Systems, methods, and media for multiple beam optical coherence tomography

Abstract

To provide systems, methods, and media for multiple beam optical coherence tomography.SOLUTION: Systems, methods, and media include: a light source 102; a splitter 108 that outputs part of light to each of a plurality of waveguide bodies; optical components that receive the light from the waveguide bodies and transmit the light as beams, simultaneously apply the beams to a sample 116 at a plurality of lateral positions, and collect backscattered light from the plurality of lateral positions; another splitter 122 that outputs part of light to waveguide bodies of a reference arm as reference light samples; a mixer 130 that receives backscattered light samples and the reference light samples, combines each backscattered sample with a corresponding reference sample to output interference fringes; and a detector 134 that receives the interference fringes, and outputs OCT signals each indicating a structure of the sample at a respective lateral position.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of and priority to U.S. Provisional Application No. 62 / 951,710, filed December 20, 2019, the entire contents of which are incorporated herein by reference.

[0002] <Statement Regarding Federally Sponsored Research> This invention was made with Government support under Grant No. P41EB015903 awarded by the National Institutes of Health. The Government has certain rights in this invention. [Background technology]

[0003] In general, the imaging speed of an optical coherence tomography (OCT) system directly correlates with the performance of the OCT system. Increasing the imaging speed can expand the area that the OCT system can explore, allow OCT coverage of sample motion, and enable oversampling techniques that enable angiographic imaging contrast. One intuitive approach to increasing OCT imaging speed is to increase the sweep rate of the light source in swept-wavelength OCT systems. However, efforts to increase the sampling rate beyond 1 megahertz (MHz) have proven difficult. There are.

[0004] Another approach to increasing the effective sampling rate of the system is to increase the number of beams and / or use an expanded beam to simultaneously image multiple lateral locations with a beam and / or set of beams that extend laterally along the sample. In such an approach, multiple lateral locations are detected simultaneously using parallel imaging channels, thereby obtaining information from multiple beams and / or expanded beams to effectively increase the imaging speed.

[0005] Previous efforts to increase the number of beams have used a separate interferometer for each imaging channel, which limits the scalability of the approach to only a few channels and increases the system complexity. Other efforts have attempted to use multi-beam interferometers using integrated photonic devices, but precise control of the optical delays per channel requires extensive manual labor and / or microfabrication of the devices to depth-encode the channel information.

[0006] Therefore, new systems, methods and media for multi-beam optical coherence tomography are desired. Summary of the Invention

[0007] In some embodiments of the presently disclosed subject matter, systems, methods, and media are provided for multi-beam optical coherence tomography.

[0008] In some embodiments of the presently disclosed subject matter, a system for multi-beam optical coherence tomography is provided, the system comprising: The optical fiber includes a sample arm configured to be optically coupled to a light source, and a reference arm configured to be optically coupled to the light source, the sample arm including a first optical fiber having a proximal end optically coupled to the light source and a distal end, and a reference arm configured to optically couple to the first optical fiber. a first splitter optically coupled to a distal end of a first plurality of optical fibers and optically coupled to a proximal end of each of the first plurality of optical fibers having n optical fibers; and a first plurality of optical components configured to receive a plurality of respective beams from each of the plurality of optical fibers, emit the plurality of beams toward a sample, receive a plurality of spatially separated backscattered light samples from the sample, each backscattered light sample corresponding to one of the first plurality of beams, and transmit the plurality of backscattered light samples toward a detector; and the reference arm includes a second optical fiber having a proximal end optically coupled to the light source and a distal end, and a second optical fiber having a distal end optically coupled to the second optical fiber. and a second splitter optically coupled to a distal end of the optical fiber of the first plurality of optical fibers and to a proximal end of each optical fiber of a second plurality of optical fibers having n optical fibers; and a second plurality of optical components configured to combine each of the plurality of backscattered light samples with a beam emitted by a corresponding optical fiber of the second plurality of optical fibers to generate a plurality of interference fringes and transmit each of the plurality of interference fringes to a corresponding channel of the detector having a plurality of detection channels, the detector configured to output optical coherence tomography data indicative of a structure of the sample at a plurality of locations where the plurality of backscattered light samples were generated.

[0009] In some embodiments, the light source is a wavelength swept laser.

[0010] In some embodiments, the wavelength-swept laser operates at an A-scan rate of 125 kHz.

[0011] In some embodiments, the light source is a wavelength-stepped frequency comb source.

[0012] In some embodiments, the sample arm further comprises a first spatial separator mechanically coupled to a distal end of each optical fiber of the first plurality of optical fibers.

[0013] In some embodiments, the first spatial separator comprises a V-groove assembly.

[0014] In some embodiments, the reference arm further comprises a second spatial separator mechanically coupled to a distal end of each optical fiber of the second plurality of optical fibers.

[0015] In some embodiments, the particular spectral range is centered at 1300 nm.

[0016] In some embodiments, the first splitter comprises a planar lightwave circuit splitter that receives light from the first optical fiber and splits the received light into n outputs.

[0017] In some embodiments, the first spatial separator comprises a V-groove assembly.

[0018] In some embodiments, the first plurality of optical components include a first lens having a first surface optically coupled to the first plurality of optical fibers and a second surface configured to focus the plurality of beams at a first focal length corresponding to a focal length of the first lens, a surface that deflects light received from the second surface of the first lens toward a first surface of a second lens and deflects light received from the first surface of the second lens toward the second surface of the first lens, and a second lens whose first surface is optically coupled to the surface, the second lens having a second surface that directs light received from the surface toward the sample and receives the plurality of backscattered light samples from the sample.

[0019] In some embodiments, the first plurality of optical components comprises a third lens having a first surface optically coupled to the first plurality of optical fibers and a second surface, the third lens comprising: a third lens configured to focus the plurality of beams at a first focal length corresponding to a focal length of a first lens; and a polarizing beam splitter having a first interface that transmits light having a first polarization and polarizes light having a second polarization, the polarizing beam splitter having a first port, a second port, and a third port, the polarizing beam splitter transmitting light having the first polarization received at the first port to the second port and polarizing light having the second polarization received at the second port toward the third port, the first port optically coupled to a second surface of the third lens to receive the plurality of beams from the third lens, the second port optically coupled to a third surface of the fourth lens to emit the plurality of beams toward a fourth lens and receive a plurality of backscattered light samples from the fourth lens. a fourth lens having a first surface optically coupled to the second port, the third port configured to emit the plurality of samples towards a fifth lens, the first surface of the fourth lens optically coupled to the second port and the fourth lens having a second surface, the beam splitter further comprising a quarter wave plate optically coupled to the second surface of the fourth lens and the first surface of the first lens, the first surface of the first lens optically coupled to the quarter wave plate, the fifth lens having a first surface optically coupled to the third port of the polarizing beam splitter and a second surface optically coupled to a third plurality of optical fibers, the first plurality of optical fibers and the third plurality of optical fibers being oriented such that light emitted from each of the first plurality of optical fibers is sent to a corresponding one of the third plurality of optical fibers.

[0020] In some embodiments, the first plurality of optical components comprises a plurality of optical circulators, each having a first port, a second port, and a third port, wherein each first port of each of the plurality of optical circulators is optically coupled to the light source via a corresponding optical fiber of the first plurality of optical fibers, each second port of each of the plurality of optical circulators is optically coupled to the sample via a corresponding optical fiber of a third plurality of optical fibers, and each third port of each of the plurality of optical circulators is optically coupled to the second plurality of optical components via a corresponding optical fiber of a fourth plurality of optical fibers.

[0021] In some embodiments, the system further comprises a spatial separator mechanically coupled to a distal end of each optical fiber of the third plurality and arranged to optically couple each optical fiber of the third plurality to a first surface of the first lens.

[0022] In some embodiments, the first plurality of optical components comprises a second planar lightwave circuit including a plurality of optical couplers each having a first port, a second port, and a third port, wherein each first port of each of the plurality of optical couplers is optically coupled to the light source via a corresponding optical fiber of the first plurality of optical fibers, each second port of each of the plurality of optical couplers is optically coupled to the sample via a corresponding optical fiber of a third plurality of optical fibers, and each third port of each of the plurality of optical couplers is optically coupled to the second plurality of optical components via a corresponding optical fiber of a fourth plurality of optical fibers.

[0023] In some embodiments, each of the plurality of optical couplers outputs a first percentage of the light received at the first port from the third port, outputs a second percentage of the light received at the first port from a fourth port, outputs the first percentage of the light received at the third port from the first port, and outputs the second percentage of the light received at the third port from the second port.

[0024] In some embodiments, the ratio of the first rate to the second rate is about one.

[0025] In some embodiments, the ratio of the first rate to the second rate is less than one.

[0026] In some embodiments, the optical fiber further comprises a spatial separator mechanically coupled to a distal end of each of the third plurality of optical fibers and arranged to optically couple each of the third plurality of optical fibers to a first surface of the first lens.

[0027] In some embodiments, the second plurality of optical components comprises a beam splitter having a first port, a second port, and a third port, the first port configured to receive light emitted by the second plurality of optics, the second port configured to receive the plurality of backscattered light samples, and the third port configured to output the plurality of interference fringes.

[0028] In some embodiments, the detector comprises a plurality of balanced detectors having a first port and a second port, each balanced detector corresponding to a respective channel of the detector, and the beam splitter further comprises a fourth port configured to output a second plurality of interference fringes, and each of the plurality of balanced detectors receives one of the plurality of interference fringes and a corresponding interference fringe of the second plurality of interference fringes and outputs a signal based on both interference fringes.

[0029] In some embodiments, the second plurality of optical components comprises a plurality of optical couplers each having a first port, a second port, a third port, and a fourth port, the first port being coupled to the light source via a respective one of the second plurality of optical fibers, the second port being coupled to the sample via a respective one of a fourth plurality of optical fibers, the third port being coupled to a respective one of the plurality of detection channels, and the fourth port being coupled to a respective one of the plurality of detection channels.

[0030] In some embodiments, each of the plurality of optical couplers is a discrete fiber coupler.

[0031] In some embodiments, the system further comprises a third planar lightwave circuit, the planar lightwave circuit comprising the plurality of optical couplers.

[0032] In some embodiments, the reference arm further comprises a modulation component disposed between the light source and the second splitter, the modulation component configured to at least modulate the polarization of the light input to the second splitter.

[0033] In some embodiments, the reference arm further comprises a modulation component disposed between the light source and the second splitter, the modulation component configured to modulate at least a phase of the light input to the second splitter.

[0034] In some embodiments, the reference arm further comprises a modulation component disposed between the light source and the second splitter, the modulation component configured to modulate the phase of the light input to the second splitter and to modulate the polarization of the light input to the second splitter.

[0035] In some embodiments, the sample arm further comprises a modulation component disposed between the light source and the first splitter, the modulation component configured to at least modulate the polarization of the light input to the first splitter.

[0036] In some embodiments, the sample arm further comprises a modulation component disposed between the light source and the first splitter, the modulation component configured to modulate at least a phase of the light input to the first splitter.

[0037] In some embodiments, the sample arm further comprises a modulation component disposed between the light source and the first splitter, the modulation component configured to modulate a phase of the light input to the first splitter and to modulate a polarization of the light input to the first splitter.

[0038] In some embodiments, the modulation component comprises a coupler having a first port, a second port, and a third port optically coupled to the light source; a first phase modulator having a first port and a second port optically coupled to the second port of the coupler; a second phase modulator having a first port and a second port optically coupled to the third port of the coupler; and a beam combiner having a first port optically coupled to the first phase modulator, a second port optically coupled to the second phase modulator, and a third port.

[0039] In some embodiments, the modulation component further comprises a polarization control part optically coupled to a second port of the coupler and to a first port of the first phase modulator.

[0040] In some embodiments, the modulation component further comprises a polarization control part optically coupled to a third port of the coupler and to a port of the second phase modulator.

[0041] In some embodiments, a system for multi-beam optical coherence tomography includes a first splitter arranged to receive a first light from a light source and output a portion of the first light into each of a first plurality of waveguides; optical components arranged to receive light from the first plurality of waveguides and direct the received light as a plurality of beams to the sample such that each beam strikes a different lateral location on the sample, and collect a plurality of backscattered light samples from the different lateral locations of the sample; a second splitter arranged to receive a second light from the light source and output a portion of the second light into each of a second plurality of waveguides as a plurality of reference light samples; a mixer arranged to receive the plurality of backscattered light samples and the plurality of reference light samples and combine each backscattered light sample with a corresponding reference light sample to output a plurality of interference fringes; and a detector arranged to receive the plurality of interference fringes and output a plurality of optical coherence tomography signals each indicative of a structure at each lateral location of the sample.

[0042] In some embodiments, the plurality of beams comprises eight beams.

[0043] In some embodiments, the first splitter comprises a planar lightwave circuit splitter.

[0044] In some embodiments, the optical component comprises a plurality of optical circulators, each optical circulator being arranged to receive one of the plurality of beams from one of the first plurality of waveguides, direct the received beam towards the sample, and direct a sample of backscattered light towards the detector.

[0045] In some embodiments, the optical component comprises a plurality of optical couplers, each optical coupler being arranged to receive one of the plurality of beams from one of the first plurality of waveguides, direct the received beam towards the sample, and direct a sample of backscattered light towards the detector.

[0046] In some embodiments, the system further comprises the light source.

