Compact MEMS 2D MEMS scanning mirror assembly design and related aspects

Abstract

A microelectromechanical systems (MEMS) two-dimensional scanning mirror assembly (310) has an optical design including a movable MEMS scanning mirror having a reflective surface (334), a point light source (308a) for a light beam, a collimating lens assembly (516) configured to receive light from the light source and output a collimated light beam toward the reflective surface (334) having an exit beam diameter greater than a threshold, and objective lens assemblies (510, 512) through which the collimated light beam reflected from the reflective surface exits the scanning mirror assembly. The reflective surface (334) is configured to reflect the incident collimated light beam to form a probe beam (312), which exits the mirror assembly as a telecentric beam (312) toward a telecentric image plane with a resolution better than a telecentric beam resolution threshold. The scanning mirror assembly optics are configured to provide a total track length L from the point light source to the telecentric image plane (700) of less than 40 mm.

Description

[Technical Field]

[0001] The present disclosure relates to compact two-dimensional MEMS (Micro Electro Mechanical Systems) based mirror assemblies and related aspects, particularly, but not exclusively, to scanning mirror designs suitable for compact optical coherence tomography (OCT) and related aspects.

[0002] Optical coherence tomography (OCT) is performed using optical devices to generate cross-sectional images of biological tissue. Using monochromatic light with a constant phase difference, it is possible to achieve axial (depth) resolution well below 8 microns. While OCT scanning cannot penetrate to great depths, it can provide depth scanning of tissues used in medical fields such as ophthalmology and dermatology, as well as surgical applications. Therefore, when probing biological tissues (in vivo) in real time, as well as in other applications, it is desirable to be able to use such OCT systems to generate images with depth information. To generate images with depth information, multiple one-dimensional scans, known as A-scans, are performed along a scan line, and these A-scans are stacked and combined to generate a two-dimensional image, known as a B-scan. By acquiring B-scans sufficiently close together and rapidly, a three-dimensional image of the OCT-probed sample tissue can also be obtained.

[0003] To generate a three-dimensional image, an OCT scanner scans a sample using a beam path spanning two spatial locations. Such scanning systems known in the art typically use orthogonal galvanometer mirrors to address the desired two-dimensional spatial location of the sample. To avoid Petzval curvature of the resulting interference image plane caused by the spatial separation of the galvanometer mirrors, relay optics are required to combine the pupils of each scanning mirror into a common pupil, which can then be focused onto an image plane of a common optical path length for each galvanometer mirror. Alternatively, electromechanical 2D scanning mirror systems using a single pupil for each scanning axis are also known in the art, but these operate at much slower scanning speeds due to the physical size limitations of this technology, making them less desirable than systems capable of faster scanning.

[0004] OCT scanners are available for use in a variety of surgical procedures where depth information is advantageous. For surgical procedures in small areas or when access to the tissue region to be operated on is limited, such as when using an OCT scanner during ophthalmic surgery, the form factor of the OCT scanner must be significantly different from that of an OCT scanner where access to the region probed by the OCT scanner is not limited or is not required while the OCT scan is in progress.

[0005] The use of OCT scanners when performing surgical procedures imposes additional design constraints on the form factor of the OCT device. One such constraint is the physical limit on the size of the combined microscope and OCT adapter. For example, the overall height of the OCT device and any attached microscope used by a surgeon performing a surgical procedure is limited by design so that the surgeon can view the area being scanned through the microscope while still accessing the area under the OCT / microscope using surgical tools to perform the surgical procedure.

[0006] A factor that influences the overall size of an OCT scanner is the size of the scanning mirror assembly. Microelectromechanical systems (MEMS)-based optical reflective devices can be used to reduce the physical size limitations of the scanning mirror assembly and support higher scan rates, but MEMS mirrors have small effective apertures. Small numerical aperture optical designs for OCT applications either result in low lateral resolution at the image plane or require complex optical designs due to the use of a converging light beam incident on a small-aperture MEMS mirror.

[0007] For applications such as metrology or intraoperative OCT, which benefit from a flat tomographic image plane, the spatial separation of galvanometer mirrors requires relay optics to combine the pupils of each scanning mirror into a common pupil and then focus them onto the image plane. This results in a large, multi-optical element scanner design that is less desirable for intraoperative systems requiring minimal sterile field volume. Optical designs based on small-numerical aperture reflective scanners result in low-numerical aperture designs, and the use of convergent light beams with large angles of incidence on small-aperture MEMS mirrors results in poor lateral resolution or complex optical designs.

[0008] Therefore, the design of surgical OCT scanning systems, particularly those for ophthalmic surgery where the OCT light must access the interior of the eye through the eye's pupil, is subject to various design constraints. Using an OCT scanner during ophthalmic surgery can impose various, potentially conflicting, design constraints. To keep the microscope height or other device dimension between the surgeon and the tissue orientation being operated on as short as possible, depending on the microscope's form factor, it is known in the art to replace the microscope objective with an objective lens that is part of the OCT scanner system. The OCT scanner system objective lens is aligned with the optical channel of the microscope optics, allowing the OCT scanner to use the same focal plane as the microscope. However, known OCT microscope adapter systems currently have form factors that add at most about 50 mm to the microscope's stack height when attached. Therefore, it is desirable to improve the optical design of OCT adapters to better minimize these stack heights (or other dimensions between the surgeon and the surgical field) when the microscope and OCT adapter assemblies are secured together. Reducing the stack height can improve access to the area probed by the OCT scan for surgical procedures.

[0009] Summary of the Invention The disclosed technology seeks to alleviate or eliminate at least some of these design limitations by providing an improved MEMS-based optical design for a scanning mirror assembly suitable for OCT scanner applications. In particular, but not exclusively, some embodiments of the disclosed technology provide an ultra-compact, large-numerical-aperture MEMS-based 2D point-source optical design that achieves large angles of incidence at the scanning mirror to reduce compound angle coupling when performing two-dimensional (2D) scanning. Some embodiments of the disclosed technology enable OCT images to be generated with high lateral optical resolution from an optical path-length equivalent image plane. Given the size and dimensions of the optical components of an OCT scanner adapter, there are limitations to obtaining the smallest possible footprint (and volume). However, by varying at least the internal optical geometry, including the design of the scanning mirror assembly, the beam direction, and the deflection angle through the objective lens also used in the microscope, a more compact OCT scanner adapter can be achieved that fits within the footprint of a surgical microscope and has a reduced vertical stack height. However, achieving this reduction is not easy due to limitations on the size of optical components and the need to fit optical geometries within such limited spaces.

[0010] The following summary description presents features of the disclosed technology that may be preferred features in some embodiments. The present invention is defined by the appended claims.

[0011] The disclosed technology relates to scanner designs and related aspects that are suitable for, but not limited to, OCT scanning applications. Some embodiments of the disclosed technology provide OCT scanners with optical configurations that support particularly compact housing designs. Such designs are beneficial for use in surgical applications, where the OCT scanner serves as an adapter for a microscope.

[0012] According to a first aspect of the disclosed technology, there is provided a microelectromechanical system (MEMS) two-dimensional scanning mirror assembly, the scanning mirror assembly including a scanning mirror optical system, the scanning mirror optical system including at least a movable reflective surface of the MEMS scanning mirror, the movable reflective surface being movable in two dimensions; a collimating lens assembly configured to receive a scanning light beam from a scanning light source and output a collimated scanning light beam toward the reflective surface, the collimated scanning light beam having an output beam diameter from the collimating lens assembly; and an objective lens assembly, the collimated scanning light beam reflected from the reflective surface having an output beam diameter from the objective lens assembly. and an objective lens assembly that exits the scan mirror assembly through a reflective surface, wherein the scan mirror assembly optics are configured to reflect an incident collimated scanning light beam towards the objective lens assembly to form a telecentric scan beam that exits the mirror assembly telecentrically towards a telecentric image plane, wherein as the reflective surface moves during scanning, the point at which the telecentric scanning light beam focuses in the telecentric image plane changes, and wherein at least the position and dimensions of the scan mirror optics within the scan mirror assembly are configured to minimize a track length L from the light source to the telecentric image plane.

[0013] By configuring the scan mirror assembly to have a track length of 40 mm or less, the lateral footprint of the scan mirror assembly is kept small, which allows the scan mirror assembly to be housed within a scanner housing that also has a small lateral footprint.

[0014] In some embodiments, the scanning mirror assembly comprises an optical block.

[0015] In some embodiments, the optical block is connected to a light source for the scanning light beam. The scanning light source may be hosted on a separate device, and the scanning light may in some embodiments be injected along an optical fiber from that device.

[0016] In some embodiments, the light source for the scanning light beam in the optical assembly is a point light source, such as the end of an optical fiber with one end connected to the light source for the scanning beam. Light from the optical fiber can be incident on the scanning mirror assembly via an optical fiber connector.

[0017] In some embodiments, the position and dimensions of the scanning mirror optics within the mirror assembly define a track length L from the light source to the telecentric image plane, where the track length L is 40 mm or less.

[0018] In some embodiments, the scanning light is received by the scanning mirror assembly through an optical fiber end face acting as a point light source. In some embodiments, the numerical aperture of the optical fiber acting as the point light source and the focal length of the collimating lens assembly set the exit beam diameter of the scanning light beam from the collimating lens to at least 3.1 mm.

[0019] In some embodiments, the scanning light source, e.g., the source of scanning light in the scanning mirror assembly, comprises an optical fiber end face that provides a point light source, and the numerical aperture of the point light source and the focal length of the collimating lens assembly are configured such that the exit beam diameter of the scanning light beam from the collimating lens is at least 3.1 mm.

[0020] In some embodiments, the design threshold for telecentric beam resolution at the telecentric image plane is better than 6 microns, in other words, the image can be resolved to an extent of less than 6 microns.

[0021] In some embodiments, the numerical aperture of the optical fiber and the focal length of the collimating lens assembly set the collimating lens exit beam design threshold to at least 3.1 mm.

[0022] In some embodiments, the combination of the focal lengths of the scan mirror objective lens and the scan mirror field lens through which the scan or probe beam exits the mirror assembly determines the total track length L.

[0023] In some embodiments, the mirror assembly scans + / - 5 degrees, for example, the reflective surface (334) may be configured to move within + / - 5 degrees about each of two orthogonal axes x, y, which in some embodiments intersect at the optical center of the scanning mirror's reflective surface.

[0024] In some embodiments, the optical fiber has a numerical aperture of 0.14.

[0025] In some embodiments, the objective lens assembly optics comprises an objective lens and a field lens, and the total track length L depends on the combined focal length of the objective lens assembly optics.

[0026] In some embodiments, the objective lens comprises an F2.7 biconvex doublet lens and the field lens comprises an F19 positive / negative meniscus doublet field lens.

[0027] In some embodiments, the optical path difference (OPD) of the telecentric scan or probe beam output by the scanning mirror assembly has a radius of curvature greater than 100 mm.

[0028] In some embodiments, the telecentric beam is telecentric at the telecentric image plane to better than a 0.03 degree angle of incidence.

[0029] In some embodiments of the MEMS scanning mirror assembly, the reflective surface of the MEMS scanning mirror comprises a large diameter gold coated silicon mirror bonded to an underlying mechanical structure.

[0030] In some embodiments, the reflective surface comprises a large diameter gold coated silicon mirror bonded to the underlying mirror movement mechanical structure of a MEMS scanning mirror assembly.

[0031] In some embodiments, the mirror assembly is a scanning mirror in an OCT scanner device, and the optical fiber provides a point source for the OCT light beam.

