Mueller matrix laser radar

Abstract

The invention relates to the technical field of radars, in particular to a Mueller matrix laser radar which comprises an optical chip integrated with a pulse light modulator, a polarization state generator and a polarization measuring instrument. The optical circulator is provided with a first port, a second port and a third port, the first port is connected with the output end of the polarization state generator, and the third port is connected with the input end of the polarization measuring instrument; and a circuit control system 200. The pulse light is adjusted by the polarization state generator, then is input to the optical circulator from the first port and is output to a target object from the second port, return light interacting with the target object is input to the optical circulator from the second port and is output to the polarization measurement instrument from the third port, and the polarization measurement instrument measures the polarization state of the return light and outputs measurement data. The circuit control system constructs a Mueller matrix of the target object according to the polarization state of the emitted light and the polarization state of the returned light, and realizes distance measurement and component analysis of the target object by analyzing the Mueller matrix and comparing time delay of optical signals.

Description

Technical Field

[0001] The present application relates to the field of radar technology, and particularly to a Mueller matrix lidar. Background Art

[0002] A lidar is a radar system that detects the position, speed and other characteristic quantities of a target by emitting laser beams, and has a wide range of applications in modern detection fields. Among them, a polarization lidar is an indispensable part of a lidar. A polarization lidar can obtain the response information of a target object to polarized light, and obtain more physical information, especially performing excellently in fields such as the atmosphere, ocean, and earth surface.

[0003] When a polarization lidar works, pulsed light is generated by a transmitting system, and the polarization state of the light is controlled through polarization modulation, so as to emit the desired polarized light. After being scattered by a target object, it returns to the receiving system. The receiving system will divide the obtained polarized light into optical signals in different directions, and then convert these optical signals into electrical signals and transmit them to a signal processing system. Then, the signal processing system analyzes the obtained signals using a known mathematical model. For example, we can obtain information such as the particle concentration, distribution, and shape in the atmosphere.

[0004] The current polarization lidar has limited environmental adaptability. Under extreme weather conditions such as heavy rain, thick fog, and sandstorms, the propagation and reflection of laser beams will be interfered, resulting in a decrease in ranging accuracy or even failure; at the same time, in the detection of fine structures or small-sized targets, the resolution of the lidar may not meet the high-precision requirements. Summary of the Invention

[0005] The present application aims to solve at least one of the above technical problems in the prior art to some extent. For this reason, an embodiment of the present application provides a Mueller matrix lidar, which can extract the microscopic structure and composition information of a target object through Mueller matrix analysis, realize high-precision detection and identification of fine structures and small-sized targets, and overcome the deficiencies of traditional lidars in this regard.

[0006] A Mueller matrix lidar includes:

[0007] An optical chip, on which a pulsed light modulator, a polarization state generator and a polarization measuring instrument are integrated, and the output end of the pulsed light modulator is connected to the input end of the polarization state generator through an optical fiber;

[0008] An optical circulator having a first port, a second port and a third port, the first port is connected to the output end of the polarization state generator, and the third port is connected to the input end of the polarization measuring instrument through an optical fiber; and

[0009] A circuit control system is electrically connected to a pulse light modulator, a polarization state generator, and a polarization measuring instrument on the optical chip respectively. The circuit control system is used to control the pulse light modulator to generate pulsed light and control the polarization state generator to modulate the pulsed light into optical signals with different polarization states;

[0010] Among them, the pulsed light generated by the pulse light modulator is adjusted by the polarization state generator and then input from the first port to the optical circulator and output from the second port. The return light after interacting with the target object is input from the second port to the optical circulator and output from the third port to the polarization measuring instrument; the polarization measuring instrument is used to measure the polarization state of the return light and output measurement data; the circuit control system is also used to construct the Mueller matrix of the target object according to the polarization state of the emitted light and the polarization state of the return light, and realize the distance measurement and component analysis of the target object by analyzing the Mueller matrix and comparing the time delay of the optical signal.

[0011] In an optional or preferred embodiment, the pulse light modulator includes a Mach-Zehnder interferometer, and electrodes are integrated on two arms of the Mach-Zehnder interferometer to form a voltage-controlled electro-optic phase shifter to control the phase difference between the two arms.

