained by additionally recording a second volume-averaging measurement of the corneal region, which was acquired by varying the instrument position relative to the eye to focus at different depths. In this case, the recording of the volume-averaged corneal and lens images is based on a common anterior scleral region from both datasets. We note that, alternatively, the corneal and lens junction recording can be achieved by recording separate corneal and lens frames relative to a common scleral reference surface prior to volume averaging. Importantly, regardless of significant patient movement between acquisitions, the joint recording of the scleral region allows for the acquisition of synthetic images with a large depth range while maintaining measurement accuracy. We note that in Figure 12 , Figure 13B and Figure 14 The volume-averaged B-scan shown is the original image, i.e., before calibration and refractive correction using techniques known in the art.

[0117] exist Figure 1A In the OCT device 100 shown, information from all parts of the eye 108, acquired by an array of small beams 152, is simultaneously collected by a 2-D sensor array 178. However, due to the approximate Gaussian or Lambertian intensity distribution of many light sources, this can result in the outer small beams having a lower intensity than the more central small beams. Figure 3 An alternative lighting system 300 is shown in a schematic oblique view, which is used to provide lighting in a way that is more efficient than traditional lighting systems. Figure 1AThe superluminescent diode (SLD) 114 and lens 116 shown produce more uniform illumination over the extended region. Light 112 from the SLD 114 is focused by the parabolic mirror 302 and lens 116 onto a MEMS mirror 304, which is capable of scanning during a single acquisition frame of a 2-D sensor array used to acquire OCT or tomographic images. Before collimation at the second lens 310, the beam 306 generated by the SLD 114, parabolic mirror 302, and lens 116 (typically highly elliptical) can be manipulated 312 into an effective beam with a desired shape 308 by high-speed angular jitter 314 in one dimension (x-axis or y-axis) or two dimensions (x-axis and y-axis) by the MEMS mirror 304. The operation of the OCT device is as previously referenced. Figure 1A The process involves spatially sampling the sample light using a 2-D microlens array 148 or similar, the difference being that small beams containing information from different lateral portions of the eye 108 are sequentially struck onto the 2-D sensor array 178. Assuming that the scanning 314 of the MEMS mirror 304 is faster than eye movement, the visibility of the interference pattern fringes or the stability of the snapshot single-frame image acquired by the 2-D sensor array 178 will not be affected by eye movement. That is, individual images or tomographic images can still be acquired in a sufficiently short time so that the effect of eye movement is negligible.

[0118] While from a metrological perspective, a "snapshot" technique equivalent to a global shutter is preferable for simultaneously capturing the entire image or tomographic image, it is not essential. The use of the scanning mirror 304 is similar to a rolling shutter in a camera and maintains certain standards that can improve the signal-to-noise ratio of the image or tomographic image, as well as the uniformity of the signal-to-noise ratio across the field of view. To achieve this improvement while remaining within certain predetermined limits, we can define time... t that time t This represents the time limit for ensuring the phase stability of the interferometric image. Typically, it is approximately 100 microseconds. t Suitable for patients fixating on a target (corresponding to axial motion less than a quarter wavelength (typically about 0.2 μm), and is in the MEMS mirror 304 in an associated microlens array ( Figure 3 (Not shown in the image) Exposure time limitation for any single small beam when scanning light source 112. Second time period. T This can be defined as the frame exposure time, which for eye measurements is typically about one millisecond without significantly degrading the quality of the measurement. Then, it is preferable to make the width of the scan beam 306... x With frame width X Matching makes x / X Approximately equal to t / TThis enhances the signal-to-noise ratio without reducing measurement accuracy beyond a predetermined level. If desired, pairs of deformable prisms or cylindrical lenses may be included in the illumination system 300 for independently controlling the width of the beam 306 generated by the SLD 114, parabolic mirror 302, and lens 116. x and height y .

[0119] Back Figure 1A It will be understood that when the cornea 146 of a normally unaccommodated eye 108 is illuminated by an array of parallel beams 152 as shown, light from all the beams entering the pupil 186 will be received at a single zone 190 of the retina 144, the diameter of which corresponds to twice the numerical aperture of the beams multiplied by the focal length of the eye. These beams interfere with each other, thus producing structured illumination of the retina, but it is difficult to extract a large amount of lateral resolution information. Therefore, the retinal portion of the obtained image is largely just an average of the structures in zone 190. This measurement can be repeated for different incident angles, by having the patient track a movable fixed target, or by rotating the device 100 relative to the eye 108 to allow for precise measurement of the axial length of the eye across the retina. Figure 6 The flowchart shown depicts the entire process of providing information about the overall shape of the eye. In step 602, the composite reflector 110 is moved to the "aperture" position, and in step 604, two or more images or tomographic images of the eye 108 are measured at different incident angles, for example, by moving a fixed target or relative to the eye rotation device 100. Reference Figure 1A and Figure 1C Each image or tomographic image contains data from the anterior surface of the eye (preferably including the anterior sclera 106) provided by at least some outer bundles 188, and data from a local area 190 of the retina 144 provided by at least some more central bundles 184. The corresponding anterior surface data should at least partially overlap, as referenced above. Figure 2C As explained. In step 606, based on the differential delay 2·Δ· applied to the reference beam 122 by the composite reflector 110. n (λ), adjusting the retinal portion of each image or tomographic image relative to the anterior surface portion. Finally, in step 608, the overlapping portions of the corresponding anterior scleral data are used to record the retinal portions of two or more images or tomographic images. Figure 6 Most (if not all) of the steps in the flowchart will typically be performed by a computer 182 equipped with appropriate computer-readable program code. Figure 6 The process shown can provide useful measurements in different locations; for example, while it may be time-consuming in a clinical setting, it can provide information about the overall shape of the eye.

