Hybrid fiber-based interferometer design with dispersion for complex conjugate resolution and related embodiments

Abstract

A high-dispersion single-mode hybrid optical fiber (1900) located in one of the reference arm or probe arm of an optical interferometer, wherein the hybrid fiber (1900) comprises at least two optical fibers (1902,1902), at least one of the at least two optical fibers having a different core diameter and at least one of the at least two optical fibers having different dispersion characteristics, the at least two optical fibers being fused together at their ends to form a hybrid optical fiber, and each of the at least two optical fibers having a length based on the core diameter of the optical fiber with respect to the central wavelength of the light beam passing through the hybrid optical fiber and a target GDD per unit length based on the target length of the hybrid optical fiber, wherein the hybrid optical fiber adds an additional GDD value compared to an optical fiber in the other of the reference arm or probe arm of an optical interferometer.

Description

[Technical Field]

[0001] This disclosure relates to a hybrid fiber-based differential-dispersive interferometer design, and more particularly to a design suitable for use with high-dispersion techniques for removing residual complex conjugate image artifacts from 2D image scans, such as optical coherence tomography (OCT) B-scan images.

[0002] Optical coherence tomography (OCT) is an imaging modality that uses the principle of low-coherence interferometry to produce a three-dimensional image of a sample. An OCT system generally consists of a broadband light source, a reference arm and a sample optical arm, and a detection arm consisting of either a spectrometer or a photodiode detector. The interference patterns of light reflected from the reference arm and sample arm are measured by the detector and electronically processed to generate a tomographic image showing the relative positions of the reflectors within the sample. Scanning the beam within the sample arm allows for the matching of different spatial positions and thus enables the construction of a 3D image of the sample.

[0003] OCT signal processing requires multiple steps, one of which is the Fourier transform of the detected interference signal. Since the measured signal is real-valued, the Fourier transform yields a complex signal with identical positive and negative frequency components. This mirroring of data is known as complex conjugate artifact, limiting the usable imaging range to half of the theoretically possible range. Techniques for removing or suppressing conjugate artifacts are known as complex conjugate resolution (CCR) methods, which can result in an immediate doubling of the imaging range in OCT. However, known systems and methods for CCR are impractical in many situations due to the expensive and complex optical components that must be added to the OCT scanning system. Furthermore, multiple image acquisitions are required to generate the phase information necessary to remove the conjugate image. This slows down the imaging time, degrades system performance, and makes the system highly susceptible to sample motion, especially when imaging biological subjects.

[0004] Optical coherence tomography (OCT) is performed using optical instruments that enable the generation of cross-sectional images of biological tissue. Using monochromatic light with a constant phase difference, it is possible to achieve axial (depth) resolution far below 8 microns. Therefore, such OCT systems are desirable when probing biological tissue (in vivo), both in real time and in other applications, where they can be used to generate scans. Because OCT scans cannot penetrate to great depths, they are particularly useful for probing skin tissue and in ophthalmology. Different OCT scan images are constructed from many one-dimensional scans (A scans) performed at multiple depths to create a two-dimensional image (B scan). By acquiring B scans quickly and at sufficient close range, a three-dimensional image (C scan) of the OCT-probeled sample tissue can be obtained.

[0005] However, various technical issues present challenges that affect how OCT scan images are developed in applications where real-time streaming of OCT scan images may be hindered.

[0006] One of these technical challenges is a method for rapidly removing complex conjugate image artifacts in OCT scan images. By using the dispersion mismatch of known techniques between the sample arm and reference arm in frequency-domain OCT systems, complex conjugate artifacts can be iteratively suppressed and the imaging range increased. A fast dispersion encoded full-range DEFR algorithm that detects multiple signal components in each iteration is disclosed by Hofer et al. in the paper "Fast dispersion encoded full range optical coherence tomography for retinal imaging at 800nm ​​and 1060nm" Vol.18, No.5, Optics Express 4898, March 2010. However, although faster than previous techniques known in the art, the disclosed technique is still relatively slow, taking approximately 5-10 seconds to process a single image. This means that, while much faster than the techniques previously provided in the exemplary OCT dispersed system described by Hofer et al. in “Dispersion encoded full range frequency domain optical coherence tomography”, Optics Express, 17(1), 2009, it is not suitable for live image processing applications such as complex conjugate image removal from OCT scan images generated in real time during retinal ophthalmic surgery. Both algorithms described by Hofer in these papers are extremely slow when processing full-range images, hindering their use in real-time applications. Hofer et al.'s algorithm further describes the use of static selection of critical processing parameters, which requires manual optimization of processing parameters for specific image datasets. This limits the use of this method when imaging different types of samples under different imaging conditions due to variability in signal intensity and image clarity.

[0007] Summary of the Invention The disclosed technology attempts to mitigate or eliminate at least some of the limitations of the prior art by using a hybrid fiber-based interferometer design and to improve the complex conjugate resolution in OCT scanner applications. In particular, some embodiments of the disclosed technology can improve some of the capabilities of the disclosed methods for CCR executed in real time, but are not limited thereto.

[0008] The following summary description shows features of the disclosed technology that may be preferred features in some embodiments. The present invention is presented by the appended claims.

[0009] A first aspect of the disclosed technology is a high-dispersion single-mode hybrid optical fiber located in one of the reference arm or the probe arm of an optical interferometer imaging system, the hybrid fiber comprising at least two optical fibers, at least one of the at least two optical fibers having a different core diameter and different dispersion characteristics from at least one other optical fiber of the at least two optical fibers, the at least two optical fibers being fusion spliced end to end to form the hybrid optical fiber, each of the at least two optical fibers having a length based on the core diameter of the optical fiber with respect to the center wavelength of the optical beam passing through the hybrid optical fiber and a target GDD per unit length based on the target length of the hybrid optical fiber, and the hybrid fiber adding an additional GDD value as compared to the optical fiber in the other of the reference arm or the probe arm of the optical interferometer.

[0010] In some embodiments, the additional GDD value is between 31000 (fs 2 ) and 46000 (fs 2 ).

[0011] In some embodiments, at least one type of optical fiber has a length different from the length of at least one other optical fiber in the hybrid optical fiber.

[0012] In some embodiments, the length of each optical fiber is determined by calculating the target group velocity delay (GVD) for a hybrid optical fiber of a predetermined length, converting the target GVD to a target optical fiber dispersion parameter (OFDP) for the central wavelength of light passing through the hybrid optical fiber, determining at least two optical fiber types each having an OFDP bounding the target OFDP, converting the OFDP of each determined type of optical fiber to the GVD at the central wavelength, and determining the length of each fiber based on the GVD of each fiber at the central wavelength, such that when the optical fibers are fused end-to-end, they are collectively determined to achieve an optical path that matches the predetermined optical path length of the hybrid optical fiber.

[0013] In some embodiments, the hybrid optical fiber comprises a 630-HP fiber from Coherent of a predetermined length and a HI780 fiber from Corning of a predetermined length.

[0014] In some embodiments, the hybrid optical fiber is located in the reference arm of an optical coherence imaging system comprising an OCT device.

[0015] In some embodiments, the hybrid fiber is configured to introduce a predetermined level of wavelength dispersion into the reference arm of the optical interferometer to remove complex conjugate image data from the OCT image output by the OCT device.

[0016] In some embodiments, the hybrid optical fiber is located in the reference arm of an optical interferometer configured to output OCT imaging data from an OCT device. The ratio of the two constituent fibers forming the hybrid fiber may be such that, for a hybrid optical fiber path length of 6 meters, 5 meters consist of Coherent 630-HP fiber and 1 meter consists of Corning HI780 fiber. In some embodiments, these optical fibers can be replaced with optical fibers having the same or similar optical properties, such as those listed in Table 1 of the detailed description, for example, other glass having the same set of optical properties, including at least the same refractive index, group refractive index, and clarity.

[0017] Another aspect of the disclosed technology comprises an OCT assembly having an OCT interferometer assembly, the OCT interferometer assembly comprising an OCT detector assembly, a sample arm configured to guide an OCT probe beam from the OCT light source of the OCT assembly toward a target and a return OCT probe beam from the scanned target toward the OCT detector assembly, and an OCT system reference assembly with adjustable optical path length comprising a hybrid optical fiber according to the first aspect or one of the embodiments thereof disclosed herein, wherein the reference assembly is configured on the reference arm of the OCT detector assembly, and the OCT light from the OCT light source is split to travel along the reference arm as a reference beam and along the sample arm as an OCT probe beam, the return reference beam and the return probe beam are coupled, and the OCT detector assembly is configured to detect interference in the coupled OCT light returning from the reference arm and the sample arm.

[0018] In some embodiments, the OCT assembly further comprises an image processor, and the OCT detector of the OCT interferometer assembly is configured to output a signal to the image processor containing the detected interference pattern of the returned coupled OCT light, and the interference patterns of the returned OCT reference light and OCT probe light are Fourier transformed by the image processor.

[0019] In some embodiments, the image processor is configured to perform a computer-implemented complex conjugate resolution (CCR) method to remove complex conjugate artifacts from the Fourier-transformed signal, and the reference beam path in the reference arm of the hybrid glass optical fiber OCT system achieves sufficient chromatic dispersion to enable the CCR method to remove CC artifacts in real time.

[0020] In some embodiments, wavelength dispersion along the hybrid glass fiber is sufficient to enable the computer-implemented CCR method to remove complex conjugate artifacts from OCT B scans or stereoscopic scans in real time.

[0021] In some embodiments of the disclosed technology, the high-dispersion retroreflector comprises a filter glass that is transparent at least in the near-infrared (IR) wavelength and configured to cause differential dispersion of incident broadband low-coherent light at least in the near-infrared (NIR) wavelength.

[0022] In some embodiments, the retroreflector is transparent over the same wavelength range over which differential dispersion occurs, but in other embodiments, it may be transparent over a different wavelength range over which differential dispersion occurs.

[0023] In some embodiments, the median group delay dispersion of the filter glass is 38000 (fs 2 )~40000(fs 2 It is within the range of ).

[0024] In some embodiments, the median group dispersion rate of the filter glass is 1100 fs 2 / mm~1280fs 2 This is a range value of / mm.

[0025] In some embodiments, the retroreflector has the following properties for incident light with a spectrum centered at 850 nm, namely a refractive index of 2.5129 for light having a wavelength of 850 nm, a group refractive index of 2.7268 (ng) for light having a wavelength of 850 nm, a group velocity delay of 1120.75 fs 2 / mm, and a glass having one of a transparency of 95.7% for light having a wavelength of 850 nm.

[0026] In some embodiments, the retroreflector has an external conical shape, and the interior of the cone includes at least three mirror facets collectively configured to perform retroreflection of incident light.

[0027] In some embodiments, the disclosed technology includes a bulk glass differential dispersion interferometer assembly for extended depth imaging in optical coherence tomography (OCT), the interferometer assembly including an automated path length optical-mechanical assembly including a first fixed retroreflector located at one end of the optical path and a second adjustable retroreflector located in the same place as a fixed high-dispersion retroreflector on a movable mount to form an adjustable optical path within the interferometer assembly, the high-dispersion retroreflector including filter glass transparent at infrared (IR) wavelengths and configured to cause differential dispersion at near-infrared (NIR) wavelengths between broadband low-coherent incident light.

[0028] In some embodiments, the interferometer assembly is located within the probe arm of an OCT scanning system, and the high-dispersion retroreflector is configured to cause differential dispersion at near-infrared (NIR) wavelengths between broadband low-coherent incident light returning from the reference arm and the probe arm of the OCT system.

[0029] In some embodiments, the interferometer is configured to output light for complex conjugate resolution of incident OCT light.

[0030] In some embodiments, the median group delay dispersion of the filter glass material is 38000 (fs 2 )~40000 (fs 2It is within the range of ).

[0031] In some embodiments, the median group dispersion rate of the filter glass material is 1100 fs 2 / mm~1280fs 2 This is a range value of / mm.

[0032] In some embodiments, the high-dispersion retroreflector (1500) has a refractive index of 2.5129 for light with a wavelength of 850 nm, a group refractive index of 2.7268 (ng) for light with a wavelength of 850 nm, and 1120.75 fs for incident light having a spectrum centered at 850 nm. 2 The glass has one of the following characteristics: a group velocity delay of 1 / mm and 95.7% transparency for light with a wavelength of 850nm.

[0033] In some embodiments, the high-dispersion retroreflector may comprise IRG27 glass, such as that manufactured by Schott_IRG.

[0034] In some embodiments, the first retroreflector (1604) and the second retroreflector (1602) have a refractive index of 1.5098 for light with a wavelength of 850 nm, a group refractive index of 1.5249 (ng) for light with a wavelength of 850 nm, and 40.13 fs for incident light having a spectrum centered at 850 nm. 2 It features glass with a group velocity delay of 1 / mm and 99.8% transparency for light with a wavelength of 850nm.

[0035] In some embodiments, the first and second retroreflectors may comprise BK7 glass, such as that manufactured by SCHOTT.

[0036] In some embodiments, the high-dispersion retroreflector has a conical exterior, and the interior of the cone comprises at least three specular facets collectively configured to perform retroreflection of incident light.

[0037] In some embodiments, the disclosed technology includes an optical coherence tomography (OCT) apparatus configured to perform real-time OCT, the apparatus including an illumination arm with at least an optical light source for OCT, a reference arm, an OCT probe arm from which an OCT probe beam is emitted, a data or output arm through which the returned OCT light passes and is output as a signal processed by an image processor, and at least one dispersed retroreflector in the reference arm or OCT probe arm according to the first embodiment or any of the embodiments thereof disclosed herein.

[0038] In some embodiments, the variance between the reference arm and the probe arm is variable and set above a minimum threshold for separating the complex conjugate image from the OCT image output for display.

[0039] In some embodiments, the OCT device further comprises at least one additional distributed component provided on either the reference arm or the OCT probe arm.

[0040] In some embodiments, at least one additional distributed component is located within the reference arm and comprises a distributed optical fiber.

[0041] In some embodiments, at least one additional dispersion component is located within the reference arm and includes a dispersion glass window, and the physical path length of the reference arm is configured to compensate for the dispersion window, or the physical path length of the opposite OCT probe arm is extended to compensate for the dispersion window.

[0042] In some embodiments, the OCT apparatus comprises a bulk glass differential-dispersive interferometer assembly for extended depth imaging in optical coherence tomography (OCT), and the interferometer assembly comprises an automated path length optics-mechanical assembly.

[0043] In some embodiments, the OCT apparatus of the third embodiment includes an OCT scanner adapter according to any of the embodiments disclosed herein.

[0044] In some embodiments, at least one dispersive optical component is provided within the OCT probe arm and includes one or more of a dispersive optical fiber, a dispersive dichroic mirror, a dispersive OCT objective lens, and a dispersive OCT field lens.

[0045] In some embodiments, the image processor can use distribution to perform a computer-implemented image processing complex conjugate resolution (CCR) method for removing complex conjugate image data from image data, for example in real time, the method comprising: receiving an image signal containing image data containing complex conjugate image data (902); performing baseline signal subtraction (906); resampling the obtained wavelength data to generate linear wavenumber image data (908, 910); processing the linear wavenumber image data using at least one iteration of a CCR image processing algorithm to generate a complex conjugate decomposition (CCR) result; generating a CCR image calculated from the CCR result; and separating the CCR image from the received OCT image data to remove the complex conjugate image data.

[0046] In some embodiments, the CCR image processing algorithm uses an adjustable threshold for each iteration step.

[0047] Advantageously, by adjusting the threshold for each iteration step, it is possible to generate CCR images more quickly.

[0048] Advantageously, the initial threshold can be determined for each individual scanned image by applying an initial threshold based, for example, on a frequency-versus-amplitude histogram obtained from the Fourier transform of the image. The initial threshold may then be set to a percentile of the histogram above a certain value.

[0049] Another advantage of the disclosed image processing method is that, since the processing parameters are selected based on the characteristics of the original image, the image processing method according to one of the disclosed embodiments can optimally select the processing parameters and select an adaptive threshold level before performing any iterative complex conjugate resolution processing. In other words, in some embodiments, a prediction of what the optimal threshold should be for each image is provided.

[0050] Instead of iteratively processing OCT scan images to select a range of different static thresholds and choose each static threshold based on the final image result of what the optimal threshold should be for each iteration, the threshold is dynamically adjusted at each threshold by an embodiment of the image processing method using the CCR algorithm according to the disclosed technique.

[0051] Secondly, the ability to do all of this in real time (<30ms) enables real-time video processing through combinations of processing methods, the use of dedicated GPUs, and the selection of system distribution parameters.

[0052] In some embodiments, the algorithms according to the disclosed technology are implemented using a dedicated processor or processing circuit. For example, in some embodiments, the algorithms may be implemented using a graphics processing unit (GPU). In some embodiments, the method is performed in real time.

[0053] For example, using some embodiments of the disclosed technology, images can be generated in less than 30 milliseconds. This allows the CCR images to be used in an OCT system for applications such as surgical procedures, including ophthalmic surgery, where it is important that the images are generated in real time without excessive delay during surgical procedures.

[0054] In some embodiments, the generated CCR image data calculated from the CCR results includes size and / or phase data of the obtained CCR image.

[0055] In some embodiments, the method further includes performing logarithmic scaling of the obtained CCR images. This can be helpful in visualizing the data when it has a range of sizes spanning several orders of magnitude.

[0056] In some embodiments, processing linear wavenumber image data to generate complex conjugate resolution results involves performing multiple iterations of a CCR image processing algorithm, the CCR image processing algorithm comprising: applying variance correction to the linear wavenumber image signal data; performing a signal transformation, such as a Fourier transform (e.g., Fast Fourier Transform (FFT)); calculating the magnitude of the result of performing the signal transformation on the linear wavenumber image signal data; calculating a variable threshold for each iteration of the algorithm; setting the signal transformation result to zero for each signal transformation result value whose magnitude does not meet the criteria for storage based on the threshold for the current iteration; storing the signal transformation result for each signal transformation result value whose magnitude meets the criteria for storage based on the threshold for the current iteration; calculating an inverse signal transformation, such as an inverse FFT, for all stored signal transformation results; applying inverse variance correction; extracting the real image component and subtracting the result from the start image spectral data.

[0057] In some embodiments, the signal transformation may include a Fourier transform that decomposes the input signal into sinusoidal components with discrete frequencies; however, some embodiments of the image processing methods disclosed herein may instead use alternative signal transformations, such as suitable wavelet transforms.

[0058] In some embodiments, matching the conditions for storing the frequency components of an input signal having an amplitude of a given frequency bandwidth includes matching or exceeding a calculated variable memory condition threshold amplitude value for storing those frequency components of an OCT scan image data.

[0059] In some embodiments, meeting the conditions for storing the signal conversion result includes exceeding a calculated (variable) storage condition threshold.

[0060] Advantageously, since the memory condition threshold is not static, some embodiments of the disclosed technology can provide better automated optimization of processing parameters for a particular image dataset.

[0061] Advantageously, the variable storage condition threshold in some embodiments allows different types of samples to be imaged under different imaging conditions due to the variability of signal intensity and image clarity.

[0062] In some embodiments, after the final iteration has been performed, the method further optionally includes adding any remaining iteration residual signals to the final output signal.

[0063] In some embodiments, the algorithm is performed for each A scan, and the A scans are then stacked to generate B scans of the scanned tissue sample or other object of interest.

[0064] In some embodiments, several iterations of the CCR algorithm are performed to extract real image components and subtract the results from the starting image spectral data of that iteration until the stored signal conversion result values ​​include a complex numerical image without any significant conjugate image artifacts.

[0065] In some embodiments, the method further includes performing signal apodization, which is an optional processing parameter set by the user that helps to adjust the input signal so that it has zero values ​​at each end, and helps to reduce edge artifacts when performing signal transformations in the image processing algorithm by the disclosed technique.

[0066] In some embodiments, the calculated variable threshold is based on an empirically derived formula.

[0067] In some embodiments, the variable threshold is calculated using the derived formula.

[0068] In some embodiments, the variable threshold is calculated using a threshold based on image characteristics, such as a histogram-based intensity distribution.

[0069] Advantageously, this allows the variable threshold to be a dynamically adjusted threshold based on one or more image characteristics of the current image. These characteristics can change in response to the optical matching of the sample or other dynamic imaging conditions.

[0070] In some embodiments, the method is implemented using a graphics processing unit capable of processing images in less than 30 milliseconds.

[0071] In some embodiments, the image data is OCT image data, and the method further includes outputting an OCT image based on the received image data from which the complex conjugate image data has been removed.

[0072] In some embodiments, the output OCT image does not have a perceptible complex conjugate image when displayed.

[0073] According to another second aspect of the disclosed technology, an optical coherence tomography (OCT) apparatus configured to perform real-time OCT comprises at least an optical light source, a reference arm, an illumination arm including an OCT probe arm from which an OCT probe beam is emitted, and a data arm through which return OCT light is processed by an image processor (148) configured to perform a method according to the first aspect and / or at least one of its embodiments disclosed herein.

