Polarization-sensitive optical interference tomography device

Abstract

To provide a polarization-sensitive optical interference tomography device for acquiring a tomographic image on which the polarization characteristics of a sample is reflected better.SOLUTION: The polarization-sensitive optical interference tomography device is for acquiring a signal representing polarization characteristics of a sample from reflection light of measurement light applied to the sample and interference light with reference light for reference. The device has two collimators for reference light facing each other on an optical path for the reference light, and adjusts the length of the optical path for the reference light by the collimators for reference light.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Optical Coherence Tomography (OCT) is mainly used for tomography of living organs such as the eyeball in the medical field.

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

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

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

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

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

[0009] The present disclosure (4) is a polarization-sensitive optical coherence tomography apparatus in any arbitrary combination with any one of the present disclosures (1) to (3), which includes a polarization beam splitter for splitting the interference light into a vertically polarized component and a horizontally polarized component, a vertically polarization-sensitive detector for detecting the vertically polarized component, and a horizontally polarization-sensitive detector for detecting the horizontally polarized component.

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

[0011] The present disclosure (6) is a polarization-sensitive optical coherence tomography apparatus in any arbitrary combination with any one of the present disclosures (1) to (5), which includes a wavelength-sweeping light source, the wavelength-sweeping range of the light from the wavelength-sweeping light source is 100 to 200 nm, and the repetition scanning frequency is 30 to 120 kHz.

[0012] The present disclosure (7) is a polarization-sensitive optical coherence tomography apparatus in any arbitrary combination with any one of the present disclosures (1) to (6), which is configured such that a user can perform tomography while carrying the portion including the objective lens.

[0013] The present disclosure (8) is a polarization-sensitive optical coherence tomography apparatus in any arbitrary combination with any one of the present disclosures (1) to (7), which is configured such that the vertically polarized component and the horizontally polarized component of the interference light can be acquired 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 one of the present disclosures (1) to (8) including a focus-variable lens with a variable focal length.

[0015] The present disclosure (10) is such that the polarization-sensitive optical coherence tomography apparatus includes an optical path length adjustment module having the collimator for the reference light on the optical path of the reference light, and a coupler (2) that multiplexes the reflected light of the measurement light and the reference light, and a collimator for the measurement light that converts the measurement light into parallel light, and a scanning mirror that scans the measurement light irradiated to the sample, and there is no polarization control element on the optical path between the coupler (1) and the collimator for the reference light, and the two collimators for the reference light are arranged to face each other so as to be located substantially on a straight line, and the collimator for the reference light has a variable angle and / or position, and the optical path length adjustment module includes a holding member that holds each of the collimators for the reference light, and the holding member is a polarization-sensitive optical coherence tomography apparatus in any combination with any one of the present disclosures (3) to (9) capable of adjusting the angle and / or position of the collimator for the reference light.

[0016] The present disclosure (11) is a polarization-sensitive optical coherence tomography apparatus in any combination with any one of the present disclosures (1) to (10) for industrial use.

Advantages of the Invention

[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.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

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Figure 5

Embodiments for Carrying Out the Invention

[0019] Hereinafter, the present disclosure will be specifically described.

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

[0021] The OCT apparatus of the present disclosure includes two collimators for reference light disposed opposite to each other on the optical path of the reference light, and adjusts the optical path length of the reference light by the collimators, so it is easy to accurately match the optical path lengths of the measurement light and the reference light. Even when the optical path length of the measurement light may change according to the size, shape of the sample, and the imaging environment, by adjusting the optical path length of the reference light by the collimators for reference light in accordance with the change, the optical path lengths of the measurement light and the reference light can be easily matched. As a result, it becomes possible to acquire a tomographic image in which the polarization characteristics of the sample are more accurately reflected.

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

[0023] The reference light collimator preferably has a variable angle and / or position, and more preferably has a variable angle. It is preferable that the two reference light collimators can independently change the angle and / or position with respect to each other. Further, it is preferable that no optical fiber is disposed between the collimators (on the opposing side) so that the optical path length can be changed by the operation of the collimator. With the above configuration, the optical path length between the reference light collimators can be easily adjusted, and the optical path length of the reference light can be easily adjusted.

