System and method for interferometry using illumination arrays

Abstract

An interferometry system including: a light source comprising an array of photo-sites arranged on a substrate, each photo-site including one or more light elements configured to emit light, wherein each photo-site is individually controllable; a processor for controlling the photo-sites; at least one optical coupling element configured to receive the light from the one or more light elements and to split the light into a plurality of optical paths comprising a reference arm and a sample arm and to recombine said optical paths; a reference arm; a sample arm including a sample configured to interact with the light; and a detector configured to detect interferograms formed by an interference between the light from the sample arm and the light from the reference arm.

Description

MGH 2025-169-02Quarles 125141.04954SYSTEM AND METHOD FOR INTERFEROMETRY USING ILLUMINATION ARRAYSCross Reference to Related Applications

[0001] The present application is based on, claims priority to, and incorporates herein by reference in its entirety for all purposes, US Provisional Application Serial No. 63 / 746,443, filed January 17, 2025.Statement of Government Support

[0002] This invention was made with government support under P41EB015903 awarded by the National Institutes of Health. The government has certain rights in the invention.Background

[0003] Interferometric techniques are widely used to detect optical path length differences between a reference field and light interacting with a sample, enabling extraction of material properties such as refractive index variations, thickness, distance, and surface topography or subsurface tomography. Unlike conventional intensity-based imaging systems, which record the spatial distribution of electromagnetic field intensity, interferometric measurements provide access to the amplitude and the phase of the sample field, thereby encoding information regarding the axial evolution of the sample signal. The depth-resolved sample structure can be encoded into the spectral dimension, or alternatively can be probed by varying the pathlength of the reference signal in combination with a low temporal coherence light source, providing volumetric sample information. However, because detectors are in practice limited to one- or two-dimensional pixel arrays, acquisition of higher-dimensional information (e.g. 3D volumetric information) generally requires mapping of one or more signal dimensions onto an alternative domain, most commonly time or wavelength.

[0004] Spectral-domain optical coherence tomography (SD-OCT) is a representative example of such an approach, wherein a broadband source illuminates a sample whose scattered light is interferometrically combined with a reference beam and the resulting spectral interferogram is detected using a spectrally resolving detection scheme employing either a ID (point-scan configuration) or 2D (line-field configuration) detector. The missing lateral spatial information isMGH 2025-169-02Quarles 125141.04954typically acquired by mechanically scanning a single illumination beam across the sample, and sequentially registering the resulting interferometric measurements to reconstruct a volumetric dataset. Similar tradeoffs between detector dimensionality and information content arise in other interferometric modalities, including time-domain interferometry and Fourier-domain (also referred to as swept-wavelength or swept-source configurations) systems, where spatial or depth information is encoded through temporal scanning or wavelength tuning. These approaches commonly rely on mechanical scanning elements that sweep an illuminating beam across the sample, leading to systems that are complex, bulky, costly, and constrained in speed, stability, and achievable illumination geometries.

[0005] Thus there is a need to integrate original light source architectures to enable cost-effective, low-complexity optical coherence tomography systems without sacrificing imaging quality.Summary

[0006] The present disclosure provides systems and methods that overcome the aforementioned drawbacks by developing illumination arrays as a light source for interferometric systems, such as OCT. Unlike conventional OCT systems that rely on single light sources, introducing a plurality of light emitters into an interferometric system removes the need for an independent scanning mechanism (e.g. mechanical scanners) and provides new illuminations strategies that can lead to improved image quality and optimized acquisition schemes.

[0007] In one aspect of the present disclosure, an interferometry system is described. The system comprises a light source comprising an array of photo-sites arranged on a substrate, each photosite including one or more light elements configured to emit light, wherein each photo-site is individually controllable, a processor for controlling the photo-sites, at least one optical coupling element configured to receive the light from the one or more light elements and to split the light into a plurality of optical paths comprising a reference arm and a sample arm and to recombine said optical paths, a reference arm, a sample arm including a sample configured to interact with the light, and a detector configured to detect interferograms formed by an interference between the light from the sample arm and the light from the reference arm.MGH 2025-169-02Quarles 125141.04954

[0008] In one aspect of the present disclosure, a method of interferometry is described. The method comprises providing a light source comprising an array of photo-sites arranged on a substrate, each photo-site including one or more light elements configured to emit light, wherein each photo-site is individually controllable, controlling, by a processor, the photo-sites, receiving, by at least one optical coupling element, the light from the one or more light elements and splitting the light into a plurality of optical paths comprising a reference arm and a sample arm and recombining said optical paths, transmitting or reflecting, by the reference arm, the light, interacting, by a sample in the sample arm, with the light, and detecting, by a detector, interferograms formed by an interference between the light from the sample arm and the light from the reference arm.

[0009] These aspects are nonlimiting. Other aspects and features of the systems and methods described herein will be provided below.Brief Description of the Drawings

[0010] The foregoing features of embodiments will be more readily understood by reference to the following detailed description, taken with reference to the accompanying drawings, in which:

[0011] FIG. 1A is a schematic of an example light source, according to aspects of the present disclosure.

[0012] FIG. IB is a schematic of an example light source, according to aspects of the present disclosure.

[0013] FIG. 1C is a schematic of an example light source, according to aspects of the present disclosure.

[0014] FIG. ID is a schematic of an example light source, according to aspects of the present disclosure.

[0015] FIG. 2A is a schematic of example light source FIG. 1A including a waveguide, according to aspects of the present disclosure.

[0016] FIG. 2B is a schematic of example light source FIG. IB including a waveguide, according to aspects of the present disclosure.

[0017] FIG. 2C is a schematic of example light source FIG. 1C including a waveguide, according to aspects of the present disclosure.MGH 2025-169-02Quarles 125141.04954

[0018] FIG. 3 is a schematic of an interferometry system, according to aspects of the present disclosure.

[0019] FIG. 4 is a schematic of an interferometry system using a one-dimensional (ID) array of light elements, according to aspects of the present disclosure.