[0074] In some embodiments of the OCT device, the reference arm and probe arm exceed the minimum design threshold for separating the complex conjugate image from the OCT image output for display.

[0075] In some embodiments of the OCT device, the OCT device further comprises at least one distributed component provided on one of the reference arm or probe arm.

[0076] In some embodiments of the OCT apparatus, at least one dispersion component in a reference arm comprises a dispersion optical fiber, a dispersion glass window in the reference arm configured such that the physical path length of the reference arm compensates for the dispersion window, or the physical path length of an opposing OCT probe arm is extended to compensate for the dispersion window, and one or more dispersion retroreflectors in the reference arm, the amount of dispersion determined by the optical path length through the dispersion retroreflector.

[0077] In some embodiments of the OCT apparatus, at least one dispersive optical component provided within the OCT probe arm includes one or more of a dispersive optical fiber, a dispersive dichroic mirror, a dispersive OCT objective lens, and a dispersive OCT field lens.

[0078] According to another aspect of the disclosed technology, the present invention includes a computer program product comprising computer code that, when loaded from memory and executed on one or more processors or processing circuits of the device, is configured to cause the device to implement the method disclosed herein.

[0079] According to another aspect of the disclosed technology, the image processor includes one or more processors or processing circuits, including a graphics processing unit, and the image processor is configured to execute computer code, when executed, causing the image processor to implement a complex conjugate resolution method according to any one of the embodiments disclosed herein.

[0080] Advantageously, the OCT scanner system may include exemplary embodiments of the MEMS scanning mirror assembly disclosed herein within the OCT scanner adapter 206 for a microscope. The system design of the OCT scanner adapter 206 has a compact configuration in the sense that it is laterally compact, as the optical design of the MEMS scanning mirror allows the optical channel formed by the microscope optics and the mounted OCT scanner objective lens to require an optimally short housing stack height, the optical path that the probe light travels within the scanning mirror assembly block is less than 40 mm, and it supports a high scanning speed with a resolution of 6 microns or less in the resulting OCT image.

[0081] This is useful when a surgeon needs to use a microscope or similar device to generate a magnified image of the surgical area using a microscope optics, allowing the surgeon to better view the surgical area while keeping the patient within reach of the surgeon's arm during ophthalmic surgery. In other words, some embodiments of the OCT scanner system designs disclosed herein result in a combined stack height of the microscope and the mounted OCT scanner adapter 206 that is much shorter than previously possible. The design better balances design constraints, allowing the surgeon to view the area being scanned by the OCT scanner through one or more eyepieces of the microscope and keep the scanned area within the focal plane of the microscope optics, while still allowing the surgeon to physically reach the scanned area to perform the surgical procedure.

[0082] Other aspects of the compact design offer additional advantages. For example, the design of the scanning mirror assembly is advantageous in that it reflects a beam used for feedback of the scanning mirror position in an optical plane different from that used by the OCT probe beam, and the optical path of the reference beam used to determine the scanning mirror position is advantageously configured to reduce the possibility of the return light from the feedback arm contaminating the mirror position reference beam or its light source, or contaminating the OCT probe beam.

[0083] The embodiments described above, the appended claims, and / or the examples disclosed above and below herein can be appropriately combined with each other, as will be apparent to those skilled in the art.

[0084] Additional features and advantages are disclosed in the following description, claims, and drawings, and it may be readily apparent that such features disclosed in the context of one aspect or embodiment above can be combined with those disclosed in the description of a person skilled in the art. [Brief explanation of the drawing]

[0085] Herein, some embodiments of the disclosed technology will be described, merely as examples, with reference to the accompanying drawings. [Figure 1] This diagram schematically illustrates the basic principles of a spectral region OCT system. [Figure 2A] This figure schematically shows front and rear perspective views of an OCT scanner adapter 206 for a microscope, according to several embodiments of the disclosed technology. [Figure 2B] This figure schematically shows front and rear perspective views of an OCT scanner adapter 206 for a microscope, according to several embodiments of the disclosed technology. [Figure 3A] This figure schematically shows various components of an example of an OCT scanner adapter 206 according to several embodiments of the disclosed technology. [Figure 3B] This figure schematically shows various components of an example of an OCT scanner adapter 206 according to several embodiments of the disclosed technology. [Figure 4] Figures 3A and 3B show enlarged views of the OCT scanner adapter 206. [Figure 5A] This figure schematically illustrates an example of the optical design of a MEMS scanning mirror assembly according to several embodiments of the disclosed technology. [Figure 5B] This figure schematically shows further details of the input arm 518 in Figure 5A. [Figure 6] Figure 5A schematically shows an example of a collimating lens assembly for the input arm. [Figure 7] This figure schematically illustrates an example of an objective lens assembly for a MEMS scanning mirror assembly according to several embodiments of the disclosed technology. [Figure 8A] This figure shows an example of OCT images and layered phantom CCR image data of a contact lens. [Figure 8B] This figure shows the OCT image of Figure 8A, which does not have CCR image data. [Figure 9] This figure shows an example of an image processing method for removing complex conjugate image data from image data, according to several embodiments of the disclosed technology. [Figure 10] This figure shows an example of an algorithm for generating signal transformations without conjugate image effects, based on several embodiments of the disclosed technology. [Figure 11A] This figure schematically illustrates further details of two examples of the algorithm shown in Figure 10. [Figure 11B] This figure schematically illustrates further details of two examples of the algorithm shown in Figure 10. [Figure 12] This figure schematically illustrates an image processing apparatus configured to implement a method for removing CCR image data from OCT images, according to several embodiments of the disclosed technology. [Figure 13] This figure schematically shows an example of a system according to one embodiment of the disclosed technology. [Figure 14] This figure schematically illustrates an example of a method according to several embodiments of the disclosed technology. [Figure 15A] This figure schematically illustrates different diagrams of retroreflectors according to several embodiments of the disclosed technology. [Figure 15B] This figure schematically illustrates different diagrams of retroreflectors according to several embodiments of the disclosed technology. [Figure 16] This figure shows an example of a reference arm assembly according to several embodiments of the disclosed technology. [Figure 17]This figure schematically illustrates an example of another method according to several embodiments of the disclosed technology. [Figure 18] This figure schematically illustrates an example of another method according to several embodiments of the disclosed technology. [Figure 19A] This diagram schematically illustrates hybrid optical fibers according to several embodiments of the disclosed technology. [Figure 19B] This diagram schematically illustrates hybrid optical fibers according to several embodiments of the disclosed technology.

[0086] Detailed explanation The detailed description below provides examples of embodiments of the disclosed technology, which are described in sufficient detail to enable those skilled in the art to carry out the disclosed technology.

[0087] There are two forms of OCT scanning: time-domain OCT (TD-OCT) and spectral-domain OCT (SD-OCT). SD-OCT uses spectral matching of the spectrum in the OCT interferometer output.

[0088] Figure 1 schematically illustrates the operating principle of an exemplary spectral-domain optical coherence tomography (SD-OCT) interferometer scanner system 100, including some examples of embodiments of the disclosed technology.

[0089] In the exemplary SD-OCT system 100 shown in Figure 1, the SD-OCT system 100 can be used to generate an optical coherence tomography image of an in vivo tissue sample 116, such as a human eye, by probing into the tissue sample 116 using an OCT optical scanning beam.

[0090] System 100 is schematically shown in Figure 1 and it will be clear that it is not drawn to scale. The positions and relative sizes of the various components of the SD-OCT system 100 shown in Figure 1 do not necessarily reflect their actual or relative positions or sizes in exemplary embodiments of the disclosed technology.

[0091] Hereinafter, references to OCT scan images or image data may, as will be apparent to those skilled in the art, refer to, as necessary, one-dimensional A scans, two-dimensional B scans including multiple A scans, or stereoscopic scan images including multiple B scans.

[0092] As shown in Figure 1, the SD-OCT system 100 includes a low-coherence broadband optical scanning light source 102. The scanning light source 102 is appropriately connected to a coupler 104 configured to split the light from the light source 102 into an OCT optical reference beam following an optical path 103a along a reference arm 103 and an OCT optical probe or scanning beam following an optical path 105a along an OCT probe arm 105. The OCT light returned along the reference arm 103 and probe arm 105 has different phase shifts that produce interference when the returned light is recombined at the coupler 104. The combined optical signal is output from the coupler along a detection or output arm 107, and the optical interference pattern is detected using a spectrometer 136. The output optical signal 146 from the spectrometer 136 is then processed by an image processor 148, for example, to apply a Fourier transform to the output optical signal 146, which then generates OCT scanning data that can be displayed on a suitable display 152.

[0093] The resulting interference pattern, which is the different phase shift between the OCT light returned from the reference arm and the OCT light returned from the probe arm, occurs because the OCT light is returned from different depths in the scanned tissue sample 116 or from one or more different structures within the scanned tissue sample 116. In some embodiments, the scanned tissue sample may instead include a different type of object of interest 112 than the in vivo tissue sample located in a region of the human body.

[0094] The phase shift that generates interference is influenced by the different depths returned by structures within the sample scanned by the OCT light. The interference from the phase shift allows the signal output 146 of the spectrometer 136 to generate an image known as tomography, which provides visual indication of the depth and location of one or more such structures within the scanned or probed region.

[0095] In some embodiments of the SD-OCT system 100 shown in Figure 1, the broadband OCT light source 102 has a center wavelength of 860 nm over a bandwidth of 100 nm. In some embodiments, two or more light sources 102 are used to realize broadband low-coherence OCT scanning light over a desired bandwidth.

[0096] The probe OCT beam is returned after being backscattered, reflected, or otherwise returned from any structure at a specific depth within region 116 containing the tissue sample being scanned. In some embodiments, one or more or all of the optical paths 101a, 103a, 105a, 107a are realized using a suitable single-mode optical fiber and may include one or more sections in which the beam following the optical fiber travels through free space.

[0097] In the embodiment of the SD-OCT system 100 schematically shown in Figure 1, the reference beam exits from the coupler 104, travels along the reference arm 103 via the collimator lens 106, is reflected by the translationally moving reference mirror 108, and returns along the reference arm 103 towards the coupler 104. The optical paths 103a along the reference arm 103 and 105a along the probe arm 105 are configured to have equivalent optical path lengths toward the focal plane 154 that illuminates the sample being scanned or other object of interest. Based on the detected interference between the returned reference beam light and the returned OCT probe beam light when recombined at the coupler 104, the depth of any structure in the sample to which the probe beam light has been backscattered, reflected, or otherwise returned can be determined by outputting the detected interference signal 146 to the image processor 148.

[0098] In some embodiments, interference between the return reference beam and the return OCT probe beam light occurring along the output arm 107 is measured using a suitable spectrometer 136, such as the one shown in Figure 1, to determine the depth of the scanned cross-sectional image. Other embodiments of the OCT system 100 may use other techniques to measure the interference and generate an output signal 146.

[0099] In some embodiments of the OCT system 100, one or more or all of the optical paths 101a, 103a, 105a, 107a include one or more sections through which an outward or inward (relative to the coupler 104) OCT beam following the optical fiber travels in free space, comprising a suitable single-mode optical fiber and / or an outward or inward (relative to the coupler 104) OCT beam following the optical fiber travels.

[0100] In some embodiments of the disclosed technology, the optical path lengths of the reference beam and the probe beam are the same, but the dispersion characteristics of the optical fibers through which each beam travels are configured to be different in order to improve the removal of complex conjugate images from the OCT image output and to improve the quality of the OCT scan image and the speed at which the complex conjugate-resolved OCT scan image is acquired.

[0101] In some embodiments, the term OCT scanning is used herein to refer to B-scan and stereoscopic scanning images of a tissue region (also referred herein to as a tissue sample) 116 generated using a spectral-region SD-OCT scanner system 100.

[0102] In the schematic example of spectral region OCT shown in Figure 1, a broadband light source 102 generates an OCT probe beam that illuminates a region of tissue 116 that is scanned by the OCT probe beam over the range of near-infrared wavelengths.

[0103] The spectrometer 136 shown in Figure 1 includes a collimating lens 138 through which the reflected light passes through a grating 140 to generate a spectrally dependent interference pattern. The interference pattern is focused onto a line camera 144 via an objective lens 142, and the image signal representing the interference pattern is sent from the output 146 to a suitable image processing system 148. However, in an alternative embodiment, another suitable type of interference detector in the output arm 107 may be used.

[0104] In the embodiment of the SD-OCT system 100 shown in Figure 1, the spectrometer 136 measures the spectral interference of the returned OCT light beam by measuring the intensity modulation of the returned light as a function of frequency. The rate of change of intensity over different frequencies indicates the location of different reflective layers within the sample.

[0105] The OCT probe beam travels from the coupler 104 along the OCT probe branch 105 of the coupler 104, following the optical path 105a, and then enters the OCT scanner 164. An exemplary OCT scanner 164 shown in Figure 1 includes a collimating lens 110 and a scanning mirror assembly 310 (for example, shown in Figures 3A and 5 below) which includes a scanning mirror 112 having a reflective surface 334 (for example, see Figure 3A or Figure 5) that deflects the OCT scanning beam from the scanner 164 through the objective lens 114 toward a focal plane 154 in the scanning region 116. The scanning mirror assembly 310 includes a mirror positioning system which includes a secondary light source 158 that is reflected toward the sample region 116 being scanned by the scanning mirror 112 of the scanning mirror assembly. The scanning mirror assembly includes a mirror positioning system 156 which includes a light source 158 for detecting the mirror position and a mirror position detector (PSD) 160. The OCT scanner 164 also includes an objective lens 114 that focuses the OCT scanning beam onto a focal plane 154 within the region of the tissue or sample 116 being scanned.

[0106] The scanning mirror 112 may include a micro-electromechanical system (MEMS) scanning mirror that is angularly moved by a mirror moving unit (not shown in Figure 1). The movement of the scanning mirror 112 moves the OCT probe beam across the sample being scanned or other object of interest, and the resulting interference pattern is used to generate an OCT B scanning image from the system output 156.

[0107] The movement of the mirror movement unit is performed under the control of the controller 162. The controller 162 may be located within the scanning mirror assembly, which includes the scanning mirror 112, or it may be located separately from it.

[0108] The mirror position system 156 shown in Figure 1 includes an optical angular displacement mirror position measuring system 156. This system provides feedback on the mirror position to the controller and, in some embodiments, enables closed-loop control of the MEMS-based scanning mirror position in some embodiments.

[0109] When the OCT scanner 164 is in use, the scanning mirror 112 is moved by a mirror movement mechanism under the control of the controller 162 to guide the OCT beam along the scanning path. After reflection by the mirror 112, the OCT probe beam passes through a telecentric objective lens 114 that focuses the OCT probe beam to different positions within the focal plane 154 in the sample tissue 116 being scanned. As schematically shown in Figure 1, the focal plane 154 is shown as being in the conceptual xy plane, and depth information is supplied orthogonally along the z axis.

[0110] The telecentric objective lens 114, through which the probe beam passes to reach the sample 116 and through which the return probe beam light also passes, is shown in Figure 1 with three exemplary emerging telecentric beams that focus at different positions within the focal plane 154 in the xy plane, as shown in Figure 1. Each of the exemplary emerging telecentric beams results from a different position on the scanning mirror assembly 112; in other words, Figure 1 schematically shows only three sequential telecentric beam positions as an example. This is to schematically illustrate how the telecentric OCT scan or probe beam is moved to illuminate different regions as the B scan or stereoscopic scan progresses.

[0111] The scanning area includes a sample of tissue 116. In Figure 1, this includes tissue from an eye 116, which may be an in vivo or in vitro tissue sample. In other uses of the OCT scanner system, where OCT scanning images may be useful for visualizing internal structures at various depths within tissue, other types of human or animal tissue can be scanned in vivo or in vitro.

[0112] For example, as shown in Figure 1, the eye 116 is schematically shown and comprises a pupil 118 surrounded by the iris 120, with the posterior chamber 122 and zonal fibers 124 located behind it, and the lens 126 and cornea 128 anterior to it. Figure 1 also presents the anterior chamber 130 of the eye, as well as the ciliary muscle 132 and ligaments 134, all of which can be shown as internal structures in a tomographic image scanned using an OCT system such as OCT system 100 and presented on a display 152.

[0113] The likelihood of a successful outcome from surgical procedures performed on tissues such as the human eye or the eye of another organism, where access is extremely limited, can be improved by using OCT. In some embodiments, the OCT system 100 may be used to create images based on two-dimensional or three-dimensional scanning of the area of ​​the eye 116 being operated on, which can be presented to the surgeon in real time. This allows for a better understanding of the depth of any procedure being performed as the surgery is being carried out. Providing this depth information of the area to be surgically treated in real time can help the surgeon avoid making incisions that are too deep (which may unnecessarily damage the underlying tissue) or too shallow (which may result in an unsuccessful surgery and / or prolonged healing of the surgical tissue).

[0114] As schematically shown in Figure 1, the interference signal output 146 of the spectrometer 136 of the OCT system 100 is post-processed by the image processor 148. For example, the signal output 136 may be image-processed using a Fourier transform or other suitable signal transform for the OCT scan. This can first generate a distorted OCT scan image, and then undergo additional image processing to correct the distortion of the OCT image before the OCT scan image 150 is output to a suitable display 152. Some embodiments of the OCT scanner system 100 may also use image processing to remove complex conjugate artifacts and improve the depth range of the resulting image.

[0115] The display 152 may be part of the apparatus hosting the SD-OCT system 100 that performs image processing, or it may be a separate apparatus. In some exemplary embodiments of the disclosed technology, a series of OCT scan images 148 are generated using an OCT probe light beam quickly enough to supply a live stream video containing OCT scan images 150 onto the display 152. In some embodiments, the display 152 may be a near-eye display. In some embodiments, the display 152 may be a large display system comprising multiple displays for presenting information to both the surgeon and / or others in the operating room. The display 152 may be integrated into the SD-OCT system 100 or it may be external to it.

[0116] One or more of the components shown in Figure 1 that form the OCT scanning system 100 may be housed separately from the optical system that forms the OCT scanner device 164. By separating the OCT scanner optical system, the OCT scanner 164 can have a more compact form factor. A more compact OCT scanner 164 can be better positioned closer to the sample area being scanned.

[0117] In some embodiments, the OCT scanner system 100 includes an OCT scanner 164 provided as an adapter for a microscope, for example, an OCT scanner adapter 206 for a microscope 200 schematically shown in Figures 2A and 2B. In some embodiments, the microscope 200 includes a surgical microscope suitable for use during surgical procedures. In some embodiments, the housing 202 of the microscope 200 has a lower carriage configured to accept one or more microscope accessories, thereby allowing the OCT scanner adapter 206 to be mounted on the lower carriage of the microscope housing. In this case, the OCT scanner adapter optical system objective lens 114 can also function as a microscope objective lens 210 (see also Figures 3A, 3B, and 4 of the drawings).

[0118] Example of a microscope system with an OCT scanner adapter Figures 2A and 2B show schematic front and back perspective views of an OCT scanner adapter 206 for a microscope, in other words, an OCT scanner microscope accessory 206, according to several embodiments of the disclosed technology. The term OCT scanner adapter, as used herein, refers to an OCT scanner adapter microscope accessory. In some embodiments of the disclosed technology, references to an OCT scanner adapter may also refer to an apparatus including an integrated OCT scanner adapter.

[0119] Figures 2A and 2B show how the OCT scanner adapter 206 in Figures 3A, 3B, and 4 may be mounted on the lower carriage of the microscope 200. For example, the microscope accessory of the OCT scanner adapter 206 can be retrofitted to the microscope 200 by removing any existing microscope accessories from mounting points located on the lower carriage of the microscope and using these microscope mounting points to mount the OCT adapter 206 to the lower carriage of the microscope 200 instead. Once properly secured in place, the form factor of the OCT scanner adapter aligns the objective lens 210 with at least one of the optical channels of the microscope optics, e.g., the rear channel or the channel used by the microscope camera. In some embodiments, the lower carriage of the OCT adapter may also provide mounting points for additional accessories.

[0120] In some embodiments, the OCT scanner adapter 206 has a vertically compact form factor so as not to add excessive height h2 to the height h1 of the microscope to which it is mounted when in use. Reducing the additional vertical height h1 of the OCT scanner adapter 206 improves the ease of access to the scanning area in use of the scanner when generating cross-sectional images of the scanning area 116 while the microscope is being used simultaneously. The OCT scanner adapter 206 is also laterally compact. This means that when mounted on the microscope 200, it does not excessively obstruct surgical access to the area of ​​tissue being scanned, allowing for simultaneous surgical procedures.

[0121] In the following description, height is referred to in the context that the OCT scanner adapter 206 is used to scan the tissue sample 116 from a position above the tissue sample, such as when the OCT scanner adapter 206 is mounted on the lower carriage of the surgical microscope 200.