[0032] In some embodiments, the scanning mirror assembly is implemented within the housing of the OCT scanner adapter.

[0033] In some embodiments, the OCT scanner device is an OCT adapter scanner for a microscope, preferably a surgical microscope.

[0034] In some embodiments, the MEMS scanning mirror assembly is provided as an optical block in an optical coherence tomography (OCT) scanner, the scanning light beam comprises an OCT probe beam, and the light source comprises an optical fiber having an end face that acts as a point source for the OCT probe beam.

[0035] In some embodiments, by using an optical design that results in an internal track length of 40 mm or less within the scanning mirror assembly, the housing of the OCT scanner adapter can be mounted to the lower carriage of a surgical microscope and fit within at least the lateral footprint of the surgical microscope to which the OCT scanner housing is attached.

[0036] In some embodiments, the OCT probe beam provides a depth scan of the sample, and the OCT light returning from the sample has a lateral optical resolution of 6 μm or better.

[0037] In some embodiments, the OCT light returned from the sample along the OCT probe arm has a lateral optical resolution of 6 μm or better, in other words, a resolution of better than 166 line pairs per mm.

[0038] In some embodiments, the OCT scanner is provided as an OCT scanner adapter for a surgical microscope, for example as an accessory.

[0039] According to another aspect of the disclosed technology, there is provided a spectral domain optical coherence tomography scanner system including an optical interferometer arrangement, the scanner system comprising: an illumination arm including a light source; a scanning depth reference arm; a scanning arm; and a coupler connected to a detection arm, wherein an illumination light beam from the light source is incident on the coupler along the illumination arm, and the illumination light beam is split by the coupler into a scanning depth reference light beam that follows the scanning depth reference arm towards a reflective surface and a scanning light beam that follows the scanning arm towards a sample to be scanned, the scanning arm comprising a scanning mirror assembly according to the first aspect or any one of its preferred embodiments configured to move the scanning light beam over the sample such that light returned from the sample is returned along the scanning arm towards the coupler, and the returned light from the scanning arm and the scanning depth reference arm is directed by the coupler to an interference detector located in a detector arm configured to detect interference between the returned light from the scanning arm and the returned light from the scanning depth reference arm, and the interference detector is configured to output data including an OCT interference signal of the returned light for image processing to generate a tomogram of the scanned sample.

[0040] In some embodiments, the scanner system comprises an image processor configured to process the received OCT interference signals and output an OCT image for display.

[0041] In some embodiments, the scanner system comprises at least one display and an image processor configured to process the received OCT interference signals and output the OCT image to the at least one display.

[0042] In some embodiments, a MEMS 2D scanning mirror assembly comprises a MEMS 2D OCT scanning mirror comprising at least a movable MEMS scanning mirror having a reflective surface; a fiber optic connector configured to accept an optical fiber that serves as a point source for an OCT beam that illuminates the reflective surface; and a collimating lens assembly configured to output OCT light from the point source toward the reflective surface with an exit beam diameter of at least 3.1 mm, wherein the reflective surface is configured to reflect the incident collimated OCT light beam to form an OCT scan or probe beam that exits the mirror assembly as a telecentric beam toward a telecentric image plane with a resolution of up to 6 microns, and wherein the optics of the scanning mirror assembly are configured to achieve a total track length L from a) an end face of the fiber ferrule that provides the point source inserted into the fiber optic connector to b) the telecentric image plane of less than 40 mm.

[0043] In some embodiments of the scanner system, an objective lens assembly is implemented in the probe arm of the scanning mirror assembly to create a telecentric OCT beam.

[0044] Another aspect of the disclosed technology includes an optical coherence tomography (OCT) scanner system including a microelectromechanical systems (MEMS) two-dimensional scanning mirror assembly according to the first aspect or any of the embodiments thereof disclosed herein.

[0045] Advantageously, some embodiments of the disclosed technology relate to an OCT scanner system that includes an OCT scanner adapter for a surgical microscope that includes an exemplary embodiment of the MEMS scanning mirror assembly disclosed herein. The OCT scanner adapter configuration according to the disclosed technology is compact in the sense that the optical design of the MEMS scanning mirror allows the optical channel formed by the microscope optics and the attached OCT scanner objective to require an optimally short housing stack height. The optical design also allows the OCT scanner adapter housing to be laterally compact, as the optical path that the OCT probe light follows within the scanning mirror assembly block is less than 40 mm. Some embodiments of the design also allow the resulting OCT images to be generated with a resolution of 6 microns or less.

[0046] This is useful in ophthalmic surgery where a surgeon needs to use a microscope or similar device to generate a magnified image of the surgical area using microscopic optics. By providing a magnified view of the surgical area, the surgeon can better see the tissue being operated on while at the same time keeping the patient within arm's reach.

[0047] Some embodiments of the OCT scanner system design disclosed herein result in a combined stack height of the microscope and attached OCT scanner adapter 206 that is much shorter than previously possible. The present 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 area being scanned within the focal plane of the microscope optics, while still allowing the surgeon to physically reach the scanned area to perform the surgical procedure.

[0048] Other aspects of the compact design provide additional benefits, for example, the design of the scanning mirror assembly reflects the beam used for scanning mirror position feedback in a different optical plane than 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 chance of returning light from the feedback arm contaminating the mirror position reference beam or its light source, or contaminating the OCT probe beam.

[0049] The above embodiments, the appended claims, and / or the examples disclosed herein above and below may be combined with one another as appropriate, as would be apparent to one skilled in the art.

[0050] Additional features and advantages are disclosed in the following description, claims, and drawings, and may be readily apparent to one skilled in the art who combines such features disclosed in the context of one aspect or embodiment above with those disclosed in the description. [Brief explanation of the drawings]

[0051] Some embodiments of the disclosed technology will now be described, by way of example only, and with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 shows a schematic diagram of the basic principles of a spectral domain OCT system. [Figure 2A] 2A-2C are schematic diagrams illustrating front and back perspective views of an OCT scanner adapter 206 for a microscope, in accordance with some embodiments of the disclosed technology. [Figure 2B] 2A-2C are schematic diagrams illustrating front and back perspective views of an OCT scanner adapter 206 for a microscope, in accordance with some embodiments of the disclosed technology. [Figure 3A] 2A-2C are schematic diagrams illustrating various views of components of an example OCT scanner adapter 206, in accordance with some embodiments of the disclosed technology. [Figure 3B] 2A-2C are schematic diagrams illustrating various views of components of an example OCT scanner adapter 206, in accordance with some embodiments of the disclosed technology. [Figure 4] FIG. 3C is an enlarged view of the OCT scanner adapter 206 shown in FIGS. 3A and 3B. [Figure 5A] 1A-1C are schematic diagrams illustrating an example of an optical design for a MEMS scanning mirror assembly in accordance with some embodiments of the disclosed technology. [Figure 5B] FIG. 5B is a schematic diagram illustrating further details of the input arm 518 of FIG. 5A. [Figure 6] FIG. 5B is a schematic diagram of an example collimating lens assembly for the input arm of FIG. 5A. [Figure 7] 1A-1C are schematic diagrams illustrating example objective lens assemblies for MEMS scanning mirror assemblies in accordance with some embodiments of the disclosed technology.

[0052] Detailed Description The detailed description set forth below provides examples of embodiments of the disclosed technology, described in sufficient detail to enable those skilled in the art to practice the disclosed technology.

[0053] There are two forms of OCT scanning: time-domain OCT (TD-OCT) and spectral-domain OCT (SD-OCT). SD-OCT uses spectral interrogation of the spectrum at the output of an OCT interferometer.

[0054] FIG. 1 illustrates schematically the operating principles of an exemplary Spectral Domain Optical Coherence Tomography (SD-OCT) interferometer scanner system 100, including some example embodiments of the disclosed technology.

[0055] In the exemplary SD-OCT system 100 shown in FIG. 1, the SD-OCT system 100 can be used to generate optical coherence tomographic images of an in vivo tissue sample 116, such as a human eye, by probing within the tissue sample 116 using an OCT optical scanning beam.

[0056] It should be apparent that system 100 is shown schematically in Figure 1 and is not drawn to scale. The locations of the various components of SD-OCT system 100 and their relative sizes shown in Figure 1 do not necessarily reflect their actual or relative locations or sizes in exemplary embodiments of the disclosed technology.

[0057] Hereinafter, references to OCT scan images or image data may refer to a one-dimensional A-scan, or a two-dimensional B-scan comprising multiple A-scans, or a volumetric scan image comprising multiple B-scans, as appropriate, as will be apparent to those skilled in the art.

[0058] As shown in FIG. 1 , the SD-OCT system 100 includes a low-coherence broadband optical scanning light source 102. The scanning light source 102 is suitably connected to a coupler 104 configured to split light from the light source 102 into an OCT optical reference beam that follows optical path 103a along a reference arm 103 and an OCT optical probe or scanning beam that follows optical path 105a along an OCT probe arm 105. The OCT light returned along the reference arm 103 and the probe arm 105 has different phase shifts that create 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. An 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 generates OCT scan data that can then be displayed on a suitable display 152.

[0059] The different phase shifts between the OCT light returned from the reference arm and the OCT light returned from the probe arm, resulting in a detected interference pattern, arise 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 contain a different type of target of interest 112 than an in vivo tissue sample located in a region of the human body.

[0060] The phase shift that produces the interference is affected by the different depths to which the OCT light is returned by structures within the scanned sample. The interference from the phase shift allows the signal output 146 of the spectrometer 136 to be used to produce an image known as a tomography that provides a visual indication of the depth of one or more such structures within the scanned or probed region and their location within the scanned or probed region.

[0061] 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 achieve broadband low-coherence OCT scanning light over a desired bandwidth.

[0062] The probe OCT beam is returned after being backscattered, reflected, or otherwise returned from any structures at a particular depth within the region 116 containing the tissue sample being scanned. In some embodiments, one or more or all of the optical paths 101 a, 103 a, 105 a, 107 a are realized using suitable single-mode optical fibers and may include one or more sections in which the beam following the optical fiber travels in free space.

[0063] In the embodiment of SD-OCT system 100 shown schematically in FIG. 1 , the reference beam exits coupler 104, travels along reference arm 103 through collimating lens 106, is then reflected by translating reference mirror 108, and travels back along reference arm 103 toward coupler 104. Optical path 103a along reference arm 103 and optical path 105a along probe arm 105 are configured with equivalent optical path lengths toward a focal plane 154 that illuminates the sample or other object of interest being scanned. Based on the detected interference between the returning reference beam light and the returning OCT probe beam light upon recombination at coupler 104, detected interference signal 146 can be output to image processor 148, thereby determining the depth of any structures within the sample that backscatter, reflect, or otherwise return the probe beam light.

[0064] In some embodiments, the interference between the returning reference beam and the returning OCT probe beam light occurring along output arm 107 is measured using a suitable spectrometer 136, such as that shown in Figure 1, to determine the depth of the cross-sectional image being scanned. Other embodiments of OCT system 100 may use other techniques to measure the interference and generate output signal 146.

[0065] In some embodiments of the OCT system 100, one or more or all of the optical paths 101a, 103a, 105a, 107a comprise suitable single-mode optical fibers and / or include one or more sections in which the outward or inward (relative to the coupler 104) OCT beam travels in free space following an optical fiber.

