Atmospheric attenuation compensation data processing system of long-distance laser radar

Abstract

The invention relates to the technical field of laser ranging and photoelectric detection, and discloses an atmospheric attenuation compensation data processing system for a long-distance laser radar, which comprises a signal acquisition module, a signal processing module and a signal processing module, an atmospheric parameter calculation module determines an atmospheric attenuation coefficient according to a signal segment amplitude attenuation slope, a gain control module adjusts a gain curve increase step length, a timing correction module determines a timing starting point offset according to the coefficient, and both gain adjustment and offset compensation respond to the atmospheric attenuation coefficient in real time; according to the invention, a transmissivity in-situ sensing mechanism is established by using a scattering background endogenous by a laser echo, waveform broadening and timing starting point offset caused by non-uniform distribution of a medium are eliminated, and distance measurement consistency and sensitivity are improved.

Description

Technical Field

[0001] This invention relates to an atmospheric attenuation compensation data processing system for long-range lidar, belonging to the field of laser ranging and photoelectric detection technology. Background Technology

[0002] Current laser rangefinders utilize the time-of-flight of laser pulses to acquire target position information and are widely used in autonomous driving and industrial measurement systems. However, the transmission of laser pulses in free space is affected by absorption and scattering by atmospheric aerosols, resulting in energy attenuation and pulse envelope broadening distortion. Maintaining the measurement range is a common practice that involves increasing the laser emission power or improving the detection sensitivity.

[0003] In environments with fluctuating visibility, increasing hardware gain can lead to detector saturation, which is limited by human eye safety power. For example, Chinese invention patent CN107167792A discloses an atmospheric laser communication device with ranging function and its ranging method. It adds a ranging crystal oscillator to the communication circuit and uses a mode selection switch to switch between communication and ranging states. The distance is determined by calculating the pulse round-trip time delay. The ranging process relies on preset fixed time delay parameters and requires manual or restricted switching of working modes. It cannot provide real-time perception and online compensation for dynamic time delays caused by system time base deviation, device aging temperature drift, and channel fluctuations under complex working conditions. This control approach, which lacks flexible adjustment capabilities, is slow to respond to high-frequency dynamic errors and cannot meet the strict requirements of real-time performance and adaptability for high-precision work. Post-processing correction of local parameters obtained from external meteorological sensors is an industry improvement path. However, since external monitoring data cannot characterize the instantaneous non-uniform medium distribution along the long-distance path of the laser pulse, and atmospheric scattering induces a slow rise edge of the waveform, causing the timing start point to shift, the measurement results fluctuate randomly at the centimeter or even decimeter level depending on the meteorological conditions.

[0004] Therefore, how to use the ranging system to receive the original waveform envelope to realize the in-situ inversion of transmission path characteristics, and to collaboratively complete dynamic energy compensation and timing deviation correction without relying on additional sensing hardware, has become the technical problem to be solved by this invention. Summary of the Invention

[0005] To address the problems mentioned in the background art, the technical solution of the present invention is as follows: A long-range lidar atmospheric attenuation compensation data processing system, comprising: The signal acquisition module acquires the raw waveform data output by the detector. The raw waveform data includes the target echo pulse and the backscattered signal before the target echo pulse arrives. The atmospheric parameter calculation module extracts the signal segment between the zero-range point and the target point from the original waveform data as the interface scattering signal flow, calculates the amplitude attenuation slope of the interface scattering signal flow over time, and determines the atmospheric attenuation coefficient of the laser propagation path based on the amplitude attenuation slope. The gain control module establishes a time-varying gain curve that increases non-linearly with the laser flight time. Based on the atmospheric attenuation coefficient, it adjusts the growth slope of the time-varying gain curve in real time to adjust the gain of the detector's subsequent amplifier circuit for the target echo pulse. The timing correction module identifies the rising edge characteristics of the target echo pulse, and determines the timing start offset based on the atmospheric attenuation coefficient and the slope of the rising edge characteristics through a preset nonlinear mapping rule, thereby correcting the original ranging result. The atmospheric parameter calculation module outputs the determined atmospheric attenuation coefficient to the gain control module and the timing correction module in real time. The adjustment of the time-varying gain curve by the gain control module and the determination of the timing start offset by the timing correction module are both in real time response to the change of atmospheric attenuation coefficient, forming a logical closed loop of environmental feature perception and measurement deviation correction within a single pulse sampling period.

[0006] Preferably, the atmospheric parameter calculation module extracts the local signal in the backscattered signal within a preset window before the trigger time of the rising edge of the target echo pulse, calculates the level change of the local signal relative to the average amplitude of the interface scattering signal flow, and inverts the local optical transmittance on the laser propagation path based on the level change, thereby correcting the atmospheric attenuation coefficient to eliminate the measurement error caused by the sudden change in medium concentration at the near target location.

