A full polarization fmcw lidar system and measurement method

Abstract

The application discloses a kind of full polarization FMCW laser radar systems and measuring methods, system includes sweep laser source, first optical coupler, polarization state generation module, optical circulator, optical transceiver and scanning module, polarization state analysis module, second optical coupler, photoelectric balance detector and signal acquisition and processing module;Wherein, sweep laser source, first optical coupler, polarization state generation module, optical circulator and optical transceiver and scanning module are sequentially connected;Polarization state analysis module, second optical coupler, photoelectric balance detector and signal acquisition and processing module are sequentially connected;First optical coupler is also connected with second optical coupler;Optical circulator is also connected with polarization state analysis module.The application realizes a kind of new laser radar system, which can be synchronized, high-speed, complete target distance, speed and complete mueller matrix are obtained by single sweep.

Description

Technical Field

[0001] This invention belongs to the field of lidar technology, specifically relating to a fully polarized FMCW lidar system and measurement method. Background Technology

[0002] Polarization lidar adds a completely new dimension of physical detection to traditional lidar by analyzing the polarization state information of light, demonstrating irreplaceable application value in many fields.

[0003] Current polarization measurement schemes in polarization lidar systems are mainly based on traditional ToF lidar, primarily divided into multi-channel and time-division multiplexing types. Both types have certain drawbacks. The multi-channel type suffers from complex system structure, high hardware cost, and difficulty in gain calibration. This is because it requires multiple detectors to detect light signals with different polarization directions. The inherent differences in the photoelectric responses of these detectors necessitate complex gain calibration to ensure measurement accuracy, increasing system control complexity and hardware cost. Furthermore, the integration of multiple detectors leads to a larger system size, hindering miniaturization. The time-division multiplexing type suffers from low measurement speed and poor real-time performance. This is because it requires changing the polarization state of the incident light time-division multiple times and performing multiple detections to obtain sufficient polarization information to calculate the Mueller matrix. The detection time is long, making it only suitable for scenarios with slow target changes, such as atmospheric and oceanic remote sensing monitoring, and unable to meet the real-time detection requirements of high-speed dynamic scenarios such as autonomous driving.

[0004] Frequency-modulated continuous wave (FMCW) lidar is an active optical detection technology based on coherent detection. Its core principle is to emit continuous laser light with a frequency that changes linearly with time, and to calculate target information using the frequency difference between the emitted and echo signals. It has significant advantages such as high detection accuracy, integrated ranging and velocity measurement, and strong anti-interference capabilities. However, existing polarization-based FMCW lidar also has certain shortcomings, mainly incomplete polarization information acquisition, inability to calculate the complete Mueller matrix, and high system complexity in some schemes. This is because existing polarization-based FMCW lidar often adopts limited-channel designs such as dual-channel or six-channel designs, which can only acquire partial elements of the Stokes vector or local elements of the Mueller matrix, and cannot achieve the calculation of the complete Mueller matrix. This makes it difficult to extract the complete polarization characteristics of the target, limiting the ability to identify and classify complex targets. Furthermore, multi-channel designs such as six-channel designs still have the problem of multi-detector gain calibration, resulting in high system complexity. Summary of the Invention

[0005] The main objective of this invention is to overcome the shortcomings and deficiencies of the prior art and to propose a fully polarized FMCW lidar system and measurement method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A fully polarized FMCW lidar system includes a frequency-sweeping laser source, a first optical coupler, a polarization state generation module, an optical circulator, an optical transceiver and scanning module, a polarization state analysis module, a second optical coupler, a photoelectric balance detector, and a signal acquisition and processing module.

[0008] The swept-frequency laser source, the first optical coupler, the polarization state generation module, the optical circulator, and the optical transceiver and scanning module are connected in sequence; the polarization state analysis module, the second optical coupler, the photoelectric balance detector, and the signal acquisition and processing module are connected in sequence.

[0009] The first optical coupler is also connected to the second optical coupler; the optical circulator is also connected to the polarization state analysis module.

[0010] The present invention also includes a measurement method based on the provided fully polarized FMCW lidar system, comprising the following steps:

[0011] A swept-frequency laser source outputs continuous light with linearly modulated frequency;

[0012] The continuous light output from the swept laser source is split into signal light and local oscillator light by the first optical coupler. The signal light enters the polarization state generation module, is modulated into a polarization state with a specific spectral code, and is then transmitted to the target through the circulator and then through the optical transceiver and scanning module.

