Switchable multi-configuration OCT

Abstract

To provide an optical coherence tomography (OCT) imaging system.SOLUTION: An optical coherence tomography, OCT, imaging system for imaging an object comprises an interferometer and an optical coupler. The interferometer comprises a sample arm and a reference arm. The reference arm comprises a first optical fiber and an optical switch. The optical switch is controllable to guide reference light from the first optical fiber to a selected optical path of N optical paths, where N is an integer greater than or equal to 2, and each of the N optical paths has a respective optical path length and / or chromatic dispersion that differs from the respective optical path length and / or chromatic dispersion of each of the other optical paths. The optical coupler guides the reference light propagating along the selected optical path to a second optical fiber. The OCT imaging system detects an interference between the reference light propagating via the second optical fiber and sample light propagating via the sample arm after scattered by the object.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Exemplary embodiments of this specification generally relate to the field of optical coherence tomography (OCT) imaging systems.

Background Art

[0002] Optical coherence tomography (OCT) is an imaging technique based on low coherence interferometry and is widely used to obtain high-resolution two-dimensional and three-dimensional images of light-scattering media such as biological tissues.

[0003] OCT imaging systems can be classified as time-domain OCT (TD-OCT) or Fourier-domain OCT (FD-OCT) (also called frequency-domain OCT) according to how the depth range is achieved. In TD-OCT, the optical path length of the reference arm of the interferometer of the imaging system changes over time during the acquisition of the reflectivity profile (referred to as the "imaging target" in this specification) of the scattering medium being imaged by the OCT imaging system, and the reflectivity profile is generally called a "depth scan" or "axial scan" ("A-scan"). In FD-OCT, the spectral interferogram resulting from the interference between the reference arm and the sample arm of the interferometer at each A-scan position is Fourier-transformed to simultaneously acquire all points along the depth of the A-scan without requiring a change in the optical path length of the reference arm. FD-OCT can enable imaging much faster than the scanning of the sample arm mirror in the interferometer because all backscattering from the sample is measured simultaneously. Two general types of FD-OCT are spectral-domain OCT (SD-OCT) and swept-source OCT (SS-OCT). In SD-OCT, a broadband light source delivers many wavelengths to the imaging target, and a spectrometer is used as a detector to measure all wavelengths simultaneously. In SS-OCT (also called time-encoded frequency-domain OCT), the light source is swept over a certain wavelength range, and the time output of the detector is converted into a spectral interference.

[0004] OCT imaging systems can also be classified as point scanning (also known as "point detection" or "scanning point"), line field, or full field, depending on how the imaging system is configured to acquire OCT data laterally. Point scanning OCT imaging systems typically acquire OCT data by scanning a sample beam focused to a point on the surface of the object to be imaged along a single virtual line on the surface of the object to be imaged (which may be, for example, a straight line or curved to define a circle or spiral), or along a set of (usually substantially parallel) virtual lines (so-called "scanning lines") on the surface of the object to be imaged, and acquiring an axial depth profile (A scan) for each of multiple points along the line(s) at one point at a time, and constructing OCT data that includes a one-dimensional or two-dimensional array of A scans representing the two-dimensional or three-dimensional (volume) reflectance profile of the sample. Line scanning OCT imaging systems acquire OCT data by generating a ray, for example, by shaping a nominally circular light beam into a ray using a cylindrical lens or Powell lens, scanning the ray across the surface of the object to be imaged (i.e., providing line-field illumination), and for each scanning position along the line, acquiring axial depth profiles (A scans) in parallel for each of a number of points along the line, thereby constructing OCT data that includes a one-dimensional or two-dimensional array of A scans representing the two-dimensional or three-dimensional (volume) reflectance profile of the sample. Full-field OCT imaging systems typically use a halogen lamp (rather than a laser source) and a 2D detector array such as a CCD camera to acquire OCT data in the form of frontal (lateral) oriented tomographic images recorded in parallel by the 2D detector array.

[0005] The range of positions along the propagation direction of sample illumination in which an OCT imaging system can acquire data from the object being imaged can be determined (at least partially) by the optical path length of the reference arm and the coherence length of the light used to image the object being imaged. In ophthalmic applications, an OCT imaging system can usually not image both the anterior and posterior segments of the eye unless changes are made to the interference settings in the OCT imaging system, specifically to the adjustment of the reference arm to provide the necessary changes in its optical path length. Such changes are usually implemented using a mechanical mechanism that changes the optical path length of the reference arm by moving a mirror located at the end of the reference arm along the optical propagation axis within the reference arm, for example, by moving the mirror back and forth along the axis using a linear actuator. Such mechanisms are often slow to implement the required changes in the optical path length of the reference arm.

[0006] However, some FD-OCT imaging systems have been developed to simultaneously image the anterior and posterior segments of the eye using full-range OCT techniques that attempt to recover the full imaging depth of the OCT imaging system by resolving the complex conjugate ambiguity induced by the Hermitian Fourier transform of the spectral interferogram. Dispersively coded full-range OCT optical configurations tend to require a higher level of chromatic dispersion within the reference arm than conventional OCT configurations of the type described above, and the reference arm can be configured to image either the anterior or posterior segment while maintaining dispersion match with the sample arm. [Overview of the project]

[0007] According to a first exemplary embodiment of this specification, an optical coherence tomography (OCT) imaging system for imaging an object to be imaged is provided. The OCT imaging system comprises a light source, a sample arm, a reference arm, and an interferometer having an optical splitter arranged to split light from the light source into sample light propagating along the sample arm and reference light propagating along the reference arm. The reference arm comprises a reference arm optical fiber arranged to guide the reference light, an optical switch controllable to guide at least a portion of the reference light from the reference arm optical fiber to a selected optical path among N optical paths, where N is an integer of 2 or more, and each of the N optical paths has at least one of the optical path length or chromatic dispersion of each of the other optical paths among the N optical paths, and an optical coupler arranged to guide the at least portion of the reference light propagating along the selected optical path to an output optical fiber. The OCT imaging system further comprises a photodetector arranged to detect interference light resulting from interference between at least a portion of the reference light propagating through the output optical fiber and the sample light that propagates through the sample arm after being scattered by the object to be imaged.

[0008] In the above OCT imaging system, the optical switch may be a 1×N optical switch having N output ports, the optical coupler may be an N×1 optical coupler having N input ports, and each of the N optical paths may have an optical fiber connecting each of the N output ports to each of the N input ports. At least some of the optical fibers may have different path lengths. Additionally or alternatively, each of the N optical paths may have its own dispersing element, each dispersing element of the dispersing element is arranged to provide its own level of chromatic dispersion of the reference light propagating through the optical path having the dispersing element. The N×1 optical coupler may include an N×1 optical fiber coupler or (active) N×1 optical switch that can control the reference light to couple one input port of the N input ports corresponding to one output port of the N output ports coupled by the 1×N optical switch to an output optical fiber.

[0009] The OCT imaging system or any of the above-described modifications thereof may further include a controller, and the OCT imaging system may be capable of operating in multiple imaging modes to image different ranges of the object at different depths along the propagation direction of sample light toward the object. In this case, during the operation of the OCT imaging system in each imaging mode, the controller may control optical switches to direct the reference light from the reference arm optical fiber into each of N optical paths, each having a different optical path length, such that the phase difference between the sample light, which is scattered from a depth within each range of the object and received by the photodetector, and the reference light, which is propagated through the output optical fiber and received by the photodetector, is less than a predetermined threshold. Furthermore, the object to be imaged may be an eye, and the OCT imaging system may be capable of operating in at least one of a first imaging mode for imaging a first portion of the anterior segment of the eye, a second imaging mode for imaging a first portion of the posterior segment of the eye, or a third imaging mode for imaging a second portion of the anterior segment and a second portion of the posterior segment of the eye.

[0010] When the OCT imaging system is capable of operating in a first imaging mode, the controller may be configured to control an optical switch to direct a reference light from a reference arm optical fiber into a first optical path of N optical paths, the first optical path comprising a first dispersion element configured such that the level of chromatic dispersion of sample light, which is scattered by a first portion of the anterior segment of the eye and then received by a photodetector, matches the level of chromatic dispersion of reference light (LR) which is propagated through the output optical fiber and then received by a photodetector.

[0011] If the OCT imaging system is capable of operating in a second imaging mode, the controller may be configured to control an optical switch to direct reference light from a reference arm optical fiber into a second optical path of N optical paths, the second optical path comprising a second dispersion element configured such that the level of chromatic dispersion of sample light received by a photodetector after being scattered by a first portion of the posterior segment of the eye matches the level of chromatic dispersion of reference light received by a photodetector after being propagated through the output optical fiber.

[0012] If the OCT imaging system is capable of operating in a third imaging mode, the controller may be configured to control an optical switch to direct the reference light from the reference arm optical fiber to a third optical path among N optical paths, the third optical path providing a level of chromatic dispersion of the reference light propagated through the output optical fiber and received by the photodetector that is greater than the level of chromatic dispersion of the sample light received by the photodetector after being scattered by a second portion of the anterior segment and / or a second portion of the posterior segment of the eye.

[0013] The OCT imaging system may further include a lens and a lens movement mechanism for moving the lens in and out of the optical path within the sample arm of the interferometer. In a first imaging mode, the controller may be configured to control the lens movement mechanism to move the lens in the optical path within the sample arm of the interferometer so that a first portion of the anterior segment of the eye is imaged through the lens during operation of the OCT imaging system in the first imaging mode. In a second imaging mode, the controller may be configured to control the lens movement mechanism to move the lens out of the optical path within the sample arm of the interferometer so that a first portion of the posterior segment of the eye is imaged without using the lens during operation of the OCT imaging system in the second imaging mode. Alternatively, the OCT imaging system may further include a pupil alignment module configured to align the focus of the OCT imaging system with the pupil of the eye based on the image of the anterior segment. In this case, the OCT imaging system can be configured to operate in a first imaging mode while the pupil alignment module is operating to align the focus of the OCT imaging system with the pupil of the eye, and then, after the pupil alignment module has operated, to operate in a second imaging mode to align the focus of the OCT imaging system with the pupil of the eye.

