Multi-contrast jones matrix ophthalmic optical coherence tomography imaging system based on single balanced detector

Abstract

The application discloses a kind of based on single-balanced detector's multiple contrast Jones matrix OCT imaging system, belong to optical imaging technical field.Sweeping laser light is divided into two beams by 1*2 broadband fiber coupler, one enters sample arm polarization delay module, generates two orthogonal sample lights of equal power, optical path difference is ξ, detects biological tissue, and sample returns the backscattering light transmission to 50 / 50 broadband fiber coupler by three-port fiber ring;With another into reference arm polarization delay module, generated two orthogonal reference lights of equal power, optical path difference is 2ξ, after interference, it is collected by a balanced detector.High-speed data acquisition card directly processes interference signal to realize real-time imaging;Another channel acquires k-clock signal, improves the detection accuracy of system by calculating correlation to system phase compensation.The application is suitable for medical fields and the like, to simplify system structure, reduce cost, save data processing time.

Description

TECHNICAL FIELD

[0001] The application relates to a single-balanced detector-based multi-contrast Jones matrix OCT imaging system and belongs to the technical field of optical imaging. BACKGROUND

[0002] Optical coherence tomography (OCT) is a non-invasive, label-free and depth-resolved imaging technique that can provide three-dimensional structural information of a sample under test. In the past 30 years, OCT has been widely used in a series of medical fields, including ophthalmology, dermatology, oncology, etc. In addition to standard OCT that only provides sample morphological information, various functional extensions of OCT are being developed, including OCT angiography (OCTA) and polarization-sensitive OCT (PS-OCT).

[0003] OCTA can realize three-dimensional microvascular network imaging without the need for exogenous contrast agents. When moving particles (mainly red blood cells) flow through the OCT imaging beam, local fluctuations will be caused in the repeatedly acquired cross-sectional images. By comparing the fluctuation amplitudes of the OCT signals at the same position at different times, the vascular distribution information, including the vascular diameter and the vascular density, can be extracted from the tissue, thereby improving the diagnosis rate of pathological diseases. As another functional extension of OCT, PS-OCT can extract the polarization properties of biological tissues, such as birefringence, bidirectional attenuation and optical axis direction angle. These properties are often related to the microstructure and even the ultrastructure of the sample, and can be used to detect changes in the structure of diseased tissues, showing unique advantages in the biomedical field. More importantly, the combination of PS-OCT and OCTA can effectively improve the vascular connectivity and reveal more blood vessels by eliminating polarization artifacts.

[0004] In PS-OCT detection, to obtain the Jones matrix, two orthogonally polarized lights are usually used to probe the sample, and then the backscattered light returned from the sample interferes with a reference light, and two balanced detectors are used to detect the two orthogonal components of the interference signal. A CUDA algorithm based on GPU is used for parallel operation of the interference signal to realize real-time scattering intensity imaging. After Fourier transform is performed on the two interference signals obtained, the Jones matrix carrying the polarization properties of the sample and the system is obtained. Then, the intensity image, the polarization image (including the birefringence, linear attenuation and polarization uniformity image) and the blood vessel image are calculated.

[0005] Multi-contrast OCT systems can provide valuable multi-dimensional images of biological tissues. For example, intensity images can reflect the structural information of the sample; birefringence can reflect the arrangement order of fiber structures such as proteins; polarization uniformity can reflect the distribution of pigments; and angiography can reflect the vascular distribution of living tissues. These provide reliable methods for tissue characterization and classification. However, traditional systems still have the following problems:

[0006] First, unlike standard OCT imaging systems, traditional multi-contrast Jones matrix OCT imaging systems use two balanced detectors, one for collecting two orthogonal components of the interference spectrum to infer the polarization information of the sample, such as birefringence, linear attenuation, and polarization uniformity, which increases the cost and structural complexity of the system.

[0007] Second, to obtain complete polarization information, it is necessary to perform Fourier transform on the two collected interference spectra separately, which increases the calculation time of subsequent data processing.

[0008] Third, because the FPGA on the high-speed data acquisition card can only perform parallel operations on the interference signal collected by channel A, in order to achieve real-time imaging of sample detection, it is necessary to use the GPU-based CUDA algorithm to parallel process the two channels collected by the high-speed data acquisition card, which greatly increases the system cost and computational complexity.