[0047] Various objects, features and advantages of the presently disclosed subject matter can be more fully understood by considering the following detailed description of the presently disclosed subject matter in conjunction with the following drawings, in which like reference numerals refer to like elements, and in which: [Brief description of the drawings]

[0048] [Figure 1] FIG. 1 illustrates an example of a system for multi-beam optical coherence tomography according to some embodiments of the presently disclosed subject matter. [Diagram 2] FIG. 2 illustrates an example of a splitter that can be used to implement part of a system for multi-beam optical coherence tomography according to some embodiments of the presently disclosed subject matter. [Diagram 3] FIG. 2 illustrates an example of a sampling optical system that can be used to realize part of the system for multi-beam optical coherence tomography of some embodiments of the subject matter disclosed herein and that can be used to realize part of the system shown in FIG. [Figure 4] FIG. 2 illustrates an example of an optical system that can be used to realize the mixing portion of a multi-beam interferometer for multi-beam optical coherence tomography of some embodiments of the presently disclosed subject matter. [Diagram 5] FIG. 2 illustrates an example of components that can be used to implement a portion of a detector for multi-beam optical coherence tomography according to some embodiments of the presently disclosed subject matter. [Figure 6A]1 illustrates an example of an arrangement of components that can be used to align multiple optical fibers across a free space gap in some embodiments of the presently disclosed subject matter. [Figure 6B] FIG. 6B is a side view of the arrangement of parts of some embodiments of the presently disclosed subject matter shown in FIG. 6A. [Figure 7A] FIG. 1 illustrates an example of a composite structural C-scan of a human finger generated by combining information from multiple optical coherence tomography signals acquired simultaneously using a system for multi-beam optical coherence tomography implemented in some embodiments of the presently disclosed subject matter. [Figure 7B] FIG. 2 illustrates an example of multiple B-scans generated simultaneously using multiple channels of a system for multi-beam optical coherence tomography implemented in some embodiments of the presently disclosed subject matter. [Figure 8] FIG. 1 shows an example of multiple en face optical coherence tomography angiography images inside a mouse ear generated simultaneously using multiple channels of a system for multi-beam optical coherence tomography implemented in some embodiments of the presently disclosed subject matter, and a composite en face image generated from information generated using multiple channels of some embodiments of the presently disclosed subject matter. [Figure 9] FIG. 2 illustrates an example process for simultaneously generating multiple optical coherence tomography images using multiple beams according to some embodiments of the presently disclosed subject matter. [Figure 10] FIG. 1 illustrates example hardware that can be used to implement an imaging device and / or a computer that can be used with some embodiments of the mechanism for multi-beam optical coherence tomography implemented in some embodiments of the subject matter disclosed herein. [Figure 11] FIG. 1 illustrates an example of a system for multi-beam optical coherence tomography implemented in some embodiments of the presently disclosed subject matter. [Figure 12]FIG. 2 illustrates an example of components that can be used to implement a portion of a phase and / or polarization modulator of some embodiments of the presently disclosed subject matter. [Figure 13] FIG. 2 illustrates an example of a part of the sampling optics of a system for multi-beam optical coherence tomography according to some embodiments of the subject matter disclosed herein, which can be used to realize a part of the sampling optics of the system shown in FIG. [Figure 14] FIG. 2 illustrates another example of a part of the sampling optics of a system for multi-beam optical coherence tomography according to some embodiments of the subject matter disclosed herein that can be used to realize a part of the sampling optics of the system shown in FIG. [Figure 15] FIG. 2 illustrates another example of a component that can be used to realize the focusing portion of the sampling optical system of the system for multi-beam optical coherence tomography of some embodiments of the subject matter disclosed herein, the focusing portion of the sampling optical system of the system shown in FIG. [Figure 16] FIG. 2 illustrates an example of optical components that can be used to implement the mixing portion of a multi-beam interferometer for multi-beam optical coherence tomography of some embodiments of the presently disclosed subject matter. [Figure 17] FIG. 13 illustrates another example of optical components that can be used to implement the mixing portion of a multi-beam interferometer for multi-beam optical coherence tomography according to some embodiments of the presently disclosed subject matter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] In some embodiments of the presently disclosed subject matter, mechanisms (which may include systems, methods, and mediums) are provided for multi-beam optical coherence tomography.

[0050] In some embodiments, the mechanism described herein may use a light source that defines a single channel imaging rate, a single waveguide-based reference arm, and a single waveguide-based sample arm, each of which includes a first optical subsystem that can be used to generate a set of electromagnetic waves. In some embodiments, the sample arm may include a second optical subsystem that can be used to probe a set of sample locations with the electromagnetic waves provided by the first optical subsystem of the sample arm, the second optical subsystem being capable of collecting corresponding backscattered electromagnetic waves from the sample. In some embodiments, a third optical subsystem may receive a reference electromagnetic wave from the reference arm and combine the reference electromagnetic wave with the corresponding backscattered electromagnetic waves to generate a set of interference fringes. In some embodiments, the detection and processing arrangement may record the interference fringes of each imaging channel separately, and the recorded information from the interference fringes may be used to generate multiple OCT signals, each of which represents a different portion of the sample.

[0051] FIG. 1 illustrates an example system 100 for multi-beam optical coherence tomography according to some embodiments of the presently disclosed subject matter. In some embodiments, the system 100 can include a light source 102 suitable for generating an OCT signal. For example, the light source 102 can be a wavelength-swept laser. In such an example, the wavelength-swept laser can be operated at any suitable A-scan rate (e.g., the number of times it sweeps through a range of wavelengths per time period) and can be centered at any suitable frequency. In one more specific example, the A-scan rate is about 125 kilohertz (kHz) and the center wavelength is about 1300 nanometers. As another example, the light source 102 can be a frequency comb source, such as a wavelength-stepped frequency comb source. In such an example, the wavelength-stepped frequency comb laser can be operated at any suitable A-scan rate (e.g., the number of times it steps through the entire wavelength range per period) and can be centered at any suitable frequency. For example, the A-scan rate can be about 125 kHz, 250 kHz, 500 kHz, 1 MHz, 2 MHz, 4 MHz, or any other suitable scan rate, and the center wavelength can be about 1300 nanometers (nm), 1050 nm, 1580 nm, or any other suitable wavelength. In other examples, the light source 102 can be configured using a Fourier domain mode-locked laser, a vertical cavity surface emitting laser, a stretch pulse mode-locked laser, or a phase code mode-locked laser.

[0052] In some embodiments, the light source 102 may be coupled to the sample and reference arms of the system 100 using any suitable optical component or components. For example, a fiber The coupler 104 can receive light from the light source 102 (e.g., via an electromagnetic wave conductor, such as an optical fiber, optically coupled between an output of the light source 102 and an input port of the fiber coupler 104) and output a first portion of the light toward a sample arm and a second portion of the light toward a reference arm. In some embodiments, any suitable portion of the source light can be sent to the sample arm. For example, more than half of the source light received at the fiber coupler 104 can be sent to the sample arm and less than half can be sent to the reference arm. As a more specific example, about 80% of the source light received at the fiber coupler 104 can be sent to the sample arm and 20% can be sent to the reference arm.

[0053] In some embodiments, the sampling arm may comprise an electromagnetic wave conductor, such as a single mode optical fiber 106, optically coupled to an output of the fiber coupler 104 and an input of an N-way optical splitter 108. In some embodiments, the N-way splitter 108 may be configured using any suitable optical component or combination of components. For example, the N-way splitter 108 may be configured as an N-way planar lightwave circuit. As another example, the N-way splitter 108 may be configured as a monolithic fused optical fiber splitter. As yet another example, the N-way splitter 108 may be configured as a monolithic fused optical fiber splitter. Splitter 108 may be implemented as a fiber optic fused splitter constructed by cascading optical splitters.

[0054] In some embodiments, the outputs of N-way splitter 108 may be coupled to N electromagnetic wave guides, such as fiber bundle 110. In some embodiments, fiber bundle 110 may be constructed using any suitable component or any suitable combination of components. For example, fiber bundle 110 may be constructed using an optical fiber ribbon having at least N optical fibers. In some embodiments, each optical fiber of fiber bundle 110 may be a single mode optical fiber.

[0055] In some embodiments, an output side of each of the N optical fibers 110 may be coupled to sampling optics 112. In some embodiments, the sampling optics may receive light from each optical fiber of the fiber bundle 110, convert the light from each fiber into a beam of light, and focus the resulting N beams 114 at or near the surface of the sample 116. The sample 116 may backscatter a portion of each beam back to the sampling optics 112. The sampling optics 112 may receive the backscattered light from the sample 116 and direct the backscattered light from each of the N beams 114 into N electromagnetic wave guides, such as respective fibers of the fiber bundle 118. In some embodiments, the fiber bundle 118 may be constructed using components similar to those used to construct the fiber bundle 110. In some embodiments, each optical fiber of the fiber bundle 118 may be a single mode optical fiber.

[0056] In some embodiments, the reference arm may comprise an electromagnetic wave conductor, such as a single mode optical fiber 120, that is optically coupled to an output of the fiber coupler 104 and an input of an N-way optical splitter 122. In some embodiments, the N-way splitter 122 may be constructed using any suitable optical component or any suitable combination of components. For example, the N-way splitter 122 may be constructed using components similar to those used to construct the N-way splitter 108.

[0057] In some embodiments, the outputs of N-way splitter 122 may be coupled to N electromagnetic wave conductors, such as individual fibers of fiber bundle 124. In some embodiments, fiber bundle 124 may be constructed using any suitable component or any suitable combination of components. For example, fiber bundle 124 may be constructed using components similar to those used to construct fiber bundle 110. In some embodiments, the fibers Each optical fiber in the fiber bundle 124 may be a single mode optical fiber.

[0058] In some embodiments, the distal end of fiber bundle 118 may be optically coupled to a first set of inputs of mixer 130, and the distal end of fiber bundle 124 may be optically coupled to a second set of inputs of mixer 130. In some embodiments, mixer 130 may convert light from each of the individual fibers of fiber bundle 118 and fiber bundle 124 into beams and each beam from fiber bundle 118 may be respectively combined with a corresponding beam from fiber bundle 124.

[0059] In some embodiments, when the signals are combined, the difference between the path length of the beam from the sample arm (e.g., the path length of the backscattered light from the sample) and the path length of the beam from the reference arm can produce an interference pattern related to the structure of the sample 116. In some embodiments, the optical path lengths of the reference arm and the sample arm can be approximately equal. Additionally, in some embodiments, the path length of the reference arm and / or the sample arm can be variable, allowing the target distance of the OCT system 100 to be adjustable.

[0060] In some embodiments, the output of mixer 130 may be coupled to N electromagnetic wave guides, such as fiber bundles 132. In some embodiments, fiber bundle 132 may be constructed using any suitable component or combination of components. For example, fiber bundle 132 may be constructed using a fiber optic ribbon having at least N optical fibers. Additionally, in some embodiments, mixer 130 may be coupled to 2N electromagnetic wave guides (e.g., two fiber bundles 132), with each pair of the 2N electromagnetic wave guides carrying an associated signal.

[0061] In some embodiments, detectors 134 may be coupled to one or more outputs of the mixer 130 and may generate OCT signals for each of the N beams incident on the sample 116. In some embodiments, the detectors 134 may be implemented using any suitable technique or combination of techniques. For example, as described below with reference to FIG. 5, the detectors 134 may be configured using balanced detectors, each of which receives a pair of interference fringe signals from the mixer 130 and provides an output to a corresponding channel of a data acquisition board. In some embodiments, signals from the detectors 134 may be used to generate an OCT image depicting the structure of the sample 116.

[0062] In some embodiments, the reference arm can include a component 142 (sometimes referred to herein as a phase control, a polarization control, and / or a modulation component) that can be configured to cause a common optical function that affects the beams propagating through the reference arm (e.g., all N beams propagating through the fiber bundle 124). For example, in some embodiments, the modulation component 142 can be configured to modulate the phase of the electromagnetic wave in the reference arm, modulate the polarization of the electromagnetic wave in the reference arm, modulate the phase and polarization of the electromagnetic wave in the reference arm, modulate or shift the optical frequency of the electromagnetic wave in the reference arm, and / or any other suitable function. In a more specific example, the modulation component 142 can be an optical phase modulator. In another specific example, the modulation component 142 can be an optical polarization modulator. In another more specific example, the modulation component 142 can be an optical phase polarization modulator.

[0063] In some embodiments, modulating the phase of the electromagnetic wave (e.g., by modulation component 142) can generate a complex fringe signal (e.g., a signal that includes components that can be detected using heterodyne detection techniques). For example, modulating the phase of the electromagnetic wave in the reference arm can generate a complex fringe signal when the phase-modulated electromagnetic wave in the reference arm interacts with the electromagnetic wave in the sample arm (e.g., at mixer 130). The information contained in the complex fringe signal can be used to perform OCT and sub-sampled OCT (circular In this paper, we can distinguish between positive and negative optical retardation space in circular-ranging OCT (sometimes called circular-ranging OCT).

[0064] In some embodiments, the modulation component 142 can be configured as a phase modulator using any suitable technology or any suitable combination of technologies. For example, the modulation component 142 can be and / or include an electro-optic modulator. In one more specific example, the modulation component 142 can be a lithium niobate modulator. As another example, the modulation component 142 can be and / or include an acousto-optic modulator. In one more specific example, the modulation component 142 can be an optical frequency shifter.

[0065] In some embodiments, the polarization of the electromagnetic wave can be modulated (e.g., by modulation component 142) to facilitate interferometric measurements of multiple polarizations. For example, the interference between electromagnetic waves propagated through the reference arm and the sample arm can be measured separately in two or more different polarization states. Interferometric measurements of multiple polarizations can increase the signal-to-noise ratio of the detected signal.

[0066] In some embodiments, the modulation component 142 can be configured as a polarization modulator using any suitable technology or any suitable combination of technologies. For example, the modulation component 142 can be an electro-optic or acousto-optic modulator that induces different phase modulation in transverse electric (TE) and transverse magnetic (TM) optical modes to modulate the polarization. As a more specific example, a lithium niobate modulator can be used to provide an electro-optic modulator with different phase responses in the TE and TM optical modes.

[0067] In some embodiments, the sample arm may include components 144 (sometimes referred to herein as phase controls, polarization controls, and / or modulation components) that are configurable to cause a common optical function that affects the beams propagating through the sample arm (e.g., all N beams propagating through fiber bundle 110). In some embodiments, modulation components 144 may be configured to modulate the phase, polarization, and / or optical frequency of the electromagnetic waves in the sample arm using any suitable technique, such as those techniques described above for modulation component 142.

[0068] In some embodiments, modulation component 142 and / or modulation component 144 can be omitted. Additionally or alternatively, in some embodiments, modulation component 142 can include a phase modulator and modulation component 144 can omit a phase modulator (or vice versa). In some embodiments, modulation component 142 and modulation component 144 can include a polarization modulator.

[0069] In some embodiments, the modulation component 142 and / or the modulation component 144 can be configured to induce phase and / or polarization modulation that induces modulation between consecutive A-lines, or can induce modulation within an A-line. Furthermore, if the light source 102 is implemented as a wavelength-stepped frequency comb source, the modulation component 142 and / or the modulation component 144 can also induce modulation between consecutive A-lines, between optical pulses of a wavelength-stepped frequency comb source, etc.

[0070] In some embodiments, the reference arm may include a variable optical delay element (not shown) to control the optical delay of the electromagnetic waves in each reference arm fiber (e.g., each fiber of fiber bundle 124, etc.). For example, an optical delay component may be placed before splitter 122 (e.g., connected to fiber 120) so that the optical delay affects all beams in the reference arm. The variable optical delay can be achieved using any suitable technique or combination of techniques. For example, the variable optical delay can be achieved using a mirror on a translation stage with an optical circulator disposed between the portions of the fibers 120 (e.g., light from the fiber coupler 104 and / or the modulation component 142 can be directed to the mirror by the optical circulator, and light reflected by the mirror can be directed by the optical circulator towards the splitter 122). As another example, a free space coupling arrangement can be disposed between the portions of the fibers 120, and the distance between the portions of the fibers 120 can be varied (e.g., using a translation stage, etc.). Additionally or alternatively, a variable optical delay element can be disposed in the sample arm (e.g., in connection with the fibers 106).

[0071] 2 is a diagram illustrating an example splitter 200 that may be used to implement portions of the system 100 for multi-beam optical coherence tomography of some embodiments of the presently disclosed subject matter. In some embodiments, the splitter 200 may have an input coupled to and / or implemented by an electromagnetic wave guide. For example, an optical fiber 202 may serve as and / or be coupled to the input of the splitter 200.

