Microbench OCT Design

Abstract

The OCT system is built on a micro- or semiconductor optical bench and uses free-space optics and may avoid the use of optical fibers.

Description

[Technical field]

[0001] The present invention relates generally to the field of optical coherence tomography (OCT) and optical coherence domain reflectometry (OCDR) systems, and more specifically to the use of micro-optics in the design / construction of low-cost and / or compact OCT and OCDR systems. [Background technology]

[0002] There is a growing need for compact, low-cost Optical Coherence Tomography (OCT) and Optical Correlation Domain Reflectometry (OCDR) systems. OCDR systems measure light scattering / reflectance within a sample axially along a light sampling beam, while OCT systems combine multiple such measurements along a direction orthogonal to the axial illumination to produce a cross-sectional or tomographic image of the sample. Typically, the sample is biological tissue, but could be other types of materials.

[0003] Until now, there have been two main approaches to achieve lower-cost systems: redesigning classical “macroscopic” OCDR / OCT systems (e.g., bulk optics using discrete bulk optical components and / or optical fibers) to reduce size and cost, and implementing OCDR / OCT systems on semiconductor chips, so-called “OCT-on-chip”. Redesigning macroscopic OCDR / OCT systems, which generally consist of a set of components (e.g., light source, splitter, etc.) connected by optical fibers, has so far been unable to achieve the desired cost reduction goal due to the cost of the individual components and the overall manufacturing cost of the system. “OCT-on-chip” systems have the potential to achieve the miniaturization and cost reduction goals, but they entail high initial investment costs, e.g., research and development in the design and manufacturing of photonic integrated circuits (PICs), as well as prohibitively expensive non-recurring expenses (NRE), e.g., investment in the development and construction of manufacturing facilities for large-scale semiconductor chips (e.g., PICs).

[0004] An alternative to photonic integrated circuits is the use of so-called micro-optical benches or semiconductor optical benches. Similar to a typical optical bench (or optical table or optical breadboard), which can be a linear rigid bar or base (typically graduated) on which lenses, light sources, and other optical components can be mounted, a micro-optical bench is a substrate base (such as a ceramic bench or other base material) in which locations (e.g. cavities or pits) for receiving or mounting micro-optical components are constructed.

[0005] The potential of micro-optical benches in the construction of optical systems has been recognized. For example, light sources (e.g., swept-source light sources) have been implemented on micro-optical benches, and these light sources have been used in the construction of macroscopic (e.g., bulk optics-based) swept-source OCT systems. In addition to providing swept-source illumination light, micro-optical benches have also been used to implement k-clock interferometers, which interfere the swept-source light with itself with a small optical delay to generate a modulated signal that can be used either to trigger the OCT detection system or to compensate for nonlinearities in the sweep rate of the swept source. An example of this implementation is described in non-patent document 1. The semiconductor optical bench is constructed / grown on a PIC type substrate (e.g., single crystal silicon or other semiconductor wafer). In addition to having openings (e.g., cavities or pits) on the surface for receiving individual components, the semiconductor optical bench may also include integrated circuits. Semiconductor optical benches have been used in telecommunication applications (e.g., as optical transceivers). It is believed that the use of semiconductor optical benches could potentially realize reduced size and cost-effective LIDAR modules for autonomous vehicles. Nevertheless, to the inventor's knowledge, semiconductor optical benches have not been used in the field of medical imaging or OCT. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Bart Johnson, Walid Atia, Seungbum Woo, Carlos Melendez, Mark Kuznetsov, Tim Ford, Nate Kemp, Joey Jabbour, Ed Mallon, Peter Whitney, "Tunable 1060 nm VCSEL co-packaged with pump and SOA for OCT and LiDAR," Proceedings of SPIE (Proc. SPIE10867), Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XXIII. XXIII), 1086706 (February 22, 2019), doi:10.1117 / 12.2510395 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to reduce the cost and size of OCT / OCDR systems. Another object of the present invention is to simplify the design and construction of OCT / OCDR systems, for example, minimizing the use of optical fibers and maximizing the use of micro-optical components.

[0008] Another object of the present invention is to provide parallelization of OCT and integration of scanning into compact designs. A further object of the present invention is to simplify the calibration of OCT / OCDR systems. [Means for solving the problem]

[0009] The above objectives are achieved in an OCT / OCDR system that identifies and maximizes the advantages of building an OCT / OCDR system on a micro-optical or semiconductor optical bench. The present invention uses a micro-optical or semiconductor optical bench to realize a compact, low-cost optical coherence tomography (OCT) system and an optical correlation domain reflectometry (OCDR) system. Both micro-optical and semiconductor optical benches can be described as a (typically rigid) base that supports and aligns (e.g., separate) micro-optical components, although semiconductor optical benches are generally smaller than micro-optical benches and may differ in construction materials and manufacturing processes. A micro-optical bench is typically a rigid carrier (such as a ceramic bench or other base material) that houses several micro-optical elements, which are positioned and often actively aligned by a robot. Typical lens diameters are in the range of 0.5 mm to 2.5 mm. A common package for housing a micro-optical bench is a standard (e.g., 14-pin) butterfly package or surface mount device (SMD) package (or other micro-package / integrated circuit package). A semiconductor optical bench is typically smaller than a micro-optical bench and consists of a (e.g., grown) substrate (e.g., a silicon wafer) with recessed openings (e.g., receptacles, cavities, or pits) on its surface, which are designed to receive and hold micro-optical or other (e.g., discrete) components at predetermined (X, Y, Z) positions and orientations. This may eliminate (or reduce) the need for active alignment of the received components. Optionally, according to the present invention, a semiconductor optical bench may also have integrated circuits (ICs) and / or photonic integrated optical components, PICs (e.g., integrated photonic circuits), configured / grown / built in / on the semiconductor optical bench.This application uses the term micro-optical bench (or microbench) for the slightly larger, typically rigidity-based and / or relaxed alignment variations, as described above, to distinguish it from semiconductor optical benches, although it is recognized that semiconductor optical benches are sometimes referred to as micro-optical benches in the prior art.

[0010] Implementation of OCT / OCDR on either a micro-optical bench or a semiconductor optical bench can significantly reduce costs by replacing the bulk and fiber optic components of a traditional bulk optical (e.g., macroscopic) system with micro-optical components. Also, the semiconductor optical bench approach, like the "OCT-on-a-chip" approach described above, can achieve costs similar to those expected with "OCT-on-a-chip". Although the semiconductor optical bench concept may require more non-recurring expenses (NRE) than the micro-optical bench approach, both approaches can be achieved with a lower development effort than the "OCT-on-a-chip" concept from the current state of technology, while still achieving greater cost savings and reliability improvements compared to redesigning a "macroscopic" OCDR / OCT system. The micro-optical bench approach also offers greater flexibility in component integration since components do not need to be constructed from chip materials.

[0011] Some features / new approaches of the present invention include the implementation of an OCDR / OCT system on a micro-optical bench or semiconductor optical bench with micro components (e.g., micro-optical components) and / or eliminating optical fibers. Bulk optical components (such as those used in "macroscopic" or "bulk optical" OCDR / OCT systems) are expensive and incur significant additional costs associated with addressing alignment issues between components. While optical fibers address many of the alignment challenges in bulk optics, they reduce the stability of the system by adding temperature dependence and motion sensitive polarization effects, and fiber length variability complicates the design and manufacturing process. The present approach (particularly using a semiconductor optical bench) allows for the creation of reliable free space optics OCT / OCDR systems with minimal alignment / calibration issues.

[0012] Other objects and achievements of the present invention, together with a fuller understanding of the invention, will become apparent and appreciated by reference to the following description and claims taken in conjunction with the accompanying drawings.

[0013] To facilitate the understanding of the present invention, several publications are cited or referenced herein. All publications cited or referenced herein are incorporated by reference in their entirety.

[0014] The embodiments disclosed herein are merely examples, and the scope of the disclosure is not limited thereto. Any feature of an embodiment described in one claim category, e.g., a system, may also be claimed in another claim category, e.g., a method. Dependencies or back references in the appended claims are selected for formality reasons only. However, any subject matter resulting from a careful back reference to a previous claim may also be claimed, thereby disclosing any combination of the claims and their features and may be claimed regardless of the dependencies selected in the appended claims. [Brief description of the drawings]

[0015] In the drawings, like reference symbols / letters refer to like elements. [Figure 1A] FIG. 1 illustrates a schematic frequency-domain optical coherence tomography (FD-OCT) system. [Figure 1B] FIG. 1 shows an example en face vasculature image. [Figure 1C] FIG. 1 shows an exemplary B-scan of a vasculature (OCTA) image. [Figure 1D] FIG. 1 illustrates OCT with orthogonal polarization states that uses polarizers to create interference between light returning from the reference and sample arms. [Figure 1E] FIG. 1 illustrates an exemplary computer system (or computing device or computer). [Figure 2A-2B] FIG. 2A illustrates an exemplary OCT system 11 on a semiconductor optical bench 13 (or alternatively on a micro-optical bench), and FIG. 2B illustrates an alternative embodiment of the OCT system of FIG. 2A in which a window W (or other transmissive element) is used as an interface between the hermetically sealed bench 13 and the outside world in addition to using optical fibers. [Fig. 2C-2D]FIG. 2C shows another alternative embodiment in which the reference arm RefArm is fully built / integrated onto the optical bench 13, eliminating the need for a reference arm interface between the optical bench 13 and the outside world, and FIG. 2D shows an example of a PS-OCT having two detection paths PthA and PthB and implemented on a micro-optical bench or semiconductor optical bench 13. [Fig. 2E-2F] FIG. 2E shows an orthogonal detector approach, where the light in the detection arm (below pinhole P) is first split by a non-polarizing beam splitter non-PBS before traveling to two individual polarizing beam splitters PBS2 and PBS3, and FIG. 2F shows an alternative embodiment of an OCT system, where a window W is used to connect between the bench and the sample and reference arms, and fiber couplings (31 and 33) are used to connect to detectors 38, 40. [Fig. 2G-2H] FIG. 1 illustrates two embodiments that address the problem of nonlinearity in the frequency sweep of the light source that may be found in a swept-source OCT system. [Diagram 3] FIG. 1 shows an example of a polarizing beam splitter PBS suitable for receiving light in the detection arm and redirecting it to the silicon wafer surface and thereby to the integrated detectors D1, D2. [Figure 4A-4B] FIG. 4A shows one way of combining multiple VCSELs (41 / 43) using a dichroic mirror 45, and FIG. 4B shows the use of another dichroic mirror 51 to split the light at the detection end of the OCT to different detectors (47 / 49), such as when the VCSELs 41 / 43 of FIG. 4A are operated simultaneously. [Diagram 5] FIG. 13 illustrates an alternative method of scanning a given location in sample tissue with multiple VCSELs covering different wavelength bands. [Figure 6] FIG. 2 illustrates an exemplary guidance system for directing an OCT imaging module (in accordance with the present invention) to the pupil center. [Figure 7A-7B]Figure 7A is a pivot system for scanning an imaging module, showing a structure for moving the imaging module along the surface of a sphere using one or more pivot points, and Figure 7B shows the displacement of the imaging platform of Figure 7A when the structure is rotated or pivoted. [Figure 7C-7D] FIG. 7C is an alternative pivot system for scanning an imaging module, showing a mechanism for mechanically shifting the effective pivot point of FIG. 7A, and FIG. 7D shows the displacement of the imaging platform of FIG. 7C as the structure is rotated or pivoted. [Figure 8] FIG. 1 illustrates how the present invention can eliminate or reduce the need for a very restricted area known as the "pupil box" and, optionally, an ophthalmic lens. [Figure 9A] FIG. 13 illustrates another approach to physically moving the scanning system (or “OCT assembly” OA1) to scan across the eye through the use of a polar coordinate-based system. [Figure 9B-9C] FIG. 9B provides a close-up front view of the radial slide RS1 relative to the patient's eye, and FIG. 9C illustrates an exemplary scan pattern suitable for a spherical scanning assembly, particularly for OCTA scanning. [Figure 10] FIG. 2 shows the placement of a fixation target behind a sphere traversed by the imaging system. [Figure 11] FIG. 1 illustrates the continuous acquisition of a limited field of view by translating the scanning module of the present invention. [Figure 12] FIG. 13 shows an arrangement in which the beams incident on the scan mirror are a line of beams that all strike the scan mirror at the same location, but at different angles along the line. [Figure 13A] FIG. 13 illustrates another way to convert a 2D array into a set of points equally spaced along the vertical direction by slightly rotating the array. [Figure 13B]FIG. 13B shows another way of achieving a similar effect to FIG. 13A, in which the array of VCSELs is in the form of a parallelogram, with each row or column being shifted slightly perpendicular to the scanning direction. [Figure 13C] FIG. 1 illustrates that the number of VCSELs in the vertical and horizontal directions can vary significantly. [Figure 14A-14B] FIG. 13 illustrates passing the beam array through a lenslet array (or lens array) to adjust the amount of numerical aperture and pitch product to optimize imaging on the retina. [Figure 15] FIG. 1 illustrates, by way of example, an exemplary OCT B-scan image of a normal retina of a human eye, identifying various typical retinal layers and boundaries. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] OCDR systems measure light scattering / reflectance in a sample axially along a light sampling beam, while OCT systems combine multiple such measurements along a direction orthogonal to the axial illumination to generate a cross-sectional or tomographic image of the sample. OCT angiography (OCTA) is an extension of OCT that identifies (e.g., renders in an image format) blood flow in tissue layers. OCTA can identify blood flow by identifying differences (e.g., contrast differences) over time in multiple OCT images of the same retinal region and designating differences that meet a predetermined criterion as blood flow. Because OCDR, OCT, and OCTA are similar in structure and share many parts, this description will focus on OCT with the understanding that one skilled in the art will be able to apply this description to OCDR and OCTA. It should be understood that the present invention applies equally to OCDR and OCTA unless otherwise specified.