[0009] Fourth, while multi-contrast Jones matrix OCT systems using swept lasers offer fast imaging speeds and deep imaging depths, they suffer from temporal jitter, which can cause severe phase instability. This further impacts the accuracy of complex- and phase-based OCTA techniques for vascular imaging and the measurement of sample birefringence. While a series of hardware-based phase compensation methods, such as Mach-Zehnder interferometers and fiber Bragg gratings, have achieved promising results, these approaches either increase system cost or complexity.

[0010] The above-mentioned problems of high cost, high complexity and high computing time have seriously restricted the promotion of commercialization and clinical application of multi-contrast Jones matrix OCT imaging systems. Summary of the Invention

[0011] To address the above problems, the present invention discloses a multi-contrast Jones matrix OCT imaging system based on a single balanced detector, which aims to reduce system cost and structural complexity; improve the phase stability of the system; and achieve higher-precision detection of blood vessels and polarization information.

[0012] The purpose of the present invention is achieved through the following technical solutions:

[0013] The present invention discloses a multi-contrast Jones matrix OCT imaging system based on a single balanced detector, comprising a swept laser, a 1*2 broadband fiber coupler, a reference arm polarization delay module, a sample arm polarization delay module, a three-channel broadband fiber circulator, a probe scanning module, a 50 / 50 broadband fiber coupler, a balanced detector, a high-speed data acquisition card, a control module, and a data processing module.

[0014] The system adopts a semi-fiber structure to improve system stability and noise immunity. The input port of a 1x2 broadband fiber coupler is connected to a swept laser, while its two output ports are connected to the reference arm polarization delay module and the sample arm polarization delay module, respectively, in a free-space configuration via fiber collimators. The output port of the reference arm polarization delay module is directly connected to one of the input ports of a 50 / 50 broadband fiber coupler via a fiber collimator, where it interferes with the sample backscattered light. Port 1 of a three-channel broadband fiber circulator is connected to the sample arm polarization delay module via a fiber collimator, while port 2 is connected to the probe scanning module in the free-space configuration. Port 3 is connected to the other input port of the 50 / 50 broadband fiber coupler via a fiber flange. The two input ports of the balanced detector are connected to the two output ports of the 50 / 50 broadband fiber coupler, respectively. The differential output port is connected to Channel A of a high-speed data acquisition card via an RF cable. Furthermore, the k-clock output port of the swept laser is split into two by an RF cable, connected to the clock signal channel and Channel B of the high-speed data acquisition card, respectively.

[0015] The control module is used to provide synchronization signals for the acquisition system and generate analog voltage waveforms for the scanning system.

[0016] The beam emitted by the swept laser is divided into two beams by a 1*2 fiber coupler and enters the sample arm polarization delay module and the reference arm polarization delay module respectively.

[0017] The sample arm polarization delay module adopts a double wave plate structure or a double Dove prism structure to split the input 45° linearly polarized light into two probe lights with mutually perpendicular polarization states, equal power, and an optical path difference of ξ, and is transmitted to the probe scanning module by a broadband fiber circulator.

[0018] The probe scanning module includes a scanning system for realizing one-dimensional and two-dimensional scanning imaging of the detection beam; and also includes a confocal microscope for focusing the detection beam on the sample to be tested and collecting the backscattered signal returned by the sample.

[0019] The reference arm polarization delay module adopts a double wave plate structure or a double Dove prism structure to split the input 45° linearly polarized light into two reference beams with perpendicular polarization states, equal power and an optical path difference of 2ξ, and transmit them to the 50 / 50 broadband coupler.

[0020] The backscattered light returned by the sample interferes with the reference light generated by the reference arm polarization delay module at a 50 / 50 coupler and is split into two beams of equal power, which are then introduced into the two input ports of a balanced detector for differential detection. The differential voltage signal is collected by a high-speed data acquisition card and transmitted to the data processing module. The interference spectrum is directly processed in parallel by the FPGA on the high-speed data acquisition card, including DC term removal, dispersion compensation, zero padding, and Fourier transform, thereby achieving real-time display of the scattering intensity image; the Jones component J, which is a mixture of the system and sample polarization characteristics, can be obtained by Fourier transforming the measured interference spectrum. 11 、J 12 、J 21 、J 22 :

