A multi-frequency lidar system based on polarization modulation

Abstract

A multi-frequency laser radar system based on polarization modulation, characterized in that it includes: a transmitter and a receiver; the transmitter is used to emit polarized laser; the transmitter includes a laser source and a polarization modulator; the laser source is used to emit laser; the polarization modulator is used to modulate the laser; the receiver is used to receive a specific reflection signal of the polarized laser. The utility model effectively improves the signal-to-noise ratio of the received signal of the laser radar in an outdoor sunlight environment, and increases the measurable distance while keeping the light source power and calculation accuracy unchanged.

Description

Technical Field

[0001] The utility model relates to the technical field of laser radars, and in particular to a multi-frequency laser radar system based on polarization modulation. Background Art

[0002] LiDAR is a radar system that emits laser beams to detect the position, speed and other characteristic quantities of a target. Its working principle is to emit a detection signal (laser beam) to the target, and then compare the received signal reflected from the target (target echo) with the transmitted signal. After appropriate processing, relevant information about the target can be obtained, such as target distance, direction, height, speed, attitude, shape and other parameters. Obtaining high-precision data from mobile platforms through LiDAR has been widely used in the field of autonomous driving.

[0003] The use scenarios of LiDAR systems applied in the field of autonomous driving are mostly outdoors. The near-infrared band in sunlight partially overlaps with the wavelength of the laser radar light source. Therefore, in addition to receiving the signal emitted by the laser light source and reflected by the object, the receiving sensor also receives the light emitted by the sunlight and reflected and scattered by the object. Compared with the light emitted by the laser radar light source, the light emitted by the sunlight and reflected and scattered by the object reaching the sensor is noise, and noise affects the working distance and calculation accuracy of the laser radar. When the noise increases, the signal-to-noise ratio of the signal decreases, the calculation accuracy deteriorates, and the corresponding measurable distance of the laser radar decreases.

[0004] The disclosure of the above background technology content is only used to assist in understanding the inventive concept and technical solution of the utility model. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above content has been disclosed on the filing date of this patent application, the above background technology should not be used to evaluate the novelty and creativity of the present application. Utility Model Content

[0005] To this end, the utility model proposes a multi-frequency lidar system based on polarization modulation, which uses a laser with polarization characteristics as a transmitting light source and cooperates with a receiving end with a polarization device to form a lidar system, thereby effectively improving the signal-to-noise ratio of the received signal of the lidar in an outdoor sunlight environment, and increasing the measurable distance while keeping the light source power and calculation accuracy unchanged.

[0006] The utility model provides a multi-frequency laser radar system based on polarization modulation, characterized in that it comprises: a transmitter and a receiver;

[0007] The transmitter is used to emit polarized laser light;

[0008] The transmitter includes a laser source and a polarization modulator;

[0009] The laser source is used to emit laser light;

[0010] The polarization modulator is used to modulate the laser;

[0011] The receiver is used for receiving a specific reflected signal of the polarized laser.

[0012] Optionally, the multi-frequency laser radar system based on polarization modulation is characterized in that the laser source comprises:

[0013] A first laser source, used to generate a first laser beam;

[0014] The second laser source is used to generate a second laser beam; the frequency of the first laser beam is different from the frequency of the second laser beam.

[0015] Optionally, the multi-frequency laser radar system based on polarization modulation is characterized in that the polarization modulator comprises:

[0016] A first polarization modulator, located in the optical path of the first laser beam, and used for specifically modulating the first laser beam into a first polarization state;

[0017] A second polarization modulator, located in the optical path of the second laser beam, and used for specifically modulating the second laser beam into a second polarization state;

[0018] The first polarization state is different from the second polarization state.

[0019] Optionally, the multi-frequency lidar system based on polarization modulation is characterized in that the second polarization state is related to the frequency of the second laser beam.

[0020] Optionally, the multi-frequency laser radar system based on polarization modulation is characterized in that the transmitter further includes:

[0021] An optical combiner is used to combine the first laser beam and the second laser beam without changing the polarization states of the first laser beam and the second laser beam.

[0022] Optionally, the multi-frequency laser radar system based on polarization modulation is characterized in that the receiver includes:

[0023] A third polarization modulator, used for filtering the reflected signal of the polarized laser;

[0024] The first sensor is used to receive the reflected signal filtered by the third polarization modulator.