[0072] In some embodiments, a proximal end of the optical fiber 202 can be coupled to a light source (such as light source 102) and a distal end of the optical fiber 202 can be coupled to splitting optics 204. For example, the optical fiber 202 can be used to implement at least a portion of optical fiber 106 or optical fiber 120.

[0073] In some embodiments, the splitting optics 204 may be implemented using any suitable technology or any suitable combination of technologies. For example, the splitting optics 204 may be implemented using planar lightwave circuits. As another example, the splitting optics 204 may be implemented as a fused optical fiber splitter, as described above for the N-way splitter 108. In some embodiments, the splitting optics 204 may split the light received via the optical fiber 202 into any suitable number of portions. For example, in some embodiments, the splitting optics 204 may be a 1×8 planar lightwave circuit that splits the light into eight substantially equal portions. As another example, the splitting optics 204 may be implemented by cascading and / or otherwise combining multiple relatively small planar lightwave circuits, such as 1×2 planar lightwave circuits.

[0074] In some embodiments, multiple outputs of splitting optics 204 can be coupled to a group of optical fibers 206, with each optical fiber 206 in the group having a proximal end optically coupled to one channel of splitting optics 204 and a distal end that can be coupled to another optical device. For example, optical fibers 206 can be used to implement at least a portion of fiber bundle 110 or fiber bundle 124.

[0075] FIG. 3 illustrates an example of a sampling optics 300 that can be used to implement a portion of the system 100 for multi-beam optical coherence tomography of some embodiments of the subject matter of the present disclosure. As shown in FIG. 3, the sampling optics 300 can receive multiple portions of light from a light source (e.g., via an N-way splitter 108, etc.). In some embodiments, the sampling optics 300 can include a spatial separator 302 configured to mechanically position the distal ends of multiple optical fibers of a fiber optic bundle (e.g., fiber optic bundle 110, etc.) such that a face of each optical fiber of the fiber optic bundle is held in a specific relative position and a specific relative orientation with respect to other optical elements of the sampling optics 300. For example, the cladding surrounding the core can be placed in a V-shaped groove sized to precisely position the individual optical fibers of the fiber optic bundle 110, including the core and the cladding. By positioning the optical fibers in the optical fiber bundle 110, the spatial separator 302 can position the fibers at specific locations defined in one dimension (e.g., using a linear V-groove, etc.) or can position the fibers at specific locations defined in two dimensions (e.g., an array, etc.). In some embodiments, the spatial separator 302 can be implemented using any suitable component. For example, the spatial separator 302 can be a single mode V-groove array available from OZ Optics, Inc., headquartered in Ottawa, Canada. In another example, the spatial separator 302 may be implemented as a V-groove assembly, such as a 3D array of wells or through-holes drilled into a material (e.g., glass, silicon dioxide, etc.) in which individual fibers of the set of fibers are fixed such that the faces of each fiber are precisely aligned with each other. In such an example, the wells or through-holes may be formed mechanically (e.g., using a mechanical drilling tool, etc.) and / or using other processing techniques (e.g., photolithography, etc.). In such an example, the wells or through-holes of the array may be arranged in any suitable one- or two-dimensional layout (e.g., in a row or column, in a set of rows or columns, as multiple concentric circles, etc.). In yet another example, the spatial separator 302 may be implemented as one or more multi-core fibers, each optical core of which is arranged in a specific relative position to one another in the multi-core fiber.

[0076] In some embodiments, a first lens 304 can be optically coupled to the optical fibers of the fiber bundle 110. As shown in FIG. 3, the first lens 304 can be positioned such that the facet of each optical fiber of the fiber bundle 110 coincides with the focal length f1 of the first lens 304 and emits a beam from a point at a particular radial distance from the optical axis of the first lens 304. As shown in FIG. 3, the first lens 304 can be a biconvex lens. However, this is by way of example only, and many types of lenses can be used to realize the first lens 304 (and other lenses shown in the figures as biconvex lenses). For example, without excluding any type of suitable lens, other types of lenses (e.g., the lenses shown in FIGS. 3, 4, 6A, 6B, and 11) that can be used to realize the mechanisms for multi-beam optical coherence tomography described herein include plano-convex lenses, achromatic doublet lenses, Fresnel lenses, and graded index (GRIN) lenses. In some embodiments, when the spatial separator 302 is used to align the optical fibers of the fiber bundle 110 such that all beams emitted by the optical fibers of the fiber bundle 110 are coplanar, the positioning of the spatial separator 302 with respect to the first lens 304 can be such that the optical axis of the first lens 304 is coplanar with the beams. For example, the above configuration can facilitate alignment of one or more other components with respect to the spatial separator 302 and the first lens 304.

[0077] In some embodiments, each optical fiber of the fiber bundle 110 can emit an individual beam towards a first face of the first lens 304, which can focus light received from the fiber bundle 110 at a focal length f1 distal to the first lens 304. This allows the beams from each of the optical fibers to converge at a focal point of the first lens 304. In the absence of other optical components, the beams will diverge after the focal point, and at a distance of 2*f1 from the face of the optical fiber, the beams will be mirrored across the optical axis and collected by an array of optical fibers having mirror image positions relative to the optical fibers positioned by the spatial separator 302.

[0078] In some embodiments, the sampling optics 300 can include a polarizing beam splitter 306 disposed at the focal point of the first lens 304 and / or the second lens 308. In some embodiments, the polarizing beam splitter 306 can receive light from the first lens 304, emit substantially all of the light having a first linear polarization toward the second lens 308, and deflect all of the light having a second, orthogonal polarization toward a second optical axis. In the example, the sample arm can include a polarization control (not shown) that causes the light emitted from the fiber bundle 110 to be in a uniform polarization state such that the polarizing beam splitter 306 transmits substantially all of the light emitted from the fiber bundle 110 towards the second lens 308.

[0079] In some embodiments, the beam emitted from the first lens 304 may converge at the interface of the polarizing beam splitter 306 and begin to diverge as it travels towards a first surface of the second lens 308. The second lens 308 may be positioned such that the interface of the polarizing beam splitter 306 coincides with the focal length f2 of the second lens 308. In some embodiments, the focal length of the first lens 304 and the focal length of the second lens 308 may be equal (e.g., f1=f2), although this is merely an example and the focal lengths of both lenses may be different.

[0080] In some embodiments, the second lens 308 can focus the diverging beams so that they become substantially parallel beams traveling parallel to the optical axis of the second lens 308. In some embodiments, as shown in FIG. 3, the second lens 308 can focus each beam to a point with a focal length f2. For example, if the interface of the polarizing beam splitter 306 is located at a distance equal to the focal length f2 from the first surface of the second lens 308, each beam can be focused at a distance equal to the focal length f2 on the second surface side of the second lens 308.

[0081] In some embodiments, the sampling optics 300 can include a quarter wave plate 310 disposed in the focal plane of the second lens 308 and in the focal plane of the third lens 312. In some embodiments, the quarter wave plate 310 can be positioned to shift the polarization of the light received from the second lens 308 to circular polarization. For example, in some embodiments, the quarter wave plate 310 can be positioned such that the fast axis of the quarter wave plate 310 can circularly polarize the output light with an angle of 45° to the input polarization axis. In some embodiments, each beam can be emitted from the quarter wave plate 310 toward a first surface of the third lens 312. The third lens 312 can be positioned such that the center of the quarter wave plate 310 coincides with the focal length f3 of the third lens 312. In some embodiments, the third lens 312 can be positioned such that the center of the quarter wave plate 310 coincides with the focal length f3 of the third lens 312. The second focal length can be equal to or different from the focal lengths of the first lens 304 and / or the second lens 308. In some embodiments, the third lens 312 can focus the beam received from the quarter wave plate 310 to a focal length f3 distal to the third lens 312, such that the beams corresponding to each of the multiple optical fibers of the fiber bundle 110 can be focused at the focal point of the third lens 312.

[0082] In some embodiments, the sampling optics 300 may include a reflector 314 that deflects the light received from the third lens 312 toward the sample 116. The reflector 314 may be positioned such that the reflecting surface of the reflector 314 coincides with the focal length f3 of the third lens 312. In some embodiments, the reflector 314 may be implemented using any suitable reflecting surface, such as a plane mirror, a galvanometer, a micro-electromechanical system (MEMS) type mirror, a polygon mirror scanner, or the like. In some embodiments, the angle of the reflector 314 may be fixed or adjustable. For example, in some embodiments, the reflector 314 may be a galvanometer scanner surface that may be used to control the angle that the reflector 314 makes with the optical axis of the third lens 312.

[0083] In some embodiments, the beam emitted from the third lens 312 may converge at the reflective surface of the reflector 314 and begin to diverge as it travels toward a first surface of the fourth lens 316. The fourth lens 316 may be positioned such that the reflective surface of the reflector 314 coincides with the focal length f4 of the fourth lens 316. The focal length may be equal to or different from the focal lengths of the first lens 304, the second lens 308 and / or the third lens 312.

[0084] In some embodiments, the fourth lens 316 can focus the diverging beams such that they become substantially parallel beams traveling parallel to the optical axis of the fourth lens 316 when they intersect the surface of the sample 116. In some embodiments, as shown in FIG. 3, the fourth lens 316 can focus each beam to a point with a focal length f4. For example, if the reflecting surface of the reflector 314 is disposed at a distance equal to the focal length f4 from the first surface of the fourth lens 316, each beam can converge at a distance equal to the focal length f4 on the second surface of the fourth lens 316 and begin to diverge (e.g., form a beam waist at the focal length f4) after passing the distance equal to the focal length f4.

[0085] In some embodiments, the sample 116 may backscatter one or more portions of each beam incident on the sample. The depth to which the light is backscattered may depend on the structure of the sample 116 and / or the wavelength of the incident light. This may result in different amounts of phase difference between the backscattered light and the light propagating in the reference arm. Additionally, the polarization of the light backscattered by the sample 116 may also be inverted.

[0086] In some embodiments, the light backscattered by the sample 116 can have its polarization adjusted by a quarter-wave plate to a linear polarization offset by 90° relative to the incident light and return to the sampling optics 300 along the same path as the incident light from the light source 102, with most of the backscattered light being deflected by the polarizing beam splitter 306 into a path that coincides with the second optical axis of the polarizing beam splitter 306 (e.g., an optical path substantially perpendicular to the optical axes of the first lens 304 and the second lens 308).

[0087] In some embodiments, the beam of backscattered light emitted from the proximal side of the second lens 308 may converge at an interface of the polarizing beam splitter 306, which may reflect the backscattered light. The beam of backscattered light may then begin to diverge as it travels along the second optical axis of the polarizing beam splitter 306 toward a first surface of the fifth lens 320. The fifth lens 320 may be positioned such that the interface of the polarizing beam splitter 306 coincides with a focal length f5 of the fifth lens 320. In some embodiments, the focal length of the fifth lens 320 may be equal to or different from the focal lengths of the first lens 304, the second lens 308, the third lens 312, and / or the fourth lens 316. For example, in order to maintain a constant beam spacing between the first surface of the first lens 304 and the second surface of the fifth lens 320 (e.g., to enable a constant spacing between the spatial separator 302 and the second spatial separator described below), the focal length of the first lens 304 and the focal length of the fifth lens 320 can be configured to be equal (e.g., f1=f5).

[0088] In some embodiments, the sampling optics 300 can include a second spatial separator 322 configured to mechanically position the proximal ends of the optical fibers of a fiber optic bundle (e.g., fiber optic bundle 118) such that a face of each optical fiber of the fiber optic bundle is held in a specific relative position and a specific relative orientation with respect to other optical elements of the sampling optics 300. For example, each core of each optical fiber of the fiber optic bundle 118 can be positioned by placing the cladding surrounding the core in a V-shaped groove sized to precisely position each optical fiber of the fiber optic bundle 118, including the core and the cladding. In some embodiments, the spatial separator 322 can be implemented using any suitable components, such as those described above for the spatial separator 302. In some embodiments, the second spatial separator 322 is positioned such that the beams of backscattered light emitted from the second surface of the fifth lens 320 are received by the respective optical fibers. As described below, an alignment system can be used to precisely align spatial separator 322 so that a beam of backscattered light is received by a corresponding optical fiber that transmits the backscattered light to a mixer (such as mixer 130).

[0089] 4 illustrates an example optical system 400 that can be used to implement the mixing portion of a multi-beam interferometer for multi-beam optical coherence tomography of some embodiments of the presently disclosed subject matter. As shown in FIG. 4, there are various components that can be used to implement the free-space mixer 400. In some embodiments, the free-space mixer 400 can include a spatial separator 402 configured to mechanically position the distal ends of multiple optical fibers of a fiber optic bundle (e.g., fiber optic bundle 124) such that a face of each optical fiber of the fiber optic bundle is held in a specific relative position and orientation with respect to other optical elements of the free-space mixer 400. In some embodiments, the spatial separator 402 can be implemented using any suitable components, such as those described above for the spatial separator 302 of FIG. 3.

[0090] In some embodiments, a first lens 404 can be optically coupled to the optical fibers of the fiber bundle 124. As shown in FIG. 4, a second lens 412 can be positioned such that the face of each optical fiber of the fiber bundle 118 coincides with the focal length of the second lens 412 and emits the backscattered beam from a point that is a particular radial distance from the optical axis of the second lens 412. In some embodiments, if a spatial separator 402 is used to align the optical fibers of the fiber bundle 124 such that all reference beams emitted by the optical fibers of the fiber bundle 124 are coplanar, the positioning of the spatial separator 402 relative to the first lens 404 can be such that the optical axis of the first lens 404 is coplanar with the reference beams. For example, the above configuration can facilitate alignment of one or more other components relative to the spatial separator 402 and the first lens 404.

[0091] In some embodiments, each optical fiber of the fiber bundle 124 can emit an individual beam towards a first face of the first lens 404, which can focus light received from the fiber bundle 124 at a focal length f distal to the first lens 404. This allows the reference beams from each of the optical fibers to be focused at the focal point of the first lens 404. In the absence of other optical components, the reference beams diverge after the focal point, and at a distance of 2*f from the face of the optical fiber, the reference beams are mirrored across the optical axis and collected by an array of optical fibers having mirror image positions relative to the optical fibers positioned by the spatial separator 402.

[0092] In some embodiments, the free space mixer 400 may include a beam splitter 406 disposed at a focal point of the first lens 404, a focal point of the second lens 412, a focal point of the third lens 420, and a focal point of the fourth lens 430. In some embodiments, the beam splitter 406 may receive light from the first lens 404 and deflect a first portion of the light toward the third lens 420 and transmit a second portion of the light toward the fourth lens 430. For example, approximately half of the light received from the first lens 404 may be deflected toward the third lens 420 and approximately half of the light received from the first lens 404 may be transmitted toward the fourth lens 430.

[0093] In some embodiments, the free-space mixer 400 can include a second spatial separator 410 that mechanically separates the distal ends of multiple optical fibers in a fiber optic bundle (such as the fiber optic bundle 118) such that a face of each optical fiber in the fiber optic bundle is held in a specific relative position and in a specific relative orientation with respect to other optical elements of the free-space mixer 400. In some embodiments, spatial separator 410 may be implemented using any suitable components, such as those described above for spatial separator 302 in FIG.

