PSOCT system for adjusting circular polarization based on feedback and adjusting method

Abstract

The invention discloses a PSOCT system based on feedback adjustment circular polarization and an imaging method, and belongs to the field of polarization sensitive optical coherence imaging. A Stokes vector is calculated in real time by analyzing a backscattered light signal on the surface of a sample tissue collected by the system, and the Stokes vector is compared with a target circular polarization state position on a Poincare sphere. And then, the feedback control module dynamically adjusts a fourth polarization controller according to a deviation signal generated by comparison, so that the polarization state change caused by bending or shaking of the sample arm optical fiber is compensated, and the detection light irradiated to the surface of the sample tissue is always kept in a stable circular polarization state. Under the conditions that additional polarization measurement hardware is not added and the system structure is not changed, the problem that the polarization state of a single-state input PSOCT system is unstable is effectively solved, the accuracy and repeatability of birefringence imaging are remarkably improved, and clinical transformation and application are better facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of PSOCT imaging technology, and particularly relates to a PSOCT system based on feedback regulation of circular polarization. BACKGROUND

[0002] Optical coherence tomography (OCT) is a high-resolution optical coherence imaging technology, and its imaging resolution reaches microns. It has been widely used in ophthalmology, dermatology, and cardiovascular medicine. As an extension of OCT imaging technology, polarization-sensitive optical coherence tomography (PSOCT) uses polarization contrast to extract additional tissue-specific structure and composition information, enabling three-dimensional imaging of birefringent structures and providing microscopic structural arrangement of anisotropic tissues. This birefringence-based contrast has been proven to be of great significance in the diagnosis and monitoring of pathological conditions in clinical practice.

[0003] However, the PS-OCT technology faces many challenges in further industrialization and popularization: the stability of the polarization state irradiated onto the tissue, the error caused by polarization mode dispersion (PMD), etc. In the process of using the single-state input system, the sample arm fiber inevitably bends, shakes or vibrates, which will cause the polarization state irradiated onto the sample tissue to change uncontrollably, destroy the expected circular polarization input, cause deviation in the reconstruction of polarization information, and affect the accuracy and repeatability of birefringence imaging. The double-state input system uses time division multiplexing or polarization multiplexing technology to make the probe light incident on the sample tissue have a preset orthogonal polarization state, which can avoid the influence of polarization state changes in the sample arm. However, the double-state input system significantly increases the complexity of the system and reduces the imaging speed, which is not conducive to clinical transformation. In contrast, the single-state input system is simpler and easier to use, but the problem of sensitivity to polarization state changes needs to be overcome. The traditional methods of monitoring the polarization state mainly include two kinds: one is to directly measure the polarization state of the output light through a polarization measuring instrument; the other is to measure the optical power through an optical power meter, and to indirectly judge through the optical power. However, both methods need to introduce additional measuring devices, and will change the original optical path state, which is extremely inconvenient in actual use. Therefore, how to simply and accurately monitor the polarization state and timely adjust and restore the circular polarization in the single-state input system is of great importance. SUMMARY

[0004] Therefore, the purpose of this invention is to provide a PSOCT system and imaging method based on feedback-adjusted circular polarization, which aims to solve the problem that the sample arm fiber in a single-state input PSOCT system is easily disturbed, leading to instability of the incident circular polarization state and thus affecting the accuracy of birefringence imaging. The goal is to achieve stable and reliable birefringence imaging while maintaining a simple system structure and facilitating clinical translation.

[0005] To achieve the above objectives, this invention provides a PSOCT system based on feedback-adjusted circular polarization, comprising: a swept-frequency light source, a first coupler, a sample arm, a reference arm, a second coupler, a polarization beam splitter, and a balanced detector. Light emitted from the swept-frequency light source is split by the first coupler and enters the sample arm and the reference arm; the sample light and the reference arm light interfere with each other at the second coupler; the interfering light is separated by the polarization beam splitter and converted into an electrical signal by the balanced detector; characterized in that it further comprises: A fourth polarization controller, disposed in the sample arm, is used to adjust the polarization state of the sample light irradiating the sample tissue; The feedback control module is used to acquire and analyze the electrical signal of the balanced detector in real time, calculate the polarization state of the sample surface and compare it with the target circular polarization, generate a control signal to drive the fourth polarization controller to dynamically adjust so that the sample light forms and maintains stable circular polarization on the sample tissue surface.