[0025] Optionally, the multi-frequency laser radar system based on polarization modulation is characterized in that the receiver further comprises:

[0026] An optical splitter is used to separate the received multi-frequency reflected signals according to wavelength or frequency.

[0027] Optionally, the multi-frequency laser radar system based on polarization modulation is characterized in that the receiver further includes:

[0028] a fourth polarization modulator, used for filtering the reflected signal of the polarized laser; the third polarization modulator and the fourth polarization modulator have different polarization states;

[0029] The second sensor is used to receive the reflected signal filtered by the fourth polarization modulator.

[0030] Optionally, the multi-frequency lidar system based on polarization modulation is characterized in that the reflected signal is irradiated onto the third polarization modulator and the fourth polarization modulator respectively after passing through the spectrometer.

[0031] Optionally, the multi-frequency lidar system based on polarization modulation is characterized in that the first sensor and the second sensor are sensors of different types and are used to detect signal strength and polarization state at different frequencies.

[0032] Compared with the prior art, the utility model has the following beneficial effects:

[0033] The utility model uses a laser with polarization characteristics as the transmitting light source, and cooperates with a receiving end with a polarization device to form a laser radar system, which effectively improves the signal-to-noise ratio of the receiving signal of the laser radar in an outdoor sunlight environment, and increases the measurable distance while keeping the light source power and calculation accuracy unchanged. It can be applied to vehicles, service robots, drones and other fields involving autonomous driving. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without creative work. By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, purposes and advantages of the utility model will become more obvious:

[0035] Figure 1 This is a schematic structural diagram of a multi-frequency laser radar system based on polarization modulation in an embodiment of the utility model;

[0036] Figure 2 This is a schematic diagram of the structure of a transmitter in an embodiment of the utility model;

[0037] Figure 3 This is a schematic diagram of the structure of another transmitter in an embodiment of the utility model;

[0038] Figure 4 This is a schematic diagram of the structure of another transmitter in an embodiment of the utility model;

[0039] Figure 5 This is a schematic diagram of the structure of another transmitter in an embodiment of the utility model;

[0040] Figure 6 This is a schematic diagram of the structure of a receiver in an embodiment of the utility model;

[0041] Figure 7 This is a schematic diagram of the structure of another receiver in an embodiment of the utility model;

[0042] Figure 8 It is a structural schematic diagram of another receiver in an embodiment of the utility model.

[0043] 1- Transmitter;

[0044] 2- Receiver;

[0045] 3-Laser source;

[0046] 4-Polarization modulator;

[0047] 5- Random phase plate;

[0048] 6-Reflective mirror;

[0049] 7- Launch lens;

[0050] 8- a first laser source;

[0051] 9- second laser source;

[0052] 10-a first polarization modulator;

[0053] 11- a second polarization modulator;

[0054] 12-optical combiner;

[0055] 13- a third polarization modulator;

[0056] 14- first sensor;

[0057] 15-Spectrum splitter;

[0058] 16-a fourth polarization modulator;

[0059] 17- second sensor; DETAILED DESCRIPTION

[0060] The utility model is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the utility model, but do not limit the utility model in any form. It should be pointed out that for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the utility model. These all fall within the scope of protection of the utility model.

[0061] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present utility model and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the utility model described here, for example, can be implemented in an order other than those illustrated or described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0062] The embodiment of the utility model provides a multi-frequency laser radar system based on polarization modulation, aiming to solve the problems existing in the prior art.

[0063] The following specific embodiments are used to describe in detail the technical solution of the utility model and how the technical solution of the present application solves the above technical problems. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the utility model will be described below in conjunction with the accompanying drawings.

[0064] The laser radar system described in the utility model includes a transmitter and a receiver. The transmitter emits light with significant polarization characteristics, which may be possessed by the laser light source itself, or may be a laser light source without polarization characteristics with a set of polarization devices added thereto, thereby having polarization characteristics. The receiver includes a receiving sensor and a set of polarization devices. The polarization device is located outside the receiving sensor, and the optical signal passes through the polarization device before entering the receiving sensor, and only signals that meet specific polarization characteristics can enter the receiving sensor.