[0120] However, it will be shown that the discrete point grid can be modified by inserting an additional lens in front of the eye, or by appropriately modifying the relay optics in the sample arm. Figure 1A The imaging optics system shown delivers an angularly dispersed array of small beams focused onto the retina, a discrete grid of points that can be measured simultaneously or at least within a single frame of the sensor array. This can be used to image extended areas of the retina by jittering the position of the small beam array, for example, by using MEMS mirrors in relay optics within the sample arm. To further establish accurate measurements of eye shape, as is crucial for applications such as the diagnosis and monitoring of myopia development, it is necessary to go beyond imaging and precisely determine the axial length at different locations on the retina using illumination beams at different angles. For this purpose, the measurement requires a reference measuring instrument positioned relative to the eye, as further described below. It also requires knowledge of the shape of the cornea and the subsequent layers of the eye, which can be obtained using the reference mentioned above. Figure 1A The described apparatus and techniques are used for measurement.

[0121] therefore, Figure 4 It is shown in schematic form. Figure 1A A variation of the sample arm relay optics of the device shown is provided to offer a spectral domain OCT device according to a second embodiment of the invention. For example... Figure 1A As shown, from PBS 120 and quarter-wave plate 156 ( Figure 4 The emitted sample beam 150 (not shown) is transmitted through a spatial sampling element in the form of a 2-D microlens array 148 to form an array of parallel small beams 152. In some embodiments, the small beams form a uniform array, while in others, they may have different waist dimensions depending on their position within the array, determined by the characteristics (particularly the focal length) of the microlenses in the microlens array 148. The small beam array 152 then encounters... Figure 1A The relay system 400 is significantly different from the 4F lens system 154. In this second embodiment, the relay system 400 includes a relay system 400 with a focal length of [missing information]. FThe device includes a conventional lens 402, a MEMS mirror 404 for jittering the angularly dispersive sub-beam group 412 at its on-eye position, and a compound lens 406 having two portions 408 and 414 with different focal lengths for acting on different sub-groups of sub-beams 410 and 416. For simplicity, the MEMS mirror 404 is shown as transmissive rather than reflective. In some embodiments, the compound lens 406 is a monolithic structure having the different portions 408 and 414 as shown, for example manufactured by replica diamond turning. Alternatively, it may include two or more lenses positioned adjacent to each other to provide a multi-element lens designed to reduce aberrations in both the central sub-beam 416 and the peripheral sub-beam 410. In a preferred embodiment, the device includes a mechanism for interchangeable compound lenses 406, such as a lens mounting bracket or lens wheel. The interchangeable compound lenses may, for example, have different focal length pairs, different relative sizes of the different portions 408 and 414, or more than two different portions. In yet another variation, the compound lens can be replaced by a conventional lens, preferably matched with lens 402, to provide, for example... Figure 1A The device shown is a 4F relay system 154. This provides a low-cost means for providing additional instruments capable of operating in this configuration, optimized for measuring anterior eye structures.

[0122] The outer portion 408 of the compound lens 406 relays the peripheral subgroup 410 of the angularly dispersed small beam group 412 to the anterior segment 142 of the eye 108, preferably including a portion of the anterior sclera 106. In this particular embodiment, the outer portion 408 of the compound lens has a focal length equal to that of the first lens 402. F This provides a non-magnified telecentric relay system with parallel propagating peripheral beams 410. Alternative implementations with non-single magnification or non-telecentric imaging (e.g., by including an optical wedge) can provide a set of divergent or converging peripheral beams. In either case, the relayed peripheral beams enable information to be acquired from a point grid in or on the anterior segment 142 (preferably including a portion of the anterior sclera 106).

[0123] The focal length of the internal portion 414 of the compound lens 406 (in this embodiment, it is...) F / 2) The central subgroup 416 of the angularly dispersed small beam 412 is selected to re-image onto the retina 144. This is achieved by the focal length range of the internal portion 414 of the compound lens, where... F The / 2 selection provides an inverted image 418 from the central small beam 416 of the MEMS shake mirror 404, which is located at a distance from the compound lens 406. FThe inverted image 418 can be located inside or outside the anterior segment 142, provided that a substantial proportion of the central small beam 416 is transmitted through the pupil 186 and relayed to the retina 144. The optical power of the eye 108 transforms the relatively large area of ​​the angularly dispersed small beam 416 into a more focused spatial dispersion array 422 of small beams on the retina. The MEMS mirror 404 simultaneously jitters the positions of the central small beam array 422 on the retina 144 and the peripheral small beam 410 in front of the eye 108, wherein the peripheral small beam provides a reference for recording retinal imaging measurements of the central small beam, as previously explained.