[0066] In some embodiments of the disclosed technology, the optical path lengths traversed by the reference and probe beams are matched, but the dispersion characteristics of the optical fiber through which each beam travels are configured to be different to improve removal of the complex conjugate image from the OCT image output, improving the image quality of the OCT scan image and the speed at which complex conjugate resolved OCT scan images are acquired.

[0067] In some embodiments, the term OCT scan is used herein to refer to B-scan and volumetric scan images of a tissue region (also referred to herein as a tissue sample) 116 generated using the spectral domain SD-OCT scanner system 100.

[0068] In the example of spectral domain OCT shown schematically in FIG. 1, a broadband light source 102 generates an OCT probe beam that illuminates a region of tissue 116 scanned by the OCT probe beam over a range of near-infrared wavelengths.

[0069] 1 includes a collimating lens 138 through which returning light passes through a grating 140 to produce a spectrally dependent interference pattern. The interference pattern is focused via an objective lens 142 onto a line camera 144, and an image signal representing the interference pattern is sent at output 146 to a suitable image processing system 148. However, in alternative embodiments, another suitable type of interference detector in output arm 107 could be used.

[0070] 1 measures the spectral interference of the returning OCT light beam by measuring the intensity modulation of the returning light as a function of frequency. The rate of change of intensity across different frequencies indicates the location of different reflective layers within the sample.

[0071] The OCT probe beam travels from the coupler 104 along the OCT probe branch 105 of the coupler 104 along optical path 105a before entering the OCT scanner 164. The exemplary OCT scanner 164 shown in FIG. 1 includes a collimating lens 110 and a scanning mirror assembly 310 (e.g., shown in FIGS. 3A and 5, described below) including a scanning mirror 112 having a reflective surface 334 (e.g., see FIG. 3A or FIG. 5) that deflects the OCT scanning beam from the scanner 164 through the objective lens 114 toward a focal plane 154 within the scanning region 116. The scanning mirror assembly 310 includes a mirror positioning system including 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 that includes the light source 158 and a mirror position detector (PSD) 160 for detecting the mirror position. 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.

[0072] The scanning mirror 112 may include a microelectromechanical system (MEMS) scanning mirror that is angularly moved by a mirror translation mechanism (not shown in FIG. 1 ). The movement of the scanning mirror 112 moves the OCT probe beam across the sample or other object of interest being scanned, and the resulting interference pattern is used to generate an OCT B-scan image from the system output 156.

[0073] Movement of the mirror mover is performed under the control of a controller 162. The controller 162 may be located within the scan mirror assembly that includes the scan mirror 112, or may be located remotely therefrom.

[0074] 1 includes an optical angular displacement mirror position measurement system 156, which provides feedback to the controller regarding the mirror position, allowing in some embodiments closed-loop control of the MEMS-based scanning mirror position in some embodiments.

[0075] The scanning mirror 112, when in use by the OCT scanner 164, is moved by a mirror translation mechanism under the control of a controller 162 to direct the OCT beam along a scan 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 a focal plane 154 at the sample tissue 116 being scanned. As shown schematically in Figure 1, the focal plane 154 is shown as being in a notional xy plane, with depth information provided orthogonally along the z axis.

[0076] The telecentric objective lens 114, through which the probe beam passes to reach the sample 116 and through which the returning probe beam light also passes, is shown in FIG. 1 with three exemplary emerging telecentric beams that focus at different positions within the focal plane 154, which is in the xy plane as shown in FIG. 1. Each of the exemplary emerging telecentric beams results from a different position of the scanning mirror assembly 112; in other words, FIG. 1 only shows three sequential telecentric beam positions, by way of example, in order to illustrate schematically how the telecentric OCT scan or probe beam is moved to illuminate different regions as the B-scan or volumetric scan progresses.

[0077] The scanned area includes a sample of tissue 116. In Figure 1, this includes tissue of the eye 116, which may be an in vivo or in vitro tissue sample. In other uses of the OCT scanner system, where OCT scanned images may be useful for visualizing internal structures at various depths within the tissue, other types of human or animal tissue may be scanned in vivo or in vitro.

[0078] For example, as shown in Figure 1, eye 116 is shown schematically with pupil 118 surrounded by iris 120, behind which is located posterior chamber 122 and zonular fibers 124, and in front of which is the eye's lens 126 and cornea 128. Figure 1 also shows anterior chamber 130 of the eye, as well as ciliary muscles 132 and ligaments 134, all of which may be scanned using an OCT system, such as OCT system 100, and shown as internal structures in a tomographic image presented on display 152.

[0079] The likelihood of a successful outcome from a surgical procedure performed on tissue, such as a human eye or the eye of another organism, where very limited access exists may 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 scans 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 procedure is performed. Providing this real-time depth information of the area undergoing the surgical procedure can help the surgeon avoid making an incision that is too deep (which may unnecessarily damage underlying tissue) or too shallow (which may result in an unsuccessful procedure and / or slow healing of the operated tissue).

[0080] As shown schematically in FIG. 1 , the interference signal output 146 of the spectrometer 136 of the OCT system 100 undergoes post-processing by an image processor 148. For example, the signal output 136 may be image processed using a Fourier transform or other suitable signal transform on the OCT scan. This may initially produce a distorted OCT scan image, which may 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.

[0081] The display 152 may be part of the device hosting the SD-OCT system 100 that performs the image processing, or it may be a separate device. Some exemplary embodiments of the disclosed technology use the OCT probe light beam to generate a series of OCT scan images 148 quickly enough to provide a live stream video containing the OCT scan images 150 on 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 with 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 may be external to it.

[0082] 1 that form the OCT scanning system 100 may be housed separately from the optics that form the OCT scanner device 164. By separating the OCT scanner optics, the OCT scanner 164 may have a more compact form factor. A more compact OCT scanner 164 may be better positioned closer to the sample area being scanned.

[0083] In some embodiments, the OCT scanner system 100 includes the OCT scanner 164 provided as an adapter for a microscope, such as an OCT scanner adapter 206 for the microscope 200 shown schematically in FIGS. 2A and 2B. In some embodiments, the microscope 200 includes a surgical microscope suitable for use during a surgical procedure. The housing 202 of the microscope 200, in some embodiments, includes a lower carriage configured to receive one or more microscope accessories, thereby allowing the OCT scanner adapter 206 to be attached to the lower carriage of the microscope housing. In this case, the OCT scanner adapter optics objective 114 can also function as the microscope objective 210 (see also FIGS. 3A, 3B, and 4 of the drawings).

[0084] Example of a microscope system with an OCT scanner adapter 2A and 2B show schematic front and back perspective views of an OCT scanner adapter 206 for a microscope, or in other words, an OCT scanner microscope accessory 206, in accordance with some embodiments of the disclosed technology. The term OCT scanner adapter is used herein to refer to an OCT scanner adapter microscope accessory. Reference to an OCT scanner adapter may also refer, in some embodiments of the disclosed technology, to a device that includes an integrated OCT scanner adapter.

[0085] 2A and 2B illustrate how the OCT scanner adapter 206 of FIGS. 3A, 3B, and 4 can be attached to the lower carriage of the microscope 200. For example, the microscope accessory OCT scanner adapter 206 can be retrofitted to the microscope 200 by removing any existing microscope accessories from the mounting points located on the microscope's lower carriage and using these microscope mounting points to instead mount the OCT adapter 206 to the lower carriage of the microscope 200. When 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, such as 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.

[0086] In some embodiments, the OCT scanner adapter 206 has a vertically compact form factor so that the additional height h2 added to the height h1 of the microscope to which it is attached during use is not excessive. Reducing the additional vertical height h1 of the OCT scanner adapter 206 improves ease of access to the scan region 116 during scanner use when generating cross-sectional images of the scan region 116 while the microscope is simultaneously being used. The OCT scanner adapter 206 is also laterally compact. This means that when attached to the microscope 200, it does not unduly obstruct surgical access to the region of tissue being scanned, allowing for simultaneous surgical procedures.

[0087] In the following description, height is referred to in the context of the OCT scanner adapter 206 being used to scan the tissue sample 116 from a position above the tissue sample, such as may occur when the OCT scanner adapter 206 is attached to the lower carriage of the surgical microscope 200.

[0088] Some embodiments of the OCT scanner 206 described herein retain a similarly compact form factor and can be used in other contexts. Furthermore, in some embodiments, the OCT scanner 206 may be integrated into another device, such as the microscope 200. In some embodiments, the OCT scanner 206 may be distributed as an optional accessory for such a device, so that it can be distributed and sold independently of the microscope to which it is subsequently attached. Thus, unless the context clearly prohibits it, references to height may equally apply to other dimensions of the OCT scanner that are substantially or nearly orthogonal to the plane of any device to which the OCT objective and OCT scanner are attached, and the orientation of the OCT scanner and microscope stack may also vary depending on one or more of the patient's orientation and the configuration of the microscope optics and the position of the eyepieces.

[0089] In other words, references to height in the context of an overall “height” are based solely on the assumed orientation of the OCT scanner and microscope relative to a supine patient when surgery is being performed on the patient. While the patient is supine, the surgeon can access the surgical target area beneath one embodiment of the OCT scanner adapter 206 according to the disclosed technology, while simultaneously physically accessing the eyepieces of the microscope 200 to which the OCT scanner 206 is attached. This geometric configuration can vary in some embodiments depending on the configuration of the microscope optics and / or the patient's orientation and / or the location of the surgical target area. Therefore, in the following description, references to the height and / or combined stack height of the microscope and OCT scanner adapter 206 can 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, as would be apparent to one skilled in the art.

[0090] 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 implemented by the OCT scanner adapter 206 for the microscope 200 includes the objective lens 114 of the OCT scanner system 100 shown schematically in FIG. 1. Accordingly, references to the objective lens 210 in the description can refer to the objective lens 114 of the OCT system 100, including different types of OCT scanners 164, unless the context clearly limits the reference to use of the OCT scanner as an adapter or accessory for a microscope.

[0091] In the exemplary embodiment of the OCT scanner adapter 206 shown in FIG. 2A, the OCT scanning optics design has a compact form factor that adds minimal additional height h2 to the height h1 of the microscope optics housing 202.

[0092] 2A and 2B also show microscope handles 204a,b, which aid in positioning the microscope 200 above the area to be scanned (and viewed). The OCT scanner adapter 206 includes a housing 208 secured to the lower carriage of the microscope 200 as shown. However, as noted above, in some embodiments, the OCT scanner adapter 206 may have different configurations and / or orientations during use. Such different configurations and / or orientations of the OCT scanner adapter 206 during use can also implement the compact principles of the OCT scanner design disclosed herein.

[0093] 2B shows a different rear view of the OCT scanner adapter 206 shown in FIG. 2A. The rear view shows a data and / or power port 212, such as an RSJ45 Ethernet port or a USB port, and an optical port 214. Port 212 provides power to the OCT scanner adapter 206 and, in some embodiments, may comprise a power-over-Ethernet port.

[0094] The OCT scanning light, in some embodiments, is returned from the OCT scanner adapter 206 via optical port 214 to the interferometry components of the OCT scanning system 100 as shown in FIG.

[0095] 1, the returning OCT light from the sample 116 returns through the objective lenses 210, 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 towards the sample being scanned form part of the probe arm 105 of the FD-OCT system 100.

[0096] The OCT light exits and illuminates the sample tissue 116 being scanned, and is then reflected, backscattered, or otherwise returned. The returning OCT light then passes back through coupler 104, where it interferes with light returned from reference arm 103. The returning OCT and reference beams then propagate along output arm 107 to spectrometer 136, which outputs an OCT and reference beam optical interference signal 136 for image processing to generate OCT imaging data 146 that is presented on display 152.