[0014] In any of the OCT imaging systems or their modifications described above, the optical switch may include a micro-electromechanical switch, a micro-mechanical switch, a micro-optical switch, and / or an optical switch driven by a stepper motor. Additionally or alternatively, the OCT imaging system may further include an optical power monitor, and the optical switch may be controllable to switch between (i) simultaneously directing a first portion of the reference light from the reference arm optical fiber to a selected optical path among N optical paths and a second portion of the reference light from the reference arm optical fiber to the optical power monitor, and / or (ii) directing at least a portion of the reference light (LR) from the reference arm optical fiber to a selected optical path among N optical paths and directing at least a portion of the reference light (LR) from the reference arm optical fiber to the optical power monitor.

[0015] According to a second exemplary aspect of this specification, an OCT imaging system for imaging an object to be imaged is also provided. The OCT imaging system comprises a light source and an interferometer having a sample arm, a reference arm, and an optical splitter arranged to split light from the light source into sample light propagating along the sample arm and reference light propagating along the reference arm. The reference arm comprises a first mirror arranged to reflect the reference light from the optical splitter back towards the optical splitter when the reference light from the optical splitter is incident on the first mirror, a second mirror, and a mirror movement mechanism controllable to move the second mirror in and out of the optical path of the reference light propagating toward the first mirror such that when the second mirror is moved out of the optical path, the reference light is reflected back towards the optical splitter by the first mirror, and when the second mirror is moved in the optical path, the reference light is reflected back towards the optical splitter by the second mirror instead of the first mirror. The OCT imaging system further includes a photodetector positioned to detect interference light resulting from the interference between a reference light reflected back toward the optical splitter and sample light scattered by the object being imaged and propagating through the sample arm.

[0016] A second exemplary embodiment of the OCT imaging system may be operable in a first imaging mode for imaging a first range of depths of an object along the propagation direction of sample light toward the object, and a second imaging mode for imaging a second range of depths of the object along the propagation direction of sample light toward the object, wherein the first range of depths is different from the second range of depths. The OCT imaging system may further include a controller arranged to control a mirror movement mechanism such that, during operation of the OCT imaging system in the first imaging mode, the second mirror is outside the optical path such that the phase difference between sample light scattered from the first range of depths of the object and received by the photodetector and reference light reflected back toward the optical splitter by the first mirror and received by the photodetector is smaller than a predetermined threshold, and during operation of the OCT imaging system in the second imaging mode, the second mirror is inside the optical path such that the phase difference between sample light scattered from the second range of depths of the object and received by the photodetector and reference light reflected back toward the optical splitter by the second mirror and received by the photodetector is less than a predetermined threshold. The OCT imaging system may be capable of operating in a first imaging mode in which a portion of the posterior segment of the eye is imaged as a first depth range of the target to be imaged, and a second imaging mode in which a portion of the anterior segment of the eye is imaged as a second depth range of the target to be imaged.

[0017] A third exemplary aspect of this specification also provides a computer implementation method for controlling the imaging of an object by an OCT imaging system, the OCT imaging system comprising a light source, a sample arm, a reference arm, and an interferometer having an optical splitter arranged to split light from the light source into sample light propagating along the sample arm and reference light propagating along the reference arm. The reference arm comprises a reference arm optical fiber arranged to guide the reference light, an optical switch controllable to guide at least a portion of the reference light from the reference arm optical fiber to a selected optical path among N optical paths, where N is an integer of 2 or more, and each of the N optical paths has at least one of the optical path length and chromatic dispersion different from at least one of the optical path length and chromatic dispersion of the other optical paths among the N optical paths, and an optical coupler arranged to guide the at least portion of the reference light propagating along the selected optical path to an output optical fiber. The OCT imaging system further comprises a photodetector arranged to detect interference light resulting from interference between at least a portion of the reference light output from the output optical fiber and the sample light that propagates through the sample arm after being scattered by the object to be imaged. The computer implementation method includes receiving a signal indicating a range of imaging depths over which an image of a portion of the object to be imaged is acquired; configuring the OCT imaging system to acquire an image of the portion of the object to be imaged over the indicated range of imaging depths by selecting one of the N optical paths based on the received signal; and controlling the optical switch to direct the reference light from the reference arm optical fiber to the selected optical path. The computer implementation method further includes controlling the OCT imaging system configured to acquire an image of the portion of the object to be imaged.

[0018] A computer program is also provided that, when executed by a computer, contains computer-readable instructions that cause the computer to perform the above-described method. The computer program may be stored in a non-temporary computer-readable storage medium or carried by signals.

[0019] Hereafter, illustrative embodiments will be described in detail, only as non-limiting examples, with reference to the accompanying drawings described below. Similar reference numerals appearing in different drawings may indicate identical or functionally similar elements unless otherwise indicated. [Brief explanation of the drawing]

[0020] [Figure 1] Figure 1 is a schematic diagram of an OCT imaging system according to a first exemplary embodiment described herein. [Figure 2] Figure 2 is a schematic diagram of a scanning system that forms part of an OCT imaging system in a first exemplary embodiment. [Figure 3] Figure 3 is a schematic diagram of an exemplary mounting configuration of the reference arm in an exemplary embodiment. [Figure 4] Figure 4 is a schematic diagram of an exemplary mounting configuration of the reference arm in an alternative exemplary embodiment. [Figure 5] Figure 5 is a schematic diagram of programmable signal processing hardware that can be configured to perform at least some of the functions of the OCT data processing hardware described herein. [Figure 6] Figure 6 is a flowchart illustrating the process by which the controller of the OCT imaging system in the first exemplary embodiment controls the OCT imaging system to capture an image target. [Figure 7] Figure 7 is a schematic diagram of an OCT imaging system according to a second exemplary embodiment of this specification. [Modes for carrying out the invention]

[0021] Exemplary embodiments of the OCT imaging system described in this specification address at least some of the drawbacks recognized by the inventors, which include the inability to image an object to be imaged over a wide depth range (e.g., imaging over substantially the entire depth range of a human eye from the anterior segment to the posterior segment) without making time-consuming changes to the configuration of the interference settings in the OCT imaging system as described above, which may reduce the efficiency of using the OCT imaging system, or the inability to switch between a full-range imaging mode and one or more standard OCT imaging modes (having a narrower depth of field and requirements for dispersion matching between the sample arm and the reference arm of the interferometer).

[0022] More specifically, the inventors have devised an OCT imaging system that can switch the light in the reference arm of the interferometer of the OCT imaging system to propagate along a selected optical path among a plurality of different optical paths available within the reference arm. Each of the available optical paths can have a respective optical path length and / or level of wavelength dispersion set to meet the requirements of the associated imaging mode of the OCT imaging system. The imaging mode of the OCT imaging system can be changed simply by controlling an optical switch to switch the available optical paths within the reference arm so as to provide the required optical path length and / or level of wavelength dispersion. For example, in ophthalmic applications, the proposed OCT imaging system can switch the OCT imaging system configuration to operate in an imaging mode for imaging the anterior segment of the eye, another imaging mode for imaging the posterior segment of the eye, and a further imaging mode for full-range OCT imaging of the eye.

[0023] Here, exemplary embodiments of an OCT imaging system and a method of controlling imaging of an object to be imaged by the OCT imaging system will be described in detail with reference to the accompanying drawings.

[0024] (First Exemplary Embodiment) FIG. 1 is a schematic diagram of an OCT imaging system 100 for imaging an imaging target (object) 105, which may be a human eye as in this exemplary embodiment. The OCT imaging system 100 includes a light source 110, an interferometer 120, and a photodetector 130. The OCT imaging system 100 may further include a controller 140 as in the exemplary embodiment. Further, the OCT imaging system 100 may be a point-scanning swept-source OCT (SS-OCT) imaging system that further includes a scanning system 150 as in this exemplary embodiment. However, more generally, the OCT imaging system 100 may be a point-scanning, line-scanning, or full-field OCT imaging system that uses a mirror-based optical system, a lens-based optical system, or an optical system including at least one mirror and at least one lens to image a portion of an eye (or other object), and may be any OCT imaging system known in the art, such as any Fourier-domain OCT (FD-OCT) imaging system as described later.

[0025] The light source 110 may be a sweep light source, for example, in the form of a wavelength-swept (or "tunable wavelength") laser, arranged to generate a light beam LB having wavelengths that are swept over a certain wavelength range (preferably linearly) during imaging of the object to be imaged 105 by the OCT imaging system 100, as in this exemplary embodiment. The tunable wavelength laser may be of a type known to those skilled in the art, such as a Fourier-domain mode-locked (FDML) laser with a Fabry-Perot tunable wavelength filter or polygonal scanning mirror, or one based on a microcavity tunable wavelength laser with a microelectromechanical system (MEMS). The central frequency of the sweep light source is selected depending on the object to be imaged 105 and is typically in the near-infrared or infrared portion of the spectrum (typically about 1050 nm), for example in ophthalmic applications. Alternatively, in exemplary embodiments where the OCT imaging system 100 takes the form of an SD-OCT imaging system, the light source 110 may be a broadband light source in the form of a superluminescent diode, for example, arranged to generate a light beam LB having a certain range of wavelengths (i.e., a broad spectral content) simultaneously during imaging of the object to be imaged 105 by the OCT imaging system 100. In some exemplary embodiments, the light source 110 may include further components such as one or more cylindrical lenses for shaping the light beam LB, a light source aperture, and / or one or more collimating lenses for collimating the light beam LB.

