Polarization-sensitive optical coherence tomography apparatus

Abstract

The purpose of the present disclosure is to provide a polarization-sensitive optical coherence tomography apparatus capable of acquiring a tomographic image in which polarization characteristics of a sample are reflected more properly. The present disclosure relates to a polarization-sensitive optical coherence tomography apparatus for acquiring a signal representing polarization characteristics of a sample from interference light generated by reflected light of measurement light radiated onto the sample and reference light for reference. The polarization-sensitive optical coherence tomography apparatus includes two collimators for reference light arranged to face each other along an optical path of the reference light, and adjusts the optical path length of the reference light by the collimators for reference light.

Description

Polarization-sensitive optical coherence tomography device

[0001] The present disclosure relates to polarization-sensitive optical coherence tomography devices.

[0002] Optical coherence tomography (OCT) is primarily used in the medical field for tomography of biological organs such as the eyeball.

[0003] Patent Document 1 describes a polarization OCT device in which a polarization controller is arranged in each of a measurement light side fiber, a reference light side fiber, and a detector side fiber.

[0004] JP 2015-130974 A

[0005] An object of the present disclosure is to provide a polarization-sensitive optical coherence tomography apparatus capable of acquiring a tomographic image that better reflects the polarization characteristics of a sample.

[0006] The present disclosure (1) is a polarization-sensitive optical coherence tomography device that acquires a signal representing the polarization characteristics of a sample from interference light between reflected light of measurement light irradiated onto the sample and reference light for reference, the polarization-sensitive optical coherence tomography device comprising two reference light collimators arranged opposite each other on the optical path of the reference light, and that adjusts the optical path length of the reference light by the reference light collimators.

[0007] The present disclosure (2) is a polarization-sensitive optical coherence tomography apparatus according to the present disclosure (1), which is provided with a polarization control element on the optical path of the measurement light irradiated onto the sample, for adjusting the polarization state of the measurement light.

[0008] The present disclosure (3) is a polarization-sensitive optical coherence tomography device according to the present disclosure (1) or (2), which includes a coupler (1) that splits light from a light source into measurement light that is irradiated onto the sample and the reference light, and the intensity ratio between the measurement light and the reference light is 60:40 to 95:5.

[0009] The present disclosure (4) is a polarization-sensitive optical coherence tomography device in any combination with any of the present disclosures (1) to (3), which includes a polarizing beam splitter that splits the interference light into a vertically polarized component and a horizontally polarized component, a vertical polarization-sensitive detector that detects the vertically polarized component, and a horizontal polarization-sensitive detector that detects the horizontally polarized component.

[0010] The present disclosure (5) is a polarization-sensitive optical coherence tomography device that uses light having a center wavelength in the range of 950 to 1400 nm as light from a light source, and is any combination with any of the present disclosures (1) to (4).

[0011] The present disclosure (6) is a polarization-sensitive optical coherence tomography device in any combination with any of the present disclosures (1) to (5), which includes a wavelength swept light source, the wavelength sweep width of light from the wavelength swept light source being 100 to 200 nm, and the repetitive scanning frequency being 30 to 120 kHz.

[0012] The present disclosure (7) is a polarization-sensitive optical coherence tomography device that can be combined with any of the present disclosures (1) to (6) and is configured so that a user can perform tomography while carrying the part that includes the objective lens.

[0013] The present disclosure (8) is a polarization-sensitive optical coherence tomography device that can be arbitrarily combined with any of the present disclosures (1) to (7) and is configured to be capable of acquiring the vertically polarized component and the horizontally polarized component of the interference light in accordance with the polarization axis of the sample.

[0014] The present disclosure (9) is a polarization-sensitive optical coherence tomography apparatus in any combination with any of the present disclosures (1) to (8) that includes a focus variable lens with a variable focal length.

[0015] The present disclosure (10) is a polarization-sensitive optical coherence tomography device in any combination with any of the present disclosures (3) to (9), wherein the polarization-sensitive optical coherence tomography device comprises an optical path length adjustment module having the reference light collimator on the optical path of the reference light, a coupler (2) that combines reflected light of the measurement light and the reference light, a measurement light collimator that converts the measurement light into parallel light, and a scanning mirror that scans the measurement light to be irradiated onto the sample, wherein no polarization control element is provided on the optical path between the coupler (1) and the reference light collimator, the two reference light collimators are arranged opposite to each other so as to be positioned substantially in a straight line, the reference light collimator has a variable angle and / or position, the optical path length adjustment module comprises holding members that respectively hold the reference light collimators, and the holding members are capable of adjusting the angle and / or position of the reference light collimator.

