A vehicle-mounted laser radar system suitable for rainy days

Abstract

This invention discloses a vehicle-mounted lidar system suitable for rainy weather, comprising: a rain sensor, a laser emitting module, a receiving module, a signal processing module, and a ranging module. This invention detects rainfall in rainy conditions and adjusts the configuration parameters of the laser emitting module accordingly, enabling the periodic alternation of laser beam A and laser beam B. This allows laser beams A and B to better detect their respective useful targets under different rainfall levels, generating sufficient echo signals from the useful targets, thus enabling the system to obtain more accurate point cloud data. Next, the signal receiving and signal processing modules perform hierarchical processing on the clutter signals in the echo signals of laser beams A and B, ultimately obtaining a more accurate point cloud signal of the useful targets from the echo signal generated by laser beam B. Finally, the ranging and image generation modules achieve clear imaging and accurate ranging of the useful targets.

Description

Technical Field

[0001] This invention relates to a lidar, specifically to a vehicle-mounted lidar system. Background Technology

[0002] LiDAR boasts advantages such as high precision, wide field of view, and good stability, making it suitable for operational needs in most scenarios. LiDAR is considered a future major player in the field of autonomous driving in automobiles. However, despite its significant advantages, LiDAR suffers from disadvantages due to the short wavelength and weak penetration of laser light. When encountering media that affect light propagation, such as raindrops, a reflection phenomenon occurs, causing these media to be mismeasured as obstacles. This results in false alarm point clouds in the perception algorithm, leading to misjudgments by the vehicle-mounted LiDAR and hindering its ability to achieve clear imaging and accurate distance measurement in adverse weather conditions.

[0003] In lidar systems, the received echo signal usually contains various noises in addition to the effective reflected echo. These noises, combined with the reflected echo from the target, reduce the signal-to-noise ratio (SNR) of the received echo, severely decreasing the system's measurement accuracy and significantly reducing the effective detection range. The SNR of the received laser echo largely determines the system's ranging and scanning performance.

[0004] Currently, LiDAR generally uses filtering algorithms to filter received clutter signals. Although filtering algorithms are constantly being improved, a single filtering algorithm can only achieve a relatively good effect in filtering clutter signals in a specific scenario. Especially in severe weather, the types of clutter signals are more diverse, making it very difficult to filter clutter signals using filtering algorithms.

[0005] In conclusion, achieving clear imaging and accurate ranging for vehicle-mounted LiDAR in adverse weather conditions is a major challenge in the current LiDAR field. Summary of the Invention

[0006] Purpose of the invention: In view of the above-mentioned prior art, this invention proposes a vehicle-mounted lidar system suitable for rainy weather, which solves the problem of severe clutter interference in rainy weather.

[0007] Technical solution: A vehicle-mounted lidar system suitable for rainy weather, comprising: a rain sensor, a laser emitting module, a receiving module, a signal processing module, and a ranging module;

[0008] The rain sensor is used to detect the current amount of rainfall and determine the rainfall level.

[0009] The laser emitting module is used to periodically emit two different laser beams alternately. The target of laser beam A is the raindrops falling in real time, and the target of laser beam B is the road conditions in front of the vehicle in real time. The emission power, wavelength and emission distance of laser beam A and laser beam B are controlled according to the level of rainfall.

[0010] The receiving module is used to receive the light signal reflected back from the laser beam and to perform background light noise reduction processing on the light signal;

[0011] The signal processing module is used to process the echo signal output by the receiving module, obtain the real-time rain echo intensity value and the corresponding point cloud signal based on the echo signal of laser beam A, and then remove the real-time rain echo intensity value and the corresponding point cloud signal from the echo signal of laser beam B.

[0012] The ranging module is used to calculate the distance between the effective target and the vehicle based on the information output by the signal processing module.

[0013] Furthermore, the laser emission module includes an optical phased array lidar chip and three tunable lasers and three lens groups respectively connected to the optical phased array lidar chip; the three tunable lasers are used to control the output of laser beams with different wavelengths and emission powers; the three lens groups are used to control the output of laser beams with different emission distances.