[0020] FIG. 5 is a schematic of an interferometry system using a two-dimensional (2D) array of light elements, according to aspects of the present disclosure.

[0021] FIG. 6 is a schematic of an interferometry system using a 2D array of light elements on a flexible substrate, according to aspects of the present disclosure.

[0022] FIG. 7 is a schematic of an example processor according to aspects of the present disclosure.

[0023] FIG. 8A is a schematic of an example spectral domain-OCT system for measuring oxygen saturation of optical vasculature, according to aspects of the present disclosure.

[0024] FIG. 8B is a graph of 527nm and 560nm light as a function of horizontal pixel index, according to aspects of the present disclosure.

[0025] The drawings are not intended to define the precise proportions, dimensions, or relative sizes of the elements, but are instead presented for illustrative purposes.Detailed Description

[0026] The present disclosure provides a novel interferometric illumination architecture in which the illumination function is distributed across a plurality of individually addressable sources that are arranged and operated as a coordinated array within a shared interferometer. In contrast to conventional interferometric imaging systems that rely on a single illumination source and acquire spatial information through mechanical beam scanning, the disclosed architecture distributes the illumination function across multiple emitters, each of which can be independently controlled in space, time, and / or wavelength. In the architecture presented herein, the system can be configured such that there exists a spatial correspondence between points in the illumination array and points on the sample, thereby enabling acquisition of spatially resolved interferometric information without reliance on mechanical scanning thereby enabling illumination, detection, and reconstruction strategies that are fundamentally inaccessible to single-source interferometric system.MGH 2025-169-02Quarles 125141.04954

[0027] This array-based illumination paradigm represents a qualitative departure from prior interferometric approaches. The disclosure exploits the ability to operate many emitters in parallel, or in controlled temporal and spectral sequences, to synthesize multidimensional interferometric datasets in a manner that avoids the traditional trade-offs between detector dimensionality, acquisition speed, and system complexity. Distributing the illumination function across multiple emitters introduces system-level considerations that are absent from conventional OCT architectures, including coordination of multiple interferometric signals, preservation of interferometric contrast across the array, management of optical coupling and optical etendue, and synchronization between source operation and detector acquisition. The embodiments described below illustrate various ways in which these considerations may be addressed in practice.

[0028] Illuminator arrays have not been used in OCT systems, presumably because of a lack of suitable arrays with properties that would meet OCT requirements for producing high quality images. Micro-LEDs have been developed primarily in the context of display technology, where they are viewed as scaled-down versions of conventional LEDs optimized for high pixel density, brightness, efficiency, and color purity. Industrial development efforts have been directed toward narrowing the emission spectrum to increase color purity. This trend to reduce emitter spectral bandwidth teaches away from their use in SD-OCT. Consequently, a person of ordinary skill in the art would not have recognized the existing spectral and spatial characteristics of micro-LEDs as being advantageous for SD-OCT, nor would they have been motivated to exploit these properties in an OCT system.

[0029] Moreover, reducing the emitting area to the micrometer scale does not only render an individual micro-LED compatible with OCT due to improved spatial coherence properties but also because it enables an entirely different architecture in which multiple emitters can be used as an effective OCT illumination source. At conventional mm-scale dimensions, each LED acts as an extended, spatially incoherent source, and combining multiple such emitters would rapidly become impractical. For example, constructing an array on the order of 128 x 128 macro LEDs would result in an illumination source with excessive physical size, prohibitive thermal load, complex electrical routing, and severe optical inefficiencies. Such an array could not be readily coupled into standard OCT interferometers or optical fibers, nor could it be integrated intoMGH 2025-169-02Quarles 125141.04954clinically viable imaging systems. These practical constraints further discourage the use of multiple macro-LEDs in OCT. In contrast, when the emitting area is reduced to dimensions comparable to the fundamental mode of a single-mode waveguide, each micro-LED behaves as a quasi-point source that can be efficiently mode-matched into the interferometer. Only in this micron-scale regime does it become physically feasible to arrange a plurality of LEDs into an array whose outputs can be individually (at the pixel level) spatially controlled, temporally multiplexed, or spectrally combined without compromising OCT imaging performance. This transition from a single emitter to a plurality of emitters is therefore not an obvious scaling step, but a qualitatively different operating regime that would not have been apparent to a person of ordinary skill in the art.

[0030] Thus, the approach described herein does not represent a simple or predictable extension of prior illumination technologies for OCT. Instead, it proposes a conceptual shift in how sources for OCT are defined: from a single-aperture emitter to a spatially addressable, spectrally engineered, and temporally controlled illumination system.

[0031] FIGS. 1A-1D illustrate an example light source that may be used in any of the interferometry systems described herein. The light source 100 of FIG. 1A includes a substrate 110 on which an array 120 of photo-sites 122, 122’, 122” are arranged. The photo-sites 122, 122’, 122” may alternatively be referred to as pixels, with the terms being used interchangeably herein. In a non-limiting example, the substrate 110 includes a complementary metal-oxide-semiconductor (CMOS). The array 120 of photo-sites 122, 122’, 122” may be arranged in a ID or 2D configuration. In a non-limiting example, the array 120 may be symmetrical (e.g., 2x2, 3x3, 4x4, etc.) or asymmetrical (e.g., 2x1, 3x1, 2x3, etc.). While FIGS. 1A-1D show a side view of light sources with arrays of 3 photo-sites 122, 122’, 122” along one dimension, this depiction is purely illustrative and is not limited to a 3x1 array.