[0012] In an optional or preferred embodiment, the pulse light modulator adjusts the pulsed light so that the output light has four different polarization states, and the polarization state of the output light cycles among these four polarization states.

[0013] In an optional or preferred embodiment, the polarization state generator includes:

[0014] A first polarization beam splitting rotator for receiving the pulsed light from the pulse light modulator;

[0015] A second polarization beam splitting rotator for outputting the modulated polarized optical signal to the first port of the optical circulator;

[0016] A multi-stage Mach-Zehnder interferometer structure is arranged between the first polarization beam splitting rotator and the second polarization beam splitting rotator. The multi-stage Mach-Zehnder interferometer structure includes at least two voltage-controlled electro-optic phase shifters and at least one multimode interference coupler connected in sequence;

[0017] In an optional or preferred embodiment, the polarization measuring instrument includes:

[0018] An end face coupler for coupling the optical signal output from the third port of the optical circulator into the optical chip;

[0019] A third polarization beam splitting rotator is connected to the output end of the end face coupler and is used to separate two orthogonal linear components of light into two waveguides;

[0020] Two optical power splitters, respectively connected to two output waveguides of the third polarization beam splitter rotator, and each output waveguide is connected to one of the optical power splitters;

[0021] Two cross-correlation analyzers, arranged at the output ends of the optical power splitters; and

[0022] Four photodetectors, respectively connected to four output ends of the cross-correlation analyzers, for converting optical signals into electrical signals and outputting them to the circuit control system.

[0023] In an optional or preferred embodiment, the polarization measuring instrument satisfies the following relationship: I = P·S in , where S in is the Stokes vector of the input light, P is a 4×4 matrix related to the power splitting ratio, and I is a vector composed of photocurrents measured by the four photodetectors.

[0024] In an optional or preferred embodiment, the optical circulator is a high-isolation optical circulator, and the isolation is not less than 20 dB.

[0025] In an optional or preferred embodiment, a semiconductor optical amplifier is further included. The semiconductor optical amplifier is arranged on the optical chip to replace the pulsed light modulator. A narrow pulse electrical signal generator is connected to the input end of the semiconductor optical amplifier, and the output end of the semiconductor optical amplifier is connected to the input end of the polarization state generator.

[0026] In an optional or preferred embodiment, the circuit control system includes:

[0027] A data acquisition module, for acquiring the electrical signals output by the polarization measuring instrument;

[0028] A signal processing module, for processing the electrical signals and calculating the Stokes vector;

[0029] A Mueller matrix calculation module, for calculating the Mueller matrix according to the Stokes vectors of the transmitted light and the returned light;

[0030] A target characteristic analysis module, for analyzing the characteristic parameters of the target object according to the Mueller matrix and the optical signal time delay data;

[0031] A data storage module, for storing preset Mueller matrix reference data and measurement result data.

[0032] In an optional or preferred embodiment, the optical chip is made of thin-film lithium niobate material.

[0033] Based on the above technical solution, the embodiments of the present application have at least the following beneficial effects: The pulsed light generated by the pulsed light modulator is adjusted by the polarization state generator and then input from the first port to the optical circulator and output from the second port to the target object. The return light after interacting with the target object is input from the second port to the optical circulator and output from the third port to the polarization measuring instrument. The polarization measuring instrument measures the polarization state of the return light and outputs measurement data. The circuit control system constructs the Mueller matrix of the target object based on the polarization state of the transmitted light and the polarization state of the return light. By analyzing the Mueller matrix and comparing the time delay of the optical signal, the distance measurement and component analysis of the target object are realized. Through Mueller matrix analysis, the microscopic structure and composition information of the target object can be extracted, and high-precision detection and identification of fine structures and small-sized targets can be achieved, overcoming the deficiencies of traditional lidars in this regard. Brief Description of the Drawings

[0034] The following further describes the present application in conjunction with the drawings and embodiments;

[0035] Figure 1 is a schematic structural diagram of the Mueller matrix lidar provided by the embodiments of the present application;