[0026] The interferometer 120 comprises a sample arm 121, a reference arm 122, and a first optical splitter 123, and may also include a second optical splitter 124, as in this exemplary embodiment. The first optical splitter 123 is positioned to split light LB from the light source 110 into sample light LS propagating along the sample arm 121 and reference light LR propagating along the reference arm 122. The sample light LS propagating along the sample arm 121 in a first direction is scattered by the object to be imaged 105. The sample light propagating through the sample arm 121 after being scattered by the object to be imaged 105 (i.e., the collected light LC which is at least a portion of the light scattered by the object to be imaged 105 during imaging of the object to be imaged 105) propagates along the sample arm 121 in a second direction opposite to the first direction, toward the first optical splitter 123. The sample light LS may be guided to the imaging target 105 by the scanning system 150, as in this exemplary embodiment, and the collected light LC may be collected by the scanning system 150. The collected light LC passes through the first optical splitter 123 and proceeds toward the second optical splitter 124. The second optical splitter 124 is configured to combine the collected light LC and the reference light LR to form an inference light LI resulting from the interference between the reference light LR and the collected light LC exiting the reference arm 122. The interference light LI propagates toward the photodetector 130.

[0027] The first optical splitter 123 and the second optical splitter 124 may comprise beam splitters as shown in the illustration, as in this exemplary embodiment. However, the first optical splitter 123 and the second optical splitter 124 are not limited in this respect and may instead take the form of a 2x2 fiber coupler (e.g., a 50:50 fiber coupler) or a 2x1 fiber coupler, respectively. Furthermore, in some exemplary embodiments, for example, if the reference arm 122 guides the reference light LR to a mirror, which is positioned to reflect the reference light LR back to the first optical splitter 123 through the reference arm 122, the second optical splitter 124 may be omitted, and the first optical splitter 123 is positioned to combine the collected light LC and the reference light LR to form an inference light LI resulting from the interference between the reference light LR and the collected light LC exiting the reference arm 122.

[0028] The scanning system 150 may be configured to perform a two-dimensional point scan of the optical beam LS over the object to be imaged 105, as in this exemplary embodiment, and to collect optical LC scattered by the object to be imaged 105 during the point scan. Thus, the scanning system 150 is configured to acquire an A scan at each scanning position distributed two-dimensionally over the surface of the object to be imaged 105 by sequentially illuminating the scanning positions with the optical beam LS, one scanning position at a time, and collecting at least a portion of the optical LC scattered by the object to be imaged 105 at each scanning position. The scanning system 150 can perform a two-dimensional point scan using any suitable scanning pattern known to those skilled in the art, such as unidirectional scanning (a pair of parallel scan lines following a common direction, along which the scan lines extend), serpentine scanning, or helical scanning.

[0029] The scanning system 150 may be a mirror-based system comprising a scanning element and a mirror, as in this exemplary embodiment, and the scanning system 150 is arranged to perform two-dimensional point scanning by scanning an optical beam LS over an imaging target 105 via the mirror. An example of such a scanning system capable of performing wide-field retinal scanning is described in International Publication No. 2014 / 53824, the contents of which are incorporated herein by reference in their entirety. The scanning system 150 may also be provided in the form of the scanning system 200 shown in Figure 2, as in this exemplary embodiment. The scanning system 200 comprises an optical coupler 211, a first scanning element 212, a first curved mirror 213, a second scanning element 214, and a second curved mirror 215. The optical beam LS enters the scanning system 200 via the optical coupler 211. Next, the optical beam LS is sequentially reflected by the first scanning element 212, the first curved mirror 213, the second scanning element 214, and the second curved mirror 215 before being incident on the imaging target in the form of the eye 220. The optical LC scattered by the eye 220 and collected by the scanning system 200 passes through the scanning system 200 in the reverse order of the optical path of the optical beam LS and exits the scanning system 200 via the optical coupler 211. Alternatively, the scanning system 150 may be a lens-based system, and it should be noted that the scanning system 150 is arranged to perform two-dimensional point scanning by one or more scanning elements that scan the optical beam LS over the imaging target 105 through one or more lenses. Such lens-based scanning systems are well known to those skilled in the art and are therefore not described in further detail herein.

[0030] Two-dimensional point scanning is performed by rotating the first scanning element 212 around a first axis 216 to scan the optical beam LS in a first direction across the object to be imaged, and by rotating the second scanning element 214 around a second axis 217 to scan the optical beam LS in a second direction (which may be orthogonal to the first direction, as in this exemplary embodiment) across the object to be imaged. By rotating the first scanning element 212 and the second scanning element 214 in this way, the optical beam LS can be directed to any position on the object to be imaged. The rotation of the first scanning element 212 and the second scanning element 214 may be adjusted by the controller 140 or a separate controller (not shown) scanning system controller so that the optical beam LS is scanned across the object to be imaged according to a predetermined scanning pattern, as described above.

[0031] The first curved mirror 213 is an elliptical mirror (also called a slit mirror), and the second curved mirror 215 is also an elliptical mirror. Each elliptical mirror has two foci. The first scanning element 212 is located at the first focal point of the first curved mirror 213, and the second scanning element 214 is located at the second focal point of the first curved mirror 213. The second scanning element 214 is also located at the first focal point of the second curved mirror 215, and the eye 220 (more specifically, the pupil of the eye 220 in this embodiment) is located at the second focal point of the second curved mirror 215. However, either curved mirror may instead be any reflective element having an aspherical reflective surface, such as a conical cross-sectional shape like a paraboloid or hyperboloid, or more generally, a shape described by one or more polynomial functions of two variables.

[0032] The first scanning element 212 and the second scanning element 214 may each be a galvanometer optical scanner (or "galvo"), as in this exemplary embodiment, but other types of scanning elements, such as a MEMS scanning mirror or a resonant scanning mirror, may be used instead.

[0033] Referring again to Figure 1, the reference arm 122 comprises a reference arm optical fiber 125, an optical switch 126, and an optical coupler 127. The reference arm optical fiber 125 is positioned to guide the reference light LR (from the optical splitter 121 to the optical switch 126). The reference arm 122 may further include an output optical fiber 128 positioned to guide the reference light LR (via a second optical splitter 124) toward the photodetector 130, as in this exemplary embodiment.

[0034] The optical switch 126 is controllable (for example, by the controller 140, as in this exemplary embodiment) to direct the reference light LR from the reference arm optical fiber 125 to a selected optical path among N optical paths 129, where N is an integer greater than or equal to 2. Each of the N optical paths 129 has a different optical path length and / or chromatic dispersion than each of the other optical paths of the N. In other words, each of the N optical paths has either a different optical path length than each of the other optical paths of the N, a different chromatic dispersion than each of the other optical paths of the N, or a different combination of optical path length and chromatic dispersion than the combination of each of the other optical paths of the N. The optical switch 126 may be controllable by the controller 140, as in this exemplary embodiment, but may instead be controllable manually (i.e., by a user of the OCT imaging system 100 scanning a dial that operates to change the switch setting of the mechanical switch or the optical switch 126). The optical coupler 127 is positioned to guide the reference light LR propagating along the selected optical path to the output optical fiber 128.

[0035] The optical switch 126 may be a 1×N optical switch (i.e., a 1×N optical fiber switch) having N output ports optically coupled to each of the N optical paths described above, as in this exemplary embodiment, but alternatively, it may be a 1×M optical switch (where M is an integer greater than N) having these N output ports plus one or more additional output ports. For example, in some exemplary embodiments where M = N+1, the 1×M optical switch has one additional output port connected to an optical power monitor that is positioned to monitor the optical power of a reference optical fiber LR propagating through the reference arm optical fiber 125 when the 1×M optical switch is configured to direct light from the reference arm optical fiber 125 to the aforementioned additional output port. In other exemplary embodiments where M = N+P, the 1×M optical switch has P additional output ports (where P is an integer greater than or equal to 2), each of the P additional output ports being connected to each of the P optical power monitors, each optical power monitor being positioned to monitor the optical power of light incident thereon when the 1×M optical switch is configured to direct light from the reference arm optical fiber 125 to the aforementioned additional P output ports. By providing multiple optical power monitors, redundancy is provided (in case one of the optical power monitors fails or malfunctions), and the optical power of the reference optical LR propagating through the reference arm optical fiber 125 can be monitored with greater reliability.

[0036] As described above, if multiple optical power monitors 390 are provided, the optical switch 126 may be able to control the following: a first portion of the reference light LR from the reference arm optical fiber 125 to a selected optical path among the N optical paths 129 (so that only a portion of the reference light LR from the reference arm optical fiber 125 is led to the selected optical path), and a second portion of the reference light LR from the reference arm optical fiber 125 (the second portion may be the remaining portion of the reference light LR) to an optical power monitor 390, or simultaneously guide each portion of the reference light LR from the reference arm optical fiber 125 to its respective optical power monitor. Additionally or alternatively, the optical switch 126 may be able to control the following: guiding the reference light LR (or a portion thereof) from the reference arm optical fiber 125 to a selected optical path among the N optical paths 129, and guiding the reference light LR (or a portion thereof) from the reference arm optical fiber 125 to an optical power monitor 390.

[0037] The optical power monitor(s) may be any type of photoelectric device capable of generating an electrical signal indicating the optical power of the received optical signal, and may include, for example, Si, Ge, or InGaAs detectors. Furthermore, the form of the optical switch 126 is not limited, and the optical switch 126 may include, for example, a micro-electromechanical switch, a micro-mechanical switch, a micro-optical switch, and / or an optical switch driven by a stepper motor.