[0032] Each photo-site 122, 122’, 122” in the array 120 includes one or more light elements configured to emit light. FIGS. 1A and IB each depict a single light element at each photo-site 122, 122’, 122”, while FIGS. 1C and ID depict a plurality of light elements at each photo-site 122, 122’, 122”. The light elements may emit central wavelengths of light ranging from 300 nm to 1000 nm. In one embodiment, the light elements may emit wavelengths of light ranging from 400 nm to 800 nm. The light source 100 may further include one or more front plates 130 thatMGH 2025-169-02Quarles 125141.04954serves as an optical window for the light emitted from the light elements. In a non-limiting example, the front plate 130 is a flat glass substrate sitting atop the light elements of the array 120. For example, the front plate 130 may comprise, but is not limited to, sapphire, borosilicate or fused silica glass. FIG. ID further includes a micro-lens array 140 adjacent to the front plate 130 opposite the array of photo-sites. Such a micro-lens array 140 is configured to reshape the light emitted by each photo-site 122, 122’, 122”. The micro-lens array 140 is not limited for use with light source 100’”, and may be included in any of the light sources 100, 100’, and 100”. The micro-lens 140 array and the front plate 130 may form a single piece.

[0033] In a non-limiting example in which the light elements are fabricated with asymmetric emitting areas, such as rectangular geometries, the light elements are configured to leverage or compensate for the resulting optical anamorphism. For example, micro-optics may independently shape the numerical aperture or beam divergence along orthogonal axes to produce a symmetric beam profile, or alternatively to intentionally generate an anisotropic illumination profile suited for line-field, projected-field, or other OCT imaging modalities.

[0034] As shown in FIG. 1 A, the light elements may emit substantially identical central emission wavelengths. Alternatively, light elements may have substantially identical central emission wavelengths, but different bandwidths.

[0035] As shown in FIG. IB, light source 100’ may include light elements 125, 126, and 127 with different central emission wavelengths. FIG. 1C depicts another alternative light source 100” wherein each photo-site 122, 122’, 122” in the array 120 comprises a plurality of the light elements 125, 126, and 127 with different central emission wavelengths and optionally different spectral bandwidths stacked along an axis that is perpendicular to the substrate 110 of the array 120. In other words, at each photo-site 122, 122’, 122”, multiple light elements are stacked on top of each other at a single position on the array 120. In the non-limiting example of FIG. 1C, the three light elements 125, 126, 127 may correspond to a red central emission wavelength, green central emission wavelength, and blue central emission wavelength, respectively. As will be described in further detail below, by individually controlling the light elements 125, 126, and 127 in FIG. 1C, the central emission wavelengths of each photo-site 122, 122’, 122” can be adjusted.MGH 2025-169-02Quarles 125141.04954

[0036] In a non-limiting example, the light source 100” in FIG. 1C may also include a plurality of light elements emitting the same wavelength at any given photo-site (not shown). In such a configuration, the radiant power may be increased. Alternatively, light elements may have substantially identical central emission wavelengths, but different bandwidths.

[0037] It is noted that the number of light elements stacked at a given photo-site 122, 122’, 122” is not limited to three as depicted in FIGS. 1C-1D. Rather, the number of elements at each photosite may be one or more.

[0038] In a non-limiting example, each of the photo-sites 122, 122’, 122” in the array 120 may be mutually spatially incoherent and mutually temporally incoherent relative to each other.

[0039] The light elements may include light emitting diodes (LEDs), lasers (such as laser diodes), wavelength-swept source lasers (such as vertical cavity surface emitting lasers), super-luminescent diodes (SLEDs), or the like.

[0040] In a non-limiting example, the array 120 may comprise mini-scale or micro-scale LEDs, wherein each mini-LED produces light emission areas less than 200 pm and each micro-LED produces light emission areas less than 20 pm in a first direction. For example, a light element may emit an area of light with a lateral extent along one direction of less than 100 pm, less than 50 pm, less than 20 pm, less than 10 pm, or any value therebetween. In addition, the typical spectral bandwidth of a single micro-LED with a central wavelength of 475 nm is around 20 nm, which corresponds to an OCT axial resolution of about 5 pm in air (~3.7 pm in water). Thus, their temporal coherence characteristics are very close to those found in SLEDs conventionally used in SD-OCT in the near infrared. In comparison to SLEDs, arrays of micro-LEDs are readily fabricated on wafers that can be interconnected with CMOS technology for driving the individual micro-LEDs.

[0041] As described herein, the use of mini-LEDs or micro-LEDs provides the ability to support a scalable, spatially addressable illumination array, while also providing secondary advantages such as compact form factor, electronic controllability, and reduced system complexity, particularly at visible and near-infrared wavelengths. These attributes make mini-LED and micro-LED arrays particularly attractive for interferometric imaging systems operating at visible wavelengths, where source availability, system footprint, complexity, and cost have historically limited practical implementation.MGH 2025-169-02Quarles 125141.04954

[0042] Furthermore, mini- and micro-LEDs have sub-nanosecond response times, enabling fast switching. Also, mini- and micro-LED arrays can be driven to create complex spatial and temporal patterns for projection onto the sample of interest. In addition, the central emission wavelength of micro-LEDs can be tuned either at the fabrication stage or, after fabrication, by changing their current during operation, making them suitable for Fourier-domain (swept- source) configurations. Also, the spectral bandwidth of micro-LEDs can be further increased during fabrication, and / or narrowed through colored filters.

[0043] Alternatively, other classes of solid-state light emitters may also be used as illuminators in interferometric systems comprising a plurality of individually addressable illumination sources. For example, vertical-cavity surface-emitting lasers (VCSELs) have been fabricated at the microscale and integrated into dense 2D arrays in which individual emitters can be independently addressed. VCSEL arrays can provide compact, electronically controlled illumination sources with emission characteristics suitable for interferometric imaging. In particular, they may be operated in swept-source configurations, including by sequential activation of emitters having different emission wavelengths, by electronic tuning of the emission wavelength of one or more emitters, or by a combination thereof.