[0021] I(Δz)∝J 11 δ(z-Δz)+J 12 δ(z-(Δz+ξ))+J 21 δ(z-(Δz+2ξ)+J 22 δ(z-(Δz+3ξ)

[0022] To achieve high-precision polarization information measurement and vascular distribution measurement, phase compensation is required for the time jitter of the swept laser. On the one hand, the clock channel of the high-speed data acquisition card is used to receive the k-clock signal from the swept laser and use it as an external clock signal to acquire OCT signals. On the other hand, while detection channel A is used to acquire OCT signals, detection channel B uses the internal clock signal to acquire the k-clock signal and calculates the maximum cross-correlation of the k-clock signal under each sweep.

[0023] Correlatin=Var(kclock(t1))*Var(kclock(t2))

[0024] Where kclock(t1) and kclock(t2) represent the k-clock signals collected at different sweep periods t1 and t2, respectively. The number of pixel offsets for each A-line in the OCT signal is then determined, and the OCT interferometer signal is shifted to achieve phase correction. The similarity matrix of the phase-compensated Jones matrix is ​​calculated, and the eigenvalue decomposition of the similarity matrix is ​​performed. The two eigenvalues ​​obtained are used to derive the local birefringence and linear attenuation of the sample. The two eigenvectors obtained are used to determine the optical axis angle. Furthermore, the Stokes vector converted from the Jones vector is used to determine polarization uniformity. By calculating the similarity between multiple repeated B-scan measurements, a vascular distribution image is obtained. In addition to obtaining cross-sectional images of the sample, including intensity images, birefringence images, linear attenuation images, polarization uniformity images, and vascular images, corresponding three-dimensional volumetric images and en face images obtained using the amplitude summation projection method are also obtained.

[0025] The working method of the single-balanced detector-based multi-contrast Jones matrix OCT imaging system disclosed by the application is as follows:

[0026] The low-coherence light emitted by the swept laser is divided into two beams of light via the 1*2 wideband fiber coupler, and enters the reference arm polarization delay module and the sample arm polarization delay module respectively, so as to obtain two beams of probe light output by the sample arm polarization delay module, which are orthogonal in polarization state, equal in power, and have an optical path difference of ξ, and two beams of reference light output by the reference arm polarization delay module, which are orthogonal in polarization state, equal in power, and have an optical path difference of 2ξ. The three-channel wideband fiber circulator inputs the probe light to the probe scanning module to converge on the sample to be measured, and transmits the backscattered light returned by the sample to the 50 / 50 wideband fiber coupler. The two beams of reference light are directly transmitted to the 50 / 50 wideband fiber coupler, interfered with the backscattered light returned by the sample, and equally divided into two paths at equal power, and input to the two input ports of the balanced detector for differential detection. The high-speed data acquisition card performs analog-to-digital conversion on the differential voltage signal output by the balanced detector and uploads it to the data processing module, so as to further obtain the intensity information, polarization information and blood vessel distribution information of the sample.

[0027] Advantages:

[0028] 1. The single-balanced detector-based multi-contrast Jones matrix OCT imaging system disclosed by the application first sets up a polarization delay module similar to that in the sample arm in the reference arm, so that two beams of reference light having perpendicular polarization states and a certain optical path difference are generated, so as to realize twice depth multiplexing in the OCT image. Then the two beams of reference light are interfered with the backscattered light from the sample at the 50 / 50 coupler, and the output ports thereof are directly connected to the two input ports of a balanced detector, without the need to pass through other devices in the polarization-sensitive detection unit, so that the system structure can be significantly simplified and the system cost can be reduced.

[0029] 2. The single-balanced detector-based multi-contrast Jones matrix OCT imaging system disclosed by the application can obtain a 2*2 Jones matrix by performing Fourier transform on only one obtained interference spectrum signal, so as to further obtain the intensity, polarization and blood vessel information of the sample, and significantly improve the data processing efficiency and operation speed in the later stage.

[0030] 3. The single-balanced detector-based multi-contrast Jones matrix OCT imaging system disclosed by the application adopts the FPGA supported by the high-speed data acquisition card to realize real-time imaging by parallel processing of the interference signals collected by channel A, so as to significantly reduce the cost and complexity of the system.