[0007] Preferably, the atmospheric parameter calculation module includes: a sampling and statistics unit, which calculates the flip density of the least significant bit of the original waveform data within a preset time window. ,in, The ratio of the number of flips to the total number of samples; the waveform reconstruction unit, based on the flip density. Quantization step size of the detector analog-to-digital converter Recover the subquantized envelope curve The calculation formula is: Among them, the atmospheric parameter calculation module is based on the subquantized envelope curve. The atmospheric attenuation coefficient is determined by the gradient over time, and the intrinsic thermal noise of the detector is used to extract values ​​below the quantization step size. The amplitude characteristics of the scattered signal.

[0008] Preferably, it also includes an environmental noise monitoring module, which collects the detector's output signal during a preset time slot before laser pulse emission to obtain the intrinsic thermal reference. The offset stripping module acquires the real-time background noise signal from the original waveform data. Real-time background noise signal With intrinsic thermal standard Perform differential processing to extract the pure atmospheric scattering component. The atmospheric parameter calculation module is based on the pure atmospheric scattering components. The atmospheric attenuation coefficient was corrected to remove the temperature drift component of the detector.

[0009] Preferably, it also includes a local gradient monitoring module to extract the backscattered signal within a preset window before the leading edge of the target echo pulse is triggered, and to calculate the energy drop slope of the backscattered signal. The atmospheric parameter calculation module is based on the energy descent slope. and the rising edge slope of the target echo pulse Determine the interface coupling factor The calculation formula is: Among them, the timing correction module is based on the interface coupling factor. The offset of the timing start point is adjusted by a second weight.

[0010] Preferably, the atmospheric parameter calculation module divides the backscattering envelope before the target echo pulse into micropath units and calculates the amplitude variance of each micropath unit. The amplitude variance of the gain control module between two adjacent micropath units When the rate of change exceeds a preset threshold, pulsed gain weights are injected into the time-varying gain curve to compensate for the heterogeneous medium layer in the path.

[0011] Preferably, the atmospheric parameter calculation module calculates the expected near-field peak energy based on the atmospheric attenuation coefficient determined by the preceding sampling period; the gain control module outputs a gain attenuation command negatively correlated with the expected near-field peak energy to the detector's bias voltage adjustment link within a preset near-field time slot after the laser pulse emission, so that the original waveform data is maintained within the detector's linear dynamic range.

[0012] Preferably, it also includes a target attribute identification module, which extracts the envelope residual signal from the original waveform data and distinguishes atmospheric medium and moving entity interference based on the energy distribution characteristics of the envelope residual signal in the frequency domain; when it is determined that there is moving entity interference, the gain control module keeps the correction amount corresponding to the current atmospheric attenuation coefficient unchanged and shields the correction of the gain adjustment by the moving entity interference.

[0013] Preferably, the gain control module adopts a gain compensation function that increases exponentially with the laser flight time. The growth coefficient of the exponential term of the gain compensation function is positively correlated with the atmospheric attenuation coefficient, so that the weak echo signal at the far end of the ranging range is maintained within the dynamic recognition window of the detector.

[0014] Preferably, the timing correction module stores a timing error lookup table model. The timing correction module uses the rising slope of the target echo pulse and the atmospheric attenuation coefficient as input variables of the timing error lookup table model to determine the deviation value of the triggering time relative to the pulse energy center, and uses the deviation value as the timing start offset.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. In long-distance laser ranging sensors, the energy distribution characteristics before the arrival of the echo pulse are extracted, and an in-situ sensing mechanism for the transmittance of the transmission path is established. The backscattering signal generated by the interaction between the laser pulse and the path medium is used as a probe to realize the real-time extraction of the instantaneous optical characteristics of the measurement path. This avoids compensation deviation caused by inconsistency between external sensor data and the laser transmission path, and solves the problem of sensing failure caused by path non-uniformity in long-distance measurement. Combining the atmospheric attenuation coefficient and the echo pulse broadening characteristics, a nonlinear compensation logic for the timing start point is constructed. By calculating the pulse rise time broadening caused by the scattering medium, the timing drift state of the echo signal is corrected, ensuring the physical consistency of the ranging start point under different atmospheric visibility and echo intensity, and eliminating the fluctuation of measurement values ​​caused by atmospheric scattering.

[0016] 2. By utilizing the detector's intrinsic thermal noise as a random disturbance source and statistically analyzing the least significant bit flip frequency of the sampled data, subquantization-level weak signal feature reconstruction is achieved. This enables the system to extract the atmospheric energy attenuation slope even when the signal amplitude is lower than the quantization step size of the analog-to-digital converter, breaking the physical constraints of hardware quantization accuracy and improving the sensor's detection sensitivity in sparse scattering environments. Furthermore, by analyzing the spectral distribution characteristics of the echo envelope residual signal, a semantic arbitration mechanism between the atmospheric medium and moving interfering objects is established. Utilizing the difference in frequency domain energy distribution between atmospheric suspended particles and physical interfering objects, the energy jumps of occasional moving targets such as fallen leaves and birds are identified and shielded, ensuring that the atmospheric attenuation compensation logic only applies to the real medium environment and improving the reliability of target acquisition in complex dynamic scenarios.