[0014] Furthermore, based on a pre-set numerical range, rainfall is divided into five levels: no rain, light rain, moderate rain, heavy rain, and torrential rain. Depending on the amount of rainfall, a larger amount of rainfall corresponds to a laser beam A with a longer wavelength and lower power, and the emission distance of laser beam A remains unchanged under different amounts of rainfall. Depending on the amount of rainfall, a larger amount of rainfall corresponds to a laser beam B with a longer wavelength, higher power, and longer emission distance.

[0015] Furthermore, in the laser emission module, the emission wavelength ranges of the three tunable lasers are 532-540nm, 1064-1070nm, and 1550-1560nm, respectively, and the emission powers are 10mW, 20mW, 30mW, and 40mW, respectively. The emission distances controlled by the three lens groups are 50m, 100m, and 150m, respectively.

[0016] Furthermore, for laser beam A: when the rainfall level is light rain, adjustable laser one and lens group one are selected to achieve an emission wavelength of 532-540nm, an emission power of 40mw, and an emission distance of 50m; when the rainfall level is moderate rain, adjustable laser one and lens group one are selected to achieve an emission wavelength of 532-540nm, an emission power of 30mw, and an emission distance of 50m; when the rainfall level is heavy rain, adjustable laser two and lens group one are selected to achieve an emission wavelength of 1064-1070nm, an emission power of 20mw, and an emission distance of 50m; when the rainfall level is torrential rain, adjustable laser two and lens group one are selected to achieve an emission wavelength of 1064-1070nm, an emission power of 10mw, and an emission distance of 50m.

[0017] For laser beam B: When the rainfall level is light rain, select adjustable laser two and lens group one to achieve an emission wavelength of 1064-1070nm, an emission power of 10mw, and an emission distance of 50m; when the rainfall level is moderate rain, select adjustable laser two and lens group two to achieve an emission wavelength of 1064-1070nm, an emission power of 20mw, and an emission distance of 100m; when the rainfall level is heavy rain, select adjustable laser three and lens group two to achieve an emission wavelength of 1550-1560nm, an emission power of 30mw, and an emission distance of 100m; when the rainfall level is torrential rain, select adjustable laser two and lens group three to achieve an emission wavelength of 1550-1560nm, an emission power of 40mw, and an emission distance of 150m.

[0018] Furthermore, the receiving module includes an optical collimating lens group, a background light denoising module, and a signal amplification circuit;

[0019] The optical collimating lens group is used to collimate the optical signals reflected back from laser beam A and laser beam B.

[0020] The background light denoising module includes a tunable filter, four photodetectors, first to third filters, and first to fourth control switches. The four photodetectors are arranged side by side, with a filter installed at the incident end of each of the first to third photodetectors. The signal output ends of the first to fourth photodetectors are connected to the input end of the tunable filter via a control switch. The first to third filters correspond to wavelengths of 532-540nm, 1064-1070nm, and 1550-1560nm, respectively. The first to fourth control switches are controlled to open and close by the main control module. When open, the tunable filter can receive the signal output from the corresponding photodetector.

[0021] Specifically, during the interval between adjacent emission cycles of the laser beam, the fourth control switch connected to the fourth photodetector is turned on, while the first to third control switches are turned off. At this time, the signal output by the fourth photodetector only includes the background light noise signal. Then, according to the wavelengths of laser beam A and laser beam B emitted in the next emission cycle, the main control module turns on the control switches connected to the photodetectors corresponding to the same wavelength filters according to the laser beam emission time. That is, through the action of the filters and switches, only the detection echo signal of the corresponding band and the background light noise signal of that band can be input to the tunable filter. The tunable filter removes the signal in the same band as the output signal of the fourth photodetector from the output signals of the first to third photodetectors. This signal in the same band is the background light noise signal in the same band as laser beam A or laser beam B, thereby achieving the effect of removing background light noise.