[0031] 4. The single-balanced detector-based multi-contrast Jones matrix OCT imaging system disclosed in the application, while channel A of the high-speed data acquisition card collects the OCT signal, channel B continuously collects the k-clock signal with an internal clock, and the maximum cross-correlation between them is calculated to obtain the misalignment point number of the collected signal in the wave number domain, and the OCT interference signal is translated to complete phase correction, thereby obtaining high-precision birefringence and blood vessel distribution information of the sample. Without increasing the cost and complexity of the system structure, a phase-stable multi-contrast Jones matrix OCT system is realized. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of the single-balanced detector-based multi-contrast Jones matrix OCT imaging system.

[0033] Among them:

[0034] 1 - frequency laser, 2 - 1*2 10 / 90 wideband fiber coupler, 3 - reference arm polarization delay module, 4 - sample arm polarization delay module, 5 - three-channel wideband circulator, 6 - 50 / 50 wideband fiber coupler, 7 - balanced detector, 8 - probe scanning module, 9 - high-speed data acquisition card, 10 - control module, 11 - data processing module.

[0035] Figure 2 It is an embodiment schematic diagram of the single-balanced detector-based multi-contrast Jones matrix OCT imaging system.

[0036] Among them:

[0037] 1 - frequency laser, 2 - 1*2 10 / 90 wideband fiber coupler, 3 - reference arm polarization delay module, 4 - sample arm polarization delay module, 5 - three-channel wideband circulator, 6 - 50 / 50 wideband fiber coupler, 7 - balanced detector, 8 - probe scanning module, 9 - high-speed data acquisition card, 10 - control module, 11 - data processing module, 31 - plane mirror, 32 - wideband quarter-wave plate, 33 - wideband polarization beam splitter prism, 34 - linear polarizer, 35 - fiber collimator, 41 - plane mirror, 42 - wideband quarter-wave plate, 43 - wideband polarization beam splitter prism, 44 - linear polarizer, 45 - fiber collimator, 81 - fiber collimator, 82 - scanning galvanometer, 83 - imaging lens, 84 - sample.

[0038] Figure 3 It is the simultaneously collected interference signal and k-clock signal;

[0039] Figure 4 It is the misalignment point distribution of the collected signal under different frequency sweeping periods;

[0040] Figure 5are the interference signal and k-clock signal after phase correction. DETAILED DESCRIPTION

[0041] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. The technical problems solved by the technical solution of the present invention and the beneficial effects thereof are also described. It should be noted that the described embodiments are only intended to facilitate understanding of the present invention and do not serve to limit the present invention in any way.

[0042] like Figure 2 As shown, the multi-contrast Jones matrix OCT system based on a single balanced detector disclosed in this embodiment includes a swept laser 1, a 1*2 10 / 90 broadband fiber coupler 2, a reference arm polarization delay module 3, a sample arm polarization delay module 4, a three-channel broadband circulator 5, a 50 / 50 broadband fiber coupler 6, a balanced detector 7, a probe scanning module 8, a high-speed data acquisition card 9, a control module 10, and a data processing module 11.

[0043] The reference arm polarization delay module 3 includes a plane mirror 31 , a broadband quarter-wave plate 32 , a broadband polarization beam splitter prism 33 , a linear polarizer 34 , and a fiber collimator 35 .

[0044] The sample arm polarization delay module 4 includes: a plane mirror 41, a broadband quarter-wave plate 42, a broadband polarization beam splitter prism 43, a linear polarizer 44, and a fiber collimator 45; the probe scanning module 8 includes: a fiber collimator 81, a scanning galvanometer 82, an imaging lens 83, and a sample 84.

[0045] A micro-electromechanical system type swept laser is used to generate low-coherence light, TTL trigger signal and k-clock signal.

[0046] A 1*2 10 / 90 broadband fiber coupler is used to connect the swept laser, the reference arm polarization delay module, and the sample arm polarization delay module and split the low-coherence light into two beams, which are transmitted to the reference arm polarization delay module and the sample arm polarization delay module respectively.