[0024] The OCT apparatus 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 only needs to have a reference light collimator. For example, it preferably includes a holding member that holds the upstream and downstream collimators, respectively. The holding member is preferably capable of adjusting the angle and / or position of the collimator, more preferably capable of adjusting the angle, and still more preferably capable of adjusting the angle in two axes (X - Y). Each holding member may be fixed to the housing of the OCT apparatus, or may be connected to each other by a connecting member such as a rod like 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. As such an optical path length adjustment module, one shown in FIG. 2 described later can be exemplified, but it is not limited thereto.

[0025] The measurement light and the reference light are generated from the light from the light source. The OCT apparatus 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 scans by changing the frequency (wavelength) over time. As the wavelength-sweeping light source, a wavelength-sweeping laser using a wavelength-sweeping filter (driven by a polygon mirror, driven by a galvanometer mirror, etc.), an FDML laser, a MEMS wavelength-sweeping light source (MEMS VCSEL, an external resonator type MEMS Fabry-Perot laser, etc.), an SGDBR laser, etc. can be used.

[0026] When using a wavelength-sweeping light source, the wavelength-sweeping range of light is preferably 100 to 200 nm, more preferably 120 nm or more, still more preferably 130 nm or more, and also more preferably 180 nm or less, still more preferably 150 nm or less. Also, the repetition scanning frequency is preferably 30 to 120 kHz, more preferably 40 kHz or more, and also more preferably 100 kHz or less, still more preferably 80 kHz or less, and even more preferably 60 kHz or less. With the above configuration, the resolution in the depth direction can be improved.

[0027] Examples of the light from the light source include visible light and infrared light, and near-infrared light (NIR) is preferred. As the light from the light source, it is preferable to use light having a central wavelength in the range of 800 to 2000 nm. As the range of the central wavelength, 950 nm or more is more preferable, and 1400 nm or less is more preferable. Among them, in terms of improving the resolution in the depth direction, light having a central wavelength of 1060 ± 50 nm or 1310 ± 50 nm is preferred, and light having a central wavelength of 1060 ± 50 nm is more preferred.

[0028] The OCT apparatus of the present disclosure preferably includes a coupler (1) that splits the light from the light source into measurement light for irradiating a sample and reference light for reference. The intensity ratio of the measurement light and the reference light generated by the coupler (1) is preferably 60:40 to 95:5, more preferably 70:30 or more, still more preferably 80:20 or more, even more preferably 85:15 or more, and also 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, and the sensitivity of OCT can be enhanced.

[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 condensing the measurement light on the sample, but is preferably a short-focus lens in terms of improving the lateral resolution. Also, it is preferably a variable-focus lens with a variable focal length in that the focus in the depth direction can be freely adjusted and a tomographic image with high resolution can be obtained.

[0030] The OCT device of the present disclosure preferably includes a polarization control element (hereinafter, also referred to as the polarization control element (1)) for adjusting the polarization state of the measurement light on the optical path of the measurement light irradiated on the sample. The polarization control element (1) is preferably provided on the optical path between the coupler (1) and the objective lens. Depending on the size, shape of the sample, and the imaging environment, it may be necessary to move the probe (the part including the objective lens) at various angles for imaging. Accordingly, when the bend of the optical fiber for transmitting the measurement light changes, the polarization state of the measurement light may change. By providing the polarization control element (1) together with the above-described collimator for reference light, the change in the polarization state of the measurement light caused by the bend of the optical fiber can be compensated more accurately.

[0031] The adjustment of the polarization state can be performed, for example, by observing the OCT signal. By observing the polarization OCT signals in two orthogonal polarization directions, adjusting so that the light and dark of the stripe pattern due to polarization in the image are inverted from each other, and adjusting so that the contrast of the light and dark of each stripe pattern is maximized, the polarization state optimal for polarization-sensitive OCT can be achieved.

[0032] The polarization control element (1) can also be provided outside the housing of the OCT device. By configuring in this way, in particular, when imaging while carrying the probe, it becomes easy to adjust to the optimal polarization state according to the sample to be imaged.

[0033] A polarization control element can also be provided on the optical path between the coupler (1) and the collimator for reference light. However, in the OCT apparatus of the present disclosure, since the optical path length can be adjusted by the collimator for reference light, it is not necessary to provide a polarization control element at the above position.