[0022] The signal amplification circuit is used to reshape and amplify the electrical signal after removing background light noise.

[0023] Furthermore, the signal processing module includes a signal calculation unit and a unit for filtering useless echo signals;

[0024] The signal calculation unit is used to calculate the quantized intensity value of each point cloud signal in the remaining echo signal after background light denoising based on the output signal of the receiving module;

[0025] The unit for filtering useless echo signals is used to process the output results of the signal calculation unit as follows:

[0026] Step 1: Compare the quantized intensity value of the echo point cloud signal of laser beam A after calculation and processing by the signal calculation unit with the value range in the rain echo intensity database;

[0027] Step 2: Remove all intensity values ​​and corresponding point cloud signals that are outside the range of rain echo intensity values;

[0028] Step 3: Save the intensity values ​​of the remaining point cloud signals and record them as real-time rain echo intensity values;

[0029] Step 4: Compare the quantized intensity value of the echo point cloud signal of the laser beam B after calculation and processing by the signal calculation unit with the real-time rain echo intensity value, and remove the values ​​in the echo signal that are the same as the real-time rain echo intensity value and the corresponding point cloud signals.

[0030] The rain echo intensity database stores rain echo intensity values ​​obtained in advance by the vehicle-mounted lidar system under different rainfall intensities, with the laser at different emission wavelengths, emission powers, and emission distances.

[0031] Furthermore, it also includes an image generation module, used to integrate information from effective point cloud signals based on the output signal of the signal processing module to form an image.

[0032] Furthermore, the image generation module includes an effective target discrimination module, a point cloud data integration module, and an imaging module;

[0033] The target discrimination module is used to classify and determine several valid targets based on the direction, angle and intensity values ​​of each received point cloud signal;

[0034] The point cloud data integration module is used to integrate the intensity value and the distance information of the effective target;

[0035] The imaging module is used to process the integrated point cloud data and finally display the image and distance on the display screen.

[0036] Beneficial Effects: This invention detects rainfall in rainy weather and adjusts the configuration parameters of the laser emission module accordingly to achieve periodic alternating emission of laser beam A and laser beam B. This allows laser beams A and B to better detect their respective useful targets under different rainfall levels, generating sufficient echo signals from the useful targets and ultimately providing the system with more accurate point cloud data. Next, the signal receiving and processing modules perform hierarchical processing on the clutter signals in the echo signals of laser beams A and B, ultimately obtaining a more accurate point cloud signal of the useful target from the echo signal generated by laser beam B. Finally, the ranging and image generation modules achieve clear imaging and accurate ranging of the useful target. This invention solves the problem of severe clutter interference in vehicle-mounted lidar systems during rainy weather. Attached Figure Description

[0037] Figure 1 This is a structural diagram of a vehicle-mounted lidar system suitable for rainy weather.

[0038] Figure 2 This is a schematic diagram of the OPA lidar chip structure;

[0039] Figure 3 This is a schematic diagram of the background light denoising system.

[0040] Figure 4 The flowchart shows the module for filtering useless echo signals. Detailed Implementation

[0041] The invention will now be further explained with reference to the accompanying drawings.

[0042] like Figure 1As shown, a vehicle-mounted LiDAR system suitable for rainy weather includes: a display screen, a main control module, a rain sensor, a laser emitting module, a receiving module, a signal processing module, a ranging module, and an image generation module. The laser emitting module includes a tunable laser, an optical phased array (OPA) LiDAR chip, and a voltage control module. The receiving module includes an optical collimating lens group, a background light denoising module, and a signal amplification module. The signal processing module includes a signal calculation unit and a unit for filtering unwanted echo signals. The ranging module includes a microsecond timer and a ranging system. The image generation module includes an effective target discrimination module, a point cloud data integration module, and an imaging module.