[0038] The optical coupler 127 may be an N×1 optical coupler having N input ports optically coupled to each of the N optical paths described above, as in this exemplary embodiment, or alternatively, an M×1 optical coupler (where M is an integer greater than N) having N input ports and one or more additional input ports. For example, the N×1 optical coupler may be either an N×1 optical fiber coupler or an N×1 optical switch (which can be controlled by the controller 140 or manually, as described above) for coupling one input port of the N input ports corresponding to one output port of the N output ports to which the reference optical LR is coupled by the optical switch 126 to the output optical fiber 128. The form of the optical coupler 127 is not limited, and the optical coupler 127 may include, for example, a micro-electromechanical switch, a micro-mechanical switch, a micro-optical switch, an optical switch driven by a stepper motor, or a passive T-coupler.

[0039] Each of the N optical paths 129 may comprise a separate optical fiber connecting each of the N output ports to each of the N input ports, as in this exemplary embodiment. At least some of the optical fibers may have different path lengths (by having different physical lengths and / or by being made of materials having different refractive indices), as in this exemplary embodiment. Thus, in this arrangement, the optical path of the reference optical LR propagating along the reference arm 122 can be modified by selecting a suitable optical fiber that connects one of the N output ports of the optical switch 126 to the corresponding one of the N input ports of the optical coupler 127. However, this modification of the path length in the reference arm 122 may also be achieved using free-space optical communication in some or all of the N optical paths 129, for example, by using a mirror (not shown) to increase the distance of light propagating along the path between the selected output port of the optical switch 126 and the corresponding input port of the optical coupler 127.

[0040] Each of the N optical paths 129 may comprise its own dispersive element, as in this exemplary embodiment. Each dispersive element is positioned to provide its respective level of chromatic dispersion of a reference light LR propagating through the optical path comprising the dispersive element. For example, each dispersive element may be a glass rod or optical fiber providing the desired level of chromatic dispersion and may be positioned between two portions (e.g., halves) of each optical fiber connecting each output port of the optical switch 126 to the corresponding input port of the optical coupler 127. Thus, each of the one or more optical paths can have its respective level of chromatic dispersion, set by comprising its respective dispersive element providing the desired level of chromatic distortion. However, instead of using dispersive elements, the level of chromatic dispersion of a reference light LR propagating through one of the N optical paths 129 may instead be provided by optical fibers connecting the corresponding output ports of the optical switch 126 to the respective input ports of the optical coupler 127 (for example, by selecting optical fibers having a predetermined level of chromatic dispersion, such as by selecting a particular type of fiber given the length of fiber required to achieve the desired optical path length).

[0041] Furthermore, in some exemplary embodiments, each of the N optical paths 129 may include its respective dispersing element without including an optical fiber, and the dispersing element is arranged to provide its respective level of chromatic dispersion of a reference optical LR propagating through the optical path containing the dispersing element. In such cases, changes in the optical path length may instead be achieved by the dispersing element itself and / or by free-space optical communication, as described above.

[0042] Therefore, as described above, by appropriately selecting optical fibers and / or dispersive elements in at least a portion of the N optical paths 129, each of the N optical paths can have a different optical path length and / or chromatic dispersion than each of the other optical paths of the N optical paths 129. That is, the optical path length of one of the N optical paths 129 may be set to a predetermined value by appropriately setting the optical path length of the optical fiber in the optical path while considering the optical path lengths of any other elements in the optical path (such as dispersive elements, if provided), and the level of chromatic dispersion of that optical path may be set to a predetermined level by appropriately setting the level of chromatic dispersion of selected dispersive elements in the optical path while considering the level of chromatic dispersion of each of the other elements in the optical path (including, if provided for the optical path, the level of chromatic dispersion of the optical fibers connecting each of the N output ports to each of the N input ports). This makes it possible to set a predetermined value of the optical path length and / or the level of chromatic dispersion of an optical path to be different from each of the other optical paths of the N optical paths 129.

[0043] The reference arm 122 may be provided in the form of the reference arm 300 schematically shown in Figure 3. The reference arm 300 comprises a reference arm optical fiber 310, a 1×5 optical switch 320, a 5×1 optical coupler 330, an output optical fiber 340, and five optical paths 350. The 1×5 optical switch 320 has five output ports PO1', PO2', PO3', PO4', and PO5', and the 5×1 optical coupler 330 has five input ports PI1', PI2', PI3', PI4', and PI5'. Each optical path of the optical path 350 is provided between the respective output port of the 1×5 optical switch 320 and the respective numbered input ports of the 5×1 optical coupler 330 (for example, the first optical path is provided at ports PO1 to PI1). The optical path 350 comprises (same type) optical fibers 361, 362, 363, 364, and 365, each coupling its output port to its corresponding input port. The third and fourth optical paths from left to right in Figure 3 each comprise dispersion elements 370 and 380, respectively, located between the two halves of optical fibers 363 and 364 provided in the third and fourth optical paths. The dispersion elements 370 and 380 provide different pre-selected levels of chromatic dispersion. Furthermore, as shown in Figure 3, optical fiber 361 is a first length, optical fibers 362 and 363 are different second lengths, and optical fibers 364 and 365 are a third length different from the first and second lengths. Thus, each of the five optical paths 350 has its own unique combination of optical path length and chromatic dispersion. The exemplary reference arm 300 in Figure 3 has five optical paths, but instead, fewer or more optical paths may be provided, each having a different optical path length and / or chromatic dispersion than each of the other optical paths.

[0044] The reference arm 122 may be provided in the form of the reference arm 301 schematically shown in Figure 4. The reference arm 301 in Figure 4 differs from the reference arm 300 in Figure 3 only by having a 1×6 optical switch 321 instead of a 1×5 optical switch 320, the additional output port P06 of the 1×6 optical switch 321 being optically coupled to a power monitor 390 via an optical fiber 366. The power monitor 390 can take any of the above forms (among other things). The power monitor 390 may be used, for example, to monitor the optical power of the reference optical LR propagating through the reference arm optical fiber 125, when the 1×6 optical switch 321 is configured to direct light from the reference arm optical fiber 125 to the additional output port P06', for the purpose of confirming that the measured power level corresponds to a safe level of illumination delivered to the patient's eye by the light source 110. The controller 140 can be configured to turn off the power to the light source 110 or, otherwise, stop the illumination of the patient's eyes by the light source 110 (for example, by closing a shutter) if the light power measured by the power monitor 390 exceeds a predetermined threshold level.

[0045] The above arrangement of the reference arm 122, which is switchable between N optical paths 129 having various optical path lengths and / or levels of wavelength dispersion, may be advantageous in that the OCT imaging system 100 can be switched between different optical configurations, allowing the OCT imaging system 100 to operate in multiple imaging modes, whereas previously each configuration required a dedicated OCT imaging system within a single OCT imaging system or a time-consuming configuration change. The OCT imaging system 100 may be able to operate in multiple imaging modes to image each different depth range of the imaging target 105 along the propagation direction of the sample light LS toward the imaging target 105, as in this exemplary embodiment. For example, if the imaging target 105 is an eye, each depth range may correspond to each layer of the eye whose thickness direction is aligned with the optical axis of the eye.

[0046] During the operation of the OCT imaging system 100 in each imaging mode, the controller 140 can control the optical switch 126 to direct the reference light LR from the reference arm optical fiber 125 into each of the N optical paths, each having its own optical path length, such that the absolute value of the difference between the phase of the sample light LC, which has been scattered from a depth within each depth range of the imaging target 105 and received by the photodetector 130, and the phase of the reference light LR, which has been propagated through the output optical fiber 128 and received by the photodetector 130, is less than a predetermined threshold. In other words, each of the N optical paths has an optical path length such that, for each depth range of the imaging target 105 imaged in each imaging mode, the absolute value of the difference in optical path length between the optical path length of the sample arm 121 (including the optical path to and within the imaging target 105) and the optical path length of the reference arm 122 is less than a predetermined threshold. The predetermined threshold may be, for example, a predetermined ratio of the coherence length of the light generated by the light source 110 (i.e., the light beam LB), or it may be the coherence length of the light generated by the light source 110 itself. Therefore, the OCT imaging system 100 may be able to image a range of different depths of the object to be imaged 105 by switching N optical paths in order to keep the optical path difference between the arms of the interferometer 120 within the coherence length of the light generated by the light source 110.

[0047] Furthermore, by using dispersive elements in one or more of the optical paths, the OCT imaging system 100 can be configured to operate in multiple imaging modes, in one or more of the imaging modes, where the level of chromatic dispersion between the arms of the interferometer 120 is mismatched, for example, in full-range OCT imaging mode. High dispersion in the reference arm of the interferometer 120 helps to correct the phase of the reference beam and match it to the phase of the backscattered light from the object being imaged 105. Alternatively, high dispersion can be incorporated into the sample arm 121. For example, in distributed-coded full-range OCT (DE-FR-OCT), the phase of the signal is encoded by dispersive elements in the imaging system. The algorithm used in DE-FR-OCT assumes an initial phase and iteratively updates the estimated phase based on the recorded intensity and phase of the detected OCT signal. As the estimated phase converges, the original signal is restored (based on a given criterion), while the mirror image is degraded and can be removed to obtain depth information. In one or more other imaging modes for imaging a more limited depth range of the object to be imaged 105, the wavelength dispersion between the arms of the interferometer 120 can be matched.