[0036] Figure 2 is a schematic diagram of the pulsed light modulator provided by the embodiments of the present application;

[0037] Figure 3 is a schematic diagram of the polarization state generator provided by the embodiments of the present application;

[0038] Figure 4 is a schematic diagram of the polarization measuring instrument provided by the embodiments of the present application. Detailed Embodiments

[0039] In order to enable those skilled in the art to better understand the technical solutions in the present application, the following will clearly and completely describe the technical solutions in the embodiments of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0040] The following further describes the embodiments of the present application in conjunction with the drawings and embodiments in detail. The following embodiments are used to illustrate the present application, but cannot be used to limit the scope of the present application.

[0041] In the description of the embodiments of the present application, it should be noted that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the embodiments of the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the embodiments of the present application. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0042] In the description of the embodiments of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "connected" and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific situations.

[0043] In the embodiments of the present application, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature can be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature can be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0044] A lidar is a radar system that emits laser beams to detect the position, speed and other characteristic quantities of a target, and has a wide range of applications in modern detection fields. Among them, a polarization lidar is an indispensable part of a lidar. A polarization lidar can obtain the response information of a target object to polarized light and obtain more physical information, especially showing excellent performance in the fields of atmosphere, ocean, earth surface, etc.

[0045] When a polarization lidar works, pulsed light is generated by the emission system, and the polarization state of the light is controlled through polarization modulation, so as to emit the desired polarized light. After being scattered by the target object, it returns to the receiving system. The receiving system will divide the obtained polarized light into optical signals in different directions, and then convert these optical signals into electrical signals and transmit them to the signal processing system. Then, the signal processing system uses a known mathematical model to analyze the obtained signals. For example, we can obtain information such as the particle concentration, distribution, and shape in the atmosphere.

[0046] Today's polarization lidar has limited environmental adaptability. Under extreme weather conditions such as heavy rain, thick fog, and sandstorms, the propagation and reflection of laser beams will be disturbed, resulting in a decrease in ranging accuracy or even failure. At the same time, in the detection of fine structures or small-sized targets, the resolution of lidar may not meet the high-precision requirements.

[0047] This application provides a Mueller matrix lidar, which realizes highly integrated and all-solid-state design. It can improve the detection accuracy while enhancing the adaptability to extreme environments and effectively solve the deficiencies of existing polarization lidars in the recognition of fine structures.

[0048] Referring to Figure 1 , the Mueller matrix lidar of this application includes an optical chip, an optical circulator 100, and a circuit control system 200.

[0049] The optical chip is integrated with a pulsed light modulator 300, a polarization state generator 400, and a polarization measuring instrument 500. The output end of the pulsed light modulator 300 is connected to the input end of the polarization state generator 400 through an optical fiber. The optical circulator 100 has a first port, a second port, and a third port. The first port is connected to the output end of the polarization state generator 400 through an optical fiber, and the third port is connected to the input end of the polarization measuring instrument 500 through an optical fiber. The circuit control system 200 is connected to the pulsed light modulator 300, the polarization state generator 400, and the polarization measuring instrument 500 on the optical chip through electrical connections.

[0050] The circuit control system 200 controls the pulsed light modulator 300 to generate pulsed light and controls the polarization state generator 400 to modulate the pulsed light into optical signals with different polarization states. The pulsed light generated by the pulsed light modulator 300 is adjusted by the polarization state generator 400 and then input into the optical circulator 100 from the first port and output from the second port towards the target object 600. The return light after interacting with the target object 600 is input into the optical circulator 100 from the second port and output from the third port to the polarization measuring instrument 500. The polarization measuring instrument 500 measures the polarization state of the return light and outputs measurement data. The circuit control system 200 constructs the Mueller matrix of the target object 600 based on the polarization state of the emitted light and the polarization state of the return light, and realizes the distance measurement and composition analysis of the target object 600 by analyzing the Mueller matrix and comparing the time delay of the optical signals.

[0051] This application uses thin-film lithium niobate material to make the optical chip. Thin-film lithium niobate has excellent electro-optic characteristics and a relatively high refractive index, which can realize the efficient modulation and transmission of optical signals. The thin-film lithium niobate material also has excellent temperature stability and anti-environmental interference ability, improving the working reliability of the lidar in harsh environments.