[0043] like Figure 2 As shown, the OPA lidar chip includes a coupler, an MMI beam splitter, 1×N electro-optic switches S1, 1×M electro-optic switches S2, N electro-optic phase shifter groups 1, M electro-optic phase shifter groups 2, and a grating antenna. The output of the coupler is connected to the input of the MMI beam splitter, and the output of the MMI beam splitter is connected to the inputs of the 1×N electro-optic switches S1 and the 1×M electro-optic switches S2, respectively. The 1×N electro-optic switches S1 and the N electro-optic phase shifter groups 1 are adjusted to the same waveguide group, emitting laser beam A through the grating antenna; the 1×M electro-optic switches S2 and the M electro-optic phase shifter groups 2 are adjusted to the same waveguide group, emitting laser beam B through the grating antenna.

[0044] The vehicle-mounted LiDAR system is activated via the display screen. Upon receiving the activation signal, the main control module turns on the rain sensor. The rain sensor detects the current real-time rainfall and determines the rainfall level. Based on a pre-set range, the rainfall is categorized into five levels: no rain, light rain, moderate rain, heavy rain, and torrential rain.

[0045] The main control module adjusts the laser emission module according to the current rainfall level. Specifically, the main control module applies different voltages to the 1×N-channel electro-optic switch S1 and the 1×M-channel electro-optic switch S2 through the control voltage control module. The two electro-optic switches are in an alternating open and closed state. Within one emission cycle, the open time of switches S1 and S2 is 50μs each, that is, laser beam A and laser beam B are emitted alternately for 50μs each; the interval between adjacent emission cycles is 10μs.

[0046] The main control module adjusts the phase of N electro-optic phase shifter groups 1 and M electro-optic phase shifter groups 2 through the control voltage control module, so that the scanning direction and scanning range of laser beam A and laser beam B are different. For laser beam A, the main scanning area is the area diagonally above the vehicle, and the main target of scanning is the real-time falling raindrops. For laser beam B, the main scanning area is the area in front of the vehicle, including the left and right front areas, and the target of scanning is the real-time road conditions in front of the vehicle.

[0047] Laser beams of different wavelengths, emission powers, and emission distances are emitted under different rainfall levels, resulting in varying backscattering and penetration coefficients of raindrops. Based on the different functions of laser beams A and B, appropriate parameter configurations are selected for each under different rainfall conditions. Specifically, the emission power, wavelength, and emission distance of laser beams A and B are controlled according to the rainfall level. For heavy rainfall, laser beam A with a longer wavelength and lower power is output, while the emission distance of laser beam A remains constant under different rainfall levels. Conversely, for heavy rainfall, laser beam B with a longer wavelength, higher power, and longer emission distance is output. When there is no rain, the 1×N-channel electro-optical switch S1 is closed, and only the 1×M-channel electro-optical switch S2 is open.

[0048] Preferably, in the laser emission module, the emission wavelength ranges of the three tunable lasers are 532-540nm, 1064-1070nm, and 1550-1560nm, respectively, and the emission powers are 10mW, 20mW, 30mW, and 40mW, respectively. The emission distances controlled by the three lens groups are 50m, 100m, and 150m, respectively.

[0049] For laser beam A: When the rainfall level is light rain, select adjustable laser one and lens group one to achieve an emission wavelength of 532-540nm, an emission power of 40mw, and an emission distance of 50m; when the rainfall level is moderate rain, select adjustable laser one and lens group one to achieve an emission wavelength of 532-540nm, an emission power of 30mw, and an emission distance of 50m; when the rainfall level is heavy rain, select adjustable laser two and lens group one to achieve an emission wavelength of 1064-1070nm, an emission power of 20mw, and an emission distance of 50m; when the rainfall level is torrential rain, select adjustable laser two and lens group one to achieve an emission wavelength of 1064-1070nm, an emission power of 10mw, and an emission distance of 50m.