[0013] The optical transceiver and scanning module is used to convert fiber or waveguide light into free space light and to perform beam spatial scanning. The return light carrying target information is received by the optical transceiver and scanning module and then introduced into the polarization state analysis module through the circulator for polarization state analysis and conversion.

[0014] The converted light and the local oscillator light enter the photoelectric balance detector through the second optical coupler for coherent mixing, and output a beat frequency signal containing distance, velocity and polarization information;

[0015] The signal acquisition and processing module calculates the beat frequency signal and simultaneously acquires the target's distance, velocity, and complete Mueller matrix.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0017] 1. Ultra-high-speed full polarization information acquisition capability; This invention adopts a single frequency sweep and full parameter acquisition scheme. The measurement speed is only limited by the period of a single FMCW frequency sweep, reaching the kHz to MHz level, compared to time-division polarization lidar that requires multiple measurements; By using frequency division multiplexing spectral coding technology in the polarization state generation module and analysis module, this invention improves the measurement speed by several orders of magnitude, making it possible to acquire the complete Mueller matrix of the target in real time on a high-speed moving vehicle platform.

[0018] 2. The system has a simple structure. By adopting a single-channel information carrier with a "spectral dimension" instead of the "spatial multi-channel" or "temporal multi-channel" of the existing technology, the core polarization modulation and demodulation module (PSG and PSA) of this invention consists only of a polarizer and a phase delayer. It is a passive optical device, which avoids the complex beam splitting optical path, multiple detectors and cumbersome channel gain calibration required by multi-channel schemes. While acquiring more complete information, it greatly simplifies the system architecture, reduces costs and improves reliability.

[0019] 3. Multi-dimensional information fusion: By deeply integrating the high-precision ranging and velocity measurement capabilities of FMCW with the efficient full polarization measurement capabilities of spectral intensity modulation, this invention can simultaneously and accurately acquire the geometric information (3D point cloud), motion state (velocity), and physical properties (Muller matrix) of the target. This multi-dimensional information fusion capability enables the system not only to "see" the target but also to "identify" the target's material properties (the polarization information of the Muller matrix can be used to calculate the target's refractive index, absorption coefficient, surface morphology, crystal structure, etc.), providing an unprecedented perception dimension for high-end applications such as autonomous driving. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the fully polarized FMCW lidar system of the present invention.

[0021] Figure 2 This is a schematic diagram of the polarization state generation module in the embodiment.

[0022] Figure 3 This is a schematic diagram of the polarization state analysis module in the embodiment.

[0023] Figure 4 This is a simulation verification diagram of the detection waveform of the fully polarized FMCW lidar system in the embodiment.

[0024] The reference numerals in the attached diagram are as follows: 1-Sweep laser source; 2-First optical coupler; 3-Polarization state generation module; 4-Optical circulator; 5-Optical transceiver and scanning module; 6-Polarization state analysis module; 7-Second optical coupler; 8-Photoelectric balance detector; 9-Signal acquisition and processing module. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0026] Examples; such as Figure 1 As shown, a fully polarized FMCW lidar system includes a frequency-sweeping laser source 1, a first optical coupler 2, a polarization state generation module 3, an optical circulator 4, an optical transceiver and scanning module 5, a polarization state analysis module 6, a second optical coupler 7, an optoelectronic balance detector 8, and a signal acquisition and processing module 9.

[0027] The swept-frequency laser source, the first optical coupler, the polarization state generation module, the optical circulator, and the optical transceiver and scanning module are connected in sequence; the polarization state analysis module, the second optical coupler, the photoelectric balance detector, and the signal acquisition and processing module are connected in sequence.

[0028] The first optical coupler is also connected to the second optical coupler; the optical circulator is also connected to the polarization state analysis module.

[0029] In this embodiment, the system operates by including the following steps:

[0030] S1, The swept-frequency laser source outputs continuous light with linearly modulated frequency;

[0031] S2. The continuous light output from the sweeping laser source is split into signal light and local oscillator light by the first optical coupler. The signal light enters the polarization state generation module, is modulated into a polarization state with a specific spectral code, and is then transmitted to the target through the circulator and then through the optical transceiver and scanning module.