[0017] In general, optical coherence tomography (OCT) uses low-coherence light to generate two-dimensional (2D) and three-dimensional (3D) internal views of biological tissue or other samples. Examples of OCT systems are provided in U.S. Patent Nos. 6,741,359 and 9,706,915, which are incorporated by reference herein in their entireties.

[0018] FIG. 1A shows a general-type frequency domain optical coherence tomography (FD-OCT) system OCT-1 used to collect 3D image data of an eye E suitable for use with the present invention. The FD-OCT system OCT-1 includes a light source LtSrc1. Typical light sources include, but are not limited to, a broadband light source with a short temporal coherence length or a swept laser light source. Sample light (SLt) from the light source LtSrc1 is guided down a sample arm, typically by an optical fiber (Fbr1), to illuminate a sample, e.g., an eye E, a typical sample being human intraocular tissue. The light source LtSrc1 can be, for example, a broadband light source with a short temporal coherence length in the case of spectral domain OCT (SD-OCT) or a tunable laser light source in the case of swept-source OCT (SS-OCT). The sample light can typically be scanned using a scanner Scnr1 between the output of the optical fiber Fbr1 and the sample E, so that a beam of light (dashed line Bm) is scanned laterally over the area of ​​the sample to be imaged. The light beam from the scanner Scnr1 can pass through the scan lens SL and the ophthalmic lens OL and be focused on the sample E to be imaged. The scan lens SL can receive a beam of sample light SLt from the scanner Scnr1 at multiple angles of incidence and generate substantially collimated light, and the ophthalmic lens OL can then focus the collimated light on the sample. This example shows a scan beam Bm that needs to be scanned in two lateral directions (e.g., X-direction and Y-direction on a Cartesian plane) to scan a desired field of view (FOV). This example is a point-field OCT that uses a point-field beam (a beam of light focused to a point) to scan across the sample. Thus, the scanner Scnr1 is exemplarily shown to include two sub-scanners, a first sub-scanner Xscn for scanning the point-field beam across the sample in a first direction (e.g., horizontal X-direction) and a second sub-scanner Yscn for scanning the point-field beam on the sample in an intersecting second direction (e.g., vertical Y-direction).If the scanning beam is a line field beam (a beam of light focused into a line), e.g., line field OCT, which may sample an entire line portion of the sample at one time, then only one scanner may be required to scan the line field beam across the sample to span the desired FOV. If the scanning beam is a full field beam (e.g., full field OCT), then no scanner may be required and a full field light beam may be illuminated across the entire desired FOV at one time.

[0019] Regardless of the type of beam used, the light scattered from the sample (SCTl) is collected. In the present example of FIG. 1A, the scattered light SCTl returning from the sample is collected in the same optical fiber Fbr1 used to route the light for the illumination SLt.

[0020] The reference light RefL derived from the same light source LtSrc1 travels with the sample light SLt until it is split into a separate reference path (e.g., a reference arm) by an optical splitter LSpltr1, implemented here as a fiber coupler Cplr1. It should be understood that different types of optical splitters are known. The reference path includes an optical fiber (Fbr2) and a retroreflector (RR1) with an adjustable optical delay. Those skilled in the art will understand that a transmissive reference path can also be used and that the adjustable delay can be placed in the sample arm or the reference arm of the interferometer. The collected light scattered from the sample (e.g., the scattered light SCTl returning from the sample arm) is combined with the reference light RefL returning from the reference arm by an optical combiner LCmbnr1, embodied here by a fiber coupler Cplr1. Again, it should be understood that different types of optical coupling mechanisms are known in the art. The reference light RefL and the scattered light SCTl then travel together to an OCT photodetector Dtctr1 (e.g., a photodetector array, a digital camera, etc.), and an OCT signal OS is generated by the interference between the reference light RefL and the scattered light SCTl, which may be provided to an electronic processor Cmp1 (or a computer system) that converts the observed interference into depth information of the sample. The depth information may be stored in a memory associated with the processor Cmp1 and / or displayed on a display (e.g., a computer / electronic display / screen) Scrn1 (e.g., as a scan image as shown in Figures 1B and 1C). The processing and storage functions may be localized within the OCT instrument, or the selection functions may be offloaded (e.g., executed on) onto an external processor (e.g., an external computing device at a local or remote site) to which the collected data may be transferred (e.g., wired or wirelessly, e.g., by a peer-to-peer connection or via a computer network such as a local area network, a wide area network, the Internet, etc.).

[0021] In this example, the interference between the reference light RefL and the scattered light SCTl occurs in the light combiner LCmbnr1 (implemented as a fiber coupler Cplr1), but it can also occur in the optical components between the light combiner LCmbnr1 and the detector Dtctr1. For example, if the reference light RefL and the scattered light SCTl have orthogonal polarization states when combined by the light combiner LCmbnr1, interference can be generated at 45 degrees to the polarization states of RefL and SCTl by a polarizer (not shown), as described in U.S. Pat. No. 7,126,693 (B2), which is incorporated herein by reference in its entirety. For illustrative purposes, the system 700b of U.S. Pat. No. 7,126,693 (B2) is reproduced herein as FIG. 1D, with the polarizer identified as component 752b. For illustrative purposes, the component that generates the interference is referred to below as an interference generator IG.

[0022] 1A, although a single fiber port is shown going to detector Dtctr1, those skilled in the art will recognize that interferometers of various designs can be used for balanced or unbalanced detection of interference signals. Optionally, the output analog OCT signal AOS from detector Dtctr1 can be converted to a digital OCT signal DOS by an analog-to-digital converter (ADC) AD1 and then fed to a processor (e.g., an internal or external computing device) Cmp1.

[0023] FIG. 1E shows an example of a computing device (or computer system). This unit can be dedicated to data processing or perform other tasks that are very general and not dedicated to OCT devices. The processor (computing device) Cmp1 can include, for example, a field programmable gate array (FPGA), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a graphics processing unit (GPU), a system on a chip (SoC), a central processing unit (CPU), a general purpose graphics processing unit (GPGPU), or a combination thereof, which can perform some or all of the processing steps in a serial and / or parallel manner with one or more host processors and / or one or more external computing devices. A more detailed description of an exemplary computing device is provided below.

[0024] The sample and reference arms in the interferometer can be constructed of bulk optics, fiber optics, or hybrid bulk optics and can have different architectures such as Michelson, Mach-Zehnder, or common-path based designs, as will be appreciated by those skilled in the art. The light beams used herein can be carefully directed all over the optical path. Instead of mechanically scanning the beam, a light field can illuminate a one- or two-dimensional area of ​​the retina to generate OCT data (see, e.g., U.S. Pat. No. 9,332,902; D. Hillmann et al., "Holoscopy-Holographic Optical Coherence Tomography," Optics Letters, vol. 36(13), p. 2390, 2011; Y. Nakamura et al., "High-Speed ​​Three Dimensional Human Retinal Imaging by Line Field Spectral Domain Optical Coherence Tomography," Optics Express, vol. 10, no. 1, pp. 111-115, 2012). Express, 15(12), 7103, 2007; Blazkiewicz et al., Signal-To-Noise Ratio Study of Full-Field Fourier-Domain Optical Coherence Tomography, Applied Optics, 44(36), 7722, (2005). In time-domain systems, the reference arm needs to have an adjustable optical delay to create interference. Typically, balanced detection systems are used in TD-OCT and SS-OCT systems, and a spectrometer is used at the detection port for SD-OCT systems.

[0025] While the present invention may be applied to any type of OCT / OCTA / OCDR system as described above, it is described herein fully or partially on a microbench and / or semiconductor optical bench or similar device having specially configured / shaped recesses, each recess designed to receive and hold a particular micro-optical device (or other (e.g., separate) component) at a pre-specified location, preferably at a pre-specified height and orientation. For ease of description, one or more features of the present invention are described as applied to a semiconductor optical bench, but it should be understood that the same feature(s) may be applied to a micro-optical bench unless otherwise stated. Other indicia common in lithography processes may also be used to place a particular micro-optical device at a pre-specified location. Various aspects of the present invention may be applied to any type of OCT / OCTA / OCDR system or other types of ophthalmic diagnostic systems and / or systems, including but not limited to fundus imaging systems, visual field testing devices, and scanning laser polarimeters.

[0026] In SS-OCT system configurations using light sources with long instantaneous coherence lengths, variable delays (e.g., adjustment of the optical path length of the reference arm according to the depth / axial position of the sample region being imaged, as described elsewhere herein) may not be necessary to position the sample within the (system's) depth imaging window. Instead, large optical path length mismatches between the reference and sample lights may be tolerated. For example, in a typical imaging scenario, a large imaging depth may be generated that is large enough so that the sample is always within the depth imaging window. The acquired image may then be cropped to display only the region of interest (e.g., the desired depth range). This region of interest may change dynamically during acquisition, for example to compensate for sample motion. However, this cropping approach requires digitization electronics (e.g., analog-to-digital converters) that are fast enough to resolve the high-frequency interference signal corresponding to the maximum imaging depth, which may be difficult to realize, especially in a cost-effective manner, using standalone video cards, video capture cards, daughter boards, and other discrete components. However, high speed detection and / or digitization electronics (circuitry) may be feasible by integrating the detection and / or digitization electronics (circuitry) directly on the same substrate / base as the semiconductor optical bench on which the present OCT system is built (or ICs on the same substrate / base as the micro-optical bench, e.g., in a manner similar to system-on-chip, SOP, or integrated circuit substrate approaches). Higher operating speeds may be achieved at least in part due to smaller traces (and optionally lower rail-to-rail voltage swings) associated with typical integrated circuits, which avoid / mitigate high frequency interference issues between long traces / leads / wires and large capacitive loads, large signal propagation delays, and typical timing issues associated with routing traces / leads / wires to interconnect with external discrete components.

[0027] Alternatively, the analog OCT signal can be downmixed (or modulated or downconverted or frequency mixed or frequency shifted) at a frequency corresponding to one edge of the desired imaging window (either the minimum path length mismatch or the maximum path length mismatch) to create a downmixed OCT signal with spectral content corresponding to that obtained when the reference arm path length is adjusted to this imaging depth. This downmixing is typically accomplished by frequency mixing the OCT signal with a downmixing frequency to produce the OCT signal plus or minus the downmixing frequency, and then filtering to remove (or select or isolate) the summed (or modulated, mixed, or shifted) frequency. To avoid noise near zero frequency and / or to provide a buffer that can adjust the downmixing frequency if a signal appears in this band near zero frequency, the downmixing frequency can be selected such that the zero frequency is slightly outside the scanning range of interest; in a standard SS-OCT system, a similar effect can be achieved by having the reference arm length slightly outside the depth range of the sample of interest. Downmixing the OCT signal in this way can provide several advantages. Most relevant to the design of the present optical bench (semiconductor optical bench or micro-optical bench), downmixing allows for significant mismatch in the (optical) path length between the reference arm and the sample arm, making it possible to integrate a short reference arm (e.g. shorter than the distance to the sample (e.g. retina) position) on a microbench (or semiconductor optical bench) that does not break away from the micropackage, and making the downmixing frequency tunable can eliminate the need for mechanical or optical adjustment of the reference arm path length or the sample arm path length.

[0028] To quickly find an appropriate downmixing frequency, the source can be swept slowly first to generate a large scan range with a relatively slow A-scan speed, and then once the desired scan depth is identified, a faster sweep speed and corresponding A-scan speed can be switched to and the appropriate downmixing frequency used to precisely set the scan depth for the resulting more limited scan range.