[0050] For laser beam B: When the rainfall level is light rain, select adjustable laser two and lens group one to achieve an emission wavelength of 1064-1070nm, an emission power of 10mw, and an emission distance of 50m; when the rainfall level is moderate rain, select adjustable laser two and lens group two to achieve an emission wavelength of 1064-1070nm, an emission power of 20mw, and an emission distance of 100m; when the rainfall level is heavy rain, select adjustable laser three and lens group two to achieve an emission wavelength of 1550-1560nm, an emission power of 30mw, and an emission distance of 100m; when the rainfall level is torrential rain, select adjustable laser two and lens group three to achieve an emission wavelength of 1550-1560nm, an emission power of 40mw, and an emission distance of 150m.

[0051] The receiving module receives the optical signals reflected from laser beams A and B. The optical collimating lens group of the receiving module is used to collimate the received optical signals.

[0052] like Figure 3 As shown, the background light denoising module comprises four parts: a tunable filter, four photodetectors, first to third filters 3-5, and first to fourth control switches 6-9. Specifically, the four photodetectors are arranged side by side, with a filter installed at the incident end of each of the first to third photodetectors. The signal output ends of the first to fourth photodetectors are each connected to the input end of the tunable filter via a control switch. The first to third filters 3-5 correspond to wavelengths of 532-540nm, 1064-1070nm, and 1550-1560nm, respectively. The first to fourth control switches 6-9 can be controlled to open and close by the main control module. When open, the tunable filter can receive the signals output by the corresponding photodetectors.

[0053] Specifically, during the interval between adjacent laser beam emission cycles, the fourth control switch 9 is turned on, while the first to third control switches 6-8 are turned off. At this time, the signal output by the fourth photodetector only includes background noise. Then, the main control module, based on the wavelengths of laser beams A and B emitted in the next emission cycle, turns on the control switches connected to the photodetectors corresponding to the same wavelength filters according to the laser beam emission time. That is, through the action of the filters and switches, only the detection echo signal of the corresponding band and the background noise signal of that band can be input to the tunable filter. The tunable filter removes the signal in the same band as the output signal of the fourth photodetector from the output signals of the first to third photodetectors. This same band signal is the background noise signal in the same band as laser beam A or laser beam B, thus achieving the effect of removing background noise.

[0054] The signal amplification circuit of the receiving module will reshape and amplify the electrical signal after removing background light noise.

[0055] The signal calculation unit of the signal processing module is used to calculate the remaining echo signal after the background light noise has been removed and the signal amplification circuit has been processed, and then obtains the quantized intensity value of each point cloud signal in the remaining echo signal.

[0056] Since laser beam A and laser beam B are emitted in a periodic alternating state, the signal calculation unit also alternately outputs the processed echo signals of laser beam A and laser beam B. For example... Figure 4 As shown, the useless echo signal filtering unit is used to remove the remaining clutter signals from the echo signals of laser beam A and laser beam B, respectively. The specific steps are as follows:

[0057] Step 1: Compare the quantized intensity value of the echo point cloud signal of laser beam A after calculation and processing by the signal calculation unit with the value range in the rain echo intensity database;

[0058] Step 2: Remove all intensity values ​​and corresponding point cloud signals that are outside the range of rain echo intensity values;

[0059] Step 3: Save the intensity values ​​of the remaining point cloud signals and record them as real-time rain echo intensity values;

[0060] Step 4: Compare the quantized intensity value of the echo point cloud signal of the laser beam B after calculation and processing by the signal calculation unit with the real-time rain echo intensity value, and remove the values ​​in the echo signal that are the same as the real-time rain echo intensity value and the corresponding point cloud signals.

[0061] The rain echo intensity database 10 is derived from continuous testing of this lidar system under ideal conditions, including rainfall intensities of light, moderate, heavy, and torrential rain, with laser emission wavelengths of 532-540nm, 1064-1070nm, and 1550-1560nm; emission powers of 10mW, 20mW, 30mW, and 40mW; and laser beam emission distances through the lens group of 50m, 100m, and 150m. It represents a relatively accurate range of quantified rain echo intensity values.