[0124] What will be understood is that, Figure 4 The OCT device modified in the manner shown is advantageous for lateral-resolved imaging of the extended area of ​​the retina 144. Furthermore, it can provide ocular measurements useful for tracking myopia progression in patients and monitoring the effects of treatments on progression. Advantageously, the modified sample arm relay optics 400 enable approximately simultaneous recording of the entire 2-D array of small beams 152. A subgroup of small beams 410 (e.g., which may be parallel or converging) strikes the anterior segment 142 of the eye (preferably including the anterior sclera 106) to provide recording of data obtained using a second angularly dispersive subgroup of small beams 416 mapped across a region 422 of the retina 144 using the pupil 186 and the eye's optical power. Importantly, this configuration can also provide small-diameter beams incident on the corneal or scleral region on one hand, and small-diameter beams incident on the retina on the other. For example, the relay optics can be designed such that the diameter of the beams is less than 50 μm for both the scleral and retinal regions. Smaller beams on the retina will provide higher resolution imaging of the retina, but with reduced depth of focus. Typically, a compromise between these two factors is achieved by using a small beam diameter of 5 μm to 20 μm at the retina.

[0125] Figure 5A It is shown in schematic form. Figure 1A A variation of the sample arm optics of the apparatus 100 shown is used to provide a spectral-domain OCT apparatus according to a third embodiment of the invention. This variation can also be applied to… Figure 4The sample arm optics shown incorporate an improved aperture at the front end of the sample arm to provide better isolation for the returning sample bundles. As will be explained, this improved aperture suppresses crosstalk between the returning sample bundles, particularly by suppressing the passage of off-axis high-intensity specular reflections. The wavefront 500 in the sample arm points to a spatial sampling element in the form of a 2-D microlens array 148, which forms multiple bundles, with a waist 502 passing through a structured aperture septum 504, the aperture size of which is comparable to the bundle waist or the first Rayleigh ring. The bundles are then relayed by a second 2D microlens array 506 to provide an effective bundle waist 508 that can be located in front of or behind the second microlens array 506 by selecting the spacing between the microlens arrays 148 and 506 and the focal length of the second microlens array. In some cases, the focal length of the individual microlenses in the second microlens array 506 can be adjusted such that the effective bundle waist varies significantly, for example, to suit the portion of the eye sampled by the individual bundles. A 4F relay system 154 is configured to relay the effective beam waist toward the sample eye 108. This 4F relay system can be designed such that the size of the sampling points 510 on the eye illuminated by the small beam is significantly smaller than the intervals between them. When the small beam is relayed to the sampling point 510 on the cornea 146, it typically generates a specular reflection signal 514 in addition to the backpropagating scattered signal 512. This specular reflection signal is typically off-axis, i.e., not backpropagating. This specular reflection 514 will typically be much stronger than the scattered signal 512 and, if measures are not taken to avoid crosstalk from the returning small beam 518 as it travels to the detection system, has the potential to overwhelm this signal as well as the signal 516 scattered from adjacent sampling points 510. The specular reflection light 514 is transmitted by the 4F relay system 154 to a position 520 near the corresponding effective beam waist 508 and, due to its angular path, can be directed to adjacent small lenses to interfere with its weak scattered signal 518. This crosstalk can introduce errors when identifying interfaces or other ocular surfaces.

[0126] like Figure 5BAs shown in the enlarged view, the structured aperture septum 504 includes a first member 522 having a plurality of apertures 524 for allowing the on-axis beams 512, 516, 518 returning from the eye to pass through. This member 522 will block most of the off-axis specular reflections 520 because refraction at the second microlens array 506 will tend to direct them away from the apertures 524. However, the specular beams 520 can still be caught at the edges of the apertures 524, causing some diffraction of the specular light over an angle range 526, which may be collected by adjacent microlenses 528 in the first microlens array 148. To prevent this, the structured aperture septum 504 preferably includes a second member 530 extending substantially parallel to the propagation direction of the on-axis beams 512, 516, 518 to suppress the passage of off-axis light (such as specular reflections 514, 520). The second member 530, which preferably extends toward the first small lens array 148, provides additional crosstalk suppression, thereby allowing for more accurate detection and interpretation of weak backscattered signals 512, 516, 518.

[0127] The structured perforated partition 504 can be made, for example, by laser drilling holes 524 in a thin plate to provide the first component 522, wherein the second component 530 is provided by attaching the plate to a honeycomb lattice or the like, the lattice size being compatible with the spacing of the microlenses in the first microlens array 148.