[0016] The present disclosure (11) is a polarization-sensitive optical coherence tomography apparatus for industrial use, which can be arbitrarily combined with any of the present disclosures (1) to (10).

[0017] According to the present disclosure, it is possible to provide a polarization-sensitive optical coherence tomography apparatus capable of acquiring a tomographic image that better reflects the polarization characteristics of a sample.

[0018] Fig. 1 is a schematic diagram showing an example of an OCT device of the present disclosure; Fig. 2 is a schematic diagram showing an example of an optical path length adjustment module; Fig. 3 is a schematic diagram showing another example of an OCT device of the present disclosure; Fig. 4 is a diagram showing an OCT image obtained in Example 1; Fig. 5 is a diagram showing an OCT image obtained in Example 2;

[0019] The present disclosure will be specifically described below.

[0020] The present disclosure relates to a polarization-sensitive optical coherence tomography (polarization-sensitive OCT) device that acquires a signal representing the polarization characteristics of a sample from the interference light between the reflected light of measurement light irradiated onto the sample and a reference light for reference, the polarization-sensitive OCT device having two reference light collimators arranged opposite each other on the optical path of the reference light, and that adjusts the optical path length of the reference light using the reference light collimators (hereinafter also referred to as the OCT device of the present disclosure).

[0021] The OCT device disclosed herein includes two reference beam collimators arranged opposite each other on the optical path of the reference beam. The collimators adjust the optical path length of the reference beam, making it easy to accurately match the optical path lengths of the measurement beam and the reference beam. Even if the optical path length of the measurement beam changes depending on the size and shape of the sample or the imaging environment, the optical path lengths of the measurement beam and the reference beam can be easily matched by adjusting the optical path length of the reference beam using the reference beam collimators in accordance with these changes. As a result, it becomes possible to acquire a tomographic image that better reflects the polarization characteristics of the sample.

[0022] The collimators for the reference light are disposed opposite each other on the optical path of the reference light, and it is preferable that the two collimators are disposed opposite each other so as to be positioned substantially in a straight line. It is also preferable that the collimators are disposed opposite each other so that light emitted from one (upstream) collimator is incident on the other (downstream) collimator. It is also preferable that the downstream collimator is used in reverse mode (reverse input).

[0023] The reference beam collimator preferably has a variable angle and / or position, more preferably a variable angle. The two reference beam collimators are preferably capable of changing their angles and / or positions independently of each other. Furthermore, it is preferable that no optical fiber is disposed between the collimators (on the opposing sides) so that the optical path length can be changed by operating the collimators. With the above configuration, the optical path length between the reference beam collimators can be easily adjusted, and the optical path length of the reference beam can be easily adjusted.

[0024] The OCT device of the present disclosure preferably includes an optical path length adjustment module having the above-described reference light collimator on the optical path of the reference light. The optical path length adjustment module may include a reference light collimator, but preferably includes, for example, holding members for holding the upstream and downstream collimators, respectively. The holding members preferably allow adjustment of the angle and / or position of the collimators, more preferably angle adjustment, and even more preferably angle adjustment along two axes (X-Y). Each holding member may be fixed to the housing of the OCT device, or may be connected to each other by a connecting member such as a rod, as in an optical cage system. The optical path length adjustment module may further include a connecting member for connecting an optical fiber to the optical path length adjustment module. An example of such an optical path length adjustment module is shown in FIG. 2, which will be described later, but is not limited thereto.

[0025] The measurement light and the reference light are generated from light from a light source. The OCT device of the present disclosure may include a light source. The light source may be a low-coherence light source, and is preferably a wavelength-swept light source (frequency-swept light source) that changes and scans the frequency (wavelength) over time. Examples of the wavelength-swept light source include a wavelength-swept laser using a wavelength-swept filter (driven by a polygon mirror, driven by a galvanometer mirror, etc.), an FDML laser, a MEMS wavelength-swept light source (MEMS VCSEL, external cavity MEMS Fabry-Perot laser, etc.), an SGDBR laser, etc.