[0017] 3. The interface gradient monitoring module extracts the interface noise flow before the main echo is triggered, and determines the interface coupling factor by combining the pulse rising edge slope. This decouples the average attenuation effect of the whole path from the local scattering effect near the target, eliminates the timing deviation caused by the sudden change of the local medium at the leading edge of the target, and ensures the measurement stability of the sensor under sudden conditions of local fog or dust. Attached Figure Description

[0018] Figure 1 This is a block diagram showing the module composition architecture and data processing logic connection of the present invention; Figure 2 This is a comparison diagram of the frequency domain energy distribution characteristics of atmospheric scattering medium and moving entity interference in this invention; Figure 3 This is a timing diagram showing the signal interaction between the various modules of the system of the present invention for the coordinated execution of environmental perception and deviation correction. Detailed Implementation

[0019] This detailed description is intended to illustrate the present invention. The following description is intended to explain the present invention and is not intended to limit the scope of protection of the present invention.

[0020] This invention proposes an atmospheric attenuation compensation data processing system for long-range lidar, comprising a signal acquisition module, an atmospheric parameter calculation module, a gain control module, and a timing correction module. These modules establish data connections via an internal system bus. Utilizing the backscattered signal generated by the laser pulse propagating in free space as an in-situ probe of path transmittance, the system acquires and processes raw waveform data including the preceding backscattered signal and the target echo pulse to determine the atmospheric attenuation coefficient reflecting the medium distribution along the propagation path. The gain curve of the receiving link is adjusted synchronously and the offset of the timing start point is compensated. The signal acquisition module uses a field-programmable gate array (FPGA) to build a parallel pipeline processing architecture. During the acquisition of raw waveform data, a high-speed cache is used to perform real-time windowing of the interface scattering signal stream and send it to the computing core in segments to reduce the atmospheric attenuation coefficient. The calculation is performed synchronously with the laser pulse flight, and the atmospheric attenuation coefficient is output by the atmospheric parameter calculation module. Before the target echo pulse arrives, the growth slope of the time-varying gain curve in the gain control module is adjusted by injection. At the hardware execution level, the gain compensation mismatch caused by data processing delay is eliminated, achieving a sub-microsecond response closed loop within a single pulse cycle. The sub-microsecond response is achieved by using feedforward prediction logic built with an FPGA to predict the atmospheric attenuation trend based on the scattering signal within the preceding 500ns before the laser pulse reaches the target point. This predicts the atmospheric attenuation trend and drives a high-speed current-type digital-to-analog converter to directly adjust the bias operating point of the detector amplification link. This ensures that the gain switching action is physically stable before the nanosecond-level target echo arrives, thereby guaranteeing the real-time and deterministic nature of the compensation. The atmospheric attenuation coefficient is used; to extract the characteristics of the pure path medium, the system uses an environmental noise monitoring module to collect data from the detector 10 minutes before laser pulse emission. The output signal within the preset time slot is defined as the intrinsic thermal reference. The calibration process is completed during the first 500ms silent period after system power-on. The signal acquisition module performs continuous sampling at 4096 points with laser emission disabled. The statistical mean of the thermal noise level is obtained through an accumulator and displacement calculation unit. If this mean deviates from the preset 1.25V reference by more than 2.0mV, the system will drive the 12-bit digital-to-analog converter to adjust the detector's pre-amplifier bias voltage in 0.5mV steps until the least significant bit's switching frequency stabilizes within the range of 48% to 52%. The offset stripping module then acquires the real-time background noise signal from the original waveform data. Real-time background noise signal With intrinsic thermal standard Differential processing is performed to strip away the detector's thermal drift component in order to extract the pure atmospheric scattering component. The atmospheric parameter calculation module is based on the pure atmospheric scattering components. Corrected atmospheric attenuation coefficient .

[0021] During atmospheric attenuation compensation, in order to cope with weak scattered signals below the quantization step size of the analog-to-digital converter... The problem is that the atmospheric parameter calculation module uses a subquantized feature reconstruction unit, and the sampling statistics unit counts the least significant bit flip density of the original waveform data within a preset time window of 50ns. , flip density The ratio of the number of flips to the total number of samples is used by the waveform reconstruction unit based on the flip density. With quantization step size Recover the subquantized envelope curve The calculation formula is: ,in, To recover the obtained subquantized envelope curve level values; This is the quantization step size of the detector's analog-to-digital converter; To achieve the flip density; during the system startup phase, environmental baseline calibration is performed, and data is acquired by the signal acquisition module when the laser is not emitting pulses. The intrinsic thermal noise sequence is obtained by calculating the sequence amplitude falling within the quantization step size. The probability distribution on both sides of the zero mark determines the intrinsic thermal reference. Based on this, the bias voltage of the analog-to-digital converter's front-end is adjusted to ensure that the peak-to-peak value of the base noise covers... to Quantization steps, sampling and statistical unit output flip density It exhibits linear physical sensitivity under continuously varying environmental visibility, and has a subquantized envelope curve. Reconstruction provides support from stable sources of random disturbances. Quantization step size for the detector analog-to-digital converter, As the intrinsic thermal standard, For the flipped density, The subquantized envelope curve level is used; the atmospheric parameter calculation module extracts the signal segment between the ranging zero point and the target point from the original waveform data as the interface scattering signal stream, calculates the amplitude attenuation slope of the interface scattering signal stream over time, and determines the atmospheric attenuation coefficient of the laser propagation path based on the amplitude attenuation slope. The atmospheric parameter calculation module will determine the atmospheric attenuation coefficient. The atmospheric attenuation coefficient is output in real time to the gain control module and the timing correction module. The acquisition logic is as follows: Within a 1000ns interface scattering signal stream, the system steps into calculation windows of 50ns each, extracting the average voltage value within two adjacent calculation windows and calculating its drop ratio. This drop ratio is then input into a pre-defined 16-level linear mapping table, which establishes voltage change rates from 0.1 to 0.95 up to 0.1km. - ¹ to 1.2km - ¹Correspondence of atmospheric attenuation coefficients; this linear mapping table is obtained by applying a controlled aerosol environment at a speed of 0.05 km. - ¹This method is used to obtain the in-situ solution of the average transmittance of the entire path by stepping up the visibility and recording the corresponding echo envelope slope.