[0048] The imaging target 105 may be a human eye, as in this exemplary embodiment, and the OCT imaging system 100 may be capable of operating in a first imaging mode for imaging at least a portion of the anterior segment of the eye, a second imaging mode for imaging at least a portion of the posterior segment of the eye, and / or a third imaging mode for imaging at least a portion of the anterior segment and at least a portion of the posterior segment of the eye (simultaneously). However, although the OCT imaging system 100 is described herein as an ophthalmic OCT imaging system, the imaging target 105 is not limited in this way and may instead be any tissue (e.g., skin), a biological specimen, or, more generally, any scattering medium whose subsurface structure is imaged by OCT. In such cases, the imaging modes may correspond to portions of the imaging target at different depth ranges or to the use of full-range OCT techniques for imaging over increased imaging depths.

[0049] When the OCT imaging system 100 is capable of operating in a first imaging mode, the controller 140 may be configured to control an optical switch 126 to guide the reference light LR from the reference arm optical fiber 125 to a first optical path among N optical paths, the first optical path comprising a first dispersion element configured such that the level of chromatic dispersion of the sample light LC, after being scattered by the anterior segment of the eye and then received by the photodetector 130, matches the level of chromatic dispersion of the reference light LR, after propagating through the output optical fiber 128 and then received by the photodetector 130. Thus, in the first imaging mode, the optical path selected by the controller 140 results in an optical path difference between the sample arm 121 and the reference arm 122, which is smaller than the coherence length of the light produced by the light source 110 for each range of depths imaged in the anterior segment of the eye, and the level of chromatic dispersion in the sample arm 121 (without considering any chromatic dispersion induced by the eye) matches that in the reference arm 122. By matching the wavelength dispersion between the arms of the interferometer 120 in the first imaging mode, the OCT imaging system 100 can image the anterior segment (or a portion thereof) of the eye without full-range OCT technology, thereby reducing computational costs and improving imaging quality by allowing better control of image artifacts caused by autocorrelation from the OCT imaging system 100. In this regard, algorithms used in full-range OCT tend to degrade the SNR because they can introduce artifacts that need to be suppressed. In this exemplary embodiment, by providing wavelength dispersion matching between the arms of the interferometer 120, the posterior segment of the eye can be imaged and / or the anterior segment can be imaged sequentially without using the algorithms described above.

[0050] The OCT imaging system 100 may further include, as in this exemplary embodiment, a lens 160 for changing the focus setting for imaging the anterior and posterior segments of the eye, and a lens movement mechanism 170 for moving the lens 160 in and out of the optical path within the sample arm 121 of the interferometer 120. In such a case, the controller 140 may control the lens movement mechanism 170 to move the lens 160 into the optical path within the sample arm 121 of the interferometer 120 so that the anterior segment (or a portion thereof) of the eye is imaged through the lens 160 during operation of the OCT imaging system 100 in the first imaging mode. Furthermore, the lens movement mechanism 170 may be configured to adjust the position of the lens 160 to change the focus of the lens 160. In such a case, the controller 140 may control the lens movement mechanism 170 to optimize the focus of the OCT imaging system 100 when operating in the first imaging mode. Providing the lens 160 helps ensure that the anterior segment of the eye is imaged by the OCT imaging system 100 in the first imaging mode.

[0051] If the OCT imaging system 100 is capable of operating in a second imaging mode, the controller 140 may be further configured to control an optical switch 126 to guide the reference light LR from the reference arm optical fiber 125 to a second optical path among N optical paths, as in this exemplary embodiment, the second optical path comprising a second dispersion element configured such that the level of chromatic dispersion of the sample light LC, after being scattered by the posterior segment of the eye and then received by the photodetector 130, matches the level of chromatic dispersion of the reference light LR, after being propagated through the output optical fiber 128 and then received by the photodetector 130. Thus, in the second imaging mode, the optical path selected by the controller 140 results in an optical path difference between the sample arm 121 and the reference arm 122, which is smaller than the coherence length of the light produced by the light source 110 for each range of depths imaged in the posterior segment of the eye, and the level of chromatic dispersion in the sample arm 121 (without considering any chromatic dispersion induced by the eye) matches that in the reference arm 122. By matching the wavelength dispersion between the arms of the interferometer 120 in the second imaging mode, the OCT imaging system 100 is configured to image the posterior segment (or a portion thereof) of the eye without full-range OCT technology. This allows for better control of image artifacts caused by autocorrelation from the OCT imaging system 100, as described above, thereby reducing computational costs and improving imaging quality.

[0052] As in this exemplary embodiment, the controller 140 can further position the lens movement mechanism 170 to move the lens 160 out of the optical path within the sample arm 121 of the interferometer 120, so that the posterior segment (or a portion thereof) of the eye is imaged without using the lens 160 during operation of the OCT imaging system 100 in a second imaging mode. Thus, the OCT imaging system 100 can perform imaging with the lens 160 in a first imaging mode and without using the lens 160 in a second imaging mode. Consequently, the anterior segment of the eye can be imaged in the first imaging mode by the OCT imaging system 100 using the lens 160 without interfering with the OCT imaging system 100's ability to image the posterior segment of the eye, where the use of the lens 160 is not required.

[0053] If the OCT imaging system 100 is capable of operating in a third imaging mode, the controller 140 may be further configured to control an optical switch 126 to guide the reference light LR from the reference arm optical fiber 125 to a third optical path among N optical paths, as in this exemplary embodiment, the third optical path provides a level of chromatic dispersion of the reference light LR propagated through the output optical fiber 128 and received by the photodetector 130 that is greater than the level of chromatic dispersion of the sample light LC received by the photodetector 130 after being scattered by the anterior and / or posterior segments of the eye. Thus, in the third imaging mode, the optical path selected by the controller 140 results in an optical path difference between the sample arm 121 and the reference arm 122 that is smaller than the coherence length of the light produced by the light source 110 for each range of depth imaged over the anterior segment (or part thereof) and posterior segment (or part thereof) of the eye, and the level of chromatic dispersion in the reference arm 122 is greater than that in the sample arm 121 (without considering any chromatic dispersion induced by the object being imaged 105). By mismatching the wavelength dispersion between the arms of the interferometer 120 in the third imaging mode, the OCT imaging system 100 can image the anterior and posterior segments (or a part thereof) of the eye using full-range OCT technology, as described above.

[0054] Although three imaging modes have been described above, the OCT imaging system 100 is not limited in this respect, and more generally, the switchable functionality of the OCT imaging system 100 can be used to switch between various optical paths arranged to provide the required level of optical path length and / or chromatic dispersion for any particular set of system requirements, depending on the imaging depth, the OCT technology used, or other methods. For example, the OCT imaging system 100 may additionally or alternatively include a fourth imaging mode which is the same as the first imaging mode except that it includes a fourth dispersion element (instead of the first dispersion element) positioned to provide a level of chromatic dispersion within the reference arm 122 as described in the third imaging mode; a fifth imaging mode which is the same as the second imaging mode except that it includes a fifth dispersion element (instead of the second dispersion element) positioned to provide a level of chromatic dispersion within the reference arm 122 as described in the third imaging mode; or a sixth imaging mode which is the same as the third imaging mode except that it includes a sixth dispersion element (instead of the third dispersion element) positioned to provide a level of chromatic dispersion within the reference arm 122 as described in the first or second imaging mode. Thus, in the fourth and fifth imaging modes, full-range OCT techniques can be used in the same way as in the third imaging mode, which may be desirable to capture increased imaging depth within each part of the eye. Furthermore, in the sixth imaging mode, at least a portion of the anterior and posterior segments of the eye can be imaged without full-range OCT technology. For example, the range of depths imaged across the anterior and posterior segments of the eye can be achieved without requiring the increased range of imaging depths obtained with full-range OCT technology.

[0055] Referring again to Figure 1, the photodetector 130 is positioned to detect interference light LI resulting from the interference between the reference light LR propagating through the output optical fiber 128 and the sample light LC, which is scattered by the object to be imaged 105 and propagates through the sample arm 121. In other words, during imaging of the object to be imaged 105, the reference light LR and the collected light LC are induced to interfere with each other in the optical splitter 122, and the resulting interference light LI is directed to the photodetector 130 and received by the photodetector. The photodetector 130 is positioned to generate a detection signal based on the measured interference, which can be processed by the controller 140 or separate OCT data processing hardware to generate an image of the object to be imaged 105 using well-known OCT data processing techniques. For example, the controller 140 can generate composite volumetric OCT data, which can be used to generate a front image of the object to be imaged 105, which limits the SVP to a selected slab of the imaged sample by well-known projection techniques such as total voxel projection (SVP) or restricted SVP (RSVP).

[0056] The photodetector 130 generates a detection signal by photoelectrically converting the interference measured between the reference light LR and the sample light LC, which is scattered by the imaging target 105 and propagates through the sample arm 121. The specific form that the photodetector 130 can take depends on the form in which the OCT imaging system 100 is implemented. For example, if the OCT imaging system 100 is implemented as an SD-OCT imaging system, the photodetector 130 may include a spectrometer that may have a diffraction grating, a Fourier transform lens, and a detector array (or line scanning camera). If the OCT imaging system 100 is implemented as an SS-OCT imaging system as in this exemplary embodiment, the photodetector 130 may include a balanced photodetector configuration with two photodetectors (e.g., reverse-bias photodiodes) whose output photocurrents are subtracted from each other, and the subtracted current signals are converted into a voltage detection signal by a transimpedance amplifier.

[0057] The OCT imaging system 100 may further include a pupil alignment module 180, which is positioned using well-known techniques to align the focus of the OCT imaging system 100 with the pupil of the eye based on an image of the anterior segment, as in this exemplary embodiment. The OCT imaging system 100 may operate in a first imaging mode while the pupil alignment module 180 is operating to align the focus of the OCT imaging system 100 with the pupil of the eye, and then, after the operation of the pupil alignment module 180, be positioned in a second imaging mode (or third imaging mode) to align the focus of the OCT imaging system 100 with the pupil of the eye. Thus, after the pupil alignment module 180 has aligned the focus of the OCT imaging system 100 with the pupil of the eye, the controller 140 is configured to control the optical switch 126 to switch from guiding the reference light LR from the reference arm optical fiber 125 to a first optical path to guiding the reference light LR from the reference arm optical fiber 125 to a second optical path.