[0128] Various methods have been described above for creating volumetric or tomographic images of the eye by recording multiple 3-D OCT or tomographic images together to create a synthetic image based on, for example, data from the scleral surface. Another metrological problem we hope to address is the ability to provide a 3-D model of the eye shape that includes the retina, where the curvature and shape of the retina can be relied upon, not just the continuity of the images, as is the case in most OCT measurements. As previously mentioned, an additional difficulty in measuring eye shape using OCT is that the apparent curvature of the retina is affected by the position of the OCT instrument relative to the eye. To address this, we further rely on information about the relative position of the eye to the instrument measured in a single OCT measurement, and knowledge of each optical surface of the eye determined by the OCT, to allow for accurate reconstruction of the shape of the posterior surface of the eye. The reconstruction can be based on any of the following:

[0129] (i) Perform ray tracing or other beam propagation simulations using parameters determined from front-end measurements or calibrations, wherein the ray tracing or other optical model provides calibration between the converging small beams of the front-end measurements and retinal measurements, along with the relative delays of the calibration sample and the reference beam; or

[0130] (ii) Using a finite set of parameters (e.g., x, y, z, and θ) to define the position of the instrument relative to the eye to create a calculated curvature modification of the retinal image, which is obtained by formulating a formula that takes into account the relative optical trajectory of a small beam passing through the eye.

[0131] In both cases, it is preferable, but not necessary, that the instrument's position information relative to the eye is acquired simultaneously with the retinal image.

[0132] We also found, for example, in Figure 12 The clearly visible posterior iris surface 1204 provides a relatively smooth and well-defined surface, which in some cases can be a suitable reference surface for recording multiple OCT frames or images. However, in this case, when the inner surface is used as a reference instead of an outer surface such as the anterior sclera, the absolute position of the eye needs to be calculated by taking into account the optical refraction that occurs before that inner surface in a consistent manner.

[0133] In some implementations, a complete optical model of the anterior part of the eye (e.g., anterior and posterior corneal topographic maps) will be generated previously using instruments in different acquisition modes, and may use different delays and / or instrument positions.

[0134] Figure 15 A simplified simulation embodiment of case (ii) above is schematically illustrated, namely, a simplified simulation embodiment that uses classical geometric optics to determine the apparent or actual shape of the retina based on the instrument position (expressed as the angle from the corneal apex). Solid lines 1502A and 1502B show the measured distance (in mm) to the retina relative to a specific interface determined from scan A for two different axial instrument positions. These lines represent the apparent retinal shape for different axial instrument positions. Two lines 1504A and 1504B correspond to the apparent shape of a perfectly spherical retinal surface of radius R, which is determined by the measurement characteristics of the anterior segment of the eye. Dashed lines 1506A and 1506B now show the calculated shape of the retina relative to a sphere of radius R. The position of the fovea is schematically shown by the concavity 1508 of the retinal shape. It can be seen that the calculated shape of the retina relative to a sphere of radius R is independent of the axial position of the instrument relative to the eye, demonstrating the correction for the apparent retinal shape. Although for simplicity, the embodiments shown here only show variations in the axial position of the instrument (approximately 8 mm in this case), the angular orientation and lateral position of the instrument relative to the eye can be considered in a similar manner to ensure repeatable and accurate measurements of the retinal shape.

[0135] As an example of the above situation (i), Figure 16The diagram illustrates a correction term 1602 for the axial depth at a specific angular position on the eye, calculated using a ray tracing algorithm. In this figure, the x-axis represents the eye position, i.e., the relative distance (in mm) from the designed corneal plane, while the y-axis represents the maximum difference (in mm) in the optical path length between the on-axis and off-axis beams. The correction is determined based on measurement parameters of the anterior segment of the eye and the relative position of the eye to the instrument, where the lens configuration is adapted to measure the retina at the appropriate location.

[0136] Figure 17 A flowchart illustrating an improved measurement for determining eye shape according to a preferred embodiment is provided, wherein the influence of the instrument's position relative to the eye is corrected. In step 1702, an OCT device with a first optical repeater (e.g., Figure 1A The 4F lens system 154 shown in the sample arm is used to measure the anterior segment of the sample eye and the axial depth to the fovea in the first acquisition. Preferably, the axial depth is measured to the retinal pigment epithelium (RPE) at the fovea. Then, in step 1704, the refractive characteristics of the anterior segment of the eye are calculated based on the data obtained in the first acquisition. In step 1706, a second optical repeater (such as...) is used... Figure 4 The relay system 400 shown captures an image of the eye's retina on a dotted grid in the second acquisition, the second optical repeater being calibrated relative to the first optical repeater. This makes it possible to determine the relative axial and angular positions of the first and second acquisitions in step 1708. Finally, in step 1710, for example based on... Figure 15 The correction formula discussed or by using about Figure 16 The discussed ray tracing or other optical models determine the corrected retinal shape. We note that the axial eye depth measured in step 1702 does not necessarily have to be the depth to the fovea, but it is convenient to use a fixed target to align with the fovea. The fovea can also be identified from the retinal image captured in step 1706.