[0065] The emitter emits light with polarization characteristics, including but not limited to linear polarization and circular polarization. When the laser light source in the emitter itself has polarization characteristics, the polarization characteristics can be maintained without adding a polarization device, or the polarization characteristics can be changed by adding a polarization device. When the laser light source does not have polarization characteristics, a set of polarization devices can be added to the output end of the laser light source so that the laser emitted by the emitter has polarization characteristics.

[0066] When the laser light source does not have polarization characteristics, a polarizer with a specific polarization direction can be added to make the laser emitted by the transmitter have a specific polarization direction, that is, a linear polarization characteristic, and the polarization device is a polarizer; or a polarizer and a quarter wave plate can be added to make the laser initially set by the transmitter have a circular polarization characteristic, and the polarization device is a polarizer and a quarter wave plate. When the laser light source has a linear polarization characteristic, a quarter wave plate can be added to make the emitted light source have a circular polarization characteristic, and the polarization device is a quarter wave plate.

[0067] The receiver receives the optical signal emitted by the light source and returned by the measured object, and sets the polarization device attached to the sensor according to the polarization characteristics of the light emitted by the transmitter. If the light emitted by the transmitter is linearly polarized light, the polarization device is a polarizer with a specific polarization direction. If the light emitted by the transmitter is circularly polarized light, the polarization device is a quarter wave plate and a polarizer.

[0068] When the LiDAR system is used outdoors, especially in a sunlight environment, ambient light or sunlight emission and reflection and scattering from objects will enter the LiDAR system receiving sensor. These lights that are not emitted by the LiDAR light source and reflected from objects into the receiving sensor will become noise outside the required detection signal. Most of the light in the environment is unpolarized light. When the ambient light enters the LiDAR receiving device, part of the energy will be filtered out by the polarization device, and the signal-to-noise ratio of the light emitted by the emitting laser light source and reflected from the measured object will increase. Then, when the light source power and signal-to-noise ratio remain unchanged, the measurable distance will increase accordingly.

[0069] The following calculations show the signal-to-noise ratio of the received signal before and after adding a polarization device to the receiver. The laser emitted by the laser radar system's transmitter measures an object at a distance of d. The signal strength returned to the laser radar system's receiving device is S, and the noise signal reaching the receiving device is N. When the receiver does not have a polarization device, the signal strength received by the receiving sensor is S, and the noise strength received by the receiving sensor is N. The signal-to-noise ratio of the returned signal is

[0070] SNR=S / N (1)

[0071] When the distance of the object is d, the receiver is equipped with a polarization device, and the characteristics of the polarization device are determined by the polarization characteristics of the laser radar light source. The signal of the emitted light source returned by the measured object is almost lossless through the polarization device. Since the external ambient light is mainly composed of non-polarized light, the remaining energy of the non-polarized light after passing through the polarization device can be calculated as one-half. The signal strength received by the receiving sensor can be calculated as S, and the noise strength received by the receiving sensor is N / 2, then the signal-to-noise ratio of the returned signal is

[0072] SNR'=S / (N / 2)=2*S / N (2)

[0073] SNR'=2*SNR (3)

[0074] From (3), we can see that, without considering the loss of the return signal through the polarization device, the signal-to-noise ratio of the received signal of the laser radar system receiver adding a polarization device to measure the same distance object is twice that of the one without the polarization device. Consider changing the laser radar system measuring the object distance with the polarization device added to the receiving sensor to d1, so that the signal-to-noise ratio of the received signal of the receiving sensor is the same as that of the receiving signal of the receiving sensor without the polarization device added to measure the distance d. Then we have

[0075] S1=S*(d / d1) 4 (4)

[0076] SNR1=S1 / (N / 2) (5)

[0077] SNR1=SNR (6)

[0078] Taking (1) to (6) into consideration, we can get

[0079] d1≈1.189*d(7)

[0080] From (7), it can be seen that when the signal-to-noise ratio of the laser radar receiving sensor is kept the same, the receiving device can increase the object distance measured by the system by about 18.9% after adding the polarization device compared to the system without adding the polarization device.

[0081] The present invention is further described below with reference to the accompanying drawings.