[0122] Some embodiments of the OCT scanner 206 described herein maintain a similarly compact form factor and may be used in other contexts. Furthermore, in some embodiments, the OCT scanner 206 may be integrated into another device, such as a microscope 200. In some embodiments, the OCT scanner 206 may be distributed as an optional accessory for such devices, so that it may be distributed and sold independently of the microscope which may be attached later for use. Thus, unless the context clearly prohibits it, references to height may apply equally to other dimensional directions of the OCT scanner that are substantially or nearly orthogonal to the plane of any device to which the OCT objective lens and OCT scanner are mounted, and the orientation of the OCT scanner and microscope stack may also differ depending on the patient orientation and one or more of the configuration of the microscope optics and the position of the eyepieces.

[0123] In other words, references to height in the overall context of “height” are based solely on the assumed orientation of the OCT scanner and microscope for a supine patient when surgery is being performed on the patient. While the patient is supine, the surgeon can access the area to be operated on beneath one embodiment of the OCT scanner adapter 206 according to the disclosed technology, and at the same time, can physically access the eyepiece of the microscope 200 to which the OCT scanner 206 is mounted. This geometric configuration can vary in some embodiments depending on the configuration of the microscope optics and / or the orientation of the patient and / or the position of the area to be operated on. Thus, in the following description, references to the height of the microscope and OCT scanner adapter 206 and / or the combined stack height may also refer to other dimensions of the microscope and OCT scanner adapter 206 that act as constraints on the form factor of the OCT scanner, which will be apparent to those skilled in the art.

[0124] Returning to Figures 2A and 2B, the microscope optics housed in the microscope housing 202 form an optical channel that provides a view of the area below the objective lens 210 of the OCT scanner adapter 206. In some embodiments, the objective lens 210 realized by the OCT scanner adapter 206 for microscope 200 includes the objective lens 114 of the OCT scanner system 100 schematically shown in Figure 1. Thus, references to the objective lens 210 in this description may refer to the objective lens 114 of the OCT system 100, including different types of OCT scanners 164, unless the context explicitly limits the reference to the use of an OCT scanner as an adapter or accessory for a microscope.

[0125] In an exemplary embodiment of the OCT scanner adapter 206 shown in Figure 2A, the OCT scanning optical design has a compact form factor, adding a minimum additional height h2 to the height h1 of the microscope optical system housing 202.

[0126] Figures 2A and 2B also show microscope handles 204a,b which help position the microscope 200 above the area to be scanned (and viewed). The OCT scanner adapter 206 includes a housing 208 fixed to the lower carriage of the microscope 200 as shown. However, as described above, in some embodiments the OCT scanner adapter 206 may have different configurations and / or orientations when in use. Such different configurations and / or orientations of the OCT scanner adapter 206 in use can also implement the compact principle of the OCT scanner design disclosed herein.

[0127] Figure 2B shows a different rear view of the OCT scanner adapter 206 shown in Figure 2A. The rear view shows a data and / or power port 212, for example, an RSJ45 Ethernet port or a USB port, and an optical port 214. Port 212 supplies power to the OCT scanner adapter 206 and, in some embodiments, may include a power over Ethernet port.

[0128] In some embodiments, the OCT scanning light is returned from the OCT scanner adapter 206 to the interferometry components of the OCT scanning system 100 via the optical port 214, as shown in Figure 1.

[0129] For example, in the embodiment shown in Figure 1, the OCT light returning from the sample 116 returns via the objective lenses 210 and 114 and is output along the optical fiber 308a via the optical port 214. Thus, the optical fiber 308a, the optical path through the mirror lens assembly, and other optical components of the OCT scanner adapter 306 located along the optical path followed by the OCT scanning beam toward the sample being scanned form part of the probe arm 105 of the FD-OCT system 100.

[0130] The OCT light is emitted to illuminate the scanned sample tissue 116, then reflected, backscattered, or otherwise returned. The returned OCT light then passes through the coupler 104 and returns, where it interferes with the light returned from the reference arm 103. The returned OCT and reference beam then propagate along the output arm 107 to the spectrometer 136, which outputs an OCT and reference beam light interference signal 136 for image processing to generate OCT imaging data 146 presented on the display 152.

[0131] For example, in some embodiments of the disclosed technology, such as those shown in Figures 1, 2A, and 2B, the return OCT light is exported from the OCT scanner adapter 206 to the coupler 104 via the optical port 214, and through there it is passed to the spectrometer 136 of the spectral OCT system 100.

[0132] The OCT scanner housing 208, including the objective lens 210, adds a height h2 to the height h1 of the microscope 200 in the embodiments shown in Figures 2A and 2B. The additional stack height H2 introduced by attaching the OCT scanner adapter 206 to the microscope housing 202 is minimized by using the optical design of the OCT scanner optical components within the OCT scanner adapter 206 according to embodiments of the disclosed technology.

[0133] For example, several embodiments of the optical component design of the OCT scanner adapter 206 may have the optical design schematically shown in Figures 3A, 3B, 4, 5A, and 5B. This optical design raises the OCT beam emerging from the scanning mirror assembly 310 by a minimum amount from the plane of the objective lenses 114, 210 before the OCT appears through the objective lenses 114, 120. This allows the additional stack height h2 of the OCT scanner adapter to be less than 40 mm, and in some embodiments, the additional stack height h2 is 36 mm or less.

[0134] Figures 2A and 2B are not to scale, and the x, y, and z axes shown in the figures are schematic and merely illustrative of general front and rear perspective views. As shown in Figures 2A and 2B, the microscope housing body stack height is h1 and is aligned with the Z axis, while the microscope housing base and OCT scanner adapter 206 are mainly aligned with the XY horizontal plane. The OCT scanner system stack height h2 mounted below the carriage is also aligned with the Z axis. As a result, the total stack height h3 of the microscope body housing the microscope optics combined with the OCT scanner mounted below the carriage is determined by h1 and h2. Preferably, the combined height h3, h1 + h2 = h3, is short enough to allow the microscope to be positioned to allow manipulation by a user performing surgery on or through the area including the focal plane of the microscope objective lens 210 through which the OCT beam emanating from the microscope passes. The OCT optical design, for example in some embodiments, allows for the minimization of h2 to 36 mm while still maintaining a suitable output beam diameter of 10.6 mm and having a stack height of 36 mm or less.

[0135] Therefore, by using the optical design for the scanning mirror assembly optical system according to the embodiments of the disclosed technology, the combined stack height h3 = h1 + h2 can be made much shorter than was possible with previous optical design configurations.

[0136] By reducing the stack height as much as possible, the microscope can be better positioned for surgery. For example, it can be positioned far enough away from the focused tissue sample to allow the user access to the tissue sample under surgery, but close enough to fit a typical human physical form factor. In other words, the OCT adapter height h2 is preferably reduced as much as possible to allow conventional operation of the microscope by a user who is also performing surgery, while the microscope is optically focused on the focal plane on the tissue sample using the microscope objective lens 210 of the OCT scanner adapter 206 from which the OCT probe beam is emitted onto the tissue sample.

[0137] Some embodiments of the OCT scanner adapter 206 microscope accessory shown in Figures 2A and 2B include a scanning mirror assembly 310 (described in more detail below) having a compact optical design that allows the h2 to be minimized to 36 mm or less.

[0138] For example, in some embodiments, as will be described later with reference to Figures 3A, 3B, and 4, the OCT scanner adapter 206 includes an ultra-compact large numerical aperture microelectromechanical system (MEMS) based two-dimensional (2D) scanning mirror assembly 310, which uses a position-sensing detector 160 and a point light source 158 to determine the position of the reflective mirror surface 334 in its optical design.

[0139] Some embodiments of OCT scanner assemblies using the PSD160 can support very high scanning rates, e.g., more than 36,000 A scans per second, where an A scan is a depth scan at a given point in the tissue. Each B scan is formed from multiple adjacent A scans, and the A scans can be used to generate an image with depth information about the scanned area in the form of slices through the sample being scanned, showing the structure at different depths along the slice. In other words, the B scan provides information about the structure in the z-direction or depth direction along a single linear cross section of the tissue sample, e.g., a linear scan along a line definable by xy coordinates as schematically shown in Figure 1. Some embodiments of the OCT assembly enable the generation of very high-resolution images, e.g., 400 B scans per second in real time, across the entire field of view (FoV) being scanned, which may be an area of ​​20 mm × 20 mm or larger. By performing a series of B scans sufficiently quickly and in close proximity across the sample, a three-dimensional stereoscopic scan or composite scan can then be formed from the scanned region and presented on the display 152.

[0140] An embodiment of the scanning mirror assembly, shown as optical block 310 in Figures 3A-3B and 4, and shown in more detail in Figures 5A and 5B, includes various optical components arranged in an optical design configured to reduce the height h2 and lateral footprint of the OCT scanner adapter 206.

[0141] Some embodiments of the optical design of a scanning mirror assembly specify one or both of the minimum and maximum exit beam diameters of one or more optical components. For example, the beam diameter of an OCT beam input via optical fiber 308A preferably exceeds a threshold diameter of 3.1 mm when exiting the collimating lens assembly 516, shown as collimating lens 602 in Figure 6, and the beam diameter from the collimating lens may have an exit pupil diameter of 3.3 mm in some embodiments. Other design constraints may depend on the exit pupil diameter of the OCT beam from the collimating lens. For example, in some embodiments, the collimated OCT beam exits the collimating lens assembly with an exit pupil diameter of at least 3.1 mm, and possibly as large as 3.3 mm, to have a wavefront error of less than (approximately) 1 / 2 wave (rms).

[0142] Another selected output beam diameter is the beam diameter of the OCT beam 312 that outputs from the focusing lens assembly 314 of the OCT scanner adapter 206 and then enters the folding mirror 316. The focusing lens 314 expands the OCT scanning or probe beam diameter to 10.6 mm and sets the resolution for the OCT scanner system based on the OCT system numerical aperture, and ultimately the focal length of the OCT microscope objective lens 210. For the objective lens 210 with a working distance (not focal length) of 175 mm, the lateral resolution is 30 μm, in other words, the resolution is better than 33 line pairs per millimeter. This can be compared to a resolution of 6 microns, 166 line pairs / mm, at the mid-image plane located at the exit of the OCT objective lens assemblies 510, 512.

[0143] In some embodiments, the maximum FoV that a user can set for scanning is a 20mm x 20mm area, using a preferred user interface, for example, a user interface of an apparatus implementing the image processing system 148 shown in Figure 1, which includes or is connected to a display 152. In some embodiments, the user interface is configured to allow the user to adjust the position of the OCT scan FoV within a 25mm box, even if the entire FoV of the OCT scan image remains a 20mm x 20mm area.

[0144] Embodiments of the disclosed technology used in surgical procedures and other applications requiring real-time image processing may utilize a highly dispersed configuration of the OCT system 100 having an OCT scanning adapter 206.

[0145] As used herein, the term "real-time" refers to a small processing delay of, for example, 60 ms or less, and in some embodiments, delays of approximately 30 ms or less are achievable. This design incorporates a high incident angle at the scanning mirror to reduce composite angle coupling when performing 2D scanning of the sample with both high lateral optical resolution and a telecentric image plane.

[0146] The following description of the optical design of the scanning mirror assembly 310 shown in Figures 3A, 3B, 4, and 5A incorporates a high incident angle at the scanning mirror reflective surface 334 to reduce composite angle coupling when performing a 2D scan of a sample, enabling the OCT scan to be performed in both high lateral optical resolution and telecentric image plane. Each OCT scan includes a number of one-dimensional scans, A scans, which provide depth information at points within the region being scanned (e.g., of a sample). Several A scans are stacked together to create a two-dimensional image, referred to herein as B scans. B scans provide slices through the scanning region, showing depth information along the path of the A scans. Multiple B scans traversing the scanning region can provide a three-dimensional stereoscopic scan of the scanning region.

[0147] The scanning mirror assembly 310 includes a movable reflective surface 334 equipped with a micro-electromechanical system having a suitable large numerical aperture. The term “large numerical aperture” here refers to the effective aperture diameter of the reflective surface 334, preferably larger than about 4 mm in diameter. The term “effective aperture diameter” means the range of angles that can be imaged through the aperture without obstruction from supports, clips, or other forms of retaining elements. A larger effective aperture diameter of the scanning mirror reflective surface 334 results in a slower scanning rate because the probe beam covers a larger diameter. While MEMS mirrors with an effective aperture diameter of about 7 mm are already known in the art, even with optical feedback, these known MEMS mirrors with large effective aperture diameters cannot scan at speeds acceptable for real-time imaging applications such as those required for OCT during optical surgery. In some embodiments, the scanning mirror has an effective aperture diameter of 5 mm. In some embodiments, a 4.2 mm effective aperture diameter scanning mirror assembly is used, enabling scanning to be performed at speeds fast enough for the SD-OCT system shown in Figure 1 to be used for real-time surgical applications.

[0148] In OCT, axial and transverse characteristics are separated. Transverse resolution is determined by the objective lens and focusing medium in front of the sample. The axial characteristics of interferometry are defined by the coherence characteristics of the OCT scanning light source and how the return OCT signal is sampled by the detector after it has been returned from the sample. OCT axial resolution depends on the spectral bandwidth and center wavelength of the OCT scanning light source. Axial imaging depth defines the axial range covered by the B scan. It is also defined by the maximum fringe frequency that can be detected as the maximum frequency of the interference spectrum, which decodes the maximum depth scanned.

[0149] A scan is an amplitude depth scan along a one-dimensional axis, usually referred to as the z-axis, through the sample, while B scans are two-dimensional transverse scans across the sample formed by a series of A scans. In other words, for each sample point, the spectrally dependent interference fringe pattern generated by back reflections from the OCT interferometer's reference mirror and back reflections from the sample is recorded as an A scan. Multiple A scans are performed to generate other scans, such as B scans, which allow for the generation of a complete depth profile of the sample reflectivity at the beam position.

[0150] In some embodiments, the aperture diameter is 4.2 mm or larger.

[0151] In some embodiments, the OCT scanner adapter 206 includes a high-speed OCT MEMS-based mirror scanning assembly 310 that uses a position sensing detector system 160 to implement control loop feedback for controlling the positioning of the OCT beam during scanning. The control loop feedback has a technical advantage in that it enables the OCT scanner to generate more B scans per second of the object of interest being scanned. In other words, the control feedback loop implemented in some embodiments of the disclosed technology enables the suppression of ringing and resonant behaviors caused by step changes in the drive voltage at the ends of the scan line.

[0152] Example of OCT microscope adapter design Figure 3A schematically shows an exemplary embodiment of the MEMS microscope OCT scanner adapter 206 according to the disclosed technology, which is suitable for mounting on the lower carriage of the microscope 200 shown in Figures 2A and 2B, as it consists of optical components that are designed to optimally reduce the lateral and vertical footprint while maintaining optical quality characteristics suitable for OCT applications.

[0153] In Figure 3A, an illustrated exemplary embodiment of the OCT scanner adapter 206 comprises several components housed within or mounted on an adapter housing 208. The adapter housing 208 includes data / power ports 212, such as an Ethernet Power over Ethernet port or a high-speed USB port.

[0154] Furthermore, an optical port 214 is provided for inputting and outputting OCT scanning light to the OCT scanner adapter 206. The optical fiber 308a connected to the optical port 214 supplies OCT light from the coupler 104 shown in the OCT scanning system 100 of Figure 1 to the scanning mirror assembly optical block 310 shown in Figure 3A via the optical fiber connector 308. The return OCT light returns along the coupler 104 shown in Figure 1 via the optical fiber 308a. Thus, the optical fiber 308a is part of the optical path 105a shown in the OCT scanning system 100 of Figure 1, through which OCT probe light illuminates the sample to be scanned, and through which OCT light returned from the sample is output toward the coupler 104 of the OCT scanning system 100 shown in Figure 1. The optical fiber 308a has a suitable numerical aperture, preferably 0.14, to allow OCT light in the near-infrared region to propagate along it in single mode.

[0155] The OCT light from the OCT light source 102 follows optical path 101a along the illumination arm 101 to the coupler 104, and then takes optical path 105a along the probe arm 105 in Figure 1, which is partly formed by the optical fiber 308a. The OCT light following the optical fiber 308a is injected into the scanning mirror assembly optical block 310 via the OCT data connection fiber connector 308, and then follows the OCT arm 518 of the MEMS scanning mirror assembly 310 (see Figure 5A).

[0156] In some embodiments, the optical fiber connector 308 into which the OCT light is input to the MEMS mirror block 310 is a fiber connector relative to an angle-polished connector.

[0157] The optical block housing the MEMS scanning mirror assembly 310 also houses the optical components of an optical angular displacement mirror position measuring system 156 for the scanning mirror assembly, shown in Figure 1 as a mirror position measuring system 156. A controller 162 (see Figure 1, not shown in Figure 3A) is used to adjust the reflective surface 334 of the scanning mirror 112 shown in Figure 1 using the mirror movement mechanism (not shown) of the MEMS scanning mirror assembly 310. The controller 164 may be implemented within the OCT scanner adapter 206 or may be remotely located, in which case the control signal may be transmitted to the mirror movement unit in the MEMS scanning mirror assembly 310 via the data port 212 of the OCT scanner adapter 206.

[0158] In some embodiments, the same mirror reflective surface 334 in the scanning mirror assembly housed within the optical block 310 reflects both the input OCT beam and the mirror positioning reference beam from a different light source (see Figure 5A below for more details). However, as will be apparent to those skilled in the art, in other embodiments, it is possible to use separate mirrors mounted on the same tilt axis, provided that this is done in a manner that does not adversely affect the stack height h2 of the OCT scanner adapter 206.

[0159] The OCT light, which travels along the optical path 105a and is received via the OCT data connection fiber 308, is reflected by an optical surface of the reflective surface 334 that is different from the optical surface on which the light from the light source of the angular displacement mirror measurement system 156 is reflected.

[0160] The reflected OCT beam then follows an optical path through the OCT scanner adapter 206, from which it emerges via the microscope objective lens 210 to probe a tissue sample of interest, such as in vivo ocular tissue schematically shown in Figure 1. Other types of tissue samples of interest may include tissue samples for fields such as ophthalmology and dermatology, dentistry, angiography, and cardiology, as well as other tissue samples for the diagnosis of diseases, including cancer.

[0161] OCT light reflected, backscattered, or otherwise returned from structures within the tissue sample then returns through the scanning mirror assembly of the optical block 310 and follows the return path 105a along the optical fiber 308a. The returned OCT light is then emitted from the OCT scanner adapter 206 via the optical port 214 and supplied to the OCT system 100, where it is combined with and interferes with the light returned from the reference arm 103 at the coupler 104. The resulting interference pattern is detected by a spectrometer 136 in the OCT system 100 in Figure 1, which generates image data, and the image data can then be image-processed to obtain a tomographic image showing scanned structures within the tissue located within the scanning FoV.

[0162] In an exemplary embodiment of the OCT adapter 206 shown in Figure 3A, the OCT probe beam 312 is output from an optical block housing a MEMS OCT scanning mirror assembly 310 and travels toward a beam splitter 318 toward a folding mirror 316 that lifts the OCT beam a minimum amount from its optical plane toward the beam splitter 318. The beam splitter 318 reflects the incident OCT beam toward the objective lens assembly 210 of the OCT scanner adapter 206, which also functions as the objective lens of the microscope optics housed in the microscope 200 when the OCT scanner adapter 206 is mounted on the microscope 200. The OCT probe beam emerges from the objective lens 210 as a telecentric beam focused on a focal plane 154 in the tissue being scanned, in the xy plane schematically shown in Figure 1. The resulting reflected OCT light can be used to generate an OCT A scan that provides depth information in the z direction, orthogonal to the focal plane 154, in other words, as shown in Figure 1. The movement of the reflective mirror surface 334 shifts the position of the telecentric beam across the focal plane 154 within the scanned region 116, enabling the generation of an OCT B scan image.

[0163] In Figure 3A, the OCT scanner adapter 206 is configured so that the objective lens 210 can be used as an objective lens by the microscope optical system and the OCT scanner system 100. A light-shielding gasket 320 is provided around the aperture formed in the OCT scanner adapter 206, through which the OCT objective lens 210 is aligned with and extends the optical channel formed by the microscope optical system of the microscope 200.

[0164] The configuration of the folding mirror 316, beam splitter 318, and objective lens assembly 210 of the OCT scanner adapter 206 is collectively designed so that the OCT beam is lifted only a small amount from the plane it follows through the scanning mirror assembly so that it can exit through the objective lens 210. The amount of lift required is influenced by the inclination angles of the beam splitter and folding mirror, as well as the beam incidence geometry. Thus, the additional height h2 that the OCT scanner adapter 206 adds to the height of the microscope is also minimized by using this optical design. For example, in some embodiments, the OCT scanner adapter housing 302 adds 40 mm or less to the overall height h1 of the microscope housing 202. In some embodiments, the additional height h2 is 36 mm or less. This can be achieved with a lift of 27 mm or about 27 mm by using suitable inclination angles for the beam splitter and folding mirror in some embodiments.