[0137] While we have described in the preceding discussion the use of metrology and tomography to record retinal or other internal ocular data from the anterior surfaces of the eye (such as the anterior sclera or posterior iris), systems with simplified hardware may only be able to obtain retinal data. For example, it may not be possible to obtain data from sources such as... Figure 4 The peripheral small bundle 410 shown provides the recording points. In this case, we can rely on the morphology of the eye to provide additional markers for identifying the axial position. If we only rely on the angular range of the small bundle (e.g., from such...) Figure 4The axial length is obtained starting at position 422 on the retina (shown in the central retinal bundle 416), but the complete anterior and foveal lengths have already been obtained, which in many cases is sufficient to identify the problem and correct the axial length for the instrument position. The distance between the instrument and the eye will be known, but without angular content, it may not be possible to correct directly. However, by identifying the fovea, correction can be made through the morphology of the eye without further recording. This solution is easily adaptable to changes, although there are situations where this can be well controlled, such as pupil dilation or a fixed target. In this case, by using the retinal bundle 416 to generate a wide, dense grid of scan points 422 on the retina 144, recording of each grid point can be achieved based solely on the shape of the eye. For example, for an eye with a given foveal depth, we can predict the apparent shape of the assumed spherical retinal surface. The deviation from the predicted shape represents the actual shape variation of the eye, which is a function smooth enough to have sufficient features to allow alignment of each snapshot grid. This is an attractive alternative for anterior and retinal measurements using a 4F repeater 154 with a single-focal-length lens in the sample arm optics and potentially without the need for low-cost instruments with multi-length delay elements such as the compound reflector 110. The location of the fovea can be determined by identifying the foveal depression in the depth map (e.g., as...). Figure 15 (as shown in the image), or determined by using an integrated retinal camera that records at an angle to the OCT instrument.

[0138] exist Figure 1A In the optical coherence tomography apparatus shown, a multi-length retardation element, in the form of a compound reflector 110, is located in the reference arm to apply a predetermined optical path length difference on the lateral separation portions 134, 138 of the reference beam 122. This allows for the single acquisition of interferometric data from multiple axially separated regions of a sample, such as an eye, thereby extending the depth of field of the apparatus. A similar effect can be achieved using a transmission element located in the sample arm, wherein the interferometer is configured such that the sample beam passes through the element before and after interacting with the sample, or only before or only after interacting with the sample.

[0139] Figure 18A The schematic depiction shows a transmission multi-length retardation element 1800, which is made of a single piece of glass or a material with a refractive index of [missing information]. n (λ) is composed of other transparent materials and has a first outer portion 1802 that is Δ thicker than the second inner portion 1804. If light in the sample beam 150 passes through the element 1800 both before and after interacting with the sample, as when the element is located Figure 1A As shown in the sample arm of the eye OCT device, the first outer portion 1806 of the sample beam will receive a delay 2Δ greater than that received by the second inner portion 1808. nThe delay of (λ). This is related to Figure 1A The reference arm compound reflector 110 shown provides the same effect, enabling the acquisition of interference data from the anterior sclera 106 and retina 144 in a single pass using the outer portion 1806 and inner portion 1808 of the sample beam 150. It will be understood that the inner portion 1804 of element 1800 can be omitted, in which case the element can be an annular glass plate of thickness Δ. As previously mentioned, the material of element 1800 can be selected to have a dispersion that at least partially compensates for the eye's dispersion, and if differential delay is not required, the element can be moved out of the sample beam path. Reference Figure 1A The element 1800 can be placed, for example, between the quarter-wave plate 156 and the microlens array 148. Alternatively, it can be located between the microlens array 148 and the 4F lens system 154, in which case a predetermined optical path length difference will be applied to a separate subgroup of the array of sample beams 152.

[0140] Figure 18B Another transmission multi-length delay element 1810 is schematically depicted for applying a predetermined optical path length difference across individual subgroups of the array of sample beams 152, or equivalently, applying a predetermined optical path length difference across different portions of the sample beam. In one embodiment, element 1810 includes a beamsplitter having a first fully reflective angled surface 1812 and a second partially reflective angled surface 1814. In combination, these angled surfaces are used to convert an array of sample beams 152, for example, generated using a microlens array (not shown), into a beam multiplexing group 1816 in which some beams 1818 travel a shorter optical path length than the other beams 1820. Reference Figure 1A The small-beam multiplexing group 1816 can be used, for example, to obtain interference signals from both the cornea 146 and the retina 144. In another embodiment, the first angular surface 1812 is partially reflective for providing a separate subgroup of small beams 1822 having the same optical delay as small beam 1818. In yet another embodiment, the first angular surface 1812 is partially reflective and the second angular surface 1814 is fully reflective for providing laterally spaced subgroups of small beams 1820, 1822 with different optical delays for obtaining interference signals, for example, from the anterior sclera 106 and the retina 144. In other embodiments, the first angular surface 1812 and the second angular surface 1814 have polarization-dependent reflectivity, such that the optical path lengths of the various small beams can be adjusted by polarization control, for example, using a polarizing layer appropriately positioned on the front surface 1824 or the rear surface 1826 of element 1810 or using an external polarizer.