[0029] Electronic adjustment of the downmixing frequency provides rapid adjustment of the imaging window depth (axial position) and allows for adjusting the scan depth during acquisition to follow the (curvature of) the sample (e.g., retina) and even shifting the scan depth between or during A-scans within a B-scan to follow the sample (e.g., adjusting the path length during acquisition to follow the overall sample position, the sample surface, or a specific layer within the sample). Various methods can be used to track a surface or layer, examples include adjusting the downmixing frequency based on the spectrum of the OCT signal or based on the identification of a specific layer or boundary in the OCT image discovered through signal processing of the OCT. In the case of retinal imaging, a possible surface to be followed is the RPE, or the entire retina can be tracked. To track the entire retina, the spectrum acquired by OCT digitization can be kept near the midpoint of the bandwidth range supported by the digitization, while to track the RPE, a peak spectral signal likely to correspond to the RPE can be kept at a fixed frequency.

[0030] The downmixing technique of shifting the scan depth has the advantage of not adding a Doppler shift to the OCT signal, as would be produced by moving the reference mirror to adjust the scan depth. This Doppler shift is undesirable because it affects the image and causes phase wash-out in SD-OCT systems and axial position displacement or broadening of the axial point spread function (PSF) in swept source systems. Electronic adjustment of the downmixing frequency can be achieved through the use of a voltage controlled oscillator.

[0031] Instead of performing the downmixing electronically, the same effect can also be achieved by shifting the optical frequency of either the sample or reference light. An optical modulator, such as an acousto-optic or electro-optic modulator, can be used to generate the individual frequency shifts. In a hybrid microbench / PIC system, this modulation can be provided in the PIC.

[0032] One possible complication of changing the downmixing frequency during acquisition can arise during angiography imaging, where two OCT scans acquired at slightly different times are compared and the difference between the scans indicates motion, usually due to blood flow. If the downmixing frequency is adjusted between two such scans, it may be necessary to compensate for this downmixing frequency change before calculating the difference between the scans, so as not to produce artifacts.

[0033] In some embodiments, one may choose to use the downmixing concept described above to allow for large optical path length mismatch between the sample and reference arms, but may also choose to perform some optical path length adjustments optically for axial sample alignment. This can still be done in a micropackage and without the need for moving parts. For example, a scanning delay line can be implemented using an electro-optical deflector in combination with a diffraction grating and mirrors.

[0034] In a preferred embodiment, the OCT system described above is implemented on a semiconductor optical bench, which is a semiconductor into which slots (recesses) for the micro-optical components are etched and into which the micro-optical components are placed without the need for active alignment processes. Such a system is particularly suitable for mass production, since it benefits from the scalability of the semiconductor manufacturing process. The slots for the micro-optical components can be etched in parallel for hundreds or thousands of devices by patterning the entire semiconductor wafer using lithography. The micro-optical components can then be assembled by a robot for the entire wafer at once, followed by a wafer-level packaging step, in which a lid wafer is bonded on top of the base layer and a hermetic seal is formed. Alternatively, a separate semiconductor optical bench can be used instead of the lid wafer. This "lid" semiconductor optical bench can be constructed with corresponding / complementary slots (or patterns) configured to receive the portions of the micro-optical components that extend onto the surface of the opposing "base" semiconductor optical bench. In this configuration, the micro-optical components are sandwiched between the two semiconductor optical benches and are aligned and held by the two opposing semiconductor optical benches. The lid wafer does not necessarily have to be made of a semiconductor material, but may be made of, for example, glass or ceramic that does not have semiconducting properties. This may be beneficial in cases where operating wavelengths are used where typical semiconductor materials such as silicon are not transparent. It is desirable to have at least one of a transparent bench wafer or a transparent lid wafer, since the bench or lid typically act as a window through which light can be coupled out and / or into the micropackage. The hermetically sealed package may contain a vacuum to allow faster movement of elements within the package, for example, MEMS elements of vertical cavity surface emitting lasers (VCSELs) or MEMS-based beam steering mirrors.Alternatively, it may contain specific gases that prevent or reduce degradation of the active semiconductor optical materials, for example, oxidative damage at the facets of the gain chip.

[0035] Because lithographic patterning of semiconductor wafers creates slots and / or other alignment features with nanometer precision, semiconductor optical benches are particularly beneficial in applications where precise control of optical path length is required. These include, for example, multi-beam OCT systems where a sample is scanned in parallel with multiple beams and imaging depth mismatch between the individual imaging channels is undesirable, or quadrature detectors where, for example, the interference signal to be detected is split and acquired with a relative phase shift of 90 degrees to reconstruct a complex signal.

[0036] 2A shows an exemplary OCT system 11 on a base, e.g., a semiconductor optical bench 13 (or alternatively, on a micro-optical bench). In this example, light from a light source LtSrc1 passes through a half-wave plate (or retarder) 15 (where the symbol lambda λ stands for wave plate, which is an optical device that changes the polarization state of the light wave traveling through the wave plate) to a first polarizing beam splitter (or beam splitter) PBS0. The split light then passes through a first quarter-wave plate 17 to a sample off the bench (along the sample arm) and a second quarter-wave plate 19 to a reference arm off the bench 13. The return light from the sample arm (SCTI) and the reference arm (RefL) is combined at a first polarizing beam splitter PBS0 and passes through a second half-wave plate 21, a first lens 23 (where the symbol L stands for lens), an (optional) pinhole P, and a second lens 25 to reach a second polarizing beam splitter PBS1, which is preferably at 45 degrees to the polarization states of the return light SCTI and RefL and which acts as an interference generator IG (e.g., generates interference). The interference signal is sent to detectors 27, 29 (where the symbol D stands for detector). The purpose of the various half-wave plates in this description is to change the polarization state so that part of the light passes through the polarizing beam splitter and part of the light is reflected by the polarizing beam splitter. This same function can be performed by a wave plate or plates with different amounts of phase retardation. For example, a 22.5 degree half wave plate can be used to rotate the polarization state by 45 degrees so that half the light is reflected and half is transmitted by the polarizing beam splitter, but the same 50 / 50 split can be achieved using a quarter wave plate rotated 45 degrees to obtain circular polarization. One advantage of such an approach may be that all wave plates can be quarter wave plates, reducing the number of different components required. Possible microlenses used in the system include, but are not limited to, ball lenses, GRIN lenses, spherical lenses, aspheric lenses, or freeform lenses.

[0037] Figure 2B shows an alternative embodiment of the OCT system of Figure 2A. Components similar to those of Figure 2A have similar reference numbers and have been described above. In Figure 2B, a window 18A / 18b (where the symbol W represents a window), or other transmissive element, is used as the interface between the hermetically sealed bench 13 and the outside world, rather than using optical fibers.

[0038] FIG. 2C shows another embodiment of an OCT system according to the present invention. Components similar to those in FIG. 2A and FIG. 2B have similar reference numbers and have been described above. In FIG. 2C, the reference arm RefArm is fully built / integrated on the optical bench 13 (semiconductor optical bench or micro optical bench), thus eliminating the need for a reference arm interface (e.g., 18B in FIG. 2B) between the optical bench 13 and the outside world. In this example, the retroreflector (e.g., similar to RR1 in FIG. 1) is implemented as a mirror 20 (where the symbol M represents a mirror). Since interference is obtained when the reference path length matches the sample path length within the coherence length of the light, several ways in which this may be implemented are contemplated herein. A reference arm path length can be created on the optical bench 13 that is approximately (or substantially) equal in length to the sample arm path length. Alternatively, one can use a source with a long coherence length in a swept source system and then utilize only a limited scan depth by not displaying the full scan depth or by downmixing / demodulating the OCT signal before digitization as described above.

[0039] Another embodiment may not require external sample arm optics. Instead, the sample may be placed in contact with or in close proximity to the micro-package. In such an embodiment, all sample arm optics are part of the micro-package. Focusing optics may be used, for example, to simultaneously function as an exit / entrance window for the sample beam.

[0040] Since much of the cost in a micro-optical bench and / or semiconductor optical bench solution is in the NRE and packaging, the complexity of the OCT solution can be increased without significantly increasing the overall cost, making more complex designs such as PS polarization sensitive OCT feasible. FIG. 2D shows an example of a PS-OCT with two detection paths PthA and PthB and implemented on a micro-optical bench or semiconductor optical bench 13. Components similar to those described above have similar reference numbers, and duplicate examples of similar components have similar reference numbers with the letter "b" added to the end. In this example, PBS0 and PBS0b deflect the light to their corresponding reference arms RefArm and RefArmb, each of which includes a quarter wave plate 19 / 19b that rotates the polarization state of the light by 90 degrees when passing twice, so that all the reference light passes through PBS0 and PBS0b back to the corresponding detector paths PthA and PthB. The two polarization states returning from the sample (e.g., the scattered light SCTl through the window 18A) are separated by PBS0b, the first polarization state travels through the polarizer PBS0 to the detector path PthA, and the second polarization state is reflected by PBS0b to the detector path PthB. The light returning from the sample to the detector path PthA is reflected by PBS0 because its polarization state is rotated 90 degrees by the combination of the half-wave plate 15b and the Faraday rotator 22 (where the symbol FR stands for Faraday rotator, a type of polarization rotator). This combination of the half-wave plate and the Faraday rotator also slightly rotates the polarization of the light traveling towards the sample arm, deflecting some of the source light into the reference arm RefArmb. As mentioned above, balanced detection is achieved in each detection path by rotating the polarization state by 45 degrees before entering the polarizing beam splitter PBS1 / PBS1b in front of the corresponding detector 27 / 29 and 27b / 29b.

[0041] FIG. 2E shows another approach involving quadrature detection. In this approach, the light in the detection arm (below pinhole P) passes through a half-wave plate 21 and is first split by a non-polarizing beam splitter (non-PBS) 24 before proceeding to two individual polarizing beam splitters PBS2 and PBS3, which reflect their signals to corresponding detectors 30 / 32 and 34 / 36. In one of the paths between non-PBS 24 and PBS3, a quarter-wave plate (λ / 4) 26 is added to introduce a quarter-wave retardance. Quadrature detection allows the system to distinguish between negative and positive differences in path length between the reference arm and the sample, thereby extending the feasible scan range over a distance where the reference arm path is equal to the sample arm path, by suppressing the complex conjugate mirror image of FD-OCT.

[0042] It may also be desirable to integrate other aspects of the clinical OCT system onto a micro- or semiconductor optical bench to further miniaturize the system and reduce cost. Possible examples include 1)-3) below.

[0043] 1) Integrating a second imaging modality such as a scanning laser ophthalmoscope for retinal imaging and / or tracking. 2) Providing a fixation target for the eye, possibly using a micro-electromechanical system (MEMS) mirror, and directing the fixation target to a different location behind the eye to change the patient's fixation position.

[0044] 3) Focusing and / or aberration correction of the OCT sample to account for differences in the optical properties of different eyes. Such correction can be performed, for example, using a moving lens in the package, an adjustable mirror (e.g., in the package), an Alvarez microlens, or an electrically adjustable lens.

[0045] Another advantage of implementing the OCT on a semiconductor optical bench (or micro-optical bench) is that the OCT can be packaged, for example, in a dual in-line package (DIP) or surface mount device (SMD) (or other micropackage or integrated circuit package) and soldered onto a printed circuit board along with other chips such as processing electronics for the OCT signal.

[0046] In one or more of the above embodiments, the polarizing beam splitter PBS outputs its two separate beams to corresponding detectors that may be integrated in (on) the optical bench 13. Figure 3 shows an example of a polarizing beam splitter PBS suitable for receiving light in the detection arm and redirecting the light to a silicon wafer surface. In this example, detectors D1 and D2 are integrated into a semiconductor optical bench.

[0047] FIG. 2F shows an alternative embodiment of an OCT system according to the present invention. All components similar to those described above have similar reference numbers. As in FIG. 2B, windows (W) 18A / 18B provide an interface from the bench 13 to the sample arm and reference arm. In this example, fiber couplings (31 and 33) are used to interface with the detectors 38 and 40. However, as previously mentioned, it is highly desirable to eliminate optical fibers in the OCT system to improve both stability and manufacturability. Optical fibers in a typical OCT system offer two main advantages: simplified alignment and spatial mode filtering to ensure single mode interference between the light from the reference arm and the light from the sample arm. Current micro-optical bench and semiconductor optical bench technology addresses the need for alignment but does not directly address the need to achieve single mode interference of the return signal. To restrict the light reaching the detector to a single mode, or at least close enough to single mode to achieve good performance from OCT, the return light from the sample arm and reference arm may pass through one or more pinholes P (not shown in FIG. 2F) before detection, as shown in FIGS. 2A-2E. Also, for ease of alignment and to ensure that both the reference and sample beams are confined to the same single mode, it is desirable for the sample and reference beams to pass through the same pinhole together after they are combined. Rather than allowing them to interfere with a beam splitter, as is done in classical systems, combining the two beams on the same optical path through the use of a polarizing beam splitter provides a shared path for the source and reference beams, allowing such pinholes to be positioned as shown in Figures 2A through 2E.