[0052] Referring to Figure 2 、Figure 3 , in this application, an optical chip based on thin-film lithium niobate is used to realize the integration of optical devices. A lithium niobate-based planar waveguide structure 10 is deposited on the substrate of the optical chip of thin-film lithium niobate. A lithium niobate-based ridge waveguide structure 20 is formed by etching on the lithium niobate-based planar waveguide structure 10 for the conduction of optical waveguides. Using this structure can achieve the characteristics of small volume, low loss, and high electro-optic effect efficiency.

[0053] The pulse light modulator 300, polarization state generator 400, and polarization measuring instrument 500 in this application are all constructed based on this structure. As Figure 2 shown in the schematic diagram of the pulse light modulator 300, Figure 3 is the schematic diagram of the polarization state generator 400.

[0054] In some embodiments, the pulse light modulator 300 includes a Mach-Zehnder interferometer. Electrodes are integrated on the two arms of the Mach-Zehnder interferometer to form a voltage-controlled electro-optic phase shifter 30 to control the phase difference between the two arms. When continuous light is input, under the control of the circuit control system 200, by applying a voltage to the electrodes, the electro-optic effect of thin-film lithium niobate is used to change the propagation phase of the optical wave in the two arms. When the phase difference is set to π, the two beams of light undergo destructive interference at the beam combining point, and the output light intensity approaches zero; when the phase difference is set to 0 or 2π, the two beams of light undergo constructive interference at the beam combining point, and the output light intensity reaches the maximum value. By modulating the applied voltage, the generation of pulsed light can be achieved, and the frequency, duty cycle, and waveform of the pulse can be controlled.

[0055] The circuit control system 200 adopts a combined design of a high-speed digital signal processor and a field programmable gate array, and can generate precise drive signals to control the pulse light modulator 300 to generate pulsed light.

[0056] In some embodiments, the polarization state generator 400 adopts a multi-stage Mach-Zehnder interferometer structure design. The polarization state generator 400 includes a first polarization beam splitting rotator, a second polarization beam splitting rotator, and a multi-stage Mach-Zehnder interferometer structure disposed between the first polarization beam splitting rotator and the second polarization beam splitting rotator.

[0057] The multi-stage Mach-Zehnder interferometer structure includes two voltage-controlled electro-optic phase shifters 30 connected in sequence and a multimode interference coupler.

[0058] Assume that the phase shift angles caused by the two electro-optic phase shifters are θ and φ respectively. Through derivation, when the input polarization state is set to horizontal polarization, the Stokes vector of the output light is: S=(1 cosθ - sinθ cosφ - sinθ sinφ)T.

[0059] Specifically, when θ = 0, the output is linearly horizontally polarized light; when θ = π / 2 and φ = 0, the output is linearly vertically polarized light; when θ = π / 2 and φ = π / 2, the output is right-handed circularly polarized light; when θ = π / 2 and φ = 3π / 2, the output is left-handed circularly polarized light. By precisely controlling θ and φ through the circuit control system 200, the longitude and latitude of the polarization state of light on the Poincaré sphere can be changed, generating light with different polarization states.

[0060] A polarization state control module is provided in the circuit control system 200. This module uses a high-speed digital-to-analog converter and can achieve rapid switching between different polarization states. In addition, the system is also equipped with a temperature compensation circuit to ensure that within the operating temperature range of -20°C to 60°C, the fluctuation of the generation accuracy of the polarization state does not exceed 1%.

[0061] In some embodiments, a high-isolation optical circulator 100 is used as the separation device for transmitted light and received light. Its isolation is not less than 20 dB, ensuring unidirectional transmission of optical signals in the system, effectively preventing crosstalk between transmitted light and received light, improving the purity of the signal and the measurement accuracy. At the same time, due to the unidirectional transmission characteristic of the optical circulator 100, the stability and reliability of the system are improved. Using the optical circulator 100 also avoids complex optical path separation and simplifies the overall architecture of the system.