[0022] The gain control module establishes a time-varying gain curve that increases non-linearly with the laser flight time. To compensate for energy loss caused by atmospheric attenuation, the gain control module uses the atmospheric attenuation coefficient... The growth slope of the time-varying gain curve is adjusted in real time to regulate the gain of the detector's subsequent amplifier circuit for the target echo pulse. In this scheme, the gain control module adopts a gain compensation function that increases exponentially with the laser flight time, and its exponential growth coefficient is related to the atmospheric attenuation coefficient. Positive correlation ensures that the weak echo signal at the far end of the ranging range remains within the detector's dynamic recognition window; the timing correction module identifies the rising edge characteristics of the target echo pulse, as atmospheric scattering causes the pulse rising edge slope to... The timing becomes slower and causes timing drift. The timing correction module adjusts the timing based on the atmospheric attenuation coefficient. With rising slope The timing start offset is determined by a preset nonlinear mapping rule. The original ranging results are corrected. The timing correction module stores a timing error lookup table model and adjusts the rising edge slope. With atmospheric attenuation coefficient As an input variable to the timing error lookup table model, the deviation value of the trigger moment relative to the pulse energy center is determined and used as the timing start offset. The timing correction module stores timing errors and uses a lookup table model that employs a bilinear interpolation algorithm to extract real-time values. Input components include atmospheric parameters. The atmospheric attenuation coefficient is output by the atmospheric parameter calculation module. The timing correction module identifies the rising edge slope of the target echo pulse. The system retrieves a pre-stored two-dimensional scatter matrix and calculates the initial timing start offset based on the distance weights between the current input component and the four adjacent calibration nodes. The local gradient monitoring module outputs the energy descent slope. With rising slope Calculate the interface coupling factor As a product operator, it acts on the initial timing start offset. Obtain the final correction value to eliminate waveform distortion interference caused by sudden changes in medium concentration near the target point. Atmospheric attenuation coefficient, The slope of the rising edge of the target echo pulse. This is the offset of the timing start point. The slope of the energy decrease of the backscattered signal. This is the interface coupling factor.

[0023] To address localized fog or abrupt changes in the ranging path, the local gradient monitoring module extracts the backscattered signal within a preset window before the target echo pulse leading edge is triggered, and calculates the energy drop slope of the backscattered signal. The atmospheric parameter calculation module is based on the energy descent slope. Rising slope of the target echo pulse Determine the interface coupling factor The calculation formula is: ,in, Interface coupling factor; The rising edge slope of the target echo pulse; The timing correction module is based on the interface coupling factor to determine the energy drop slope of the backscattered signal. Offset of timing start point A second-order weight correction is implemented to eliminate measurement errors caused by abrupt changes in medium concentration near the target point. For potential localized fog along the path, the atmospheric parameter calculation module divides the backscattering envelope into micropath units. Specifically, this division is implemented using equal-interval gating of a high-speed sampling clock, with the width of each unit corresponding to the spatial resolution of the laser. The amplitude variance of each unit is then calculated. To characterize the non-uniformity of aerosols in this region, when adjacent units When the abrupt change exceeds a preset 20% threshold, the system determines that it has entered a heterogeneous dielectric layer and triggers the gain control module to inject pulsed gain weights to ensure that the echo envelope is not clipped due to the abrupt change in the dielectric. To shield the influence of moving entities on gain adjustment, the target attribute recognition module extracts the envelope residual signal from the original waveform data. According to the envelope residual signal The energy distribution characteristics in the frequency domain distinguish between atmospheric interference and moving entity interference. When moving entity interference is detected, the gain control module maintains the current atmospheric attenuation coefficient. The corresponding correction remains unchanged, stopping the correction of gain adjustment by moving entity interference; in terms of near-field protection, the atmospheric parameter calculation module uses the atmospheric attenuation coefficient determined by the previous sampling period. The expected near-field peak energy is calculated, with the laser emission peak power set to 10W. The optical constant is obtained through factory calibration. Specifically, a pulse is emitted to a 90% reflectivity standard target at 20m, and the peak level of the detector output is recorded as 2.5V. After subtracting the initial attenuation of 0.1km⁻¹, the comprehensive optical constant is obtained as 0.025. During system operation, this constant is multiplied by the emission power of 10W and the near-field energy is calculated using the exponential attenuation lookup table stored in memory. For example, at a distance of 5m from the gate, if the calculated expected peak level exceeds the linear window of 3.0V, a gain attenuation command is output in advance. Within the preset near-field time slot after the laser pulse emission, the gain control module outputs a gain attenuation command negatively correlated with the expected near-field peak energy to the detector's bias voltage adjustment link, so that the original waveform data is maintained within the linear dynamic range of the detector. In this way, a logical closed loop of environmental feature perception and measurement deviation correction is formed within a single pulse sampling period.