[0058] The ability of the OCT imaging system 100 to switch between different imaging modes may allow the OCT imaging system to acquire OCT images of interest, which can significantly improve the OCT imaging workflow, by advantageously using images from the anterior segment of the eye for patient alignment before rapidly switching to the second (or third) imaging mode described above. The workflow time for patient alignment can be further reduced by not using lens 160 while imaging in the first imaging mode during patient alignment, since images acquired without using lens 160 may be sufficient for the purpose of patient alignment.

[0059] The controller 140 may be provided in any suitable form, for example, as programmable signal processing hardware 400 of the type schematically shown in Figure 5. The programmable signal processing device 400 includes a communication interface (I / F) 410 for use in receiving commands regarding the imaging mode on which the OCT imaging system 100 should operate and outputting signals to the optical switch 126 (and optionally, an N×1 optical switch as an optical coupler 127), or for receiving detection signals from the photodetector 130 and outputting an image of the object to be imaged 105 (for example, in a front projection) for display on a display such as a computer screen. The signal processing hardware 400 further includes a processor (e.g., a central processing unit, i.e., a CPU, and / or a graphics processing unit, i.e., a GPU) 420, working memory 430 (e.g., random access memory), and an instruction store 440 that stores a computer program 445 containing computer-readable instructions that, when executed by the processor 420, cause the processor 420 to perform various functions, including the functions of the controller 140 described herein. The working memory 430 stores information used by the processor 420 during the execution of the computer program 445. The instruction store 440 may include a ROM (for example, in the form of electrically erasable programmable read-only memory (EEPROM) or flash memory) preloaded with computer-readable instructions. Alternatively, the instruction store 440 may include RAM or a similar type of memory, and the computer-readable instructions of the computer program 445 can be input from a computer program product such as a non-temporary computer-readable storage medium 450 in the form of a CD-ROM, DVD-ROM, or computer-readable signals 460 that carry computer-readable instructions. In either case, when the computer program 445 is executed by the processor 420, it causes the processor 420 to perform the functions of the controller 140 described herein.In other words, the controller 140 of this exemplary embodiment may include a computer processor 420 and a memory 440 that stores computer-readable instructions that, when executed by the computer processor 420, cause the computer processor 420 to control an optical switch 126 to guide the reference light LR from the reference arm optical fiber 125 to a selected optical path among N optical paths, and optionally control N×1 optical switches simultaneously with the optical switch 126 as described above. Furthermore, when the computer-readable instructions are executed by the computer processor 420, the computer processor 420 can process the detection signal to generate an image of the target to be captured 105.

[0060] However, it should be noted that the controller 140 may alternatively be implemented as non-programmable hardware such as an ASIC, FPGA, or other dedicated integrated circuit that performs the functions of the controller 140 described above, or as a combination of such non-programmable and programmable hardware as described above, with reference to Figure 5.

[0061] Figure 6 is a flowchart showing the process by which the controller 140 of this exemplary embodiment controls the imaging of the target object 105 by the OCT imaging system 100.

[0062] In step S1 of Figure 6, the controller 140 receives a signal indicating the range of imaging depths in which an image of a portion of the target 105 is acquired. The received signal can indicate an imaging depth range corresponding to the first imaging mode, the second imaging mode, or the third imaging mode, as described above, as in this exemplary embodiment.

[0063] In step S2 of Figure 6, the controller 140 configures the OCT imaging system 100 to acquire an image of a portion of the object to be imaged 105 over an indicated imaging depth range. To do this, the controller 140 selects one of the N optical paths based on the received signal and controls the optical switch 126 to guide the reference light LR from the reference arm optical fiber 125 to the selected optical path. If the optical coupler 127 is provided in the form of an N×1 optical switch, as described above, the controller 140 may also control the N×1 optical switch to switch simultaneously with the optical switch 126 to connect the selected output port of the optical switch 126 to the corresponding input port of the N×1 optical switch. For example, if the received signal indicates an imaging depth range corresponding to a first imaging mode, the controller 140 selects an optical path corresponding to the optical path length and / or chromatic dispersion required for the first imaging mode.

[0064] In step S3 of Figure 6, the controller 140 controls the OCT imaging system 100 to acquire an image of a portion of the target object 105. This is achieved by operating the OCT imaging system 100, which is configured using techniques well known to those skilled in the art. For example, as in this exemplary embodiment, the controller 140 can control the OCT imaging system 100, which is configured to acquire an image of a portion of the target object 105 by operating the pupil alignment module 180, operating the movement module 170, controlling the scanning system 105 to perform a two-dimensional point scan of the target object 105 over a range of indicated imaging depths, receiving a detection signal from the photodetector 130, and generating an image of the portion of the target object 105 based on the detection signal.

[0065] The process in Figure 6 can be implemented by a controller 140, implemented in the form of the programmable signal processing hardware 400 described above with reference to Figure 5, which operates according to the instructions contained in the computer program 445 when the computer program 445 is executed by the processor 420. The computer program 445 may be stored in a non-temporary computer-readable storage medium such as a CD-ROM or DVD-ROM, or in a computer program product 450 such as a computer-readable signal 460 that carries computer-readable instructions.

[0066] (Second exemplary embodiment) Figure 7 is a schematic diagram of an OCT imaging system 500 for imaging an object 105 according to a second exemplary embodiment. The OCT imaging system 500 comprises a light source 110, an interferometer 520, a controller 540, and a photodetector 130, and may further comprise a lens 160, a lens movement mechanism 170, and a pupil alignment module 180, as in this exemplary embodiment. The OCT imaging system 500 may also be a point-scanning SS-OCT imaging system further comprising a scanning system 150, as in this exemplary embodiment. However, the OCT imaging system 500 may more generally be any OCT imaging system known in the art, such as any FD-OCT imaging system.

[0067] The light source 110, the sample arm 121 of the interferometer 520, the photodetector 130, the lens 160, the lens movement mechanism 170, and the pupil alignment module 180 are the same as in the first exemplary embodiment. Therefore, these components, and other components of the OCT imaging system 500 labeled with the same reference numerals as in the first exemplary embodiment of Figure 1, will not be described again. This exemplary embodiment differs from the first exemplary embodiment of Figure 1 in at least some configurations of the components of the interferometer 520 (particularly in the reference arm 522 of the interferometer 520), the differences of which will be described below with reference to Figure 7. Furthermore, the controller 540 differs from the controller 140 only in its control of the reference arm 522.

[0068] The interferometer 520 differs from the interferometer 120 of the first exemplary embodiment only in the configuration of the reference arm 522, and in that it includes an optical splitter 523 instead of both the optical splitter 123 and optical splitter 124 of the first exemplary embodiment. The optical splitter 523 splits the light LB from the light source 110 into a sample light LS propagating along the sample arm 121 and a reference light LR propagating along the reference arm 522, and is arranged to combine the collected light LC from the sample arm 121 and the reference light LR emitted from the reference arm 522 to form an inference light LI resulting from the interference between the reference light LR and the collected light LC.

[0069] The reference arm 522 comprises a first mirror 524, a second mirror 526, and a mirror moving mechanism 528. The first mirror 524 is positioned so that when the reference light LR from the optical splitter 523 is incident on the first mirror 524, it reflects the reference light LR from the optical splitter 523 and returns it to the optical splitter 523.

[0070] The mirror moving mechanism 528 is controllable by the controller 540 to move the second mirror 526 in and out of the optical path of the reference light LR propagating toward the first mirror 524, such that when the second mirror 526 is moved out of the optical path, the reference light LR is reflected back toward the optical splitter 523 by the first mirror 524, and when the second mirror 526 is moved in the optical path, the reference light LR is reflected back toward the optical splitter 523 by the second mirror 526 instead of the first mirror 524. In other words, the controller 540 controls the mirror moving mechanism 528 to move the second mirror 526 to a position in front of the first mirror 524 and within the optical path of the reference light LR propagating toward the first mirror 524, and from that position, such that when the second mirror 526 is in the position of the first mirror 524, the second mirror 526 reflects the reference light LR back toward the optical splitter 523 instead of the first mirror 524. The mirror movement mechanism 528 may rotate the second mirror 526 in and out of the optical path of the reference light LR propagating toward the first mirror 524 (for example, around a rotation axis parallel to the optical path to reduce or eliminate the movement of the second mirror 526 in the direction along the optical path), as in this exemplary embodiment. Alternatively, the mirror movement mechanism 528 may translate the second mirror 526 in and out of the aforementioned optical path (for example, in a direction perpendicular to the optical path to reduce or eliminate the movement of the second mirror 526 in the direction along the optical path). With either of these arrangements, the optical path length of the reference arm 522 can be switched between two values ​​by a controller 540, which can be selected as needed for a particular OCT imaging system configuration. Compared to the above-described conventional mechanical mechanisms that change the optical path length of the reference arm by moving a mirror provided at the end of the reference arm along the optical path of the reference light using a linear actuator or the like, this arrangement can enable large changes in optical path length relatively quickly by shortening the distance required for the mirror in the reference arm to move to produce the desired change in optical path length.