[0097] For example, in some embodiments of the disclosed technology, such as those shown in FIGS. 1, 2A, and 2B, the return OCT light is exported from the OCT scanner adapter 206 via optical port 214 to the coupler 104, through which it is passed to the spectrometer 136 of the spectral OCT system 100.

[0098] 2A and 2B, the OCT scanner housing 208, which includes the objective lens 210, adds a height h2 to the height h1 of the microscope 200. The additional stack height H2 introduced by attaching the OCT scanner adapter 206 to the microscope housing 202 is minimized by using an optical design of the OCT scanner optical components within the OCT scanner adapter 206 according to embodiments of the disclosed technology.

[0099] For example, some embodiments of the optical component design of the OCT scanner adapter 206 may have the optical design shown generally in Figures 3A, 3B, 4, 5A, and 5B, which lifts the OCT beam emerging from the scan mirror assembly 310 a minimal amount above the plane of the objective lens 114, 210 before the OCT emerges through the objective lens 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.

[0100] It should be understood that 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 aligned primarily with the XY horizontal plane. The OCT scanner system stack height h2 mounted under the carriage is also aligned with the Z axis. As a result, the total stack height h3 of the microscope body, which houses the microscope optics combined with the OCT scanner mounted under the carriage, is determined by h1 and h2. Preferably, the combined height h3 of h1 + h2 = h3 is short enough to allow the microscope to be positioned to allow operation by a user performing surgery on or through an area that includes the focal plane of the microscope objective lens 210 through which the OCT beam exiting the microscope passes. The OCT optical design, for example, in some embodiments, allows h2 to be minimized to 36 mm while still maintaining a preferred exit beam diameter of 10.6 mm and still having a stack height of 36 mm or less.

[0101] Therefore, by using an optical design for the scanning mirror assembly optics according to 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.

[0102] 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 to be operated on, but close enough to fit the physical form factor of a typical human. 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 a surgical procedure, while the microscope is optically focused onto a focal plane on the tissue sample using the microscope objective lens 210 of the OCT scanner adapter 206, through which the OCT probe beam is emitted onto the tissue sample.

[0103] 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) with a compact optical design that allows h2 to be minimized to 36 mm or less.

[0104] For example, in some embodiments, as described below with reference to Figures 3A, 3B, and 4, the OCT scanner adapter 206 includes an ultra-compact, large numerical aperture, microelectromechanical systems (MEMS)-based two-dimensional (2D) scanning mirror assembly 310, which uses a point light source 158 to determine the position of a reflective mirror surface 334 in its optical design using a position-sensing detector 160.

[0105] Some embodiments of OCT scanner assemblies using the PSD 160 can support very fast scan rates, e.g., 36,000 A-scans per second or more, where an A-scan is a depth scan at a given point within tissue. Each B-scan is formed from multiple adjacent A-scans, which can be used to generate an image with depth information about the region being scanned in the form of a slice through the sample being scanned, showing structures at different depths along the slice. In other words, a B-scan provides information about z- or depth-directed structures along a single linear cross-section of the tissue sample, e.g., a linear scan along a line definable in x- and y-coordinates, as shown schematically in FIG. 1. Some embodiments of the OCT assembly enable very high-resolution images, e.g., 400 B-scans per second, to be generated in real time across the entire field of view (FoV) being scanned, which may be, for example, a 20 mm x 20 mm area or larger. By taking a series of B-scans sufficiently quickly and close to each other across the sample, a three-dimensional volumetric or composite scan can then be formed from the area being scanned and presented on the display 152.

[0106] The embodiment of the scanning mirror assembly, shown as optical block 310 in Figures 3A-3B, 4, and 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.

[0107] Some embodiments of the optical design of the scanning mirror assembly specify one or both of a minimum and a maximum exit beam diameter of one or more optical components. For example, the beam diameter of the OCT beam input via optical fiber 308A preferably exceeds a threshold diameter of 3.1 mm when exiting the collimating lens assembly 516, shown in FIG. 6 as collimating lens 602, 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, and has a wavefront error of less than (approximately) ½ wave (rms).

[0108] Another exit beam diameter that can be selected is the beam diameter of the OCT beam 312 exiting the focusing lens assembly 314 of the OCT scanner adapter 206 and then incident on the folding mirror 316. The focusing lens 314 expands the OCT scan or probe beam diameter to 10.6 mm, setting the OCT system numerical aperture and ultimately the resolution for the OCT scanner system based on 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, or better than 33 line pairs per millimeter. This can be contrasted with a resolution of 6 microns, 166 line pairs / mm, at the intermediate image plane located at the exit of the OCT objective lens assemblies 510 and 512.

[0109] In some embodiments, the maximum FoV that a user can set for a scan is a 20 mm x 20 mm area using a suitable user interface, for example, a user interface of a device implementing image processing system 148 shown in Figure 1 that includes or is connected to display 152. In some embodiments, the user interface is configured to allow a user to adjust the position of the OCT scan FoV within the 25 mm box, while still allowing the total FoV of the OCT scan image to remain a 20 mm x 20 mm area.

[0110] Embodiments of the disclosed technology used in surgical procedures and other applications requiring real-time imaging can use the high dispersion configuration of the OCT system 100 with the OCT scanning adapter 206.

[0111] The term real-time, as used herein, refers to a small processing delay, for example, 60 ms or less, and in some embodiments, a delay of about 30 ms or less is achievable. The design incorporates a high angle of incidence at the scanning mirror to reduce compound angle coupling when performing 2D scanning of the sample with both high lateral optical resolution and a telecentric image plane.

[0112] The following description of the optical design of the scan mirror assembly 310 shown in Figures 3A, 3B, 4, and 5A incorporates a high angle of incidence at the scan mirror reflective surface 334 to reduce compound angle coupling when performing a 2D scan of a sample, allowing OCT scans to be performed with both high lateral optical resolution and a telecentric image plane. Each OCT scan includes multiple one-dimensional scans, A-scans, which provide depth information at points within the area being scanned (e.g., of a sample). Several A-scans are stacked together to create a two-dimensional image, referred to herein as a B-scan. A B-scan provides a slice through the scanned area, showing depth information along the path of the A-scan. Multiple B-scans traversing the scanned area can provide a three-dimensional volumetric scan of the scanned area.

[0113] The scanning mirror assembly 310 includes a movable reflective surface 334 equipped with a microelectromechanical system having a suitable large numerical aperture. The term "large numerical aperture" herein refers to the effective aperture diameter of the reflective surface 334, which is preferably greater than about 4 mm in diameter. The term "effective aperture diameter" refers to the range of angles that can be imaged through the aperture without the need for supports, clips, or other forms of retention elements to get in the way. The larger the diameter of the effective aperture diameter of the scanning mirror reflective surface 334, the slower the scan rate because the probe beam covers a larger diameter. MEMS mirrors with effective aperture diameters of about 7 mm are already known in the art, but even with optical feedback, these known MEMS mirrors with large effective aperture diameters cannot scan at a speed acceptable for real-time imaging applications, such as those required for OCT when performing 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 scanning mirror assembly is used, which allows scanning to be performed fast enough for the SD-OCT system shown in FIG. 1 to be used for real-time surgical applications.

[0114] In OCT, axial and lateral properties are separated. The lateral resolution is defined by the objective lens and focusing medium in front of the sample. The axial properties of interferometry are defined by the coherence properties of the OCT scanning light source and how the returning OCT signal is sampled at the detector after returning from the sample. The OCT axial resolution depends on the spectral bandwidth and central wavelength of the OCT scanning light source. The 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 scanned depth.

[0115] An A-scan is an amplitude depth scan along one dimension through the sample, usually referred to as the z-axis, and a B-scan is a two-dimensional lateral scan across the sample formed by a series of A-scans. In other words, for each sample point, the spectrally dependent interference fringe pattern produced by backreflections from the OCT interferometer's reference mirror and backreflections from the sample is recorded as an A-scan. Multiple A-scans are taken to generate other scans, such as B-scans, which allow a complete depth profile of the sample reflectivity at the beam position to be generated.

[0116] In some embodiments, the aperture diameter is 4.2 mm or greater.

[0117] In some embodiments, the OCT scanner adapter 206 includes a high-speed OCT MEMS-based mirror scanning assembly 310 that uses the position-sensing detector system 160 to implement a control loop feedback for controlling the positioning of the OCT beam during scanning. The control loop feedback has a technical advantage in that it allows the OCT scanner to generate more B-scans per second of an object of interest being scanned. In other words, the control feedback loop implemented in some embodiments of the disclosed technology allows for suppression of ringing and resonant behavior caused by step changes in drive voltage at the ends of a scan line.

[0118] OCT Microscope Adapter Design Example FIG. 3A schematically illustrates an exemplary embodiment of a MEMS microscope OCT scanner adapter 206 according to the disclosed technology suitable for mounting on the lower carriage of the microscope 200 shown in FIGS. 2A and 2B, as the adapter is constructed with optical components that seek to optimally reduce the lateral and vertical footprint while maintaining optical quality characteristics suitable for OCT applications.

[0119] 3A, the illustrated exemplary embodiment of an OCT scanner adapter 206 comprises multiple components housed within or mounted on an adapter housing 208. The adapter housing 208 comprises a data / power port 212, such as an Ethernet Power over Ethernet port or a high-speed USB port.

[0120] An optical port 214 is also provided for inputting and outputting OCT scanning light to and from the OCT scanner adapter 206. An optical fiber 308a connected to the optical port 214 supplies OCT light from the coupler 104 shown in FIG. 1 to the scanning mirror assembly optical block 310 shown in FIG. 3A via the optical fiber connector 308. The returning OCT light returns along the coupler 104 shown in FIG. 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 FIG. 1, through which the OCT probe light illuminates the scanned sample and through which the returned OCT light from the sample is output toward the coupler 104 of the OCT scanning system 100 shown in FIG. 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 a single mode.

[0121] 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 of Figure 1, of which optical fiber 308a forms a part. The OCT light following 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 (see Figure 5A) of the MEMS scanning mirror assembly 310.

[0122] In some embodiments, the fiber optic connector 308 through which the OCT light is input to the MEMS mirror block 310 is a fiber connector to angle polished connector.

[0123] The optical block housing MEMS scan mirror assembly 310 also houses the optical components of an optical angular displacement mirror position measurement system 156 for the scan mirror assembly, shown in FIG. 1 as mirror position measurement system 156. A controller 162 (see FIG. 1, not shown in FIG. 3A) is used to adjust the reflective surface 334 of scan mirror 112 shown in FIG. 1 using a mirror movement mechanism (not shown) of MEMS scan mirror assembly 310. Controller 164 may be implemented within OCT scanner adapter 206 or may be remotely located, in which case control signals may be passed to the mirror movement in MEMS scan mirror assembly 310 via data port 212 of OCT scanner adapter 206.

[0124] In some embodiments, the same mirror reflective surface 334 in the scanning mirror assembly housed in the optical block 310 reflects both the input OCT beam and a mirror positioning reference beam from a different light source (see FIG. 5A, described in more detail below). However, as will be apparent to those skilled in the art, other embodiments may 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.

[0125] OCT light following optical path 105 a received via OCT data connection fiber 308 is reflected from an optical surface of reflective surface 334 that is different from the optical surface from which light from the light source of angular-displacement mirror measurement system 156 is reflected.