[0026] When a wavelength swept light source is used, the wavelength sweep width of the light is preferably 100 to 200 nm, more preferably 120 nm or more, even more preferably 130 nm or more, more preferably 180 nm or less, and even more preferably 150 nm or less. Furthermore, the repetitive scanning frequency is preferably 30 to 120 kHz, more preferably 40 kHz or more, more preferably 100 kHz or less, even more preferably 80 kHz or less, and even more preferably 60 kHz or less. The above configuration can improve the resolution in the depth direction (depth direction).

[0027] Examples of light from the light source include visible light and infrared light, with near-infrared light (NIR) being preferred. Light from the light source preferably has a central wavelength in the range of 800 to 2000 nm. The central wavelength range is more preferably 950 nm or more, and more preferably 1400 nm or less. Among these, light with a central wavelength of 1060±50 nm or 1310±50 nm is preferred, with light with a central wavelength of 1060±50 nm being more preferred, in terms of improving resolution in the depth direction (depth direction).

[0028] The OCT device of the present disclosure preferably includes a coupler (1) that splits light from a light source into measurement light that irradiates a sample and reference light for reference. The intensity ratio of the measurement light to the reference light generated by the coupler (1) is preferably 60:40 to 95:5, more preferably 70:30 or more, even more preferably 80:20 or more, even more preferably 85:15 or more, and even more preferably 92:8 or less. By setting the intensity ratio within the above range, the irradiation intensity of the measurement light on the sample can be increased, thereby improving the sensitivity of OCT.

[0029] The OCT device of the present disclosure may include an objective lens for irradiating a sample with measurement light. The objective lens is not limited as long as it is a lens capable of focusing the measurement light on the sample, but is preferably a short-focus lens in terms of improving lateral resolution. Furthermore, a variable-focus lens with a variable focal length is also preferable in terms of being able to freely manipulate the focus in the depth direction and obtaining high-resolution tomographic images.

[0030] The OCT device of the present disclosure preferably includes a polarization control element (hereinafter also referred to as polarization control element (1)) on the optical path of the measurement light irradiated onto the sample, which adjusts the polarization state of the measurement light. The polarization control element (1) is preferably provided on the optical path between the coupler (1) and the objective lens. Depending on the size and shape of the sample and the imaging environment, it may be necessary to move the probe (the part including the objective lens) to various angles to capture images. If the bending of the optical fiber transmitting the measurement light changes accordingly, the polarization state of the measurement light may change. By including the polarization control element (1) together with the above-mentioned reference light collimator, changes in the polarization state of the measurement light due to bending of the optical fiber can be more accurately compensated for.

[0031] The polarization state can be adjusted, for example, by observing the OCT signal. By observing polarized OCT signals in two orthogonal polarization directions and adjusting the polarization so that the shading of the striped patterns in the image is inverted and the contrast between the shading of each striped pattern is maximized, the optimal polarization state for polarization-sensitive OCT can be achieved.

[0032] The polarization control element (1) can also be provided on the outside of the housing of the OCT device. This configuration makes it easy to adjust the polarization state to the optimum state according to the sample to be imaged, especially when imaging while carrying a probe.

[0033] A polarization control element can be provided on the optical path between the coupler (1) and the reference light collimator. However, in the OCT device of the present disclosure, the optical path length can be adjusted by the reference light collimator, so there is no need to provide a polarization control element at the above location.

[0034] The measurement light irradiated onto the sample is reflected by the sample to become reflected light (sample light), which is then combined with the reference light that has passed through the reference light collimator to become interference light. Note that in the OCT device of the present disclosure, the reference light collimator also functions as a reference surface. Therefore, there is no need to provide a separate reference surface such as a reference mirror.

[0035] The OCT device of the present disclosure preferably includes a coupler (2) that combines reflected light of the measurement light and reference light. In this case, a collimator for the reference light is preferably provided on the optical path of the reference light between the coupler (1) and the coupler (2). The reflected light of the measurement light to be combined may have passed through the coupler (1). The interference light may be split into two by the coupler (2) and then emitted.

[0036] A polarization control element (also referred to as polarization control element (2)) may be provided on the optical path between the reference light collimator and the coupler (2) and on the optical path of the measurement light between the coupler (1) and the coupler (2).