[0094] In some embodiments, a second lens 412 can be optically coupled to the optical fibers of the fiber bundle 118. As shown in FIG. 4, the second lens 412 can be positioned such that the face of each optical fiber of the fiber bundle 118 coincides with the focal length of the second lens 412, and emits the backscattered beam from a point that is a particular radial distance from the optical axis of the second lens 412. In some embodiments, if a spatial separator 410 is used to align the optical fibers of the fiber bundle 118 such that all backscattered beams emitted by the optical fibers of the fiber bundle 118 are coplanar, the positioning of the spatial separator 410 relative to the second lens 412 can be such that the optical axis of the second lens 412 is coplanar with the backscattered beams. For example, the above configuration can facilitate alignment of one or more other components relative to the spatial separator 410 and the second lens 412.

[0095] In some embodiments, each optical fiber of the fiber bundle 118 can emit an individual backscattered beam towards a first surface of the second lens 412, which can focus light received from the fiber bundle 118 at a focal length f distal to the second lens 410 (distal from the light source 102). This allows the backscattered beams from each of the optical fibers to converge at a focal point of the second lens 412. In the absence of other optical components, the backscattered beams diverge after the focal point, and at a distance of 2*f from the surface of the optical fiber, the backscattered beams are mirrored across the optical axis and collected by an array of optical fibers having mirror image positions relative to the optical fibers positioned by the spatial separator 410.

[0096] In some embodiments, the beam splitter 406 can receive light from the second lens 412, deflect a first portion of the light towards the fourth lens 430, and transmit a second portion of the light towards the third lens 420. For example, approximately half of the light received from the second lens 412 can be deflected towards the fourth lens 430 and approximately half of the light received from the second lens 412 can be transmitted towards the third lens 420.

[0097] In some embodiments, the reference beam emitted from the first lens 404 can converge at the interface of the beam splitter 406, and the backscattered beam emitted from the second lens 412 can converge at the interface of the beam splitter 406 from an orthogonal direction. The beam splitter 406 splits the reference beam emitted from the first lens 404, such that the first reference beam is transmitted by the beam splitter 406 and diverges as it travels towards the first surface of the fourth lens 430, and the second reference beam is reflected by the beam splitter 406 and diverges as it travels towards the first surface of the third lens 420. The beam splitter 406 may split the backscattered beam emitted from the second lens 412, such that a first backscattered beam is transmitted by the beam splitter 406 and diverges as it travels toward a first surface of the third lens 420, and a second backscattered beam is reflected by the beam splitter 406 and diverges as it travels toward a first surface of the fourth lens 430. In some embodiments, the spatial separator 402, the first lens 404, the spatial separator 410, the second lens 412, and the beam splitter 406 may be aligned such that a first reference beam combines with a corresponding first backscattered beam to form a first interference beam that diverges toward the first surface of the third lens 420, and a second reference beam combines with a corresponding second backscattered beam to form a second interference beam that diverges toward the first surface of the fourth lens 430. In some embodiments, the first interfering beam can include interference fringes caused by the interaction of the reference light and the backscattered light contained in the first interfering beam.

[0098] In some embodiments, the third lens 420 and the fourth lens 430 are arranged such that the interface of the beam splitter 406 coincides with the focal length f of the third lens 420 and the fourth lens 430. In some embodiments, the third lens 420 can focus the first interfering beam so that it is a substantially parallel beam traveling parallel to the optical axis of the third lens 420, and the fourth lens 430 can focus the second interfering beam so that it is a substantially parallel beam traveling parallel to the optical axis of the fourth lens 430. In some embodiments, the reference arm can include a polarization controller (not shown) that causes the light emitted from the fiber bundle 124 to have a uniform polarization state such that substantially all of the light emitted from the fiber bundle 124 has the same polarization as the polarization of the backscattered beam. For example, a polarization controller can be inserted on the optical fiber 120. In general, as the light in the reference arm and the sample arm propagates in the optical fibers (e.g., in optical fiber 106, optical fiber 120, each optical fiber in fiber bundle 110, each optical fiber in fiber bundle 118, each optical fiber in fiber bundle 124, etc.), the polarization may change arbitrarily due to the physical properties of the fiber (e.g., due to bending or stress on the fiber, etc.). In addition, the sample arm experiences a 90° polarization change, which causes reflection by the polarizing beam splitter 306. The polarization control in the reference arm can be manipulated to match the polarization of the light in the reference arm to the polarization of the backscattered beam in the sample arm to increase the interaction of the beams in the free-space mixer.

[0099] In some embodiments, the free-space mixer 400 can include a third spatial separator 422 configured to mechanically position the proximal ends of multiple optical fibers in a fiber optic bundle (e.g., fiber optic bundle 132-1, etc.) such that a face of each optical fiber in the fiber optic bundle is held in a specific relative position and in a specific relative orientation with respect to other optical elements of the free-space mixer 400. For example, the core of each individual optical fiber in fiber optic bundle 132-1 can be positioned with the cladding surrounding the core in a v-shaped groove in the third spatial separator 422 sized to precisely position the individual optical fiber, including the core and cladding. Additionally, in some embodiments, the free-space mixer 400 can include a fourth spatial separator 432 configured to mechanically position the proximal ends of multiple optical fibers in a fiber optic bundle (e.g., fiber optic bundle 132-2, etc.) such that a face of each optical fiber in the fiber optic bundle is held in a specific relative position and in a specific relative orientation with respect to other optical elements of the free-space mixer 400. For example, the core of each individual optical fiber in the fiber optic bundle 132-2 can be positioned by placing the cladding surrounding the core in a v-shaped groove in the fourth spatial separator 432 that is dimensioned to precisely position the individual optical fiber including the core and the cladding. This can be done.

[0100] In some embodiments, spatial separators 422 and 432 may be implemented using any suitable components, such as those described above for spatial separator 302. In some embodiments, spatial separator 422 may be positioned such that a first interfering beam emitted from beam splitter 406 is received by a respective optical fiber, and spatial separator 432 may be positioned such that a second interfering beam emitted from beam splitter 406 is received by a respective optical fiber. As described below, an alignment system may be used to precisely align spatial separators 422 and 432 such that the interfering beams are received by respective optical fibers, which transmit the interfering beams to a detector. It should be noted that, typically, the interference fringes output to the fibers of fiber bundle 132-1 and the interference fringes output to the corresponding fibers of fiber bundle 132-2 will initially have the same polarization but will differ in phase by 180° (e.g., a phase shift induced in part by beam splitter 406). As the light propagates from mixer 400, the polarizations in each fiber diverge from one another (e.g., in the case of single mode fibers, the polarization of the light in a fiber of fiber bundle 132-1 will diverge from the polarization of the light in the corresponding fiber of fiber bundle 132-2). Although the phase relationship between the two signals is generally maintained (which may diverge depending on the polarization of the light), this facilitates the suppression of DC noise components and allows the use of a balanced detector to amplify the signal contained in the interference fringes.

[0101] FIG. 5 illustrates an example of components 500 that can be used to realize a portion of a detector for multi-beam optical coherence tomography of some embodiments of the subject matter disclosed herein. As shown in FIG. 5, there are various components that can be used to realize the detector 500. In some embodiments, the detector 500 can include a first optical junction 502 that can be used to couple each optical fiber of a fiber optic bundle (e.g., fiber optic bundle 132-1, etc.) to up to N individual optical fibers 504-506, and a second optical junction 512 that can be used to couple each optical fiber of a fiber optic bundle (e.g., fiber optic bundle 132-2, etc.) to up to N individual optical fibers 514-516. In some embodiments, the first optical junction 502 and / or the second optical junction 512 can be realized using any suitable component or components. For example, the optical junction 502 and / or the optical junction 512 can be realized using a junction box. As another example, each optical fiber of fiber bundle 132-1 and / or fiber bundle 132-2 can be coupled to a connector that can be mechanically coupled to a corresponding connector coupled to each of fibers 504-506 and / or 514-516 to optically couple the corresponding optical fibers. In some embodiments, optical junction 502 and / or optical junction 512 can be omitted. For example, each fiber of fiber bundle 132-1 and / or fiber bundle 132-2 can have a connector at the end thereof that is coupled to a corresponding detector. In some embodiments, fiber bundle 132-1 and / or fiber bundle 132-2 can be positioned such that light emitted from each fiber / waveguide of the fiber bundle is directed to a corresponding detection element (e.g., detectors 520-1-520-N, etc.) without the need for separate fibers 504-506 and / or 514-516 in between.

[0102] In some embodiments, detector 500 can include N balanced detectors 520-1 through 520-N. As shown in Figure 5, in some embodiments, each balanced detector 520 can be coupled to a pair of optical fibers that transmit interference fringes from a mixer (e.g., mixer 130, etc.). In the example shown in Figure 5, the two interference fringes received by a particular balanced detector 520 were generated using the same backscattered signal.

[0103] In some embodiments, each balanced detector 520 may include a pair of balanced photodetectors 522. Each pair of balanced photodetectors 522 generates an individual output signal that is input to a subtraction circuit 524 that subtracts one input from the other to reduce common mode noise in both interference fringes. The subtraction circuit 524 may output the interference fringe signal to one channel of a digital acquisition board 530 having at least N channels. In some embodiments, the digital acquisition board 530 may output an interference fringe signal that may be used to generate OCT data indicative of the structure of the sample at each location where each beam is backscattered from the sample.

[0104] In some embodiments, the balance detection operation may be implemented digitally (e.g., instead of using balance detector 520). For example, fiber bundle 132-2 and associated components may be omitted, and a detector (e.g., a photodetector, etc.) may be optically coupled to each fiber / waveguide of fiber bundle 132-1 (e.g., instead of balance detector 520, etc.). In such a case, one or more beams from fiber bundle 124 may be optically coupled to one or more fibers 132-1 without mixing with corresponding beams from fiber bundle 118, such that at least one fiber of fiber bundle 132-1 transmits only the reference arm light (e.g., while the other fibers of fiber bundle 132-1 transmit only the reference arm light). In one more specific example, one or more of the fibers in the fiber bundle 118 are not connected to the mixer 130. In another more specific example, the fiber bundle 124 may have more fibers than the fiber bundle 118, and more reference arm beams than sample arm beams. One or more detectors (e.g., a reference detector, etc.) may be optically coupled to the fibers / waveguides in the fiber bundle 132-1 that have only the reference arm light to record the intensity of the reference arm light, and another detector (e.g., a fringe detector, etc.) may record the intensity of the fringe signal. In another specific example, or in the alternative, a portion of the light output from the light source 102 (e.g., 1%, 2%, etc.) may be sent to one or more reference detectors without passing through the reference arm or sample arm to provide a signal substantially similar to the reference arm signal of the fibers in the fiber bundle 132-1. By subtracting the digital signal from the reference detector from the digital signal from the interference fringe detector, the digital fringe signals of the other detectors and noise (e.g., noise caused by fluctuations in laser power, etc.) can be removed.

[0105] 6A and 6B are top and side views of an example arrangement 600 of components that can be used to align optical fibers across a free space gap in some embodiments of the presently disclosed subject matter. In some embodiments, very precise alignment of components may be required to achieve strong optical coupling between components used to generate beams to interrogate a sample and generate interference patterns in free space using the techniques described herein. In some embodiments, alignment components 600 can be used to align beam forming optical fiber(s) (e.g., optical fiber 602, etc.) and focusing components (e.g., lens 606-1, etc.), and to align an assembly of optical fiber 602 and lens 601-1 with a corresponding assembly of optical fiber 620 and lens 606-2.

[0106] In some embodiments, the optical fibers 602 can be mechanically coupled to a six-axis stage 608-1 via a spatial separator 604-1, which allows the orientation of the beam-forming surface of the six-axis stage 608-1 and the optical fibers 602 to be maintained, thereby allowing the direction of the beam emitted from the optical fibers 602 to be adjusted relative to other components, such as the alignment component 600. In some embodiments, the spatial separator 604-1 fixes the orientation of a group of optical fibers relative to each other and to the six-axis stage 608-1, allowing the direction of the beam emitted from each of the optical fibers to be adjusted collectively.

[0107] In some embodiments, the six-axis stage 608-1 can be mechanically coupled to the lens 606-1 via a fixture 610-1, which can be attached to a tilt and rotation stage 612-1, which can be attached to a linear stage 614-1. In some embodiments, the position of the fixture 610-1 can be adjusted using the tilt and rotation stage 612-1 and / or the linear stage 614-1 without changing the relative orientation of the lens 606-1 and the optical fiber 604-1. In some embodiments, the alignment component 600 can be used to adjust the alignment of the optical fiber 602 and the optical fiber 620 to ensure that the beam emitted from the optical fiber 602 is received by the optical fiber 620. Additionally, in some embodiments, a power meter can be associated with each of multiple fiber channels (e.g., optical fiber 620 and at least one other optical fiber) associated with the output side of the alignment component, and the position of fixture 610-1 can be adjusted using tilt rotation stage 612-1 and / or linear stage 614-1 and / or the relative orientation of lens 606-1 and optical fiber 604-1 can be adjusted until the total optical power from all fiber channels is maximized.

[0108] In one specific example where each spatial separator 604 positions eight optical fibers, The spatial separator 604 can be mounted on a six-axis stage 608 that can control the relative position and angle (e.g., yaw and pitch) of the optical fiber fixed by the spatial separator 604 with respect to the optical lens 606, thereby providing eight collimated beams with aperture stops at least one focal length from the lens 606. By controlling the roll movement of the stage, the axis of the spatial separator 604 (e.g., an imaginary line intersecting the fiber core in the V-groove assembly) is aligned with the axis of the spatial separator of the opposing beam receiving component. The alignment between the six-axis stage 608 and the lens 606 can be fixed by a fixture 610 mounted on a tilting and rotating stage 612. By manipulating the tilting and rotating stage 612, the eight beams can be aligned together. A linear translation stage 614 can be used to match the distance between the lenses 606 to an appropriate distance (e.g., twice the focal length if the focal lengths of the lenses 606 are equal) to ensure that the eight emissions at one end of the spatial separator 604 can be coupled into optical fibers positioned by the downstream spatial separator.

[0109] In some embodiments, alignment component 600 can be used to align various optical components that can be used with the mechanisms described herein. For example, alignment component 600 can be used to align spatial separator 302, first lens 304, fifth lens 320, and spatial separator 322 to ensure that beams emitted from each optical fiber of fiber bundle 110 are optically coupled to each corresponding optical fiber of fiber bundle 118. As another example, alignment component 600 can be used to align components of mixer 400.

[0110] Figure 7A illustrates an example of a composite structural C-scan of a human finger generated by combining information from multiple optical coherence tomography signals acquired simultaneously using a system for multi-beam optical coherence tomography implemented in some embodiments of the presently disclosed subject matter, which are shown in Figure 7B. As shown in Figure 7B, multiple B-scans shown in panels (a)-(h) were acquired simultaneously using an OCT system implemented in some embodiments of the presently disclosed subject matter. The information contained in the multiple B-scans can be combined to generate a C-scan depicting a larger area of ​​the sample.

