A method and system for receiving echoes with a large dynamic range in a lidar, and a lidar

Abstract

The present invention provides a method and system for receiving echoes with a large dynamic range by a lidar, and a lidar. The method includes the following steps: S1. The radar receiver receives the laser echo signal reflected by the object to be measured, amplifies the laser echo signal with three different gain levels to obtain three amplified echo signals, and splices the three amplified echo signals by using an accumulative splicing algorithm to obtain a laser echo input signal; S2. Smoothly filter the laser echo input signal to obtain a smooth laser echo signal; S3. Extract the optimal laser echo from the smooth laser echo signal; wherein, the peak detection algorithm is used to confirm the first laser echo and the last laser echo; obtain the fitting function, perform fitting processing on the fitting function by using the least squares method, and then decompose the optimal laser echo signal by using the least squares fitting algorithm. The present invention can achieve detection within a large dynamic range at a long distance and has high detection accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of lidar, and more particularly, to a method and system for receiving lidar echoes with a large dynamic range and a lidar. Background Art

[0002] A lidar is a radar system that detects the position, speed, and other characteristic quantities of a target by emitting a laser beam, and is composed of a laser transmitter, an optical receiver, and an information processing system, etc. Its working principle is to emit a laser beam towards the target, and then compare the received signal reflected from the target with the transmitted signal. After appropriate processing, relevant information about the target can be obtained, such as parameters of the target distance, azimuth, altitude, speed, attitude, and shape, etc.

[0003] Lidar can be classified into near-sensing lidar and long-distance lidar according to the measurement distance. The long-distance lidar mainly detects long-distance objects. However, in actual measurements, the objects detected at long distances may also have different distance positions (i.e., large dynamic range at long distances). When the reflected echo signals are at different distances, the laser energy also differs by several orders of magnitude. According to the distance of the detected object, the receiver amplifies the echo signal differently. When measuring a near-distance target, the echo energy is strong, and the amplitude of the converted electrical pulse is high. Excessive gain will cause the amplifier to saturate. After the amplifier saturates, the recovery time is long. When measuring a long-distance target, the echo energy is low, and the converted electrical pulse signal is weak. Therefore, the present application proposes a method and system for receiving lidar echoes with a large dynamic range and a lidar to solve the above-mentioned technical problems of echo signal methods. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and system for receiving lidar echoes with a large dynamic range and a lidar, which solve the above technical problems.

[0005] The embodiments of the present invention are implemented through the following technical solutions:

[0006] In a first aspect, a method for receiving lidar echoes with a large dynamic range is proposed, including the following steps:

[0007] S1. The radar receiver receives the laser echo signal reflected by the object to be measured, amplifies the laser echo signal with three different gain levels according to the gain parameters of the variable gain amplifier to obtain three amplified echo signals, and splices the three amplified echo signals using an accumulative splicing algorithm to splice and obtain the laser echo input signal;

[0008] S2. Smoothly filter the laser echo input signal to obtain a smooth laser echo signal;

[0009] S3. Extract the optimal laser echo from the smoothed laser echo signal; among them, the peak detection algorithm is used to confirm the first laser echo and the last laser echo; a fitting function is obtained according to the first laser echo and the last laser echo, and the least squares method is used to fit the fitting function, and then the least squares fitting algorithm is used to decompose the optimal laser echo signal.

[0010] Preferably, the S1 specifically includes the following steps:

[0011] S11. Receive the laser echo signal and perform the first-stage amplification using a transimpedance amplifier;

[0012] S12. Use the high-gain parameter, medium-gain parameter, and low-gain parameter of the variable gain amplifier to establish a high-gain amplification branch, a medium-gain amplification branch, and a low-gain amplification branch respectively. Input the laser echo signal after the first-stage amplification into the high-gain amplification branch, the medium-gain amplification branch, and the low-gain amplification branch respectively for the second-stage amplification to obtain three amplified echo signals;

[0013] S13. Input the three echo signals into the ADC chip for quantization processing to obtain the high-gain quantization code value, the medium-gain quantization code value, and the low-gain quantization code value;

[0014] S14. Use the acquisition accumulation splicing algorithm to calculate the high-gain quantization code value, the medium-gain quantization code value, and the low-gain quantization code value to obtain the final code value and the laser echo input signal corresponding to the final code value.