[0044] The light emitted from each photo-site 122, 122’, 122” may be propagated in free space. Alternatively, as in FIGS. 2A-2C, light sources 200-200” show the light sources 100-100” coupled to a plurality of waveguides 210, each waveguide coupled to the front plate 130 at each photo-site 122, 122’, 122” of the array 120. The light emitted from each of the photo-sites 122, 122’, 122” in the array 120 may be coupled in free space into a waveguide (e.g. an optical fiber), with or without the use of coupling optics such as micro-lenses, or can be directly butt-coupled into a waveguide. FIGS. 2A-2C illustrate the butt-coupled configuration. In an embodiment using micro-LEDs as the light elements, their size is approximately equal to the core diameter of a single-mode fiber.

[0045] In a further embodiment, the waveguides could be fabricated directly on top of the substrate 130, or fabricated separately and coupled onto the substrate.

[0046] In a further embodiment, free-space coupling of the photo-site emission is engineered using micro-optical elements, such as the micro-lens array 140 shown in FIG. ID or diffractive optical elements, positioned on (directly fabricated on) or in proximity to the light elements.MGH 2025-169-02Quarles 125141.04954These optical elements may control the numerical aperture, divergence, and spatial distribution of the emitted light in order to optimize coupling efficiency into downstream optics or waveguides, increase usable illumination power at the sample.

[0047] Light source architectures 200-200’ ’ may further include optical combiners 220, for merging the light propagating through each of the waveguides 210 into single or a reduced number of outputs.

[0048] Referring now to FIG. 3, an example interferometry system 300 using any one of the light sources 200-200” is shown. It is noted, that while FIG. 3 shows any one of light sources 200-200” being used in the system, any one of light sources 100-100’” may also be used without the waveguides 210. The system 300 includes an optical coupling element 310 such as a splitter configured to receive light emitted from the light elements in the photo-site array 120 and split the light into a plurality of optical paths comprising the reference arm 320 and a sample arm 330.

[0049] The reference arm 320 may include a reflective component such as a mirror for reflecting the light back toward the optical element 310. The sample arm 330 may include various optical components such as a lens 331 to couple the light into free space toward a 2D scanner 332, which further directs the beam through a scan lens 334 and onto the sample 336. Alternatively, the 2D scanner 332 may be fixed, with scanning across the sample being controlled by the control of the various light elements of the photo-site array 120. Scattered light from the sample is collected by the sample arm 330 and back toward the optical element 310. The scattered light from the sample arm 330 interferes with the reflected light from the reference arm 320 in the optical element 310 also serving as a coupler, thereby forming interferograms that may be detected by detector 340.

[0050] In a non-limiting example, the light source may comprise an array of photo-sites including micro-LED light element used in an OCT systems including spectral-domain OCT, swept-source OCT, and time-domain OCT architectures. The micro-LED array provides spatially, temporally, and spectrally controlled illumination.

[0051] In some embodiments, micro-LED light elements are used in a spectral-domain OCT system, wherein broadband illumination from one or more micro-LEDs interferes with a reference beam and the resulting interference spectrum is detected using a spectrally resolvingMGH 2025-169-02Quarles 125141.04954detection scheme (typically a grating and a camera). Depth-resolved information is obtained by Fourier transformation of the detected spectral interferogram by a spectrometer, while spatial information is acquired using point-scanning, line-field, projected-field, or full-field illumination geometries enabled by the micro-LED array.

[0052] In some embodiments, the micro-LED light elements are used in a time-domain OCT system, wherein depth-resolved information is obtained by scanning the optical path length between the reference and sample arms. The micro-LED array provides spatially controlled illumination including point, line-field, or full-field imaging, while interferometric signals are detected using single-element or multi-element detectors. Time-domain OCT imaging may be implemented in full-field-OCT fashion to obtain an en-face image at a given sample depth.

[0053] In some embodiments, swept-source OCT operation is achieved using a micro-LED array comprising a plurality of emitters with incrementally offset central emission wavelengths, wherein the micro-LEDs are sequentially activated in time to produce a wavelength sweep without mechanically tunable optical elements. For example, in a line-field configuration, one dimension of a 2D micro-LED array corresponds to spatial illumination on the sample, while an orthogonal dimension comprises a series of micro-LEDs with differing central wavelengths, such that sequential activation along the wavelength dimension produces a swept-source illumination at each spatial position.

[0054] Wavelength sweeping can be achieved partially by tuning the drive current applied to individual micro-LEDs or VCSELs, thereby shifting their central emission wavelengths during operation. In such embodiments, the wavelength sweep may be produced by sequentially activating micro-LEDs or VCSELs with different central wavelengths, by dynamically tuning the emission wavelength of one or more emitter via current modulation, or by a combination of array -based wavelength stepping and current-induced wavelength tuning.

[0055] While system 300 depicts a Michelson-type interferometry system in which an optical coupling element 310 both divides the light into reference and sample optical paths (arms) and recombines the light returned from said optical paths, other interferometry architectures are also considered, such as a Mach-Zehnder interferometry system. For example, in a Mach-Zehnder interferometer, the light may be divided and recombined using a plurality of optical coupling elements. Specifically, a first optical coupling element may split the light from the light elementsMGH 2025-169-02Quarles 125141.04954into the reference and sample optical paths, while a second optical coupling element recombines the light from the reference and sample optical paths. The detector likewise detects the interferogram resulting from the interference between the recombined optical paths. Various optical elements may be included to direct, couple, or condition light between the optical paths, optical coupling elements, and the detector.

[0056] FIGS. 4-6 show similar interferometry systems to that of FIG. 3 with different example light source array configurations.

[0057] In the interferometry system 400 of FIG. 4, the array is a ID array 402 of light elements 404 for projecting a line-field illumination on the sample plane 436. The light 406 emitted from the array is coupled in the interferometry system though optical splitter / coupler 410 to direct the light to a reference arm 420 and a sample arm 430. In a line-field configuration, the illumination can be scanned using a scanning unit 432 and focused using a scan lens 434 on the sample plane 436 to a form scanning line at positions 438, 438’, and 438” as it moves across the area to be imaged. FIG. 4 shows three line field illumination positions for simplicity, but the number of positions is not limited thereto. The scattered light from the sample is routed back to interfere with the reflected beam from the reference arm and form an interferogram recorded by a detector 440.