[0111] FIG. 8 is an example of multiple en face optical coherence tomography angiography images of the inside of a mouse ear generated simultaneously using multiple channels of a system for multi-beam optical coherence tomography implemented in some embodiments of the presently disclosed subject matter. 13A and 13B show a composite unfocused image generated from information generated using multiple channels of some embodiments of the presently disclosed subject matter.

[0112] 9 illustrates an example process 900 for simultaneously generating multiple optical coherence tomography images using multiple beams according to some embodiments of the presently disclosed subject matter. In some embodiments, the process 900 may begin at 900 by aligning the V-groove assembly and corresponding lenses of the multi-beam optical coherence tomography system to a particular performance level. For example, the alignment may be adjusted (e.g., using a calibration surface such as an optical mirror) until the optical coupling between each pair of optical fibers across the free space portion of the system (e.g., optical coupling between fiber bundle 110 and fiber bundle 118 or optical coupling between fiber bundle 118 and fiber bundles 132-1 and 132-2) can cause the received signal intensity of each channel of the detector to exceed a threshold value.

[0113] In some embodiments, process 900 may use signals received by one or more detectors (e.g., detector 134 and / or detector 520) as feedback signals that may be used to adjust the orientation and / or position of various components of the system. .

[0114] At 904, the process 900 can include acquiring OCT signals of the tissue sample across the N channels simultaneously. For example, the OCT signals can be acquired using the mechanisms described above across the N channels simultaneously using a free space interferometer using the techniques described above.

[0115] In some embodiments, the process 900 can acquire interference fringe signals corresponding to multiple A-scans while scanning the N beams over the sample (e.g., by translating the sample, translating the optics, and / or scanning with a galvanometer scanner).

[0116] In some embodiments, the process 900 can generate OCT data using the OCT signals received from the N channels. For example, the process 900 can convert the interference fringe signals received at 904 into A-scans and combine multiple A-scans from a particular channel to obtain a B-scan.

[0117] Process 900 can combine 908 the OCT data from the N channels to generate composite OCT data that describes the structure of the sample over a larger area than that acquired using a single channel. In some embodiments, process 900 can account for relatively small differences in the N channels when combining the data. For example, process 900 can axially shift the B-scan from each channel by an amount that corresponds to the path length difference from a reference path length for that particular channel.

[0118] FIG. 10 illustrates example hardware 1000 that can be used to implement an imaging device and / or a computer that can be used with some embodiments of the mechanism for multi-reference arm spectral domain optical coherence tomography implemented in some embodiments of the subject matter disclosed herein. For example, the hardware illustrated in FIG. 10 can be used to implement at least a portion of a system for multi-beam optical coherence tomography (such as system 100). As illustrated in FIG. 10, in some embodiments, the imaging system 1010 can include a hardware processor 1012, a user interface and / or display 1014, one or more communication systems 1018, a memory 1020, one or more light sources 1022, one or more electromagnetic wave detectors 1026, and / or one or more optical connectors 1026. In some embodiments, the hardware processor 1012 can be any suitable hardware processor or combination of hardware processors, such as a central processing unit (CPU), a graphics processing unit (GPU), a microcontroller (MCU), a field programmable gate array (FPGA), a dedicated image processor, etc. In some embodiments, the input(s) and / or display(s) 1014 may comprise any suitable display device(s), such as a computer monitor, a touch screen, a television, a transparent or translucent display, a head mounted display, etc., and / or input devices and / or sensors, such as a keyboard, a mouse, a touch screen, a microphone, a gaze tracking system, a motion sensor, etc., that can be used to receive user input.

[0119] In some embodiments, communications system 1018 may include any suitable hardware, firmware, and / or software for communicating information over communications network 1002 and / or any other suitable communications network. For example, communications system 1018 may include one or more transceivers, one or more communications chips, and / or one or more communications In a more specific example, the communication system 1018 may include a WiFi connection, a Bluetooth connection, a mobile phone connection, an Ethernet connection, and the like. It may include hardware, firmware and / or software that can be used to establish net connections, optical connections, and the like.

[0120] In some embodiments, communication network 1002 may be any suitable communication network or any suitable combination of communication networks. For example, communication network 1002 may be a WiFi network (which may include one or more wireless routers, one or more switches, etc.), a peer-to-peer network (e.g., a Bluetooth network, etc.), a cellular network (e.g., a 3G network, a 4G network, etc., including any of CDMA, GSM, LTE, LTE Advanced, WiMAX, etc.), or a combination of any of the above. 10 may include a wireless network (compliant with an appropriate standard), a wired network, etc. In some embodiments, communications network 1002 may be a local area network, a wide area network, a public network (e.g., the Internet), a private or semi-private network (e.g., a corporate or university intranet), any other suitable type of network, or any suitable combination of networks. Each of the communications links shown in FIG. 10 may be any suitable one or combination of communications links, such as a wired link, an optical fiber link, a WiFi link, a Bluetooth link, a cellular link, etc.

[0121] In some embodiments, the memory 1020 may include one or more suitable storage devices that may be used to store instructions, values, etc., for example, for the hardware processor 1012 to process image data generated by one or more photodetectors, for presenting content using the input / display 1014, for communicating with the computer 1030 via the communication system 1018, etc. The memory 1020 may include any suitable volatile memory, non-volatile memory, storage, any other suitable type of storage medium, or any suitable combination thereof. For example, the memory 1020 may include RAM, ROM, EEPROM, one or more flash drives, one or more hard disks, one or more solid state drives, one or more optical drives, etc. In some embodiments, the memory 1020 may have encoded therein a computer program for controlling the operation of the imaging system 1010. In some such embodiments, the hardware processor 1012 may execute at least a portion of a computer program to control one or more light sources and / or detectors (e.g., to obtain OCT data as described above with reference to FIG. 9), generate images and / or calculate values ​​(e.g., OCT images), send information to and / or receive information from the calculator 1030, and combine OCT images from multiple channels to generate a composite OCT image (e.g., as described above with reference to FIGS. 7-9).

[0122] In some embodiments, the imaging system 1010 may include one or more light sources 1022, e.g., coherent or incoherent light sources (e.g., lasers, light emitting diodes or combinations of light emitting diodes, white light sources, etc.), which may be broadband or narrower band light sources. For example, the bandwidth of the light source may be selected to provide a range of wavelengths that facilitates depth detection over the full imaging range of the OCT system. Additionally, in some embodiments, the light source 1022 may be associated with one or more filters.

[0123] In some embodiments, the imaging system 1010 may include one or more photodetectors 1024 (e.g., balanced detector 520, etc.), such as one or more photodiodes, and / or one or more image sensors (e.g., a CCD image sensor or a CMOS image sensor, etc., any of which may be a linear array or a two-dimensional array). For example, in some embodiments, the detector 1024 may be a It may include one or more detectors configured to detect particular wavelengths of light (e.g., using filters, using optics to direct light of different wavelengths to multiple portions of the detector(s), etc.).

[0124] In some embodiments, the imaging system 1010 can include one or more optical connectors 1026. For example, such optical connectors can be fiber optic connectors that form an optical connection between the light source(s) 1022 and / or detector 1024 and an optical fiber (e.g., an optical fiber as part of a fiber optic cable, etc.). For example, the optical connectors 1026 can be used to couple the light source 1022 to the sample arm and reference arm of the system 100 via a fiber coupler (e.g., fiber coupler 104, etc.).

[0125] In some embodiments, the computing device 1030 may include a hardware processor 1032, a display 1034, one or more inputs 1036, one or more communication systems 1038, and / or memory 1040. In some embodiments, the hardware processor 1032 may be any suitable hardware processor or combination of hardware processors, such as, for example, a CPU, a GPU, an MCU, an FPGA, a dedicated image processor, etc. In some embodiments, the display 1034 may include any suitable display device, such as, for example, a computer monitor, a touch screen, a television, a transparent or translucent display, a head mounted display, etc. In some embodiments, the input 1036 may include any suitable input device and / or sensor that can be used to receive user input, such as, for example, a keyboard, a mouse, a touch screen, a microphone, a gaze tracking system, a motion sensor, etc.

[0126] In some embodiments, communications system 1038 may include any suitable hardware, firmware, and / or software for communicating information over communications network 1002 and / or any other suitable communications network. For example, communications system 1038 may include one or more transceivers, one or more communications chips, one or more communications chipsets, etc. In one more specific example, communications system 1038 may include a WiFi connection, a Bluetooth® connection, a cellular connection, an Ethernet connection, a cellular network, a cellular telephone connection ... It may include hardware, firmware and / or software that can be used to establish a net connection or the like.

[0127] In some embodiments, memory 1040 may include one or more suitable storage devices that may be used to store instructions, values, etc. that may be used by hardware processor 1032 to present content using display 1034, to communicate with one or more imaging devices, etc. Memory 1040 may include any suitable volatile memory, non-volatile memory, storage, any other suitable type of storage medium, or any suitable combination thereof. For example, memory 1040 may include RAM, ROM, EEPROM, one or more flash drives, one or more hard disks, one or more solid state drives, one or more optical drives, etc. In some embodiments, memory 1040 may have encoded therein a computer program for controlling the operation of computing device 1030. In such an embodiment, the hardware processor 1032 may execute at least a portion of a computer program to receive content (e.g., image content, etc.) from one or more imaging devices (e.g., imaging device 1010, etc.), combine OCT images from multiple channels to generate a composite OCT image (e.g., such as those described above with reference to Figures 7-9), present content (e.g., images and / or values, etc.), transmit content to one or more other computers and / or imaging systems, etc.

[0128] In some embodiments, computing device 1030 may be any suitable computing device, such as a general purpose computer or a special purpose computer. For example, in some embodiments, computing device 1030 may be a smartphone, a wearable computer, a tablet computer, a laptop computer, a personal computer, a server, etc. As another example, in some embodiments, computing device 1030 may be a medical device, a system controller, etc.

[0129] FIG. 11 illustrates an example system 1100 for multi-beam optical coherence tomography implemented in some embodiments of the subject matter disclosed herein. The system 1100 includes a custom wavelength-swept laser operating at an A-scan rate of 125 kHz and a central wavelength of 1300 nm. 1% of the laser output is sent to a Mach-Zehnder interferometer (MZI) to generate calibration vectors for linear k-space resampling. The remaining 99% of the output is sent to a multi-beam OCT interferometer. In the reference arm, a 1×8 PLC splitter (available from FS, Inc., headquartered in New Castle, Delaware) is used to split the input into eight fields that are transmitted over eight optical fiber ribbons to a V-groove assembly (VGA, available from OZ Optics, Inc.). The fiber spacing in this V-groove assembly is 250 micrometers. In the sample arm, the eight sample fields are relayed from the VGA end face to eight focal points after passing through a 1 × 8 PLC. These eight focal points are displaced by 850 μm in the sample plane by two telescopes of the multibeam microscope. The microscope design was optimized using ZEMAX simulations to provide diffraction-limited focal points over a 6.8 × 6.8 mm field of view. A polarizing beam splitter (PBS) is used to align the polarization state of the illumination beam to one state, and a double pass through a quarter-wave plate (QWP) changes the polarization state of the return beam to be orthogonal to the input state, which causes the beam to be reflected by the PBS and coupled to another additional fiber ribbon through which it is sent to the detector. The eight reference and sample fields arriving at the beam splitter (BS) each give rise to eight interference fringes, and these interference fringes in each arm of the BS are coupled to the VGA for balanced detection. The eight interference fringes are acquired through the first eight channels of a 16-channel data acquisition board (AlazarTech). The MZI signal is obtained via the 9th channel of the board.

[0130] The path length differences of the eight channels of the system 1100 are shown in Table 1. These path length differences are due to the non-uniform fiber length of each ribbon and the different optical path length each beam travels through the microscope. The maximum path length difference was about 200 μm, which was an order of magnitude smaller than the penetration depth of the system. The microscope design provided sufficient aberration correction, with a measured coupling efficiency of the return beam into the fiber ribbon of 68.5%. The system sensitivity was 92.13 ± 1.13 dB with an average power of 3.7 mW incident on the sample for each channel. The variation in sensitivity between channels is mostly due to polarization dispersion in the fiber ribbon, which causes a channel-dependent polarization mismatch between the reference and sample fields. [Table 1]

[0131] 12 is a diagram illustrating an example 1200 of components that can be used to implement a portion of the phase and / or polarization modulator of some embodiments of the presently disclosed subject matter. In some embodiments, modulation component 1200 can use multiple phase modulators to provide phase and / or polarization modulation. In some embodiments, modulation component 142 and / or modulation component 144 can be implemented using modulation component 1200.

[0132] 12, a fiber coupler 1204 can be coupled to an electromagnetic wave guide 1202 (e.g., an optical fiber, etc.) of a sample arm or a reference arm (e.g., a sample arm or a reference arm of system 100). For example, the optical fiber 1202 can optically couple an input of the fiber coupler 1204 to a light source (e.g., via an optical coupler between the fiber coupler 1204 and a light source, such as light source 102). In some embodiments, the fiber coupler 1204 can receive light from the light source (e.g., via an electromagnetic wave guide such as an optical fiber and / or other optical components such as a fiber coupler optically coupled between an output of the light source 102 and an input port of the fiber coupler 1204, etc.) and output a first portion of the light at a first output and a second portion of the light at a second output. 12, an electromagnetic wave guide 1206 (e.g., a single mode optical fiber, a polarization-maintaining single mode optical fiber, etc.) may be optically coupled to a first output of the fiber coupler 1204, and another electromagnetic wave guide 1208 may be optically coupled to a second output of the fiber coupler 1204. In some embodiments, any suitable portion of the source light may be sent to the optical fiber 1206. For example, half of the source light received at the fiber coupler 1204 may be sent to each of the optical fibers 1206 and 1208. As another example, more than half of the source light received at the fiber coupler 1204 may be sent to either the optical fiber 1206 or the optical fiber 1208, and less than half may be sent to the other optical fiber.

[0133] In some embodiments, the optical fiber 1206 can be optically coupled to the first phase modulator 1210 such that a first portion of the light received at the fiber coupler 1204 is input to an input of the first phase modulator 1210. Further, in some embodiments, the optical fiber 1208 can be optically coupled to the second phase modulator 1212 such that a second portion of the light received at the fiber coupler 1204 is input to an input of the second phase modulator 1212.

[0134] In some embodiments, the optical modulator 1210 and the optical modulator 1212 can be optically coupled to a polarization beam combiner 1218. As shown in FIG. 12, a polarization control 1214 can be disposed between the phase modulator 1210 and the polarization beam combiner 1218. In some embodiments, the polarization control 1214 can align the polarization state at the polarization beam combiner 1218 to a first polarization state. Additionally or alternatively, a polarization control 1216 can be disposed between the phase modulator 1212 and the polarization beam combiner 1218. In some embodiments, the polarization control 1216 can align the polarization state at the polarization beam combiner 1218 to a second polarization state.