[0032] S3, Optical transceiver and scanning module, is used to convert fiber or waveguide light into free space light and to perform beam spatial scanning; the return light carrying target information is received by the optical transceiver and scanning module and then introduced into the polarization state analysis module through the circulator for polarization state analysis and conversion;

[0033] S4. The converted light and the local oscillator light enter the photoelectric balance detector via the second optical coupler for coherent mixing, outputting a beat frequency signal containing distance, velocity, and polarization information; wherein, the beat frequency signal output by the photoelectric balance detector is expressed as:

[0034] Let the target distance be R, the radial velocity be v, and the sweep rate be K, then the beat frequency generated by the distance... =2K·R / c, Doppler frequency shift =2v / λ; Simultaneously, the birefringent optical path difference resulting from the birefringent crystal with a thickness of L in both the polarization state generation and polarization state analysis modules is Δn·L, which generates the spectral modulation frequency. =c / (Δn·L); The above 1:1:5:5 phase retardation ratio will produce a 1-12 times increase in the spectrum. Modulation frequency; where c is the speed of light, λ is the wavelength, and Δn is the birefringence coefficient of the crystal;

[0035] The beat frequency signal output by the photoelectric balance detector is represented as:

[0036] ;

[0037] in, For detector responsivity, coefficient , It is a linear function of the elements of the sample Mueller matrix M.

[0038] S5, the signal acquisition and processing module, calculates the analog beat frequency signal and simultaneously acquires the target's distance, velocity, and complete Mueller matrix; specifically, the signal acquisition and processing module includes the following steps:

[0039] S51, Analog-to-digital conversion; converting the analog beat frequency signal output by the photoelectric balance detector into a digital signal, with a sampling rate that satisfies the Nyquist sampling theorem (usually more than 2.5 times the highest beat frequency).

[0040] S52, Deskewing and Nonlinear Correction: The sweep frequency nonlinearity is measured in real time using an auxiliary MZI interferometer, and the digital signal is resampled or phase corrected to eliminate the influence of nonlinearity on the ranging resolution.

[0041] S53, Fast Fourier Transform; Perform a Fast Fourier Transform on the corrected digital signal to transform it to the frequency domain;

[0042] S54, Frequency domain separation; extracting components from the high-frequency band of the spectrum. The frequency components; in the low-frequency band of the spectrum, extract those containing The frequency components, the amplitude of which corresponds to each element of the Mueller matrix;

[0043] S55. Distance and velocity calculation; detection of peak frequencies in the high-frequency band; calculation of beat frequencies f for upper and lower sweep frequencies using a symmetrical triangular wave frequency modulation method. up and f down By combining the equations, we can obtain the distance R and the velocity v.

[0044] S56. Mueller matrix solution; extraction of characteristic frequencies from the low-frequency spectrum. The magnitude is worth , Substitute it into a pre-calibrated system of linear equations (or use a lookup table) to solve for the complete 4×4 Mueller matrix M of the target; the calibration process uses a set of standard samples with known Mueller matrices (such as air, linear polarizers, quarter-wave plates, etc.) to calibrate the system and obtain the conversion coefficients between the amplitude value and the M element;

[0045] S57. Data fusion and output: The calculated distance and velocity are correlated with the Mueller matrix point by point to generate a four-dimensional point cloud (three-dimensional coordinates + velocity + polarization attribute).

[0046] like Figure 4 As shown, this is a simulation verification diagram of the detection waveform of the fully polarized FMCW lidar system using air as a sample in the embodiment; the time-domain waveform obtained by simulating with air as a sample is as follows. Figure 4As shown in (a) above; the spectrum after FFT processing is as follows: Figure 4 As shown in (b) of the image. Low-frequency peaks in the spectrum correspond to polarization information, while high-frequency peaks correspond to range / velocity information. Further magnification of the low-frequency region (e.g.) Figure 4 (as shown in (c)) and demodulated, the Mueller matrix of air was obtained. The consistency between the Mueller matrix and the standard air Mueller matrix preliminarily verifies the feasibility of this scheme in realizing polarization measurement in the FMCW lidar system.

[0047] In the Mueller matrix calculation step, due to the non-ideal nature of the devices (such as waveplate delay deviation, limited polarizer extinction ratio, fiber splicing angle error, etc.), the directly calculated Mueller matrix will have systematic errors. Therefore, in this embodiment, the following calibration and compensation steps can also be adopted:

[0048] System matrix calibration; various known samples, including air samples, polarizers, quarter-wave plates, etc., are placed between the polarization state generation module and the polarization state analysis module to change the polarization state of the input light and measure the output signal; the system transformation matrix is ​​fitted using the differential evolution algorithm, thereby correcting the measured value to the true Mueller matrix;

[0049] Temperature and vibration compensation: The system integrates a temperature sensor and a reference optical path to monitor environmental changes in real time and dynamically correct the demodulation results.