[0034] The measurement light irradiated on the sample is reflected by the sample to become reflected light (sample light), and is combined with the reference light that has passed through the collimator for reference light to become interference light. In the OCT apparatus of the present disclosure, the collimator for reference light also functions as a reference surface. Therefore, it is not necessary to separately provide a reference surface such as a reference mirror.

[0035] The OCT apparatus of the present disclosure preferably includes a coupler (2) that combines the reflected light of the measurement light and the reference light. In this case, the collimator for 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 be the one that has passed through the coupler (1). The interference light may be split into two by the coupler (2) and emitted.

[0036] A polarization control element (also referred to as a polarization control element (2)) may be provided on the optical path between the collimator for reference light 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 of amplifying a signal. Also, an amplifier may be provided separately.

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

[0039] The polarization beam splitter is preferably provided on the optical path between the coupler (2) and the vertically polarization-sensitive detector or the horizontally polarization-sensitive detector. Further, the polarization beam splitter 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 a polarization control element (3)) may be provided on the optical path between the coupler (2) and the polarization beam splitter.

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

[0042] Examples of the types of OCT that can be employed 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 them, SS-OCT is preferable in terms of high sensitivity and deep measurable depth.

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

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

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

[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 the interference signal by the measurement light and the reference light. The DAQ device preferably includes an A / D converter. The DAQ device preferably converts the collected interference signal into digital data.

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

[0049] The OCT device of the present disclosure preferably further includes a display device that displays the obtained optical coherence tomography image. The display device may be a stationary type or a portable type, but a portable type is preferable because the image can be confirmed at the imaging site. Also, the connection to the arithmetic unit may be wired or wireless. There may be one or a plurality of the display devices.

[0050] In the OCT device of the present disclosure, a device or member through which light is incident or emitted may be connected by an optical fiber. As the optical fiber, a single-mode fiber (SMF) is preferably used. The optical fiber that enters the polarization beam splitter described above (the optical fiber that forms the optical path between the coupler (2) and the polarization beam splitter) may be a polarization-maintaining fiber (PFM).

[0051] An example of the OCT device of the present disclosure is shown in FIG. 1, but the OCT device of the present disclosure is not limited thereto. In the OCT device 100 of FIG. 1, the wavelength-sweeping light source 101 outputs light used for OCT. The wavelength-sweeping light source 101 outputs a trigger signal each time the frequency scanning starts. Also, light is detected by a Mach-Zehnder interferometer, and a K clock signal for sampling at equal frequency intervals is output. The light output from the wavelength-sweeping light source 101 passes through the optical fiber 102 and is split at the coupler 103 into measurement light for irradiating the sample and reference light for reference at an intensity ratio of 90:10. The measurement light is transmitted to the probe 106 through the optical fiber 104 having a length of several meters. A polarization control element 105 for compensating for changes in the polarization state of the measurement light is provided in the optical fiber 104. In the probe 106, the measurement light is converted into parallel light by the collimator 107, then reflected by the galvanometer mirror 108, and incident on the objective lens 109. The galvanometer mirror 108 is driven by a galvanometer driver (not shown) to scan the parallel light in the XY direction perpendicular to the optical axis. The parallel light incident on the objective lens 109 is focused on the sample 110 which is the imaging target, reflected on the sample surface, returns as reflected light (sample light) through the same optical path, exits into the optical fiber 111, passes through the polarization control element 112, and is incident on the coupler 118. On the other hand, the reference light emitted from the coupler 103 passes through the optical fiber 113, passes through the collimator 115 provided in the upstream optical path length adjustment module 114, and becomes parallel light. The parallel light passes through the reverse-mode collimator 115 provided in the downstream optical path length adjustment module 114 and is guided into the 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. A schematic diagram of the optical path length adjustment module 114 is shown in FIG. 2. The optical path length adjustment module 114 includes an angle adjustment holder 114a that holds the collimator 115 so that two-axis (X-Y) angle adjustment is possible, a fixing member 114b for fixing the angle adjustment holder 114a to the housing, and a fiber connector 114c for connecting the optical fiber 113 or 116. By moving the angle adjustment holder 114a to adjust the angle of the collimator 115, the optical path length of the reference light can be adjusted. In FIG. 2, the angle adjustment holder 114a is fixed to the housing by the fixing member 114b. However, without using the fixing member 114b, the upstream and downstream angle adjustment holders 114a may be connected by a plurality of 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, passes through the polarization control element 117, is incident on the coupler 118, and is combined with the sample light to become interference light. The interference light is split into two by the coupler 118. One passes through the optical fiber 119, passes through the polarization control element 120, and is incident on the polarization beam splitter 121. The other passes through the optical fiber 124, passes through the polarization control element 125, and is incident on the polarization beam splitter 126. The interference light incident on the polarization beam splitters 121 and 126 is split into a horizontal polarization component and a vertical polarization component. The horizontal polarization component is incident on the horizontally polarization-sensitive detector 129 through the optical fibers 122 and 127, and the vertical polarization component is incident on the vertically polarization-sensitive detector 130 through the optical fibers 123 and 128. The horizontally polarization-sensitive detector 129 and the vertically polarization-sensitive detector 130 respectively detect interference signals based on the horizontal polarization component and the vertical polarization component of the interference light. The detected interference signals are collected by a DAQ device (A / D converter) (not shown) provided in the control unit (not shown) and converted into digital data. The collection of the interference signals is started by a trigger signal emitted by the wavelength-sweeping light source 101 and is performed in synchronization with the K clock signal. The arithmetic device provided in the control unit generates an optical coherence tomography 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] Preferably, the OCT device of the present disclosure is configured such that a user can perform tomography while carrying the part equipped with the objective lens. By making the part equipped with the objective lens portable in this way, imaging can be performed from various positions and angles according to the size and shape of the sample. Also, the vertical polarization component and the horizontal polarization component of the interference light can be obtained in accordance with the polarization axis of the sample. When the part equipped with the objective lens is made portable, the optical path length of the measurement light tends to change during imaging. However, since the OCT device of the present disclosure can adjust the optical path length of the reference light by the reference light collimator, an optical coherence tomography image that better reflects the polarization characteristics of the sample can be obtained.