[0047] Reference arm polarization delay module 3 adopts a double wave plate structure including plane mirror 31, wideband quarter wave plate 32, wideband polarization beam splitter prism 33, linear polarizer 34, fiber collimator 35. Linear polarizer 34 is used to generate 45° linearly polarized light; polarization beam splitter prism 33 is used to split 45° linearly polarized light into two orthogonal components; wideband quarter wave plate 321 is used to rotate the polarization direction of P light by 90° to become S light; wideband quarter wave plate 322 is used to rotate the polarization direction of S light by 90° to become P light; plane mirrors 311 and 312 are used to return the light to the original path, and the relative positions of the two plane mirrors are used to generate an optical path difference of 2ξ between the two polarized lights; fiber collimator 351 is used to collimate the light beam, and fiber collimator 352 is used to couple the light beam into the optical fiber; the use of the fiber collimator can effectively reduce the loss of optical signals.

[0048] Sample arm polarization delay module 4 adopts a double wave plate structure including: plane mirror 41, wideband quarter wave plate 42, wideband polarization beam splitter prism 43, linear polarizer 44, fiber collimator 45; linear polarizer 44 is used to generate 45° linearly polarized light; polarization beam splitter prism 43 is used to split 45° linearly polarized light into two orthogonal components; wideband quarter wave plate 421 is used to rotate the polarization direction of P light by 90° to become S light; wideband quarter wave plate 422 is used to rotate the polarization direction of S light by 90° to become P light; plane mirrors 411 and 412 are used to return the light to the original path, and the relative positions of the two plane mirrors are used to generate an optical path difference of 2ξ between the two polarized lights; fiber collimator 451 is used to collimate the light beam, and fiber collimator 452 is used to couple the light beam into the optical fiber; the use of the fiber collimator can effectively reduce the loss of optical signals.

[0049] Three-channel wideband circulator 5 is used to connect sample arm polarization delay module 4, probe scanning module 8 and 50 / 50 wideband fiber coupler 6. Two beams of orthogonal sample light enter the a port of circulator 5, and the b port outputs to probe scanning module 8, and backscattered light is transmitted to wideband fiber coupler from the c port;

[0050] 50 / 50 wideband fiber coupler 6 is used to synthesize backscattered light and reference light, and to equally divide the synthesized light into two paths to the two input ports of balanced detector 7.

[0051] The probe scanning module includes fiber collimator 81, scanning galvanometer 82, imaging lens 83 and sample 84. Fiber collimator 81 is used to collimate the light beam and couple the backscattered light into the optical fiber; scanning galvanometer 82 is used for one-dimensional and two-dimensional scanning of the probe light beam, thereby realizing two-dimensional and three-dimensional imaging of the sample; imaging lens 83 is used to converge the probe light beam on the sample to be measured on the one hand, and to collect the returned backscattered signal on the other hand;

[0052] The balanced detector 7 is used to differentially detect the synthesized light output by the optical fiber coupler 6 , and output the differential signal from the RF end into the detection channel A of the high-speed data acquisition card 9 .

[0053] The high-speed data acquisition card 9's detection channel A is used for analog-to-digital conversion of differential signals, detection channel B is used for analog-to-digital conversion of k-clock signals, and the clock channel is used to receive the k-clock signal as an external clock signal to acquire differential signals. It also receives the frame trigger signal generated by the control module 10 to synchronize the system's acquired signals.

[0054] Control module 10 includes an NI PCIE6323 data acquisition device, which drives the scanning galvanometer, controlling the scanning mode, scanning range, scanning speed, and number of repetitions. It also receives a TTL trigger signal from the swept laser 1 as a digital signal source and generates a frame trigger signal that is transmitted to the high-speed data acquisition card 9 to synchronize the acquisition system.

[0055] Compared with the traditional multi-contrast Jones matrix OCT imaging system, this system based on a single balanced detector greatly simplifies the system structure and reduces the system cost.

[0056] The data processing module 11 is used to perform parallel interferometric spectral processing via the FPGA on the high-speed data acquisition card, significantly reducing system cost and computational complexity. Data processing includes DC removal, dispersion compensation, zero padding, and Fourier transform, enabling real-time display of the scattering intensity image. In particular, the Fourier transform of the measured interferometric spectrum yields the Jones component, a mixture of the system and sample polarization characteristics:

[0057] I(Δz)∝J 11 δ(z-Δz)+J 12 δ(z-(Δz+ξ))+J 21 δ(z-(Δz+2ξ)+J 22 δ(z-(Δz+3ξ)

[0058] Here J 11 、J 12 、J 21 、J 22 are the four components of the Jones matrix. This greatly improves the processing efficiency and computational speed of subsequent data. The obtained Jones components are coherently synthesized to obtain a scattering intensity image with enhanced sensitivity.