[0024] Example 1: In a monitoring scenario of long-span bridge construction in mountainous areas, a long-range laser ranging sensor performs high-frequency continuous measurement on a construction benchmark point 2km away. When a sudden local dense fog occurs 1.2km along the ranging path, causing atmospheric visibility to drop from 10km to below 500m, the laser pulse experiences severe energy attenuation and pulse rise edge broadening during penetration of the heterogeneous medium layer. This results in decimeter-level timing drift errors in the traditional fixed threshold detection mode, and the far-end echo amplitude drops to the minimum quantization step of the analog-to-digital converter (ADC). the following.

[0025] The data processing system is 10 seconds before the laser pulse is emitted. The output signal of the detector is acquired in a preset time slot to obtain the intrinsic thermal reference. The signal acquisition module detects the signal 8 seconds before the main echo arrives. The path position of s is determined by the sampling and statistical unit, which calculates the least significant bit flip density of the original waveform data within a preset time window of 50 ns. The waveform reconstruction unit is based on the formula Recover the subquantized envelope curve with an amplitude lower than the quantization precision. The atmospheric parameter calculation module is based on the subquantized envelope curve. The time gradient determines the atmospheric attenuation coefficient of the propagation path. The gain control module is based on the atmospheric attenuation coefficient. The exponential growth factor of the time-varying gain curve is adjusted in real time to keep the weak signal at the far end within the detector's dynamic recognition window. The timing correction module identifies the rising slope of the target echo pulse. Combined with atmospheric attenuation coefficient The timing error lookup table model was used to determine a deviation of 16.5 ns as the timing start offset. ,in, The subquantized envelope curve level value. The quantization step size of the detector's analog-to-digital converter. For the flipped density.

[0026] Example 2: When the atmospheric attenuation compensation data processing system is deployed in an optical calibration field with visibility continuously varying from 0.3 km to 15.0 km, the test platform provides raw waveform data with a sampling rate of 2 Gsps and a system bandwidth of not less than 500 MHz. The physical measurement platform integrates an avalanche photodetector, which simulates atmospheric environments of different concentrations through an aerosol generator and injects Gaussian white noise with a signal-to-noise ratio of 20 dB into the raw signal to reproduce the industrial electromagnetic interference environment; the sampling and statistical unit processes the data, involving the statistical window length. The settings for the statistical window length The setting is based on a technical trade-off between ranging spatial resolution and statistical confidence, when the statistical window length is... When a smaller value is selected, the flipping density is... Susceptible to random biases caused by transient noise disturbances, when the statistical window length... When a larger window size is selected, the system's sensitivity in capturing local medium abrupt changes along the path decreases. Therefore, this experiment adjusts the statistical window length. Set to 50ns.

[0027] The experimental procedure begins by acquiring the detector's output signal within a preset time slot before the laser pulse emission, obtaining an intrinsic thermal reference with a stable value around 12.5 mV. As aerosol concentration increases and environmental visibility decreases, the amplitude of the interface scattering signal flow between the ranging zero point and the target point in the original waveform data increases. The sampling and statistical unit calculates the flip density of the least significant bit within the signal segment. The waveform reconstruction unit is based on the formula Recover the subquantization envelope curve with an amplitude lower than the quantization precision. ,in, The subquantized envelope curve level value. To quantize the step size, To calculate the inversion density, the atmospheric parameter calculation module solves for the atmospheric attenuation coefficient of the propagation path. The results are output to the gain control module and the timing correction module. Table 1 shows the atmospheric attenuation compensation performance test results, which demonstrate the system's performance in performing dynamic gain adjustment and timing start offset. Revised test data.

[0028] Table 1: Test Results of Atmospheric Attenuation Compensation Performance

[0029] Analysis of the test data in Table 1 shows that, within the working range of visibility from 0.5 km to 15.0 km, the overturning density... The relationship between visibility decreases and the time adjustment module is monotonically increasing, after which the timing start offset is deducted. Subsequently, the final ranging error output by the sensor stabilized within an accuracy range of less than 2.0 cm. This is the offset of the timing start point; when the visibility deteriorates to 0.3km, the flip probability of the least significant bit approaches the statistical saturation point due to the excessive intensity of the scattered echo, and the system enters the nonlinear overload region, at which point the final ranging error increases to 14.25cm.