[0050] like Figure 2 As shown, the polarization state generation module consists of a linear polarizer P1 and two cascaded phase delayers R1 and R2. The polarization state of the emitted light changes periodically with the wavelength, thereby "encoding" the polarization information onto the spectrum.

[0051] like Figure 3 As shown, the structure of the polarization state analysis module is symmetrical to that of the polarization state generation module, consisting of two cascaded phase retarders R3 and R4 and a linear polarizer P2. When the echo light carrying the target polarization information enters this module, it undergoes a process that is the reverse of that in the polarization state generation module. Ultimately, the light energy of different polarization states is redistributed to different spectral frequency channels and received by the detector, thus achieving the decoding and analysis of the echo light's polarization state.

[0052] The four phase delayers R1, R2, R3 and R4 are made of birefringent crystal waveplates. In this embodiment, the thickness ratio of the four waveplates is set to 1:1:5:5. In actual implementation, other ratios, such as 1:2:5:10, can also be used.

[0053] The fast axis azimuth angles of the four wave plates are respectively , , , In this embodiment, the angles are configured as 45°, 0°, 0° and 45°; other configurations may also be used in actual implementation.

[0054] The transmission axis angles of the two linear polarizers P1 and P2 are 0° and 90°, respectively, but other configurations can also be used in actual implementation.

[0055] Furthermore, since the frequency sweep range of FMCW lidar is typically only on the order of GHz, while the spectral modulation period (free spectral range FSR) of a traditional birefringent crystal waveplate is approximately 100 GHz, the difference is two orders of magnitude. To achieve matching, a polarization-maintaining fiber waveplate can be used instead of a birefringent crystal waveplate; specifically:

[0056] Select a length L of polarization-maintaining fiber (PMF) (typically 50-500 meters), and fusion splice its two ends to the input and output fibers at angles of 0° and 45° respectively. This PMF segment itself serves as an equivalent waveplate.

[0057] Alternatively, a spectral coding structure and configuration that can achieve the same technical effect can be used to replace the polarization state analysis module or polarization state generation module in the system of this embodiment.

[0058] The fully polarized FMCW lidar system in this embodiment is compatible with mechanical scanning, MEMS scanning, or solid-state optical phased array OPA scanning mechanisms.

[0059] The beam scanning mechanism is placed in the optical transceiver and scanning module. By precisely controlling the emission angle of the beam, the beam can illuminate the target area point by point according to the set law. At the same time, the echo signal in each direction is collected to obtain the distance, velocity and Mueller matrix of each pixel.

[0060] The data of all pixels are combined to form a three-dimensional polarization point cloud: each point contains coordinates, velocity, and material characteristic parameters derived from the Mueller matrix (such as depolarization index, linear polarization degree, circular polarization degree, phase retardation, etc.).

[0061] Finally, those skilled in the art should understand that in actual implementation, the number of phase retarders in the polarization state generation module and polarization state analysis module can be 2, 3, or more, as long as their combination can achieve spectral encoding of the polarization state. The phase retarder can be a birefringent crystal waveplate, fiber waveplate, liquid crystal variable retarder, or electro-optic crystal. The laser source is not limited to a single tunable laser; a broadband light source can also be used in conjunction with a spectrometer. In this case, the system's measurement speed depends on the spectrometer's acquisition rate.

[0062] Existing multi-channel polarization lidar employs a dual-channel / six-channel polarization detection architecture, requiring multiple detectors to detect signals in different polarization directions. This presents challenges in multi-detector gain calibration and results in a complex system structure. Furthermore, it can only acquire partial polarization information and cannot calculate the complete Mueller matrix. Existing time-division polarization lidar uses mechanically rotating waveplates or electro-optic modulators to sequentially generate and / or analyze multiple different polarization states in time, requiring multiple measurements to calculate the Mueller matrix, which is slow and unsuitable for dynamic scenarios. This invention utilizes the principle of spectral intensity modulation to orthogonally modulate different polarization state information onto different spectral frequency channels. Through a single FMCW frequency sweep, all 16 Mueller matrix elements can be extracted from the spectrum of the beat frequency signal in one go. Its core technique is "frequency division multiplexing," which is fundamentally different from the "time division multiplexing" of existing technologies.