[0059] While channel A of the high-speed data acquisition card is collecting OCT signals, channel B is continuously collecting k-clock signals with an internal clock at a sampling rate of 1Gs / s. The k-clock signals and interference signals collected at different times are shown in the figure. Figure 3As shown in the figure, it can be seen that the wave number corresponding to the same sampling point index is different, that is, there is a laser phase instability phenomenon. By calculating the maximum cross-correlation of the k-clock signal under different sweep cycles,

[0060] Correlatin=Var(kclock(t1))*Var(kclock(t2))

[0061] Here, kclock(t1) and kclock(t2) represent the k-clock signals collected at different sweep cycles t1 and t2 respectively. Then, the number of offset points of the collected signals at different sweep cycles is obtained as follows: Figure 4 As shown in the figure, the OCT interference signal is shifted according to the number of misalignment points to complete the phase correction. Figure 5 As shown, high-precision birefringence and vascular distribution information is obtained, and a phase-stable multi-contrast Jones matrix OCT system is realized without increasing the cost and structural complexity of the system.

[0062] The similarity matrix of the phase-compensated Jones matrix is ​​calculated, and the eigenvalue decomposition of the similarity matrix is ​​performed. The two eigenvalues ​​obtained can be used to deduce the sample's local birefringence and linear attenuation. The two eigenvectors obtained can be used to determine the optical axis angle. Furthermore, the Stokes vector converted from the Jones vector is used to obtain polarization uniformity. By calculating the similarity between multiple repeated B-scan measurements, a vascular distribution image can be obtained. In particular, in addition to obtaining cross-sectional images of the sample, including intensity images, birefringence images, linear attenuation images, polarization uniformity images, and vascular images, corresponding three-dimensional volumetric images and en face images obtained using the amplitude sum projection method can also be obtained.

[0063] The above specific description further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multi-contrast Jones matrix OCT imaging system based on a single balanced detector, characterized by: It includes a swept laser, a 1*2 broadband fiber coupler, a reference arm polarization delay module, a sample arm polarization delay module, a three-channel broadband fiber circulator, a probe scanning module, a 50 / 50 broadband fiber coupler, a balanced detector, a high-speed data acquisition card, a control module, and a data processing module. The system adopts a semi-fiber structure; The input port of the 1*2 broadband fiber coupler is connected to a frequency-sweeping laser, and the two output ports are connected to a reference arm polarization delay module and a sample arm polarization delay module of a free-space structure respectively through fiber collimators; The output port of the reference arm polarization delay module is directly connected to one of the input ports of a 50 / 50 broadband fiber coupler through a fiber collimator, and interferes with the sample backscattered light at the coupler; Port 1 of the three-channel broadband fiber circulator is connected to the sample arm polarization delay module through a fiber collimator, port 2 is connected to the probe scanning module of the free space structure, and port 3 is connected to the other input port of the 50 / 50 broadband fiber coupler through a fiber flange; The two input ports of the balanced detector are respectively connected to the two output ports of the 50 / 50 broadband fiber coupler, and the differential output port is connected to channel A of the high-speed data acquisition card through a radio frequency line; The k-clock output port of the frequency sweep laser is divided into two by a radio frequency line and connected to the clock signal channel and channel B of the high-speed data acquisition card respectively; The sample arm polarization delay module adopts a double wave plate structure or a double Dove prism structure to split the input 45° linearly polarized light into two probe beams with mutually perpendicular polarization states, equal power, and an optical path difference of 2ξ. The two beams are then transmitted to the probe scanning module by a broadband fiber circulator. The reference arm polarization delay module adopts a double wave plate structure or a double Dove prism structure to split the input 45° linearly polarized light into two reference beams with perpendicular polarization states, equal power and an optical path difference of 2ξ, and transmit them to the 50 / 50 broadband coupler.

2. The multi-contrast Jones matrix OCT imaging system based on a single balanced detector according to claim 1, characterized in that: The control module is used to provide synchronization signals for the acquisition system and generate analog voltage waveforms for the scanning system.