[0030] Example 3: This example combines Figures 1 to 3 This document describes an atmospheric attenuation compensation data processing system for a long-range lidar system, as follows: Figure 1 As shown, the system mainly consists of a signal acquisition module, an atmospheric parameter calculation module, a gain control module, and a timing correction module. The detector outputs a raw analog signal to the signal acquisition module, which contains raw waveform data of backscatter and echo pulses, and transmits it to the atmospheric parameter calculation module. The atmospheric parameter calculation module intercepts the interface scattering signal stream and determines the atmospheric attenuation coefficient, which is then sent to the gain control module and the timing correction module respectively. The gain control module adjusts the slope of the time-varying gain curve and controls the subsequent amplifier circuit based on the received atmospheric attenuation coefficient. At the same time, the timing correction module determines the timing start offset based on the rising edge characteristics and corrects the original ranging result. Finally, the system outputs ranging data corrected for attenuation and offset.

[0031] like Figure 2 As shown, the horizontal axis of the coordinate system represents frequency in MHz, and the vertical axis represents energy distribution in dB. The figure illustrates the energy response characteristics of the atmospheric medium and moving entities at different frequencies. The solid line represents the spectral curve of the atmospheric medium, whose energy shows a smooth decreasing trend with increasing frequency. The dashed line represents the spectral curve of the moving entity, which exhibits significant energy fluctuations and peak bulges in specific frequency bands. The system identifies and shields interference targets based on the difference in energy distribution between the two in the frequency domain. Figure 3 As shown, after the laser emitter emits a laser pulse, the photodetector outputs the raw waveform data. The signal acquisition module performs operations to acquire the backscattered signal, acquire the target echo pulse, and transmit the raw waveform data. The atmospheric parameter calculation module then intercepts the interface scattering signal stream, calculates the amplitude attenuation slope, and determines the atmospheric attenuation coefficient. The coefficient is output in real time to the gain control module and the timing correction module. The gain control module adjusts the time-varying gain curve and adjusts the gain of the subsequent amplifier circuit to feed back to the photodetector. At the same time, the timing correction module identifies the rising edge characteristics, determines the timing start offset, and corrects the original ranging result. Finally, the system outputs the final ranging result.

[0032] Example 4: In the scenario of automatic collision avoidance monitoring for container quay cranes in coastal ports, the long-range laser ranging sensor operates under the combined conditions of high-salt spray and frequent seabird flights. The high concentration of sea salt aerosol causes non-uniform attenuation of the laser propagation path, and the moving seabirds produce energy abrupt changes in the echo envelope, similar to localized fog patches. This makes it difficult for the energy compensation algorithm to distinguish between medium absorption and physical occlusion, leading to misadjustment of the gain controller and random drift of the ranging reference. The target attribute recognition module extracts the envelope residual signal from the original waveform data. The generation logic involves subtracting the original pulse sampling sequence from a preset standard Gaussian pulse model. The system then processes the envelope residual signal. A 1024-point discrete Fourier transform was implemented. This standard Gaussian pulse model, obtained through factory calibration in a controlled laboratory environment without scattering media, accurately measures and fits the inherent waveform characteristics of the transmitted pulse. It represents the system's zero-broadening response benchmark under ideal channel conditions. By calculating the residuals, waveform distortion components induced by atmospheric scattering or physical interference can be precisely extracted. The system calculates the energy integral values ​​in the high-frequency bands from 10MHz to 50MHz. Energy integral value in the low frequency band from 0MHz to 10MHz Based on the physical characteristics of edge reflections from moving entities such as seabirds containing high-frequency harmonic components, and atmospheric aerosol scattering envelope exhibiting a smooth evolution, a judgment threshold is set. ,in This is the energy integral value in the high-frequency band. This is the energy integral value in the low-frequency band; when the threshold is determined... When the value is greater than 1.5, the system determines that there is moving entity interference in the current path. At this time, the gain control module locks the gain compensation step size of the current sampling period to shield the atmospheric attenuation coefficient caused by the instantaneous energy jump caused by seabirds. Errors in the correction amount.

[0033] The timing correction module determines the timing start offset. During this period, a two-dimensional timing error lookup table model stored in static random access memory was employed, in which the atmospheric attenuation coefficient... The index step size is set to 0.05. The range covers 0.1 Up to 1.0 The slope of the rising edge The index step size is set to 10. When the atmospheric attenuation coefficient is acquired in real time With rising slope When the data falls between model grid points, the system performs bilinear interpolation to determine the initial timing start offset based on a weighted average of the values ​​from four adjacent calibration points. For abrupt changes in the medium near the target point, the local gradient monitoring module extracts the signal within a 20ns window before the target echo pulse triggers and calculates the energy drop slope. The atmospheric parameter calculation module calculates according to the formula. Determine the interface coupling factor ,in For interface coupling factor, The slope of the rising edge, The energy descent slope; the timing correction module will adjust the interface coupling factor. As a product operator applied to the initially determined timing start offset To obtain the final correction value and eliminate the measurement deviation caused by the sudden change in local medium at the target leading edge; the system uses the frequency domain energy distribution discrimination criterion and multilinear interpolation correction formula to identify seabird interference and suppress more than 85% of false compensation triggering in the salt spray environment, reducing the ranging consistency error within a 1.5km range from 15.6cm to about 1.8cm, and verifying the measurement stability of the data processing system in the environment where non-uniform medium and dynamic entities coexist.