[0015] Preferably, the accumulation splicing algorithm includes the following steps:

[0016] A. Judge whether the high-gain code value overflows; if not, output the high-gain code value as the final code value; if it overflows, enter step B;

[0017] B. Judge whether the medium-gain code value overflows; if not, accumulate the medium-gain code value on the high-gain code value and subtract the code value when the level is 0 to obtain a new medium-gain code value and enter step C;

[0018] C. Judge whether the new medium-gain code value overflows; if not, output the new medium-gain code value as the final code value; if it overflows, enter step D;

[0019] D. Judge whether the low-gain code value overflows; if not, accumulate the low-gain code value on the new medium-gain code value and subtract the code value when the level is 0 to obtain a new low-gain code value and enter step E;

[0020] E. Output the new low-gain code as the final code value.

[0021] Preferably, the S2 uses a Savitzky-Golay algorithm to implement smoothing filtering.

[0022] Preferably, the peak detection algorithm is specifically:

[0023] A. Determine the data length of the effective smoothed laser echo signal according to the range to be measured;

[0024] B. Extract useful data of the waveform according to the distance between the laser radar and the ground and the data length;

[0025] C. Detecting peaks in useful data; specifically, setting pulse width conditions, and detecting peaks that meet the pulse width conditions in useful data;

[0026] D. Filter the peaks whose amplitude is less than 5 times the noise amplitude, mark the peak with the largest amplitude among all the detected peaks as the first laser echo, and the peak with the largest time as the last laser echo.

[0027] Preferably, the fitting function is:

[0028] R(t)=G(t;A s ,μ s ,σ s )+Q(t;a,b,c,d,e,g,h,f)+G(t;A b ,μ b ,σ b );in

[0029]

[0030]

[0031]

[0032] Specifically, the Gaussian function is used to fit the first laser echo and the last laser echo, and the pentagonal function is used to fit the echo. s ,μ s ,σ S ) represents the first laser echo signal simulated by Gaussian function, G(t; A b ,μ b ,σ b ) represents the final laser echo signal simulated by Gaussian function, A s , μ s and σ s Respectively represent the amplitude, mean and standard deviation of the Gaussian function of the first laser echo signal; A b , μ b and σ brespectively represent the amplitude, mean, and standard deviation of the Gaussian function of the end laser echo signal. a, b, c, d, and f respectively represent the abscissas of the five corners in the pentagon function, and e, g, and h respectively represent the ordinates corresponding to the three vertices in the nonagon function.

[0033] In a second aspect, a lidar large dynamic range echo receiving system is provided, including a receiver and an FPGA chip. An ADC chip and a variable gain amplifier are provided in the receiver. The FPGA chip includes an external component configuration module, a timing control module, a first buffer module, a second buffer module, a splicing processing module, and a peak detection module. Among them,

[0034] The external component configuration module is used to configure the clock chip device, ADC chip, and variable gain amplifier outside the FPGA chip.

[0035] The timing control module is used to change the working state of the FPGA chip according to the reset signal and the synchronization signal.

[0036] The first buffer module is used to store the quantization code values from the ADC chip.

[0037] The second buffer module is used to store the effective laser echo signals received by the receiver.

[0038] The splicing processing module calculates the laser echo input signal according to the accumulative splicing algorithm.

[0039] The peak detection module uses the peak detection algorithm to confirm the first laser echo and the end laser echo.

[0040] In a third aspect, a lidar is provided, including a transmitter, a receiver, and an FPGA chip. The FPGA chip is respectively communicatively connected to the transmitter and the receiver.

[0041] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects;

[0042] This application reasonably uses a variable gain amplifier to perform gain amplification on the input laser echo signal according to different gain levels of the variable gain amplifier, and then accumulatively splices the three amplified echo signals through the accumulative splicing algorithm. The laser echo input signal can correctly input the weak laser echo in the large dynamic range signal.

[0043] The present invention is reasonably designed, has a simple structure, and strong practicability. Description of the Drawings

[0044] Figure 1 It is a schematic flowchart of the lidar large dynamic range echo receiving method provided by Embodiment 1 of the present invention. Detailed implementation mode

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Generally, the components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0046] Embodiment 1

[0047] In a first aspect, a method for receiving large dynamic range echo of a lidar is proposed, including the following steps:

[0048] S1. The radar receiver receives the laser echo signal reflected by the object to be measured, amplifies the laser echo signal with three different gain levels according to the gain parameters of the variable gain amplifier to obtain three amplified echo signals, and splices the three amplified echo signals using an accumulative splicing algorithm to obtain the laser echo input signal. The variable gain amplifier can adjust the gain according to the distance of the object to be measured, and can more accurately receive the laser echo signal.