[0058] FIG. 5 shows an interferometry system 500 with a light source comprising a 2D array 502 of light elements 504 to project a line-field illumination on the sample plane 536 through sequential activation of lines of photo-sites. The light 506 emitted from the array is coupled in the interferometry though optical splitter / coupler 510 to direct the light to a reference arm 520 and a sample arm 530. In this line-field configuration, the illumination is relayed using fixed optics (no scanning unit) 532 and focused using a scan lens 534 on the sample plane 536 to form sequentially activated lines at positions 538, 538’, and 538” spanning the area to be imaged. FIG. 5 shows three line field illumination positions for simplicity, but the number of lines formed is not limited thereto. The scattered light from the sample is routed back to interference with the reflected beam from the reference arm and form an interferogram recorded by a detector 540.

[0059] Alternatively, interferometry system 500 may include a scanning unit 432 as in FIG. 4. In this configuration, smaller regions of the sample 536 are scanned via the sequential activation ofMGH 2025-169-02Quarles 125141.04954light elements 504 of the 2D array 502, while the scanning unit 432 extends the overall area of the sample 536 that can be scanned.

[0060] In another example of system 500 including scanning unit 432, the scanning unit 432 may also provide a small shift in the projected region to allow for sub-pixel resolution. For example, the shift may be less than the pixel pitch between adjacent light elements 504.

[0061] FIG. 6 shows an example interferometry system 600 using a flexible 2D array 602 of light elements 604 to project a line field illumination matching the shape of the sample. The flexible 2D array 602 may be curved, or otherwise shaped to provide uniform or geometry-adapted illumination and improve optical coupling efficiency. The light 606 emitted from the light elements 604 is coupled in the interferometry system though optical splitter / coupler 610 to direct the light to a reference arm 620 and a sample arm 630. In this line-field configuration, the illumination relayed using fixed optics (no scanning unit) 632 and focused using a scan lens 634 on the sample 636 to form sequentially activated lines at positions 638, 638’, and 638” spanning the area to be imaged. The flexible array is shaped such that the image of the photo-sites 639 is conformal to the sample (e.g. a cornea 636) hence optimizing the illumination intensity at the sample surface. The scattered light from the sample is routed back to interference with the reflected beam from the reference arm and form an interferogram recorded by a detector 640.

[0062] Alternatively, interferometry system 600 may include a scanning unit 432 as in FIG. 4. In this configuration, smaller regions of the sample 636 are scanned via the sequential activation of light elements 604 of the 2D array 602, while the scanning unit 632 extends the overall area of the sample 636 that can be scanned.

[0063] In another example of system 600 including scanning unit 432, the scanning unit 432 may also provide a small shift in the projected region to allow for sub-pixel resolution. For example, the shift may be less than the pixel pitch between adjacent light elements 604.

[0064] As alluded to above, the individual light elements of the various light sources are individually controllable or addressable. An example processor 700 for such control of the individual light elements is shown in FIG. 7 and is electrically coupled to the systems shown in FIGS. 3-6. The processor 700 may individually control an emission activation of each individual light element (On / Off) to control an emission activation and wavelength at a given photo-site. For example, in a system using light source 100’, where light elements 125, 126, and 127 eachMGH 2025-169-02Quarles 125141.04954have different central emission wavelengths, the processor may activate any combination of the three light elements. In an example system using light source 100”, individually activating the light elements in the stack of light elements at each photo-site will affect the activation, power, and emission wavelength at each photo-site. For example, in each stack of light elements in FIG.1C, any combination of elements may be activated, leading to a wide expansion of the possible emission patterns by the light source.

[0065] The processor may further control the wavelength of each individual light element. For example, if the light elements are LEDs, the processor may set a current level to each individual LED to adjust the wavelength. If instead, the light elements are swept laser sources, the processor may adjust the emission wavelength of the lasers individually.

[0066] As will be described in further detail below, the processor may also control the individual light elements for various temporal and spatial patterns of the array of photo-sites for various illumination geometries.

[0067] In a non-limiting example, OCT imaging employs projected-field or line-field illumination geometries, in which a desired illumination pattern is formed on the sample using a single micro-LED or a plurality of micro-LEDs. For example, line-field OCT may be achieved using a plurality of micro-LEDs arranged in a line, or by using at least two rectangular micro-LEDs in which one lateral dimension is micrometric, thereby maintaining one-dimensional spatial coherence along the short axis.

[0068] Furthermore, generalization of line-field imaging is also possible, such as, but not limited to, random mask imaging, Hadamard basis mask imaging, full-field imaging, etc.

[0069] Line and generalized mask scanning can be achieved either by opto-mechanical methods (beam deflector, galvanometer scanner) for systems such as system 400 described above or by using a 2D array and electronically switching on and off different lines of the 2D array as shown in FIGS. 5 and 6.

[0070] The processor 700 may also synchronize illumination from the array of photo-sites with the rolling of a shutter of a detector to enable high-speed imaging with full- or partial-confocal gating.

[0071] In embodiments using a 2D detector, the processor 700 may control light element illumination patterns such that they are activated in a sparse or sub-area illumination mode, inMGH 2025-169-02Quarles 125141.04954which, at any given time, only a single light element or a small, non-adjacent subset of light elements corresponding to a single spatial pixel or spatially separated pixels on the sample is illuminated, while all other light elements remain off. The illumination is then sequentially shifted to another light element or subset of light elements in time.

[0072] In this embodiment, the illumination sequence is designed such that adjacent or nearby spatial locations on the sample are not illuminated simultaneously, thereby reducing spatial mixing and reconstruction cross talk arising from multiple scattering. This can be accomplished by identifying the pixels in the detector that correspond only to active illumination array pixels, thus ignoring light that has suffered significant scattering and emerges from the sample at an offset lateral location. Another approach to reduce cross talk can rely on multiplexed / encoded illumination, that allows the OCT system to differentiate from single backscattered light and multiply backscattered light that propagated from a different illuminator array pixel that uses a different illumination code.