[0034] Example 5: The offline calibration field for laser characteristics provides a controlled temperature and humidity environment. The data processing system constructs a two-dimensional timing error lookup table model stored in static random access memory through controlled physical experiments. The physical experiment platform uses a picosecond-level delay generator to control the simulated time-of-flight range with a step size of 6.67 ps, and in conjunction with a programmable optical attenuator to generate 0.01... Up to 2.0 Atmospheric attenuation coefficient within the range Gradient; the system records each set of atmospheric attenuation coefficients. With rising slope The corresponding deviation value of the trigger time relative to the energy center of the pulse envelope is used as the timing start offset. Write to the data storage area to ensure that the timing drift under different atmospheric attenuation levels is quantified and calibrated.

[0035] After the sensor hardware is assembled and deployed in the field observation environment, the data processing system initiates the environmental baseline calibration procedure to eliminate differences in the electrical performance of individual detectors. With laser emission triggering disabled, the system performs 2048 consecutive samplings on the receiving link to calculate the amplitude variance of the sampling sequence and determine the intrinsic thermal reference under the current temperature conditions. The statistical distribution characteristics; the data processing system is based on the intrinsic thermal reference obtained from the measurement. Adjust the gain of the analog-to-digital converter's preamplifier stage so that the peak-to-peak value of the floor noise covers 1 to 2 quantization steps. Thus, the flipping density is established. Transform into subquantized envelope curve The conversion benchmark ensures that the measurement benchmark of the system is normalized under different hardware components.

[0036] Example 6: In the application scenario of LiDAR for autonomous driving on highways, the data processing system performs exponential growth coefficient calibration of the time-varying gain curve to adapt to the dynamically evolving atmospheric environment. The system uses a standard scattering target to establish an energy benchmark and obtains the atmospheric attenuation coefficient by changing the aerosol concentration. The sample sequence records the gain value that maintains the target echo pulse peak at 80% of the analog-to-digital converter's full scale, and a proportional mapping model is established to determine the exponential growth coefficient. The calculation formula is: ,in, The growth coefficient of the exponential term, It is a proportionality constant. This is the atmospheric attenuation coefficient, and the proportionality constant is... The determination logic lies in: by offline recording the rate of decrease in the signal-to-noise ratio at the receiver under different attenuation levels, the sensitivity correlation factor between the gain compensation step size and the extinction coefficient is extracted; in actual operation, It serves as a mapping weight between atmospheric physical attenuation and hardware circuit control quantities, ensuring that the exponential growth of the gain curve can accurately offset atmospheric energy loss and prevent system feedback oscillations induced by adjustment overshoot. The coefficient matrix determined by the above procedure is stored in the system memory as a basis for online adjustment, so that the system has a physical reference point for amplifying and compensating weak signals at a distance.

[0037] When the sensor detects an increase in the intensity of the backscattered signal in the near field during operation, the data processing system initiates a real-time clamping procedure in the linear region to prevent detector saturation. The atmospheric parameter calculation module uses the atmospheric attenuation coefficient determined by the previous sampling period. According to the formula Calculate the expected peak energy in the near field. ,in, This represents the expected peak energy in the near field. The peak power of laser emission. These are optical constants. Atmospheric attenuation coefficient, To minimize the detection range, the gain control module determines the near-field peak energy. The output gain attenuation command is sent to the detector's bias voltage adjustment link, causing the detector to reduce its sensitivity within a preset near-field time slot after the laser pulse is emitted.

[0038] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A data processing system for atmospheric attenuation compensation of a long-range lidar, characterized in that, include: The signal acquisition module acquires the raw waveform data output by the detector. The raw waveform data includes the target echo pulse and the backscattered signal before the target echo pulse arrives. The atmospheric parameter calculation module extracts the signal segment between the zero-range point and the target point from the original waveform data as the interface scattering signal flow, calculates the amplitude attenuation slope of the interface scattering signal flow over time, and determines the atmospheric attenuation coefficient of the laser propagation path based on the amplitude attenuation slope. The gain control module establishes a time-varying gain curve that increases non-linearly with the laser flight time. Based on the atmospheric attenuation coefficient, it adjusts the growth slope of the time-varying gain curve in real time to adjust the gain of the detector's subsequent amplifier circuit for the target echo pulse. The timing correction module identifies the rising edge characteristics of the target echo pulse, and determines the timing start offset based on the atmospheric attenuation coefficient and the slope of the rising edge characteristics through a preset nonlinear mapping rule, thereby correcting the original ranging result. The atmospheric parameter calculation module outputs the determined atmospheric attenuation coefficient to the gain control module and the timing correction module in real time. The adjustment of the time-varying gain curve by the gain control module and the determination of the timing start offset by the timing correction module are both in real time response to the change of atmospheric attenuation coefficient, forming a logical closed loop of environmental feature perception and measurement deviation correction within a single pulse sampling period.