[0049] Specifically, the S1 includes the following steps:

[0050] S11. Receive the laser echo signal and perform the first-stage amplification using a transimpedance amplifier;

[0051] S12. Use the high-gain parameter, medium-gain parameter, and low-gain parameter of the variable gain amplifier to establish a high-gain amplification branch, a medium-gain amplification branch, and a low-gain amplification branch respectively, and input the laser echo signal after the first-stage amplification into the high-gain amplification branch, the medium-gain amplification branch, and the low-gain amplification branch respectively for the second-stage amplification to obtain three amplified echo signals respectively.

[0052] In this embodiment, the high-gain parameter is 100 times, the medium-gain parameter is 10 times, and the low-gain parameter is 1 time.

[0053] S13. Input the three echo signals into the ADC chip for quantization processing respectively to obtain the high-gain quantization code value, the medium-gain quantization code value, and the low-gain quantization code value;

[0054] The three echo signals are respectively input into three ADC chips for quantization processing with a sampling rate of 2 GSPS, a quantization bit number of 8 bits, and a quantization of 700 mV, and the high-gain quantization code value, the medium-gain quantization code value, and the low-gain quantization code value are obtained respectively.

[0055] S14. The acquisition and accumulation splicing algorithm calculates the quantization code values of the high-gain level, medium-gain level, and low-gain level, and obtains the final code value and the laser echo input signal corresponding to the final code value.

[0056] The accumulation splicing algorithm includes the following steps:

[0057] A. Determine whether the high-gain level code value overflows; if not, output the high-gain level code value as the final code value; if it overflows, proceed to step B;

[0058] B. Determine whether the medium-gain level code value overflows; if not, accumulate the medium-gain level code value on the high-gain level code value, and subtract the code value at zero level to obtain the new medium-gain level code value and proceed to step C;

[0059] C. Determine whether the new medium-gain level code value overflows; if not, output the new medium-gain level code value as the final code value; if it overflows, proceed to step D;

[0060] D. Determine whether the low-gain level code value overflows; if not, accumulate the low-gain level code value on the new medium-gain level code value, and subtract the code value at zero level to obtain the new low-gain level code value and proceed to step E;

[0061] E. Output the new low-gain level code as the final code value.

[0062] In the accumulation splicing algorithm, considering that when the level is zero, the code value corresponds to the code value at zero level or 128, so 127 or 128 will be subtracted during the accumulation calculation.

[0063] In this application, since the variable gain amplifier can adjust the gain, the accumulation splicing algorithm of this application does not consider the situation where the high-gain level code value, medium-gain level code value, and low-gain level code value overflow simultaneously.

[0064] The method of parallel processing and amplification of the high-gain level amplification branch, medium-gain level amplification branch, and low-gain level amplification branch enables one of the processing circuits to correctly receive the echo signal with unknown amplitude, effectively improving the system's ability to receive and process signals with a large dynamic range, thereby expanding the maximum detection depth of the system. In subsequent processing, the accumulation splicing algorithm is independent of the actual amplification factor and does not need to be adjusted according to the actual amplification factor. It is applicable to parallel processing circuits with different gain combinations, effectively utilizes the advantages of the three-way parallel data, and the spliced waveform can clearly represent the laser echo, well retaining the relative magnitudes between data points. Therefore, the accumulation splicing algorithm can correctly output the weak laser echo in the large dynamic range signal, and the spliced waveform is suitable for the subsequent algorithm to extract and process the laser echo signal, helping to improve the measurement accuracy.

[0065] S2. Smoothly filter the laser echo input signal to obtain a smoothed laser echo signal.

[0066] In S2, the Savitzky-Golay algorithm is used to implement the smoothing filter.

[0067] In other embodiments of the present application, the moving algorithm or the lowess algorithm can also be used for smoothing filtering.

[0068] S3. Extract the optimal laser echo from the smoothed laser echo signal; among them, the peak detection algorithm is used to confirm the first laser echo and the last laser echo; a fitting function is obtained based on the first laser echo and the last laser echo, and the least squares method is used to perform fitting processing on the fitting function, and then the least squares fitting algorithm is used to decompose the optimal laser echo signal.