[0006] More preferably, a first polarization controller is also provided in the sample arm after the first coupler splits the beam. The first polarization controller is located between the first coupler and the second circulator to maximize the output optical power of the second circulator. A second polarization controller is provided between the second coupler and the first circulator; the second polarization controller is used to maximize the interference amplitude of the two interference channels; A third polarization controller is provided between the second coupler and the second circulator, which is used to maximize the contrast between the two orthogonal interference channels.

[0007] More preferably, the fourth polarization controller is a motor-driven annular polarization controller, and the feedback control module changes the orbital state of the annular polarization controller by controlling the rotation angle of the motor, thereby achieving fine adjustment of the polarization state.

[0008] More preferably, the annular polarization controller has a three-ring structure, which is equivalent to a λ / 4 waveplate, a λ / 2 waveplate, and a λ / 4 waveplate in sequence; the feedback control module controls the deflection angle of the three rings independently to make the polarization state of the sample surface approach the target circular polarization.

[0009] This invention also provides a PSOCT imaging method based on feedback-adjusted circular polarization, applied to the aforementioned PSOCT system based on feedback-adjusted circular polarization; comprising the following steps: S1. Adjust the probe to acquire images of the region of interest in the sample tissue; S2. Based on the region of interest, perform image segmentation to identify the surface of the sample tissue; S3. Select several pixels at the center of the sample tissue surface, calculate their surface Stokes vectors and normalize them to obtain the average normalized polarization state matrix. ; S4. Based on the averaged normalized polarization state matrix The deviation from the target circular polarization state is dynamically adjusted by the fourth polarization controller until the sample light forms stable circular polarization light on the sample tissue surface; S5. Using the generated circularly polarized light, perform three-dimensional polarization-sensitive optical coherence tomography imaging on the region of interest.

[0010] More preferably, in S1, adjusting the probe to acquire images of the region of interest in the sample tissue includes: After initial calibration is completed, the OCT image preview mode is used for previewing. The imaging probe is moved to change the position of the beam illumination. After the region of interest of the sample tissue is determined, the probe is stopped and the image is acquired. The polarization state is adjusted based on the acquired image.

[0011] Further preferably, in S2, image segmentation is performed based on the region of interest to identify the sample tissue surface, including: preprocessing the acquired raw data of two orthogonal polarization states, H-channel data and V-channel data, and then performing a Fourier transform to convert them into H-channel Fourier domain complex signals. and V-channel Fourier domain complex signal The Stokes vectors I, Q, U, and V are constructed using the following formula: Where θ is the phase difference between the H and V channels. yes The conjugate of complex numbers, Represents the imaginary part of a complex number. The real part of the complex number is represented by Q and U, which describe the linearly polarized components in the x and y directions, respectively. V describes the circularly polarized component of light. 2 =Q 2 +U 2 +V 2 I represents the light intensity envelope, indicating the total light intensity of each pixel. The sample tissue surface is segmented based on the light intensity envelope.

[0012] Furthermore, the process of segmenting the sample tissue surface based on the light intensity envelope includes the following steps: The intensity threshold is obtained by multiplying the maximum light intensity on each Ascan data by a preset light intensity ratio threshold η. The first pixel on the Ascan data from the near end to the far end that is greater than the intensity threshold is regarded as the sample tissue surface.

[0013] Furthermore, in S3, several pixels at the center of the sample tissue surface are selected, their surface Stokes vectors are calculated and normalized to obtain the average normalized polarization state matrix. ,include: After normalizing the Stokes vectors I, Q, U, and V, a polarization state matrix that can characterize the polarization state of each pixel is constructed using the three parameters Q, U, and V. : According to light intensity To segment the sample tissue surface, extract a region of interest that is A pixels wide from the center of the field of view; The averaged and normalized polarization state matrix is ​​obtained by averaging and normalizing the Stokes vectors of the A pixels. ; Adjust the fourth polarization controller according to the set target circular polarization state position, so that the polarization state matrix Approaching the target circularly polarized state position (0, 0, 1), when the polarization state matrix... When the target circularly polarized state position is reached, it is determined that stable circularly polarized light has been formed.