2. The atmospheric attenuation compensation data processing system for long-range lidar according to claim 1, characterized in that, The atmospheric parameter calculation module extracts the local signal within a preset window before the trigger time of the rising edge of the target echo pulse in the backscattered signal, calculates the level change of the local signal relative to the average amplitude of the interface scattering signal flow, and inverts the local optical transmittance on the laser propagation path based on the level change, thereby correcting the atmospheric attenuation coefficient to eliminate the measurement error caused by the sudden change in medium concentration at the near target location.

3. The atmospheric attenuation compensation data processing system for long-range lidar according to claim 1, characterized in that, The atmospheric parameter calculation module includes: a sampling and statistics unit, which calculates the least significant bit flip density of the raw waveform data within a preset time window. ,in, The ratio of the number of flips to the total number of samples; the waveform reconstruction unit, based on the flip density. Quantization step size of the detector analog-to-digital converter Recover the subquantized envelope curve The calculation formula is: Among them, the atmospheric parameter calculation module is based on the subquantized envelope curve. The atmospheric attenuation coefficient is determined by the gradient over time, and the intrinsic thermal noise of the detector is used to extract values ​​below the quantization step size. The amplitude characteristics of the scattered signal.

4. The atmospheric attenuation compensation data processing system for long-range lidar according to claim 1, characterized in that, It also includes an environmental noise monitoring module, which collects the detector's output signal during a preset time slot before laser pulse emission to obtain the intrinsic thermal reference. The offset stripping module acquires the real-time background noise signal from the original waveform data. Real-time background noise signal With intrinsic thermal standard Perform differential processing to extract the pure atmospheric scattering component. The atmospheric parameter calculation module is based on the pure atmospheric scattering components. The atmospheric attenuation coefficient was corrected to remove the temperature drift component of the detector.

5. The atmospheric attenuation compensation data processing system for long-range lidar according to claim 1, characterized in that, It also includes a local gradient monitoring module, which extracts the backscattered signal within a preset window before the leading edge of the target echo pulse is triggered, and calculates the energy drop slope of the backscattered signal. ; The atmospheric parameter calculation module is based on the energy descent slope. and the rising edge slope of the target echo pulse Determine the interface coupling factor The calculation formula is: Among them, the timing correction module is based on the interface coupling factor. The offset of the timing start point is adjusted by a second weight.

6. The atmospheric attenuation compensation data processing system for long-range lidar according to claim 1, characterized in that, The atmospheric parameter calculation module divides the backscattered envelope before the target echo pulse into micropath units and calculates the amplitude variance of each micropath unit. The amplitude variance of the gain control module between two adjacent micropath units When the rate of change exceeds a preset threshold, pulsed gain weights are injected into the time-varying gain curve to compensate for the heterogeneous medium layer in the path.

7. The atmospheric attenuation compensation data processing system for long-range lidar according to claim 1, characterized in that, The atmospheric parameter calculation module calculates the expected peak energy in the near field based on the atmospheric attenuation coefficient determined by the previous sampling period; the gain control module outputs a gain attenuation command that is negatively correlated with the expected peak energy in the near field within the preset near field time slot after the laser pulse is emitted, and sends it to the bias voltage adjustment link of the detector so that the original waveform data is maintained within the linear dynamic range of the detector.

8. The atmospheric attenuation compensation data processing system for long-range lidar according to claim 1, characterized in that, It also includes a target attribute identification module, which extracts the envelope residual signal from the original waveform data and distinguishes atmospheric medium and moving entity interference based on the energy distribution characteristics of the envelope residual signal in the frequency domain. When it is determined that there is moving entity interference, the gain control module keeps the correction amount corresponding to the current atmospheric attenuation coefficient unchanged and shields the correction of the gain adjustment by the moving entity interference.

9. The atmospheric attenuation compensation data processing system for a long-range lidar according to claim 1, characterized in that, The gain control module uses a gain compensation function that increases exponentially with the laser flight time. The growth coefficient of the exponential term of the gain compensation function is positively correlated with the atmospheric attenuation coefficient, so that the weak echo signal at the far end of the ranging range is maintained within the detector's dynamic recognition window.

10. The atmospheric attenuation compensation data processing system for a long-range lidar according to claim 1, characterized in that, The timing correction module stores a timing error lookup table model. The timing correction module uses the rising slope of the target echo pulse and the atmospheric attenuation coefficient as input variables of the timing error lookup table model to determine the deviation value of the trigger time relative to the pulse energy center, and uses the deviation value as the timing start offset.

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