[0165] In some embodiments, as shown in the exemplary embodiment of Figure 3A, the OCT probe beam 312 exits an optical block housing a scanning mirror assembly, travels through free space, and first proceeds to a focusing lens assembly 314, which allows the focal plane of the scanned image to be adjusted. This adjusts the focus of the scan at different depths. The focusing lens assembly 314 is driven by a motor 326, which further includes a movement limiter or stopper 324. In some embodiments, the focusing mechanism provided by the adapter's focusing lens assembly 314 is adjustable to control the OCT focal plane within a range of ±30 mm, thereby allowing a range of depths in the sample to be focused for scanning. The OCT focal plane can be adjusted over a range of + / -30 mm and may be optimized for the best SNR during initial image acquisition. This should not be confused with the technique of shifting the focus at an A scan rate, which is used to extend the depth of focus in the sample. The focusing lens assembly 314 moves more slowly than required for A-scan sampling and does not adjust without user intervention unless the system detects a large movement of the sample.

[0166] In some embodiments, as shown in Figure 3A, the OCT scanner adapter 206 is attached to the microscope 200 using a fixture, for example, a screw, the screw being provided in recesses of mounts 328a and 328b and extending from mounts 328a, 328b into the lower carriage of the microscope 200, to corresponding receptacle openings or holes, preferably screw holes, in the lower carriage of the microscope 200, so as to fixate the OCT scanner adapter 206 to the microscope. In some embodiments where the OCT scanner adapter 206 functions as a microscope accessory, the OCT scanner adapter 206 may also include receptacle openings or holes at positions on its base corresponding to the positions of receptacle openings or holes in the lower carriage of the microscope 200. Different types of microscope accessories that are otherwise attached to the lower carriage of the microscope 200 can be attached to the lower carriage of the OCT adapter instead by having the same or similar receptacle positions within the base of the OCT scanner adapter microscope accessory 206 as the receptacle positions in the lower carriage of the microscope. In other words, in some embodiments, the OCT scanner adapter 206 is configured to be mounted on the lower carriage of a microscope as a microscope optical system accessory. Some embodiments of the OCT scanner adapter microscope accessory 206 allow the OCT scanner adapter accessory 206 to have another microscope accessory mounted on the base of the OCT scanner adapter.

[0167] Figure 3B shows an alternative diagram of the OCT scanner adapter 206 in Figure 3A. However, in Figure 3B, the position of the light source or emitter 158 of the mirror positioning light beam 400, shown in Figure 4, which illuminates the scanning mirror, is more visible, as is the position of the position sensing detector (PSD) 160 of the optical angular displacement measurement system 156 within the optical block 310.

[0168] Furthermore, Figure 3B schematically shows an exemplary incidence angle θ of the mirror positioning illumination beam 400 shown in Figure 4 on the reflective surface 334 of the MEMS scanning mirror, which, after reflection, forms a mirror positioning reference beam that travels toward the PSD160.

[0169] It should be understood that the incident angles and positions of the beam paths shown in the drawings are for illustrative purposes only and are not to scale.

[0170] The MEMS scanning mirror assembly is designed such that the illumination mirror positioning light beam 400, shown in Figure 4, is reflected by the scanning mirror's reflective surface 334 at different optical surfaces to form a reference beam 402 that passes along the positioning reference arm of the OCT scanning mirror assembly 310 from the optical surface where the incident OCT scanning or probe beam 312 is reflected, as shown in Figures 4 and 5A. The scanning mirror assembly is also configured such that the return positioning light is reflected by the mirror at a different optical surface, which is different from the optical surface where the incident mirror positioning beam is reflected, and which is different from the optical surface where the incident mirror positioning beam is reflected, resulting in minimal interference with any of the light sources of the OCT beam, the incident mirror positioning beam, or the mirror positioning beam.

[0171] Figure 4 of the attached drawings schematically shows an enlarged view of the OCT scanner adapter 206 in Figures 3A and 3B. In Figure 4, the mirror position illumination beam 400 (shown as dashed and dotted lines) from the point light source 158 is incident on the reflective surface 334 of the OCT scanning mirror 500 shown in Figure 5A at an incident angle of interest (AOI) indicated by θ. The mirror position reflected beam 402 (shown as a dashed line in Figure 4) is reflected toward the PSD 160, where it is detected. For clarity, the reflected light from the incident beam at the PSD 160 is not shown in Figure 4.

[0172] The OCT scanner optical components shown in Figures 3A to 4 are arranged so that the OCT light appearing from the optical surface of the scanning mirror assembly is lifted slightly from that optical surface by the folding mirror 316 toward the beam splitter 318. The beam splitter 318 allows the OCT probe beam to be transmitted through the microscope optics and returned to the microscope optics, while reflecting the OCT probe beam to the same focal plane 154 as the microscope light. By optimally positioning the beam splitter and folding mirror relative to the objective lens 210, it is possible to reduce the height that the OCT probe beam must be lifted by the folding mirror before it is reflected by the beam splitter 318 and exits through the objective lens 210.

[0173] In some embodiments, the folded mirror elevates the OCT beam by 27 mm from the optical surface of the scanning mirror assembly.

[0174] Example of optical design for scanning mirror assembly Figure 5A of the attached drawings schematically shows an example of an optical design for a two-dimensional (2D) scanning mirror assembly, such as a 2D scanning mirror assembly housed in the optical block 310 shown in Figures 3A, 3B, and 4.

[0175] The optical design of the 2D scanning mirror assembly is suitable for use with other types of OCT scanners, such as the OCT scanner 164 and OCT scanner adapter 206 shown in Figure 1. The scanning mirror assembly 310 shown in Figure 5A has an optical design that can be used for non-OCT applications that use scanning light requiring mirror positioning.

[0176] In other words, the optical design of the 2D scanning mirror assembly in Figure 5A is not limited in all its embodiments to OCT applications or devices such as those shown in Figures 1 to 4 of the accompanying drawings. It can be usefully implemented in any other type of optical scanning device where a compact lateral optical surface is beneficial.

[0177] Some exemplary embodiments of the micro-electromechanical system (MEMS) two-dimensional scanning mirror assembly 310 shown in Figure 5A have an optical design comprising a movable MEMS scanning mirror having a reflective surface 334, a connector 308 to a point source for a scanning light beam, and, for example, an optical fiber 308a connected via the optical fiber connector 308 as shown, where the end of the optical fiber 308a (see Figure 5b) functions as a point source for the light beam.

[0178] The scanning mirror assembly optics also includes a collimating lens assembly 516 for light introduced via connector 308. The collimating lens assembly 516 is configured to output light from a point source with an output beam diameter exceeding a threshold output beam diameter toward a reflective surface suitable for the desired scanning application. After being reflected by the reflective surface 334 of the scanning mirror 112, the scanning light beam passes through the objective lens assemblies 510, 512 and exits the scanning mirror assembly.

[0179] The reflective surface 334 is configured to reflect the incident collimated light beam to form a scanning beam, for example, an OCT probe beam if the point source realizes OCT light, and the OCT light, as a telecentric beam 312, exits the mirror assembly via the objective lens 510 and the field lens 512 (collectively referred to as the objective lens assembly 510, 512) toward the telecentric image plane 154. The optical design of the components within the scanning mirror assembly is configured to ensure that the scanning beam can perform scanning with a resolution better than the resolution threshold.

[0180] The optical system of the scanning mirror assembly is configured to achieve a total track length L of the path from the point source, for example, from the end face of an optical fiber or fiber ferrule (see also Figure 5B), to the telecentric image plane (700) of less than approximately 40 mm, which helps to keep the lateral dimension X of the scanning mirror assembly small enough to allow the OCT scanner housing 308 to be below the desired lateral footprint in its design. For example, as shown in Figure 5, the width X of the scanning mirror assembly is preferably less than 41 mm, and may be 40.6 mm or less in some embodiments, for example. The optical design is also configured to keep the depth Y as small as possible, as shown in Figure 5A, and may be 35 mm or less, for example, and may be as short as 34.5 mm or less in some optical designs.

[0181] Therefore, in some embodiments, the total track length L is kept as short as possible, allowing the optical design layout to minimize the lateral footprint X and depth footprint Y as much as possible, and as a result, the scanner housing with the scanning mirror assembly 310 can have a similarly small footprint.

[0182] By keeping the lateral footprint X as small as possible, lateral access to the area being scanned is improved, which is particularly beneficial when the scanning mirror assembly 310 is a scanning mirror assembly for the OCT scanner adapter 206, which is a surgical microscope accessory, as this can improve access to the area being operated on while the microscope to which the scanning mirror assembly is attached is in use.

[0183] In some embodiments of the scanning mirror assembly, the threshold for the exit beam diameter from the collimating lens 516 is at least 3 mm, preferably at least 3.1 mm. By having an exit beam diameter of at least 3.1 mm, the scanner benefits from better lateral resolution than that enabled by a smaller exit beam diameter.

[0184] In some embodiments of the scanning mirror assembly, the threshold for telecentric beam resolution at the telecentric image plane 700 is better than 6 microns. In other words, the scanned image can resolve features of the scanned sample smaller than 6 microns.

[0185] In some embodiments, the scanning mirror 112 may be moved by, for example, a controller 162. In some embodiments, the scanning mirror assembly may be configured to move about its optical axis and to scan over a range of + / - 5 degrees.

[0186] In some embodiments of the scanning mirror assembly, both the numerical aperture of the optical fiber and the focal length of the collimating lens determine a preferred threshold of at least 3.1 mm for the exit beam diameter of the collimated beam from the collimating lens in order to achieve the resolution designed at the focal plane. The combination of the focal length of the scanning mirror objective lens and the focal length of the scanning mirror field lens from which the probe beam exits the mirror assembly determines the total track length L, which is preferably less than or near 40 mm.

[0187] In some embodiments, for example, when the scanning mirror assembly is used for OCT purposes, the optical fiber has a numerical aperture of 0.14. The optical fiber supplying light to the scanning mirror assembly by acting as a point source may have a different preferred numerical aperture value that enables supplying sufficient light to the scanning mirror assembly for other use cases along the single-mode optical fiber 308a in other embodiments of the scanning mirror assembly.

[0188] In some embodiments of the scanning mirror assembly, the objective lens 510 comprises an F2.7 biconvex doublet lens, and the field lens 512 comprises an F19 positive / negative meniscus doublet field lens.

[0189] In some embodiments of the scanning mirror assembly, the optical path difference (OPD) of the telecentric probe beam output by the scanning mirror assembly has a radius of curvature greater than 100 mm.

[0190] In some embodiments of the scanning mirror assembly, the telecentric beam is more telecentric than an incident angle of 0.03 degrees in the telecentric image plane.

[0191] In some embodiments of the MEMS scanning mirror assembly, the reflective surface 334 of the MEMS scanning mirror includes a large-diameter gold-clad silicon mirror bonded to the underlying mechanical structure.

[0192] Embodiments of the scanning mirror assembly 310 design schematically shown in Figure 5A can be implemented as an optical block within an OCT scanning system, such as the OCT scanning system 100 shown in Figure 1. For example, in some embodiments, the scanning mirror assembly is implemented as an optical block having the X, Y footprint shown in Figure 5A within a compact OCT scanner adapter 206 for a microscope, such as an optical block housing the scanning mirror assembly 310 shown in Figures 3A, 3B, and 4.

[0193] However, as described above, the scanning mirror assembly 310 shown in Figures 5A and 5B has an optical design that can be used in a variety of different usage scenarios in other types of scanner systems. In some embodiments, the mirror assembly shown in Figures 5A and 5B is realized as a scanning mirror assembly for an OCT device, such as those shown in Figures 3A to 3B, to receive light fed in by the optical fiber 308a. In other embodiments, a different point source may be used instead of the optical fiber 308a, which functions as a point source for the OCT light beam, as shown in Figures 3A, 3B, 4, 5A, and 5B.

[0194] In some embodiments, the mirror assembly 310 may be located within an OCT scanner adapter 206 used as an OCT scanning accessory for a microscope 200. In some embodiments, the microscope may be a surgical microscope, and the scanning mirror assembly 310 may be used to generate OCT scans of the tissue sample being operated on at a speed high enough to allow live OCT tomography of the tissue sample area to be generated while the surgical procedure is in progress.

[0195] In some embodiments, the SD-OCT scanning system shown in Figure 1 includes an OCT scanner adapter 206 comprising scanning mirror assemblies 112,310 having an optical design as shown in Figures 5A and 5B and described herein.

[0196] In some embodiments, the scanning mirror assembly 310 is configured such that the OCT light returned from the sample along the OCT probe arm 105 has a lateral optical resolution of 6 μm or more, in other words, a resolution better than 166 line pairs per mm.

[0197] In some embodiments, the scanning mirror assembly 310 comprises a MEMS 2D scanning mirror assembly including at least a movable MEMS scanning mirror having a reflective surface 334, an optical fiber 308a connected via an optical fiber connector 308 and configured to function as a point source for an OCT beam illuminating the reflective surface 334, and a collimating lens assembly 516 configured to output OCT light from the point source toward the reflective surface 334 with an output beam diameter of at least 3.1 mm. The reflective surface 334 is configured to reflect both an incident collimated OCT light beam for forming an OCT probe beam and a mirror positioning reference beam. The OCT probe emits the mirror assembly as a telecentric beam toward the telecentric image plane with a resolution of at most 6 microns. The optical system of the scanning mirror assembly 310 is configured to achieve a total track length L from a) the end face of the fiber ferrule providing the point source inserted into the optical fiber connector, to b) in some embodiments less than 40 mm, preferably less than 36 mm, to the telecentric image plane. In some embodiments, the objective lens assemblies 510, 512 are located within the probe arm of the scanning mirror assembly to focus the telecentric OCT beam through the OCT scanner (microscope) lenses 114, 210.

[0198] The scanning mirror assembly 310 has an optical design that includes a reflective surface 334 of a MEMS mirror configured such that the incident mirror positioning beam is reflected by an optical surface different from the optical surface on which the incident OCT scanning beam is reflected. In this way, the scanning mirror assembly can also be used with a mirror positioning system, such as the angle-tilting mirror positioning system schematically shown in Figure 1 of the drawings.

[0199] As described above, some embodiments of the MEMS-based scanning mirror assemblies shown in Figures 5A and 5B and described herein are implemented in an OCT scanner 206 as shown in Figures 3A, 3B, and 4, as part of an SD-OCT scanning system shown in Figure 1. Accordingly, some embodiments of the disclosed technology include an OCT scanner system 100 comprising an OCT scanner 206 including a microelectromechanical system (MEMS) two-dimensional scanning mirror assembly 310 having a compact optical design according to the disclosed technology.

[0200] In some embodiments of the MEMS scanning mirror assembly 310, the scanning mirror 112 is mounted on a lower mechanical structure or support 500 that provides a mirror movement mechanism that allows the mirror surface 334 to pivot around its optical axis under the control of a controller 162, as shown in Figure 5A.

[0201] In some embodiments, the reflective surface 334 of the MEMS scanning mirror assembly includes a large-diameter gold-clad silicon mirror bonded to the underlying mechanical structure 500.

[0202] The angular displacement measurement system 156 shown in Figure 1 is implemented in the embodiment of the MEMS mirror assembly in Figure 5A by a light source 158, which is a preferred point light source, for example, a laser diode 502. The point light source generates a light beam, referred to herein as the mirror positioning light beam 400 (shown as a dashed line in Figure 5A), which passes through the collimating lens 503 so that the collimated mirror positioning beam 400 is incident on the scanning mirror surface 334 at an incident angle θ.

[0203] The angular displacement measurement system 156 is used to determine the angular position of the MEMS scanning mirror assembly 310 relative to the incident mirror positioning beam 400, thereby determining the mirror position of the incident light beam when performing a scan and adjusting it as the scan progresses. OCT scanning (e.g., B-scanning or stereoscopic scanning) is performed by moving the mirror using the controller 164 according to arbitrary scanning parameters for a particular scanning configuration (these may be input by the user and / or automatically determined for a particular type of scan in some embodiments).

[0204] The position of the movable MEMS mirror surface 334 can be controlled in some embodiments using a suitable angular position controller (not shown in Figure 5A) that uses closed-loop control based on feedback from a position sensing detector 160 that detects the reflected mirror positioning beam 402.

[0205] In some embodiments, the scanning mirror assembly 310 described above with reference to Figures 3A, 3B, 4, 5A, and 5B includes a position sensing detector 160 configured to transmit feedback mirror position data to a controller 162 configured to control the position of the MEMS scanning mirror surface when scanning is performed. However, in some embodiments of the compact OCT scanning mirror assembly 310 of the drawings, the controller is housed remotely. For example, in some embodiments, it may be housed elsewhere within the OCT scanner adapter 206. Alternatively, in some embodiments, it may be housed together with other system components of the OCT scanner system 100, or it may be hosted on a different platform having a user interface that allows input of scanning parameters. Control signals may be transmitted from the remote controller 162 via a suitable data connection, such as a data port, such as 212, in some embodiments.

[0206] In some embodiments, the mirror positioning light source illuminates the reflective surface of the mirror assembly for the optical mirror position feedback channel at an incident angle θ greater than 62 degrees, preferably 67.5 degrees, from the normal to the plane of the reflective mirror surface 334.

[0207] In some embodiments, the OCT light source illuminates the reflective surface of the mirror assembly of the OCT light channel at an incident angle θ of less than 28 degrees, preferably 22.5 degrees, from the normal to the plane of the reflective mirror surface 334.

[0208] In some embodiments, the minimum usable aperture on the reflective mirror surface is at least 4 mm, which is particularly useful when the mirror assembly is incorporated into an OCT scanner device, such as the compact OCT scanner 206 microscope accessory used for surgical applications.

[0209] In some embodiments of the disclosed technology, the OCT apparatus may use closed-loop feedback to control the scanning mirror position. The use of closed-loop feedback may be useful in embodiments requiring high scanning rates, such as when a live video or other form of OCT scanning image sequence is required. The use of closed-loop feedback allows the mirror to be moved fast enough and accurately to achieve high scanning rates and / or high scanning resolution (in other words, high OCT image B-scan or stereoscopic scanning resolution), thus supporting low-latency, high-speed OCT scanning for time-sensitive applications, such as when OCT scanning is implemented to guide surgical procedures. However, in some embodiments, open-loop control may be provided.

[0210] The disclosed technology attempts to address at least some of the design constraints that exist when designing OCT systems for surgical microscopes. For example, one design constraint is that smaller diameter scanning mirror surfaces are better suited to achieving higher scanning rates. Numerical aperture is related to resolution. The effective aperture diameter, i.e., the mirror diameter, is related to the scanning size in that the underlying mechanical structure of the MEMS is the same, and therefore a smaller diameter mirror, such as 2 mm in diameter, can tilt further before hitting the MEMS base (up to + / - 7 degrees), while a larger diameter mirror, such as 7.5 mm in diameter, can tilt only + / - 1.5 degrees before hitting the base. This means that a larger area can be scanned using a smaller diameter mirror, but this comes at the expense of resolution.

[0211] In some embodiments, the threshold for the exit beam diameter of the OCT light beam is based on the numerical aperture of the optical fiber and the focal length of the collimating lens assembly.

[0212] In some embodiments, the two-dimensional scanning mirror assembly is configured to reflect a mirror positioning light beam (400) incident on a reflective surface (334) in a first optical plane toward a position sensing detector (160) configured to generate information about the tilt angle of the scanning mirror reflective surface (334).

[0213] In some embodiments of the optical angular displacement measurement system 156 of the scanning mirror assembly 310 shown in Figure 5, mirror positioning light from a light source 158 is first collimated by a preferred collimating lens assembly 503 to form a collimated illumination light beam 400 that is incident on the reflective mirror surface 334. The collimated illumination light beam 400 (circularly represented by short dashed / dashed lines in Figures 3B, 4, and 5A) is then incident on the reflective MEMS mirror surface 334 at AOI = θ and reflected to form a mirror position reference beam 402 (shown by longer dashed / dashed lines in Figures 3B, 4, and 5A), which moves along the mirror position reference arm 501 of the scanning mirror assembly, through the PSD lens assembly 504, and in some embodiments, through an optional attenuation filter 506, toward the PSD 160.

[0214] However, the mirror positioning beam 400 may be reflected by the PSD160 toward the reflective surface 334 of the MEMS mirror or otherwise returned (the reflected beam is not shown in Figure 5A). This is undesirable because such reflected light may contaminate the illumination positioning beam and / or the input OCT light beam. Other issues with stray light reflectivity in the mirror position detector system include the detection of an incorrect spot position when stray light is present on the PSD160, and the potential for changes in diode behavior when reflected light is incident on the diode cavity, which can cause intensity fluctuations in the position detector beam that the PSD detects as a change in position.

[0215] To prevent the return reflecting element of the positioning beam from being reflected by the MEMS mirror assembly 310, some embodiments of the disclosed technology include additional components such as optical traps. The optical traps are appropriately configured and positioned to reduce the re-incidentation of any reflected mirror positioning reference beam light into the emitter for the mirror positioning beam and / or contamination of the return probe beam 312 before it reaches the interferometer.