[0048] Nonlinearity in the frequency sweep of the light source can be a problem in swept-source OCT systems. Figures 2G and 2H show two embodiments that address this nonlinearity problem. All components similar to those in Figure 2C have similar reference numbers and have been described above. The embodiment of Figures 2G and 2H incorporates a second (on-board) interferometer 12, exemplarily shown to include a beam splitter 14 (where the symbol "BS" stands for beam splitter), two mirrors 20A and 20B, and a detector 16. By directing a portion of the light from the light source LtSrc1 to the interferometer 12 (e.g., an etalon or Michelson interferometer), a k-clock for triggering the SS-OCT acquisition or a reference signal can be obtained. Either of these configurations can be used to linearize the sweep (e.g., by a swept signal), the k-clock trigger directly linearizes the acquisition, and the reference signal can be used to determine and thus correct the nonlinearity. The light for generating the k-clock or reference signal can be extracted immediately after the light source using a PBS and a half-wave plate. For example, in FIG. 2G, a portion of the light from the light source LtScr1 is directed to the interferometer 12 by a half-wave plate 15A and a polarizing beam splitter PBS4. Alternatively, as shown in FIG. 2H, a portion of the light from the light source LtScr1 can be directed to the interferometer 12 by a partially transmitting mirror 20C (and optionally another quarter-wave plate 19A) in the reference arm RefArm, followed by the Michelson interferometer 12, which eliminates some parts compared to the design shown in FIG. 2G.

[0049] To avoid additional components for spatial filtering, the active areas of the photodiodes can act as spatial filters if their size is chosen appropriately: in this case, the collected light is focused onto a detector, using a small detector that is typically less than a few times the size of the focused beam.

[0050] The beam from the micro-optics package may be coupled to additional optical components (e.g., mirror scanner, beam expander, relay optics to the sample) depending on the application. To avoid reflections from these optical surfaces returning to the detector in the interferometer, the quarter-wave plate (17 in Figure 2A) in the sample path may be placed outside the microbench; one option is to place it between the last optical component and the sample. In this configuration, reflections from any components in the sample path before the quarter-wave plate will be directed away from the detector due to their polarization state.

[0051] Reflections from various optical components in the system can result in detector saturation, damage to the VCSEL or optical amplifiers, and / or artifacts or ghost images in the OCT signal. These unwanted reflections can be reduced or eliminated in a variety of ways, including but not limited to the use of pinholes and apertures, limiting the active area of ​​the detector, gluing components to reduce refractive index mismatch, anti-reflective coatings, tilted components, and polarization separation.

[0052] The OCT systems described in Figures 2A-2E (as well as Figures 2G and 2H) can avoid the use of fibers and / or semiconductor waveguides. The absence of fibers avoids signal variations due to changes in birefringence that occur when the fiber moves or when the temperature changes, and the absence of semiconductor waveguides, which typically have sub-micrometer diameters, improves light collection and propagation efficiency, as well as alignment stability, for example, when the probe is dropped or vibrated.

[0053] In conventional OCT systems, the light in the reference path is reflected back to the interferometer using a corner retroreflector. Corner retroreflectors are ideal for directing the incident light over a wide range of angles of incidence and reliably redirecting the reference light in the presence of system tolerances and misalignments. However, corner retroreflectors are expensive and difficult to manufacture at scales below 1 mm. Corner retroreflectors can also change the polarization on the wavefront if the beam is directed to the center of the component. A major advantage of the described micro-optical system is the tight tolerances in the mounting of the optical components, which may allow the use of a plane mirror instead of a retroreflector (20 in Figures 2C and 2D). If the system cannot ensure sufficient co-alignment of the sample and reference for detection in this configuration, the system can instead include a lens with a mirror placed at its focal plane in the reference path (i.e., a cat's eye retroreflector).

[0054] As mentioned above, the described system is very low cost. However, the cost of a SS-OCT system is typically determined by the cost of the tunable light source. It is therefore desirable to use a particularly inexpensive light source to enable the system to be low cost overall. Vertical-cavity surface-emitting lasers (VCSELs) are prevalent in many mass-produced applications, such as data centers, optical computer mice, distance and proximity sensors, biometric face recognition, etc., and are therefore generally very inexpensive. It has previously been shown that it is possible to tune the central wavelength by adjusting the laser drive current. Thus, such a light source or a combination of multiple such light sources is well suited for use in the systems described herein. One problem with VCSELs, particularly thermally driven VCSELs, is that the sweptable wavelength range is limited. Since the axial resolution of an OCT system is determined by the optical sweep bandwidth, it is desirable to combine multiple VCSELs with different central wavelengths to achieve a larger combined bandwidth and possibly an increased total optical output power.

[0055] 4A shows one way of combining multiple VCSELs (e.g., swept sources) 41 / 43 using a dichroic mirror 45. In this approach, light from swept source 41 passes through dichroic mirror 45 and light from swept source 43 is reflected by dichroic mirror 45. In this way, both VCSELs 41 / 43 are combined to form a combined light beam 46.

[0056] Referring to FIG. 4B, if the VCSELs 41 / 43 of FIG. 4A are operated simultaneously (which is desirable from an optical output power standpoint), it may be desirable to split their light to different detectors (47 / 49) at the detection end of the OCT via the use of another dichroic mirror 51.

[0057] Alternatively, multiple VCSELs can be operated sequentially and then light from each VCSEL (e.g., two or more VCSELs) can be detected on the same detector. Operating the VCSELs sequentially can be useful, for example, when the VCSELs have a limited duty cycle. A limited duty cycle can be the result of the VCSEL needing to cool between thermally driven sweeps, or, in the case of a MEMS VCSEL, the MEMS needing to return to an initial position to begin the next sweep.

[0058] FIG. 5 shows another method of scanning a given location in a sample tissue with multiple VCSELs covering different wavelength bands. In this example, multiple different VCSELs (e.g., VCSEL-1, VCSEL-2, VCSEL-3, and VCSEL-4) sequentially illuminate the same location on the (tissue) sample by focusing different VCSELs along a line and shifting the scan by the distance between the focused VCSELs. FIG. 5 shows a plot of time vs. (illumination) position on the tissue sample. In this way, the same given location on the sample (e.g., location Loc1) is scanned sequentially by multiple (e.g., four) VCSELs. Optionally, a combination of multiple current-tuned VCSELs can be used. For example, spectrally, two or more VCSELs can be used to sweep pairs / groups with large spectral separation in parallel and then sequentially sweep a second set. Multiple VCSELs can be linearized and an array of VCSELs can be inserted into a slot in a micro-optical bench (or semiconductor optical bench). Alternatively, one or more VCSELs can be integrated into the semiconductor wafer of semiconductor used to construct the optical bench substrate / base, as can the electronics or detectors. The use of VCSELs is particularly suited to this as they emit directly vertically from the bench, and therefore a simple mirror or rotating prism can be used to redirect the VCSEL light along the plane of the semiconductor based bench.

[0059] Another problem with VCSELs is that their optical output power is limited. Therefore, for high-quality OCT imaging of biological samples, VCSELs may be combined with semiconductor optical amplifiers. However, three aspects unique to the OCT system described herein enable the use of VCSELs for high-quality OCT imaging of biological samples without optical amplifiers, which has not been demonstrated to date.

[0060] 1. High optical efficiency free-space micro-optical interferometers. Similar optical efficiency is not possible with fiber-based designs at least in the 800 nm and 1060 nm wavelength ranges, because efficient circulators do not exist in these wavelength ranges, and so a lot of power is always lost on the path to the sample.

[0061] 2. Use of low noise detectors instead of pin and transimpedance amplifier based balanced detectors. Because the performance of the systems described herein can be significantly limited by the amount of reference light required to overcome detector noise, in contrast to state-of-the-art OCT systems that are generally not source power starved, it is desirable to use very low noise detectors. This allows shot noise limited sensitivity to be obtained using low reference powers. Thus, by appropriately adjusting the waveplate in front of the first polarizing beam splitter, most of the available optical power can be sent to the sample. A low noise detector suitable for use in the systems described herein is the electron injection detector (EI detector). Electron injection detectors exhibit low noise, which is due to their inherent amplification that is less dependent on the RF signal bandwidth.

[0062] The relative intensity noise (RIN) of the source is also usually not an issue when only a small reference power is required to overcome the detector noise as the dominant noise source. It is therefore possible to omit balanced detection in such systems and still limit the shot noise. However, it is usually still desirable to use a balanced detection configuration, since balanced detection not only suppresses RIN, but also common mode signals such as autocorrelation signals.

[0063] 3. Use of VCSEL arrays, i.e. multiple parallel beams. This multiplies the total sample optical power by the number of VCSELs in the array. Thus, for example, MEMS tunable VCSELs and optical amplifiers can be used to achieve sample powers equal to or higher than state-of-the-art OCT systems. The concept of multiplexing through the use of VCSELs and detector arrays is explained in more detail in a later section of this specification.

[0064] Another embodiment may add a partially transmissive element to the sample arm that generates a reflection that interferes with the reference beam. Since the above embodiment already has a number of optical surfaces in the sample arm, one of these optical surfaces may be used for the reflection instead of introducing an additional element. Since this reflection is closer than the sample in any case, its interference signal will have a lower frequency than the OCT signal. It can therefore be separated from the OCT signal, for example, by splitting the signal and high-pass / low-pass filtering the two copies accordingly. For example, the low frequency can be used for the reference interference signal and the high frequency can be used for the OCT signal. The reference interference signal will then be digitized in parallel and used to correct the wavenumber nonlinearity of the sweep and to phase stabilize the OCT data. Alternatively, the reference signal and the OCT signal can be digitized together and separated in digital space. This avoids the need for a second data acquisition channel.

[0065] The present invention also contemplates other aspects of the OCT system that are implemented on a micro-optical or semiconductor optical bench, or that are actually integrated into a semiconductor optical bench. For example, a MEMS mirror that scans the OCT beam can be implemented on the bench, or can be integrated into a semiconductor-based bench by photolithography. The MEMS mirror can provide the full transverse scanning capability for the OCT system, or can be one part of the system. In particular, the MEMS mirror can provide a fast scan over a limited field of view, with a more extended field of view being provided by a secondary scanning system. Limiting the field of view of a MEMS scanning system integrated on a micro-optical and / or semiconductor optical bench (e.g., to less than the full (or more extended) scanning FOV of the desired / predetermined / target of the system (e.g., a wide-field scanning system)) has several advantages. First, the angular range of the MEMS mirror is typically on the order of + / - 6 degrees, making it difficult to address the full field of view desired for a typical OCT system. In classical (e.g., bulk optics) OCT systems, a relatively large MEMS mirror can be used to image the MEMS to a demagnified spot to increase the field of view, which is more difficult in the limited space in a DIP (or other typical semiconductor package) for both the mirror and the OCT system. In addition, by limiting the size of the MEMS mirror, the speed of the scan can be increased, but at the expense of not being able to further demagnify the beam to increase the field of view. It should also be noted that the scanning speed of the MEMS mirror can be further increased through resonant scanning around one scan axis. Finally, the resulting scanning motion is beneficial due to the fast scanning of a small area that moves relatively slowly over the retina.The fact that the region of interest moves relatively (or comparatively) slowly across the retina allows for maintaining optimal performance of the OCT system by adjusting the axial scan depth, focus, and / or other aberrations such as astigmatism to match the characteristics of the retina at a given location.

[0066] One challenge in this configuration is to relay the beam from the scanner to the patient's pupil while maintaining the large working distance and compact design of the OCT module. Introducing a convergent beam onto the MEMS scanner offers flexibility in design, including the possibility of relaying the scanner with a single lens placed at a distance slightly larger than the focal length of the lens. Also, the vergence of the beam can be adjusted by translating the lens in front of the scanner, thus providing a focusing element in the design. This configuration offers a compact design with minimal components for pupil relay and focusing.

[0067] Addressing the need for high-speed scanning using mirrors integrated on a micro-optical bench / semiconductor optical bench means that the wide-field scanning system can scan at slower speeds, offering greater flexibility in its design. Examples of options enabled by the reduced scanning speed requirement include actually moving the mirrors driven by either galvanometers or electric motors, or the OCT system including the MEMS mirror across the field of view. The design of the ultra-compact OCT interferometers enabled by the micro-optical bench and semiconductor optical bench solutions makes moving the entire OCT interferometer more feasible, but this combination of small-field fast scanning (on a micro-bench) and wide-field slow scanning can also be used in more classical fiber-optic based OCT systems, where the fiber tip of the OCT sample arm, the MEMS scanner, and the small-field optics are moved as a group across the entire field of view.