[0071] The OCT imaging system 500 may operate in a first imaging mode, as in this exemplary embodiment, for imaging a first depth range of the imaging target 105 along the propagation direction of the sample light LS toward the imaging target 105, and in a second imaging mode, for imaging a second depth range of the imaging target 105 along the propagation direction of the sample light LS toward the imaging target 105. The first depth range and the second depth range are different, but the two ranges may partially overlap in some cases. For example, in this exemplary embodiment, where the imaging target 105 is an eye, the depth range is the depth range along the optical axis of the eye. Furthermore, in such a case, the OCT imaging system 500 may operate in a first imaging mode, for imaging a portion of the anterior segment of the eye as the first depth range of the imaging target 105, and in a second imaging mode, for imaging a portion of the posterior segment of the eye as the second depth range of the imaging target 105.

[0072] The controller 540 may be configured to control the mirror movement mechanism 528 such that, during the operation of the OCT imaging system 500 in the first imaging mode, the second mirror 526 is outside the optical path such that the phase difference between the sample light LC, which has been scattered from a first depth range of the object to be imaged 105 and received by the photodetector 130, and the reference light LR, which has been reflected back toward the optical splitter 523 by the first mirror 524 and received by the photodetector, is smaller than a predetermined threshold. In other words, the reference arm 522 has an optical path length such that, when the second mirror 526 is moved outside the optical path of the reference light LR, the difference in optical path length between the optical path length of the sample arm 121 and the optical path length of the reference arm 522 is less than a predetermined threshold over the first depth range of the object to be imaged 105 being imaged in the first imaging mode.

[0073] The controller 540 may be further configured to control the mirror moving mechanism 528 such that, during the operation of the OCT imaging system 500 in the second imaging mode, the second mirror 526 is in the optical path such that the phase difference between the sample light LC, which has been scattered from a second depth range of the object to be imaged and received by the photodetector 130, and the reference light LR, which has been reflected back toward the optical splitter 523 by the second mirror 526 and received by the photodetector, is smaller than a predetermined threshold. In other words, the reference arm 522 has an optical path length such that, when the second mirror 526 moves into the optical path of the reference light LR, the difference in optical path length between the optical path length of the sample arm 121 and the optical path length of the reference arm 522 is less than a predetermined threshold over a second depth range of the object to be imaged 105 being imaged in the second imaging mode.

[0074] The predetermined threshold may be, for example, a predetermined ratio of the coherence length of the light generated by the light source 110, or it may be the coherence length of the light generated by the light source 110 itself. Therefore, the OCT imaging system 100 can switch between imaging two depth ranges of the object to be imaged 105 by switching the second mirror 526 inside or outside the optical path of the reference light LR propagating toward the first mirror 524. This switch makes the difference in optical path length between the arms of the interferometer 120 shorter than the coherence length of the light for each depth range, as needed.

[0075] A second exemplary embodiment is described using two mirrors within a reference arm 522, but the OCT imaging system 500 is not limited in this respect and can generate other different optical path lengths within the reference arm 522 using additional mirrors that are movable by a mirror moving mechanism 528 (or by a separate moving mechanism similarly controllable by the controller 540). Thus, the OCT system 500 can quickly switch between operating in various imaging modes that enable imaging of the object to be imaged 105 over a range of different depths.

[0076] While the first and second exemplary embodiments were described with reference to a point-scanning SS-OCT system, the OCT imaging system is not so limited. For example, any of the described OCT imaging systems may be point-scanning, line-scanning, or full-field OCT systems. In the case of a line-scanning system, the light source 110 is replaced by a line source arranged to generate a line of light, and the scanning system 150 is arranged to perform scanning of the line of light across the object to be imaged 105. In the case of a full-field system, the light source 110 generates a light beam, and the scanning system 150 may be replaced by a transport optics system arranged to guide the light beam to the object to be imaged 105 and collect scattered light during imaging of the object to be imaged 105. Furthermore, any of the OCT imaging systems described above can be provided as an alternative to an SD-OCT system by using an appropriate arrangement of the light source 110 and the photodetector 130 as described above. Furthermore, any of the OCT imaging systems described above may be provided as an alternative to a TD-OCT imaging system. For example, in the first exemplary embodiment, as described above, the second optical splitter 124 can be omitted for the mirror, and the second mirror can be moved (translationally) by a further moving mechanism (controllable by the controller 140) to acquire image data using the OCT imaging system 100 at different depths within the object to be imaged 105 in the manner of TD-OCT imaging systems well known to those skilled in the art. The first mirror 524 and the second movable mirror 526 may also be moved (translationally) if the OCT imaging system 500 of the second exemplary embodiment is adapted to form a TD-OCT imaging system.

[0077] In the foregoing description, exemplary embodiments are described with reference to several exemplary embodiments. Therefore, this specification should be considered illustrative rather than restrictive. Similarly, the drawings illustrating the features and advantages of the exemplary embodiments are presented for illustrative purposes only. The architecture of these exemplary embodiments is sufficiently flexible and configurable and can be utilized in ways other than those shown in the accompanying drawings.

[0078] Some aspects of the examples presented herein, such as the functions of a controller, may be provided in one exemplary embodiment as computer programs or software, such as one or more programs having instructions or sets of instructions contained in or stored in a manufactured product such as a machine-accessible or machine-readable medium, instruction store, or computer-readable storage device, each of which may be non-temporary. Programs or instructions on a non-temporary machine-accessible medium, machine-readable medium, instruction store, or computer-readable storage device may be used to program a computer system or other electronic device. Machine or computer-readable medium, instruction store, and storage device may include, but are not limited to, floppy diskettes, optical disks, and magneto-optical disks, or other types of medium / machine-readable medium / instruction store / storage device suitable for storing or transmitting electronic instructions. The techniques described herein are not limited to any particular software configuration. They may find applicability in any computing or processing environment. As used herein, the terms “computer-readable,” “machine-accessible medium,” “machine-readable media,” “instruction store,” and “computer-readable storage device” include any medium capable of storing, encoding, or transmitting instructions or sets of instructions for execution by a machine, computer, or computer processor, causing a machine / computer / computer processor to perform any one of the methods described herein. Furthermore, in the art, it is common to speak of software in one or another form (e.g., a program, procedure, process, application, module, unit, logic, etc.) that takes action or produces a result. Such expressions are merely a simple way of stating that the execution of software by a processing system causes a processor to perform an action to produce a result.

[0079] Some or all of the controller's functions may also be implemented by preparing application-specific integrated circuits, field-programmable gate arrays, or by interconnecting a suitable network of conventional component circuits.

[0080] Computer program products can be provided in the form of one or more storage media, one or more instruction stores, or one or more storage devices that store instructions that can be used to control or cause a computer or computer processor to perform any of the procedures of the exemplary embodiments described herein. The storage media / instruction stores / storage devices may include, but are not limited to, optical discs, ROMs, RAMs, EPROMs, EEPROMs, DRAMs, VRAMs, flash memory, flash cards, magnetic cards, optical cards, nanosystems, molecular memory integrated circuits, RAIDs, remote data storage devices / archives / warehouses, and / or any other types of devices suitable for storing instructions and / or data.

[0081] Stored in one or more computer-readable media, one or more instruction stores, or one or more storage devices, some implementations include software for controlling both the system hardware and enabling the system or microprocessor to interact with a human user or other mechanism using the results of the exemplary embodiments described herein. Such software may include, but is not limited to, device drivers, operating systems, and user applications. Finally, such computer-readable media or storage device further includes software for carrying out exemplary embodiments of the invention, as described above.

[0082] The system programming and / or software includes software modules for implementing the procedures described herein. In some exemplary embodiments herein, the modules include software, while in other exemplary embodiments herein, the modules include hardware, or a combination of hardware and software.

[0083] While various exemplary embodiments of the present invention have been described above, it should be understood that these are presented as examples and not as limitations. It will be apparent to those skilled in the art that various modifications of form and detail are possible. Therefore, the present invention should not be limited by any of the exemplary embodiments described above, but should be defined solely in accordance with the following claims and their equivalents.

[0084] Furthermore, the purpose of the abstract is to enable the Patent Office and the general public, particularly scientists, engineers, and practitioners unfamiliar with patent or legal terminology or expression, to quickly determine the nature and essence of the technical disclosure of this application from a rough examination. The abstract is not intended to limit the scope of the exemplary embodiments presented herein. It should also be understood that the procedures described in the claims do not need to be performed in the order presented.

[0085] While this specification includes details of many specific embodiments, these should not be construed as limitations on the scope of any invention or claim, but rather as descriptions of features specific to the particular embodiments described herein. Certain features described herein in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented separately or in any suitable partial combination in multiple embodiments. Furthermore, features described above as acting in a particular combination may be initially claimed as such, but one or more features from a claimed combination may, in some cases, be removed from the combination, and the claimed combination may cover a partial combination or a variation of a partial combination.

[0086] In certain situations, multitasking and parallel processing may be advantageous. Furthermore, the separation of various components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged in multiple software products.

[0087] While several exemplary embodiments and configurations have been described herein, it is clear that these are illustrative, not limiting, and are presented as examples only. In particular, many of the examples presented herein involve specific combinations of apparatus or software elements, but these elements may be combined in other ways to achieve the same purpose. Any operation, element, or feature discussed in relation to one embodiment is not intended to be excluded from a similar role in other embodiments or configurations.