[0062] The specific working principle of the optical circulator 100 is as follows: The polarized light output by the polarization state generator 400 is input from the first port of the optical circulator 100, and after being transmitted through the internal optical path, it is output from the second port and directed towards the target object 600. The return light reflected by the target object 600 is input from the second port, and after being transmitted through the internal optical path, it is output from the third port and enters the polarization measuring instrument 500. This working method avoids the power loss caused by traditional beam splitters and significantly improves the energy utilization efficiency of the system.

[0063] Refer to Figure 4 , in some embodiments, the polarization measuring instrument 500 includes an end face coupler 40, a third polarization beam splitting rotator 50, two optical power splitters 60, two cross-correlation analyzers 70, and four photodetectors 80.

[0064] The end-face coupler 40 is used to couple the optical signal output from the third port of the optical circulator 100 into the optical chip. The third polarization beam splitting rotator 50 is connected to the output end of the end-face coupler 40 and is used to separate the two orthogonal linear components of light into two waveguides. Two optical power splitters 60 are respectively connected to the two output waveguides of the third polarization beam splitting rotator 50, and each waveguide is connected to an optical power splitter 60. Two cross-correlation analyzers 70 are arranged at the output ends of the optical power splitters 60. Four photodetectors 80 are respectively connected to the four output ends of the cross-correlation analyzers 70 and are used to convert the optical signal into an electrical signal and output it to the circuit control system 200.

[0065] During operation, the return light output from the third port of the optical circulator 100 is coupled into the optical chip through the end-face coupler 40, and then the third polarization beam splitting rotator 50 separates the two orthogonal linear components of light, namely the transverse electric mode light and the transverse magnetic mode light, into two waveguides, and at the same time converts the transverse magnetic mode light into transverse electric mode light. Subsequently, each of the two waveguides is connected to two optical power splitters 60. After passing through the two cross-correlation analyzers 70, it is finally introduced into the four photodetectors 80 for the measurement of the light intensity.

[0066] The polarization measuring instrument 500 satisfies the following relationship: I = P·S in , where S in is the Stokes vector of the input light, P is a 4×4 matrix related to the power splitting ratio α / β, I = (I 1 , I 2 , I 3 , I 4 ) T , I 1 , I 2 , I 3 , I 4 represents the photocurrents measured by the four photodetectors 80, I is the vector composed of the photocurrents measured by the four photodetectors 80, and T is the pulse period. By measuring the photocurrents of different paths, the Stokes vector of the return light can be reconstructed, thereby obtaining the polarization state information of the return light.

[0067] The polarization measuring instrument 500 of this embodiment uses high-speed photodetectors 80. At the same time, the four photodetectors 80 adopt a matching design to ensure the accuracy of the polarization state measurement. The splitting ratio α / β of the optical power splitter 60 is precisely designed to minimize the condition number of the matrix P, improving the stability and noise resistance of the Stokes vector reconstruction.

[0068] In some embodiments, the circuit control system 200 includes a data acquisition module, a signal processing module, a Mueller matrix calculation module, a target characteristic analysis module, and a data storage module.

[0069] The data acquisition module uses a high-speed analog-to-digital converter to collect the electrical signals output by the polarization measuring instrument 500.

[0070] The signal processing module is designed based on a digital signal processor to implement signal filtering, amplification, and synchronization processing, and calculate the Stokes vector of the return light. This module processes the signals of the four photodetectors 80 for each optical pulse in parallel, and obtains the Stokes vector by solving an overdetermined system of equations.

[0071] The Mueller matrix calculation module uses a floating-point arithmetic unit to calculate the Mueller matrix based on the Stokes vectors of the transmitted light and the return light. For each transmitted polarization state, the system records the corresponding return polarization state, combines four different polarization state transmit-receive pairs, and constructs a complete 4×4 Mueller matrix.

[0072] The target feature analysis module includes feature extraction algorithms and pattern recognition algorithms, which can extract the polarization feature parameters of an object from the Mueller matrix, such as depolarization ratio, dichroism, phase delay, etc. At the same time, by comparing the time delays of the optical signals, the distance of the target object 600 is calculated.