[0063] In existing technologies, traditional FMCW only processes range and velocity, while existing polarization-based FMCW either only processes partial polarization information or fails to address the spectral interference problem among the three parameters. This invention establishes a unified signal model that includes range, velocity, and polarization terms. By optimizing the design of the polarization state generation and analysis modules, the modulation frequency corresponding to the polarization information (…) The frequency falls in the low-frequency range, while the beat frequency corresponding to distance / velocity ( The two components fall in the high-frequency band, achieving natural separation in the spectrum. The specific technical means is to use theoretical simulation to accurately select the length of the polarization-maintaining fiber or the free spectral range of the cascaded MZI, ensuring that the two frequency components do not overlap, thereby achieving crosstalk-free synchronous demodulation.

[0064] It should also be noted that, in this specification, terms such as "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0065] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A fully polarized FMCW lidar system, characterized in that, It includes a swept-frequency laser source, a first optical coupler, a polarization state generation module, an optical circulator, an optical transceiver and scanning module, a polarization state analysis module, a second optical coupler, a photoelectric balance detector, and a signal acquisition and processing module; The swept-frequency laser source, the first optical coupler, the polarization state generation module, the optical circulator, and the optical transceiver and scanning module are connected in sequence; the polarization state analysis module, the second optical coupler, the photoelectric balance detector, and the signal acquisition and processing module are connected in sequence. The first optical coupler is also connected to the second optical coupler; the optical circulator is also connected to the polarization state analysis module.

2. The fully polarized FMCW lidar system according to claim 1, characterized in that, The system operates by including the following steps: A swept-frequency laser source outputs continuous light with linearly modulated frequency; The continuous light output from the swept laser source is split into signal light and local oscillator light by the first optical coupler. The signal light enters the polarization state generation module, is modulated into a polarization state with a specific spectral code, and is then transmitted to the target through the circulator and then through the optical transceiver and scanning module. The optical transceiver and scanning module is used to convert fiber or waveguide light into free space light and to perform beam spatial scanning. The return light carrying target information is received by the optical transceiver and scanning module and then introduced into the polarization state analysis module through the circulator for polarization state analysis and conversion. The converted light and the local oscillator light enter the photoelectric balance detector through the second optical coupler for coherent mixing, and output a beat frequency signal containing distance, velocity and polarization information; The signal acquisition and processing module calculates the beat frequency signal and simultaneously acquires the target's distance, velocity, and complete Mueller matrix.

3. The fully polarized FMCW lidar system according to claim 1, characterized in that, The polarization state generation module consists of a linear polarizer P1 and two cascaded phase delayers R1 and R2. The structure of the polarization state analysis module is symmetrical to that of the polarization state generation module, and it consists of two cascaded phase delayers R3 and R4 and a linear polarizer P2.

4. The fully polarized FMCW lidar system according to claim 3, characterized in that, The four phase delayers R1, R2, R3 and R4 are made of birefringent crystal waveplates, and the thickness ratio of the four waveplates is set to, but is not limited to, 1:1:5:

5. The fast axis azimuth angles of the four wave plates are respectively , , , Angle configurations include, but are not limited to, 45°, 0°, 0° and 45°; The transmission axis angle configurations of the two linear polarizers P1 and P2 include, but are not limited to, 0° and 90°.

5. The fully polarized FMCW lidar system according to claim 4, characterized in that, The polarization-maintaining fiber waveplate is used to replace the birefringent crystal waveplate, specifically as follows: Select a polarization-maintaining fiber of length L and fusion splice its two ends to the input and output fibers at angles of 0° or 45° respectively; The spectral coding structure and configuration can achieve the same technical effect and replace the polarization state analysis module or polarization state generation module in the system.

6. The fully polarized FMCW lidar system according to claim 1, characterized in that, The fully polarized FMCW lidar system is compatible with mechanical scanning, MEMS scanning, or solid-state optical phased array OPA scanning mechanisms; The beam scanning mechanism is placed in the optical transceiver and scanning module. By precisely controlling the emission angle of the beam, the beam can illuminate the target area point by point according to the set law. At the same time, the echo signal in each direction is collected to obtain the distance, velocity and Mueller matrix of each pixel. The data from all pixels are combined to form a three-dimensional polarization point cloud: each point contains coordinates, velocity, and material characteristic parameters derived from the Mueller matrix.