[0062] The ranging module includes a microsecond timer and a ranging system. The microsecond timer records the time interval t{t1,t2,...,t3} from the emission of laser beam B to the acquisition of the point cloud signals of each effective target. n The ranging module calculates the distance S between the vehicle and each target that forms a valid point cloud signal based on the order in which they arrive. t0 is the time required for the light signal to travel through the receiving and processing modules. The formula is: S = V * (t - t0) / 2, where V is the speed of light. The image generation module first uses the valid target discrimination module to classify the received point cloud signals into several valid targets based on their direction, angle, and quantization intensity value. The data integration module integrates the intensity values ​​and the distance information of the valid targets. The final imaging module processes the integrated point cloud data to produce a clear image and accurate distance on the display screen.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A vehicle-mounted lidar system suitable for rainy weather, characterized in that, include: Rain sensor, laser emitting module, receiving module, signal processing module, ranging module; The rain sensor is used to detect the current amount of rainfall and determine the rainfall level. The laser emitting module is used to periodically emit two different laser beams alternately. The target of laser beam A is the raindrops falling in real time, and the target of laser beam B is the road conditions in front of the vehicle in real time. The emission power, wavelength and emission distance of laser beam A and laser beam B are controlled according to the level of rainfall. The receiving module is used to receive the light signal reflected back from the laser beam and to perform background light noise reduction processing on the light signal; The signal processing module is used to process the echo signal output by the receiving module, obtain the real-time rain echo intensity value and the corresponding point cloud signal based on the echo signal of laser beam A, and then remove the real-time rain echo intensity value and the corresponding point cloud signal from the echo signal of laser beam B. The ranging module is used to calculate the distance between the effective target and the vehicle based on the information output by the signal processing module; Based on a pre-set numerical range, rainfall is divided into five levels: no rain, light rain, moderate rain, heavy rain, and torrential rain. Depending on the amount of rainfall, a larger amount of rainfall corresponds to a laser beam A with a longer wavelength and lower power, and the transmission distance of laser beam A remains unchanged under different amounts of rainfall. Depending on the amount of rainfall, a larger amount of rainfall corresponds to a laser beam B with a longer wavelength, higher power, and longer transmission distance.

2. The vehicle-mounted lidar system suitable for rainy weather according to claim 1, characterized in that, The laser emission module includes an optical phased array lidar chip and three tunable lasers and three lens groups respectively connected to the optical phased array lidar chip; the three tunable lasers are used to control the output of laser beams with different wavelengths and emission powers; the three lens groups are used to control the output of laser beams with different emission distances.

3. The vehicle-mounted lidar system suitable for rainy weather according to claim 2, characterized in that, In the laser emission module, the emission wavelength ranges of the three tunable lasers are 532-540nm, 1064-1070nm, and 1550-1560nm, respectively, and the emission powers are 10mW, 20mW, 30mW, and 40mW, respectively. The emission distances controlled by the three lens groups are 50m, 100m, and 150m, respectively.

4. The vehicle-mounted lidar system suitable for rainy weather according to claim 3, characterized in that, For laser beam A: When the rainfall level is light rain, select adjustable laser one and lens group one to achieve an emission wavelength of 532-540nm, an emission power of 40mw, and an emission distance of 50m; when the rainfall level is moderate rain, select adjustable laser one and lens group one to achieve an emission wavelength of 532-540nm, an emission power of 30mw, and an emission distance of 50m; when the rainfall level is heavy rain, select adjustable laser two and lens group one to achieve an emission wavelength of 1064-1070nm, an emission power of 20mw, and an emission distance of 50m; when the rainfall level is torrential rain, select adjustable laser two and lens group one to achieve an emission wavelength of 1064-1070nm, an emission power of 10mw, and an emission distance of 50m. For laser beam B: When the rainfall level is light rain, select adjustable laser two and lens group one to achieve an emission wavelength of 1064-1070nm, an emission power of 10mw, and an emission distance of 50m; when the rainfall level is moderate rain, select adjustable laser two and lens group two to achieve an emission wavelength of 1064-1070nm, an emission power of 20mw, and an emission distance of 100m; when the rainfall level is heavy rain, select adjustable laser three and lens group two to achieve an emission wavelength of 1550-1560nm, an emission power of 30mw, and an emission distance of 100m; when the rainfall level is torrential rain, select adjustable laser two and lens group three to achieve an emission wavelength of 1550-1560nm, an emission power of 40mw, and an emission distance of 150m.