[0068] When wide-field imaging is provided by moving the OCT system or fiber tip, it is desirable for the system to move along a sphere (e.g., a spherical surface / plane) centered on the pupil so as to maintain a fixed working distance relative to the pupil. In addition to the benefit of maintaining the working distance, the mechanism generating the motion on the sphere can be designed such that the elements remain parallel to the sphere surface as they move along the sphere. As a result, the OCT / optical imaging system can be mounted with its optical axis perpendicular to this element parallel to the sphere, thus ensuring that as the system is scanned across the field of view, the imaging system remains pointed at the center of the sphere where the pupil is.

[0069] It may be desirable to displace the center of the sphere slightly from the pupil during scanning for several reasons, including but not limited to: 1) To simplify alignment by allowing flexibility in pupil position relative to the center of the scan.

[0070] 2) To displace the center of the sphere behind the eye and move the mechanism for moving the position of the OCT system on the sphere away from the face and eye. 3) To displace the center of the sphere toward the eye to minimize variation in distance to the retina as it is scanned across the field of view.

[0071] If the center of the sphere is displaced relative to the pupil position, it can be important to have additional angular alignment features between the surface that remains parallel to the sphere and the axis of the OCT imaging system that needs to be pointed at the pupil during the scan. To maintain this alignment relative to the pupil, it is also desirable to have a pupil tracking component attached to the OCT imaging system that monitors the axis of alignment of the OCT system relative to the pupil and adjusts the angular alignment system to keep the OCT system pointed at the pupil.

[0072] FIG. 6 shows an example of such a system in which the camera is oriented along an axis or parallel axis relative to the OCT system. That is, FIG. 6 provides an example of a guidance system for directing the OCT imaging module to the pupil center of the eye 67. In this figure, the pupil camera and the scanning module (e.g., the OCT system) are shown jointly embodied by element 61. Feedback from this camera is used to adjust the alignment system to align the camera to the pupil, so that the OCT system is also aligned to the pupil. That is, the pupil camera may drive (e.g., provide a feedback signal to) for example, a two-axis gimbal 63 that tracks the center of the eye's pupil and provides tilt functionality to maintain the alignment of the camera and the OCT imaging module 61. In this embodiment, the gimbal 63 is attached to a movable scanning module platform (or imaging module plate) 65 that preferably provides spherical motion (e.g., motion that coincides with the surface of a sphere). In summary, the pupil camera tracks the pupil center and drives the two-axis gimbal to maintain the alignment of the camera and the OCT imaging module 61. Thus, pupil tracking can address both eye movement and misalignment caused by wide-area FOV swivel systems, thereby enabling the system to maintain alignment over a predefined area (e.g., a 2×2×2 inch (5.08×5.08×5.08 centimeter) area), which is a much larger area than traditionally required within the area where the patient's eyes must be positioned to achieve effective imaging (e.g., the pupil box).

[0073] If the alignment system is well calibrated, the camera can also be mounted directly on a parallel surface and feedback can be used to align the OCT system without affecting the camera system. In the case of cataracts, or other opacities in the pupil area, such a system can also maintain alignment to a specific location on the pupil to optimize image quality. In the absence of such opacities, the system will most likely maintain alignment of the OCT system to the center of the pupil.

[0074] FIG. 7A shows a transport system forming a spherical motion for an imaging module (e.g., a pupil camera and / or a scanning module and / or other medical imaging devices). The transport system of this embodiment includes a pivot system for scanning the imaging module according to the invention, where the acquisition angle is driven / defined by one or more rotating posts (or rods) 72 / 73, which rotate to form a spherical (or spherical) face / surface 70 (e.g., forming a spherical motion). FIG. 7A shows a particularly simple way of moving the imaging system (e.g., mounted on the imaging module plate 65) along the surface of a sphere (or partial sphere), for example, by using a pivot point 71A on the sphere displaced by 90 degrees relative to the axis of the eye, and a curved post 72 extends from this pivot point 71A along the surface of the sphere to a second pivot point 71B on the opposite side of the sphere. The post 72 is then swept across the surface of the sphere by rotating it relative to the two pivot points 71A / 71B. As shown, if the second post 73 is mounted rotated 90 degrees on the sphere relative to the first post 72 and rotated in the same way, the intersection of the two posts 72 / 73 can be located at any point on the sphere. Thus, by mounting the imaging module plate (or scanning module platform) 65 at the intersection (e.g., between) of the two posts 72 / 73, the desired motion of the platform 65 can be created, and the surface on this platform 65 can be translated to all points on the section of the sphere, always with a point parallel to the sphere surface and therefore perpendicular to the center of the sphere where the pupil will be. Note that while best mechanical performance is expected when the two posts 72 / 73 are rotated 90 degrees relative to each other on the sphere, the locations of the rotation points do not have to be 90 degrees apart. If the posts are not 90 degrees apart, all points on the sphere can still be reached, but some additional friction will be created because the force generated by rotating one post is not directly along the axis of the other post.

[0075] It may not be desirable for the pivot point to be in the same plane as the center of the sphere where the pupil should be. Since the patient's face and body are also in this plane, it may be difficult to place the pivot point at these locations without affecting the human body. As previously mentioned, one solution is to move the sphere away from the body and move both the pivot point and the sphere center in front of the eye and body. If this is done, the OCT axis alignment system may need to compensate for this offset while maintaining alignment to the pupil. This correction can be done via a tracking system that keeps the optical axis of the system aligned to the pupil, or by adding an angle-dependent offset on the alignment system that compensates for this displacement, or both. This ability to tilt and point the scan module is illustrated in FIG. 7B, which shows the displacement of the platform as one of the posts is rotated.

[0076] Alternatively, the effective pivot point can be mechanically shifted. One such example of a mechanical shift for the pivot point is shown in FIG. 7C. In this manner, clearance from surface 74 can be improved by shifting the pivot point. In this figure, the effective pivot point (e.g., pivot point 75) is shifted a given distance 77 relative to location 76. Moving the pivot point in this manner, or a similar manner, allows for a smaller portion of the sphere to be used while also allowing the rotation mechanism to be moved away from surface 74. FIG. 7D shows the displacement of the platform when one of the posts is rotated.

[0077] This approach, in which the small FOV system is moved in an arc around the pupil while maintaining alignment to the pupil, has the added benefit of greatly reducing the need to position the pupil within a very restricted area known as the "pupil box" formed by the system's optics. FIG. 8 shows that the present system 80 eliminates the requirement for a wide field ophthalmic lens 81 and corresponding pupil box 82 of conventional optical systems 83. The pupil box 81 may traditionally form a three-dimensional area of ​​space (relative to the ophthalmic device) where the patient's pupil should be to achieve effective imaging. In theory, one could add pupil tracking that moves the optics in a conventional wide field system 83, but the size and weight of the optics required to support wide field FOV imaging makes this impractical. In contrast, the present system does not have optics in close proximity to the eye (as indicated by arrow 84), and the pupil box is eliminated by flexible pointing of the optics (as indicated by arrow 85). The above described technique allows pupil tracking by moving optics with a very light weight limited optical FOV. The present invention is particularly applicable to wide field of view (>50 degrees) imaging systems where moving a heavy optical head for pupil tracking is not practical.

[0078] FIG. 9A shows another transport system according to the present invention for forming a spherical motion of the imaging module. As mentioned above, the transport system physically moves the scanning system / imaging module (or "OCT assembly" OA1) in an approximately spherical / spherical motion to scan the entire eye, but this embodiment includes a polar coordinate-based system. In this example, the above-mentioned spherical motion of the OCT assembly OA1 is provided by a spherical (or partially dome-shaped) surface or frame (Sphr) in the housing H1. Optionally, the surface Sphr may be minimally large enough to accommodate the patient's eye, and thus may be relatively small compared to a typical macroscopic OCT system. In this example, the housing H1 is exemplarily shown to be 5 inches (12.7 centimeters) high. FIG. 9A provides an interior side view (or cutaway view) v1 of the housing H1, a front view v2 of the housing H1, and an exploded view v3 showing a portion of the OCT assembly OA1 extending from the exterior of the surface Sphr to its interior along a radially curved slide (or guide) (RS1) that may be positioned along the interior curved surface of the surface Sphr. A rotor Rtr or other rotating armature / rotating mechanism may rotate the surface Sphr (e.g., around the axial center of the patient's pupil) as indicated by arrow r1. In this manner, the OCT assembly OA1 may be made to rotate unidirectionally or bidirectionally along a circular path (e.g., in the azimuth direction) at a given radial distance from the center of the surface Sphr. In addition, the OCT assembly OA1 may be made to move radially (outward or inward) from the center of the surface Sphr along a radial slide RS1 (or other radially movable carriage / holding assembly or rail system) as indicated by arrow rd1. By combination of the rotor Rtr (rotating surface Sphr) and the radial slide RS1, the OCT assembly OA1 can be positioned at any position along the spherical surface formed by the interior of the surface Sphr.

[0079] FIG. 9B provides an enlarged front and side view of the radial slide RS1 relative to the patient's eye. In this example, the OCT assembly OA1 is shown to have a rectangular front profile, while in the example of FIG. 9A, the OCT assembly OA1 is shown to have a circular front profile. It should be understood that the OCT assembly OA1 is not limited to any one configuration. As shown, the radial slide RS1 can be rotated azimuthally (e.g., by a rotor Rtr or other rotating shaft, as shown by arrow r1) around the center of the patient's pupil (as shown by dotted line Cntr) so that the OCT assembly OA1 can be moved to any position within the spherical surface formed by the surface Sphr. In this way, the OCT assembly OA1 can be maintained at a fixed distance (e.g., 2 inches or 5.08 centimeters) from the patient's pupil. In this example, a fixation target Fx1 (e.g., a mirror, a light-emitting diode, a small electronic display, etc.) is fixed to the center of the sphere aligned with the patient's pupil. Optionally, fixation target Fx1 may be made to move (or may be fixed) to any other desired position along surface Sphr.

[0080] Returning to FIG. 9A, a fixation target Fx1, which may be a mirror, is shown at the center of the surface Sphr, and may be provided by a fixation laser FL1, which eliminates the need for focusing of the fixation target Fx1. The fixation laser FL1 may project a still image or a moving image (e.g., a video) onto the fixation target Fx1. Optionally, the fixation target Fx1 may be attached to the surface Sphr and rotate with the surface Sphr or be maintained at a fixed rotation relative to the eye. Furthermore, the fixation laser FL1 may be independent of the surface Sphr, and may project the fixation target Fx1 at any internal position on the surface Sphr if the interior of the surface Sphr is reflective (e.g., has a mirror surface). In this manner, the fixation laser FL1 may project fixation target Fx1 at multiple fixed locations relative to the patient's pupil while the surface Sphr rotates, or may form a fixed path Pth1, such as a radial path opposite the radial path rd1 of the OCT assembly OA1. Other components, such as pupil alignment cameras P1, P2, and P3, may be attached to and rotate with the spherical surface Sphr.

[0081] FIG. 9C shows an exemplary scan pattern suitable for a spherical scan assembly, particularly but not limited to OCTA scanning applications. Multiple scan areas or patches (Ptch1 / Ptch2) can be created in radial and azimuth steps to form a composite circular scan area. For example, if the OCT assembly has a limited scan field of view of, for example, ±6 degrees, each scan patch can have a limited scan width (LS1) of 12 degrees. As shown, the scan patches can be composed of shorter scan patches Ptch1 and longer scan blocks Ptch2 that are radially oriented and overlap each other to form an effective larger field of view of, for example, 100 degrees (e.g., by montage or other combination). As indicated by the inward and outward arrows A1, some scan patches (e.g., shorter scan patch Ptch1) can be scanned when the OCT assembly is moved radially inward toward the center of the sphere, and other scan patches (e.g., longer scan patch Ptch2) can be scanned when the OCT assembly is moved radially outward from the center of the sphere. In this way, continuous azimuth and radial scanning by one or more scanning beams can be realized. Optionally, if the entire scanning area / region formed by the patches Ptch1 / Ptch2 is formed by the scanning field of view of the (e.g., stationary) OCT assembly, the scanning patches Ptch1 / Ptch2 can be scanned while the OCT assembly is in the corresponding stationary position before the OCT assembly moves to the next scanning position to capture the next scanning patch. As mentioned above, the OCT assembly can be composed of one or more single point scanners, line scanners, or full field scanners. As mentioned above, if the OCT assembly includes multiple scanning beams operating in parallel, the effective scanning speed of the system can be increased.

[0082] While any combination of radial and azimuthal motions can be performed to scan the eye, if the OCT system is parallelized such that there are multiple OCT scan beams incident on the eye and OCT angiography is of interest, it may be desirable to perform a series of radial scans with azimuthal rotation between them, as shown in FIG. 9C, to hold the rotation of the array fixed during each radial scan. In particular, this would ensure that there is no rotation between repeat angiography scans, because such rotation would change the horizontal and vertical spacing between the parallelized beams, making it difficult to repeat the A-scan pattern (at the same location) for angiography.