[0135] Alternatively, in some embodiments, polarization-maintaining optical fiber can be used to optically couple the various components. For example, polarization-maintaining optical fiber can be used to optically couple the phase modulator 1210 and the polarization beam combiner 1218. As another example, polarization-maintaining optical fiber can be used to optically couple the phase modulator 1212 and the polarization beam combiner 1218. In some embodiments, polarization control 1214 and / or polarization control 1216 can be omitted (e.g., when polarization-maintaining optical fiber is used to optically couple the components).

[0136] In some embodiments, a polarization controller (e.g., polarization controller 1214 and / or polarization controller 1 216, etc.) and / or polarization-maintaining optical fibers can orthogonalize the light traveling along the two paths shown in FIG. 12 between the fiber coupler 1204 and the polarization beam combiner 1218 at the polarization beam combiner 1218.

[0137] In some embodiments, the light output by the polarizing beam combiner 1218 has a polarization that is a function of the phase of the light from the two paths (e.g., when the polarization between the light traversing the two paths shown in FIG. 12 between the fiber coupler 1204 and the polarizing beam combiner 1218 is orthogonal).

[0138] In some embodiments, the phase modulator 1210 and the phase modulator 1212 can each induce a particular phase shift that does not affect the polarization of the light emitted from the polarization beam combiner 1218, but changes the phase of the output by a particular amount. For example, the phase modulator 1210 and the phase modulator 1212 can be configured to induce a 90° phase shift, which can be used to induce a 90° phase shift between the reference arm light and the sample arm light. However, this is merely an example, and the phase modulator 1210 and the phase modulator 1212 can be configured to induce any amount of phase shift. Alternatively, the phase modulator 1210 can be configured to induce a first phase shift and the phase modulator 1212 can be configured to induce a second, separate phase shift different from the first phase shift, which can cause the light emitted from the polarization beam combiner 1218 to be output in a different polarization state than would be emitted if the phase modulators 1210 and 1212 did not induce the first and second phase shifts. For example, phase modulator 1210 can be configured to induce a -90° phase shift and phase modulator 1212 can be configured to induce a positive 90° phase shift (or vice versa), which can cause the polarization of the light emitted from polarization beam combiner 1218 to be output orthogonal to the polarization state of the light emitted from polarization beam combiner 1218 without a phase shift. However, this is by way of example only, and phase modulator 1210 and phase modulator 1212 can be configured to induce a variety of polarization states.

[0139] In some embodiments, the phase modulator driver 1230 can provide drive signals to the phase modulator 1210 and / or the phase modulator 1212 to control the phase shift caused by the phase modulator. For example, the phase modulator driver 1230 can provide drive signals to control the phase and / or polarization of the light output by the polarization beam combiner 1218. In one particular example, the phase modulator driver 1230 can provide drive signals that cause a particular modulation (e.g., modulation of phase and / or polarization, etc.) during a first period of time and provide drive signals that cause a different modulation during a second period of time. In such an example, the first period of time can correspond to an A-line, a portion of an A-line, one or more pulses of the wavelength-stepped frequency comb source, etc., and the second period of time can correspond to a subsequent A-line, another portion of the same A-line, one or more subsequent pulses of the wavelength-stepped frequency comb source, etc. In addition, the phase modulator driver 1230 can also provide a drive signal to the phase modulator 1210 and / or the phase modulator 1212 (or inhibit the supply of a drive signal) that does not impart modulation to the output from the polarization beam combiner 1218.

[0140] In some embodiments, the output of the polarization beam combiner 1218 can be optically coupled to an input of a fiber coupler 1220, which can pass a first portion of the light to an optical fiber 1222 for output as an output from the component 1200. The fiber coupler 1220 passes a second portion of the light to an optical fiber 1224, which can be coupled to a detector 1228 via a polarizer 1226. In some embodiments, the output of the detector 1228 can indicate the polarization of the light output from the fiber coupler 1220, and the output of the detector 1228 can be used as feedback to a phase modulator driver 1230 to maintain a constant output from the polarization beam combiner. For example, feedback from detector 1228 can be used by phase modulator driver 1230 to control phase drift of phase modulators 1210 and / or 1212. In some embodiments, fiber coupler 1220 can be configured to pass a majority of the received light to the input of optical fiber 1222 (e.g., more than 50%, more than 75%, more than 85%, more than 90%, etc.). In some embodiments, fiber coupler 1220, polarizer 1226, and detector 1228 can be omitted.

[0141] In some embodiments, a polarization controller may be placed just before the phase modulator 1210 and / or the phase modulator 1212 (e.g., proximate the input port of the phase modulator) to align the polarization of the light input to the modulator to a particular relative orientation with respect to the modulator. Additionally or alternatively, an optical polarizer may be placed proximate the fiber coupler 1204. For example, one optical polarizer may be placed proximate the input port of the fiber coupler 1204. As another example, the optical polarizers may be located near the output ports of the fiber coupler 1204 (e.g., one polarizer at each output port). As yet another example, optical polarizers may be placed along the optical fiber 1206 and the optical fiber 1208. In such an embodiment, a polarizer or set of polarizers may be used to remove variations in the light polarization as a function of time or wavelength. In some embodiments, a polarization controller may be placed before any one polarizer, or any of the combined polarizers, to control the alignment of the input polarization state with the axis of the polarizer.

[0142] FIG. 13 illustrates an example of a component 1300 that can be used to realize a portion of the sampling optics of the system for multi-beam optical coherence tomography of some embodiments of the presently disclosed subject matter, the sampling optics of the system shown in FIG. 1. In some embodiments, the component 1300 can be used to couple (e.g., via one or more other optical components) the fiber bundle 110 and the fiber bundle 118 to a sample. As shown in FIG. 13, each of the N fibers of the fiber bundle 110 (e.g., each of the N fibers of a ribbon fiber optic cable) can be coupled to a first port of an optical circulator 1302-1 to 1302-N. In some embodiments, a second port of each optical circulator 1302 can be coupled to a corresponding optical fiber of the fiber bundle 1304 (e.g., each fiber of a ribbon fiber optic cable) that can transmit light to and from the sample. The third port of each optical circulator 1302 can be coupled to a respective one of the N fibers (e.g., each fiber of a ribbon optical fiber cable) of the fiber bundle 118 that can transmit the light received from the sample to a detector (e.g., to detector 134 via mixer 130).

[0143] FIG. 14 illustrates another example of components 1400 that can be used to realize a portion of the sampling optics of the system for multi-beam optical coherence tomography of some embodiments of the subject matter disclosed herein, as shown in FIG. 1. In some embodiments, components 1400 can be used to couple fiber bundle 110 and fiber bundle 118 to a sample (e.g., via one or more other optical components). As shown in FIG. 14, each of the N fibers of fiber bundle 110 (e.g., each of the N fibers of a ribbon fiber optic cable) can be coupled to a first port of a respective corresponding coupler, and each of the N fibers of fiber bundle 118 (e.g., each of the fibers of a ribbon fiber optic cable) can be coupled to a second port of a respective corresponding coupler. In some embodiments, the N couplers can be realized using a planar lightwave circuit (PLC) 1402. In some embodiments, each of the N fibers of fiber bundle 1404 (e.g., each of the N fibers of a ribbon fiber optic cable) can be coupled to a third port of a respective corresponding coupler. Fiber bundle 1404 transmits light to and from the sample, and light returning from the sample can be transmitted by each coupler of PLC 1402 to each fiber of fiber bundle 118, which transmits the light received from the sample to a detector (e.g., The light from the sample may be transmitted to the fiber bundle 118 via mixer 130, to detector 134, etc. In some embodiments, the PLC 1402 may be configured to equally couple the first port of each coupler to the third port and the fourth port, and equally couple the third port of each coupler to the first port and the second port. In such an embodiment, half of the light output from fiber bundle 110 may be output to each fiber of fiber bundle 1404, and half of the light from the sample output by fiber bundle 1404 may be output to each fiber of fiber bundle 118.

[0144] Alternatively, in some embodiments, the PLC 1402 can be configured to asymmetrically couple the first port of each coupler between the third port and the fourth port, and asymmetrically couple the third port of each coupler between the first port and the second port. For example, the PLC 1402 can be configured to send less than half of the light output from the fiber bundle 110 to each fiber of the fiber bundle 1404 (e.g., 1%, 5%, 10%, 20%, 25%, 30%, etc.). As another example, the PLC 1402 can be configured to send more than half of the light from the sample output from the fiber bundle 1404 to each fiber of the fiber bundle 118 (e.g., 99%, 95%, 90%, 80%, 75%, 70%, etc.). In such a case, the couplers of the PLC 1402 may be configured to output light received at a first port to a fourth port and a third port in a particular ratio (e.g., 99 / 1, 95 / 5, 90 / 10, etc.) and to output light received at the third port to the second port and the first port in the same particular ratio. In some embodiments, the couplers of the PLC 1402 may be configured asymmetrically to reduce optical loss of light transmitted by the PLC 1402 between each fiber of the fiber bundle 1404 and each fiber of the fiber bundle 118. It is noted that although FIG. 14 shows N couplers configured by the PLC 1402, the couplers may be implemented using any suitable technology or any suitable combination of technologies. For example, a discrete fiber connector (e.g., similar to the fiber connector 104) may be used to couple the fiber bundle 110 to the fiber bundle 1404 and the fiber bundle 1404 to the fiber bundle 118.

[0145] 15 illustrates another example of components 1500 that can be used to realize the focusing portion of the sampling optics of the system for multi-beam optical coherence tomography of some embodiments of the subject matter disclosed herein, the focusing portion of the sampling optics of the system shown in FIG. 1. In some embodiments, the focusing optics 1500 can include a spatial separator 1504 configured to mechanically position the distal ends of the optical fibers of the optical fiber bundle 1502 (e.g., fiber bundle 1304, fiber bundle 1404, etc.) such that a face of each optical fiber of the optical fiber bundle 1502 is held in a specific relative position and a specific relative orientation with respect to other optical elements of the focusing optics 1500. For example, each core of the individual optical fibers of the optical fiber bundle 1502 can be positioned by placing the cladding surrounding the core in a V-shaped groove dimensioned to precisely position the individual optical fibers of the optical fiber bundle 1502, including the core and the cladding. The spatial separator 302 may position the fibers at specific locations defined in one dimension (e.g., using a linear V-groove, etc.) or may position the fibers at specific locations defined in two dimensions (e.g., an array, etc.). In some embodiments, the spatial separator 1504 may be implemented using any suitable component. For example, the spatial separator 1504 may be implemented as a V-groove assembly, such as a single mode V-groove assembly available from OZ Optics, Inc., headquartered in Ottawa, Canada. In another example, spatial separator 1504 may be an array of wells or through-holes drilled into a material (e.g., glass, silicon dioxide, etc.) in which individual fibers of the set of fibers are secured such that the faces of each fiber are precisely aligned with one another. In such examples, the wells or through-holes may be formed mechanically (e.g., using a mechanical drilling tool, etc.) and / or using other processing techniques (e.g., photolithography, etc.). In such examples, the wells or through-holes of the array may be arranged in any suitable one- or two-dimensional layout (e.g., arranged in a row or a column). , arranged in a set of rows or columns, arranged as multiple concentric circles, etc.) In yet another example, the spatial separator 1504 can be implemented as one or more multicore fibers, each of whose optical cores is positioned at a specific relative position to one another in the multicore fiber.

[0146] In some embodiments, a first lens 1506 can be optically coupled to the optical fibers of the fiber bundle 1502. As shown in FIG. 15, the first lens 1506 can be positioned such that the face of each optical fiber of the fiber bundle 1502 coincides with the focal length f5 of the first lens 1506 and emits a beam from a point at a particular radial distance from the optical axis of the first lens 1506. As shown in FIG. 15, the first lens 1506 can be a biconvex lens. However, this is only one example and many types of lenses can be used to realize the first lens 1506 (and other lenses shown in the drawings as biconvex lenses), similar to the lens described above with reference to FIG. 3. In some embodiments, if a spatial separator 1504 is used to align the optical fibers of the fiber bundle 124 such that all reference beams emitted by the optical fibers of the fiber bundle 1502 are coplanar, the positioning of the spatial separator 1504 relative to the first lens 1506 can be such that the optical axis of the first lens 1506 is coplanar with the reference beams. For example, the above configuration can facilitate alignment of one or more other components relative to the spatial separator 1504 and the first lens 1506.

[0147] In some embodiments, each optical fiber of the fiber bundle 1502 can emit an individual beam towards a first face of a first lens 1506, which can focus light received from the fiber bundle 1502 at a focal length f5 distal to the first lens 1506. This allows the beams from each of the optical fibers to converge at a focal point of the first lens 1506. In the absence of other optical components, the beams diverge after the focal point and can be reflected across the optical axis to be focused onto the sample at a distance of 2*f5 from the face of the optical fiber.

[0148] In some embodiments, the collection optics 1500 may include a reflector 1508 that deflects the light received from the first lens 1506 toward the sample 116. The reflector 1508 may be positioned such that the reflecting surface of the reflector 1508 coincides with the focal length f5 of the first lens 1506. In some embodiments, the reflector 1508 may be implemented using any suitable reflecting surface, such as a plane mirror, a galvanometer, a microelectromechanical system (MEMS) type mirror, a polygon mirror scanner, or the like. In some embodiments, the angle of the reflector 1508 may be fixed or adjustable. For example, in some embodiments, the reflector 1508 may be a surface of a galvanometer scanner that may be used to control the angle that the reflector 1508 makes with the optical axis of the first lens 1506.

[0149] In some embodiments, the beam emitted from the first lens 1506 may converge at the reflective surface of the reflector 1508 and begin to diverge as it travels towards a first surface of the second lens 1510. The second lens 1510 may be positioned such that the reflective surface of the reflector 1508 coincides with a focal length f6 of the second lens 1510. In some embodiments, the focal length of the second lens 1510 may be equal to or different from the focal length of the first lens 1506 (e.g., the focal length of the first lens 1506 may be equal to or different from the focal lengths of the first lens 304, the second lens 308, the third lens 312 and / or the fourth lens 316).

[0150] In some embodiments, the second lens 1510 is configured to focus the diverging beam so that when it intersects with the surface of the sample 116, it becomes a substantially parallel beam traveling parallel to the optical axis of the second lens 1510. 15, in some embodiments, the second lens 1510 can focus each beam to a point at a focal length f6. For example, if the reflecting surface of the reflector 1508 is located at a distance equal to the focal length f6 from the first surface of the second lens 1510, each beam can converge at a distance equal to the focal length f6 on the second surface side of the second lens 1510 and begin to diverge after passing the distance equal to the focal length f6 (e.g., forming a beam waist at the focal length f6).

[0151] In some embodiments, the sample 116 may backscatter one or more portions of each beam incident on the sample. The depth to which the light is backscattered may depend on the structure of the sample 116 and / or the wavelength of the incident light. This may result in different amounts of phase difference between the backscattered light and the light propagating in the reference arm. Additionally, the polarization of the light backscattered by the sample 116 may also be inverted.