[0014] More preferably, in S4, based on the averaged normalized polarization state matrix... The deviation from the target circularly polarized state is dynamically adjusted by the fourth polarization controller until the sample light forms stable circularly polarized light on the sample tissue surface, including: Through polarization state matrix The direction of motion is determined by the deviation from the target's circularly polarized position coordinates, and the deflection angle of each ring plate of the fourth polarization controller is adjusted accordingly.

[0015] This application presents a PSOCT system and imaging method based on feedback-adjusted circular polarization. By dynamically adjusting the polarization state through real-time surface Stokes vector feedback, the polarization stability of the system is close to that of a dual-state input system while maintaining the simplicity of the single-state input system structure, which significantly improves the accuracy and repeatability of imaging. The polarization state is directly calculated using the system imaging preview data as a feedback signal, eliminating the need for additional hardware such as a polarization measuring instrument or optical power meter, without changing the original optical path, thus reducing system complexity and cost. The polarization adjustment process is embedded after imaging preview and before 3D scanning, and can be completed automatically, simplifying the operation steps, saving clinical time, and better meeting the high-efficiency needs of actual diagnosis and treatment scenarios. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a PSOCT system based on feedback-adjusted circular polarization, particularly an endoscopic PSOCT system, provided in Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of the structure of a PSOCT system based on feedback-adjusted circular polarization, especially a galvanometer PSOCT system, provided in Embodiment 2 of the present invention; Figure 3 A schematic flowchart of a PSOCT imaging method based on feedback-adjusted circular polarization provided by the present invention; Figure 4 This is a frame of OCT image acquired in this invention; Figure 5 This is a schematic diagram showing the polarization state matrix on the Poincaré sphere in this invention; Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] This invention provides a single-state input PSOCT system based on feedback-adjusted circular polarization, addressing the aforementioned challenges: it utilizes real-time surface Stokes vector feedback to dynamically adjust the circular polarization input without introducing additional measurement devices. The system dynamically compensates for polarization state fluctuations in the sample arm by analyzing the Stokes vector of backscattered light from the sample tissue surface, thus maintaining a stable circular polarization input. Depending on the scanning method of the sample tissue, it can be configured as an endoscopic OCT system with rotational retraction scanning or a galvanometer OCT system with reflection deflection scanning.

[0019] like Figure 1 As shown, taking endoscopic PSOCT as an example, the PSOCT system based on feedback-adjusted circular polarization provided by this invention includes: a swept-frequency light source, a first coupler, a sample arm, a reference arm, a second coupler, a polarization beam splitter, and a balanced detector. The light emitted from the swept-frequency light source is split by the first coupler and enters the sample arm and the reference arm; the beam splitting ratio is 9:1; the returning sample light and the reference arm light interfere with each other at the second coupler; the interference light is separated by the polarization beam splitter and converted into an electrical signal by the balanced detector; it also includes: A fourth polarization controller, disposed in the sample arm, is used to adjust the polarization state of the sample light irradiating the sample tissue; The feedback control module is used to acquire and analyze the electrical signal of the balanced detector in real time, calculate the polarization state of the sample surface and compare it with the target circular polarization, generate a control signal to drive the fourth polarization controller to dynamically adjust so that the sample light forms and maintains stable circular polarization on the sample tissue surface.