[0083] In some respects, the above-mentioned technique is similar to montage, in which a set of images is manually taken with a limited field of view device and then combined to generate a wide field of view image. In such manual techniques, the patient is typically asked to look at a fixation target, and then a series of images are taken with the fixation target in different positions. The eye is then looking in a different direction for each image, so that the images show different parts of the eye that can be montaged. The technique described herein differs both in that the fixation target does not move between the collection of subfields, and in that all of the subfields are acquired sequentially without the need for an alignment step between the acquisition of the subfields.

[0084] One challenge with montaged images is that the fixation target is within the imaging field of view for the central image, but not for the peripheral image. This can lead to the need for two fixation target systems, one in the field of view of the optics and one outside the optics. In the present system, this problem can be avoided and only one fixation target system is required to cover both the central and peripheral subfields. This can be achieved by placing the fixation target 86 behind the spherical surface 70 traversed by the imaging system (e.g., scan module or scan head) 87, as shown in FIG. 10. The small scan module 87 may temporarily block the fixation target 86 when the scan module 87 passes in front of it. That is, the fixation target 86 may be blocked when the imaging system 87 passes in front of it, but because the fixation target is designed to blink frequently, the blinking pattern can be set such that fixation is turned off when the imaging system 87 temporarily blocks the fixation target. This approach also simplifies the system by eliminating the need for optics to combine the fixation target with the imaging system. To generate a more classical montage image, multiple fixation targets (not shown) can be placed at different locations behind the scanning optics, in which case multiple images are acquired at different fixations and then combined. This can be done either with a separate complete acquisition for each image, or one target is illuminated during acquisition, followed by the next target. If one is to have different fixation positions during the acquisition of a single image, a preferred approach may be to have a single fixation target that moves during acquisition to expand the field of view obtained by the system. A single fixation target for both within and outside the field of view of the imaging optics makes this possible.

[0085] FIG. 11 shows a scan pattern 90 in which the scanning (or acquisition) field of view of the scanning module defines a region of interest 92, and arrows 91 indicate translation of the scanning module to form a region of interest scan, which allows for optimized OCT imaging. This shows another advantage of the present system compared to classical scanning systems: by continuously acquiring (scanning) a limited field of view by translating the scanning module, the system can move relatively slowly over the retina to adjust the imaging parameters of the system during acquisition to account for variations in the optical properties of the retina over the field of view. Parameters that can be adjusted during acquisition include, but are not limited to, scan depth, focus, astigmatism, polarization, aberrations, and scan range.

[0086] OCT typically uses near-infrared light for imaging, in order to avoid significant strain on the patient, and is capable of acquiring data over long periods of time, up to 30 seconds or more. However, retinal movement during acquisition can be a challenge, resulting in image distortion and / or areas of the eye missing OCT data. To address this, Heidelberg Spectralis™ OCT instruments and Zeiss Cirrus OCT instruments are being developed. A second imaging system is often used to track the retina, as is done in the Cirrus™ OCT instrument. Another relatively recent development in OCT, known as OCT angiography, images the microvasculature in the eye by detecting blood movement through repeated scans. Herein, we propose that these two functions can be combined with our novel scanning approach, by using repeated scans to both detect blood flow in the eye and measure the overall movement of the retina. Until now, OCT angiography has been performed by repeating a single B-scan, where each B-scan consists of a long (10-60 degree) line scan across the retina, where each B-scan takes about 5 ms to acquire. As the retina moves, these acquisitions do not overlap, and then a secondary Information from the tracking system is used to correct the position of the OCT scan and reacquire the data. In this case, by acquiring a limited 2D (two-dimensional) region of the eye over these 5 ms periods rather than a 1D (one-dimensional) line, the system can detect motion in 2D by identifying A-scans in the 2D region that match the repeat scans. As a simple example, if we have a 500k A-scans / sec system with a 5 ms delay between repeat scans, we can scan a 50x50 A-scan region, which corresponds to an area of ​​approximately 50x20um=1mmx1mm, and therefore track a maximum of 1mm of motion per 5 ms. Thus, the scanning technique allows the same repeat scan to be used for both OCT angiography and retinal tracking, enabling retinal tracking without the use of a secondary tracking system.

[0087] In some cases, it may be desirable to have a micro-optics based OCT system without transverse scanning capabilities, in which case transverse scanning would be provided by moving or rotating the micro-optics OCT. For example, a micro-optics OCT module can be configured without an on-board beam scanner, and instead the micro-optics OCT module (and its non-scanning OCT light beam(s)) can be dragged / moved over the surface of the skin to generate a B-scan of the skin tissue. Such a system may include optics external to the micro-optics bench or semiconductor optical bench to couple light to the sample, or the sample may be directly illuminated without additional optics. Similarly, there are applications where a micro-optics system may be used without scanning in optical correlation domain reflectometry mode. One example of such an application may be measuring the distance to a sample in a microscope to optimize the focus of the microscope.

[0088] A further aspect of the OCT system that can be integrated as part of the micropackage is focusing. Tunable lenses, sometimes called liquid lenses, have been demonstrated to provide very rapid focusing, but typically have limited clear aperture. Thus, the small beam diameters inside or close to the micropackage are well suited to such adjustable lenses. In a preferred embodiment, the adjustable lens is placed at the pupil conjugate plane.

[0089] A wider spectral tuning bandwidth can be achieved using MEMS tunable VCSELs. These devices are tuned by tuning their cavity length with MEMS elements. They exist in optically pumped and electrically pumped varieties. Optically pumped tunable MEMS VCSELs usually include at least a laser diode for optical pumping and a MEMS VCSEL. Electrically pumped tunable MEMS VCSELs usually include at least one MEMS VCSEL with an electrically driven active gain section. Both electrically and optically pumped VCSELs are often combined with optical amplifiers to increase the optical power. Optionally, MEMS tunable VCSELs can be packaged with aligned optical amplifiers. Silicon (e.g., semiconductor) optical benches can use different approaches for alignment. For example, a microscope and image recognition can be used and / or a laser beam can be sent through the system to optimize its position or intensity. These components are typically packaged separately and fiber-coupled to each other, or co-packaged on a microbench in a butterfly package. Their manufacturing process includes several active alignment steps and fiber coupling and packaging steps for each device. To further reduce the size and cost of these devices and enable higher volume manufacturing of these devices, it would be beneficial to build such devices on a silicon (semiconductor) optical bench relying on passive placement and alignment steps to benefit from the scalability of wafer-level manufacturing and packaging processes.

[0090] The VCSELs, detectors, and pinholes can all be fabricated at the wafer level as arrays with sub-millimeter / micron spacing between the elements of the array. Thus, one can configure a parallel micro-optical bench or parallel semiconductor optical bench OCT system where the VCSELs, detectors, and / or pinholes are arrays and an array of light beams from the VCSELs propagate in parallel through individual optical components of the micro-bench / silicon bench (multiple OCT light beams pass through the same optical components and each beam has at least one corresponding detector for generating an OCT signal). As an example, assuming a 3×3 array of VCSELs and a corresponding array of detectors and pinholes, one can go from one acquisition channel to nine acquisition channels, with all nine channels sharing the same lenses and mirrors and thus no additional optical components required in the OCT interferometer. One can also do this with a 1D array of VCSELs, which can be a more natural pattern for scanning, but is typically less efficient in terms of filling a lens that has a circular aperture for the light beam(s) to pass through. It is desirable to pack as many beams as possible into an optical component of a given size, giving maximum packing in any pattern. For example, a hexagonal packing with 2,3,2 = 7 beams, or 3,4,5,4,3 = 19 beam rows may be desired. As mentioned above, the optimal arrangement of the beams through the optical components may differ from the desired arrangement of the beams for scanning. In such cases, the arrangement of the beams between the OCT interferometer and the scan mirror can be changed using one or more optical components that appropriately deflect each beam.

[0091] FIG. 12 shows a configuration for converting a 2D array (e.g., 3×3 array) of light beams 101 (black dots 103 represent focused beams) into a 1D array of light beams (e.g., represented by black dots 105). The (collimated) beams 107 incident on the scan mirror 109 are line beams that all hit the scan mirror 109 at the same location, but at different angles along the line. Given a 2D array of beams 101 in an OCT interferometer, optical components would be needed between the OCT interferometer and the scan mirror 107 to convert the 2D array of beams 101 into a 1D array, as shown in FIG. 12. In this embodiment, a 2D array lens 111 (with beam deflection), a 1D array lens 113 (with beam deflection), and a lens 115 provide this conversion. A converging / diverging beam 117 is transferred between the 2D array of beams 101 and the 2D array lens 111. The collimated beam 115 is redirected between the 2D array of lenses 111 and the 1D array of lenses 113, and the converging / diverging beam 105 is redirected between the 1D array of lenses 113 and lens 115.

[0092] With reference to FIG. 13A, another way to convert the 2D rectangular array of points 121 into a set of points equally spaced along the vertical (cross-scan) direction is to simply rotate the array slightly relative to the scan direction, as shown. The black dots represent the rotated 4×4 array of points 121, the grey dots 123 represent the scanned points (e.g., the resulting scan pattern), and the arrow 125 indicates the scan direction. With reference to FIG. 13B, another way to achieve a similar effect is to use an array of VCSELs 127 arranged in the form of a parallelogram, with each row or column shifted slightly vertically relative to the scan direction 129. Again, grey dots 128 indicate the scanned points. With reference to FIG. 13C, a parallelogram array 131 is shown with different horizontal and vertical VCSEL spacing. As before, grey dots 132 represent the scanned points. Arrow 133 indicates the scan direction. It is desirable to make the 2D array approximately square (the height and width of the array are approximately equal) to maximize the use of the circular effective aperture of the lens. To achieve this, the number of VCSELs in the vertical and vertical directions may be significantly different, since the spacing between the VCSELs 131 may be significantly different between the horizontal and vertical directions.

[0093] A VCSEL array will have a given pitch (spacing between VCSELs) and beam numerical aperture (e.g., a dimensionless number that characterizes the angular range over which the system can receive or emit light). The product of numerical aperture and pitch maintains a conserved quantity when imaging the VCSEL with a single element optic. FIG. 14A provides an example of a VCSEL array 141 (e.g., size 200 μm×300 μm) with a single lens 143 between the VCSEL array 141 and the scanner 145. However, the product of the desired “pitch” or “sampling interval” and the “beam numerical aperture” on the retina may not match this conserved quantity from the VCSEL array. To address this, as shown in FIG. 14B, it may be necessary to pass the beam array 146 (e.g., from a 500 μm×600 μm VCSEL array 147) through a lenslet array (or lens array) 148, thus adjusting this conserved quantity to optimize imaging on the retina. In the example of Figure 14B, the lens array 148 reduces the divergence of the beams and increases the distance to the lens: the lateral spacing between the beams at the lens array does not change, but the lens focal length and the distance from the lens to the scanner (mirror) 145 increase.

[0094] The use of a VCSEL array increases the total sample optical power of the device according to the number of VCSELs in the array. This allows each individual channel to use lower sample power than a typical single beam OCT system and still achieve comparable or better image quality and / or imaging speed. In particular, the present invention enables the use of VCSELs for high quality OCT imaging of biological samples without optical amplifiers, which would otherwise be unproven.

[0095] Although in some of the above embodiments it has been described as advantageous to omit all optical fibers or other waveguiding optical components, some micro-optical OCT systems may include waveguides, for example as part of edge-emitting lasers, semiconductor optical amplifiers, or optical modulators. A micro-optical OCT system may further be an assembly of multiple planar waveguides and / or photonic integrated circuits (PICs) that are coupled together using micro-optical components. For example, a semiconductor optical bench assembled using wafer-level assembly and packaging steps may represent a cost-effective way to combine and package multiple optical components made from different materials into a small hermetically sealed package. This is particularly desirable when different components cannot be integrated on a single PIC due to material incompatibility, for example when combining a laser or amplifier made of GaAs with a passive silicon nitride PIC. A micro-optical OCT system is further suitable for including electronics in the same package, not only discrete analog electronic components but also electronic integrated circuits. In particular, a silicon optical bench, i.e. a system built on a silicon wafer, may enable certain large-scale electronic and optical integration, since the same silicon wafer may be processed to include electronic integrated circuits. Such systems can include passive and active optical components, as well as electronic integrated circuits for driving the light sources, signal conditioning, analog-to-digital conversion, signal processing (eg, image reconstruction), data transfer, and data storage.

[0096] In hybrid PIC / micro-optical devices, the micro-optical components do not only serve as coupling between the waveguides and / or photonic integrated circuits as described above: in some systems, it may be desirable to use the micro-optical components to perform some functions of the system and the photonic integrated circuits to perform other functions, both on a common substrate and packaged together.