[0073] The sparse illumination pattern can follow deterministic or pseudo-random sequences, including raster scanning, interleaved scanning, or checkerboard patterns. The activation order may be optimized based on detector characteristics, sample scattering properties, or desired imaging speed.

[0074] This embodiment is particularly advantageous to reduce cross-talk in full-field and projected-field OCT (e.g. line-field SD-OCT) configurations employing 2D detection, in which spatial information from multiple illumination sites is simultaneously integrated at the detector.

[0075] In some embodiments, illumination from individual light elements or groups of light elements is temporally modulated to encode spatial information. Temporal modulation may include pulse-width modulation, amplitude modulation, or on / off modulation, wherein different light elements or illumination patterns are assigned distinct temporal or modulation-frequency signatures.

[0076] When multiple light elements or illumination patterns are active simultaneously, the detected OCT signals comprise a superposition of contributions from different spatial locations. The temporal or frequency encoding enables these contributions to be separated during signal reconstruction using frequency-domain analysis, lock-in detection, or other temporal demodulation techniques.MGH 2025-169-02Quarles 125141.04954

[0077] This temporal or frequency encoding enables multiplexed OCT acquisition, allowing simultaneous illumination of multiple spatial locations while preserving separability, thereby increasing acquisition speed and reducing or eliminating the need for mechanical beam scanning.

[0078] In further embodiments, temporal or frequency encoding enables the use of detectors with reduced dimensionality relative to the dimensionality of the illuminated field.

[0079] For instance, a 2D light field resulting from ID line-field illumination and wavelength dispersion at the spectrometer can be collapsed along the spatial dimension onto a ID camera. Each ID camera frame contains a superposition of signals from multiple spatial locations, which are separated after acquisition of multiple frames based on their temporal or frequency encoding. The same is possible for a 2D projected-field patterns for imaging three-dimensional (3D) (2D spatial + ID spectral) information onto a 2D detector.

[0080] In a further embodiment, the array of photo-sites is optically imaged onto a spatial light modulator (SLM, not shown) such that the emitting plane of the array is conjugated to the modulation plane of the SLM. In this configuration, the SLM applies spatially varying phase modulation to the illumination wavefront prior to interaction with the sample.

[0081] The phase modulation may be used to encode illumination originating from different photo-sites, spatial regions, or illumination patterns with distinct phase signatures. The detected OCT interferometric signals corresponding to different phase encodings are subsequently separated during signal reconstruction, thereby reducing reconstruction cross talk and enabling multiplexed acquisition with reduced detector dimensionality, including collapse of spatial or pattern dimensions onto fewer detector pixels.

[0082] Moreover, the applied phase patterns may be deterministic or pseudo-random and may be static or dynamically varied during acquisition. Phase decoding may be performed by the processor using phase-sensitive demodulation of OCT signals. The combined amplitude modulation by the light elements and phase encoding by the SLM enables multiplexed OCT acquisition.

[0083] Furthermore, the illumination may be linearly polarized prior to reaching the spatial light modulator such that the SLM applies a controllable phase delay without substantially affecting amplitude.MGH 2025-169-02Quarles 125141.04954

[0084] In a further embodiment, the spatial light modulator is operated in a polarizationmodulation mode, in which the SLM applies a spatially varying polarization retardance to encode illumination originating from different photo-sites, spatial regions, or illumination patterns with distinct polarization states. In such embodiments, the detected OCT signals are acquired using polarization-sensitive detection and are separated during reconstruction based on their polarization signatures. Polarization encoding may be used independently or in combination with phase or temporal encoding to improve separability of multiplexed illumination channels, depending on sample properties.

[0085] In a non-limiting example application, line-field SD-OCT may be used for ocular vascular saturation determination (FIGS. 8A-8B). There is strong interest in cross-sectional and depth-resolved imaging of biological tissues at visible wavelengths, as these wavelengths can provide enhanced resolution and contrast and quantitative sensitivity to endogenous absorbers such as oxygenated and deoxygenated hemoglobin or exogenous absorbers. FIG. 8A shows how the dispersed spectrum of a two-color array made up of a ID line array of micro-LEDs with a 527 nm central emission wavelength and a ID line array of micro-LEDs with a 560 nm central emission wavelength would appear on the camera in the absence of interferences (FIG. 8B). Oxyhemoglobin and deoxyhemoglobin absorbs the 527 nm light to a similar degree, while both deoxyhemoglobin absorb about two times more light at 560 nm than oxyhemoglobin. Images obtained at these two wavelengths allow the quantitative computation of the species concentration ratios. In this example, a line is projected from each ID line array on the eye and a ID scanner is used for transverse scanning across the anterior surface of the eye. Returning scattered light is dispersed using a grating onto a 2D camera wherein one axis is spectral, and the other is spatial. A processor may further process the detected signals for image processing or generating oxygen saturation maps or reports.

[0086] By controlling the photo-sites to emit one or more wavelengths configured to allow spectral unmixing of oxygenated and deoxygenated hemoglobin, relative and / or total concentrations of oxygenated hemoglobin, deoxygenated hemoglobin, or both may be determined. In a non-limiting example, the light source includes two or more sets of photo-sites configured to emit light at two or more central emission wavelengthsMGH 2025-169-02Quarles 125141.04954

[0087] As used in this specification and the claims, the singular forms “a,” “an,” and “the” include plural forms unless the context clearly dictates otherwise.

[0088] As used herein, “about”, “approximately,” “substantially,” and “significantly” will be understood by persons of ordinary skill in the art and will vary to some extent on the context in which they are used. If there are uses of the term which are not clear to persons of ordinary skill in the art given the context in which it is used, “about” and “approximately” will mean up to plus or minus 10% of the particular term and “substantially” and “significantly” will mean more than plus or minus 10% of the particular term.