[0073] The data storage module uses a large-capacity flash memory to store a preset Mueller matrix reference database and measurement result data. The reference database contains the standard Mueller matrices of various common materials and substances, which is convenient for comparison with the measurement results to achieve material identification and classification of the target object 600.

[0074] In some embodiments, the pulsed light generating device uses a semiconductor optical amplifier to replace the pulsed light modulator 300 with a Mach-Zehnder interferometer structure. The semiconductor optical amplifier is disposed on the optical chip, and its input end is connected to a narrow pulsed electrical signal generator, and the output end is connected to the input end of the polarization state generator 400.

[0075] During operation, the narrow pulsed electrical signal generator generates a high-speed electrical pulse signal to drive the semiconductor optical amplifier for gain modulation to achieve the generation of optical pulses. The semiconductor optical amplifier has a higher modulation depth and a lower drive voltage, and can achieve a narrower optical pulse width, which is beneficial to improving the range resolution of the radar.

[0076] In addition, the semiconductor optical amplifier has an amplification function, which can increase the output optical power and increase the detection range of the lidar.

[0077] In other embodiments, in order to improve the performance of the system in specific application scenarios, the polarization state generator 400 can also be optimized. The optimized polarization state generator 400 can generate eight different polarization states, including horizontal linear polarization, vertical linear polarization, +45° linear polarization, -45° linear polarization, right-handed circular polarization, left-handed circular polarization, and two elliptical polarization states.

[0078] The specific implementation method is to add a stage of Mach-Zehnder interferometer structure in the polarization state generator 400, so that the multi-stage Mach-Zehnder interferometer structure includes four voltage-controlled electro-optic phase shifters 30 and three multimode interference couplers. By adding a degree of freedom, the polarization state of the output light can be controlled more precisely, covering more points on the Poincaré sphere.

[0079] This design can obtain richer target polarization scattering characteristics, improving the measurement accuracy and reliability of the Mueller matrix. Especially for target objects 600 with complex microstructures, it can provide more detailed polarization characteristic information to support more accurate material identification and classification.

[0080] The beneficial effects of this application are as follows:

[0081] 1. Integrating three key devices, namely the pulse light modulator 300, the polarization state generator 400, and the polarization measuring instrument 500, on an optical chip significantly reduces the volume and weight of the system, and improves the stability and reliability of the system. The adoption of thin-film lithium niobate material further improves the degree of integration, enabling large-scale and high-density photon integration.

[0082] 2. By precisely controlling the polarization state of the emitted light and highly sensitively detecting the polarization state of the returned light, combined with signal processing algorithms, the Mueller matrix of the target object 600 can be accurately constructed, providing rich target characteristic information.

[0083] 3. The all-solid-state design and electronic control enable the system to still work stably in extreme environments, allowing the system to still work effectively under harsh meteorological conditions such as heavy rain and thick fog, solving the problem of limited environmental adaptability of traditional polarization lidars.

[0084] 4. Through Mueller matrix analysis, the microscopic structure and composition information of the target object 600 can be extracted, realizing high-precision detection and identification of fine structures and small-sized targets, overcoming the deficiencies of traditional lidars in this regard.

[0085] 5. The use of the optical circulator 100 avoids the power loss caused by traditional beam splitters, improving the energy utilization efficiency.

[0086] With the above advantages, the Mueller matrix lidar of this application has broad application prospects in many fields such as environmental monitoring, biomedical detection, material analysis, autonomous driving, and UAV obstacle avoidance.

[0087] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc., mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of this application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0088] The above has described the embodiments of this application in detail with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art in the said technical field, various changes can also be made without departing from the purpose of this application.