[0069] The specific peak detection algorithm is as follows:

[0070] A. Determine the data length of the effective smoothed laser echo signal according to the range to be measured;

[0071] B. Extract the useful data of the waveform according to the distance between the lidar and the ground and the data length;

[0072] C. Detect the wave peaks within the useful data; specifically, set the pulse width condition, and within the useful data, detect the wave peaks that meet the pulse width condition; the pulse width condition is: set a minimum period of a wave peak according to the pulse half-peak width of the smoothed laser echo signal. When the sampling point reaches half of the local maximum value, calculate the number difference between the sampling point and the local maximum value. If the number difference is greater than half of the minimum period, it is considered that the currently detected wave peak meets the pulse width condition.

[0073] D. Filter out the wave peaks with an amplitude less than 5 times the noise amplitude, and mark the wave peak with the largest amplitude among all the detected wave peaks as the first laser echo, and the wave peak with the largest time as the last laser echo.

[0074] The fitting function is:

[0075] R(t) = G(t; A s , μ s , σ s ) + Q(t; a, b, c, d, e, g, h, f) + G(t; A b , μ b , σ b ); where

[0076]

[0077]

[0078]

[0079] Specifically, the Gaussian function is used to fit the first laser echo and the last laser echo, and the pentagon function is used to fit the echo. G(t; A s , μ s , σ S ) represents the first laser echo signal simulated by the Gaussian function. G(t; A b , μ b , σ b ) represents the last laser echo signal simulated by the Gaussian function. A s , μ s , and σ s respectively represent the amplitude, mean value, and standard deviation of the Gaussian function of the first laser echo signal; A b , μ b , and σ b respectively represent the amplitude, mean value, and standard deviation of the Gaussian function of the last laser echo signal. a, b, c, d, and f respectively represent the abscissas of the five corners in the pentagon function, and e, g, and h respectively represent the ordinates corresponding to the three vertices in the pentagon function. The mean value μ s is considered as the first echo moment. The mean value μ b is considered as the echo moment of the last laser echo information.

[0080] When using the least squares method for fitting, the setting of the initial fitting values has a great influence on the fitting effect. Therefore, the maximum peak value in the detection result of the peak detection algorithm and its corresponding time are used as the initial values of the amplitude A s and the moment μ s of the first echo, and the maximum time and its corresponding peak value are used as the initial value of the moment μ b of the last echo and the amplitude A b .

[0081] Through the fitting process of the least squares method, the decomposition of the echo waveform can be realized, that is, the multi-echo signal of the lidar after fitting is obtained, and finally the data is fitted.

[0082] In the second aspect, a lidar large dynamic range echo receiving system is provided, including a receiver and an FPGA chip. An ADC chip and a variable gain amplifier are provided in the receiver. The FPGA chip includes an external component configuration module, a timing control module, a first buffer module, a second buffer module, a splicing processing module, and a peak detection module;

[0083] The FPGA chip needs to receive external control signals and parallel data output by three ADC chips, and at the same time, according to the external signals, realize the timing of data processing and the state transition of the circuit, etc., and finally output the calculation results.

[0084] Specifically, the external component configuration module is used to configure the clock chip device, ADC chip, and variable gain amplifier outside the FPGA chip; configure the clock chip device outside the FPGA to ensure that it outputs a high-performance clock of 1 GHz; configure the ADC chip to ensure that its sampling rate is 2 GSPS and outputs 32-bit data in parallel at a frequency of 500 MHz; configure the variable gain amplifier to ensure that its gain is adjustable to meet the system detection requirements. After the configuration is completed, it feeds back to the timing control module.

[0085] The timing control module is used to change the working state of the FPGA chip according to the reset signal and the synchronization signal; after receiving the reset signal and resetting, the FPGFA chip will automatically start the external component configuration module, and then enter the detection mode according to the configuration completion signal. At this time, the circuit will detect whether there is a laser electrical excitation signal. When the electrical excitation signal is detected, it means that the laser is working normally and laser is emitted, and the circuit starts to calculate the laser emission time and the return time. During the detection mode, when receiving the externally input synchronization signal (i.e., the laser echo signal), the currently calculated echo information will be output.