[0141] It will be understood that the OCT device may alternatively be configured to have a transmissive multi-length delay element (such as element 1800 in the reference arm) or a reflective multi-length delay element (such as a composite reflector 110 in the sample arm), also for applying a predetermined optical path length difference over the lateral spacing portions of the reference beam or sample beam.

[0142] exist Figure 1A In this design, the composite reflector 110 is a component of a spectral domain OCT apparatus designed to perform single measurements of various structures in the eye 108 across a 2D grid of points. The eye is probed using a 2-D array of small beams 152, and the returning small beams interfere with and disperse onto individual pixel groups of a 2-D sensor array 178 for detection and subsequent processing. However, it will be understood that composite reflectors or other forms of multi-length delay elements can also be used to extend the depth of field of other types of OCT apparatuses, or to study non-eye samples over extended axial depth ranges. In one embodiment, the composite reflector can be placed in the reference arm of a scan-point spectral domain OCT apparatus, where interference signals from a series of points on the sample are dispersed onto a 1-D sensor array for sequential readout and processing. Predetermined optical path length differences applied to different portions of the reference beam are used to at least partially compensate for axial spacing between various structures of the sample, whether within a single frame or across different frames. In another embodiment, the composite reflector can be placed in the reference arm of the sweep source OCT device to extend the depth range that can be measured for interference signals, wherein a point detector is scanned in length as an adjustable or stepable light source.

[0143] Although the invention has been described with reference to specific embodiments, those skilled in the art will understand that the invention may be practiced in many other forms.

[0144] In addition, the following configurations may also be used in this disclosure.

[0145] 1. A method for performing optical coherence metrology across an extended region of the eye, the method comprising the following steps:

[0146] (i) Acquire a first optical coherence tomography image of the eye within a single frame of a two-dimensional sensor array, the first optical coherence tomography image containing data from a first region of the anterior surface of the eye and data from a third region of the eye;

[0147] (ii) Acquiring a second optical coherence tomography (OCT) image of the eye within a single frame of the two-dimensional sensor array, the second OCT image comprising data from a second region of the anterior surface that at least partially overlaps with the first region and data from a fourth region of the eye; and

[0148] (iii) Process the first optical coherence tomography image and the second optical coherence tomography image to record the overlapping portion of the first region and the second region of the anterior surface, thereby recording data from the third region and the fourth region of the eye.

[0149] 2. The method according to 1, wherein at least one of the first region and the second region of the anterior surface includes a portion of the anterior sclera.

[0150] 3. The method according to 1 or 2, wherein at least one of the first region and the second region of the anterior surface includes a portion of the limbus.

[0151] 4. The method according to any one of 1 to 3 above, wherein each of the first optical coherence tomography image and the second optical coherence tomography image is acquired within a time period of 2 milliseconds or less.

[0152] 5. The method according to 4, wherein each of the first optical coherence tomography image and the second optical coherence tomography image is acquired within a time period of 1 millisecond or less.

[0153] 6. The method according to 5, wherein each of the first optical coherence tomography image and the second optical coherence tomography image is acquired within a time period of 100 microseconds or less.

[0154] 7. The method according to any one of 1 to 6 above, wherein each of the first optical coherence tomography image and the second optical coherence tomography image contains data from a plurality of discrete points in a corresponding region of the front surface.

[0155] 8. The method according to any one of 1 to 7 above, wherein each of the third region and the fourth region of the eye includes a region of the retina.

[0156] 9. The method according to any one of 1 to 7, wherein each of the third region and the fourth region of the eye comprises a plurality of discrete points on the retina.

[0157] 10. The method according to any one of 1 to 9 above, wherein the position of the means for acquiring the first optical coherence tomography image and the second optical coherence tomography image is adjusted relative to the eye between the acquisition of the first optical coherence tomography image and the acquisition of the second optical coherence tomography image.

[0158] 11. The method according to any one of 1 to 10 above, wherein the internal delay in the apparatus for acquiring the first optical coherence tomography image and the second optical coherence tomography image is adjusted between the acquisition of the first optical coherence tomography image and the acquisition of the second optical coherence tomography image.

[0159] 12. The method according to any one of 1 to 11 above, wherein one or more lenses in the apparatus for acquiring the first optical coherence tomography image and the second optical coherence tomography image are changed between acquiring the first optical coherence tomography image and acquiring the second optical coherence tomography image.

[0160] 13. The method according to any one of 1 to 12 further includes the step of applying a predetermined optical path length difference on a laterally spaced first portion and a second portion of a reference beam or a sample beam when acquiring at least one of the first optical coherence tomography image and the second optical coherence tomography image, wherein the processing step further includes taking into account the predetermined optical path length difference.