[0216] As described above, some embodiments of the MEMS-based scanning mirror assemblies shown in Figures 5A and 5B have a reflective surface designed so that OCT light input via the OCT optical coupler 308 is reflected from a mirror positioning reference beam 402 and from another region of the MEMS mirror surface 334 to which the OCT scanning or probe beam is reflected from a different optical surface.

[0217] After reflection, the OCT scan or probe beam reflected by the MEMS mirror surface 334 of the scanning mirror assembly 310 passes along the optical path through the OCT objective lens 510 and the OCT field lens assembly 512, which outputs the OCT beam as a telecentric beam into free space toward the folding mirror 316. As shown in the embodiments of Figures 3A and 3B and Figure 4, the beam passes through the focusing lens assembly 314 before being incident on the folding mirror 318, which lifts the beam away from the optical surface of the scanning mirror assembly. In some embodiments, this allows the OCT focal plane to be focused within a range of + / - 30 mm, in other words, a range of different depths can be focused into the scanning area. However, the focusing lens optics may be omitted in some embodiments of the OCT scanner.

[0218] The folding mirror 316 lifts the OCT scanning (or probe) beam from the plane of its optical path through the scanning mirror assembly by reflecting the incident OCT scanning or probe beam toward the beam splitter 318. The beam splitter reflects the OCT scanning or probe beam from the microscope objective lens 210 of the OCT scanner adapter 206 toward the focal plane 154 for scanning the tissue or similar object of interest, which may be an in vivo or in vitro tissue sample. The beam splitter 318 also allows the scanned OCT illuminated area to be viewed through the microscope optics housed within the microscope 200.

[0219] In some embodiments, as shown in Figures 3A and 3B, the OCT probe beam 312 is input to the optical block by traveling along the optical path 105a in the optical fiber 308a and is incident on the scanning mirror optical block 310 via the OCT data connection fiber input 308. The OCT scanning or probe beam 520 then passes toward the scanning mirror reflective surface 334 via the collimating lens 516. The mirror surface 334 reflects the OCT beam from the optical block, including the scanning mirror assembly 310, via the probe arm 508, at which point the OCT beam folds back toward the mirror 316 in free space.

[0220] As shown in the embodiments of the OCT adapter in Figures 3A, 3B, and 4, the OCT scan or probe beam 312 is focused by passing through a focusing lens assembly 314 before reaching the folding mirror 316. The focusing lens assembly is driven by a motor 336 that adjusts the position of the focusing optical system to allow a range of depths of focus to be achieved when performing a scan. In some embodiments, the focal range can vary from + / - 30 mm.

[0221] The returned OCT light is reflected via the MEMS scanning mirror surface 334, along the OCT arm 518 of the scanning mirror assembly 310, toward the coupler of the OCT system 100 shown in Figure 1.

[0222] In the scanning mirror assembly 310, the input OCT light beam enters from the end face 532 of the optical fiber 308a via the optical fiber connector 308, passes through the optical fiber ferrule 530 (see also Figure 5B), and then through the OCT collimating lens 516 towards the scanning mirror assembly. The track length, in other words, the measurable physical distance of the path from the end face 532 to the surface of the scanning mirror, is shown as L1 in Figures 5A and 5B.

[0223] Figure 5A also shows the track length L2 from the scanning mirror surface to the telecentric image plane 700. The total track lengths L=L1 and L2 are preferably less than or equal to the track length design threshold of 40 mm.

[0224] Figure 5B is an enlarged view of Figure 5A, showing more clearly the positions of the optical fiber ferrule 532 and optical fiber end face 530, which cause the optical fiber 308a, acting as a point light source, to incident OCT light onto the mirror scanning system 310. The OCT light travels from the end face 532 of the fiber to the collimating lens 516, and the collimated illumination OCT beam is then incident on the reflective surface 334 of the MEMS scanning mirror, which reflects it toward the OCT probe arm 105 (shown in Figure 1) or 508 shown in Figure 5A.

[0225] For clarification, in the return direction not shown in Figure 5A or Figure 5B, the return OCT light travels in the other direction along the OCT arm 518 (see also the description in Figure 6), through the collimating lens 516, then along the optical fiber 308a via the OCT data connection fiber 308, and then out of the OCT scanner adapter 206 via the optical port 214.

[0226] In some embodiments, the OCT scanner is implemented using off-the-shelf (OTS) MEMS (micro-electromechanical systems), where the MEMS scanning mirror reflective surface 334 is provided by a large-aperture protective gold-coated silicon mirror bonded to a mechanical structure 500 beneath the optical block 310. The OCT scanner 206 formed by such a design provides a simplified and miniaturized optical system with the same optical performance as much larger galvanometer scanning mirror type systems known in the art for use in intraoperative OCT systems.

[0227] In some embodiments, the optical block design of the OCT MEMS mirror assembly 310 includes a 2D scanning mirror assembly and a complementary optical angular displacement measuring system 156 for measuring the position of the MEMS mirror system.

[0228] A mirror positioning system for measuring the angular displacement of a scanning mirror reflective surface 334 comprises a mirror positioning light source 158 and a position-sensing detector (PSD) 160. The PSD may also include a PSD lens assembly 504 and a light-reducing filter 506, similar to the PSD 160. A suitable example of a PSD detector is the Hamamatsu S5991 4mm × 4mm active-area position-sensing detector.

[0229] In some embodiments, the angular optical displacement measurement system 156 is located within the same optical block as the MEMS scanning mirror assembly 310. In some embodiments, the optical angular displacement measurement system 156 is used to achieve closed-loop control of the MEMS scanning mirror position. Closed-loop control can be achieved by measuring the incident angle θ using the PSD 160 and supplying information indicating the mirror position derived therefrom to the controller, thereby enabling the controller to more accurately control the tilt angle of the scanning mirror reflective surface 334 when scanning is performed.

[0230] This closed-loop feedback can enable very high B-scan rates. For example, using closed-loop control of a 4.2 mm diameter effective aperture mirror 112, it is possible to achieve at least 400 B-scans per second as the maximum scan rate with full-angle deflection relative to the maximum field of view (FoV).

[0231] In embodiments without closed-loop control, i.e., open-loop scanning, a low-pass filter can be used to prevent the MEMS scanning mirror moving device from reaching a natural frequency excitation state where it may resonate due to uncontrolled vibrations (which could damage the MEMS scanning mirror moving device). In embodiments where open-loop scanning is performed, the maximum scanning rate may be about 50 B scans per second, which can be compared to the speed achievable with closed-loop control. In some embodiments with closed-loop control, the scanning rates achievable using exemplary embodiments of the MEMS scanning mirror assembly 310 according to the disclosed technology are about 400 Hz or higher.

[0232] In some embodiments, the optical components of the MEMS scanning mirror assembly 310 are configured to collectively achieve a predetermined system numerical aperture for a desired system optical resolution through the microscope objective lens 210. In other words, in some embodiments, the MEMS scanning mirror system components are appropriately configured to allow the diameter of the collimated OCT beam 312 output along the OCT data connection fiber 308 to match a desired minimum system optical resolution after passing through the microscope objective lens 210.

[0233] In some embodiments, all air-to-glass interfaces within the OCT scanner adapter 206 are designed to be convex in order to minimize back reflection from the OCT beam as it propagates through the optical system.

[0234] Figure 6 shows an exemplary embodiment of an OCT collimator lens 516, also referred to herein as an OCT collimator lens assembly, such as the collimator lens 516 shown on the OCT arm 518 of an optical block including the scanning mirror assembly 310 shown in Figure 5 of the drawings. The OCT collimator lens 516 is provided along the OCT arm 518 of the scanning mirror assembly optical block 310. In Figure 6, OCT light supplied to the collimator lens assembly 602 via the optical fiber ferrule end 532 appears as a collimated OCT output beam 604 having a collimated beam diameter of at least 3.1 mm. The collimated OCT beam then travels toward the scanning mirror reflective surface 334 and is reflected from there. The returned OCT light follows a reverse path through the scanning mirror assembly and is focused toward the end of the optical fiber 308a that collects the returned light via the collimated beam, and then the returned OCT light can propagate toward the coupler 104 of an interferometer system such as the OCT system 100 shown in Figure 1.

[0235] A preferred example of the OCT collimator lens 516 that may be used in some embodiments of the disclosed technology is an F3.2 biconvex doublet lens. Such lenses have a thick crown glass portion that reduces the radius of curvature of the lens surface, thereby improving color performance. In some exemplary embodiments, the collimator lens has a focal length of 10 mm with a depth of focus of 100 microns, enabling good mechanical focus stability. In some embodiments, the OCT collimator lens realizes an output beam having a collimated beam (exit pupil diameter) of 3.1 mm in diameter with <1 / 4 wave (root mean square, rms) wavefront error.

[0236] Figure 7 shows an example of an OCT objective lens assembly 510, 512 in which the OCT beam 312 contains light 312a of a certain range of wavelengths, for example, light of a certain range of wavelengths over the near-infrared portion of the optical spectrum.

[0237] The OCT light is reflected from the reflective surface 334 of the scanning mirror assembly, first focused by the OCT objective lens 510, then by the field lens 512, and subsequently emerges as a telecentric beam 312b. Multiple angle-dependent telecentric beams 312b 1,2,3 However, these beams are focused onto the telecentric image plane 700, as shown in Figure 7, and each beam 312b 1,2,3 This indicates the location where the OCT beam 312b appears at a specific scanning angle; in other words, the telecentric exit beams 312b1, 312b2, and 312b3 are sequential beams generated as the B scan progresses.

[0238] The OCT beam 312 deflected from the mirror surface, in other words, passes through the OCT objective lens assembly 510 (including the field lens 512 in some embodiments), and the light 312b forming the OCT beam 312, schematically shown in Figure 7 as OCT exit beams 312b1, 312b2, and 312b3, can be designed to exit perpendicular to the intermediate image plane at all scanning angles and thus be telecentric.

[0239] In some embodiments, all air-to-glass interfaces, such as 514, are convex to eliminate back-reflection artifacts in the OCT image. Therefore, the OCT objective lens assembly shown in Figure 7 receives the angular input OCT scan or probe beam 312a reflected from the MEMS scanning mirror surface 334, and the telecentric OCT scan or probe beam 312b (or rather, beam 312b) 1,2,3The telecentric OCT scan or probe beam 312b is converted to one of the following, which in some embodiments is then output to free space. In some embodiments, the telecentric OCT scan or probe beam 312b is first focused using a focusing lens assembly 314 before being lifted towards the beam splitter 318 by a folding mirror 316, as shown in Figures 3A and 3B. Alternatively, for example, the telecentric OCT scan or probe beam 312b may pass directly through free space to the folding mirror 316, where it is reflected towards the beam splitter 318.

[0240] The focusing lens assembly 314 functions as the optical interface for the telecentric OCT beam 312b to the microscope objective lens 210. The scanning mirror assembly can be used without the focusing lens assembly 314 in some embodiments, but this requires that the sample be positioned on the intermediate image plane 700, which is focused when the telecentric OCT beam 312b emerges from the scanning mirror assembly. Therefore, to use the OCT scanner 206 without the focusing lens assembly, the sample must be positioned on the intermediate image plane 700 in some way. For example, as shown in the exemplary embodiments of the OCT scanner in Figures 3A, 3B, and 4, the lens is required to optically couple to the microscope objective lens 210, or alternatively, the objective lens 210 would require a much shorter focal length. Such short focal lengths are not useful for surgical applications. However, in some embodiments of the disclosed technology, the OCT scanner may omit the focusing lens assembly 314 when used for a different type of application. For example, an OCT scanner 206 used for imaging eyes, especially animal eyes, may not require a focusing lens 314.

[0241] In some exemplary embodiments of the OCT scanner adapter 206 used in surgical microscopes, a focusing lens assembly 314 collimates and magnifies the incoming telecentric OCT beam 312b to a suitable back focal length, so that it has a collimated beam diameter of 10.6 mm at the exit. As the OCT beam 312 exits the focusing assembly, it is collimated and therefore focuses on the focal plane of the microscope objective lens 310, as with the microscope optics.

[0242] Alternatively, the target distance is effectively adjusted by adjusting the position of the focusing lens assembly 314 relative to the intermediate image plane. This allows the focal position of the microscope objective lens 310 to be changed as appropriate for OCT scanning, while the focal position remains fixed for the microscope optical system.

[0243] An advantage of having a focusing lens assembly 314 in some embodiments of the OCT scanner, such as those shown in the exemplary embodiments in Figures 3A, 3B, and 4, is that if the surgeon moves their eyeballs during a surgical procedure, the OCT scanning system can keep the OCT focused on a designated anatomical feature using appropriate automatic focusing techniques known in the art.

[0244] Another advantage of the embodiment of the OCT scanner 206 including the focusing lens assembly 314 is that it can be used in some situations even if the microscope optics are improperly set up by the user of the microscope 200, for example, a surgeon or assistant. For example, if the microscope is parfocal, in other words, if the microscope eyepiece is set to infinity for a user with corrected vision via contact lenses or glasses, the microscope optics will focus on the focal plane of the microscope objective lens. If the microscope eyepiece is not set to accommodate the refractive error of the microscope user's vision, some users may adjust or compensate for their own refractive error by moving the entire microscope using handles 204a,b, as shown in Figures 2A and 2B, for example. However, this movement of the microscope optics results in the scanned tissue sample or other scanned object of interest (e.g., an eye under surgery) no longer being positioned on the actual focal plane of the microscope objective lens 210 realized by the OCT scanner system 206. In other words, if the microscope is used improperly, the focus of the OCT beam 312 may need to be adjusted accordingly to compensate using a focusing lens assembly such as the focusing lens assembly 314.

[0245] In some embodiments, the OCT objective lens 510 shown in Figure 7 is an F2.7 biconvex doublet lens. The objective lens 510 is coupled with an F19 positive / negative meniscus doublet field lens 512 to direct the scanned collimated OCT beam 312, reflected from the surface 334 of the MEMS scanning mirror, to the intermediate telecentric image plane shown in Figure 7. The OCT return beam passes through the OCT field lens, then through the OCT objective lens, then is reflected again via the reflective surface 334 of the MEMS mirror, and enters the interferometer assembly (see SD-OCT system 100 in Figure 1, not shown in Figure 5A) via the OCT collimated lens 516 (see also Figure 5A) along the OCT output arm 518.

[0246] In some embodiments, as shown in the exemplary embodiments of Figures 5A and 7, all air-to-glass interfaces, such as the surface 514 of the objective lens assembly 510 for the outward OCT beam 312 and the return OCT beam (not shown), and the collimating lens 516, are convex to eliminate back reflection artifacts in the OCT image.

[0247] In some embodiments, the total track length L in the optical block of the scanning mirror assembly is the sum of the length L1 from the end face 530 of the optical fiber 308a in the optical fiber ferrule 532 to the reflective surface 334 of the scanning mirror, and the track length L2 from the surface 334 to the telecentric image plane 700, as shown in Figure 5A. The total track length L = L1 + L2 is preferably less than 40 mm.

[0248] In some embodiments, the optical path difference (OPD) in the scanned sample has an OPD curvature greater than 100 mm.

[0249] In some embodiments, the OCT scan or probe beam is telecentric better than an incident angle of 0.03 degrees.

[0250] In some embodiments, a focusing system 314 is provided to adjust the OCT beam 312 so that the OCT focal plane can be controlled within a range of ±30 mm and aligned with the microscope optical channel focal plane.

[0251] In some embodiments, the MEMS OCT scanner has a lateral XY profile where X is less than 42 mm and Y is less than 35 mm, as schematically shown in Figure 5A, so that the OCT scanner system housing can be laterally fitted into the lateral housing profile of the microscope optical system carrier footprint. This is advantageous as it reduces obstruction in the sterile field for surgical applications. In some embodiments of the optical block that implements the scanning mirror assembly 310, the dimensions of the optical block are a width X of about 40.6 mm or equal to it and a depth Y of about 34.5 mm or equal to it, and a track length L of about 40 mm or less.

[0252] In some embodiments, the scanning mirror assembly further comprises an optical angle displacement measuring system 156 for determining the inclination angle of the reflective surface with respect to incident light, the system comprising at least a point light source, a collimator lens assembly for collimating light from the point light source to form a collimated mirror position measuring light beam incident on the reflective surface, and a position sensing detector, wherein the reflective surface is configured to reflect the incident collimated light beam at a first optical surface to form a reflected position measuring light beam that travels toward the position sensing detector.

[0253] In some embodiments of the scanning mirror assembly 310 described above with reference to Figures 5A and 5B of the drawings, closed-loop control of the position of the reflective surface of the MEMS mirror is achieved by a position-sensing detector configured to supply angular displacement measurement information to a controller configured to control the inclination angle of the reflective mirror surface with respect to the irradiated light beam. In some embodiments, closed-loop control uses a PID feedback loop to adjust the drive voltage to the MEMS based on the position and to attenuate ringing artifacts caused by rapid directional changes.

[0254] Advantageously, in some embodiments, the scanning mirror assembly includes a scanning mirror assembly 310 within the OCT scanning device 206, where the input beam includes an OCT probe beam 312 that is reflected toward the sample or similar object of interest 116 through optical components along the OCT probe beam arm of the scanning mirror assembly. The scanning mirror assembly 310 is configured to output the OCT probe beam 312 toward the focal plane 154 of the sample as a telecentric OCT probe beam, and the optical path length of the OCT probe beam from the light source 102 to the sample focal image plane 154 is configured to be equal to the optical path length of a reference OCT beam from the same OCT light source 112 along the reference arm 103 of an interferometer OCT system 100 connected for 2D scanning of the sample region 116.

[0255] In some embodiments, the MEMS scanning mirror assembly 310 disclosed herein is provided as an optical block 310 within an OCT scanner adapter 206 for a surgical microscope 200 that forms part of a connected OCT system 100. Such an OCT scanner adapter 206 preferably has at least a lateral footprint X within or equal to the footprint of the surgical microscope housing, and preferably also has a length or depth footprint within the footprint of the microscope. The OCT system 100 outputs an interference signal containing OCT scanning data 146 to an image processor 148 of the OCT system 100. The image processor 148 can then process the interference signal 146 and perform signal transformations, such as a Fourier transform, which enables the display of an OCT image showing internal scanning structures within a scanning area on a display 152. This image can be generated in real time to guide a surgeon and / or, in some embodiments, to guide other parties on one or more preferred displays 152.

[0256] In some embodiments of the OCT scanner adapter 206, the OCT scanner adapter 206 is configured to be fixed to the lower carriage of the housing of the microscope optics of a surgical microscope, and the OCT scanner adapter 206 adds less than 40 mm, preferably less than 36 mm, to the stack height of the surgical microscope.

[0257] In some embodiments of the OCT scanner adapter 206, the OCT scanner adapter 206 is configured to be fixed to the lower carriage of the microscope optical system housing, and the objective lenses 114, 210 of the OCT scanner adapter 206 are aligned with the optical channels of the microscope optical system when the lateral footprint of the housing 208 of the OCT scanner adapter 206 is located within the lateral footprint of the housing 202 of the surgical microscope 200.

[0258] In this way, a surgical microscope 200, such as the one shown in Figures 2A and 2B, comprising a microscope optical system, a housing 202 for housing the microscope optical system, and an OCT scanner adapter 206, can be provided according to the disclosed technology, the OCT scanner adapter 206 including, for example, a scanning mirror assembly according to the disclosed technology, as shown as an example in Figures 5A and 3B. The OCT scanner adapter 206 may be configured to output image data that will later be input to an image processor of an OCT system, such as the OCT system shown in Figure 1.

[0259] The image processor 148 shown in the SD-OCT system 100 of FIG. 1 is configured to receive OCT scan image data output via the spectrometer 136. Any suitable device may be used as a platform for the image processor 148. In some embodiments, the device may comprise a general computer system in which image processing algorithms are executed using one or more processors or processing circuits. See, for example, FIG. 12, described later below. The image data output by the spectrometer 136 is at least Fourier-transformed by the image processing system 148, and the output of the image processing system 148 may be further processed to correct the distortion of the Fourier-transformed OCT scan image, as schematically shown in FIG. 1, for example.

[0260] FIGS. 8A and 8B show OCT images that can be generated, for example, by using an embodiment of an OCT scanner attached as an accessory to a surgical microscope 200 as schematically shown in FIGS. 2A and 2B, using an embodiment of the SD-OCT system 100 of FIG. 1. In some embodiments, the OCT scanner adapter 206 of FIG. 2 may include an OCT scanner adapter that includes optical components described in more detail in FIGS. 3A, 3B, 4, 5A, 5B, 6, and 7.

[0261] FIG. 8A shows an example of a typical OCT image of a contact lens and a layered tape phantom. The complex conjugate (CC) image artifact appears as a very blurred stripe in the OCT scan image due to the dispersion effect. FIG. 8B shows the result of processing the image using an image processor as shown as the image processor 148 of FIG. 1, which is configured to implement an exemplary embodiment of a computer-implemented image processing method 900 for removing complex conjugate image data from image data in real time using the dispersion according to the disclosed technique.