[0152] In some embodiments, light backscattered by the sample 116 can return through the collection optics 1500 following the same path as the incident light from the light source 102, with most of the backscattered light being sent on a path that coincides with the spatial separator 1504 and back through the fiber bundle 1502 towards the coupling optics.

[0153] In some embodiments, the sampling optics 112 may be implemented using a combination of the coupling optics 1300 and the collection optics 1500 or a combination of the coupling optics 1400 and the collection optics 1500 .

[0154] FIG. 16 illustrates an example of optical components 1600 that can be used to realize a mixing portion of a multi-beam interferometer for multi-beam optical coherence tomography of some embodiments of the presently disclosed subject matter. In some embodiments, the mixing components 1600 can combine N beams of light received from a sample arm and a reference arm. As shown in FIG. 16, each of the N fibers of the fiber bundle 118 (e.g., each of the N fibers of a ribbon fiber optic cable) can be coupled to a first port of a corresponding fiber coupler 1602, and each of the N fibers of the fiber bundle 124 (e.g., each of the fibers of a ribbon fiber optic cable) can be coupled to a second port of the corresponding fiber coupler 1602. For example, in some embodiments, a first fiber of the fiber bundle 118 can be optically coupled to a first port of the fiber coupler 1602-1, and a corresponding first fiber of the fiber bundle 124 can be optically coupled to a second port of the fiber coupler 1602-1.

[0155] In some embodiments, N individual fiber couplers 1602 can be used to realize the N couplers. In some embodiments, a first fiber (e.g., fiber 1604-1A, etc.) can be optically coupled to a third port of each fiber coupler 1602, and a second fiber (e.g., fiber 1604-1B, etc.) can be optically coupled to a fourth port of each fiber coupler 1602. Fiber 1604-1A and fiber 1604-1B can transmit the interference pattern to a detector (e.g., detector 134, etc.). For example, fiber 1604-1A can optically couple the third port of fiber coupler 1602-1 to a first port of a balanced detector (e.g., balanced detector 520-1, etc.), and fiber 1604-1B can optically couple the third port of fiber coupler 1602-1 to a second port of the balanced detector. Similarly, two fibers can be used to optically couple the third and fourth ports of each of the other N-1 fiber couplers 1602 to a detector (e.g., a balanced detector). Note that typically, the interference fringes output at each port of a particular fiber coupler 1602 will initially have the same polarization but will differ in phase by 180°. As light propagates from the fiber coupler 1602, the polarization in each fiber may diverge (e.g., may become sigma-degraded) while the phase relationship between the two interference fringe signals is generally maintained. (In the case of a single-mode fiber, the polarization of the light in fiber 1604-1A may diverge from the polarization of the light in fiber 1604-1B.) This facilitates the suppression of the DC noise component and allows the use of a balanced detector to amplify the signal contained in the interference fringes.

[0156] In some embodiments, the balance detector may be omitted. For example, as described above with reference to FIG. 5, the balance detection operation may be implemented digitally (e.g., instead of using the balance detector 520). For example, a single detector (e.g., a single photodetector) may be optically coupled to each fiber coupler 1602 (e.g., instead of using the balance detector 520). In such a case, one or more beams from the fiber bundle 124 may be optically coupled to one detector without mixing with corresponding beams from the fiber bundle 118 such that at least one fiber 1604 (e.g., 1604-NA, etc.) transmits only the reference arm light (e.g., while the other fiber 1604 transmits the interference fringe signal). In such a case, the fibers 1604-1B to 1604-NB may be omitted. In a more specific example, one or more fibers of the fiber bundle 118 are not optically connected to the detector 134 via the mixer 130. As another more specific example, fiber bundle 124 may have more fibers than fiber bundle 118, and more beams in the reference arm than in the sample arm. As yet another specific example, in addition to or instead of the above, a portion (e.g., 1%, 2%, etc.) of the light output from light source 102 may be sent to one or more reference detectors without passing through the reference or sample arms, providing a signal substantially similar to the reference arm signal of the fibers in fiber bundle 124. One or more detectors (e.g., reference detectors, etc.) may be optically coupled to the fibers / waveguides of fiber bundle 124 having only the reference arm light to record the intensity of the reference arm light, and other detectors (e.g., fringe detectors, etc.) may be provided to record the intensity of the interference fringe signal. The digital signal from the reference detector may be subtracted from the digital signal from the interference fringe detector to remove the digital fringe signal of the other detectors, noise (e.g., noise caused by laser power fluctuations, etc.).

[0157] In some embodiments, approximately half of the light received at the first port of each fiber coupler 1602 can be output at the third and fourth ports of the fiber coupler 1602, and approximately half of the light received at the second port of each fiber coupler 1602 can be output at the third and fourth ports of the fiber coupler 1602. In such embodiments, light from the sample arm and the reference arm can be mixed in the fiber coupler 1602 to produce an interference pattern that is output at the third and fourth ports of the fiber coupler 1602.

[0158] FIG. 17 illustrates another example of optical components 1700 that can be used to implement the mixing portion of a multi-beam interferometer for multi-beam optical coherence tomography according to some embodiments of the presently disclosed subject matter.

[0159] In some embodiments, mixing component 1600 can combine N beams of light received from the sample arm and the reference arm. As shown in FIG. 17, each of the N fibers of fiber bundle 118 (e.g., each of the N fibers of a ribbon fiber optic cable) can be coupled to a first port of a corresponding coupler implemented using PLC 1702, and each of the N fibers of fiber bundle 124 (e.g., each of the fibers of a ribbon fiber optic cable, etc.) can be coupled to a second port of a corresponding fiber coupler implemented using PLC 1702.

[0160] In some embodiments, the PLC 1702 can implement N couplers. In some embodiments, a first fiber (such as fiber 1704-1A) of the PLC 1702 can implement N couplers. A first fiber (e.g., fiber 1704-1B) may be optically coupled to the third port of each coupler of PLC 1702, and a second fiber (e.g., fiber 1704-1B) may be optically coupled to the fourth port of each coupler of PLC 1702. Fiber 1704-1A and fiber 1704-1B may transmit the interference pattern to a detector (e.g., detector 134). For example, fiber 1704-1A may optically couple the third port of the first coupler of PLC 1702 to the first port of the balanced detector (e.g., balanced detector 520-1), and fiber 1704-1B may optically couple the third port of the first coupler of PLC 1702 to the second port of the balanced detector. Similarly, two fibers may be used to optically couple the third and fourth ports of each of the other N-1 couplers of PLC 1702 to a detector (e.g., balanced detector). Alternatively, as described above with reference to FIG. 16, the balanced detection operation may be implemented digitally (e.g., instead of using balanced detector 520).

[0161] In some embodiments, approximately half of the light received at a first port of each coupler of PLC 1702 can be output at a third and fourth port of that coupler, and approximately half of the light received at a second port of each coupler of PLC 1702 can be output at a third and fourth port of fiber coupler 1702. In such embodiments, light from the sample arm and the reference arm can be mixed in the coupler to produce an interference pattern that is output at the third and fourth ports of the coupler.

[0162] [Other embodiments having various features] Example embodiment 1: 1. A system for multi-beam optical coherence tomography comprising: a sample arm configured to be optically coupled to a light source; and a reference arm configured to be optically coupled to the light source, the sample arm comprising: a first optical fiber having a proximal end optically coupled to the light source and a distal end; a first splitter optically coupled to the distal end of the first optical fiber and optically coupled to a proximal end of each of a first plurality of optical fibers having n optical fibers; and a first plurality of optical components configured to receive a plurality of respective beams from each of the plurality of optical fibers, direct the plurality of beams toward a sample, receive a plurality of spatially separated backscattered light samples from the sample, each backscattered light sample corresponding to one of the first plurality of beams, and detect the plurality of backscattered light samples. and a second plurality of optical components configured to combine each of the plurality of backscattered light samples with a beam emitted by a corresponding one of the second plurality of optical fibers to produce a plurality of interference fringes and to transmit each of the plurality of interference fringes to a corresponding channel of the detector having a plurality of detection channels, the detector being configured to output optical coherence tomography data indicative of a structure of the sample at a plurality of locations where the plurality of backscattered light samples were generated.

[0163] Example embodiment 2: The system of example embodiment 1, wherein the light source is a wavelength-swept laser.

[0164] Example 3: The system of example 1, wherein the light source is a wavelength-stepped frequency comb light source.

[0165] Embodiment 4: The method of any one of embodiments 1 to 3, wherein the sample arm further comprises a first spatial separator mechanically coupled to a distal end of each optical fiber of the first plurality of optical fibers. Any one system.

[0166] Example Embodiment 5: The system of Example 4, wherein the first spatial separator comprises a V-groove assembly.

[0167] Example 6: The system of any one of Examples 1 to 5, wherein the reference arm further comprises a second spatial separator mechanically coupled to a distal end of each optical fiber of the second plurality of optical fibers.

[0168] Embodiment 7: The system of any one of embodiments 1 to 6, wherein the particular spectral range is centered at 1300 nm.

[0169] Embodiment 8: The system of any one of embodiments 1-7, wherein the first splitter comprises a planar lightwave circuit splitter that receives light from the first optical fiber and splits the received light into multiple outputs.

[0170] Example 9: The system of any one of Examples 1 to 8, wherein the first plurality of optical components includes a first lens having a first surface optically coupled to the first plurality of optical fibers and a second surface, the first lens configured to focus the plurality of beams at a first focal length corresponding to a focal length of the first lens, a surface that deflects light received from the second surface of the first lens toward a first surface of a second lens and deflects light received from the first surface of the second lens toward the second surface of the first lens, and a second lens whose first surface is optically coupled to the surface, the second lens having a second surface that directs light received from the surface toward the sample and receives the plurality of backscattered light samples from the sample.

[0171] Example embodiment 10: the first plurality of optical components include a third lens having a first surface optically coupled to the first plurality of optical fibers and a second surface, the third lens configured to focus the plurality of beams at a first focal length corresponding to a focal length of the third lens; and a polarizing beam splitter having a first port, a second port, and a third port, the polarizing beam splitter having a first interface that transmits light having a first polarization and polarizes light having a second polarization, the beam splitter transmits light having the first polarization received at the first port to the second port and polarizes light having the second polarization received at the second port toward the third port, the first port is optically coupled to a second surface of the third lens to receive the plurality of beams from the third lens, the second port emits the plurality of beams toward a fourth lens and polarizes the plurality of beams toward the fourth lens. 10. The system of Example 9, wherein a first surface of the fourth lens is optically coupled to the second port to receive a plurality of backscattered light samples from a fifth lens, the third port configured to emit the plurality of samples toward a fifth lens, the first surface of the fourth lens is optically coupled to the second port and the fourth lens has a second surface, the beamsplitter further comprises a quarter wave plate optically coupled to the second surface of the fourth lens and to the first surface of the first lens, the first surface of the first lens is optically coupled to the quarter wave plate, the fifth lens has a first surface optically coupled to the third port of the polarizing beamsplitter and a second surface optically coupled to a third plurality of optical fibers, and the first plurality of optical fibers and the third plurality of optical fibers are oriented such that light emitted from each of the first plurality of optical fibers is sent to a corresponding optical fiber of the third plurality of optical fibers.

[0172] Example 11: The first plurality of optical components each have a first port and a second port. the first port of each of the plurality of optical circulators is optically coupled to the light source via a corresponding optical fiber of the first plurality of optical fibers, the second port of each of the plurality of optical circulators is optically coupled to the sample via a corresponding optical fiber of a third plurality of optical fibers, and the third port of each of the plurality of optical circulators is optically coupled to the second plurality of optical components via a corresponding optical fiber of a fourth plurality of optical fibers.

[0173] Example 12: The system of any one of Examples 1 to 9, wherein the first plurality of optical components comprises a second planar lightwave circuit having a plurality of optical couplers, each having a first port, a second port, and a third port, and each of the first ports of each of the plurality of optical couplers is optically coupled to the light source via a corresponding optical fiber of the first plurality of optical fibers, each of the second ports of each of the plurality of optical couplers is optically coupled to the sample via a corresponding optical fiber of a third plurality of optical fibers, and each of the third ports of each of the plurality of optical couplers is optically coupled to the second plurality of optical components via a corresponding optical fiber of a fourth plurality of optical fibers.

[0174] Example 13: The system of Example 12, wherein each of the plurality of optical couplers outputs a first percentage of the light received at the first port from the third port, outputs a second percentage of the light received at the first port from the fourth port, outputs the first percentage of the light received at the third port from the first port, and outputs the second percentage of the light received at the third port from the second port.

[0175] Example Embodiment 14: The system of Example 13, wherein the ratio of the first rate to the second rate is about 1.

[0176] Example embodiment 15: The system of example embodiment 14, wherein the ratio of the first rate to the second rate is less than 1.

[0177] Example 16: The system of any one of Examples 10 to 15, further comprising a spatial separator mechanically coupled to a distal end of each of the third plurality of optical fibers and arranged to optically couple each of the third plurality of optical fibers to a first surface of the first lens.

[0178] Example 17: The system of any one of Examples 1 to 16, wherein the second plurality of optical components comprises a beam splitter having a first port, a second port, and a third port, the first port configured to receive light emitted by the second plurality of optics, the second port configured to receive the plurality of backscattered light samples, and the third port configured to output the plurality of interference fringes.

[0179] Example 18: The system of Example 17, wherein the detector comprises a plurality of balanced detectors having a first port and a second port, each corresponding to each channel of the detector, and the beam splitter further has a fourth port configured to output a second plurality of interference fringes, and each of the plurality of balanced detectors receives one of the plurality of interference fringes and a corresponding interference fringe of the second plurality of interference fringes, and outputs a signal based on both interference fringes.

[0180] Example 19: The second plurality of optical components comprises a plurality of optical couplers each having a first port, a second port, a third port, and a fourth port, the first port being coupled to the light source via each of the second plurality of optical fibers, and the second ports being coupled to the light source via each of the second plurality of optical fibers. the third port is coupled to the sample via each of a fourth plurality of optical fibers, the third port is coupled to each of the plurality of detection channels, and the fourth port is coupled to each of the plurality of detection channels.

[0181] Example 20: The system of Example 19, wherein each of the plurality of optical couplers is a discrete fiber coupler.

[0182] Example Embodiment 21: The system of Example Embodiment 19, further comprising a third planar lightwave circuit, said planar lightwave circuit comprising said plurality of optical couplers.

[0183] Example 22: A system of any one of Examples 1 to 21, wherein the reference arm further comprises a modulation component disposed between the light source and the second splitter, the modulation component being configured to at least modulate the polarization of the light input to the second splitter.

[0184] Example 23: A system of any one of Examples 1 to 22, wherein the reference arm further comprises a modulation component disposed between the light source and the second splitter, the modulation component being configured to at least modulate the phase of the light input to the second splitter.

[0185] Example 24: The system of Example 1, wherein the reference arm further comprises a modulation component disposed between the light source and the second splitter, the modulation component being configured to modulate the phase of the light input to the second splitter and to modulate the polarization of the light input to the second splitter.