[0161] 14. The method according to 13, wherein the predetermined optical path length difference is applied to a laterally spaced first portion and a second portion of the reference beam.

[0162] 15. The method according to 14, wherein the predetermined optical path length difference is applied by a composite reflector having an axially separated first reflective surface and a second reflective surface for reflecting the laterally spaced first portion and second portion of the reference beam.

[0163] 16. An apparatus for performing optical coherence metrology across an extended region of the eye, the apparatus comprising:

[0164] An interferometer is used to acquire a first optical coherence tomography (OCT) image and a second OCT image of an eye within a single frame of a two-dimensional sensor array. The first OCT image contains data from a first region of the anterior surface of the eye and data from a third region of the eye, and the second OCT image contains data from a second region of the anterior surface and data from a fourth region of the eye, wherein the first and second regions at least partially overlap.

[0165] A computer is used to process the first optical coherence tomography image and the second optical coherence tomography image to record the overlapping portion of the first and second regions of the anterior surface, thereby recording data from the third and fourth regions of the eye.

[0166] 17. The apparatus of claim 16, wherein the interferometer is configured such that, in use, at least one of the first region and the second region of the anterior surface includes a portion of the anterior sclera.

[0167] 18. The apparatus of claim 16 or 17, wherein the interferometer is configured such that, in use, at least one of the first region and the second region of the anterior surface includes a portion of the limbus.

[0168] 19. The apparatus according to any one of 16 to 18, wherein the interferometer is configured such that, in use, each of the third and fourth regions of the eye includes a region of the retina.

[0169] 20. The apparatus according to any one of 16 to 19, wherein the apparatus is configured such that each of the first optical coherence tomography image and the second optical coherence tomography image can be acquired within a time period of 2 milliseconds or less.

[0170] 21. The apparatus of claim 20, wherein the apparatus is configured such that each of the first optical coherence tomography image and the second optical coherence tomography image can be acquired within a time period of 1 millisecond or less.

[0171] 22. The apparatus of claim 21, wherein the apparatus is configured such that each of the first optical coherence tomography image and the second optical coherence tomography image can be acquired within a time period of 100 microseconds or less.

[0172] 23. The apparatus according to any one of 16 to 22, wherein the interferometer includes a spatial sampling element for providing a small beam array such that, in use, each of the first optical coherence tomography image and the second optical coherence tomography image contains data from a plurality of discrete points in a corresponding region of the front surface.

[0173] 24. The apparatus of claim 23, wherein the spatial sampling element is configured to provide focusing of different small beams at different depths in the eye.

[0174] 25. The apparatus according to 23 or 24, wherein the spatial sampling element comprises a two-dimensional microlens array.

[0175] 26. The apparatus according to any one of 23 to 25 further includes a structured perforated septum for suppressing crosstalk between small beams returning from the eye.

[0176] 27. The apparatus of claim 26, wherein the structured perforated partition includes a first member having a plurality of holes for allowing a small beam of light returning from the eye to pass through.

[0177] 28. The apparatus of claim 27, wherein the structured perforated partition includes a second member extending substantially parallel to the propagation direction of the on-axis small beam for suppressing the passage of off-axis light.

[0178] 29. The apparatus according to any one of 23 to 28, wherein the interferometer and the spatial sampling element are configured such that, in use, each of the third region and the fourth region of the eye includes a plurality of discrete points on the retina.

[0179] 30. The apparatus according to any one of 16 to 29, wherein the interferometer includes one or more lenses adapted to interchange between the acquisition of the first optical coherence tomography image and the acquisition of the second optical coherence tomography image.

[0180] 31. The apparatus according to any one of 16 to 30, wherein the interferometer includes a multi-length delay element for applying a predetermined optical path length difference on a laterally spaced first portion and a second portion of a reference beam or a sample beam when acquiring at least one of the first optical coherence tomography image and the second optical coherence tomography image, and wherein the computer is configured to take into account the predetermined optical path length difference when processing the respective optical coherence tomography image.

[0181] 32. The apparatus of claim 31, wherein the multi-length delay element is configured to apply the predetermined optical path length difference over a laterally spaced first portion and a second portion of the reference beam.

[0182] 33. The apparatus of claim 32, wherein the multi-length delay element comprises a composite reflector having an axially separated first reflective surface and a second reflective surface for reflecting the laterally spaced first portion and second portion of the reference beam.

[0183] 34. The apparatus of claim 33, wherein the composite reflector includes a medium selected to have dispersion, the dispersion at least partially compensating for the dispersion of the eye.

[0184] 35. The apparatus according to 33 or 34, wherein the composite reflector is selected such that the predetermined optical path length difference substantially compensates for the axial depth of the eye.