[0126] The reflected OCT beam then follows an optical path through the OCT scanner adapter 206, from where it emerges through a microscope objective 210 to probe an object of interest, for example a tissue sample such as in vivo eye tissue as shown schematically in Figure 1. Other types of objects of interest may range from tissue samples for fields such as ophthalmology and dermatology, dentistry, angiography, cardiology, and other tissue samples for the diagnosis of diseases including cancer.

[0127] OCT light reflected, backscattered, or otherwise returned from structures within the tissue sample then returns through the scanning mirror assembly of the optics block 310 and follows a return path 105a along optical fiber 308a. The returned OCT light then exits the OCT scanner adapter 206 via optical port 214 and is provided to the OCT system 100, where it combines and interferes with light returned from the reference arm 103 at coupler 104. The resulting interference pattern is detected in the OCT system 100 of FIG. 1 by the spectrometer 136, which generates image data that can then be image processed to obtain a tomographic image showing the scanned structures within the tissue located within the scanning FoV.

[0128] In the exemplary embodiment of the OCT adapter 206 shown in FIG. 3A , the OCT probe beam 312 exits an optical block housing a MEMS OCT scanning mirror assembly 310 and travels toward a fold mirror 316, which lifts the OCT beam a minimal amount off its optical surface toward a beam splitter 318. The beam splitter 318 reflects the incident OCT beam toward the OCT scanner adapter 206's objective lens assembly 210, which also functions as the objective lens for the microscope optics housed in the microscope 200 when the OCT scanner adapter 206 is attached to the microscope 200. The OCT probe beam emerges from the objective lens 210 as a telecentric beam focused onto a focal plane 154 within the tissue being scanned, which lies in the xy plane shown schematically in FIG. 1 . The resulting returned OCT light can be used to generate an OCT A-scan that provides depth information orthogonal to the focal plane 154, or in other words, in the z direction shown in FIG. 1 . Movement of the reflective mirror surface 334 moves the position of the telecentric beam across the focal plane 154 within the region 116 being scanned, allowing an OCT B-scan image to be generated.

[0129] 3A, the OCT scanner adapter 206 is configured such that the objective lens 210 can be used as an objective lens by the microscope optics and the OCT scanner system 100. A light-tight gasket 320 is provided around an opening 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 optics of the microscope 200.

[0130] The configuration of the fold mirror 316, beam splitter 318, and objective lens assembly 210 of the OCT scanner adapter 206 is collectively designed to lift a small amount above the plane in which the OCT beam follows through the scanning mirror assembly so that it can exit through the objective lens 210. The amount of lift required is affected by the tilt angles of the beam splitter and fold mirror, as well as the beam entrance geometry. Therefore, the additional height h2 that the OCT scanner adapter 206 adds to the microscope height is also minimized 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. In some embodiments, this can be achieved with a lift of 27 mm or approximately 27 mm using suitable tilt angles for the beam splitter and fold mirror.

[0131] In some embodiments, as shown in the exemplary embodiment of FIG. 3A , the OCT probe beam 312 exits an optical block housing a scanning mirror assembly and travels through free space first to a focusing lens assembly 314, which allows the focal plane of the image being scanned to be adjusted. This adjusts the focus of the scan at different depths. The focusing lens assembly 314 is driven by a motor 326 and further includes a travel limiter or stop 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 within 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 best SNR during initial image acquisition. This is different from, and should not be confused with, the technique of shifting the focus at the A-scan rate, which is used to extend the depth of focus within the sample. The focusing lens assembly 314 moves slower than required for A-scan sampling and will not adjust without user intervention unless the system detects significant sample movement.

[0132] 3A , the OCT scanner adapter 206 is attached to the microscope 200 using fasteners, e.g., screws, which may be provided in recesses in the mounts 328a and 328b and extend from the mounts 328a and 328b into corresponding receiving openings or holes, preferably threaded holes, in the lower carriage of the microscope 200 to securely engage the OCT scanner adapter 206 to the microscope. In some embodiments in which the OCT scanner adapter 206 functions as a microscope accessory, the OCT scanner adapter 206 may also include a receiving opening or hole at its base that corresponds to the location of the receiving hole or holes in the lower carriage of the microscope 200. By having the same or similar fixing positions in the base of the OCT scanner adapter microscope accessory 206 as the fixing positions in the microscope lower carriage, a different type of microscope accessory that would otherwise be attached to the lower carriage of the microscope 200 can instead be attached to the lower carriage of the OCT adapter. In other words, in some embodiments, the OCT scanner adapter 206 is configured to be mounted to the lower carriage of a microscope as a microscope optics accessory. Some embodiments of the OCT scanner adapter microscope accessory 206 allow the OCT scanner adapter accessory 206 to have another microscope accessory mounted to the base of the OCT scanner adapter.

[0133] Figure 3B shows an alternative view of the OCT scanner adapter 206 of Figure 3A. However, in Figure 3B, the location of the source or emitter 158 of the mirror-positioning light beam 400 shown in Figure 4 that illuminates the scanning mirror is more visible, as is the location of the position-sensing detector (PSD) 160 of the optical angular displacement measurement system 156 within the optics block 310.

[0134] Also shown schematically in FIG. 3B is an exemplary angle of incidence θ of the mirror-positioning illumination beam 400 shown in FIG. 4 at the reflective surface 334 of the MEMS scanning mirror, which, after reflection, forms a mirror-positioning reference beam that travels toward the PSD 160.

[0135] It will be understood that the angles of incidence and positions of beam paths shown in the figures are for illustrative purposes only and are not to scale.

[0136] The MEMS scanning mirror assembly design is configured so that illumination mirror positioning light beam 400, shown in Figure 4, is reflected by the scanning mirror's reflective surface 334 at a different optical surface to form reference beam 402 that passes along the positioning reference arm of OCT scanning mirror assembly 310 from the optical surface where the same reflective surface 334 reflects incident OCT scan or probe beam 312, shown in Figures 4 and 5A. The scanning mirror assembly is also configured so that the returning positioning light is reflected by the mirror at another optical surface that is different from the optical surfaces of reflection of the OCT outgoing and returning beams and different from the optical surface where the incident mirror positioning beam is reflected, resulting in minimal interference with either the OCT beam or the source of the incident mirror positioning beam or mirror positioning beam.

[0137] Figure 4 of the accompanying drawings schematically illustrates an expanded view of the OCT scanner adapter 206 of Figures 3A and 3B. In Figure 4, a mirror-position illumination beam 400 (shown in dash-dot lines) from a point source 158 is incident on the reflective surface 334 of the OCT scanning mirror 500 shown in Figure 5A at an angle of incidence AOI indicated as θ. A mirror-position reflected beam 402 (shown in dash-dot lines in Figure 4) is reflected toward and detected by the PSD 160. For clarity, the return light from the incident beam at the PSD 160 is not shown in Figure 4.

[0138] The OCT scanner optical components shown in Figures 3A-4 are positioned so that the OCT light emerging from the optical surface of the scan mirror assembly is lifted a small amount from that surface by a fold mirror 316 toward a beam splitter 318. The beam splitter 318 reflects the OCT probe beam into the same focal plane 154 as the microscope light while allowing the light to transmit through the microscope optics and back into the microscope optics. By optimally positioning the beam splitter and fold mirror relative to the objective lens 210, it is possible to reduce the height the OCT probe beam must be lifted by the fold mirror before being reflected by the beam splitter 318 and exiting through the objective lens 210.

[0139] In some embodiments, the fold mirror lifts the OCT beam 27 mm from the optical surface of the scanning mirror assembly.

[0140] Scanning mirror assembly optical design example FIG. 5A of the accompanying drawings illustrates schematically an example of an optical design for a two-dimensional (2D) scanning mirror assembly, such as the 2D scanning mirror assembly housed within the optical block 310 shown in FIGS. 3A, 3B, and 4.

[0141] The optical design of the 2D scanning mirror assembly is suitable for use in other types of OCT scanners, such as OCT scanner 164 and OCT scanner adapter 206 of Figure 1. The scanning mirror assembly 310 shown in Figure 5A has an optical design that can be used for applications other than OCT that use scanning light that require mirror positioning.

[0142] In other words, the optical design of the 2D scanning mirror assembly of Figure 5A, in all of its embodiments, need not be limited to OCT applications or devices such as those shown in Figures 1-4 of the accompanying drawings, but may be beneficially implemented in any other type of optical scanning device where a compact lateral optical surface is beneficial.

[0143] Some exemplary embodiments of the microelectromechanical systems (MEMS) two-dimensional scanning mirror assembly 310 shown in FIG. 5A have an optical design including a movable MEMS scanning mirror having a reflective surface 334, a connector 308 to a point source of light for the scanning light beam, and, for example, an optical fiber 308a connected via an optical fiber connector 308 as shown, with the end of the optical fiber 308a (see FIG. 5b) serving as the point source of light for the light beam.

[0144] The scan mirror assembly optics also includes a collimating lens assembly 516 for light introduced via connector 308. Collimating lens assembly 516 is configured to output light from the point source with an exit beam diameter greater than a threshold exit beam diameter toward a reflective surface suitable for the desired scanning application. After reflecting off reflective surface 334 of scan mirror 112, the scanned light beam passes through objective lens assemblies 510, 512 and exits the scan mirror assembly.

[0145] The reflective surface 334 is configured to reflect the incident collimated light beam to form a scanning beam, e.g., an OCT probe beam if a point light source provides the OCT light, which exits the mirror assembly as a telecentric beam 312 via an objective lens 510 and a field lens 512 (also collectively referred to as the objective lens assembly 510, 512) toward a telecentric image plane 154. The optical design of the components in the scanning mirror assembly is configured to ensure that the scanning beam can perform a scan with a resolution better than a resolution threshold.

[0146] The optics of the scanning mirror assembly are configured to achieve a total track length L of the path from the point source, e.g., from the end face of an optical fiber or fiber ferrule (see also FIG. 5B ), to the telecentric image plane (700) of less than about 40 mm, helping to keep the lateral dimension X of the scanning mirror assembly small enough to allow the OCT scanner housing 308 to fall below the desired lateral footprint in its design. For example, as shown in FIG. 5 , the width X of the scanning mirror assembly is preferably less than 41 mm, and may, for example, be 40.6 mm or less in some embodiments. The optical design is also configured to keep the depth Y, as shown in FIG. 5A , as small as possible; for example, Y may be 35 mm or less, and in some optical designs, as short as 34.5 mm or less.

[0147] Thus, the total track length L is kept as short in some embodiments as the optical design layout allows for reducing the lateral footprint X and depth footprint Y to the smallest possible size, so that the housing of the scanner including the scanning mirror assembly 310 can have a similarly small footprint.

[0148] Keeping the lateral footprint X as small as possible improves side access to the area being scanned, which is particularly beneficial when the scanning mirror assembly 310 is a scanning mirror assembly for the surgical microscope accessory OCT scanner adapter 206, as it may improve access to the area being operated on while the microscope to which the scanning mirror assembly is attached is in use.

[0149] In some embodiments of the scanning mirror assembly, the threshold exit beam diameter from 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 a smaller exit beam diameter would allow.

[0150] In some embodiments of the scanning mirror assembly, the telecentric beam resolution threshold at the telecentric image plane 700 is better than 6 microns. In other words, the scanned image can resolve features of the sample being scanned that are smaller than 6 microns.

[0151] In some embodiments, the scanning mirror 112 may be moved, for example, by the controller 162. The scanning mirror assembly, in some embodiments, may be configured to move about its optical axis and, in some embodiments, scan over + / - 5 degrees.