[0262] The OCT image of FIG. 8B has the complex conjugate image artifact removed. The OCT image shown in FIG. 8B is derived, for example, by processing the OCT image data output from the OCT scanner adapter 206 as shown in FIG. 2A using an embodiment of an iterative image processing algorithm to remove the complex conjugate artifact according to the disclosed technique, and the resulting image of FIG. 8B exhibits a similar image quality as that shown in FIG. 8A but with the complex conjugate image artifact removed.

[0263] The disclosed embodiment of the image processing algorithm attempts to improve known techniques to prevent complex conjugate artifacts remaining in the OCT scan image generated from the spectral data output by an SC-OCT system as shown in FIG. 1. Only the real part of the spectrum is detected by the spectrometer 136 within the SD-OCT system 100 shown in FIG. 1, and as a result, in order to avoid the complex conjugate mirror term overlapping with the sample structure in the OCT image, unless some CC mirror artifact is removed from the OCT image before it is displayed, only half of the available depth range can be used to generate the OCT scan image of the sample.

[0264] To improve the removal of CC image artifacts from the OCT scan image at a speed that enables the generation of live OCT scan images, an exemplary embodiment of the disclosed technique also includes a computer-implemented method that uses dispersion to remove CC image artifacts from the OCT scan image.

[0265] It is known that the dispersion mismatch between the probe arm 105 and the reference arm 103 in the OCT interferometer system 100 causes a wavelength-dependent phase shift in the spectral interference fringes between the combined light returning from the reference arm 103 and the probe arm 105. Various techniques that use the dispersion mismatch between the probe arm and the reference arm in a spectral domain (SD) OCT system to compensate for this phase shift are also known in the art.

[0266] Some embodiments of the disclosed technology aim to improve upon known technologies by providing algorithms that iteratively suppress complex conjugate artifacts, thereby increasing the imaging range in OCT scans, such as those generated by the SD OCT system 100 in Figure 1. The disclosed embodiments of the algorithm adjust the threshold from which frequency components are removed from each artifact in each iteration, thereby enabling the suppression of more CCR artifacts in each iteration and enabling the generation of cleaner OCT scans more quickly.

[0267] Some embodiments of the algorithms based on the disclosed technology enable numerical processing of real-time OCT image data, such as that output from the spectrometer 136 in Figure 1, to suppress CCR artifacts in the resulting live OCT scan images. Each iteration of the algorithm acting on the OCT scan detects multiple signal frequency components that exceed a frequency detection threshold adjusted for that iteration of the algorithm. In other words, multiple iterations of the algorithm are performed to remove CCR artifacts in the OCT scan data for each OCT A scan, and the frequency detection threshold is adjusted for each iteration of that OCT A scan. This allows for faster acquisition of cleaner and more stable OCT scan images to generate OCT B and C scans, saves more tomography data than algorithms that fix the detection threshold for each scan, and improves the time required to generate each clean OCT scan image. In some embodiments, the computer-implemented image processing method for removing complex conjugate image data from OCT image data can be executed in real time because the algorithm is relatively fast, and B scan images can be generated in less than 30 milliseconds.

[0268] In some embodiments, the image processing acts on a live stream of OCT scan images and is fast enough to reduce the delay in presenting the CCR-cleaned live stream image to less than 60 ms, although in some embodiments it may be as low as 30 ms.

[0269] Figure 9 shows an exemplary embodiment of a computer-implemented image processing method 900 for removing complex conjugate image data from image data including an OCT scan, the method 900 includes at least receiving an image signal including image data including complex conjugate image data in an image processing device 148 (902), performing baseline signal subtraction (906), resampling wavelength data to generate linear wavenumber image data (908, 910), and processing the linear wavenumber image data using an algorithm according to the disclosed technology to generate a complex conjugate-resolved (CCR) image result, in other words, removing complex conjugate artifacts below a threshold level from an OCT scan image. In 912, at least one iteration, preferably two or more iterations, of the image processing algorithm is performed for each OCT scan, and in 914, image data including a complex conjugate-resolved image is generated. The CCR image data may include phase and / or magnitude data, and in some embodiments, logarithmic scaling 916 of the OCT scan image data can be performed to enable a more visually meaningful / impactful representation of the OCT scan over a wider frequency range when the CCR scan image data is output to a suitable display such as the display 150 in Figure 1.

[0270] In some embodiments, Method 900 may be performed in real time, for example, the OCT scan image may be generated in less than 30 milliseconds using some embodiments of the disclosed technology. The calculated image data from the displayed CCR results may, in some embodiments, include size and / or phase data of the CCR result image. In other words, size data is generally used in OCT, but in some embodiments, it is possible to use phase data that is also present in the results from the CCR processing, or to use a combination of the two (size and phase) when generating image data from the CCR results.

[0271] In some embodiments, linear wavenumber image data used to generate complex conjugate resolution results may be generated by performing multiple iterations of the complex conjugate resolution (CCR) image processing algorithm according to the disclosed technique, for example, the CCR algorithm shown in Figure 10 or Figure 11. Figure 11 shows further details of two iterations of the algorithm for simplification, where an actual OCT scan signal (R0) 1102 containing the current signal amplitude over time is input to the image processing device 148.

[0272] To generate a CCR OCT image, in other words, an OCT scan image free from CCR artifacts from an actual OCT scan signal output by, for example, the SD scanning system 100 in Figure 1, some embodiments of the disclosed technology perform an OCT processing procedure having one embodiment of method 900, which includes acquiring an OCT signal, performing signal apodization (optional), performing adaptive DC subtraction to remove a baseline current signal from an acquired OCT scan current signal output by the SD-OCT system 100, resampling wavelength data to be linear in wavenumber, and executing a CCR image processing algorithm 1000 according to the disclosed technology, such as the algorithm 1000 schematically shown in Figures 10, 11A, and 11B.

[0273] Referring briefly to Figure 11A, the image processing device 148 processes the input signal 1102 to correct its variance and applies a suitable transform such as a Fourier transform or Fast Fourier transform, or a similar technique, to generate frequency-amplitude information. Next, by applying a suitable detection threshold to the OCT frequency scan data, it is possible to selectively store only signal frequencies with amplitudes exceeding the threshold, which is schematically shown in Figure 11 by "application of threshold α0max(|r0|)". This cleans up the frequency signal (see 1008 in Figures 10 and 11), allowing for the extraction of complex frequency signal data to generate an OCT scan image for storage in 1014. Next, inverse transform and inverse variance are performed (see 1016, 1018 in Figure 10), which results in a much cleaner signal in 1104 than the original input in 1102.

[0274] The real components of the cleaner signal are subtracted from the starting spectrum at 1020, and then algorithm 1000 is repeated for a second iteration, as shown in Figure 11A.

[0275] Figure 11B shows how the initial threshold can be determined using a histogram of the frequency distribution of the Fourier transform, and the threshold is then dynamically adjusted in each subsequent iteration of the algorithm in the manner shown in Figure 11A.

[0276] Returning to Figure 10, a flowchart is shown illustrating a schematic method for implementing an exemplary embodiment of algorithm 1000. As shown in Figure 10, the computer implementation method is: Applying dispersion correction to the resampled wavelength data of the acquired OCT signal (1002), The signal transformation of a dispersion-corrected signal, for example, calculating the Fast Fourier Transform (FFT) (1004), Calculating the magnitude of the FFT result (1006), (For example, based on an empirically derived formula) calculate the adaptive storage threshold for the current iteration of algorithm 1000 (1008) to determine whether the FFT result should be stored, If it is determined that the result of 1008 exceeds the adaptive memory threshold, the value of the FFT result is stored in 1014 (1010), If the magnitude does not exceed the threshold, set the FFT result to zero (10¹²), Calculating the inverse FFT of the stored values ​​(1016), Applying inverse variance correction (1018), This can be described using pseudocode that includes extracting the real components and subtracting the result from the starting spectrum (1020).

[0277] Some embodiments of algorithm 1000 may use empirically derived formulas or other types of formulas to calculate a variable threshold for storing the FFT result. However, some other embodiments may derive the variable storage threshold differently. For example, in some embodiments, the variable storage threshold may be derived from dynamic image characteristics such as the image intensity distribution or other image characteristics.

[0278] The embodiments shown in the drawings and described herein refer to the Fast Fourier Transform of an input signal from a spectrometer, but it will be apparent to those skilled in the art that other preferred signal transforms may be used instead in other embodiments of the disclosed technology.

[0279] By repeating the above steps of the algorithm multiple times, for example at least two times, so that the algorithm is iterated at least three times in total, it is possible to generate an OCT image in which, in some embodiments, perceptible CC image data may not be present, for example, as shown in Figure 11, a much cleaner signal is shown in 1110 after inverse FT and inverse variance have been applied.

[0280] The algorithm further includes, at 1022, evaluating whether there are complex conjugate image artifacts in the real component of the signal conversion complex-valued image. If not, then another iteration is performed. If there are no conjugate image effects in the signal conversion result image, the algorithm ends at 1024.

[0281] However, optionally, instead of performing another iteration of the algorithm, if there are any remaining iteration residual signals in the last iteration, that is, if there is any residual CC image data, this can be added to the final output signal in some embodiments at 1026.

[0282] In some embodiments, the calculated CCR image can be calculated to provide the size and / or phase data of the CCR result image.

[0283] Method 900 may also include, in some embodiments, performing a logarithmic scaling of the resulting CCR image to assist in visualizing data that may have a range of sizes over several orders of magnitude.

[0284] Some embodiments of the algorithm shown in FIG. 10 include applying dispersion correction (1002), performing a fast Fourier transform (FFT) or similar complex signal conversion on the linear frequency image signal data (1004), calculating the magnitude of the result of performing the FFT on the linear frequency image signal data (1006), calculating a variable threshold for each iteration of the algorithm (1008), setting the FFT result to zero for each FFT result value having a magnitude that does not match the condition for storage based on the threshold for the current iteration (1012), storing the FFT result for each FFT result value having a magnitude that matches the condition for storage based on the threshold for the current iteration (1014), calculating an inverse FFT for all stored FFT results (1016), applying inverse dispersion correction (1018), extracting the real image component and subtracting the result from the starting image spectrum data (1020).

[0285] In some embodiments, the condition for storing the FFT result includes matching or exceeding a calculated adaptive storage threshold, in other words, matching the threshold for storing the FFT result for the current iteration, or exceeding a calculated storage threshold set for that iteration of the algorithm.

[0286] For example, by using an OCT scanning mirror system such as the OCT scanner adapter 206 shown in Figures 2A and 2B, and applying the same algorithm to the image data generated by each A scan produced by the OCT scanner system 100, and then stacking the A scans, in some embodiments it is possible to generate B scan image data that does not contain or contains very little perceptible CC image data. This makes it possible to obtain stereoscopic C scan images that are free from or nearly free from CC image artifacts.

[0287] In some embodiments of Method 900, in 1022, the CCR algorithm is repeated multiple times to extract the real image components until the stored FFT result values ​​include a complex-valued image without significant conjugate image artifacts, and the CCR result of each iteration is subtracted from the starting image spectral data of that iteration.

[0288] In some embodiments of the method 900 using the CCR algorithm 1000, the algorithm includes performing signal apodization 904. Signal apodization can adjust the input OCT signal to have zero values ​​at each end using processing parameters set by the user. This helps reduce edge artifacts that may occur when performing the FFT in a subsequent step.

[0289] In some embodiments, the calculated variable memory threshold for the OCT FFT result is based on an empirically derived formula.

[0290] In some embodiments, either alternatively or in addition, the calculated variable storage threshold for storing the OCT FFT results may include an adaptive storage threshold that is adapted in the first iteration based on dynamic image characteristics such as the intensity distribution or other properties of the current image being processed. For example, in some exemplary embodiments, a histogram can be used to set the initial threshold. This may reduce the need for recalibration of the scanning system.

[0291] In some embodiments of Method 900, the method is implemented in hardware by using, for example, a graphics processing unit capable of processing an image in less than 30 milliseconds.

[0292] In some embodiments, the image data is OCT image data, for example, OCT image data acquired using an OCT scanning mirror adapter for a microscope as shown in Figures 2A and 2B described herein, and the method further includes outputting an OCT image (920) based on the received OCT image data from which the complex conjugate image data has been removed (918). The output OCT image (922) can, in some embodiments, be displayed, ideally without the perceptible complex conjugate image.

[0293] Figures 11A and 11B schematically illustrate an example of the iterative CCR algorithm of Figure 10, where dashed lines indicate zero-frequency positions on the post-FFT graph. Figure 11A shows the real image signal r0, which has been corrected for variance and then Fourier transformed, for example, using the Fast Fourier Transform, in the first iteration of the algorithm. Next, a variable memory threshold a0max(|r0|) in the first iteration of Figure 11A, and a variable memory threshold a0max(|r0|) given by r0>a0 in Figure 11B, described below for the stored result, is applied. Here, one embodiment of threshold calculation is shown, where the threshold changes with each iteration and is based on the proportion of the maximum image value in each iteration. However, other embodiments may use a predetermined threshold or other image characteristics, such as the intensity distribution or other signal characteristics in the current image, to dynamically determine an appropriate threshold. If the results exceed a threshold for storage, the complex conjugate image decomposition data (shown as cumulative complex data in Figures 11A and 11B) is accumulated in a suitable storage medium or memory.

[0294] Otherwise, the CC image data will be discarded.

[0295] Next, an inverse Fourier transform, such as the Fast Fourier Transform, is performed, the inverse variance is applied to the data, and the real components are subtracted from the starting spectrum. The result is a new input signal to algorithm R1, which is then variance-corrected and a Fourier transform is applied. The result is then compared to a storage threshold, which is variable for each iteration of the algorithm in some embodiments. If the result exceeds the threshold, the complex conjugate decomposition data is added to the stored conjugate decomposition data found in the first iteration. Otherwise, the data is not stored. After the comparison, the inverse Fourier transform and inverse variance correction can be applied, and the real components can be subtracted from the starting spectrum of that iteration. The next iteration, shown in Figures 11A and 11B as the second iteration, begins with a new threshold for storing the spectrum, shown as a1max(|r1|) in Figure 11A and as r1>a1 in Figure 11B.

[0296] The embodiment of the algorithm in Figure 10, schematically shown in Figure 11A, differs in Figure 11B. The first iteration of the algorithm according to the embodiment shown in Figure 11B sets a first threshold for storing complex data based on a frequency histogram obtained at 1006 from the Fourier transform of the input signal. Threshold a n And a0 can be obtained, for example, based on the light intensity versus frequency histogram of the scanned image being processed, by the following:

[0297] a n = a0 - n * ( a0 - a N ) / N

number

[0298] Here, a min = Minimum priority threshold a max = Maximum starting threshold a N = Final iteration threshold Q tmin =Minimum Q4 threshold Q tmax = Maximum Q4 threshold Q4 = Upper quartiles That is the case.

[0299] This allows processing parameters to be based on the characteristics of the original image in the first iteration. This enables the application of an optimally selected threshold level before the iterative CCR processing begins. In other words, the optimal threshold for the first iteration is pre-selected based on the optical characteristics of that image. This dynamic adjustment is advantageous because it allows for the automatic taking into account different scanning illumination settings.

[0300] In some embodiments, Method 900 and the algorithm are performed by an image processing unit 148 of an optical coherence tomography (OCT) apparatus configured to perform real-time OCT, such as the spectral domain OCT system 100 shown in Figure 1. In some embodiments, the system 100 may include an illumination arm 101 including at least an optical light source 103, a reference arm 103, an OCT probe arm 105 from which an OCT probe beam is emitted, and a data arm 107 through which the return OCT light passes and is processed by an image processor 148, for example, an image processor 148 configured to perform one embodiment of Method 900 according to the disclosed technology.

[0301] In some embodiments of the OCT apparatus 100, the dispersion between the reference arm 103 and the probe arm 105 is configured to exceed a minimum design threshold for separating the complex conjugate image from the OCT image output for display. The dispersion component can be provided to one or both of the reference arm or the probe arm, but this is less desirable as it may cancel out the difference in dispersion between the reference arm and the probe arm.

[0302] In some embodiments, at least one dispersion component within the reference arm comprises a dispersion optical fiber.

[0303] In some embodiments, at least one dispersion component within a reference arm includes a dispersion glass window. The physical path length of either reference arm is shortened to compensate for the dispersion window, or the physical path length of the opposite OCT probe arm is extended to compensate for the dispersion window.

[0304] In some embodiments, at least one dispersion component within the reference arm comprises one or more dispersion retroreflectors, and the amount of dispersion is determined by the optical path length through the dispersion retroreflectors.

[0305] If the OCT system has at least one dispersive optical component provided on the OCT probe arm (105), this may include a dispersive optical fiber. Alternatively, or in some embodiments, a dispersive dichroic mirror and / or a dispersive OCT objective lens 510 and / or a dispersive OCT field lens 512 can be used to introduce dispersion into the probe arm.

[0306] Figure 12 schematically shows an image processor 148 according to the disclosed technology, which has an input port for receiving or acquiring OCT image data, such as the image data 146 shown in Figure 1, output via the interferometer coupler 104 of the OCT system 100. The image processor 148 shown in Figure 12 comprises an input port 1200 and one or more processors or processing circuits (1202) having a graphics processing unit 1204 for processing input OCT signal data by performing method 900 and / or algorithm 1000. The obtained non-complex conjugate image data is then output via an output port 1208, and the output data 150 can then be displayed on a suitable display device. The image processing unit 148 shown in Figure 12 also comprises a suitable memory 1006 for storing image data.

[0307] In some embodiments, Method 900 can be implemented using a computer program product that includes computer code configured to cause a device, such as the image processing device 148 shown in Figure 12, to perform Method 900 when loaded from memory 1006 and executed on one or more processors or processing circuits 1202, 1205 of the device.

[0308] An example of using bulk glass differential dispersion in an interferometer. Several embodiments of the disclosed technology use bulk glass differential dispersion interferometer designs to support extended depth imaging in optical coherence tomography. These embodiments may be used in conjunction with the calculation methods described above with reference to Figures 8A, 8B, 9, 10, 11A, 11B, 13, and 14 of the accompanying drawings. The interferometer designs disclosed herein may be used in some embodiments in the OCT scanning system 100 of Figure 1. The OCT scanning system of Figure 1 may, in some embodiments, include an OCT scanner adapter 206 for a surgical microscope, which is described by the embodiments disclosed herein and / or incorporates features as illustrated in Figures 2A, 2B, 3A, 3B, 4, 5A, 5B, 6, or 7.

[0309] In optical coherence tomography (OCT), complex conjugate resolution requires that there be a minimum amount of differential variance between the sample path and the reference path of the system interferometer.

[0310] In an OCT system where the light source consists of a broadband, short-coherence-length but spatially coherent superluminescent diode, the dispersion within the system is a result of the color or wavelength-dependent velocity difference of the light passing through the system's optical path, and is called group velocity dispersion or GVD, which is quantitatively defined by RP photonics as the derivative of the inverse group velocity with respect to angular frequency, as expressed by the following equation.

[0311]

number

[0312] Here, c = speed of light in a vacuum λ=wavelength n = refractive index That is the case.

[0313] Group velocity variance (GVD) can also be defined as group delay variance (GDD) per unit length.

[0314] Wavelength dispersion can be calculated from the solid material properties of the optical glass constituting the OCT system using one of the following three industry-standard dispersion formulas.

[0315] Sellmeier distributed formula:

number

[0316] Schott distributed formula:

number

[0317] Conrady distributed formula: nλ = n0 + A / λ + B / (λ^3.5) The specific coefficients in each equation are supplied by the glass manufacturer from measured glass molten material properties data.

[0318] Most transparent materials aim for low quadratic dispersion, resulting in a flat dispersion curve in the NIR spectral range; therefore, the high dispersion required for complex conjugate resolution is the opposite of typical optical designs across the visible spectrum. For CCR candidate materials, the derivative of the dispersion curve in the NIR spectral range should be similar to that of optical glass in the short-wavelength or ultraviolet wavelength range. Such materials are transparent at IR wavelengths and highly dispersed at NIR wavelengths, which means the material is used outside the usual design range; therefore, dispersion data must not be compiled by the glass manufacturer and must be calculated independently.

[0319] The disclosed technology improves the capabilities of the image processing system 148 of the SD-OCT system 100 by using infrared (IR) wavelength filter glass instead of optical design glass (e.g., the lens used in embodiments of the OCT scanner adapter 206 and / or OCT system 100 disclosed herein), thereby better removing complex conjugate artifacts and producing complex conjugate-resolved images with better resolution and an extended depth range.

[0320] Figure 14 of the attached drawings shows an example of a method for determining the required group velocity delay (GVD) for a filter glass material according to the disclosed embodiment using Sellmeier coefficients. A similar method may be used if a different dispersion formula is used in other embodiments to determine the desired GVD.