[0020] The light entering the reference arm (referred to as the reference light) is collimated and then emitted in parallel. It is then combined into 45° linearly polarized light by a 45° linear polarizer to ensure equal power in the two orthogonal polarization channels. After being focused by a focusing lens, it illuminates a reflecting mirror, which is fixed to a stepper motor. Together, they form an adjustable optical delay line used to adjust the optical path and match the sample arm. The light returning from the reflecting mirror enters polarization controller two through port 3 of the first circulator, and then enters the second coupler. The light entering the sample arm (referred to as the sample light) passes sequentially through polarization controller one, the second circulator, and polarization controller four. In the endoscopic PSOCT system, the sample light then illuminates the sample tissue through a rotation retraction driver and an imaging conduit. like Figure 2 As shown, in the galvanometer PSOCT system, the sample light is collimated and emitted as parallel light, then sequentially passes through galvanometer X, galvanometer Y, and focusing lens to illuminate the sample tissue. Galvanometer X and Y control the scanning of the light in the X and Y directions, respectively. When the sample light illuminates the tissue, the scattered light carrying tissue depth information returns along the original path of the sample arm, passes through the circulator, and enters polarization controller three to be adjusted to 45° linear polarization. At the second coupler, it interferes with the reference light, splitting the interference light signal into two beams. These beams then enter polarization beam splitter one and polarization beam splitter two, respectively, and are separated into orthogonal horizontal component H and vertical component V. These components are received by two balanced detectors for photoelectric conversion, forming two interference electrical signals for data acquisition.

[0021] Furthermore, a first polarization controller is provided in the sample arm after the first coupler splits the beam. The first polarization controller is set between the first coupler and the second circulator to maximize the output optical power of the second circulator. A second polarization controller is provided between the second coupler and the first circulator; the second polarization controller is used to maximize the interference amplitude of the two interference channels; A third polarization controller is provided between the second coupler and the second circulator, which is used to maximize the contrast between the two orthogonal interference channels.

[0022] It should be noted that the first, second, and third polarization controllers only need to be adjusted during the initial system setup. Polarization controller four is used to control the sample light to be circularly polarized when it irradiates the sample tissue. Due to the influence of fiber bending or swaying during use, it needs to be adjusted every time it is used for imaging. A ring-shaped polarization controller or a squeeze-type polarization controller can be used.

[0023] Preferably, the fourth polarization controller is a motor-driven annular polarization controller. The feedback control module controls the rotation angle of the motor to change the stress birefringence of the optical fiber in the annular polarization controller, thereby achieving fine adjustment of the polarization state.

[0024] The ring polarization controller has a three-ring structure, which is equivalent to a λ / 4 waveplate, a λ / 2 waveplate, and a λ / 4 waveplate in sequence. The feedback control module controls the deflection angle of the three rings independently to make the polarization state of the sample surface approach the target circular polarization.

[0025] After the system is built and the polarization controller is initially adjusted, the system is calibrated and can begin birefringence imaging. In actual use, most of the optical fibers in the optical path remain stable, except for the single-mode fiber connecting the sample arm to the main system and the probe (from the output port of the second circulator to the imaging probe; this section of fiber is referred to as the "probe single-mode fiber"). When the probe is moved or adjusted to position the imaging target, this section of fiber is easily disturbed, thus changing the preset circular polarization input, leading to inconsistent and inaccurate birefringence measurement results. To solve this problem, this invention provides a feedback mechanism based on surface Stokes vectors: the polarization state of the probe beam is inferred in real time using the backscattered light from the sample tissue surface, and the polarization controller is adjusted based on the detected polarization state to achieve circular polarization stabilization. The principle behind this method is as follows: Assuming that the reflected signal from the sample tissue surface is minimally affected by tissue-induced birefringence and can retain the polarization state of the incident beam, the "detecting single-mode fiber" can be modeled as an effective virtual layer above the sample tissue. When the returned sample light is output from the second circulator and detected, the polarization change caused by the "detecting single-mode fiber" can be visualized on the Poincaré sphere using the surface reflection Stokes vector.

[0026] The overall process of the system based on surface Stokes vector feedback adjustment is as follows: After the system completes initialization, OCT image preview is enabled to determine the region of interest (ROI) for imaging, and then polarization state feedback adjustment is performed. This is mainly because after the ROI is determined by preview, only the ROI is detected for a period of time. That is, the "probing single-mode fiber" can remain relatively fixed for a period of time. Therefore, it can be assumed that the fiber will not change its polarization state due to bending during the imaging process within this period of time, or the change is small and acceptable. After completing the polarization state feedback adjustment, three-dimensional scanning PSOCT imaging is performed.