[0082] Figure 1 FIG. 1 is a schematic diagram of the structure of a multi-frequency laser radar system based on polarization modulation in an embodiment of the present utility model. Figure 1 As shown, a multi-frequency laser radar system based on polarization modulation in an embodiment of the utility model includes:

[0083] Transmitter 1 and receiver 2.

[0084] Transmitter 1 is used to transmit polarized laser light. The main function of transmitter 1 is to transmit polarized laser light. Polarized laser light has a specific vibration direction compared to ordinary laser light, which enables it to produce unique reflection characteristics when interacting with a target object. The transmitter precisely controls the polarization state of the laser light to emit laser beams with specific polarization characteristics, which are then directed to the target area.

[0085] The transmitter 1 comprises a laser source 3 and a polarization modulator 4;

[0086] The laser source 3 is the core component of the transmitter, which is used to emit laser light. The laser source can be of various types, such as solid-state lasers, semiconductor lasers or fiber lasers, and a suitable laser light source is selected according to different application requirements. The polarization modulator 4 is used to modulate the laser light emitted by the laser source to achieve an output in a specific polarization state. The polarization modulator can be a wave plate, a polarization beam splitter or other polarization-related optical elements, which can change the vibration direction or phase of the light wave, thereby modulating the desired polarization state.

[0087] The receiver 2 is used to receive the polarized laser signal after being reflected by the target.

[0088] In some embodiments, the receiver 2 includes a receiving module and a polarization analysis module.

[0089] The receiving module usually includes a focusing optical system and a detector array. The focusing optical system focuses the reflected or backscattered laser from the target onto the detector, while the detector array is responsible for converting the optical signal into an electrical signal for subsequent processing and analysis.

[0090] Polarization analysis modules usually contain multiple detectors, each corresponding to a different polarization state. By comparing the signal strengths of different detectors, the polarization state of the incident light can be solved to obtain more information about the target.

[0091] Figure 2 FIG. 1 is a schematic diagram of the structure of a transmitter in an embodiment of the utility model. Figure 2 As shown, a transmitter in an embodiment of the utility model includes:

[0092] The light source 3 is used to emit laser.

[0093] Specifically, the light source 1 is the core part of the polarization projector, responsible for emitting laser light, that is, light without a specific polarization direction. The laser light can be light of any wavelength band, such as visible light, infrared light, ultraviolet light, etc.

[0094] The first polarizer 4 is located on the light path of the light source.

[0095] Specifically, the first polarizer 4 is located on the optical path of the light source 3. Its function is to obtain linearly polarized light from the laser. The first polarizer is usually composed of a multilayer film, which contains materials that can absorb or reflect light in a specific polarization direction. The number of first polarizers is one. In some embodiments, the first polarizer has only one vibration transmission direction, and only light waves vibrating along this direction can pass through. In some embodiments, the first polarizer has at least two vibration transmission directions, and the polarization directions of light emitted from different areas of the first polarizer are different. The polarization directions of different areas on the first polarizer can be vertical or at an angle of 45 degrees, 30 degrees, 15 degrees or any other angle.

[0096] The random phase plate 5 is located between the light source and the first polarizer.

[0097] Specifically, a random phase plate (RPP) is an optical element used to introduce random phase changes on the wavefront of a light beam. The surface of a random phase plate has irregular structures that introduce random phase delays on the passing light beam. This phase delay causes the wavefront of the light beam to be distorted, thereby changing the propagation characteristics and focusing performance of the light beam. The design and manufacture of a random phase plate requires precise control of the microstructure of its surface to ensure that the desired phase change can be accurately introduced into the light beam.

[0098] The reflective mirror 6 is located on the same side of the first polarizer as the light source and is used to reflect the laser.

[0099] Specifically, the reflective mirror 6 can change the direction of the light so that it propagates along the desired path. The reflective mirror is used to reflect the laser from the light source so that the light can be reflected and transmitted multiple times inside the polarization projector. Since the reflective mirror usually has a high reflectivity, the energy of the light can be retained to the maximum extent. The reflective mirror and the light source are located on the same side of the first polarizer, and can reflect the laser emitted by the light source back to the first polarizer and the random phase plate. After multiple reflections and polarization processing, more polarized light beams are finally emitted, which improves the light output rate, so that the light output rate can reach more than 90%.