[0321] In Figure 14, the Sellmeier dispersion equation for the refractive index of the target glass as a function of wavelength is first solved in S1402, and then the coefficient of GVD, i.e., (λ 3 / 2πc 2 (where c = vacuum speed of light) is calculated in S1404, and then the second derivative of refractive index versus wavelength, i.e., ∂ 2 n / ∂λ 2 The GVD is calculated in S1406, and then the GVD coefficient obtained in S1404 is multiplied by the second derivative value obtained in S1406 to determine the GVD of the glass in S1408. Subsequently, the GVD calculations in S1404 to S1408 are repeated in 20 nm wavelength increments over an OCT optical bandwidth that may be centered at 850 nm and have a bandwidth range of 100 nm around that center wavelength in S1410. The average GVD over the bandwidth range covered by S1410 is then determined in S1412, and then the group dispersion delay GDD is determined in S1414 based on the average GVD value and the glass optical path length of the glass in the interferometer system.

[0322] Any suitable apparatus, for example, the apparatus shown in Figure 12 of the attached drawings, may be used to carry out method 1400.

[0323] From the experiment, 31000(fs 2 ) and 46000(fs 2 The empirically determined GDD value between ) was chosen to give the best result for CCR.

[0324] Some embodiments of the disclosed technology replace one of the existing optical components of a path length adjustable OCT reference assembly, shown as reference arm 103 in the OCT system 100 of Figure 1, to provide a retroreflector system as shown in Figure 16 of the drawings (described below).

[0325] The reference assembly within the reference arm 103 comprises a retroreflector having a maximum retroreflector optical path length of 32.4 mm in some embodiments of the disclosed technology. Approximately 38500 (fs 2 Based on the median GDD value of ), dividing by the optical path length of 32.4 mm gives 1190 (fs 2 This means that the target GVD value of the filter glass material ( / mm) is required for retroreflector design using the disclosed technology.

[0326] Using the method 1400 outlined above, an ideal set of parameters for a glass material for OCT light with a central wavelength of 850 nm is obtained, for example, the glass refractive index n at least at 850 nm, and the group refractive index n of the light at 850 nm. g A set of parameters was determined, including GVD and transparency (expressed as % transparency at 850 nm). These were considered suitable for OCT light centered at 850 nm with a bandwidth of approximately 100 nm, which is not the wavelength of light used in some embodiments of the disclosed techniques that use near-infrared spectral light.

[0327] Examples of parameter values ​​for the properties of glass and fiber are shown in Table 1 below.

[0328] [Table 1]

[0329] The values ​​in Table 1 are examples. These represent suitable optical properties for hybrid or high-dispersion fibers that can be used in various exemplary embodiments of an interferometer system where the reference arm optical fiber length is 6 m for a nominal center wavelength of 850 nm.

[0330] The OCT beam spectrum is preferably in the infrared spectrum from about 700 nm to 1000 μm, and in some embodiments, it may be limited to the near-infrared spectrum from 750 nm to 3 μm.

[0331] Here, the group refractive index (ng) is defined as follows, where λ is the wavelength of the OCT light.

[0332] n g =c / v g =n(λ)-λ×∂n(λ) / ∂λ The only glass material possessing sufficient GVD and acceptable light absorption characteristics across the OCT bandwidth with these properties was Schott glass designated IRG27 (see the middle row of the table above). Based on calculations, the GVD of IRG27 glass is 1120.75 (fs 2 Equivalent to ( / mm), and combined with an optical path length of 32.4mm, it is below the target median value but exceeds the minimum allowable GDD value at 36312(fs 2 This yields the total GDD value.

[0333] Figures 15A and 15B schematically show exemplary physical or mechanical designs of retroreflectors, such as retroreflectors made from IRG27 glass, or retroreflectors having the same or similar refractive index, group refractive index, GVD, and equivalent optical properties such as optical clarity.

[0334] Figure 15A shows a side view of a retroreflector having a conical design with three different reflective surfaces S2, as shown in the plan view of Figure 15B. Figure 15A shows an example of the dimensions of the retroreflector reflective surfaces S2 relative to a virtual surface S1 which is the “base” of the cone (see also element 1500 labeled in Figure 16). The angles and dimensions (shown in mm) are examples only, as will be understood by those skilled in the art.

[0335] Figure 16 shows an exemplary embodiment of an automated path length optics-mechanical assembly 1600 comprising an embodiment of a high-dispersion retroreflector 1500 according to the disclosed technology. Several embodiments of the automated path length optics-mechanical assembly 1600 are configured for use within a reference arm 103 of an OCT system, such as the OCT system 100 shown in Figure 1 or any of the embodiments of the OCT system 100 disclosed herein.

[0336] In Figure 16, assembly 1600 includes an adjustable glass retroreflector 1602 containing glass having the properties of, for example, BK7 glass material manufactured by SCHOTT, or any suitable optically equivalent glass (see that parameters such as glass should preferably match those in Table 1 above). A fixed glass retroreflector 1604 containing the same glass material as the adjustable glass retroreflector 1602 is provided at one end of the adjustable portion 1606 of the path length shown in Figure 16. The high-dispersion retroreflector 1500 shown in Figure 2 is fixed. By moving the position of the mount 1608 along track 1606, the optical path length in the reference arm 103 can be adjusted to achieve a desired level of complex conjugate artifact rejection from the signal output by the interferometer for scans performed at greater depths than otherwise possible. CCR rejection can be performed, for example, on the signal 146 output by the spectrometer 136 shown in Figure 1 when the OCT interference pattern signal is processed by the image processor 148. The processing may include a complex conjugate resolution method according to any one of the embodiments disclosed herein, for example, the schematically shown method 1000 which is implemented using an iterative algorithm such as that described above with reference to Figures 9 to 13 of the drawings and / or as shown in Figures 11A and 11B of the drawings.

[0337] In some embodiments, the high-dispersion retroreflector 1500 may comprise a filter glass that is transparent at least in the near-infrared (IR) wavelength and configured to cause differential dispersion of incident broadband low-coherent light at least in the near-infrared (NIR) wavelength.

[0338] In some embodiments, the retroreflector is transparent over the same wavelength range over which differential dispersion occurs, but in other embodiments, it may be transparent over a different wavelength range over which differential dispersion occurs.

[0339] In some embodiments, the median group delay dispersion of the filter glass is 38000 (fs 2 )~40000(fs 2) may be within the range, and the median group dispersion rate of the filter glass is 1100 fs 2 / mm~1280fs 2 The value may be in the range of / mm.

[0340] In some embodiments, the high-dispersion retroreflector 1500 includes a glass having one of the following properties for incident light having a spectrum centered at 850 nm, wherein the glass has a refractive index of 2.5129 for light having a wavelength of 850 nm, a group refractive index of 2.7268 (ng) for light having a wavelength of 850 nm, and 1120.75 fs 2 It exhibits a group velocity delay of 1 / mm and 95.7% transparency to light with a wavelength of 850nm.

[0341] The retroreflector 1500 may have a conical exterior, and the interior of the cone includes at least three specular facets collectively configured to perform retroreflection of incident light.

[0342] In some embodiments of the disclosed technology, a bulk glass differential-dispersion interferometer assembly 1600 is provided for extended depth imaging in optical coherence tomography (OCT). The interferometer assembly 1600 may include an automated path length optics-mechanical assembly comprising a first fixed retroreflector 1604 located at one end of the optical path and a second adjustable retroreflector 1602 located in the same location as a fixed high-dispersion retroreflector 1500 on a mount 1608 configured to move along a track or guide rail 1608. By moving the mount 1608, the retroreflector 1500 is movable, thereby creating an adjustable optical path within the interferometer assembly 1600. In some embodiments, the high-dispersion retroreflector 1500 comprises a filter glass. The filter glass may be transparent at infrared (IR) wavelengths and may be configured to induce differential dispersion at least at near-infrared (NIR) wavelengths between broadband low-coherent incident light, for example, between the returned OCT light and the returned OCT reference light described herein in the OCT system of Figure 1.

[0343] In some embodiments, where the interferometer assembly is located within the probe arm 105 of the OCT scanning system 100, the high-dispersion retroreflector 1500 is configured to induce differential dispersion at near-infrared (NIR) wavelengths between broadband low-coherent incident light returning from the reference arm 103 of the OCT scanning system 100 and broadband low-coherent incident light returning from the probe arm 105. In some embodiments, the OCT scanning system is a spectral-domain OCT system having an interferometer configured to output an OCT scanning interference signal, which is then processed at the complex conjugate resolution of the incident OCT light in a tissue sample, such as the tissue sample 116 shown in Figure 1.

[0344] In some embodiments, the median group delay dispersion of the filter glass material is 38000 (fs 2 )~40000(fs 2 The median group dispersion rate of the filter glass material can have values ​​in the range of ). 2 / mm~1280fs 2 It can have values ​​in the range of / mm.

[0345] In some embodiments of assembly 1600, the high-dispersion retroreflector 1500 has a refractive index of 2.5129 for light with a wavelength of 850 nm, a group refractive index of 2.7268 (ng) for light with a wavelength of 850 nm, and 1120.75 fs for incident light having a spectrum centered at 850 nm. 2 The glass includes a group velocity delay of 1 / mm and a transparency of 95.7% for light with a wavelength of 850nm. For example, the high-dispersion retroreflector may include IRG27 glass, such as that manufactured by Schott_IRG. The fixed retroreflector 1604 and the movable retroreflector 1602 each have a refractive index of 1.5098 for light with a wavelength of 850nm, a group refractive index of 1.5249 (ng) for light with a wavelength of 850nm, and a group refractive index of 40.13 fs for incident light with a spectrum centered at 850nm. 2The glass may have a group velocity delay of 1 / mm and a transparency of 99.8% for light having a wavelength of 850 nm. In some embodiments, the first and second retroreflectors may be made of BK7 glass, such as that manufactured by SCHOTT. In some embodiments of the assembly, the high-dispersion retroreflector 1500 has a conical exterior, and the interior of the cone comprises at least three specular facets collectively configured to perform retroreflection of incident light.

[0346] Some embodiments of assembly 1600 may be used by an optical coherence tomography (OCT) apparatus 100 configured to perform real-time OCT, the apparatus comprising: an illumination arm 101 including at least one optical light source 102 for OCT; a reference arm 103; an OCT probe arm 105 from which an OCT probe beam is emitted; a data arm 107 through which the returned OCT light passes and is processed by an image processor 148; and at least one dispersed retroreflector in the reference arm 103 or the OCT probe arm 105.

[0347] In some embodiments, the variance between the reference arm and the probe arm is variable and set above a minimum threshold for separating the complex conjugate image from the OCT image output for display.

[0348] In some embodiments, the OCT device further comprises at least one additional distributed component provided on either the reference arm or the OCT probe arm.

[0349] In some embodiments, at least one additional distributed component is located within the reference arm and comprises a distributed optical fiber.

[0350] In some embodiments, at least one additional dispersion component is located within the reference arm and includes a dispersion glass window, and the physical path length of the reference arm is configured to compensate for the dispersion window, or the physical path length of the opposite OCT probe arm is extended to compensate for the dispersion window.

[0351] In some embodiments, the OCT apparatus comprises a bulk glass differential-dispersive interferometer assembly 1600 for extended depth imaging in optical coherence tomography (OCT), and the interferometer assembly comprises an automated path length optical mechanical assembly 1600.

[0352] In some embodiments, the OCT device 100 includes an OCT scanner adapter 206 according to any of the embodiments disclosed herein.

[0353] In some embodiments, at least one dispersive optical component is provided within the OCT probe arm (105) and comprises one or more of a dispersive optical fiber, a dispersive dichroic mirror, a dispersive OCT objective lens (510), and a dispersive OCT field lens (512).

[0354] An example of using hybrid fiber-based differential dispersion in an interferometer. Some embodiments of the disclosed technology use hybrid fiber-based differential dispersion in the interferometer instead of, or in addition to, using bulk glass differential dispersion in the interferometer design to support extended depth imaging in optical coherence tomography. These embodiments may be used in conjunction with the calculation methods described above with reference to Figures 8A, 8B, 9, 10, 11A, 11B, 13, and 14 of the accompanying drawings. The interferometer designs disclosed herein may be used in some embodiments in the OCT scanning system 100 of Figure 1. The OCT scanning system of Figure 1 may, in some embodiments, include an OCT scanner adapter 206 for a surgical microscope, incorporating features described by the embodiments disclosed herein and / or as illustrated in Figures 2A, 2B, 3A, 3B, 4, 5A, 5B, 6, or 7.

[0355] As described above, in optical coherence tomography, complex conjugate resolution requires that there be a minimum amount of differential variance between the sample path and the reference path of the system interferometer. Optical coherence tomography (OCT) is an imaging modality that uses the principle of low coherence interferometry to produce a three-dimensional image of a sample. An OCT system such as the system 100 shown in Figure 1 comprises a broadband light source 102 for OCT scanning light, a reference arm 103, a sample optical arm 105, also referred to herein, for example, as a probe or scanning arm, and a detection arm 107 equipped with a spectrometer 136, as shown in the embodiment of Figure 1. Alternatively, in the disclosed embodiment of the OCT system 100 that does not require a spectrometer, a photodiode detector may be used instead.

[0356] The interference patterns of light reflected from the reference arm 103 and the sample arm 105 are measured by the detector 136 and electronically processed using a suitable device such as the image processor 148 shown in Figure 1 to generate a tomographic image showing the relative positions of reflectors or structures causing backscattering of incident OCT light within the sample (see 116 in Figure 1, an example of a reflector or structure where the same is an eye is also shown in Figure 1). Scanning the OCT beam within the probe or sample arm using a scanning mirror assembly such as the scanning mirror assembly 310 disclosed herein allows for the matching of different spatial positions and thus enables the construction of a 3D image of the sample, in other words, a stereoscopic scan can be generated from multiple B scans.

[0357] OCT signal processing requires multiple steps, one of which is the Fourier transform of the detected interference signal. However, since the measured signal is real-valued, performing a Fourier transform yields a complex signal with identical positive and negative frequency components. This mirroring of data is known as complex conjugate artifact and limits the usable imaging range to half of the theoretically possible range. Techniques to remove or suppress conjugate artifacts are known as complex conjugate resolution (CCR) methods and can result in an immediate doubling of the imaging range in OCT.

[0358] Some embodiments of the disclosed technology can be used as bulk filter glass retroreflectors in a reference arm to improve the efficiency of the CCR method disclosed herein. In addition, or instead, in some embodiments, hybrid fibers may be designed to improve the efficiency of CC artifact removal.

[0359] Known techniques require expensive and complex optical components that must be added to the OCT system and may require the acquisition of multiple images before the phase information necessary to remove conjugate images can be generated. This slows down the imaging time, degrades system performance, and makes the system highly susceptible to sample movement, especially when imaging biological subjects.

[0360] Since some embodiments of the OCT system 100 disclosed herein aim to perform B-scanning and preferably stereoscopic scanning in real time while a surgical procedure is being performed, it is advantageous that relatively fast techniques can be used to present OCT images without CCR image artifacts. The removal of CCR artifacts can also enable an increase in the depth resolution (in other words, resolution along the Z-axis) of any resulting OCT B-scanning or stereoscopic image.

[0361] The disclosed embodiments include a method for determining a plurality of single-mode optical fiber types, one or more of which have different fiber core diameters, and the plurality of single-mode fibers collectively correct chromatic dispersion along a predetermined amount to support CCR as part of an OCT interferometer reference assembly.

[0362] In optical coherence tomography (OCT), complex conjugate resolution requires that there be a minimum amount of differential variance between the sample path and the reference path of the system interferometer.

[0363] In an OCT system where the light source consists of a broadband, short-coherence-length but spatially coherent superluminescent diode, the dispersion within the system is a result of the color or wavelength-dependent velocity difference of the light passing through the system's optical path, and is called group velocity dispersion or GVD, which is quantitatively defined by RP photonics as the derivative of the inverse group velocity with respect to angular frequency, as expressed by the following equation.

[0364]

number

[0365] Here, c = the speed of light in a vacuum, λ = wavelength, and n = refractive index.

[0366] Group velocity dispersion (GVD) can also be defined as group delay dispersion (GDD) per unit length. In the case of waveguides such as single-mode optical fibers, the dispersion parameter is related to GVD as shown in the following equation and is expressed in units of ps / (nm·km).

[0367]

number

[0368] Unit conversion calculators are well known in the art, and for example, one implemented by RP photonics and accessible from its website www.rp-photonics.com can be used to convert bulk glass GVD values ​​to appropriate units for optical fibers.

[0369] The high dispersion required for complex conjugate resolution is the exact opposite of typical optical fiber designs that aim to minimize the chromatic dispersion of the fiber for a given wavelength.

[0370] However, dispersion can be increased in single-mode optical fibers by decreasing the fiber core diameter with respect to the center wavelength enough to increase the chromatic dispersion by a desired amount. Given industry common practice, the fiber core diameter of an optical fiber arises in discrete increments that do not independently give the desired chromatic dispersion with respect to a given length of the fiber.

[0371] Therefore, a combination of optical fiber types with an appropriate core diameter must be quantitatively determined to give the desired GVD value. Figure 17 shows a version of the method in Figure 18 in which, given the target GVD value and the required fiber length S1702, method 1400 can be used, and its output is adapted to obtain the GDD from the average GVD value and fiber length in S1704, or its output is used to obtain the optical fiber dispersion parameter by converting the average GVD value obtained in S1412 in S1706.

[0372] Figure 18 provides a more detailed schematic representation of a computer-implemented method that may be used to calculate the quantities of each fiber type required in some embodiments of the disclosed technology. Method 1800 includes: calculating the target GVD of the required fiber path length in S1802; converting the target GVD value to a target optical fiber dispersion parameter at a central wavelength of 850 nm of OCT illumination light in S1804; determining the fiber types that bound the target optical fiber dispersion parameter in S1806; obtaining the optical fiber dispersion parameter from the GVD at a central wavelength of 850 nm in S1808; and using this in S1810 to calculate the length of each fiber type required to satisfy the target GDD while maintaining the required path length.

[0373] Through the experiment, 31000(fs 2 ) and 46000(fs 2 It has been empirically determined that an additional GDD value between ) is necessary for the best CCR results in the system described above.

[0374] In some embodiments of the disclosed technology, the optical fiber components of the OCT reference assembly 1600 with adjustable optical path length include hybrid fibers, for example, hybrid optical fibers having the above-mentioned GDD value over their length. By using hybrid optical fibers having the above-mentioned GDD value, the alignment stability of the reference assembly can be maintained. In particular, given the operation of the OCT interferometer, the optical path length of the optical fiber is a fixed parameter, and therefore the optical fiber dispersion parameter must be sufficient to achieve the desired GDD based on the fixed fiber length.

[0375] Figures 19A and 19B illustrate, as mere examples, an alternative method for realizing a hybrid fiber 1900 based on two individual signal-mode fibers 1902a,b covering a target fiber length TL. In Figure 19A, one fiber component of the hybrid fiber has a diameter D1A and length TL1, and the other fiber component has a diameter or numerical aperture of D2A and length TL2, giving an aggregate length TL = TL1 + TL2 and an aggregate GDD that matches the target GDD, thereby achieving more effective removal of CC image artifacts in the resulting OCT scan. Figure 19B shows how configurations with different orders of optical fibers may be used in some embodiments.

[0376] Through the process outlined above, two fiber types were identified, and their combination provided the desired chromatic dispersion while maintaining the overall optical fiber path length. A successful combination consisted of a 5m length TL1 of Coherent 630-HP fiber and a 1m length TL2 of Corning HI780 fiber. The two fiber sections were then fusion spliced ​​together to create a single 6m fiber length, in other words, TL=6, with the desired chromatic dispersion in some embodiments of the reference arm optical assembly 103.

[0377] A highly dispersed single-mode hybrid optical fiber is located in one of the reference arms or probe arms of an optical interferometer, such as an optical interferometer equipped with an OCT system 100 as shown in Figure 1, in some embodiments of the disclosed technology. The hybrid fiber comprises at least two optical fibers, at least one of which has a different core diameter and different dispersion characteristics from at least one other optical fiber. The at least two optical fibers are fused together at their ends to form a hybrid optical fiber. Each of the at least two optical fibers is fused to at least one other optical fiber of the at least two optical fibers. Each of the at least two optical fibers has a length, for example, TL1 or TL2 as shown in Figure 19A or Figure 19B, based on the core diameter of the optical fiber with respect to the central wavelength of the light beam passing through the hybrid optical fiber and a target GDD per unit length of the hybrid optical fiber. The hybrid fiber adds an additional GDD value compared to the optical fiber in the other of the reference arm or probe arm of the optical interferometer.

[0378] In some embodiments, using dispersive component optical fibers within the reference arm can also facilitate power balancing with the probe beam when the reference beam and probe beam are later combined. If the dispersive element is located within the probe arm instead, in some embodiments, additional compensation within the reference arm may be required to improve the balance between the return reference beam power and the OCT beam power.