Claims

1. A Mueller matrix laser radar, characterized in that: include: An optical chip, on which a pulse light modulator, a polarization state generator and a polarization meter are integrated, and an output end of the pulse light modulator is connected to an input end of the polarization state generator via an optical fiber; An optical circulator, comprising a first port, a second port and a third port, wherein the first port is connected to the output end of the polarization state generator, and the third port is connected to the input end of the polarization meter through an optical fiber; as well as A circuit control system is electrically connected to the pulse light modulator, the polarization state generator and the polarization measuring instrument on the optical chip, respectively, and the circuit control system is used to control the pulse light modulator to generate pulse light, and control the polarization state generator to modulate the pulse light into optical signals with different polarization states; Among them, the pulse light generated by the pulse light modulator is adjusted by the polarization state generator, input from the first port to the optical circulator and output from the second port, and the return light after interacting with the target object is input from the second port to the optical circulator and output from the third port to the polarization meter; the polarization meter is used to measure the polarization state of the return light and output measurement data; the circuit control system is also used to construct the Mueller matrix of the target object according to the polarization state of the emitted light and the polarization state of the return light, and realize the distance measurement and component analysis of the target object by analyzing the Mueller matrix and comparing the time delay of the optical signal.

2. The Mueller matrix laser radar according to claim 1, characterized in that: The pulse light modulator comprises a Mach-Zehnder interferometer, and electrodes are integrated on the two arms of the Mach-Zehnder interferometer to form a voltage-controlled electro-optical phase shifter to control the phase difference between the two arms.

3. The Mueller matrix laser radar according to claim 1, characterized in that: The pulse light modulator adjusts the pulse light so that the output light has four different polarization states, and the polarization state of the output light cycles among the four polarization states.

4. The Mueller matrix laser radar according to claim 1, characterized in that: The polarization state generator comprises: A first polarization beam splitter rotator, used for receiving the pulse light from the pulse light modulator; A second polarization beam splitter rotator, used for outputting a modulated polarized light signal to the first port of the optical circulator; A multi-stage Mach-Zehnder interferometer structure is arranged between the first polarization beam splitter rotator and the second polarization beam splitter rotator, and the multi-stage Mach-Zehnder interferometer structure includes at least three voltage-controlled electro-optical phase shifters and at least two multi-mode interference couplers connected in sequence; wherein the first stage of the multi-stage Mach-Zehnder interferometer structure is used as a beam splitter with a variable splitting ratio, and the subsequent stages are used for adjusting the polarization state.

5. The Mueller matrix laser radar according to claim 1, characterized in that: The polarimeter comprises: An end coupler, used for coupling an optical signal output from the third port of the optical circulator into an optical chip; A third polarization beam splitter rotator connected to the output end of the end coupler, for separating two orthogonal linear components of light into two waveguides; Two optical power beam splitters, respectively connected to two output waveguides of the third polarization beam splitter rotator, each output waveguide is connected to one of the optical power beam splitters; two cross-coherence analyzers, arranged at the output end of the optical power beam splitter; and Four photoelectric detectors are respectively connected to the four output ends of the cross-coherence analyzer and are used to convert optical signals into electrical signals and output them to the circuit control system.

6. The Mueller matrix laser radar according to claim 5, characterized in that: The polarimeter satisfies the following relationship: I = P·S in , where S in is the Stokes vector of the input light, P is a 4×4 matrix related to the power splitting ratio, and I is a vector composed of the photocurrents measured by the four photodetectors.

7. The Mueller matrix laser radar according to claim 1, characterized in that: The optical circulator is a high-isolation optical circulator with an isolation not less than 20 dB.

8. The Mueller matrix laser radar according to claim 1, characterized in that: It also includes a semiconductor optical amplifier, which is arranged on the optical chip to replace the pulse optical modulator. The input end of the semiconductor optical amplifier is connected to a narrow pulse electrical signal generator, and the output end of the semiconductor optical amplifier is connected to the input end of the polarization state generator.

9. The Mueller matrix laser radar according to claim 1, characterized in that: The circuit control system comprises: A data acquisition module, used for acquiring the electrical signal output by the polarization measuring instrument; A signal processing module, used for processing the electrical signal and calculating the Stokes vector; A Mueller matrix calculation module, used for calculating the Mueller matrix according to the Stokes vectors of the emitted light and the returned light; A target characteristic analysis module, used for analyzing characteristic parameters of a target object according to the Mueller matrix and the optical signal time delay data; The data storage module is used to store preset Mueller matrix reference data and measurement result data.

10. The Mueller matrix laser radar according to any one of claims 1 to 9, characterized in that: The optical chip is made of thin-film lithium niobate material.

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