[0086] The first buffer module is used to store the quantization code values from the ADC chip; the first buffer module selects the first FIFO memory. Because the high-gain quantization code values, medium-gain quantization code values, and low-gain quantization code values are differentially input into the FPGA chip at a speed of 500 MHz and a bit width of 32 bits respectively. Therefore, it is necessary to use primitives inside the FPGA to convert the differential signal into a single-ended signal first, and then cache the data into the first FIFO under the drive of the synchronous output clock, that is, the write clock of the first FIFO is 500 MHz and the bit width is 32 bits. Since this module is only responsible for the reception and transmission of asynchronous data and is not used for the storage of useful data, in order not to waste storage resources, the read clock of the FIFO is set to 125 MHz and the bit width is 128 bits. In this application, there are respectively a high-gain amplification branch, a medium-gain amplification branch, and a low-gain amplification branch for parallel amplification, corresponding to the parallel quantization code values of three ADC chips. Correspondingly, three first FIFO memories should also be used to store data in parallel.

[0087] The second cache module is used to store the valid laser echo signals received by the receiver; the second FIFO memory is selected for the second cache module. The start time of the useful data is calculated based on the flight altitude, the electrical excitation signal of the laser, etc., and the cut-off time is determined according to the sounding range of the system. The signals received between the two times are considered as useful laser echo signals and are stored in this module. This module stores the useful data after the first-stage cache module. Therefore, the write clock of the FIFO is 125 MHz and the bit width is 128 bits. Since all the useful data required for calculating the elevation has been recorded, the read clock of the module can be adjusted according to the actual operating speed of the algorithm module, effectively reducing the requirement for the FPGA operating clock. Consistent with the first cache module, this module also has 3 channels for parallel processing with the same principle.

[0088] The splicing processing module calculates the laser echo input signal according to the accumulative splicing algorithm; the data splicing is completed by judging the code values of the three-way parallel data, and the spliced data is stored. The write speed of the storage module is the same as the read speed of the second cache module. Since the subsequent peak detection algorithm needs to judge the relative magnitudes between the waveform data, the data needs to be output serially. Therefore, the spliced data is stored in a simple dual-port RAM here, and the bit width is reduced to 8 bits when reading the data, realizing the parallel-to-serial data output for the peak detection algorithm module to index and receive the sampling points of the echo signal.

[0089] The peak detection module uses the peak detection algorithm to confirm the first laser echo and the last laser echo. The peak detection module is responsible for calculating the positions of the first laser echo and the last laser echo of the laser echo, and finally outputs the times of the first laser echo and the last laser echo for setting the initial values of the subsequent fitting algorithm. Since peak detection needs to judge the relative magnitudes between the front and back data points, the algorithm uses the form of serial input data, and at the same time uses the address of the RAM to locate the data, and finally obtains the position information representing the times of the first echo and the last echo. In this process, the start time of the algorithm is determined by the depth written inside the RAM, and a calculation completion signal is given after the calculation is completed.

[0090] In a third aspect, a lidar is provided, including a transmitter, a receiver and an FPGA chip, and the FPGA chip is communicatively connected to the transmitter and the receiver respectively.

[0091] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for receiving echoes with a large dynamic range of a lidar, characterized in that, It includes the following steps: S1. The radar receiver receives the laser echo signal reflected by the object to be measured, amplifies the laser echo signal with three different gain levels according to the gain parameters of the variable gain amplifier to obtain three amplified echo signals, and splices the three amplified echo signals using the accumulative splicing algorithm to obtain the laser echo input signal; S2. Smoothly filter the laser echo input signal to obtain the smoothed laser echo signal; S3. Extract the optimal laser echo from the smoothed laser echo signal; among them, use the peak detection algorithm to confirm the first laser echo and the last laser echo; obtain the fitting function according to the first laser echo and the last laser echo, perform fitting processing on the fitting function using the least squares method, and then use the least squares fitting algorithm to decompose the optimal laser echo signal; The specific peak detection algorithm is as follows: A. Determine the data length of the effective smoothed laser echo signal according to the measurement range; B. Extract the useful data of the waveform according to the distance between the lidar and the ground and the data length; C. Detect the peak within the useful data; specifically, set the pulse width condition, and within the useful data, detect the peak that satisfies the pulse width condition; the pulse width condition is: set a minimum period of a peak according to the pulse half-peak width of the smoothed laser echo signal. When the sampling point reaches half of the local maximum value, calculate the number difference between the sampling point and the local maximum value. If the number difference is greater than half of the minimum period, it is considered that the currently detected peak satisfies the pulse width condition; D. Filter out the peaks with amplitudes less than 5 times the noise amplitude, mark the peak with the largest amplitude among all detected peaks as the first laser echo, and the peak with the largest time as the last laser echo.