[0379] In some embodiments of the hybrid optical fiber 1900, an additional GDD value is 31000 (fs 2 ) and 46000(fs 2 )

[0380] In some embodiments of the hybrid optical fiber 1900, at least one type of optical fiber 1902a has a length TL1 that is different from the length TL2 of at least one other type of optical fiber 1902b in the hybrid optical fiber 1900.

[0381] The lengths TL1 and TL2 of the constituent optical fibers 1902a and b are determined, in some embodiments, by calculating the target group velocity delay (GVD) of a hybrid optical fiber of a predetermined length, converting the target GVD into a target optical fiber dispersion parameter (OFDP) at the center wavelength of light passing through the hybrid optical fiber, determining at least two optical fiber types, each having an OFDP that forms the boundary of the target OFDP, converting the OFDP of each determined optical fiber type into a GVD at the center wavelength, and for each of the determined optical fiber types, determining the length of the fiber based on the GVD of that fiber at the center wavelength, so that when the optical fibers are fused at their ends, an optical path matching a predetermined optical path length of the hybrid optical fiber is realized.

[0382] In some embodiments, the hybrid optical fiber 1900 comprises at least one length of Coherent 630-HP fiber and at least one length of Corning HI780 fiber, wherein at least one end of the predetermined length of Coherent 630-HP fiber is fused to the end of the predetermined length of Corning H1780 fiber.

[0383] In some embodiments of optical interferometers, such as the OCT system 100 disclosed herein, a hybrid fiber is positioned in the reference arm 103 of the optical interferometer and introduces differential dispersion to the reference arm 103 compared to the returned OCT imaging light obtained by scanning a sample using an OCT apparatus according to any of the disclosed embodiments.

[0384] In some embodiments, the hybrid fiber 1900 is configured to introduce a predetermined level of chromatic dispersion into, for example, the reference arm 103 of the optical interferometer of the OCT system 100, in order to remove complex conjugate image data from the OCT image output by the OCT device.

[0385] In some embodiments, the hybrid optical fiber 1900 is located within the reference arm of an optical interferometer configured to output OCT imaging data from an OCT device, and has a length of 6 meters, of which 5 meters include a Coherent 630-HP fiber or a fiber having similar optical properties, and 1 meter includes a Corning HI780 fiber or a fiber having similar optical properties. As will be apparent to those skilled in the art, in some embodiments other glasses having equivalent properties can be used; see, for example, the properties and parameters of these fibers in Table 1.

[0386] Example using highly dispersed custom-stretched single-mode fibers Some embodiments of the disclosed technology employ an interferometer design in which a highly dispersed custom-stretched single-mode fiber is used as part of an OCT interferometer reference arm, instead of fusing two or more single-mode optical fibers together at their ends to form a hybrid fiber.

[0387] Several embodiments of the disclosed technology utilize high-dispersion optical fibers to provide differential dispersion within an interferometer, supporting extended depth imaging in optical coherence tomography. These embodiments may be used in conjunction with the calculation methods described above with reference to Figures 8A, 8B, 9, 10, 11A, 11B, 13, and 14 of the accompanying drawings, and may also be used in some embodiments having bulk glass retroreflectors to further increase the amount of differential dispersion provided. The interferometer designs disclosed herein may be used in some embodiments in the OCT scanning system 100 of Figure 1. The OCT scanning system of Figure 1 may, in some embodiments, include an OCT scanner adapter 206 for a surgical microscope, incorporating features described by the embodiments disclosed herein and / or illustrated in Figures 2A, 2B, 3A, 3B, 4, 5A, 5B, 6, or 7.

[0388] To maintain single-mode propagation through an optical fiber having a desired dispersion parameter, a suitable bulk glass material having an appropriate GDD value must be quantitatively determined, which can be done using the method described above with reference to Figures 14, 17, and 18 of the drawings.

[0389] On the other hand, several glass materials having sufficient GVD were determined using the above method, and optical fiber dispersion parameters were found that enable the desired GDD based on a fixed fiber length of an OCT reference assembly with adjustable path length as described herein, for example, shown as reference assembly 1600.

[0390] However, for the manufacturing process of stretching bulk glass into optical fibers, only one candidate material was found that could provide the required dispersion over the optical path length TL of the reference assembly 1600. This included a high-dispersion fiber with a GVD that, based on the calculations above, was found to match that of Schott N-ZK7 glass, although other types of glass with the same refractive index, group refractive index, GVD, and transparency shown in Table 1 above can be used instead. An example of values ​​for these properties is 41816 (fs) at 850 nm. 2 This includes a GVD of 250 ps / (nm·km), which translates to a dispersion parameter of -109 ps / (nm·km) at 850 nm. If the optical path length in the reference assembly of the high-dispersion fiber is 6 meters, then the reference arm optical fiber path along its length is 250 ps 2 This will result in a total GDD value of ). This is below the target median value but acceptable above the minimum acceptable GDD value.

[0391] Therefore, some embodiments of the disclosed technology include a highly dispersed single-mode optical fiber containing stretched bulk optical glass.

[0392] In some embodiments, a highly dispersed single-mode optical fiber has a glass dispersion coefficient measured using the Sellmeier method, and exhibits a frequency of 31,000 fs for a given wavelength of 860 nm in a bandwidth of 100 nm. 2 ~46000fs 2 This includes bulk optical glass having optical fiber dispersion parameters related to the group delay dispersion (GDD) value.

[0393] In some embodiments, a highly dispersed single-mode optical fiber is located within the reference arm of an optical interferometer configured to output OCT imaging data from an OCT device.

[0394] In some embodiments, the optical fiber is made of stretched bulk Schott N-ZK7 optical glass or stretched bulk optical glass having the same refractive index, group refractive index, GVD, and transparency characteristics as described in Table 1 above.

[0395] In some embodiments, the highly dispersed optical fiber can be selected by using a computer-implemented method for determining the group velocity delay, i.e., GVD, of a highly dispersed single-mode optical glass having, for example, bulk stretched optical glass, and determining GDD or GDD for a given fiber length, wherein the method includes: determining a target GVD value based on inputs including at least a target group dispersion delay (GDD) value and the optical path length along the optical fiber; solving the Sellmeier dispersion equation for the refractive index of the optical glass as a function of wavelength for the wavelength interval; determining a coefficient of GVD as a function of wavelength for each of a plurality of incremental wavelength intervals within a given bandwidth (804); determining the second derivative of the refractive index with respect to wavelength; multiplying the coefficient of GVD as a function of wavelength by the second derivative of the refractive index with respect to wavelength; averaging the GVDs determined over the bandwidth to determine the average GVD over the bandwidth, thereby iteratively determining the average GVD for that wavelength interval.

[0396] In some embodiments, the method further includes calculating the GDD from the average GVD value and fiber length.

[0397] In some embodiments, the method further includes converting the average GVD determined over bandwidth into optical fiber dispersion parameters.

[0398] In some embodiments, high-dispersion optical fibers are used in optical OCT interferometer assemblies within the detector arm of an OCT assembly, such as the OCT system 100 shown in Figure 1.

[0399] In some embodiments, the OCT interferometer assembly may comprise an OCT detector assembly, such as a spectrometer 136 shown in the exemplary OCT system 100 of Figure 1; a sample arm configured to guide OCT probe beam light from the OCT assembly back from the scanned object toward the OCT detector assembly; and a path-length adjustable OCT system reference assembly comprising a fixed-path-length, high-dispersion single-mode optical fiber including bulk-stretched optical glass, the reference assembly being located within the reference arm of the OCT detector assembly.

[0400] In some embodiments, the interference patterns of the return reference beam and OCT beam in the detector assembly undergo a Fourier transform, and the chromatic dispersion along the reference beam path in the reference arm of a high-dispersion single-mode optical glass fiber OCT system is sufficient to remove complex conjugate artifacts from the Fourier transform of the interference signal output by the OCT interferometer by using a complex conjugate resolution (CCR) method basis.

[0401] In some embodiments, the dispersion along the optical glass optical fiber is sufficient to allow the CCR method to remove complex conjugate artifacts from OCT B scans or stereoscopic scans in real time.

[0402] In some embodiments, based on a fixed fiber length of a single-mode optical fiber including optical glass, the optical fiber dispersion parameter is 31000fs 2 ~46000fs 2The system is configured to provide a group delay variance (GDD) value, which can be determined using a preferred method such as one of the methods disclosed herein with reference to Figures 14 to 18 of the attached drawings.

[0403] In some embodiments, the optical glass includes Schott N-ZK7 optical glass, or optical glass having equivalent refractive index, group refractive index, GVD, and transparency characteristics, for example, the parameter values ​​listed in Table 1 above.

[0404] In some embodiments, the determined dispersion parameter of an optical fiber made of optical glass is approximately -10⁹ ps / (nm·km) at a wavelength of 850 nm.

[0405] In some embodiments, the optical path length of the optical fiber is approximately 6 meters, and the GDD is approximately 250 ps 2 That is the case.

[0406] The above embodiments can be combined with other disclosed embodiments of the same or different aspects of the disclosed technology in any preferred manner that will be apparent to those skilled in the art.

[0407] High-dispersion single-mode optical fibers, including stretched bulk optical glass in some embodiments, may be configured as optical fibers in the reference arm of an interferometer in some embodiments, such as the OCT scanning system 100 in Figure 1. This can help resolve the depth of B-scan and stereoscopic scans in live OCT scanning streaming using the OCT scanning system, for example, by allowing the use of faster techniques for the complex conjugate resolution of the scanned image. However, in some embodiments, other glasses with equivalent properties, such as those listed in Table 1 above, may be used.

[0408] The terms used herein are for illustrative purposes only and do not limit the disclosure. Where used herein, the singular forms "a," "an," and "the" are intended to include the plural form unless the context explicitly indicates otherwise.

[0409] As used herein, the term "and / or" includes all possible combinations of one or more of the related items and may be abbreviated as " / ".

[0410] It will be further understood that, when used herein, the terms “comprises,” “comprising,” “includes,” and / or “including,” specify the presence of the described features, integers, steps, actions, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, actions, elements, components, and / or groups thereof.

[0411] The terms "first," "second," etc., may be used herein to describe various elements, but it will be understood that these elements should not be limited by these terms. These terms are used solely to distinguish one element from another. For example, without departing from the scope of this disclosure, the first element may be referred to as the second element, and similarly, the second element may be referred to as the first element.

[0412] Relative terms such as "below," "above," "upper," "lower," "horizontal," and "vertical" may be used herein to describe the relationship between one element and another, as shown in the figure. It will be understood that these terms, and the terms described above, encompass different orientations of the device in addition to the orientation shown in the figure. When one component is referred to as being "connected" or "bonded" to another component, it should be understood that it may be directly connected to or bonded to the other component, but there may also be other components in between. In contrast, when one element is said to be "directly connected" or "directly bonded" to another element, there are no intervening elements.

[0413] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as those generally understood by those skilled in the art to which this disclosure belongs. Terms used herein should be construed to have meanings consistent with those in the context of this specification and related art, and it will be further understood that they should not be construed in an idealized or overly formal sense unless expressly defined herein.

[0414] While several embodiments have been described in the context of the apparatus, it is clear that these embodiments also represent descriptions of the corresponding methods, where blocks or apparatus correspond to steps or features of steps. Similarly, embodiments described in the context of steps also represent descriptions of the corresponding blocks, items, or features of the corresponding apparatus.

[0415] Some embodiments relate to a microscope 200 equipped with an SD-OCT scanner system 100, the SD-OCT scanner system 100 using an OCT scanner adapter 206 to generate OCT A and B scans using image processing techniques disclosed herein, such as those described in relation to one or more of Figures 1 to 12. Optionally, the microscope 200 may be part of the OCT system 100 or connected to the OCT system 100, as described in relation to one or more of Figures 1 to 12.

[0416] Figure 13 shows a schematic diagram of a system 1300 configured to perform one embodiment of a computer-implemented image processing method 900 as described herein. The system 1300 comprises a microscope 1302,200 and a computer system 1306 having a display 1308. The microscope 1302,200 is configured to capture images and is connected to the computer system 1306. In some embodiments, the connection may include a preferred data connection via a port 212 schematically shown in Figures 2B, 3A, 3B, and 4. In some embodiments, the computer system 1306 may include an image processing device 148. The computer system 1306 is configured to perform at least part of the methods described herein, such as one embodiment of method 900 that includes using one embodiment of algorithm 1000. In some embodiments, the computer systems 1306,148 may be configured to perform machine learning algorithms.

[0417] The computer systems 1306,148 may be local computer devices (e.g., personal computers, laptops, tablet computers, or mobile phones) having one or more processors and one or more storage devices, or they may be distributed computer systems (e.g., cloud computing systems having one or more processors and one or more storage devices distributed to various locations such as local clients and / or one or more remote server farms and / or data centers).

[0418] Computer systems 1306,148 may include any circuit or combination of circuits. In one embodiment, computer systems 1306,148 may include one or more processors, which may be of any kind. As used herein, processors may be intended to be any kind of computing circuit, such as, for example, a microprocessor for a microscope or microscopic component (e.g., a camera), a microcontroller, a composite instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a graphics processor, a digital signal processor (DSP), a multicore processor, a field-programmable gate array (FPGA), or any other kind of processor or processing circuit. Other kinds of circuits that may be included in computer system X20 may be custom circuits, application-specific integrated circuits (ASICs), etc., such as one or more circuits (communication circuits, etc.) used in wireless devices such as mobile phones, tablet computers, laptop computers, two-way radios, and similar electronic systems. Computer system X20 may include one or more storage devices that may include one or more memory elements suitable for a particular purpose, such as main memory in the form of random access memory (RAM), one or more hard drives and / or one or more drives that handle removable media such as compact discs (CDs), flash memory cards, digital video discs (DVDs), etc. Computer system X20 may also include a display device, one or more speakers and a controller that may include a keyboard and / or a mouse, trackball, touchscreen, voice recognition device, or any other device that enables the system's user to input information into and receive information from computer systems 1306,148.

[0419] Some or all of the steps disclosed herein may be performed by (or using) hardware devices such as a processor, microprocessor, programmable computer, or electronic circuit. In some embodiments, some, one or more of the steps may be performed by such devices.

[0420] Depending on certain implementation requirements, embodiments of the disclosed technology may be implemented in hardware or software. This implementation is executable by a non-transient recording medium, which is a digital recording medium, etc., that stores electronically readable control signals and cooperates (or can cooperate) with a programmable computer system to carry out each method. Examples include floppy disks, DVDs, Blu-rays, CDs, ROMs, PROMs and EPROMs, EEPROMs, or FLASH memory. Thus, the digital recording medium may be computer-readable.

[0421] Some embodiments of the disclosed technology include a data carrier having electronically readable control signals that can cooperate with a programmable computer system so as to carry out any of the methods described herein.

[0422] Generally, embodiments of the present invention can be implemented as a computer program product comprising program code, which operates to perform one of the methods when the computer program product is executed on a computer. This program code may be stored, for example, on a machine-readable carrier.

[0423] Another embodiment includes a computer program stored in a machine-readable carrier for carrying out any of the methods described herein.

[0424] Therefore, in other words, embodiments of the present invention are computer programs having program code for carrying out any of the methods described herein when the computer program is executed on a computer.

[0425] Accordingly, another embodiment of the present invention is a recording medium (or data carrier or computer-readable medium) containing a stored computer program for carrying out any of the methods described herein when executed by a processor. The data carrier, digital recording medium, or recording medium is typically tangible and / or non-transient. Another embodiment of the present invention is an apparatus, such as those described herein, comprising a processor and a recording medium.

[0426] Therefore, another embodiment of the disclosed technology is a data stream or signal sequence representing a computer program for carrying out any of the methods described herein. The data stream or signal sequence may be configured, for example, to be transmitted over a data communication connection, such as the Internet.

[0427] Another embodiment includes processing means, for example, a computer or programmable logic device configured or adapted to carry out any of the methods described herein.

[0428] Another embodiment includes a computer having an installed computer program for carrying out any of the methods described herein.

[0429] Another embodiment of the disclosed technology includes an apparatus or system configured to transfer (e.g., electronically or optically) a computer program for carrying out any of the methods described herein to a receiver. The receiver may be, for example, a computer, a mobile device, a storage device, etc. The apparatus or system may include, for example, a file server for transferring the computer program to the receiver.

[0430] This disclosure is not limited to the embodiments described above and illustrated in the drawings, and it should be understood that those skilled in the art will recognize that many changes and modifications can be made within the scope of this disclosure and the attached claims. The embodiments disclosed in the drawings and specification are illustrative and not restrictive, and the scope of the concept of the invention is set out in the following claims.

Claims

1. A highly dispersed single-mode hybrid optical fiber (1900) located in one of the reference arm or probe arm of an optical interferometer imaging system, wherein the hybrid optical fiber (1900) is The device comprises at least two optical fibers (1902, 1902), wherein at least one of the at least two optical fibers has a different core diameter and a different dispersion characteristic than the other optical fiber at least one of the at least two optical fibers. The aforementioned two optical fibers are fused together at their ends to form a hybrid optical fiber. Each of the at least two optical fibers has a length based on the core diameter of the optical fiber with respect to the central wavelength of the light beam passing through the hybrid optical fiber, and a target GDD per unit length based on the target length of the hybrid optical fiber, The hybrid optical fiber adds an additional GDD value compared to the optical fiber in the other of the reference arm or probe arm of the optical interferometer.

2. The aforementioned additional GDD value is 31000 (fs ２ ) and 46000 (fs ２ A hybrid optical fiber according to claim 1, which is between ) and ).

3. The hybrid optical fiber according to claim 1 or 2, wherein at least one type of optical fiber has a length different from the length of at least one other optical fiber in the hybrid optical fiber.

4. The length of each optical fiber is Calculating the target group velocity delay (GVD) for a hybrid optical fiber of a predetermined length, Converting the aforementioned target GVD into a target optical fiber dispersion parameter (OFDP) with respect to the central wavelength of light passing through the hybrid optical fiber, Determine at least two optical fiber types, each having an OFDP that borders the target OFDP, Converting the OFDP of the determined type of optical fiber to the GVD of the center wavelength, The hybrid optical fiber according to any one of claims 1 to 3, wherein for each of the determined types of optical fibers, the length of the fiber is determined based on the GVD of each fiber at the central wavelength, so that the optical fibers, when fused at their ends, collectively realize an optical path that matches a predetermined optical path length of the hybrid optical fiber.

5. The hybrid optical fiber according to any one of claims 1 to 4, comprising a Coherent 630-HP fiber of a predetermined length and a Corning HI780 fiber of a predetermined length.

6. A hybrid optical fiber according to any one of claims 1 to 5, positioned in the reference arm of an optical interferometer imaging system equipped with an OCT device.

7. The hybrid optical fiber according to claim 6, wherein the hybrid fiber is configured to introduce a predetermined level of wavelength dispersion into the reference arm of the optical interferometer to remove complex conjugate image data from the OCT image output by the OCT device.

8. Located on the reference arm of an optical interferometer configured to output OCT imaging data from an OCT device, A hybrid optical fiber according to any one of claims 1 to 7, wherein the hybrid optical fiber path length of 6 meters comprises 5 meters of Coherent 630-HP fiber and 1 meter of Corning HI780 fiber.

9. An OCT assembly comprising an OCT interferometer assembly, wherein the OCT interferometer assembly is OCT detector assembly (136), A sample arm (105) is configured to guide the OCT probe beam light from the OCT light source of the OCT assembly toward the target (116) and to guide the return OCT probe beam light from the scanned target toward the OCT detector assembly, A reference assembly for an OCT system with adjustable optical path length, comprising a hybrid optical fiber according to any one of claims 1 to 8, The reference assembly is configured on the reference arm (103) of the OCT detector assembly, The OCT light from the OCT light source is split so that it travels as a reference beam along the reference arm (103) and as the OCT probe beam along the sample arm (105). The return reference beam and the return probe beam are coupled, The OCT detector assembly (136) is configured to detect interference in the coupled OCT light returning from the reference arm (103) and the sample arm (105), in an OCT assembly.

10. The OCT interferometer assembly further comprises an image processor (148), wherein the OCT detector of the OCT interferometer assembly is configured to output a signal (146) to the image processor (148) that includes the detected interference pattern of the returned coupled OCT light. The OCT assembly according to claim 9, wherein the interference patterns of the return OCT reference light and the OCT probe light are Fourier transformed by the image processor (148).

11. The image processor (148) is configured to perform a computer-implemented complex conjugate resolution (CCR) method to remove complex conjugate artifacts from the Fourier-transformed signal. The OCT assembly according to claim 9 or 10, wherein the reference beam optical path in the hybrid optical fiber OCT system reference arm (103) generates sufficient wavelength dispersion in the reference beam to enable the CCR method to remove the CC artifact in real time.

12. The chromatic dispersion along the hybrid glass fiber is sufficient to enable the computer-implemented CCR method to remove the complex conjugate artifact from the OCT B scan or stereoscopic scan in real time, according to claim 11, for the OCT interferometer.

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