[0037] The OCT apparatus of the present disclosure acquires a signal representing the polarization characteristics of the sample from the interference light. The OCT apparatus of the present disclosure preferably includes a detector that detects an interference signal based on the interference light. The detector is preferably a differential photodetector and may have a function to amplify the signal. Alternatively, an amplifier may be provided separately.

[0038] The OCT device of the present disclosure preferably includes a polarizing beam splitter that splits the interference light into a vertically polarized component and a horizontally polarized component, a vertical polarization-sensitive detector that detects the vertically polarized component, and a horizontal polarization-sensitive detector that detects the horizontally polarized component. With this configuration, information from both the vertically and horizontally polarized components can be obtained, and a tomographic image that better reflects the polarization characteristics of the sample can be obtained.

[0039] The polarizing beam splitter is preferably provided on the optical path between the coupler (2) and the vertical polarization-sensitive detector or the horizontal polarization-sensitive detector, and is preferably provided on each optical path of the interference light split into two by the coupler (2).

[0040] A polarization control element (also referred to as polarization control element (3)) may be provided on the optical path between the coupler (2) and the polarizing beam splitter.

[0041] The interferometer that can be employed in the OCT device of the present disclosure is not particularly limited, and examples thereof include a Michelson interferometer and a Mach-Zehnder interferometer.

[0042] Examples of types of OCT that can be used in the OCT device of the present disclosure include time domain OCT (TD-OCT) and Fourier domain OCT (FD-OCT). Examples of FD-OCT include spectral domain OCT (SD-OCT) and swept source OCT (SS-OCT). Among these, SS-OCT is preferred because of its high sensitivity and large measurable depth.

[0043] The OCT device of the present disclosure preferably further includes a measurement light collimator that converts the measurement light into parallel light. The measurement light collimator is preferably provided on the optical path between the light source and the objective lens, more preferably on the optical path between the coupler (1) and the objective lens, and even more preferably on the optical path between the polarization control element (1) and the objective lens. As the measurement light collimator, it is preferable to use a collimating lens with a large diameter in order to improve lateral resolution. The diameter of the measurement light collimator is preferably, for example, 2 mm or more, more preferably 4 mm or more, and preferably 12 mm or less in terms of portability of the probe.

[0044] The OCT device of the present disclosure preferably further includes a scanning mirror that scans the measurement light irradiated onto the sample. The scanning mirror is preferably provided on the optical path between the light source and the objective lens, more preferably on the optical path between the coupler (1) and the objective lens, and even more preferably on the optical path between the measurement light collimator and the objective lens.

[0045] Examples of the scanning mirror include a galvanometer mirror, a polygon mirror, a MEMS mirror, etc. Among these, a galvanometer mirror is preferred, a uniaxial or biaxial galvanometer mirror is more preferred, and a biaxial galvanometer mirror is even more preferred.

[0046] The OCT apparatus of the present disclosure preferably further includes a driving device for driving the scanning mirror.

[0047] The OCT apparatus of the present disclosure preferably further includes a data acquisition (DAQ) device that collects interference signals due to the measurement light and the reference light. The DAQ device preferably includes an A / D converter. The DAQ device preferably converts the collected interference signals into digital data.

[0048] The OCT apparatus of the present disclosure preferably further includes a calculation device that generates an optical coherence tomographic image based on an interference signal between the measurement light and the reference light, and the calculation device generates the optical coherence tomographic image by imaging the interference signal according to characteristics such as intensity.

[0049] The OCT apparatus of the present disclosure preferably further includes a display device for displaying the obtained optical coherence tomographic image. The display device may be a stationary or portable type, but a portable type is preferable because it allows the image to be checked at the imaging site. The connection to the computing device may be wired or wireless. The display device may be one or more.

[0050] In the OCT device of the present disclosure, devices or components through which light enters or exits may be connected by optical fibers. A single-mode fiber (SMF) is preferably used as the optical fiber. The optical fiber entering the polarizing beam splitter (the optical fiber forming the optical path between the coupler (2) and the polarizing beam splitter) may be a polarization-maintaining fiber (PFM).