2. The method for receiving lidar echoes with a large dynamic range according to claim 1, wherein, The specific S1 includes the following steps: S11. Receive the laser echo signal and perform the first-stage amplification using a transimpedance amplifier; S12. Use the high-gain parameter, medium-gain parameter, and low-gain parameter of the variable gain amplifier to establish a high-gain amplification branch, a medium-gain amplification branch, and a low-gain amplification branch respectively. Input the laser echo signal after the first-stage amplification into the high-gain amplification branch, the medium-gain amplification branch, and the low-gain amplification branch respectively for the second-stage amplification to obtain three amplified echo signals; S13. Input the three echo signals into the ADC chip for quantization processing to obtain the high-gain quantization code value, the medium-gain quantization code value, and the low-gain quantization code value; S14. Use the accumulative splicing algorithm to calculate the high-gain quantization code value, the medium-gain quantization code value, and the low-gain quantization code value to obtain the final code value and the laser echo input signal corresponding to the final code value.

3. The method for receiving large dynamic range echoes of a lidar according to claim 2, wherein, The accumulative splicing algorithm includes the following steps: A. Determine whether the high-gain code value overflows; if it does not overflow, output the high-gain code value as the final code value; if it overflows, go to step B; B. Determine whether the medium-gain code value overflows; if it does not overflow, accumulate the medium-gain code value on the high-gain code value and subtract the code value when the level is 0 to obtain the new medium-gain code value and enter step C; C. Determine whether the new medium gain file code value overflows; if not, output the new medium gain file code value as the final code value, and if it overflows, proceed to step D; D. Determine whether the low gain file code value overflows; if not, accumulate the low gain file code value on the new medium gain file code value, and subtract the code value when the level is 0 to obtain the new low gain file code value and proceed to step E; E. Output the new low gain file code as the final code value.

4. The method for receiving large dynamic range echoes of a lidar according to claim 1, characterized in that The S2 uses the Savitzky-Golay algorithm to implement smoothing filtering.

5. The method for receiving lidar echoes with a large dynamic range according to claim 1, characterized in that The fitting function is: R(t) = G(t; A s , μ s , σ s ) + Q(t; a, b, c, d, e, g, h, f) + G(t; A b , μ b , σ b ); where Specifically, the Gaussian function is used to fit the first laser echo and the last laser echo, and the pentagon function is used to fit the echo. G(t; A s , μ s , σ S ) represents the first laser echo signal simulated by the Gaussian function. G(t; A b , μ b , σ b ) represents the last laser echo signal simulated by the Gaussian function. A s , μ s , and σ s respectively represent the amplitude, mean value, and standard deviation of the Gaussian function of the first laser echo signal; A b , μ b , and σ b respectively represent the amplitude, mean value, and standard deviation of the Gaussian function of the last laser echo signal. a, b, c, d, and f respectively represent the abscissas of the five corners in the pentagon function, and e, g, and h respectively represent the ordinates corresponding to the three vertices in the pentagon function.

6. A large dynamic range echo receiving system for lidar, which implements the large dynamic range echo receiving method for lidar as described in any one of claims 1-5, characterized in that, It includes a receiver and an FPGA chip. An ADC chip and a variable gain amplifier are provided in the receiver. The FPGA chip includes an external component configuration module, a timing control module, a first buffer module, a second buffer module, a splicing processing module, and a peak detection module; among them, The external component configuration module is used to configure the clock chip device, ADC chip, and variable gain amplifier outside the FPGA chip; The timing control module is used to change the working state of the FPGA chip according to the reset signal and the synchronization signal; The first buffer module is used to store the quantization code value from the ADC chip; The second buffer module is used to store the effective laser echo signal received by the receiver; The splicing processing module calculates the laser echo input signal according to the accumulative splicing algorithm; The peak detection module uses the peak detection algorithm to confirm the first laser echo and the last laser echo.

7. A lidar, characterized in that, It includes a transmitter and the receiver and FPGA chip as described in claim 6. The FPGA chip is communicatively connected to the transmitter and the receiver respectively.

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