[0186] Example 25: A system of any one of Examples 1 to 24, wherein the sample arm further comprises a modulation component disposed between the light source and the first splitter, the modulation component being configured to at least modulate the polarization of the light input to the first splitter.

[0187] Example 26: A system of any one of Examples 1 to 25, wherein the sample arm further comprises a modulation component disposed between the light source and the first splitter, the modulation component being configured to at least modulate the phase of the light input to the first splitter.

[0188] Example 27: A system of any one of Examples 1 to 24, wherein the sample arm further comprises a modulation component disposed between the light source and the first splitter, the modulation component being configured to modulate the phase of the light input to the first splitter and to modulate the polarization of the light input to the first splitter.

[0189] Example 28: The system of any one of Examples 22 to 27, wherein the modulation component comprises a coupler having a first port, a second port, and a third port optically coupled to the light source, a first phase modulator having a first port and a second port optically coupled to the second port of the coupler, a second phase modulator having a first port and a second port optically coupled to the third port of the coupler, and a beam combiner having a first port optically coupled to the first phase modulator, a second port optically coupled to the second phase modulator, and a third port.

[0190] Example 29: The modulation component further comprises a polarization control portion optically coupled to the second port of the coupler and the first port of the first phase modulator. system.

[0191] Example 30: The system of example 28 or 29, wherein the modulation component further comprises a polarization control portion optically coupled to a third port of the coupler and a port of the second phase modulator.

[0192] Example embodiment 31: A system for multi-beam optical coherence tomography comprising: a first splitter arranged to receive a first light from a light source and output a portion of the first light to each of a first plurality of waveguides; optical components arranged to receive light from the first plurality of waveguides and direct the received light as a plurality of beams to the sample such that each of the plurality of beams strikes a different lateral position on the sample, and collect a plurality of backscattered light samples from the different lateral positions of the sample; a second splitter arranged to receive a second light from the light source and output a portion of the second light to each of a second plurality of waveguides as a plurality of reference light samples; a mixer arranged to receive the plurality of backscattered light samples and the plurality of reference light samples and combine each backscattered light sample with a corresponding reference light sample to output a plurality of interference fringes; and a detector arranged to receive the plurality of interference fringes and output a plurality of optical coherence tomography signals each indicative of a structure at each lateral position of the sample.

[0193] Example embodiment 32: The system of example embodiment 31, wherein the plurality of beams comprises eight beams.

[0194] Example 33: The system of example 31 or 32, wherein the first splitter comprises a planar lightwave circuit splitter.

[0195] Example 34: A system of any one of Examples 31 to 33, wherein the optical component comprises a plurality of optical circulators, each of which is arranged to receive one of the plurality of beams from one of the first plurality of waveguides, direct the received beam towards the sample, and direct a backscattered light sample towards the detector.

[0196] Example 35: A system of any one of Examples 31 to 33, wherein the optical component comprises a plurality of optical couplers, each of which is arranged to receive one of the plurality of beams from one of the first plurality of waveguides, direct the received beam toward the sample, and direct a backscattered light sample toward the detector.

[0197] Example 36: The system of any one of Examples 31 to 35, further comprising the light source.

[0198] In some embodiments, any suitable computer-readable medium may be used to store instructions for performing the functions and / or processes described herein. For example, in some embodiments, the computer-readable medium may be a transitory or non-transitory medium. For example, a non-transitory computer-readable medium may be a magnetic medium (e.g., hard disk, floppy disk, etc.), an optical disk (e.g., compact disk, digital video disk, Blu-ray disk, etc.), a semiconductor medium (e.g., RAM, flash, etc.), or a combination of both. memory, electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), any suitable medium that does not lose or lose any form of persistence during transfer, and / or any suitable As another example, transitory computer-readable media may include signals on a network, wires, conductors, optical fibers, circuits, or any suitable medium that does not lose or lose any form of permanence during transmission, or any suitable intangible medium.

[0199] While the subject matter of the present disclosure has been described above with reference to specific embodiments and examples, it will be apparent to those skilled in the art that the present invention is not necessarily so limited, and that numerous other embodiments, examples, uses, modifications, and variations therefrom are intended to be encompassed within the scope of the appended claims. The disclosures of each patent and publication cited herein are incorporated by reference in their entirety into the disclosure of this application, to the same extent as if each such patent and publication were individually incorporated by reference into the disclosure of this application.

[0200] Various features and advantages of the invention are set forth in the following claims.

Claims

1. 1. A system for multi-beam optical coherence tomography comprising: a sample arm configured to be optically coupled to a light source; and a reference arm configured to be optically coupled to the light source, The sample arm is a first optical fiber having a proximal end optically coupled to the light source and a distal end; a first splitter optically coupled to a distal end of the first optical fiber and optically coupled to a proximal end of each optical fiber of a first plurality of n optical fibers; a first plurality of optical components; Equipped with The first plurality of optical components include: receiving a plurality of respective beams from a respective one of the plurality of optical fibers; directing the plurality of beams toward a sample; receiving a plurality of spatially separated backscattered light samples from the sample, each backscattered light sample corresponding to one of the first plurality of beams; directing said plurality of backscattered light samples towards a detector; It is structured as follows: The reference arm is a second optical fiber having a proximal end optically coupled to the light source and a distal end; a second splitter optically coupled to a distal end of the second optical fiber and optically coupled to a proximal end of each optical fiber of a second plurality of n optical fibers; a second plurality of optical components; and Equipped with The second plurality of optical components include: combining each of the plurality of backscattered light samples with a beam emitted by a corresponding one of the second plurality of optical fibers to produce a plurality of interference fringes; Sending each of the plurality of interference fringes to a corresponding channel of the detector having a plurality of detection channels. It is structured as follows: The detector is configured to output optical coherence tomography data indicative of a structure of the specimen at a plurality of locations where the plurality of backscattered light samples were generated. A system characterized by:

2. the light source is a wavelength swept laser; The system of claim 1 .

3. The light source is a wavelength-stepped frequency comb light source; The system of claim 1 .

4. The sample arm further comprises: a first spatial separator mechanically coupled to a distal end of each optical fiber of the first plurality of optical fibers. Equipped with The system according to any one of claims 1 to 3.

5. the first spatial separator comprises a V-groove assembly; The system of claim 4.

6. The reference arm further comprises: a second spatial separator mechanically coupled to a distal end of each optical fiber of the second plurality of optical fibers. Equipped with The system according to any one of claims 1 to 3.

7. The particular spectral range is centered at 1300 nm. The system of claim 1 .

8. the first splitter comprises a planar lightwave circuit splitter that receives light from the first optical fiber and splits the received light into n outputs. The system of claim 1 .

9. The first plurality of optical components include: a first lens having a first surface optically coupled to the first plurality of optical fibers and a second surface, the first lens configured to focus the plurality of beams at a first focal length corresponding to a focal length of the first lens; a surface that deflects light received from the second surface of the first lens toward the first surface of a second lens and that deflects light received from the first surface of the second lens toward the second surface of the first lens; a second lens having a first surface optically coupled to the surface, the second lens having a second surface that directs light received from the surface toward the sample and receives the plurality of backscattered light samples from the sample; having The system according to any one of claims 1 to 3, 6 and 7.

10. The first plurality of optical components include: a third lens having a first surface optically coupled to the first plurality of optical fibers and a second surface, the third lens configured to focus the plurality of beams at a first focal length corresponding to a focal length of the third lens; a polarizing beam splitter having a first port, a second port, and a third port, the polarizing beam splitter having a first interface that transmits light having a first polarization and polarizes light having a second polarization; Equipped with the beam splitter transmits light having the first polarization received at the first port to the second port and deflects light having the second polarization received at the second port towards the third port; the first port is optically coupled to a second surface of the third lens to receive the plurality of beams from the third lens; the second port is optically coupled to a first surface of the fourth lens to emit the beams toward the fourth lens and to receive a plurality of backscattered light samples from the fourth lens; the third port is configured to emit the plurality of samples toward a fifth lens; a first surface of the fourth lens optically coupled to the second port and the fourth lens having a second surface; the beam splitter further comprises a quarter wave plate optically coupled to the second surface of the fourth lens and to the first surface of the first lens; a first surface of the first lens optically coupled to the quarter wave plate; The fifth lens is optically coupled to the third port of the polarizing beam splitter. a first surface and a second surface optically coupled to the third plurality of optical fibers; the first plurality of optical fibers and the third plurality of optical fibers are oriented such that light emitted from each optical fiber of the first plurality is transmitted to a corresponding optical fiber of the third plurality of optical fibers; 10. The system of claim 9.

11. The first plurality of optical components include: a plurality of optical circulators each having a first port, a second port, and a third port; Equipped with a first port of each of the plurality of optical circulators is optically coupled to the light source via a corresponding optical fiber of the first plurality of optical fibers; a second port of each of the plurality of optical circulators is optically coupled to the sample via a corresponding optical fiber of a third plurality of optical fibers; The system of any one of claims 1 to 3, 6 and 7, wherein each of the third ports of the plurality of optical circulators is optically coupled to the second plurality of optical components via a corresponding optical fiber of a fourth plurality of optical fibers.

12. a spatial separator mechanically coupled to a distal end of each optical fiber of the third plurality and disposed to optically couple each optical fiber of the third plurality to a first surface of the first lens. The system of claim 10.

13. The first plurality of optical components include: a second planar lightwave circuit comprising a plurality of optical couplers each having a first port, a second port, and a third port; Equipped with a first port of each of the plurality of optical couplers optically coupled to the light source via a corresponding optical fiber of the first plurality of optical fibers; a second port of each of the plurality of optical couplers is optically coupled to the sample via a corresponding optical fiber of a third plurality of optical fibers; a third port of each of the plurality of optical couplers is optically coupled to the second plurality of optical components via a corresponding optical fiber of a fourth plurality of optical fibers; The system according to any one of claims 1 to 3, 6 and 7.

14. Each of the plurality of optical couplers comprises: outputting a first fraction of the light received at the first port through the third port; outputting a second fraction of the light received at the first port through a fourth port; outputting the first fraction of the light received at the third port through the first port; outputting the second fraction of the light received at the third port from the second port; The system of claim 13.

15. a ratio of the first proportion to the second proportion is about 1; 15. The system of claim 14.

16. the ratio of the first rate to the second rate is less than 1; 15. The system of claim 14.

17. the second plurality of optical components comprises a beam splitter having a first port, a second port, and a third port; the first port is configured to receive light emitted by the second plurality of optics; the second port is configured to receive the plurality of backscattered light samples; the third port is configured to output the plurality of interference fringes. The system according to any one of claims 1 to 3, 6 and 7.

18. the detector comprises a plurality of balanced detectors having a first port and a second port, the plurality of balanced detectors corresponding to respective channels of the detector; the beam splitter further comprising a fourth port configured to output a second plurality of interference fringes; each of the plurality of balance detectors receives one of the plurality of interference fringes and a corresponding one of the second plurality of interference fringes, and outputs a signal based on both interference fringes; 20. The system of claim 17.

19. The second plurality of optical components include: A plurality of optical couplers each having a first port, a second port, a third port, and a fourth port. Equipped with the first port is coupled to the light source via each of the second plurality of optical fibers; the second port is coupled to the sample via each of a fourth plurality of optical fibers; the third port is coupled to each of the plurality of detection channels; the fourth port is coupled to each of the plurality of detection channels; The system according to any one of claims 1 to 3, 6 and 7.

20. each of the plurality of optical couplers is a discrete fiber coupler; 20. The system of claim 19.

21. further comprising a third planar lightwave circuit; the planar lightwave circuit comprises the plurality of optical couplers; 20. The system of claim 19.

22. the reference arm further comprises a modulation component disposed between the light source and the second splitter; the modulation component is configured to at least modulate the polarization of light input to the second splitter; The system of claim 1 .

23. the reference arm further comprises a modulation component disposed between the light source and the second splitter; the modulation component is configured to modulate at least a phase of light input to the second splitter; The system of claim 1 .

24. the reference arm further comprises a modulation component disposed between the light source and the second splitter; The modulation component includes: modulating the phase of light input to the second splitter; Modulating the polarization of light input to the second splitter It is configured as follows: The system of claim 1 .

25. the sample arm further comprises a modulation component disposed between the light source and the first splitter; the modulation component is configured to at least modulate the polarization of light input to the first splitter; The system of claim 1 .

26. the sample arm further comprises a modulation component disposed between the light source and the first splitter; the modulation component is configured to modulate at least a phase of light input to the first splitter; The system of claim 1 .

27. the sample arm further comprises a modulation component disposed between the light source and the first splitter; The modulation component includes: modulating the phase of light input to the first splitter; Modulating the polarization of light input to the first splitter It is configured as follows:

25. The system of claim 1 or 24.

28. The modulation component includes: a coupler having a first port optically coupled to the light source, a second port, and a third port; a first phase modulator having a first port optically coupled to the second port of the coupler, and a second port; a second phase modulator having a first port optically coupled to the third port of the coupler and a second port; a beam combiner having a first port optically coupled to the first phase modulator, a second port optically coupled to the second phase modulator, and a third port; Equipped with A system according to any one of claims 22 to 27.

29. The modulation component further comprises: a polarization control portion optically coupled to the second port of the coupler and to the first port of the first phase modulator; Equipped with 30. The system of claim 28.

30. The modulation component further comprises: a polarization control part optically coupled to a third port of the coupler and to a port of the second phase modulator; Equipped with 30. The system of claim 28.

31. 1. A system for multi-beam optical coherence tomography, comprising: a first splitter positioned to receive a first light from a light source and output a portion of the first light into each of the first plurality of waveguides; an optical component arranged to receive light from the first plurality of waveguides, direct the received light as a plurality of beams to the sample such that each beam strikes a different lateral location on the sample, and collect a plurality of backscattered light samples from the different lateral locations on the sample; a second splitter positioned to receive second light from the light source and output a portion of the second light into each of a second plurality of waveguides as a plurality of reference light samples; a mixer arranged to receive the plurality of backscattered light samples and the plurality of reference light samples and to combine each backscattered light sample with a corresponding reference light sample to output a plurality of interference fringes; a detector arranged to receive the interference fringes and output a plurality of optical coherence tomography signals indicative of a structure at each lateral location of the sample; A system comprising:

32. the plurality of beams comprises eight beams; 32. The system of claim 31.

33. the first splitter comprises a planar lightwave circuit splitter; 33. A system according to claim 31 or 32.

34. the optical component comprises a plurality of optical circulators; Each of the plurality of optical circulators comprises: receiving a beam of the plurality of beams from a waveguide of the first plurality of waveguides; directing the received beam towards the sample; Directing a sample of the backscattered light towards the detector. It is arranged as follows: A system according to any one of claims 31 to 33.

35. the optical component comprises a plurality of optical couplers; Each of the plurality of optical couplers comprises: receiving a beam of the plurality of beams from a waveguide of the first plurality of waveguides; directing the received beam towards the sample; Directing a sample of the backscattered light towards the detector. It is arranged as follows: A system according to any one of claims 31 to 33.

36. Further comprising the light source. A system according to any one of claims 31 to 35.

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