[0097] Further cases where an optical fiber is desirable include an external light source fiber-coupled to the micro-optics assembly, or a fiber that collects light in the detection arm and directs the light to an external photodetector. The fiber in these cases can be, for example, a single mode fiber, a polarization-maintaining fiber, a polarizing fiber, or a dual-clad fiber.

[0098] Although the micro-optical components described herein are shown with light propagating only in a single plane, it may be desirable to direct at least one of the light beams in a direction, for example perpendicular to this plane. For example, it may be desirable to have the sample arm or the sample arm and the reference arm exit through the lid of the package rather than through a side wall. In such cases, the lid is transparent at the operating wavelength or includes a window or lens integrated into the lid.

[0099] In summary, some of the new approaches / features provided in this application include: 1) Implementing various aspects of an OCT / OCDR system on a micro-optical bench or semiconductor optical bench.

[0100] 2) Realizing a hybrid system where some macroscopic aspects of the OCT / OCDR (e.g., sample arm and reference arm) are external to the micro-optical bench or semiconductor optical bench, and the rest of the OCT / OCDR system is integrated on the micro-bench.

[0101] 3) Inclusion of components on a micro-optical bench or semiconductor optical bench, including not only an OCT / OCDR interferometer, but also scanning capabilities, for example, through the potential use of micro-electromechanical system (MEMS) mirrors mounted on the bench or integrated into the semiconductor bench through the semiconductor manufacturing process.

[0102] 4) Using optical components of the OCT / OCDR system as part of the hermetic seal of the micro-optical bench or semiconductor optical bench to minimize the optical surface. For example, if the transmission of light from the micro-optical bench or semiconductor optical bench to the outside world is not done through optical fiber, the light needs to pass through a transparent element in the transmission from the hermetic sealed OCT / OCDR engine to the outside world. Instead of using a window for this transparent element, as shown as W in FIG. 2B, a quarter-wave plate can be placed at the transition between the hermetic sealed OCT / OCDR engine and the external sample arm and the external reference arm, as shown in FIG. 2A. The quarter-wave plate then becomes part of the hermetic seal, thus eliminating the need for the window W shown in FIG. 2B. For different configurations of the OCT / OCDR, other optical components required for the operation of the OCT / OCDR can also be used at this transition point for hermetic seal.

[0103] 5) It has also been shown that free-space optical OCT / OCDR systems do not require active alignment (other than possibly any components that reside off the bench, such as reference and sample arms). This is particularly feasible with semiconductor optical benches, where component placement precision is very high. The receptacle openings in semiconductor optical benches are designed to hold the components in a predefined alignment orientation with high precision.

[0104] 6) Multiple semiconductor optical bench OCT / OCDR system assemblies can be packaged and / or tested at the wafer level. 7) Incorporation of additional IC electronics (e.g., detector electronics and analog-to-digital converter) into the semiconductor optical bench package (e.g., in the silicon substrate) may further reduce cost and enable ultra-short electrical paths to enable the high speed electronics required for ultra-high speed OCT / OCDR systems. For example, higher clock speeds may be achieved because integrated circuits built on the substrate of the semiconductor optical bench itself may avoid signal propagation delays and timing issues associated with wiring traces / wires to interconnect external discrete components.

[0105] 8) If the detector is integrated into the wafer, a polarizing beam splitter can be configured to deflect the detection path beam from horizontal to the integrated detector as shown in Figure 3. Similarly, a VCSEL integrated into the semiconductor bench can be coupled to emit light vertically directly off the bench and back into the on-bench OCT / OCDR system via a rotating prism.

[0106] 9) Mixing the analog OCT / OCDR signal with an adjustable frequency (e.g., modulated reference frequency) oscillator may allow for rapid total electronic path length adjustment. For example, the analog output from the detector may be mixed with a self-tuning oscillator to establish a desired image detection range by demodulating the analog output to a target frequency range. The self-tuning oscillator may be digitally set (and / or controlled by a feedback mechanism) to achieve fast Z tracking by achieving a target mixing frequency. This approach may also avoid the generation of Doppler shifts when changing sampling depth.

[0107] 10) The transmission of return light from the reference arm and / or sample arm may pass through one or more pinholes to appropriately remove non-interfering unwanted light (especially multiply scattered light from the sample).

[0108] 11) The transmission of light returning from the reference and sample arms may pass through a shared pinhole. This creates mode matching between the reference and sample arm light to maximize interference between the arms. This may be done either before or after the interference occurs (e.g., before or after PBS1 in FIG. 2A). Doing it before the interference, as shown in FIG. 2A, provides an advantage over a balanced detection system in which only one pinhole is needed, instead of one before each of the two detectors. In addition to reducing the number of pinholes needed, this may also improve balanced detection because using the same pinhole for the light reaching both detectors creates consistency in the spatial filtering of the light reaching the two detectors. Alternatively, the photodiode(s) themselves may act as the pinhole(s). To achieve this, for example, the diameter of the active area of ​​the photodiode(s) may be close to the diameter of the spot to be focused.

[0109] 12) The quadrature detector can be implemented on the present micro-optical bench or semiconductor optical bench without the need for active alignment. 13) A micro-optical bench OCT / OCDR system or a semiconductor optical bench OCT / OCDR system can form a handheld OCT / OCDR system without the use of optical fibers or semiconductor waveguides.

[0110] 14) The micro-optical bench or semiconductor optical bench can contain all optical components of the OCT system other than aspects of the sample arm, eliminating the need to transmit light beams other than the sample beam from the micro-optical bench or semiconductor optical bench, and optionally allowing reliance on component placement tolerances for alignment of the reference arm.

[0111] Figures 2A, 2B, 2E and 2F show a hybrid solution with external sample and reference arms. Additionally, Figure 2A shows the use of a quarter wave plate as part of a hermetic seal at the edge of a micro-optical bench or semiconductor optical bench.

[0112] Below, a description of various hardware and architectures suitable for the present invention is provided. Optical coherence tomography imaging system As mentioned above, FIG. 1A shows a schematic optical coherence tomography system suitable for use with the present invention. Various methods of creating cross-sectional images (e.g., B-scans) are known in the art, including but not limited to, along the horizontal (or X) direction, along the vertical (or Y) direction, along the X and Y diagonals, or in a circular or spiral pattern. The B-scan may be in the XZ dimension, but may also be any cross-sectional image including the z dimension. An exemplary OCT B-scan image of a normal retina of a human eye is shown in FIG. 15. An OCT B-scan of the retina provides a view of the structure of the retinal tissue. For illustrative purposes, FIG. 15 identifies various normal retinal layers and layer boundaries. The identified retinal boundary layers include (from top to bottom) inner limiting membrane (ILM) layer 1, retinal nerve fiber layer (RNFL or NFL) layer 2, ganglion cell layer (GCL) layer 3, inner plexiform layer (IPL) layer 4, inner nuclear layer (INL) layer 5, outer plexiform layer (OPL) layer 6, outer nuclear layer (ONL) layer 7, the junction between the outer segments (OS) and inner segments (IS) of photoreceptors (indicated by reference numeral 8), external limiting membrane (ELM or OLM) layer 9, retinal pigment epithelium (RPE) layer 10, and Bruch's membrane (BM) layer 11.

[0113] In OCT angiography or functional OCT, analysis algorithms may be applied to OCT data collected at different times (e.g., cluster scans) at the same or nearly the same sample location on the sample to analyze motion or flow (see, e.g., U.S. Patent Application Publication Nos. 2005 / 0171438, 2012 / 0307014, 2010 / 0027857, 2012 / 0277579, and U.S. Patent No. 6,549,801, all of which are incorporated herein by reference in their entireties). The OCT system may use any one of a number of OCT angiography processing algorithms (e.g., motion contrast algorithms) to identify blood flow. For example, motion contrast algorithms may be applied to intensity information derived from the image data (intensity-based algorithms), phase information from the image data (phase-based algorithms), or complex image data (complex-based algorithms). An en face image is a 2D projection of the 3D OCT data (e.g., by averaging the intensity of each individual A-scan, whereby each A-scan defines a pixel in the 2D projection). Similarly, an en face vascular image is an image that displays a motion contrast signal in which a data dimension that corresponds to depth (e.g., the z-direction along the A-scan) is displayed as one representative value (e.g., a pixel in the 2D projection image), typically by summing or integrating all or isolated portions of the data (see, e.g., U.S. Pat. No. 7,301,644, which is incorporated herein by reference in its entirety). OCT systems that provide angiography capabilities may be referred to as OCT angiography (OCTA) systems.

[0114] FIG. 1B shows an example of an en face vasculature image. After processing the data and highlighting the motion contrast using any of the motion contrast methods known in the art, an en face (e.g., front view) image of the vasculature may be generated by summing pixel ranges corresponding to a tissue depth from the surface of the retina's internal limiting membrane (ILM). FIG. 1C shows an example B-scan of a vasculature (OCTA) image. As shown, structural information may be less clear because blood flow traverses multiple retinal layers, which may obscure the multiple retinal layers more than in a structural OCT B-scan such as that shown in FIG. 15. Nevertheless, OCTA provides a non-invasive technique for imaging the retinal and choroidal microvasculature, which may be important for diagnosing and / or monitoring various pathologies. For example, OCTA may be used to identify diabetic retinopathy by identifying microaneurysms, neovascular complexes, and quantifying the foveal avascular zone and nonperfused areas. Moreover, OCTA has been shown to be in good agreement with fluorescein angiography (FA), a more traditional but more invasive technique that requires the injection of dye to observe vascular flow in the retina. Furthermore, in dry age-related macular degeneration, OCTA has been used to monitor the generalized reduction in choriocapillaris flow. Similarly, in exudative age-related macular degeneration, OCTA can provide qualitative and quantitative analysis of choroidal neovascular membranes. OCTA has also been used to study vascular occlusion, for example, for the evaluation of nonperfused areas as well as the integrity of the superficial and deep plexuses.

[0115] Computing Devices / Systems FIG. 1E illustrates an exemplary computer system (or computing device or computer device) according to the present invention. In some embodiments, one or more computer systems may provide functionality described or illustrated herein and / or perform one or more steps of one or more methods described or illustrated herein. The computer system may be integrated into a substrate of a semiconductor optical bench as described above, or may take any suitable physical form. For example, the computer system may be an embedded computer system, a system-on-chip (SOC), or a single-board computer system (SBC) (e.g., a computer-on-module (COM) or a system-on-module (SOM)), a desktop computer system, a laptop or notebook computer system, a mesh of computer systems, a mobile phone, a personal digital assistant (PDA), a server, a tablet computer system, an augmented / virtual reality device, or a combination of two or more of these. Where appropriate, the computer system may be in a cloud, which may include one or more cloud components in one or more networks.

[0116] In some embodiments, the computer system may include a processor Cpnt1, a memory Cpnt2, a storage Cpnt3, an input / output (I / O) interface Cpnt4, a communication interface Cpnt5, and a bus Cpnt6. The computer system may also optionally include a display Cpnt7, such as a computer monitor or screen.

[0117] The processor Cpnt1 includes hardware for executing instructions, such as those that constitute a computer program. For example, the processor Cpnt1 may be a central processing unit (CPU) or a general-purpose computing-on-graphics processing unit (GPGPU). The processor Cpnt1 may read (or fetch) instructions from an internal register, an internal cache, a memory Cpnt2, or a storage Cpnt3, decode and execute the instructions, and write one or more results to the internal register, the internal cache, the memory Cpnt2, or the storage Cpnt3. In a particular embodiment, the processor Cpnt1 may include one or more internal caches for data, instructions, or addresses. The processor Cpnt1 may include one or more instruction caches, one or more data caches, for example to hold data tables. Instructions in the instruction caches may be copies of instructions in the memory Cpnt2 or the storage Cpnt3, and the instruction caches may speed up the retrieval of these instructions by the processor Cpnt1. The processor Cpnt1 may include any suitable number of internal registers and may include one or more arithmetic logic units (ALUs). The processor Cpnt1 may be a multi-core processor or may include one or more processors Cpnt1. Although this disclosure describes and illustrates a particular processor, this disclosure contemplates any suitable processor.