[0051] FIG. 1 illustrates an example of an OCT apparatus according to the present disclosure, but the OCT apparatus according to the present disclosure is not limited to this example. In the OCT apparatus 100 of FIG. 1 , a wavelength-swept light source 101 outputs light used for OCT. The wavelength-swept light source 101 outputs a trigger signal each time a frequency scan begins. The light is detected by a Mach-Zehnder interferometer and a K clock signal is output for sampling at equal frequency intervals. The light output from the wavelength-swept light source 101 passes through an optical fiber 102 and is split by a coupler 103 into a measurement light beam to be irradiated onto a sample and a reference light beam for reference, with an intensity ratio of 90:10. The measurement light is transmitted to a probe 106 through an optical fiber 104 several meters long. The optical fiber 104 is provided with a polarization control element 105 that compensates for changes in the polarization state of the measurement light. In the probe 106, the measurement light is converted into parallel light by a collimator 107, reflected by a galvanometer mirror 108, and incident on an objective lens 109. The galvanometer mirror 108 is driven by a galvanometer mirror driver (not shown) to scan the collimated light in the X and Y directions perpendicular to the optical axis. The collimated light incident on the objective lens 109 is focused on a sample 110, which is the object of imaging, reflected from the sample surface, and returns to the coupler 103 along the same optical path as the sample light. The light is then emitted to an optical fiber 111, passes through a polarization control element 112, and enters the coupler 118. Meanwhile, the reference light emitted from the coupler 103 passes through an optical fiber 113 and a collimator 115 provided in the upstream optical path length adjustment module 114 to become collimated light. The collimated light then passes through a reverse-mode collimator 115 provided in the downstream optical path length adjustment module 114 and is guided to an optical fiber 116. The upstream and downstream optical path length adjustment modules 114 each include a collimator 115, and the two collimators 115 are arranged to face each other. 2 shows a schematic diagram of the optical path length adjustment module 114. The optical path length adjustment module 114 includes an angle adjustment holder 114a that holds the collimator 115 so that the angle can be adjusted along two axes (X-Y), a fixing member 114b that fixes the angle adjustment holder 114a to the housing, and a fiber connector 114c that connects the optical fiber 113 or 116.The optical path length of the reference light can be adjusted by moving the angle adjustment holder 114a to adjust the angle of the collimator 115. While the angle adjustment holder 114a is fixed to the housing by the fixing member 114b in FIG. 2 , the fixing member 114b may not be used and the upstream and downstream angle adjustment holders 114a may be connected by multiple steel rods to form an optical cage system. The reference light emitted from the downstream optical path length adjustment module 114 passes through the optical fiber 116, the polarization control element 117, and the coupler 118, where it is combined with the sample light to form interference light. The interference light is split into two by the coupler 118; one passes through the optical fiber 119, the polarization control element 120, and the polarizing beam splitter 121; and the other passes through the optical fiber 124, the polarization control element 125, and the polarizing beam splitter 126. The interference light incident on the polarizing beam splitters 121 and 126 is split into a horizontally polarized component and a vertically polarized component. The horizontally polarized component travels through optical fibers 122 and 127 to a horizontal polarization-sensitive detector 129, and the vertically polarized component travels through optical fibers 123 and 128 to a vertical polarization-sensitive detector 130. The horizontal polarization-sensitive detector 129 and the vertical polarization-sensitive detector 130 detect interference signals based on the horizontally polarized component and the vertically polarized component of the interference light, respectively. The detected interference signals are collected and converted into digital data by a DAQ device (A / D converter) (not shown) included in a control unit (not shown). Collection of the interference signals is initiated by a trigger signal emitted by the wavelength-swept light source 101 and is performed in synchronization with the K clock signal. A calculation device included in the control unit generates an optical coherence tomographic image of the sample 110 based on the interference signals converted by the DAQ device and displays it on a mobile display (not shown).

[0052] The OCT device of the present disclosure is preferably configured so that a user can perform tomographic imaging while carrying the portion including the objective lens. Making the portion including the objective lens portable in this manner allows imaging to be performed from various positions and angles depending on the size and shape of the sample. It is also possible to acquire vertically polarized and horizontally polarized components of interference light in accordance with the polarization axis of the sample. When the portion including the objective lens is portable, the optical path length of the measurement light is likely to change during imaging. However, the OCT device of the present disclosure can adjust the optical path length of the reference light using a reference light collimator, thereby enabling the acquisition of tomographic images that better reflect the polarization characteristics of the sample.

[0053] The part including the objective lens is, for example, a probe of an OCT device, and preferably includes a measuring light collimator, a scanning mirror, and the like in addition to the objective lens.