[0089] As used herein, the terms “include” and “including” have the same meaning as the terms “comprise” and “comprising.” The terms “comprise” and “comprising” should be interpreted as being “open” transitional terms that permit the inclusion of additional components further to those components recited in the claims. The terms “consist” and “consisting of’ should be interpreted as being “closed” transitional terms that do not permit the inclusion of additional components other than the components recited in the claims. The term “consisting essentially of’ should be interpreted to be partially closed and allowing the inclusion only of additional components that do not fundamentally alter the nature of the claimed subject matter.

[0090] The phrase “such as” should be interpreted as “for example, including.” Moreover, the use of any and all exemplary language, including but not limited to “such as”, is intended merely to better illuminate the disclosure and does not pose a limitation on the scope of the disclosure unless otherwise claimed.

[0091] Furthermore, in those instances where a convention analogous to “at least one of A, B and C, etc.” is used, in general such a construction is intended in the sense of one having ordinary skill in the art would understand the convention (e.g., “a system having at least one of A, B and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together ). It will be further understood by those within the art that virtually any disjunctive word and / or phrase presenting two or more alternative terms, whether in the description or figures, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A andB.”MGH 2025-169-02Quarles 125141.04954

[0092] All language such as “up to,” “at least,” “greater than,” “less than,” and the like, include the number recited and refer to ranges which can subsequently be broken down into ranges and subranges. A range includes each individual member. Thus, for example, a group having 1-3 members refers to groups having 1, 2, or 3 members. Similarly, a group having 6 members refers to groups having 1, 2, 3, 4, or 6 members, and so forth.

[0093] The modal verb “may” refers to the preferred use or selection of one or more options or choices among the several described embodiments or features contained within the same. Where no options or choices are disclosed regarding a particular embodiment or feature contained in the same, the modal verb “may” refers to an affirmative act regarding how to make or use an aspect of a described embodiment or feature contained in the same, or a definitive decision to use a specific skill regarding a described embodiment or feature contained in the same. In this latter context, the modal verb “may” has the same meaning and connotation as the auxiliary verb “can.”

[0094] Thus, while the invention has been described above in connection with particular embodiments and examples, the invention is not necessarily so limited, and that numerous other embodiments, examples, uses, modifications and departures from the embodiments, examples and uses are intended to be encompassed by the claims attached hereto.

Claims

MGH 2025-169-02Quarles 125141.04954ClaimsWhat is claimed is:

1. An interferometry system comprising:a light source comprising an array of photo-sites arranged on a substrate, each photo-site including one or more light elements configured to emit light,wherein each photo-site is individually controllable;a processor for controlling the photo-sites;at least one optical coupling element configured to receive the light from the one or more light elements and to split the light into a plurality of optical paths comprising a reference arm and a sample arm and to recombine said optical paths;a reference arm;a sample arm including a sample configured to interact with the light; anda detector configured to detect interferograms formed by an interference between the light from the sample arm and the light from the reference arm.

2. The system of claim 1, wherein there exists a spatial correspondence between a sample location and one or more photo-sites.

3. The system of claim 1, wherein each photo-site comprises a plurality of the light elements stacked along an axis that is perpendicular to the substrate of the array.

4. The system of claim 3, wherein each light element in each of the photo-sites has a different central emission wavelength.

5. The system of claim 4, wherein the processor individually controls the plurality of light elements to control an emission wavelength of the photo-sites.

6. The system of claim 1, wherein the processor further individually controls an emission wavelength of the light elements by adjusting a current to each of the light elements.MGH 2025-169-02Quarles 125141.049547. The system of claim 1, wherein the processor individually controls the light elements to control one or more of an emission activation or a wavelength of each of the photo-sites.

8. The system of claim 7, wherein the processor generates one or more of spatial patterns or temporal patterns by controlling the emission activation of the photo-sites, wherein the one or more of the spatial patterns or temporal patterns are projected onto the sample.

9. The system of claim 1, wherein each of the one or more light elements has a light emitting area of less than 200 pm in a first direction.

10. The system of claim 9, wherein each of the one or more light elements has a light emitting area of less than 100 pm in a first direction.

11. The system of claim 9, wherein each of the one or more light elements has a light emitting area of less than 50 pm in a first direction.

12. The system of claim 9, wherein each of the one or more light elements has a light emitting are of less than 20 pm in a first direction.

13. The system of claim 9, wherein each of the one or more light elements has a light emitting area of less than 10 pm in a first direction.

14. The system of claim 1, wherein each of the one or more light elements emits light of central wavelengths of 300 nm to 1000 nm.

15. The system of claim 1, wherein each of the one or more light elements emits light of central wavelengths of 400 nm to 800 nm.

16. The system of claim 1, wherein each of the one or more light elements includes a light emitting diode (LED) or a laser.

17. The system of claim 1, wherein the interferometry system includes an optical coherence tomography (OCT) system.

18. The system of claim 17, wherein the OCT system includes a spectral domain-OCT (SD-OCT) system.

19. The system of claim 18, wherein the detector includes a spectrometer.MGH 2025-169-02Quarles 125141.0495420. The system of claim 17, wherein the OCT system includes a swept source-OCT (SS-OCT) system.

21. The system of claim 17, wherein the OCT system includes a time domain-OCT (TD-OCT) system.

22. The system of claim 1, further comprising a plurality of waveguides coupled to the photosites, wherein the light propagates through the waveguides.

23. The system of claim 1, further comprising a plurality of optical members coupled to the photo-sites, wherein the light propagates through the optical members.

24. The system of claim 23, wherein the plurality of optical members includes a micro-lens array configured to reshape the light.

25. The system of claim 1, wherein the light source is flexible and configured to conform to a non-planar surface of the sample.

26. The system of claim 1, wherein the detector is a 2D detector.

27. The system of claim 26, wherein the 2D detector includes a rolling shutter that is controllable by the processor.

28. The system of claim 27, wherein the processor synchronizes control of the photo-sites with the rolling shutter.

29. The system of claim 1, wherein an activation of the light elements includes temporal modulation by the processor.

30. The system of claim 29, wherein the temporal modulation includes one or more of pulsewidth modulation, amplitude modulation, and on / off modulation.