[0118] The memory Cpnt2 may include a main memory that stores instructions for the processor Cpnt1 to execute processing or to hold intermediate data during processing. For example, the computer system may load instructions or data (e.g., data tables) from the storage Cpnt3 or from other sources (e.g., other computer systems) into the memory Cpnt2. The processor Cpnt1 may load instructions and data from the memory Cpnt2 into one or more internal registers or internal caches. To execute an instruction, the processor Cpnt1 may read and decode an instruction from the internal register or internal cache. During or after the execution of an instruction, the processor Cpnt1 may write one or more results (which may be intermediate or final results) to the internal registers, the internal cache, the memory Cpnt2, or the storage Cpnt3. The bus Cpnt6 may include one or more memory buses (which may each include an Azures bus and a data bus) and may couple the processor Cpnt1 to the memory Cpnt2 and / or the storage Cpnt3. Optionally, one or more memory management units (MMUs) facilitate data transfer between the processor Cpnt1 and the memory Cpnt2. The memory Cpnt2 (which may be a high-speed volatile memory) may include a random access memory (RAM), such as a dynamic RAM (DRAM) or a static RAM (SRAM). The storage Cpnt3 may include a long-term or large-capacity storage for data or instructions. The storage Cpnt3 may be internal or external to the computer system and may include one or more of a disk drive (e.g., a hard disk drive HDD, or a solid-state drive SSD), a flash memory, a ROM, an EPROM, an optical disk, a magnetic optical disk, a magnetic tape, a universal serial bus (USB)-accessible drive, or other types of non-volatile memory.

[0119] The I / O interface Cpnt4 may be software, hardware, or a combination of both, and may include one or more interfaces (e.g., serial or parallel communication ports) for communicating with I / O devices, which may enable communication with a human (e.g., a user). For example, the I / O devices may include a keyboard, keypad, microphone, monitor, mouse, printer, scanner, speaker, still camera, stylus, table, touch screen, trackball, video camera, other suitable I / O devices, or a combination of two or more thereof.

[0120] The communication interface Cpnt5 may provide a network interface for communicating with other systems or networks. The communication interface Cpnt5 may include a Bluetooth interface or other types of packet-based communication. For example, the communication interface Cpnt5 may include a network interface controller (NIC) and / or a wireless NIC or wireless adapter for communication with a wireless network. The communication interface Cpnt5 may provide communication with a WI-FI network, an ad-hoc network, a personal area network (PAN), a wireless PAN (e.g., Bluetooth WPAN), a local area network (LAN), a wide area network (WAN), a metropolitan area network (MAN), a mobile phone network (e.g., a Global System for Mobile Communications (GSM) network, etc.), the Internet, or a combination of two or more of these.

[0121] The bus Cpnt6 may provide a communication link between the above-mentioned components of the computing system. For example, bus Cpnt6 may include an Accelerated Graphics Port (AGP) or other graphics bus, an Enhanced Industry Standard Architecture (EISA) bus, a Front Side Bus (FSB), a HyperTransport (HT) interconnect, an Industry Standard Architecture (ISA) bus, an InfiniBand bus, a low-pin-count (LPC) bus, a memory bus, a MicroChannel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCIe) bus, a serial advanced technology attachment (SATA) bus, a Video Electronics Standards Association local (VLB) bus, or any other suitable bus, or a combination of two or more thereof.

[0122] Although this disclosure describes and illustrates a particular computer system having a particular number of particular components in a particular arrangement, this disclosure contemplates any suitable computer system having any suitable number of any suitable components in any suitable arrangement.

[0123] As used herein, a computer-readable non-transitory storage medium may include one or more semiconductor-based or other integrated circuits (ICs) (e.g., field programmable gate arrays (FPGAs) or application specific ICs (ASICs)), hard disk drives (HDDs), hybrid hard drives (HHDs), optical disks, optical disk drives (ODDs), magneto-optical disks, magneto-optical drives, floppy diskettes, floppy disk drives (FDDs), magnetic tapes, solid state drives (SSDs), RAM-drives, SECURE DIGITAL cards or drives, any other suitable computer-readable non-transitory storage medium, or any suitable combination of two or more thereof, as appropriate. A computer-readable non-transitory storage medium may be volatile, non-volatile, or a combination of volatile and non-volatile, as appropriate.

[0124] While the present invention has been described in conjunction with several specific embodiments, as will be apparent to those skilled in the art in light of the foregoing description, many other alternatives, modifications, and variations will be apparent. Accordingly, the invention described herein is intended to embrace all such alternatives, modifications, applications, and variations that may fall within the spirit and scope of the appended claims.

Claims

1. A medical optical tomography system for imaging an eye, comprising: A hermetically sealed micropackage comprising: i) a base supporting a light source and a beam splitter, the light source generating a beam of light and the beam splitter directing a first portion of the light to a reference arm and a second portion of the light to a sample arm; ii) the micropackage containing a transmissive element providing an interface between an inside and an outside of the micropackage, the transmissive element being along the sample arm and being at least partially transmissive to the second portion of light; a detector that receives light returning from the sample arm and the reference arm and generates a signal in response to the received light; a processor for converting the signal into image data; The system, wherein the base is a semiconductor substrate and includes a digitization circuit integrated on the base and configured to digitize a signal from the detector.

2. the optical tomography system is a swept-source optical coherence tomography (OCT) system and produces a sufficiently large imaging depth such that the eye is always within a depth imaging window of the system; the detector is contained within the micropackage; 10. The system of claim 1, further comprising a computer system configured to crop the image data and display a desired depth range within the depth imaging window on an electronic display, the desired depth range dynamically changing during a data acquisition scan.

3. The system of claim 2 , wherein the depth range is modified to follow the curvature of the eye.

4. The system of claim 2 , wherein the depth range is changed during an A-scan within a B-scan.

5. the system produces a sufficiently large imaging depth such that the eye is always within a depth imaging window of the system; the reference arm is completely enclosed within the micropackage and has an optical path length that is mismatched with an optical path length of the sample arm; 5. The system of claim 1, further comprising an optical modulator supported by the base, the optical modulator configured to shift a frequency of one of the first portion of light or the second portion of light to form a modulated OCT signal having spectral content that corresponds to a spectral content that would be obtained if the optical path length of the reference arm were more closely matched to the imaging depth.

6. the system produces a sufficiently large imaging depth such that the eye is always within a depth imaging window; the reference arm is completely enclosed within the micropackage and has an optical path length that is mismatched with an optical path length of the sample arm; The system of any one of claims 1 to 5, further comprising a frequency mixer supported by the base configured to frequency mix the signal from the detector with a frequency corresponding to an edge of the depth imaging window to generate a downmixed OCT signal having spectral components corresponding to spectral components that would be obtained if the optical path length of the reference arm more closely matched the imaging depth.

7. 7. The system of claim 5 or 6, wherein the frequency corresponding to the edge of the depth imaging window is determined by using a pre-scan sweep at a slow A-scan speed, and determining the frequency corresponding to the edge of the depth imaging window from the pre-scan sweep is followed by a faster scan sweep at a faster A-scan speed.

8. The system of claim 1 , wherein the hermetically sealed micropackage comprises a vacuum.

9. 8. The system of claim 1, wherein the hermetically sealed micropackage contains a gas that mitigates degradation of active semiconductor optical materials.

10. the beam splitter is a first polarizing beam splitter; the detector that receives light returning from the sample arm and the reference arm is a first detector; The base further comprises: a first waveplate optically coupling the light source to the first polarizing beam splitter; a second waveplate in the sample arm and a third waveplate in the reference arm; a fourth waveplate and a second polarizing beam splitter, where light returning from the sample arm and the reference arm is combined at the first polarizing beam splitter and sent through the fourth waveplate to the second polarizing beam splitter, which functions as an interference generator; 10. The system of claim 1 , further comprising: a second detector, the first detector and the second detector being coupled to the second polarizing beam splitter and generating a signal in response thereto.

11. The system of claim 10 , wherein the base further supports a pinhole in an optical path between the first polarizing beam splitter and the second polarizing beam splitter.

12. The system of claim 10 or 11, wherein the second wave plate is the transmissive element.

13. 13. The system of claim 10, wherein the first, second, third and fourth waveplates all have the same phase retardation.

14. the first wave plate and the fourth wave plate are half-wave plates; 13. The system of claim 10, wherein the second wave plate and the third wave plate are quarter wave plates.

15. 15. The system of claim 1, wherein all sample arm optical components are part of the micropackage.

16. the beam splitter is a first polarizing beam splitter; the detector that receives light returning from the sample arm and the reference arm is supported by the base and is a first detector; The base further comprises: a first waveplate optically coupling the light source to the first polarizing beam splitter; a second waveplate in the sample arm and a third waveplate in the reference arm; a fourth waveplate and a second polarizing beam splitter, where light returning from the sample arm and the reference arm is combined at the first polarizing beam splitter and sent through the fourth waveplate to the second polarizing beam splitter, which functions as an interference generator; a second detector, the first detector and the second detector being coupled to the second polarizing beam splitter and generating a signal in response to the second polarizing beam splitter; and supporting a Faraday rotator, a fifth wave plate, a sixth wave plate, a third polarizing beam splitter, a fourth polarizing beam splitter, a third detector, and a fourth detector; the Faraday rotator and the second wave plate are in an optical path between the first polarizing beam splitter and the third polarizing beam splitter; the third polarizing beam splitter directs a first portion of the light received from the first polarizing beam splitter through the fifth wave plate to a second reference arm and directs a second portion of the light received from the first polarizing beam splitter to a second sample arm; the sixth waveplate optically couples the third polarizing beam splitter to the fourth polarizing beam splitter; 10. The system of claim 1, wherein the third detector and the fourth detector receive light returning from the second reference arm and the second sample arm from the fourth polarizing beam splitter and generate signals in response thereto.

17. the beam splitter is a first polarizing beam splitter; the detector that receives light returning from the sample arm and the reference arm is supported by the base and is a first detector; The base further comprises: a first waveplate optically coupling the light source to the first polarizing beam splitter; a second waveplate in the sample arm and a third waveplate in the reference arm; a fourth waveplate and a non-polarizing beam splitter, where light returning from the sample arm and the reference arm is combined at the first polarizing beam splitter and sent through the fourth waveplate to the non-polarizing beam splitter; and a second polarizing beam splitter and a second detector, the second polarizing beam splitter receiving a portion of the light received by the non-polarizing beam splitter, the first detector and the second detector coupled to the second polarizing beam splitter and generating a signal in response thereto; 10. The system of claim 1, further comprising: a third polarizing beam splitter, a fifth wave plate, a third detector, and a fourth detector, the third polarizing beam splitter receiving a portion of the light received by the non-polarizing beam splitter through the fifth wave plate, the third detector and the fourth detector being coupled to the third polarizing beam splitter and generating a signal in response thereto.

18. 18. The system of claim 1, wherein the base further supports a fiber coupler for connecting the beam splitter to the detector.

19. the beam splitter, the reference arm, and the sample arm are part of a first interferometer; 19. The system of claim 1, wherein the base further supports a second interferometer including a second beam splitter, a first mirror, and a second mirror, and a portion of the light from the light source is directed to the second interferometer to generate a clock for linearizing a scan sweep of an OCT system.

20. 20. The system of claim 19, wherein the second interferometer is optically coupled to the reference arm of the first interferometer by a partially transmitting mirror.

21. the light source includes a plurality of lasers having different center frequencies and limited wavelength ranges; 21. The system of claim 1, wherein the base further supports at least one dichroic mirror for combining light from the multiple lasers to form a combined sweep bandwidth greater than the individual wavelength range of each laser.

22. the light source includes a plurality of lasers having different center frequencies and limited wavelength ranges, the plurality of lasers being sequentially operated to sequentially scan the same area on the eye; 21. The system of claim 1, wherein the detector sequentially detects light returned from the sample arm and the reference arm sequentially by sequential operation of the multiple lasers.

23. The micropackage is part of an imaging module, and the system comprises: A transport system that creates a spherical motion; the imaging module is coupled to the transport system and is movable by the transport system in approximately the spherical motion; 23. The system of claim 1, further comprising: a gimbal that provides tilt functionality to the imaging module for aligning the imaging module with a target point on an eye.

24. The target point is a pupil of an eye, and the system comprises:

24. The system of claim 23, further comprising a pupil camera that tracks a center of the eye's pupil and provides a feedback signal to the gimbal to maintain alignment of the imaging module.

25. 24. The system of claim 23, wherein the transport system includes a rotatable post, the rotation of the post at least partially defining the spherical motion.

26. 24. The system of claim 23, wherein the transport system includes a rotatable sphere having radial guides for moving the imaging module radially within the sphere.

27. 27. The system of claim 1, wherein the base is one of a micro-optical bench and a semiconductor optical bench.

28. 28. The system of claim 1, wherein the system is one of an optical coherence tomography (OCT) system, an OCT angiography system, and an optical correlation domain reflectometry (OCDR) system.

29. 29. The system of claim 1, wherein the base has a recessed opening on a surface configured to receive the micro-optical device at a predetermined position, height, and orientation to achieve a predetermined alignment for the micro-optical device.

30. 30. The system of claim 29, wherein the micropackage includes a lid coupled to the base, the lid having a corresponding opening on a surface opposite a surface of the base, the opening on the lid configured to receive the micro-optical device to maintain the predetermined alignment of the micro-optical device.

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