[0054] The OCT device of the present disclosure is preferably configured so that a user can hold the part with the objective lens in one hand and perform tomography, and more preferably configured so that a user can hold the part with the objective lens in one hand and perform tomography.

[0055] The OCT apparatus of the present disclosure may include a part that can be carried by the user when performing tomography, in addition to the part that includes the objective lens. Such a part may include, for example, a display device.

[0056] In the OCT device disclosed herein, it is preferable that the portion including the portable objective lens and the non-portable portion are connected via an optical fiber, and the measurement light and its reflected light (sample light) are transmitted through the optical fiber. In this aspect, even if the imaging target is located far from the non-portable portion, by adjusting the length of the optical fiber, the portion including the objective lens can be positioned near the imaging target to perform tomographic imaging. Furthermore, because it is a wired type using an optical fiber, high-resolution OCT measurement can be performed even on an imaging target located far from the non-portable portion.

[0057] The length of the optical fiber is not particularly limited and can be determined depending on the location of the imaging target, but may be, for example, 0.5 m or more, preferably 1 m or more. It may also be 5 m or less, preferably 3 m or less. By setting the length within the above range, it becomes easy to carry the part including the objective lens and perform tomography while operating the equipment (polarization control element, etc.) arranged in the OCT device main body (housing).

[0058] The non-portable part is, for example, the OCT device main body (housing), which preferably includes a light source, a polarization control element, a collimator for reference light, a detector, a DAQ device, a computing device, and the like.

[0059] If there is a portable part other than the part having the objective lens, the connection between that part and the part having the objective lens or the non-portable part is not necessarily limited to a connection by optical fiber, but may also be a connection by, for example, an electric wire.

[0060] The OCT device of the present disclosure is preferably configured to acquire vertically polarized and horizontally polarized components of interference light in alignment with the polarization axis of the sample. This allows for the acquisition of a tomographic image that better reflects the polarization characteristics of the sample. The above configuration can be achieved, for example, by making the part (probe) that includes the objective lens portable.

[0061] Another example of the OCT device of the present disclosure (an example in which the portion including the objective lens is portable) is shown in FIG. 3 , but the OCT device of the present disclosure is not limited to this. In FIG. 3 , a user 201 carries a probe 202 of the OCT device in one hand. The probe 202 is connected to a housing 204 of the OCT device via an optical fiber 203. The housing 204 houses a light source, a polarization control element, a collimator for reference light, a galvanometer mirror driver, a detector, a DAQ device, a computing device, and the like. In addition, a polarization control element 205 for measurement light is installed outside the housing 204, and can be operated by the user 201 during tomography.

[0062] The OCT device of the present disclosure can be suitably used for polarization-sensitive optical coherence tomography in general, regardless of the field. In particular, it can be suitably used in fields where a wide variety of samples are imaged and the optical path length of the measurement light is likely to change depending on the sample and the imaging environment, such as the physical and chemical fields and industrial fields. The OCT device of the present disclosure is preferably for physical and chemical use or industrial use, and more preferably for industrial use.

[0063] Although the embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims.

[0064] The present disclosure will now be described in more detail with reference to examples, but the present disclosure is not limited to these examples.

[0065] Example 1: Using a polarization-sensitive OCT device having the configuration shown in Figure 1, OCT images were taken of the side of the lid of a Tombow Pencil Co., Ltd. glue stick (Kieiro Pit N, PT-NC). A high-speed wavelength swept light source manufactured by Excelitas (center wavelength: 1060 nm, sweep width: 140 nm, repetitive scanning frequency: 50 kHz) was used as the OCT light source. Two sets of Thorlabs F280APC-1064 reference collimators, connected to a collimator adapter (Thorlabs AD1109) and held on a kinematic mount (Thorlabs KC05-T / M), were placed opposite each other. The OCT images obtained included sample images based on light waves oscillating in the horizontal direction (P-polarized waves) and light waves oscillating in the vertical direction (S-polarized waves). A Gaussian filter was applied to all sample images to remove noise. Background information (BG image) was removed from each sample image of P polarized light and S polarized light to obtain P polarized light images and S polarized light images. All pixels of the obtained P polarized light images and S polarized light images were processed using the following equation to generate phase contrast images. (In the formula, I ｐ (x, z) and I ｓ(x, z) represent the interference signals of the P-polarized and S-polarized waves, respectively, with background information removed.) The obtained P-polarized wave image, S-polarized wave image, and phase-contrast image are shown in Figures 4(a), (b), and (c), respectively. The images show interference fringes specific to the sample, clearly reflecting the polarization characteristics of the sample.