[0027] This invention also provides a PSOCT imaging method based on feedback-adjusted circular polarization, applied to the aforementioned PSOCT system based on feedback-adjusted circular polarization; comprising the following steps: S1. Adjust the probe to acquire images of the region of interest in the sample tissue; S2. Based on the region of interest, perform image segmentation to identify the surface of the sample tissue; S3. Select several pixels at the center of the sample tissue surface, calculate their surface Stokes vectors and normalize them to obtain the average normalized polarization state matrix. ; S4. Based on the averaged normalized polarization state matrix The deviation from the target circular polarization state is dynamically adjusted by the fourth polarization controller until the sample light forms stable circular polarization light on the sample tissue surface; S5. Using the generated circularly polarized light, perform three-dimensional polarization-sensitive optical coherence tomography imaging on the region of interest.

[0028] More preferably, in S1, adjusting the probe to acquire images of the region of interest in the sample tissue includes: After completing the initial calibration, preview the image using the OCT image preview mode. Move the imaging probe to change the position of the beam illumination. After determining the region of interest of the sample tissue, stop moving the probe and acquire the image. After determining the region of interest, the probe position and orientation must be kept stable.

[0029] More preferably, in S2, image segmentation is performed on the image of the region of interest to identify the sample tissue surface, including: preprocessing the acquired original H-channel data and V-channel data of two orthogonal polarization states, and then performing a Fourier transform to convert them into H-channel Fourier domain complex signals. and V-channel Fourier domain complex signal The Stokes vectors I, Q, U, and V are constructed using the following formula: Where θ is the phase difference between the H and V channels. yes The conjugate of complex numbers, Represents the imaginary part of a complex number. The real part of the complex number is represented by Q and U, which describe the linearly polarized components in the x and y directions, respectively. V describes the circularly polarized component of light. 2 =Q 2 +U 2 +V 2 , I represents the light intensity envelope, indicating the total light intensity of each pixel. The sample tissue surface is segmented based on the light intensity envelope.

[0030] The sample tissue surface is determined based on the total light intensity and a preset light intensity ratio threshold. The preset light intensity ratio threshold is used to segment the sample tissue surface in the OCT structural image represented by the total light intensity. The preset light intensity ratio threshold η < 1, for example, η = 0.95. An intensity threshold is obtained by multiplying the maximum light intensity on an Ascan data point by the ratio threshold η. The first pixel on an Ascan data point from near to far that exceeds this intensity threshold is considered the sample tissue surface on that Ascan data point.

[0031] The above processing is performed on all Ascan data of the acquired images, and the collection of sample tissue surfaces on all Ascan data is regarded as the sample tissue surface.

[0032] Further preferably, in S3, several pixels adjacent to the Ascan at the center of the sample tissue surface are selected, their surface Stokes vectors are calculated and normalized to obtain the average normalized polarization state matrix. ,include: The Stokes vectors I, Q, U, and V are normalized, and then a polarization state matrix that can characterize the polarization state of each pixel is constructed using the three parameters Q, U, and V. : According to light intensity To segment the sample tissue surface, extract a region of interest that is A pixels wide from the center of the field of view; like Figure 4 As shown, 10 sample tissue surface pixels from the center of a frame of image are selected, represented by red line segments. The Stokes vectors of these 10 pixels are averaged and normalized to improve noise resistance. The averaged normalized polarization state matrix... It can be displayed on the Poincaré ball.

[0033] The averaged and normalized polarization state matrix is ​​obtained by averaging and normalizing the Stokes vectors of the A pixels. ; Adjust the fourth polarization controller according to the set target circular polarization state position, so that the polarization state matrix Approaching the target circularly polarized state position (0, 0, 1), when the polarization state matrix... Upon reaching the target circularly polarized state position, it is determined that stable circularly polarized light has been formed. For example... Figure 5 As shown, the blue dots represent the normalized polarization state matrix of the selected A points, and the red dots represent the average normalized polarization state matrix of these A points. .