[0100] In some embodiments, the reflective mirror wraps the side of the first polarizer facing the light source. The reflective mirror wraps the side of the first polarizer facing the light source, so that all light on the light source side can only be irradiated on the reflective mirror, the light source and the first polarizer, so that the light is reflected to the maximum extent. The reflective mirror is in an arc shape so that the laser is irradiated on the first polarizer with the least number of reflections, thereby reducing light loss and improving light extraction efficiency.

[0101] In some embodiments, the first polarizer completely covers the light path of the light source. The size of the first polarizer is large enough so that the laser light emitted from the light source is directly irradiated on the first polarizer without reflection, so that the emitted laser light is more uniform. Since the proportion of the emitted laser light is the highest when it is irradiated on the first polarizer for the first time, this embodiment can ensure the uniformity of the laser light.

[0102] In some embodiments, the first polarizer is connected to the reflective mirror to reflect more laser light.

[0103] Figure 3 FIG. 1 is a schematic diagram of the structure of another transmitter in the embodiment of the utility model. Figure 3As shown, the laser source in another transmitter in the embodiment of the utility model includes:

[0104] The first laser source 8 is used to generate a first laser beam.

[0105] Specifically, this laser source is responsible for generating the first laser beam of a certain frequency. It usually contains an activated gain medium, which can achieve population inversion under the action of an external excitation source, that is, the number of excited state particles at high energy levels is greater than that at low energy levels. Such a setting ensures high directivity and monochromaticity of the laser.

[0106] The second laser source 9 is used to generate a second laser beam; the frequency of the first laser beam is different from the frequency of the second laser beam.

[0107] Specifically, similar to the first laser source, the second laser source generates a laser beam with a different frequency from the first laser beam. Both the first laser beam and the second laser beam have the characteristics of good directionality, high brightness, and strong monochromaticity that are unique to lasers. These characteristics make laser radars perform well in long-distance detection and precise measurement.

[0108] The use of two laser beams of different frequencies in this embodiment allows the radar system to perform multi-frequency detection, which helps to obtain more information about the target object, such as its distance, speed, and material, and can improve the measurement capability and accuracy of the system. At the same time, multi-frequency technology can improve the accuracy of measurement and the ability to adapt to complex environments, and can be applied to multiple fields, including but not limited to remote sensing mapping, meteorological observation, environmental monitoring, and military reconnaissance.

[0109] Figure 4 FIG. 1 is a schematic diagram of the structure of another transmitter in the embodiment of the utility model. Figure 4 As shown, another polarization modulator in a transmitter in an embodiment of the utility model includes:

[0110] The first polarization modulator 10 is located in the optical path of the first laser beam, and is used for specifically modulating the first laser beam into a first polarization state.

[0111] Specifically, the first polarization modulator ensures that the first laser beam has unique polarization characteristics, which helps to distinguish and identify different laser beams through polarization analysis at the receiving end.

[0112] The second polarization modulator 11 is located in the optical path of the second laser beam, and is used for specifically modulating the second laser beam into a second polarization state.

[0113] Specifically, the first polarization state is different from the second polarization state. The second polarization modulator needs to achieve a modulation effect different from the first polarization modulator to ensure that the two laser beams are different in polarization state. The presence of the second polarization modulator enables the system to simultaneously emit two laser beams with different polarization states. This increases the complexity and flexibility of the system and may improve the accuracy and reliability of target detection.

[0114] In this embodiment, through the coordinated operation of the two polarization modulators, the multi-frequency laser radar system based on polarization modulation can emit laser beams with different polarization states, so that these laser beams can be distinguished and identified at the receiving end through polarization analysis.

[0115] In some embodiments, the second polarization state is related to the frequency of the second laser beam. According to the frequency of the second laser beam, the second polarization state is modulated into a corresponding polarization state. When there are two or more second laser beams, if the frequencies are different from each other, they are modulated into different polarization states respectively. Different frequencies are matched with different polarization states to better measure the information of the target object.

[0116] Figure 5 FIG. 1 is a schematic diagram of the structure of another transmitter in the embodiment of the utility model. Figure 5 As shown, compared with the above-mentioned embodiment, another transmitter in the embodiment of the utility model further includes:

[0117] The optical combiner 12 is used for combining the first laser beam and the second laser beam without changing the polarization states of the first laser beam and the second laser beam.