[0066] Example 2: Using the same polarization-sensitive OCT device as in Example 1, OCT images were taken of a fine-pattern NBS 1963A resolution test target (R2L2S1P1 manufactured by Thorlabs). The obtained OCT image is shown in Figure 5. It was clearly distinguishable down to a few micrometers, and high lateral resolution was obtained.

[0067] 100: OCT device 101: Wavelength swept light source 102, 104, 111, 113, 116, 119, 122, 123, 124, 127, 128: Optical fiber 103, 118: Coupler 105, 112, 117, 120, 125: Polarization control element 106: Probe 107: Collimator 108: Galvanometer mirror 109: Objective lens 110: Sample 114: Optical path length adjustment module 114a: Angle adjustment holder 114b: Fixing member 114c: Fiber connector 115: Collimator 121, 126: Polarizing beam splitter 129: Horizontal polarization-sensitive detector 130: Vertical polarization-sensitive detector 201: User 202: Probe 203: Optical fiber 204: Housing 205: Polarization control element

Claims

1. A polarization-sensitive optical coherence tomography apparatus that acquires a signal representing the polarization characteristics of a sample from the interference light between the reflected light of the measurement light irradiated on the sample and a reference light for reference, the apparatus comprising two collimators for reference light disposed opposite to each other on the optical path of the reference light, and the polarization-sensitive optical coherence tomography apparatus that adjusts the optical path length of the reference light by the collimator for reference light.

2. The polarization-sensitive optical coherence tomography apparatus according to claim 1, further comprising a polarization control element that adjusts the polarization state of the measurement light on the optical path of the measurement light irradiated on the sample.

3. The polarization-sensitive optical coherence tomography apparatus according to claim 1 or 2, comprising a coupler (1) that divides the light from the light source into measurement light irradiated on the sample and the reference light, and the intensity ratio of the measurement light to the reference light is 60:40 to 95:

5.

4. The polarization-sensitive optical coherence tomography apparatus according to any one of claims 1 to 3, comprising a polarization beam splitter that divides the interference light into a vertically polarized component and a horizontally polarized component, a vertically polarized light-sensitive detector that detects the vertically polarized component, and a horizontally polarized light-sensitive detector that detects the horizontally polarized component.

5. The polarization-sensitive optical coherence tomography apparatus according to any one of claims 1 to 4, using light having a central wavelength in the range of 950 to 1400 nm as the light from the light source.

6. The polarization-sensitive optical coherence tomography apparatus according to any one of claims 1 to 5, comprising a wavelength-sweeping light source, the wavelength-sweeping width of the light from the wavelength-sweeping light source being 100 to 200 nm, and the repetition scanning frequency being 30 to 120 kHz.

7. The polarization-sensitive optical coherence tomography apparatus according to any one of claims 1 to 6, configured to be able to perform tomography while a user carries a portion including the objective lens.

8. The polarization-sensitive optical coherence tomography apparatus according to any one of claims 1 to 7, configured to be able to acquire the vertically polarized component and the horizontally polarized component of the interference light in accordance with the polarization axis of the sample.

9. The polarization-sensitive optical coherence tomography apparatus according to any one of claims 1 to 8, comprising a focus-variable lens with a variable focal length.

10. The polarization-sensitive optical coherence tomography apparatus includes, on the optical path of the reference light, an optical path length adjustment module having the reference light collimator, a coupler (2) that multiplexes the reflected light of the measurement light and the reference light, a measurement light collimator that converts the measurement light into parallel light, and a scanning mirror that scans the measurement light irradiated on the sample. The polarization control element is not provided on the optical path between the coupler (1) and the reference light collimator. The two reference light collimators are arranged to face each other so as to be positioned substantially in a straight line. The reference light collimator has a variable angle and / or position. The optical path length adjustment module includes a holding member that holds each of the reference light collimators. The holding member is capable of adjusting the angle and / or position of the reference light collimator. The polarization-sensitive optical coherence tomography apparatus according to any one of claims 3 to 9.

11. The polarization-sensitive optical coherence tomography apparatus according to any one of claims 1 to 10, which is for industrial use.

Images