7. The fully polarized FMCW lidar system according to claim 4, characterized in that, The beat frequency signal output by the photoelectric balance detector is represented as: Let the target distance be R, the radial velocity be v, and the sweep rate be K, then the beat frequency generated by the distance... =2K·R / c, Doppler frequency shift =2v / λ; Simultaneously, the birefringent optical path difference Δn·L caused by the birefringent crystal waveplate with a thickness of 1 L in the polarization state generation module and polarization state analysis module generates a spectral modulation frequency. =c / (Δn·L); A phase retardation ratio of 1:1:5:5 will produce a 1-12 times increase in the spectrum. Modulation frequency; where c is the speed of light, λ is the wavelength, and Δn is the birefringence coefficient of the crystal; The beat frequency signal output by the photoelectric balance detector is represented as: ； in, For detector responsivity, coefficient , It is a linear function of the elements of the sample Mueller matrix M.

8. A fully polarized FMCW lidar system according to claim 7, characterized in that, The signal acquisition and processing module includes the following steps: Analog-to-digital conversion; converting the analog beat frequency signal output by the photoelectric balance detector into a digital signal, with the sampling rate satisfying the Nyquist sampling theorem; Deskewing and nonlinearity correction: The sweep frequency nonlinearity is measured in real time using an auxiliary MZI interferometer, and the digital signal is resampled or phase corrected to eliminate the impact of nonlinearity on ranging resolution. Perform a Fast Fourier Transform on the corrected digital signal to transform it to the frequency domain; Frequency domain separation; extracting components in the high-frequency band of the spectrum. The frequency components; in the low-frequency band of the spectrum, extract those containing The frequency components, the amplitude of which corresponds to each element of the Mueller matrix, where ; Distance and velocity calculation; detection of peak frequencies in the high-frequency band; calculation of beat frequencies f for upper and lower sweep frequencies using a symmetrical triangular wave frequency modulation method. up and f down By combining the equations, we can obtain the distance R and the velocity v. Mueller matrix calculation; extraction of characteristic frequencies from the low-frequency spectrum. The magnitude is worth , Substitute it into a pre-calibrated system of linear equations to solve for the complete 4×4 Mueller matrix M of the target; the calibration process uses a set of standard samples with known Mueller matrices to calibrate the system and obtain the conversion coefficients between the amplitude value and the M element; Data fusion and output: The calculated distance and velocity are correlated point by point with the Mueller matrix to generate a four-dimensional point cloud.

9. A fully polarized FMCW lidar system according to claim 8, characterized in that, In the Mueller matrix calculation process, due to the non-ideal nature of the devices, the directly calculated Mueller matrix will contain systematic errors. Therefore, the following calibration and compensation steps are also adopted: System matrix calibration; various known samples, including but not limited to air samples, polarizers and quarter-wave plates, are placed between the polarization state generation module and the polarization state analysis module to change the polarization state of the input light and measure the output signal; the system transformation matrix is ​​fitted using the differential evolution algorithm, thereby correcting the measured value to the true Mueller matrix; Temperature and vibration compensation: The system integrates a temperature sensor and a reference optical path to monitor environmental changes in real time and dynamically correct the demodulation results.

10. A measurement method based on the fully polarized FMCW lidar system according to any one of claims 1-9, characterized in that, Includes the following steps: A swept-frequency laser source outputs continuous light with linearly modulated frequency; The continuous light output from the swept laser source is split into signal light and local oscillator light by the first optical coupler. The signal light enters the polarization state generation module, is modulated into a polarization state with a specific spectral code, and is then transmitted to the target through the circulator and then through the optical transceiver and scanning module. The optical transceiver and scanning module is used to convert fiber or waveguide light into free space light and to perform beam spatial scanning. The return light carrying target information is received by the optical transceiver and scanning module and then introduced into the polarization state analysis module through the circulator for polarization state analysis and conversion. The converted light and the local oscillator light enter the photoelectric balance detector through the second optical coupler for coherent mixing, and output a beat frequency signal containing distance, velocity and polarization information; The signal acquisition and processing module calculates the beat frequency signal and simultaneously acquires the target's distance, velocity, and complete Mueller matrix.

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