[0118] Specifically, the main function of the optical combiner is to combine the first laser beam and the second laser beam into one beam and emit it. This helps to improve the efficiency of the radar system because two lasers with different frequencies can be operated at the same time. During the merging process, the optical combiner must be designed to ensure that the original polarization state of the two laser beams is not changed. This is crucial because the polarization state contains important information about the target object and any change may cause errors in the measurement results. The combined laser beam will be used to illuminate the target and then the reflected laser signal will be collected. Since lasers of different frequencies and polarization states will react differently when interacting with the target material, the received reflected signal contains rich information, such as distance, speed and material. Optical combiners are usually implemented through a combination of various optical components (such as half-wave plates, polarization beam splitters, prisms, gratings, etc.). These components need to be precisely designed and placed to ensure that the two laser beams can be accurately combined and the polarization state is not affected.

[0119] The system of this embodiment maintains the independent polarization states of the two laser beams while merging them for transmission together, which enhances the performance of the laser radar, enabling it to detect and analyze targets more accurately.

[0120] Figure 6 Schematic diagram of the structure of a receiver in the embodiment of the utility model. Figure 6 As shown, a receiver in an embodiment of the utility model includes:

[0121] The third polarization modulator 13 is used to filter the reflected signal of the polarized laser.

[0122] Specifically, the third polarization modulator 13 filters out those chaotic laser signals that are not reflected by the target, ensuring that only those reflected signals in a specific polarization state can pass through, thereby improving the recognition accuracy and measurement accuracy of the system for the target object.

[0123] The first sensor 14 is used to receive the reflected signal filtered by the second polarization modulator.

[0124] Specifically, it is located after the third polarization modulator and is used to receive the reflected signal after being filtered by the third polarization modulator. These signals are converted from light into electrical signals for subsequent processing and analysis. The commonly used detectors are avalanche photodiodes (APDs) or PIN photodiodes, which have the characteristics of high sensitivity and fast response.

[0125] In this embodiment, a third polarization modulator is installed in the receiver, so that both the receiving end and the transmitting end can perform polarization processing, thereby further improving data quality.

[0126] Figure 7 FIG. 1 is a schematic diagram of the structure of another receiver in the embodiment of the utility model. Figure 7 As shown, compared with the above-mentioned embodiment, another receiver in the embodiment of the utility model further includes:

[0127] The optical splitter 15 is used to separate the received multi-frequency reflected signals according to wavelength or frequency.

[0128] Specifically, the spectrometer distinguishes the reflected signals of multiple frequencies according to the wavelength or frequency. Since two or more laser sources with different frequencies are used in the system, the reflected signal will contain information of these two or more frequencies. The spectrometer can effectively separate this information so that subsequent processing and analysis can be performed separately for each frequency, thereby obtaining more details about the target.

[0129] This embodiment uses a spectrometer to process information of multiple frequencies simultaneously, thereby improving the efficiency and information acquisition of the laser radar. In addition, it also helps to improve the accuracy and reliability of measurement, especially in complex environments.

[0130] Figure 8 FIG. 1 is a schematic diagram of the structure of another receiver in the embodiment of the utility model. Figure 8 As shown, compared with the above-mentioned embodiment, another receiver in the embodiment of the utility model further includes:

[0131] The fourth polarization modulator 16 is used to filter the reflected signal of the polarized laser. The third polarization modulator and the fourth polarization modulator have different polarization states.

[0132] Specifically, the fourth polarization modulator filters the stray light in the reflected laser signal and only allows light in a specific polarization state to pass through. Unlike the third polarization modulator, the fourth polarization modulator has different polarization states. This design allows the system to distinguish and analyze reflected signals from different polarization states. This helps to increase the amount of information measured, because different materials or surfaces have different reflection characteristics for polarized light, so the target material can be identified based on these characteristics, improving the ability to recognize complex scenes; it helps to reduce background noise and interference from non-target reflected signals, and improve the system's signal-to-noise ratio and detection accuracy. The presence of the fourth polarization modulator further enhances the system's target detection capabilities. By precisely controlling its polarization state, the system can more accurately identify and distinguish reflected signals from different targets, thereby improving the accuracy and reliability of target detection.