[0152] In some embodiments of the scanning mirror assembly, the numerical aperture of the optical fiber and the focal length of the collimating lens together determine a preferred threshold exit beam diameter of at least 3.1 mm for the collimated beam from the collimating lens to achieve the designed resolution at the focal plane. The focal length of the scanning mirror objective lens, in combination with the focal length of the scanning mirror field lens through which the probe beam exits the mirror assembly, determines the total track length L, which is preferably less than or near 40 mm.

[0153] In some embodiments, for example, when the scanning mirror assembly is being used for OCT purposes, the optical fiber has a numerical aperture of 0.14. In other embodiments of the scanning mirror assembly, the optical fiber that supplies light to the scanning mirror assembly by acting as a point light source can have other suitable numerical aperture values ​​that provide a numerical aperture that allows sufficient light to be supplied to the scanning mirror assembly for other use cases along the single mode optical fiber 308a.

[0154] 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.

[0155] 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.

[0156] In some embodiments of the scanning mirror assembly, the telecentric beam is telecentric at the telecentric image plane to better than a 0.03 degree angle of incidence.

[0157] In some embodiments of the MEMS scanning mirror assembly, the reflective surface 334 of the MEMS scanning mirror comprises a large diameter gold coated silicon mirror bonded to an underlying mechanical structure.

[0158] An embodiment of the design of the scanning mirror assembly 310 shown schematically in Figure 5A may be implemented as an optical block in 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 in a compact OCT scanner adapter for microscope 206, such as the optical block that houses the scanning mirror assembly 310 shown in Figures 3A, 3B, and 4.

[0159] However, as noted 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 scenarios in other types of scanner systems. In some embodiments, the mirror assembly shown in Figures 5A and 5B is implemented as a scanning mirror assembly for an OCT device, such as those shown in Figures 3A-3B, and receives light launched by optical fiber 308a. In other embodiments, a different point light source may be used in place of optical fiber 308a, which serves as a point source for the OCT light beam, as shown in Figures 3A, 3B, 4, 5A, and 5B.

[0160] In some embodiments, the mirror assembly 310 may be provided within an OCT scanner adapter 206 that is used as an OCT scanning accessory for the microscope 200. In some embodiments, the microscope may comprise a surgical microscope, and the scanning mirror assembly 310 may be used to generate OCT scans of a sample tissue region being operated on at a rate high enough to allow live OCT tomography of the sample tissue region to be generated while the surgical procedure is in progress.

[0161] In some embodiments, the SD-OCT scanning system shown in FIG. 1 includes an OCT scanner adapter 206 having a scanning mirror assembly 112, 310 having an optical design as shown in FIGS. 5A and 5B and described herein.

[0162] In some embodiments, the scanning mirror assembly 310 is configured so that the OCT light returned from the sample along the OCT probe arm 105 has a lateral optical resolution of 6 μm or better, in other words, a resolution of better than 166 line pairs per mm.

[0163] 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 the OCT light from the point source toward the reflective surface 334 with an exit beam diameter of at least 3.1 mm. The reflective surface 334 is configured to reflect both the incident collimated OCT light beam to form the OCT probe beam and a mirror positioning reference beam. The OCT probe exits the mirror assembly as a telecentric beam toward a telecentric image plane with a resolution of at most 6 microns. The optics of the scanning mirror assembly 310 are configured to achieve a total track length L from a) the end face of the fiber ferrule inserting into the optical fiber connector, which realizes the point source, to the telecentric image plane, which in some embodiments is less than 40 mm, preferably less than 36 mm. An objective lens assembly 510, 512 is provided in the probe arm of the scanning mirror assembly in some embodiments to focus the telecentric OCT beam through the OCT scanner (microscope) lens 114, 210.

[0164] The scanning mirror assembly 310 has an optical design that includes a MEMS mirror reflective surface 334 configured so that an incident mirror positioning beam is reflected off an optical surface separate from the optical surface at which the incident OCT scanning beam is reflected. In this manner, the scanning mirror assembly can also be used with a mirror positioning system, such as the angle tilt mirror positioning system shown schematically in Figure 1 of the drawings.

[0165] As mentioned above, some embodiments of the MEMS-based scanning mirror assembly shown in Figures 5A and 5B and described herein are implemented in an OCT scanner 206 such as shown in Figures 3A, 3B, and 4 as part of the SD-OCT scanning system shown in Figure 1. Accordingly, some embodiments of the disclosed technology comprise an OCT scanner system 100 that includes an OCT scanner 206 that includes a microelectromechanical systems (MEMS) two-dimensional scanning mirror assembly 310 having a compact optical design in accordance with the disclosed technology.

[0166] In some embodiments of the MEMS scanning mirror assembly 310, the scanning mirror 112 is mounted to an underlying mechanical structure or support 500 that provides a mirror movement mechanism that allows the mirror surface 334 to pivot about its optical axis under the control of the controller 162, as shown in FIG. 5A.

[0167] In some embodiments, the reflective surface 334 of the MEMS scanning mirror assembly comprises a large diameter gold coated silicon mirror bonded to the underlying mechanical structure 500 .

[0168] 1 is implemented in the MEMS mirror assembly embodiment of FIG. 5A by a light source 158 comprising a suitable point light source, for example, a laser diode 502. The point light source generates a light beam, referred to herein as mirror-positioning light beam 400 (shown in dashed line in FIG. 5A), that passes through a collimating lens 503 such that the collimated mirror-positioning beam 400 is incident on the scanning mirror surface 334 at an incident angle θ.

[0169] Angular displacement measurement system 156 is used to determine the angular position of MEMS scanning mirror assembly 310 relative to incident mirror positioning beam 400, so that when performing a scan, the mirror position of the incident light beam can be determined and adjusted as the scan progresses. OCT scanning (e.g., B-scan or volumetric scan) is performed by moving the mirror using controller 164 according to any scanning parameters for the particular scan configuration (which in some embodiments can be input by a user and / or automatically determined for a particular type of scan).

[0170] The position of the movable MEMS mirror surface 334 may, in some embodiments, be controlled using a suitable angular position controller (not shown in FIG. 5A) that uses closed-loop control based on feedback from a position-sensing detector 160 that detects the reflected mirror-positioning beam 402.

[0171] In some embodiments, the scanning mirror assembly 310 described above with reference to FIGS. 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 as a scan is performed. However, in some embodiments of the compact OCT scanning mirror assembly 310 of the figures, 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 with other system components of the OCT scanner system 100 or hosted on a different platform having a user interface that allows for input of scanning parameters. Control signals may, in some embodiments, be transmitted from the remote controller 162 via a suitable data connection, such as a data port, such as 212.

[0172] 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 angle of incidence θ of greater than 62 degrees, preferably 67.5 degrees, from the normal to the plane of the reflective mirror surface 334.

[0173] In some embodiments, the OCT light source illuminates the reflective surface of the mirror assembly of the OCT light channel at an angle of incidence θ of less than 28 degrees, preferably 22.5 degrees, from the normal to the plane of the reflective mirror surface 334 .

[0174] In some embodiments, the minimum usable aperture at 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 in surgical applications.

[0175] In some embodiments of the disclosed technology, the OCT device can use closed-loop feedback to control the scanning mirror position in some embodiments. The use of closed-loop feedback can be useful in embodiments where high scan rates are required, such as when live video or other forms of OCT scan image sequences are required. The use of closed-loop feedback allows the mirror to be moved quickly and accurately enough to achieve high scan rates and / or high scan resolution (i.e., high OCT image B-scan or volumetric scan resolution), thereby supporting low-latency, rapidly generated OCT scans for time-sensitive applications, such as when OCT scans are implemented to guide surgical procedures. However, in some embodiments, open-loop control may be provided.

[0176] The disclosed technology attempts to address at least some of the design constraints that exist when designing an OCT system for a surgical microscope. For example, one design constraint is that a smaller diameter scanning mirror surface is more suitable for achieving higher scan rates. The numerical aperture is related to resolution. The effective aperture diameter, i.e., mirror diameter, is related to the scan size insofar as the underlying mechanical structure of the MEMS is the same. Thus, a smaller diameter mirror, such as a 2 mm diameter, can tilt further (up to + / - 7 degrees) before hitting the MEMS base, while a larger diameter mirror, such as a 7.5 mm diameter, can only tilt + / - 1.5 degrees before hitting the base. This means that a smaller diameter mirror can be used to scan a larger area, but this comes at the expense of resolution.

[0177] In some embodiments, the threshold 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.

[0178] 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 the first optical plane towards a position sensing detector (160) configured to generate information regarding the tilt angle of the scanning mirror reflective surface (334).

[0179] 5, mirror-positioning light from light source 158 is first collimated by a suitable collimating lens assembly 503 to form a collimated illumination light beam 400 that is incident on reflective mirror surface 334. Collimated illumination light beam 400 (schematically represented by a short dash-dot line in FIGS. 3B, 4, and 5A) then impinges on reflective MEMS mirror surface 334 at AOI=θ and is reflected to form a mirror-position reference beam 402 (shown by a longer dash-dot line in FIGS. 3B, 4, and 5A), which travels along the mirror-positioning reference arm 501 of the scanning mirror assembly, through PSD lens assembly 504, and in some embodiments, through optional neutral density filter 506, toward PSD 160.

[0180] However, the mirror positioning beam 400 may be reflected or otherwise returned by the PSD 160 toward the reflective surface 334 of the MEMS mirror (the reflected beam is not shown in FIG. 5A ). This is undesirable because such returned light may contaminate the illumination positioning beam and / or the input OCT light beam. Other issues with stray light reflectivity in mirror position detector systems include erroneous detected spot positions when there is stray light on the PSD 160, and the diode behavior may change if reflected light enters the diode cavity, which may cause intensity fluctuations in the position detector beam that the PSD detects as a change in position.

[0181] To prevent the returning reflected component 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, suitably configured and positioned to reduce any reflected mirror positioning reference beam light from re-entering the emitter for the mirror positioning beam and / or contaminating the returning probe beam 312 before reaching the interferometer.

[0182] As mentioned above, some embodiments of the MEMS-based scanning mirror assembly shown in Figures 5A and 5B have reflective surfaces designed so that the OCT light input via the OCT optical coupler 308 is reflected from different areas of the MEMS mirror surface 334, where the mirror positioning reference beam 402 and the OCT scanning or probe beam are reflected from different optical surfaces.

[0183] After reflection by the MEMS mirror surface 334 of the scan mirror assembly 310, the OCT scan or probe beam passes along an 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 fold mirror 316. As shown in the embodiment of FIGS. 3A and 3B and 4, the beam passes through a focusing lens assembly 314 before entering the fold mirror 318, which lifts the beam off the optical surface of the scan mirror assembly. In some embodiments, this allows the OCT focal plane to be focused within a range of + / - 30 mm, or in other words, different depth ranges to be focused on the scan region. However, the focusing lens optics may be omitted in some embodiments of the OCT scanner.

[0184] The fold mirror 316 lifts the incident OCT scan (or probe) beam out of the plane of its optical path through the scan mirror assembly by reflecting it toward the beam splitter 318. The beam splitter reflects the OCT scan or probe beam from the microscope objective 210 of the OCT scanner adapter 206 toward the focal plane 154 for scanning tissue or similar objects of interest, which may be an in vivo tissue sample or an in vitro sample. The beam splitter 318 also allows the OCT illumination area being scanned to be viewed through microscope optics housed within the microscope 200.