Claims

1. A method for measuring eye shape, the method comprising the following steps: (i) In the first acquisition, an optical coherence tomography apparatus with a first optical repeater is used to measure the anterior segment of the eye and the axial depth of the eye; (ii) Calculate the refractive characteristics of the anterior segment of the eye based on the data obtained in the first acquisition; (iii) In the second acquisition, the optical coherence tomography apparatus having a second optical repeater calibrated to the first optical repeater is used to capture an image of the retina of the eye on a dot grid; (iv) Determine the axial and angular positions of the second acquisition relative to the first acquisition; and (v) Using the calculated refractive properties of the anterior segment of the eye, determine the corrected retinal shape based on a correction formula or by using an optical model.

2. The method according to claim 1, wherein, The preceding segment is measured simultaneously on the point grid during the first acquisition.

3. The method according to claim 1 or claim 2, wherein, The axial depth was measured to the retinal pigment epithelium at the fovea of ​​the eye.

4. The method according to claim 1, wherein, Identify the fovea of ​​the eye from the image of the retina.

5. An optical coherence tomography apparatus for measuring the shape of an eye, the apparatus being configured to: In the first acquisition using the first optical repeater, the anterior segment of the eye and the axial depth of the eye are measured; The refractive characteristics of the anterior segment of the eye are calculated based on the data obtained in the first acquisition; An image of the eye's retina is captured on a dot grid during a second acquisition using a second optical repeater calibrated to the first optical repeater; Determine the axial and angular positions of the second acquisition relative to the first acquisition; and Using the calculated refractive properties of the anterior segment of the eye, the corrected retinal shape is determined based on a correction formula or by using an optical model.

6. The apparatus according to claim 5, wherein, The device is configured to simultaneously measure the front segment on a point grid during the first acquisition.

7. The apparatus according to claim 5 or claim 6, wherein, The device is configured to measure the axial depth of the retinal pigment epithelium at the fovea of ​​the eye.

8. The apparatus according to claim 5, wherein, The device is configured to identify the fovea of ​​the eye from the image of the retina.

9. A method for performing optical coherence metrology or tomographic imaging of a sample, the method comprising the following steps: (i) Split the light from the light source into a sample beam and a reference beam; (ii) Apply a predetermined optical path length difference to the first and second portions of the sample bundle or the reference bundle that are laterally spaced apart; (iii) Guide the sample bundle onto the sample to interact with the first and second regions of the sample that are axially separated, and collect light reflected or transmitted from the first and second regions of the sample that are axially separated; (iv) Mix the reference beam with reflected or transmitted light; (v) Detecting the interference signal generated by the mixing of the reference beam with the reflected light or the transmitted light; as well as (vi) Process the detected interference signal to provide an optical coherence tomography image of the sample. The predetermined optical path length difference at least partially compensates for the axial spacing between the first region and the second region of the sample.

10. The method according to claim 9, wherein, The sample bundle includes an array of small bundles for interacting with multiple discrete points within the first or second region of the sample.

11. The method according to claim 9 or claim 10, wherein, The predetermined optical path length difference is applied to the laterally spaced first and second portions of the reference beam.

12. The method according to claim 11, wherein, The predetermined optical path length difference is applied by a composite reflector having an axially separated first and second reflective surface for reflecting the reference beam, which are laterally spaced apart from the first and second portions.

13. An apparatus for performing optical coherence metrology or tomographic imaging of a sample, the apparatus comprising: light source; Interferometer, used for: The light from the light source is split into a sample beam and a reference beam; The sample beam is guided onto the sample to interact with the axially separated first and second regions of the sample, and to collect light reflected or transmitted from the axially separated first and second regions of the sample. and The reference beam is mixed with reflected or transmitted light; A detector is used to detect the interference signal generated by the mixing of the reference beam with the reflected light or the transmitted light; A multi-length delay element is used to apply a predetermined optical path length difference on a laterally spaced first and second portion of the sample bundle or the reference bundle; as well as A processor is used to process the detected interference signals to provide an optical coherence tomography image of the sample. The multi-length delay element is selected such that the predetermined optical path length difference at least partially compensates for the axial spacing between the first region and the second region of the sample.

14. The apparatus of claim 13, further comprising a spatial sampling element for generating a small array of small bundles from the sample bundle for interacting with a plurality of discrete points within the first or second region of the sample.

15. The apparatus according to claim 14, wherein, The spatial sampling element includes a small lens array.

16. The apparatus according to any one of claims 13 to 15, wherein, The multi-length delay element is configured to apply the predetermined optical path length difference over a first and a second portion of the reference beam that are laterally spaced apart.

17. The apparatus according to claim 16, wherein, The multi-length delay element includes a composite reflector having an axially separated first and second reflective surface for reflecting the reference beam, which are laterally spaced apart from the first and second portions.

18. The apparatus according to claim 13, wherein, The multi-length delay element includes a medium selected to have dispersion, which at least partially compensates for the dispersion of the sample.

19. An article of manufacture comprising a computer-usable medium having computer-readable program code configured to implement the method according to any one of claims 1 to 4, 9 to 12, or to operate the apparatus according to any one of claims 5 to 8, 13 to 18.

Images