[0034] Further preferably, based on the averaged normalized polarization state matrix The deviation from the target circularly polarized state is dynamically adjusted by the fourth polarization controller until the sample light forms stable circularly polarized light on the sample tissue surface, including: A fourth polarization controller is driven by a motor, and the winding state of the optical fiber in the ring polarization controller is determined according to the relationship between the winding radius and the number of windings of the ring polarization controller. Through polarization state matrix The direction of motion is determined by the deviation from the target circularly polarized position coordinates, and the deflection angle of each ring is adjusted accordingly.

[0035] After visualizing the Stokes vector on the Poincaré sphere, the polarization state matrix can be used to... The deviation from the target's circularly polarized position coordinates is used to provide feedback for adjusting the fourth polarization controller. During imaging, the probe position and orientation need to be adjusted to determine the imaging ROI. Fiber disturbances generated during probe adjustment can lead to… After determining the imaging ROI and moving away from the North Pole (i.e., the target's circular polarization state position), keep the "probe single-mode fiber" stable and adjust polarization controller four to... Approaching (0, 0, 1), the polarization controller can be adjusted manually or by a motor (if a compression-type polarization controller is used, the pressure and angle of the compression are adjusted). In this embodiment, a motor-controlled annular polarization controller is used. The motor's adjustment range is 0~180°, with an accuracy of 1.8°. The control accuracy can be refined to 0.1125° through a 16x subdivision. The relationship between the annular polarization controller's radius of rotation and the number of rotations is as follows: Where R is the radius of circumference. It is a constant in single-mode fiber. =0.133, Where N is the fiber cladding radius, N is the number of turns, and m is the wave division factor, for example, when m=4, it is equivalent to a 1 / 4 waveplate.

[0036] Taking a three-loop polarization controller as an example, a three-loop polarization controller is equivalent to , , Three cascaded waveplates are used, so the m values ​​of the three rings are 4, 2, and 4, respectively, and the number of turns is set to 2, 4, and 2. In this case, the three rings have the same circumference. The cladding diameter of the optical fiber used is 125 μm, and the wavelength is 1.31 μm. It can be calculated that the circumference of the three rings is about 20 mm. The optical fiber cannot be twisted, crossed, or overlapped during the winding process.

[0037] The first and third rings are Waveplates primarily produce displacement in the vertical direction (meridian direction), second ring. Waveplates primarily produce displacement in the horizontal direction (parallel to the equator), through... The direction of motion is determined by the deviation from the North Pole coordinates, and the deflection angles of the three ring plates are adjusted accordingly until the direction is correct. Adjust it to coincide with the North Pole.

[0038] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A PSOCT system based on feedback adjustment of circular polarization, comprising: The swept source, the first coupler, the sample arm, the reference arm, the second coupler, the polarization beam splitter and the balanced detector, the light emitted by the swept source is split into the sample arm and the reference arm by the first coupler; the returned sample light and the reference arm light interfere at the second coupler; The interference light is separated by the polarization beam splitter and converted into an electrical signal by the balanced detector; characterized in that it further comprises: A fourth polarization controller is arranged in the sample arm for adjusting the polarization state of the sample light irradiating the sample tissue; A feedback control module is used to calculate the sample surface polarization state and compare it with the target circular polarization to generate a control signal to drive the fourth polarization controller to dynamically adjust so as to form and maintain stable circularly polarized light on the sample tissue surface.

2. The feedback-adjusted circular polarization based PSOCT system of claim 1, wherein, A first polarization controller is arranged in the sample arm after the first coupler splits, and the first polarization controller is arranged between the first coupler and the second circulator to maximize the output optical power of the second circulator; A second polarization controller is arranged between the second coupler and the first circulator; the second polarization controller is used to maximize the interference amplitude of the two interference channels; A third polarization controller is arranged between the second coupler and the second circulator, and the third polarization controller is used to maximize the contrast between the two orthogonal interference channels.

3. The feedback-adjusted circular polarization based PSOCT system of claim 1, wherein, The fourth polarization controller is a motor-driven ring polarization controller, and the feedback control module changes the stress birefringence of the optical fiber in the ring polarization controller by controlling the rotation angle of the motor, thereby achieving fine adjustment of the polarization state.