[0133] The second sensor 17 is used to receive the reflected signal filtered by the third polarization modulator.

[0134] Specifically, the second sensor converts the filtered optical signal into an electrical signal for subsequent processing and analysis. Similar to the first sensor, the main function of the second sensor is to convert the received optical signal into an electrical signal for subsequent signal processing and analysis. However, since it receives the signal filtered by the fourth polarization modulator, the signal processed by the second sensor is different from that of the first sensor. The presence of the second sensor enables the system to process reflected signals from different polarization states simultaneously. By combining the data from the first sensor and the second sensor, the system can obtain more comprehensive target information, thereby improving the accuracy and completeness of target detection.

[0135] In some embodiments, after the reflected signal passes through the beam splitter, it is irradiated on the third polarization modulator and the fourth polarization modulator respectively. The third polarization modulator and the fourth polarization modulator are located after the beam splitter to ensure that the signal is further processed before entering the first sensor and the second sensor.

[0136] In some embodiments, the first sensor and the second sensor are different types of sensors, which are used to detect signal strength and polarization state at different frequencies. Since different types of sensors have different ways of perceiving the environment and the target, the combination of different types of sensors can avoid the limitations and uncertainties of a single sensor. This multi-source heterogeneous information fusion method helps to form a more comprehensive and accurate understanding of the environment or the target.

[0137] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other. The above description of the disclosed embodiments enables professionals and technicians in this field to implement or use the utility model. Various modifications to these embodiments will be obvious to professionals and technicians in this field, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the utility model. Therefore, the utility model will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features disclosed herein.

[0138] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various modifications or variations within the scope of the claims, which does not affect the essence of the present invention.

Claims

1. A multi-frequency laser radar system based on polarization modulation, characterized in that: include: Transmitters and receivers; The transmitter is used to emit polarized laser light; The transmitter includes a laser source and a polarization modulator; The laser source is used to emit laser light; The polarization modulator is used to modulate the laser; The receiver is used to receive a specific reflected signal of the polarized laser; The laser source comprises: A first laser source, used to generate a first laser beam; A second laser source is used to generate a second laser beam; the frequency of the first laser beam is different from the frequency of the second laser beam; The polarization modulator comprises: A first polarization modulator, located in the optical path of the first laser beam, and used for specifically modulating the first laser beam into a first polarization state; A second polarization modulator, located in the optical path of the second laser beam, and used for specifically modulating the second laser beam into a second polarization state; The first polarization state is different from the second polarization state.

2. The multi-frequency laser radar system based on polarization modulation according to claim 1, characterized in that: The second polarization state is related to the frequency of the second laser beam.

3. The multi-frequency laser radar system based on polarization modulation according to claim 1, characterized in that: The transmitter also includes: An optical combiner is used to combine the first laser beam and the second laser beam without changing the polarization states of the first laser beam and the second laser beam.

4. A multi-frequency laser radar system based on polarization modulation, characterized in that: include: Transmitters and receivers; The transmitter is used to emit polarized laser light; The transmitter includes a laser source and a polarization modulator; The laser source is used to emit laser light; The polarization modulator is used to modulate the laser; The receiver is used to receive a specific reflected signal of the polarized laser; The receiver comprises: A third polarization modulator, used for filtering the reflected signal of the polarized laser; The first sensor is used to receive the reflected signal filtered by the third polarization modulator.

5. The multi-frequency laser radar system based on polarization modulation according to claim 4, characterized in that: The receiver also includes: An optical splitter is used to separate the received multi-frequency reflected signals according to wavelength or frequency.

6. The multi-frequency laser radar system based on polarization modulation according to claim 5, characterized in that: The receiver further comprises: a fourth polarization modulator, used for filtering the reflected signal of the polarized laser; the third polarization modulator and the fourth polarization modulator have different polarization states; The second sensor is used to receive the reflected signal filtered by the fourth polarization modulator.

7. The multi-frequency laser radar system based on polarization modulation according to claim 6, characterized in that: After passing through the optical splitter, the reflected signal is irradiated onto the third polarization modulator and the fourth polarization modulator respectively.

8. The multi-frequency laser radar system based on polarization modulation according to claim 6, characterized in that: The first sensor and the second sensor are sensors of different types and are used to detect signal strength and polarization states at different frequencies.

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