Claims

1. An optical coherence tomography (OCT) imaging system for imaging an object to be imaged, wherein the OCT imaging system is Light source and A sample arm and a reference arm, wherein the reference arm is A reference arm optical fiber positioned to guide the reference light, An optical switch controllable to guide at least a portion of the reference light from the reference arm optical fiber to a selected optical path among N optical paths, where N is an integer of 2 or more, and each of the N optical paths has at least one of the optical path length or chromatic dispersion that is different from at least one of the optical path lengths or chromatic dispersions of each of the other optical paths among the N optical paths, An optical coupler arranged to guide at least a portion of the reference light propagating along the selected optical path to an output optical fiber, An interferometer comprising a reference arm having a light source and an optical splitter positioned to split light from the light source into sample light propagating along the sample arm and reference light propagating along the reference arm, The system comprises a photodetector arranged to detect interference light resulting from the interference between at least a portion of the reference light propagating through the output optical fiber and the sample light that propagates through the sample arm after being scattered by the imaging target, The optical switch is a 1×N optical switch having N output ports, the optical coupler is an N×1 optical coupler having N input ports, and each of the N optical paths has an optical fiber connecting each of the N output ports to each of the N input ports. Each of the N optical paths, one or more of which include a dispersion element in the optical fiber, and each of the dispersion elements is arranged to provide a respective level of wavelength dispersion of the reference light propagating through the optical path containing the dispersion element. The OCT imaging system further includes a controller, The OCT imaging system is capable of operating in multiple imaging modes to image different depth ranges of the object along the propagation direction of the sample light toward the object, During the operation of the OCT imaging system in each of the imaging modes, the controller is configured to control the optical switch to guide the reference light from the reference arm optical fiber to each of the N optical paths, each having an optical path length such that the phase difference between the sample light, which is scattered from a depth within the respective depth range of the imaging target and then received by the photodetector, and the reference light, which is propagated through the output optical fiber and then received by the photodetector, is less than a predetermined threshold. The object to be imaged is the eye, and the OCT imaging system is A first imaging mode for imaging a first portion of the anterior segment of the eye, A second imaging mode for imaging the first portion of the posterior segment of the eye, A third imaging mode for imaging the second portion of the anterior eye and the second portion of the posterior eye. It is possible to operate with at least one of the following: When the OCT imaging system is capable of operating in the first imaging mode, the controller is configured to control the optical switch to direct the reference light from the reference arm optical fiber to a first optical path among the N optical paths, the first optical path comprising a first dispersion element configured such that the level of wavelength dispersion of the sample light, after being scattered by a first portion of the anterior portion of the eye and then received by the photodetector, matches the level of wavelength dispersion of the reference light, after it has propagated through the output optical fiber and then received by the photodetector. When the OCT imaging system is capable of operating in the second imaging mode, the controller is configured to control the optical switch to direct the reference light from the reference arm optical fiber to a second optical path among the N optical paths, the second optical path comprising a second dispersion element configured such that the level of wavelength dispersion of the sample light, after being scattered by the first portion of the posterior portion of the eye and then received by the photodetector, matches the level of wavelength dispersion of the reference light, after it has propagated through the output optical fiber and then received by the photodetector. When the OCT imaging system is capable of operating in the third imaging mode, the controller is configured to control the optical switch to direct the reference light from the reference arm optical fiber to a third optical path among the N optical paths, the third optical path providing a level of wavelength dispersion of the reference light that is received by the photodetector after propagating through the output optical fiber, the level being greater than the level of wavelength dispersion of the sample light that is received by the photodetector after being scattered by the second portion of the anterior portion and / or the second portion of the posterior portion of the eye. The OCT imaging system further comprises a pupil alignment module configured to align the focus of the OCT imaging system with the pupil of the eye based on the image of the anterior segment of the eye. The OCT imaging system is configured to operate in a first imaging mode during the operation of the pupil alignment module to align the focus of the OCT imaging system with the pupil of the eye, and to operate in a second imaging mode after the operation of the pupil alignment module to align the focus of the OCT imaging system with the pupil of the eye.

2. The OCT imaging system according to claim 1, wherein at least a portion of the optical fibers have different optical path lengths.

3. The aforementioned N×1 optical coupler is N x 1 optical fiber coupler, An N×1 optical switch that can control the connection of one input port among the N input ports corresponding to one output port among the N output ports to which the reference light is coupled by the 1×N optical switch to the output optical fiber, An OCT imaging system according to claim 1 or claim 2, comprising one of the above.

4. The interferometer further comprises a lens and a lens moving mechanism for moving the lens in and out of the optical path within the sample arm of the interferometer, In the first imaging mode, the controller is configured to control the lens movement mechanism so that, during the operation of the OCT imaging system in the first imaging mode, the first portion of the anterior eye of the eye is imaged through the lens, and the lens movement mechanism moves the lens into the optical path within the sample arm of the interferometer. The OCT imaging system according to claim 1, wherein in the second imaging mode, the controller is further configured to control the lens moving mechanism to move the lens out of the optical path in the sample arm of the interferometer so that the first portion of the posterior eye of the eye is imaged without using the lens during operation of the OCT imaging system in the second imaging mode.

5. Further comprising an optical power monitor, wherein the optical switch is The first portion of the reference light from the reference arm optical fiber is simultaneously directed to the selected optical path among the N optical paths, and the second portion of the reference light from the reference arm optical fiber is simultaneously directed to the optical power monitor, and / or The OCT imaging system according to claim 1 or 2, which is controllable to switch between guiding at least a portion of the reference light from the reference arm optical fiber to the selected optical path of the N optical paths, and guiding at least a portion of the reference light from the reference arm optical fiber to the optical power monitor.

6. A computer implementation method for controlling imaging of an object to be imaged by an optical coherence tomography (OCT) imaging system, wherein the OCT imaging system is Light source and A sample arm and a reference arm, wherein the reference arm is A reference arm optical fiber positioned to guide the reference light, An optical switch controllable to guide at least a portion of the reference light from the reference arm optical fiber to a selected optical path among N optical paths, where N is an integer of 2 or more, and each of the N optical paths has at least one of the optical path length and chromatic dispersion that is different from at least one of the optical path length and chromatic dispersion of the other optical paths among the N optical paths, An optical coupler arranged to guide at least a portion of the reference light propagating along the selected optical path to an output optical fiber, An interferometer comprising: a reference arm, and an optical splitter arranged to split light from the light source into sample light propagating along the sample arm and reference light propagating along the reference arm, The system comprises a photodetector arranged to detect interference light resulting from the interference between at least a portion of the reference light output from the output optical fiber and the sample light that is scattered by the imaging target and propagates through the sample arm, The optical switch is a 1×N optical switch having N output ports, the optical coupler is an N×1 optical coupler having N input ports, and each of the N optical paths has an optical fiber connecting each of the N output ports to each of the N input ports. Each of the N optical paths, one or more of which include a dispersion element in the optical fiber, and each of the dispersion elements is arranged to provide a respective level of wavelength dispersion of the reference light propagating through the optical path containing the dispersion element. The OCT imaging system further includes a controller, The OCT imaging system is capable of operating in multiple imaging modes to image different depth ranges of the object along the propagation direction of the sample light toward the object, During the operation of the OCT imaging system in each of the imaging modes, the controller is configured to control the optical switch to guide the reference light from the reference arm optical fiber to each of the N optical paths, each having an optical path length such that the phase difference between the sample light, which is scattered from a depth within the respective depth range of the imaging target and then received by the photodetector, and the reference light, which is propagated through the output optical fiber and then received by the photodetector, is less than a predetermined threshold. The object to be imaged is the eye, and the OCT imaging system is A first imaging mode for imaging a first portion of the anterior segment of the eye, A second imaging mode for imaging the first portion of the posterior segment of the eye, A third imaging mode for imaging the second portion of the anterior eye and the second portion of the posterior eye. It is possible to operate with at least one of the following: When the OCT imaging system is capable of operating in the first imaging mode, the controller is configured to control the optical switch to direct the reference light from the reference arm optical fiber to a first optical path among the N optical paths, the first optical path comprising a first dispersion element configured such that the level of wavelength dispersion of the sample light, after being scattered by a first portion of the anterior portion of the eye and then received by the photodetector, matches the level of wavelength dispersion of the reference light, after it has propagated through the output optical fiber and then received by the photodetector. When the OCT imaging system is capable of operating in the second imaging mode, the controller is configured to control the optical switch to direct the reference light from the reference arm optical fiber to a second optical path among the N optical paths, the second optical path comprising a second dispersion element configured such that the level of wavelength dispersion of the sample light, after being scattered by the first portion of the posterior portion of the eye and then received by the photodetector, matches the level of wavelength dispersion of the reference light, after it has propagated through the output optical fiber and then received by the photodetector. When the OCT imaging system is capable of operating in the third imaging mode, the controller is configured to control the optical switch to direct the reference light from the reference arm optical fiber to a third optical path among the N optical paths, the third optical path providing a level of wavelength dispersion of the reference light that is received by the photodetector after propagating through the output optical fiber, the level being greater than the level of wavelength dispersion of the sample light that is received by the photodetector after being scattered by the second portion of the anterior portion and / or the second portion of the posterior portion of the eye. The OCT imaging system further comprises a pupil alignment module configured to align the focus of the OCT imaging system with the pupil of the eye based on the image of the anterior segment of the eye. The OCT imaging system is configured to operate in a first imaging mode during the operation of the pupil alignment module to align the focus of the OCT imaging system with the pupil of the eye, and to operate in a second imaging mode after the operation of the pupil alignment module to align the focus of the OCT imaging system with the pupil of the eye. The aforementioned method, The system receives a signal indicating the range of imaging depths in which an image of a portion of the target being imaged is acquired. Based on the received signal, one of the N optical paths is selected. Controlling the optical switch to guide the reference light from the reference arm optical fiber to the selected optical path, The OCT imaging system is configured to acquire the image of the portion of the object to be imaged over the range of imaging depth indicated above, A method comprising controlling the configured OCT imaging system to acquire an image of a portion of the object to be imaged.

7. A computer program that, when executed by a processor, includes computer-readable instructions causing the processor to carry out the method described in Claim 6.

8. A computer-readable storage medium for storing the computer program described in Claim 7.

Images