[0053] The portion provided with the objective lens is, for example, a probe of an OCT apparatus, and preferably includes a collimator for measurement light, a scanning mirror, etc. in addition to the objective lens.

[0054] The OCT apparatus of the present disclosure is preferably configured such that a user can hold the portion provided with the objective lens by hand and perform tomography, and more preferably configured such that a user can hold the portion provided with the objective lens in one hand and perform tomography.

[0055] The OCT apparatus of the present disclosure may include, in addition to the portion provided with the objective lens, a portion that can be carried by the user during tomography. Examples of such a portion include a display device.

[0056] In the OCT apparatus of the present disclosure, the portion provided with the portable objective lens and the non-portable portion are connected via an optical fiber, and it is preferable that measurement light and its reflected light (sample light) are transmitted through the optical fiber. In this aspect, even when the imaging target is located at a place far from the non-portable portion, by adjusting the length of the optical fiber, the portion provided with the objective lens can be positioned near the imaging target to perform tomography. Further, since it is a wired type using an optical fiber, high-resolution OCT measurement can be performed on an imaging target located at a place far from the non-portable portion.

[0057] The length of the optical fiber is not particularly limited and can be determined according to the location of the imaging target. For example, it may be 0.5 m or more, preferably 1 m or more. Also, it may be 5 m or less, preferably 3 m or less. By setting it within the above range, it becomes easier to carry the portion provided with the objective lens and perform tomography while operating the devices (such as polarization control elements) arranged in the OCT apparatus main body (housing).

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

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

[0060] The OCT device of the present disclosure is preferably configured to be able to acquire the vertical polarization component and the horizontal polarization component of the interference light in accordance with the polarization axis of the sample. Thereby, a tomographic image that better reflects the polarization characteristics of the sample can be acquired. The above configuration can be realized, for example, by making the part having the objective lens (probe) portable.

[0061] Another example of the OCT device of the present disclosure (an example in which the part having the objective lens is made portable) is shown in FIG. 3, but the OCT device of the present disclosure is not limited thereto. In FIG. 3, the user 201 is carrying the probe 202 of the OCT device in one hand. The probe 202 is connected to the housing 204 of the OCT device via an optical fiber 203. The housing 204 stores a light source, a polarization control element, a collimator for reference light, a galvanometer mirror driver, a detector, a DAQ device, an arithmetic device, etc. 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 preferably used in general for polarization-sensitive optical coherence tomography regardless of the field. In particular, it can be preferably used in fields where a variety of samples are imaging targets and the optical path length of the measurement light is likely to change according to the sample and the imaging environment, for example, in the fields of physical and chemical sciences and industry. 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 detail can be made without departing from the spirit and scope of the claims.