3. The multi-contrast Jones matrix OCT imaging system based on a single balanced detector according to claim 1, characterized in that: The beam emitted by the swept laser is divided into two beams by a 1*2 fiber coupler and enters the sample arm polarization delay module and the reference arm polarization delay module respectively.

4. The multi-contrast Jones matrix OCT imaging system based on a single balanced detector according to claim 1, characterized in that: The probe scanning module includes a scanning system for realizing one-dimensional and two-dimensional scanning imaging of the detection beam; and also includes a confocal microscope for focusing the detection beam on the sample to be tested and collecting the backscattered signal returned by the sample.

5. The multi-contrast Jones matrix OCT imaging system based on a single balanced detector according to claim 1, characterized in that: The backscattered light returned by the sample interferes with the reference light generated by the reference arm polarization delay module at a 50 / 50 coupler and is split into two beams with equal power. The two beams are then introduced into the two input ports of a balanced detector for differential detection. The differential voltage signal is collected by a high-speed data acquisition card and transmitted to the data processing module. The interference spectrum is directly processed in parallel by the FPGA on the high-speed data acquisition card, including DC removal, dispersion compensation, zero filling and Fourier transform, so as to realize real-time display of the scattering intensity image; the Jones component J after the mixed polarization characteristics of the system and sample can be obtained by Fourier transforming the measured interference spectrum. 11 、J 12 、J 21 、J 22 : I(Δz)∝J 11 δ(z-Δz)+J 12 δ(z-(Δz+ξ))+J 21 δ(z-(Δz+2ξ))+J 22 δ(z-(Δz+3ξ)) To achieve high-precision polarization information and vascular distribution measurements, phase compensation is required for the time jitter of the swept laser. On the one hand, the clock channel of the high-speed data acquisition card is used to receive the k-clock signal from the swept laser and use it as an external clock signal to acquire OCT signals. On the other hand, while detection channel A is used to acquire OCT signals, detection channel B uses the internal clock signal to acquire the k-clock signal and calculates the maximum cross-correlation of the k-clock signal under each sweep. Correlatin=Var(kclock(t1))*Var(kclock(t2)) Where kclock(t1) and kclock(t2) represent the k-clock signals collected at different sweep periods t1 and t2, respectively. The number of pixel misalignment points for each A-line in the OCT signal is then obtained, and the OCT interferometer signal is shifted to achieve phase correction. The similarity matrix of the phase-compensated Jones matrix is ​​calculated, and the eigenvalue decomposition of the similarity matrix is ​​performed. The local birefringence and linear attenuation of the sample can be deduced from the two eigenvalues ​​obtained; the optical axis direction angle can be obtained from the two eigenvectors obtained; further, the polarization uniformity is obtained by converting the Jones vector into the Stokes vector; by calculating the similarity between multiple repeated B-scan measurements, the vascular distribution image can be obtained; in addition to obtaining the cross-sectional image of the sample, including the intensity image, birefringence image, linear attenuation image, polarization uniformity image and vascular image, the corresponding three-dimensional volume image and the frontal image obtained by the amplitude sum projection method can also be obtained.

6. The multi-contrast Jones matrix OCT imaging system based on a single balanced detector according to claim 1, characterized in that: The working method is, Low-coherence light emitted by a frequency-sweeping laser is split into two beams via the 1*2 broadband fiber coupler, which then enter the reference arm polarization delay module and the sample arm polarization delay module, respectively, to obtain two probe beams with orthogonal polarization states, equal power, and an optical path difference of 2ξ output by the sample arm polarization delay module, and two reference beams with orthogonal polarization states, equal power, and an optical path difference of 2ξ output by the reference arm polarization delay module. A three-channel broadband fiber circulator inputs the probe light into the probe scanning module, where it converges onto the sample to be tested, and transmits the backscattered light returned by the sample to a 50 / 50 broadband fiber coupler. The two reference beams are directly transmitted to the 50 / 50 broadband fiber coupler to interfere with the backscattered light returned by the sample and are equally split into two paths with equal power, respectively input into the two input ports of a balanced detector for differential detection. A high-speed data acquisition card performs analog-to-digital conversion on the differential voltage signal output by the balanced detector and uploads it to a data processing module, thereby further obtaining intensity information, polarization information, and vascular distribution information of the sample.

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