[0185] 3A and 3B, the OCT probe beam 312 is input to the optical block by traveling along optical path 105a in optical fiber 308a and enters the scan mirror optical block 310 via the OCT data connection fiber input 308. The OCT scan or probe beam 520 then passes through a collimating lens 516 toward the scan mirror reflective surface 334. The mirror surface 334 reflects the OCT beam from the optical block containing the scan mirror assembly 310 via the probe arm 508, at which point the OCT beam travels in free space toward the fold mirror 316.

[0186] As shown in the OCT adapter embodiments shown in Figures 3A and 3B and 4, the OCT scan or probe beam 312 is focused by passing through a focusing lens assembly 314 before reaching a folding mirror 316. The focusing lens assembly is driven by a motor 336 that adjusts the position of the focusing optics to allow a range of focal depths to be achieved when performing a scan. In some embodiments, the focal range can vary from + / - 30 mm.

[0187] The returning OCT light is reflected via the MEMS scanning mirror surface 334 along the OCT arm 518 of the scanning mirror assembly 310 towards the coupler of the OCT system 100 shown in FIG.

[0188] In the scanning mirror assembly 310, the input OCT light beam enters the scanning mirror assembly 310 through the end face 532 of the optical fiber 308a via the optical fiber connector 308, passes through the optical fiber ferrule 530 (see also FIG. 5B), and passes through the OCT collimating lens 516 to the scanning mirror assembly. The track length, i.e., the measurable physical distance of the path from the end face 532 to the surface of the scanning mirror, is shown in FIGS. 5A and 5B as L1.

[0189] 5A also shows the track length L2 from the scan mirror plane to the telecentric image plane 700. The total track length L=L1 and L2 is preferably less than or equal to the track length design threshold of 40 mm.

[0190] Figure 5B is an expanded view of Figure 5A that more clearly shows the location of the fiber optic ferrule 532 and fiber optic end face 530 through which the optical fiber 308a, acting as a point source, launches the OCT light into the mirror scanning system 310. The OCT light travels from the fiber end face 532 to a collimating lens 516, and the collimated illuminating OCT beam then strikes 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.

[0191] In the return direction, which is not shown in Figures 5A or 5B for clarity, the returning OCT light travels in the other direction along OCT arm 518 (see also the description of Figure 6), through collimating lens 516, then along optical fiber 308a via OCT data connection fiber 308, and then leaves the OCT scanner adapter 206 via optical port 214.

[0192] In some embodiments, the OCT scanner is implemented using off-the-shelf (OTS) MEMS (micro-electromechanical systems), with the MEMS scanning mirror reflective surface 334 provided by a large aperture protective gold coated silicon mirror bonded to the underlying mechanical structure 500 of the optics 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.

[0193] 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 measurement system 156 for measuring the position of the MEMS mirror system.

[0194] The mirror positioning system that measures the angular displacement of the scanning mirror reflective surface 334 includes a mirror positioning light source 158 and a position sensitive detector (PSD) 160. The PSD, like the PSD 160, may include a PSD lens assembly 504 and a neutral density filter 506. An example of a suitable PSD detector is a Hamamatsu S5991 4 mm x 4 mm active area position sensitive detector.

[0195] In some embodiments, the angular optical displacement measurement system 156 is provided in the same optical block as the MEMS scan mirror assembly 310. The optical angular displacement measurement system 156 is used in some embodiments to achieve closed-loop control of the MEMS scan mirror position. Closed-loop control can be achieved by using the PSD 160 to measure the angle of incidence θ and providing information indicative of the mirror position derived therefrom to a controller, which can then more precisely control the tilt angle of the scan mirror reflective surface 334 as a scan is performed.

[0196] This closed-loop feedback can enable very high B-scan rates to be performed. For example, using closed-loop control of a 4.2 mm diameter effective aperture mirror 112, a maximum scan rate of at least 400 B-scans per second can be achieved at all angular deflections for the maximum field of view (FoV).

[0197] In embodiments without closed-loop control, i.e., open-loop scanning, a low-pass filter can be used to prevent the MEMS scanning mirror movement device from reaching a natural frequency excitation condition that could cause the MEMS scanning mirror movement device to resonate due to uncontrolled vibrations (which could damage the MEMS scanning mirror movement device). In embodiments where open-loop scanning is implemented, the maximum scan rate can be approximately 50 B-scans per second, which can be compared to rates achievable with closed-loop control. With closed-loop control in some embodiments, scan rates achievable using exemplary embodiments of the MEMS scanning mirror assembly 310 according to the disclosed technology are approximately 400 Hz or greater.

[0198] 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 210. In other words, in some embodiments, the MEMS scanning mirror system components are appropriately configured to enable the diameter of the collimated OCT beam 312 output along the OCT data connection fiber 308 to match the desired minimum system optical resolution after passing through the microscope objective 210.

[0199] In some embodiments, all air-to-glass interfaces within the OCT scanner adapter 206 are designed with convex surfaces to minimize back reflections from the OCT beam as it propagates through the optical system.

[0200] FIG. 6 illustrates 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 in the OCT arm 518 of the optical block including the scan mirror assembly 310 shown in FIG. 5 of the drawings. The OCT collimator lens 516 is provided along the OCT arm 518 of the scan mirror assembly optical block 310. In FIG. 6, OCT light fed into the collimating lens assembly 602 via the optical fiber ferrule end 532 emerges 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 and is reflected from the scan mirror reflective surface 334. The returning OCT light traverses the reverse path through the scan mirror assembly and is focused, via the collimated beam, toward the end of the optical fiber 308a that collects the returned light. The returning OCT light can then propagate back toward the coupler 104 of an interferometer system, such as the OCT system 100 shown in FIG. 1.

[0201] A suitable example of an OCT collimator lens 516 that can be used in some embodiments of the disclosed technology is an F3.2 biconvex doublet lens. Such a lens has a thick crown glass section that reduces the radius of curvature of the lens surface, resulting in improved color performance. In some exemplary embodiments, the collimator lens has a 10 mm focal length with a 100 micron depth of focus, which allows for good mechanical focus stability. In some embodiments, the OCT collimator lens achieves an output beam with a 3.1 mm diameter collimated beam (exit pupil diameter) with a wavefront error of <1 / 4 wave (root mean square, rms).

[0202] FIG. 7 shows an example of an OCT objective lens assembly 510, 512 in which the OCT beam 312 includes light 312a over a range of wavelengths, for example, across the near-infrared portion of the optical spectrum.

[0203] The OCT light is reflected from the reflective surface 334 of the scanning mirror assembly and is focused first by the OCT objective lens 510 and then by the field lens 512, before emerging as a telecentric beam 312b. 1,2,3 are shown in FIG. 7 as being focused onto a telecentric image plane 700, and each beam 312b 1,2,3 represents where the OCT beam 312b appears at a particular scan angle; in other words, the telecentric exit beams 312b1, 312b2, and 312b3 are sequential beams that are generated as the B-scan progresses.

[0204] The OCT beam 312 deflected from the mirror surface, in other words, passes through the OCT objective lens assembly 510 (which in some embodiments also includes a field lens 512), and the light 312b forming the OCT beam 312, shown schematically in FIG. 7 as OCT exit beams 312b1, 312b2, and 312b3, can be designed to exit perpendicular to the intermediate image plane at all scan angles and therefore be telecentric.

[0205] In some embodiments, all air-to-glass interfaces, such as 514, are convex to eliminate back-reflection artifacts in the OCT image. Thus, the OCT objective lens assembly shown in FIG. 7 converts the angular input OCT scan or probe beam 312a reflected from the MEMS scan mirror surface 334 into a telecentric OCT scan or probe beam 312b (or rather beam 312b 1,2,3, which is then output into 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 by a fold mirror 316 toward a beam splitter 318, as shown in FIGS. 3A and 3B. Alternatively, for example, the telecentric OCT scan or probe beam 312b may pass directly in free space to the fold mirror 316, where it is reflected toward the beam splitter 318.

[0206] The focusing lens assembly 314 serves as an optical interface for the telecentric OCT beam 312b to the microscope objective 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 at an intermediate image plane 700 where the telecentric OCT beam 312b is focused as it emerges from the scanning mirror assembly. Therefore, to use the OCT scanner 206 without the focusing lens assembly, the sample must be positioned at the intermediate image plane 700 in some manner. For example, as shown in the exemplary embodiments of the OCT scanner in FIGS. 3A, 3B, and 4, a lens would be required to optically couple to the microscope objective 210, or alternatively, the objective 210 would require a much shorter focal length. Such a short focal length would not be 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 another type of application. For example, an OCT scanner 206 used for ocular imaging, particularly animal eye imaging, may not require a focusing lens 314 .

[0207] In some exemplary embodiments of the OCT scanner adapter 206 used with a surgical microscope, the focusing lens assembly 314 is fixed and set at an appropriate back focal length to collimate and expand the incoming telecentric OCT beam 312b to have a collimated beam diameter of 10.6 mm at the exit. Because the OCT beam 312b is collimated upon exiting the focusing assembly, it is focused at the focal plane of the microscope objective lens 210, similar to microscope optics.

[0208] Alternatively, the object distance is effectively adjusted by adjusting the position of the focusing lens assembly 314 relative to the intermediate image plane, thereby changing the focal position of the microscope objective lens 210 appropriately for OCT scanning, while the focal position remains fixed for the microscope optics.

[0209] An advantage of having a focusing lens assembly 314 in some embodiments of an OCT scanner, such as that of the exemplary embodiment shown in Figures 3A, 3B, and 4, is that if the surgeon moves the eye during the surgical procedure, the OCT scanning system can keep the OCT focused on the specified anatomical feature using appropriate auto-focusing techniques known in the art.

[0210] Another advantage of embodiments of the OCT scanner 206 including the focusing lens assembly 314 is that they can be used in some situations even if the microscope optics are improperly set by the user of the microscope 200, e.g., a surgeon or assistant. For example, if the microscope is non-parfocal, i.e., if the microscope eyepieces are set to infinity for a user with corrective vision through contacts or glasses, the microscope optics will focus at the focal plane of the microscope objective. If the microscope eyepieces are not set to accommodate the refractive error of the microscope user's vision, some users can move the entire microscope, for example, using handles 204a and 204b, as shown in Figures 2A and 2B, to adjust or accommodate their refractive error. However, this movement of the microscope optics results in the scanned tissue sample or other scanned object of interest (e.g., the eye under surgery) no longer being positioned at the actual focal plane of the microscope objective 210 achieved 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 focusing lens assembly 314.

[0211] 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 to an F19 positive / negative meniscus doublet field lens 512 to direct the scanned collimated OCT beam 312 reflected from the MEMS scanning mirror surface 334 to the intermediate telecentric image plane shown in Figure 7. The OCT return light beam passes through the OCT field lens, then passes through the OCT objective lens, and then is reflected again through the MEMS mirror reflective surface 334 and along the OCT output arm 518 via the OCT collimating lens 516 (see also Figure 5A) into the interferometer assembly (not shown in Figure 5A, see SD-OCT system 100 in Figure 1).

[0212] In some embodiments, as shown in the exemplary embodiment of Figures 5A and 7, all air-to-glass interfaces, such as surface 514 and collimating lens 516 of the objective lens assembly 510 for the outgoing OCT beam 312 and the returning OCT beam (not shown), are convex to eliminate back-reflection artifacts in the OCT images.

[0213] In some embodiments, the total track length L within the optical block of the scan mirror assembly is the sum of the length L1 from the end face 530 of the optical fiber 308a in the fiber optic ferrule 532 to the reflective surface 334 of the scan 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.