5. The vehicle-mounted lidar system suitable for rainy weather according to claim 4, characterized in that, The receiving module includes an optical collimating lens group, a background light denoising module, and a signal amplification circuit; The optical collimating lens group is used to collimate the optical signals reflected back from laser beam A and laser beam B. The background light noise reduction module includes a tunable filter, four photodetectors, first to third filters, and first to fourth control switches; Four photodetectors are arranged side by side. Each of the first to third photodetectors has a filter at its incident end. The signal outputs of the first to fourth photodetectors are connected to the input of a tunable filter via a control switch. The first to third filters correspond to wavelengths of 532-540nm, 1064-1070nm, and 1550-1560nm, respectively. The first to fourth control switches are controlled to open and close by the main control module. When open, the tunable filter can receive the signals output by the corresponding photodetector. Specifically, during the interval between adjacent emission cycles of the laser beam, the fourth control switch connected to the fourth photodetector is turned on, while the first to third control switches are turned off. At this time, the signal output by the fourth photodetector only includes the background light noise signal. Then, according to the wavelengths of laser beam A and laser beam B emitted in the next emission cycle, the main control module turns on the control switches connected to the photodetectors corresponding to the same wavelength filters according to the laser beam emission time. That is, through the action of the filters and switches, only the detection echo signal of the corresponding band and the background light noise signal of that band can be input to the tunable filter. The tunable filter removes the signal in the same band as the output signal of the fourth photodetector from the output signals of the first to third photodetectors. This signal in the same band is the background light noise signal in the same band as laser beam A or laser beam B, thereby achieving the effect of removing background light noise. The signal amplification circuit is used to reshape and amplify the electrical signal after removing background light noise.

6. The vehicle-mounted lidar system suitable for rainy weather according to any one of claims 1-5, characterized in that, The signal processing module includes a signal calculation unit and a unit for filtering useless echo signals; The signal calculation unit is used to calculate the quantized intensity value of each point cloud signal in the remaining echo signal after background light denoising based on the output signal of the receiving module; The unit for filtering useless echo signals is used to process the output results of the signal calculation unit as follows: Step 1: Compare the quantized intensity value of the echo point cloud signal of laser beam A after calculation and processing by the signal calculation unit with the value range in the rain echo intensity database; Step 2: Remove all intensity values ​​and corresponding point cloud signals that are outside the range of rain echo intensity values; Step 3: Save the intensity values ​​of the remaining point cloud signals and record them as real-time rain echo intensity values; Step 4: Compare the quantized intensity value of the echo point cloud signal of the laser beam B after calculation and processing by the signal calculation unit with the real-time rain echo intensity value, and remove the values ​​in the echo signal that are the same as the real-time rain echo intensity value and the corresponding point cloud signals. The rain echo intensity database stores rain echo intensity values ​​obtained in advance by the vehicle-mounted lidar system under different rainfall intensities, with the laser at different emission wavelengths, emission powers, and emission distances.

7. The vehicle-mounted lidar system suitable for rainy weather according to any one of claims 1-5, characterized in that, It also includes an image generation module, which is used to integrate the information of the effective point cloud signal into an image based on the signal output by the signal processing module.

8. The vehicle-mounted lidar system suitable for rainy weather according to claim 7, characterized in that, The image generation module includes an effective target discrimination module, a point cloud data integration module, and an imaging module; The target discrimination module is used to classify and determine several valid targets based on the direction, angle and intensity values ​​of each received point cloud signal; The point cloud data integration module is used to integrate the intensity value and the distance information of the effective target; The imaging module is used to process the integrated point cloud data and finally display the image and distance on the display screen.

Images