31. The system of claim 1, further comprising a spatial light modulator (SLM), wherein the light from the array is emitted onto the SLM to apply spatially varying phase modulation to the light before reaching the sample.

32. The system of claim 31, where the SLM further applies varying polarization retardance to encode light originating from each of the photo-sites.MGH 2025-169-02Quarles 125141.0495433. The system of claim 1, wherein the array of photo-sites is one-dimensional (ID) or two-dimensional (2D).

34. The system of claim 1, wherein the processor further controls the photo-sites to emit one or more wavelengths configured to allow spectral unmixing of oxygenated hemoglobin and deoxygenated hemoglobin to determine one or more of relative concentrations or total concentrations of oxygenated hemoglobin, deoxygenated hemoglobin, or a combination thereof.

35. The system of claim 34, wherein the processor further produces one or more maps of oxygen saturation.

36. The system of claim 34, wherein the light source includes two or more sets of photo-sites configured to emit light at two or more central emission wavelengths.

37. A method of interferometry comprising:providing a light source comprising an array of photo-sites arranged on a substrate, each photo-site including one or more light elements configured to emit light, wherein each photo-site is individually controllable;controlling, by a processor, the photo-sites;receiving, by at least one optical coupling element, the light from the one or more light elements and splitting the light into a plurality of optical paths comprising a reference arm and a sample arm and recombining said optical paths;transmitting or reflecting, by the reference arm, the light;interacting, by a sample in the sample arm, with the light; anddetecting, by a detector, interferograms formed by an interference between the light from the sample arm and the light from the reference arm.

38. The method of claim 37, wherein there exists a spatial correspondence between a sample location and one or more photo-sites.

39. The method of claim 37, wherein each photo-site comprises a plurality of the light elements stacked along an axis that is perpendicular to the substrate of the array.MGH 2025-169-02Quarles 125141.0495440. The method of claim 39, wherein each light element in each of the photo-sites has a different central emission wavelength.

41. The method of claim 40, further comprising individually controlling, by the processor, the plurality of light elements to control an emission wavelength of the photo-sites.

42. The method of claim 37, further comprising individually controlling, by the processor, an emission wavelength of the light elements by adjusting a current to each of the light elements.

43. The method of claim 37, further comprising individually controlling, by the processor, the light elements to control one or more of an emission activation or a wavelength of each of the photo-sites.

44. The method of claim 43, further comprising generating, by the processor, one or more of spatial patterns or temporal patterns by controlling the emission activation of the photo-sites, wherein the one or more of the spatial patterns or temporal patterns are projected onto the sample.

45. The method of claim 37, wherein each of the one or more light elements has a light emitting area of less than 200 pm in a first direction.

46. The method of claim 45, wherein each of the one or more light elements has a light emitting area of less than 100 pm in a first direction.

47. The method of claim 45, wherein each of the one or more light elements has a light emitting area of less than 50 pm in a first direction.

48. The method of claim 45, wherein each of the one or more light elements has a light emitting area of less than 20 pm in a first direction.

49. The method of claim 45, wherein each of the one or more light elements has a light emitting area of less than 10 pm in a first direction.

50. The method of claim 37, wherein each of the one or more light elements emits light of central wavelengths of 300 nm to 1000 nm.MGH 2025-169-02Quarles 125141.0495451. The method of claim 37, wherein each of the one or more light elements emits light of central wavelengths of 400 nm to 800 nm.

52. The method of claim 37, wherein each of the one or more light elements includes a light emitting diode (LED) or a laser.

53. The method of claim 37, wherein the method includes optical coherence tomography (OCT).

54. The method of claim 53, wherein the OCT includes spectral domain-OCT (SD-OCT).

55. The method of claim 54, wherein the detecting includes detecting by a spectrometer.

56. The method of claim 53, wherein the OCT includes swept source-OCT (SS-OCT).

57. The method of claim 53, wherein the OCT includes time domain-OCT (TD-OCT).

58. The method of claim 37, further comprising propagating the light through a plurality of waveguides coupled to the photo-sites.

59. The method of claim 37, further comprising propagating the light through a plurality of optical members coupled to the photo-sites.

60. The method of claim 59, wherein the plurality of optical members includes a micro-lens array configured to reshape the light.

61. The method of claim 37, wherein the light source is flexible and configured to conform to a non-planar surface of the sample.

62. The method of claim 37, wherein the detector is a 2D detector.

63. The method of claim 62, wherein the 2D detector includes a rolling shutter that is controllable by the processor.

64. The method of claim 63, further comprising synchronizing, by the processor, control of the photo-sites with the rolling shutter.

65. The method of claim 37, wherein an activation of the light elements includes temporal modulation by the processor.MGH 2025-169-02Quarles 125141.0495466. The method of claim 65, wherein the temporal modulation includes one or more of pulsewidth modulation, amplitude modulation, and on / off modulation.

67. The method of claim 37, further comprising emitting the light from the array onto a spatial light modulator (SLM) to apply spatially varying phase modulation to the light before reaching the sample.

68. The method of claim 67, further comprising applying, by the SLM, varying polarization retardance to encode light originating from each of the photo-sites.

69. The method of claim 37, wherein the array of photo-sites is one-dimensional (ID) or two-dimensional (2D).

70. The method of claim 37, further comprising controlling, by the processor, the photo-sites to emit one or more wavelengths configured to allow spectral unmixing of oxygenated hemoglobin and deoxygenated hemoglobin to determine one or more of relative concentrations or total concentrations of oxygenated hemoglobin, deoxygenated hemoglobin, or a combination thereof.

71. The method of claim 70, further comprising producing, by the processor, one or more maps of oxygen saturation.

72. The method of claim 70, wherein the light source includes two or more sets of photo-sites configured to emit light at two or more central emission wavelengths.

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