4. The feedback-adjusted circular polarization based PSOCT system of claim 3, wherein, The ring polarization controller is a three-ring structure, which is equivalent to a λ / 4 waveplate, a λ / 2 waveplate and a λ / 4 waveplate in turn; the feedback control module approaches the target circular polarization of the sample surface polarization state by independently controlling the deflection angles of the three rings.

5. A method of PSOCT imaging based on feedback adjustment of circular polarization, characterized in that, The PSOCT system based on feedback adjustment of circular polarization is applied to any one of the above claims 1-4; comprising the following steps: S1, adjusting the probe to image the region of interest of the sample tissue; S2, image segmentation according to the region of interest to identify the sample tissue surface; S3, selecting several pixels in the center of the surface of the sample tissue, calculating the surface Stokes vector and normalizing to obtain the average normalized polarization state matrix ; S4, based on the averaged normalized polarization state matrix deviation from the target circular polarization state, dynamically adjusting the fourth polarization controller until the sample light forms a stable circularly polarized light at the sample tissue surface; S5, using the formed circularly polarized light to perform three-dimensional polarization-sensitive optical coherence tomography scanning imaging on the region of interest.

6. The feedback-adjusted circularly polarized PSOCT imaging method based on feedback regulation of claim 5, wherein, In S1, adjusting the probe to image the region of interest of the sample tissue includes: After completing the initialization calibration, previewing is performed in the OCT image preview mode, the imaging probe is moved to change the position of the light beam irradiation, the probe is stopped moving and the image is collected after the region of interest of the sample tissue is determined, and the polarization state is adjusted based on the collected image.

7. The feedback-adjusted circularly polarized PSOCT imaging method based on feedback regulation of claim 5, wherein, In S2, image segmentation according to the region of interest to identify the sample tissue surface includes: The two original polarization state H channel data and V channel data collected are preprocessed, and after preprocessing, Fourier transform is performed to convert into H channel Fourier domain complex signal and V channel Fourier domain complex signal The Stokes vectors I, Q, U, V are constructed by using the following formula: where θ is the phase difference between the H and V channels, is the conjugate complex of represents the imaginary part of a complex number, represents the real part of a complex number; Q and U describe the linearly polarized components in the x and y directions, respectively, V is the circularly polarized component describing the light, and I 2 = Q 2 + U 2 + V 2 , I is the light intensity envelope, which represents the total light intensity of each pixel point, and the sample tissue surface is segmented according to the light intensity envelope.

8. The feedback-adjusted circularly polarized PSOCT imaging method of claim 7, wherein, When the sample tissue surface is segmented according to the light intensity envelope, the following steps are included: Multiply the light intensity maximum value on each Ascan data by a preset light intensity ratio threshold η to obtain an intensity threshold, and regard the first pixel from the proximal end to the distal end on the Ascan data that is greater than the intensity threshold as the sample tissue surface on the Ascan data.

9. The feedback-adjusted circularly polarized PSOCT imaging method based on feedback regulation of claim 5, wherein, In S3, several pixels in the center of the surface of the sample tissue are selected, the surface Stokes vector is calculated and normalized, and an average normalized polarization state matrix is obtained , comprising: After the Stokes vector I, Q, U, V is normalized, a polarization state matrix is constructed by using the three parameters Q, U, V to represent the polarization state of each pixel point : According to the light intensity to divide the sample tissue surface, extract the region of interest field center A pixel wide region; averaging and normalizing the A number of pixel Stokes vectors to obtain an averaged normalized polarization state matrix ; The fourth polarization controller is adjusted according to the set target circular polarization state position, so that the polarization state matrix approaches the target circular polarization state position (0, 0, 1), and when the polarization state matrix reaches the target circular polarization state position, it is judged that stable circularly polarized light is formed.

10. The feedback-adjusted circularly polarized PSOCT imaging method based on feedback regulation of claim 5, wherein, In S4, based on the averaged normalized polarization state matrix deviation from the target circular polarization state, dynamically adjusting the fourth polarization controller until the sample light forms a stable circularly polarized light at the sample tissue surface comprises: By the polarization state matrix The direction of movement is determined by the deviation from the target circular polarization state position coordinate, and the deflection angle of each ring piece of the fourth polarization controller is adjusted.

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