Example

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

[0065] Example 1 Using a polarization-sensitive OCT device having the configuration shown in FIG. 1, the side surface portion of the lid of a Tombow Pencil Co., Ltd. stick glue (erasable pit N, PT-NC) was OCT imaged. As the OCT light source, a high-speed wavelength-sweeping light source manufactured by Excelitas (center wavelength: 1060 nm, sweep width: 140 nm, repetition scanning frequency: 50 kHz) was used. As the reference collimator, Thorlabs F280APC-1064 was connected to a collimator adapter (Thorlabs AD1109) and two sets of them held by a kinematic mount (Thorlabs KC05-T / M) were arranged opposite to each other. By the above OCT imaging, a sample image based on a light wave (P-polarized light wave) vibrating in the horizontal direction and a sample image based on a light wave (S-polarized light wave) vibrating in the vertical direction were obtained. A Gaussian filter was applied to all the sample images for noise removal. Background information (BG image) was removed from each of the sample images of the P-polarized light wave and the S-polarized light wave to obtain a P-polarized light wave image and an S-polarized light wave image. The following formula was used to process all the pixels of the obtained P-polarized light wave image and S-polarized light wave image to generate a phase difference image.

Equation

[0066] Example 2 Using the same polarization-sensitive OCT apparatus as in Example 1, OCT imaging of a fine pattern NBS 1963A resolution test target (R2L2S1P1 manufactured by Thorlabs) was performed. The obtained OCT image is shown in FIG. 5. It was clearly distinguishable up to about several μm, and high lateral resolution was obtained.

Explanation of Reference Numerals

[0067] 100: OCT apparatus 101: Wavelength-swept light source 102, 104, 111, 113, 116, 119, 122, 123, 124, 127, 128: Optical fibers 103, 118: Couplers 105, 112, 117, 120, 125: Polarization control elements 106: Probe 107: Collimator 108: Galvanometer mirror 109: Objective lens 110: Sample 114: Optical path length adjustment module 114a: Angle adjustment holder 114b: Fixed member 114c: Fiber connector 115: Collimator 121, 126: Polarizing beam splitters 129: Horizontally polarization-sensitive detector 130: Vertically 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 the reference light for reference, comprising two collimators for reference light arranged opposite to each other on the optical path of the reference light, A 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 for adjusting 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 splits the light from the light source into measurement light irradiated on the sample and 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 claim 1 or 2, comprising a polarization beam splitter that splits 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 claim 1 or 2, 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 claim 1 or 2, comprising a wavelength-sweeping light source, wherein the wavelength-sweeping range of the light from the wavelength-sweeping light source is 100 to 200 nm, and the repetition scanning frequency is 30 to 120 kHz.

7. The polarization-sensitive optical coherence tomography apparatus according to claim 1 or 2, configured to be capable of performing tomography while the user carries the part equipped with the objective lens.

8. The polarization-sensitive optical coherence tomography apparatus according to claim 1 or 2, 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.

9. The polarization-sensitive optical coherence tomography apparatus according to claim 1 or 2, comprising a focus-variable lens with a variable focal length.

10. The polarization-sensitive optical coherence tomography apparatus includes an optical path length adjustment module having the collimator for reference light on the optical path of the reference light, a coupler (2) that multiplexes the reflected light of the measurement light and the reference light, a collimator for measurement light that converts the measurement light into parallel light, and a scanning mirror that scans the measurement light irradiated on the sample. A polarization control element is not provided on the optical path between the coupler (1) and the collimator for reference light. The two collimators for reference light are arranged to face each other so as to be located substantially on a straight line. The angle and / or position of the collimator for reference light is variable. The optical path length adjustment module includes holding members that hold the collimators for reference light respectively. The polarization-sensitive optical coherence tomography apparatus according to claim 3, wherein the holding member is capable of adjusting the angle and / or position of the collimator for reference light. **Claim 11** The polarization-sensitive optical coherence tomography apparatus according to claim 1 or 2, which is for industrial use.

Images