[0214] In some embodiments, the optical path difference OPD at the sample being scanned has an OPD curvature greater than 100 mm.

[0215] In some embodiments, the OCT scan or probe beam is telecentric to better than a 0.03 degree angle of incidence.

[0216] In some embodiments, the focusing system 314 provides a mechanism for adjusting the OCT beam 312 so that the OCT focal plane can be controlled within a range of ±30 mm to align with the microscope optical channel focal plane.

[0217] In some embodiments, the MEMS OCT scanner has a lateral XY profile with X less than 42 mm and Y less than 35 mm, as shown schematically in FIG. 5A, allowing the OCT scanner system housing to fit laterally within the lateral housing profile of the microscope optics carrier footprint. This is advantageous because it reduces obstructions in the sterile field for surgical applications. In some embodiments of the optical block implementing the scanning mirror assembly 310, the optical block has lateral dimensions of a width X of about 40.6 mm or equal and a depth Y of about 34.5 mm or equal, with a track length L of about 40 mm or less.

[0218] In some embodiments, the scanning mirror assembly further comprises an optical angular displacement measurement system 156 for determining the tilt angle of the reflective surface relative to the incident light, 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 measurement light beam that is incident on the reflective surface, and a position sensing detector, the reflective surface configured to reflect the incident collimated light beam at a first optical surface to form a reflected position measurement light beam that travels towards the position sensing detector.

[0219] 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 provide angular displacement measurement information to a controller configured to control the tilt angle of the reflective mirror surface relative to the illuminating light beam. In some embodiments, the closed-loop control uses a PID feedback loop to adjust the drive voltage to the MEMS based on position and also to damp ringing artifacts caused by fast direction changes.

[0220] Advantageously, in some embodiments where the scanning mirror assembly comprises a scanning mirror assembly 310 within the OCT scanning device 206, the input beam comprises an OCT probe beam 312 that is reflected along an OCT probe beam arm of the scanning mirror assembly through optical components toward the sample or similar object of interest 116. The scanning mirror assembly 310 is configured to output the OCT probe beam 312 as a telecentric OCT probe beam toward the sample focal plane 154, such that the optical path length of the OCT probe beam from the light source 102 to the sample focal image plane 154 is equal to the optical path length traversed by a reference OCT beam from the same OCT light source 112 along the reference arm 103 of the interferometric OCT system 100 connected for 2D scanning of the sample region 116.

[0221] In some embodiments, a 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 the OCT scan 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, that enable an OCT image showing the internal scanning structure within the scan region to be displayed on a display 152. This image, in some embodiments, can be generated in real time to guide the surgeon and / or, in some embodiments, other parties on one or more suitable displays 152.

[0222] In some embodiments of the OCT scanner adapter 206, the OCT scanner adapter 206 is configured to be secured to a lower carriage of a housing for 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.

[0223] In some embodiments of the OCT scanner adapter 206, the OCT scanner adapter 206 is configured to be secured to the lower carriage of the microscope optics housing, such that when the lateral footprint of the housing 208 of the OCT scanner adapter 206 is positioned within the lateral footprint of the housing 202 of the surgical microscope 200, the objective lenses 114, 210 of the OCT scanner adapter 206 are aligned with the optical channels of the microscope optics.

[0224] In this manner, a surgical microscope, such as surgical microscope 200 as shown in Figures 2A and 2B, can be provided in accordance with the disclosed technology, including microscope optics, a housing 202 containing the microscope optics, and an OCT scanner adapter 206, the OCT scanner adapter 206 including a scanning mirror assembly in accordance with the disclosed technology, such as shown by way of example in Figures 5A and 3B. The OCT scanner adapter 206 can be configured to output image data that is subsequently input to an image processor of an OCT system, such as the OCT system shown in Figure 1.

[0225] Accordingly, some embodiments of the microelectromechanical systems (MEMS) two-dimensional scanning mirror assembly (310) disclosed above include a scanning mirror assembly having an optical design including: a movable MEMS scanning mirror having a reflective surface 334; a point light source 308a for a light beam; a collimating lens assembly 516 configured to receive light from the light source and output a collimated light beam having an exit beam diameter above a threshold toward the reflective surface 334; and objective lens assemblies 510, 512 through which the collimated light beam reflected from the reflective surface exits the scanning mirror assembly. The reflective surface 334 is configured to reflect the incident collimated light beam to form a probe beam 312, which exits the mirror assembly as a telecentric beam (312) toward a telecentric image plane with a resolution better than a telecentric beam resolution threshold. The optics of the scanning mirror assembly are configured to achieve a total track length L from the point source to the telecentric image plane (700) of less than 40 mm, and the scanning mirror assembly can be realized in an optical block that is 41 mm wide or less, preferably 40.6 mm wide, and 35 mm long or less, preferably 34.5 mm long, excluding the fiber optic connector 308 and MEMS support 500 (see block dimensions X and Y shown in FIG. 5A).

[0226] The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0227] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items and may be abbreviated as " / ".

[0228] It will be further understood that the terms "comprises," "comprising," "includes," and / or "including," as used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0229] Terms such as "first," "second," and the like may be used herein to describe various elements, but it should be understood that these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first element can be referred to as a second element, and similarly, a second element can be referred to as a first element, without departing from the scope of the present disclosure.

[0230] Relative terms such as "below" or "above" or "upper" or "lower" or "horizontal" or "vertical" may be used herein to describe the relationship of one element to another, as shown in the figures. It will be understood that these terms, and those described above, encompass different orientations of the device in addition to the orientation shown in the figures. When a component is referred to as being "connected" or "coupled" to another component, it should be understood that the component may be directly connected or coupled to the other component, but that other intervening components may also be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present.

[0231] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Terms used herein should be interpreted to have a meaning consistent with their meaning in the context of the present specification and related art, and will not be interpreted in an idealized or overly formal sense unless expressly defined as such herein.

[0232] While some aspects have been described in the context of an apparatus, it will be apparent that these aspects also represent a description of a corresponding method, where a block or apparatus corresponds to a step or feature of a step, and similarly, aspects described in the context of a step also represent a description of a corresponding block or item or feature of a corresponding apparatus.

[0233] It is to be understood that the present disclosure is not limited to the embodiments described above and illustrated in the drawings, but rather, those skilled in the art will recognize that many changes and modifications may be made within the scope of this disclosure and the appended claims. The drawings and specification disclose embodiments by way of example only, and not by way of limitation, the scope of the inventive concept being set forth in the following claims.

Claims

1. A microelectromechanical system (MEMS) two-dimensional scanning mirror assembly (310), the scanning mirror assembly comprising scanning mirror optics, the scanning mirror optics comprising at least: a movable reflective surface (334) of a MEMS scanning mirror, the movable reflective surface (334) being movable in two dimensions; a collimating lens assembly (516) configured to receive the scanning light beam from the scanning light source (308 a) and output a collimated scanning light beam toward the reflective surface (334), the collimated scanning light beam having an output beam diameter from the collimating lens assembly (516); an objective lens assembly (510, 512), wherein the collimated scanning light beam reflected from the reflective surface (334) exits the scanning mirror assembly (310) through the objective lens assembly; and an optical design comprising: the scanning mirror assembly optical configuration includes the reflective surface (334) configured to reflect an incident collimated scanning light beam toward the objective lens assembly (510, 512) to form a telecentric scanning beam (312) that exits the mirror assembly telecentrically toward a telecentric image plane (700); As the reflective surface (334) moves during scanning, the point at which the telecentric scanning light beam converges in the telecentric image plane changes; A MEMS scanning mirror assembly, wherein at least the position and dimensions of the scanning mirror optics within the scanning mirror assembly are configured to minimize a track length L from the light source (308a) to the telecentric image plane (700).

2. 2. The MEMS scanning mirror assembly of claim 1, wherein the position and dimensions of the scanning mirror optical system within the mirror assembly define a track length L from the light source (308a) to the telecentric image plane (700), and the track length L is 40 mm or less.

3. the scanning light source (308a) comprises an optical fiber end face (532) that provides a point light source; The MEMS scanning mirror assembly of claim 1 , wherein the numerical aperture of the point light source and the focal length of the collimating lens assembly (516) are configured such that the exit beam diameter of the scanning light beam from the collimating lens is at least 3.1 mm.

4. The MEMS scanning mirror assembly of claim 1 , wherein the resolution of the telecentric scanning light beam at the telecentric image plane is better than 6 microns.

5. 5. The MEMS scanning mirror assembly of claim 1, wherein the reflective surface (334) is configured to move within + / - 5 degrees about each of two orthogonal axes x and y that intersect at the optical center of the reflective surface.

6. 6. The MEMS scanning mirror assembly of claim 1, wherein the objective lens assembly optics comprises an objective lens (510) and a field lens (512), and the total track length L depends on the combined focal length of the objective lens assembly optics.

7. The MEMS scanning mirror assembly of claim 6 , wherein 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.

8. 8. The MEMS scanning mirror system of claim 1, wherein the optical path difference (OPD) of each scanning sequential beam forming the telecentric scanning beam output by the scanning mirror assembly (310) has a radius of curvature greater than 100 mm.

9. 9. The MEMS scanning mirror system of claim 1, wherein each telecentric scanning beam is telecentric at an angle of incidence better than 0.03 degrees from the normal to the telecentric image plane.

10. The MEMS scanning mirror assembly of any one of claims 1 to 9, wherein the reflective surface (334) comprises a large diameter gold coated silicon mirror bonded to an underlying mirror movement mechanical structure of the MEMS scanning mirror assembly (310).

11. the MEMS scanning mirror assembly (310) is provided as an optical block in an optical coherence tomography (OCT) scanner (206); the scanning light beam comprises an OCT probe beam (312); The MEMS scanning mirror assembly of claim 1 , wherein the light source (308 a) comprises an optical fiber (308 a) having an end face (532) that acts as a point source of the OCT probe beam (312).

12. the OCT probe beam provides depth scanning of the sample; The MEMS scanning mirror assembly (310) of claim 10 or 11, wherein the OCT light returning from the sample has a lateral optical resolution of 6 μm or better.

13. The MEMS scanning mirror assembly of claim 11 or 12, wherein the OCT scanner (206) is provided as an OCT scanner adapter (206) for a surgical microscope (200).

14. 1. A spectral domain optical coherence tomography scanner system (100) including an optical interferometer device, the scanner system (100) comprising: The device comprises an illumination arm (101) including a light source (102), a scanning depth reference arm (103), a scanning arm (105), and a coupler (104) connected to a detection arm (107); An illumination light beam from the light source (102) enters the coupler (104) along an illumination arm (101); the illumination light beam is split by the coupler (104) into a scanning depth reference light beam that follows the scanning depth reference arm (103) towards a reflective surface (108) and a scanning light beam that follows the scanning arm (105) towards a sample to be scanned; the scanning arm (105) comprises a scanning mirror assembly (310) according to any one of claims 1 to 14, configured to move the scanning light beam across the sample such that light returned from the sample is returned along the scanning arm (105) towards the coupler (104); The return light from the scanning arm and the return light from the scanning depth reference arm (103) are directed by the coupler (104) to an interference detector (136) located in a detector arm (107) configured to detect interference between the return light from the scanning arm and the return light from the scanning depth reference arm (103); The scanner system (100), wherein the interference detector (136) is configured to output data including an interference signal of the returned light for image processing to generate a tomogram of the scanned sample.

15. The SD-OCT scanner system (100) of claim 14, further comprising an image processor configured to process the received OCT interference signals and output an OCT image for display.

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