Laser radar body target echo generating device

Abstract

The invention provides a laser radar target echo generation device, and relates to the technical field of laser radar target characteristic digital simulation and high repetition frequency narrow pulse laser echo regeneration. According to the device, through a laser radar body target echo simulation system, a body target simulation model matched with a body target is screened out from a typical target model library; performing multi-channel optical characteristic simulation on the body target by using the laser radar, and generating body target echo simulation data of the laser radar on the typical target under different rendezvous conditions; the laser radar body target echo generation module is used for carrying out pulse echo detection of which the half bandwidth is in a nanosecond level according to the body target echo simulation data; a pulse current signal is converted into an electric pulse signal in an undistorted manner, the electric pulse signal is converted into an optical pulse signal in an undistorted manner, and the optical pulse power in a single pulse is modulated in real time. The problems that the target echo generated by the existing laser radar point target echo generation device is simple in characteristic and the real characteristic of the echo is difficult to simulate are solved.

Description

Technical Field

[0001] This document relates to the fields of digital simulation of lidar target characteristics and high repetition rate narrow pulse laser echo regeneration technology, and in particular to a lidar target echo generation device. Background Technology

[0002] With the development of lidar technology, its functions and applications have become increasingly diverse and powerful. Laser detection technology, in particular, has become an indispensable part of both national defense and civilian applications. The development of any product inevitably involves testing, and lidar is no exception. In the past, lidar product testing was often constrained by complex testing environments, variable weather, and varying operating postures, resulting in long development cycles and high budgets. Therefore, lidar target echo generation devices have emerged.

[0003] However, most lidar target echo generation devices simplify volumetric targets to point targets, ignoring the volumetric characteristics of targets under complex intersection conditions. This simplification results in a significant loss of crucial information regarding the target echo characteristics. Consequently, they can only test the basic functions of lidar products, offering limited testing capabilities and exhibiting drawbacks such as difficulty in verifying complex targets and a lack of comprehensive testing functionality.

[0004] Currently, there is very little research in China on lidar echo generation devices for high-repetition-rate, narrow-pulse-width volume targets. Firstly, considering real-world intersection conditions and the characteristics of volume targets, the echo characteristics of lidar volume targets are complex and variable, making simulation difficult. Secondly, research on lidar volume target echo characteristics is limited, lacking relevant databases and technical support. Finally, high-repetition-rate, narrow-pulse-width lidar target echoes are generally within tens of nanoseconds, making the acquisition, simulation, waveform analysis, and optical pulse generation of the target echo waveforms quite challenging.

[0005] Therefore, there is an urgent need for an echo generation device to solve the problems of current lidar point target echo generation devices, which generate simple target echo characteristics, making it difficult to simulate the true characteristics of the echo, and the low accuracy of target echo characteristics due to the single simulation intersection conditions, as well as the limited target types and high test costs. Summary of the Invention

[0006] This specification provides a lidar target echo generation device to solve the problems of current lidar point target echo generation devices, which generate target echoes with simple characteristics, making it difficult to simulate the true characteristics of the echoes, resulting in low accuracy of target echo characteristics due to the single simulated intersection conditions, limited target types, and high experimental costs.

[0007] In one aspect, this specification provides a lidar target echo generation device, including: a lidar volume target echo simulation system and a lidar volume target echo generation module;

[0008] The lidar volume target echo simulation system is used to select a volume target simulation model that matches the volume target from a pre-established library of typical target models; based on the volume target simulation model, the lidar is used to simulate the multi-channel optical characteristics of the volume target, and generate volume target echo simulation data of the lidar for typical targets under different intersection conditions.

[0009] The lidar target echo generation module is used to perform pulse echo detection with a half bandwidth of nanoseconds based on the target echo simulation data; it converts the pulse current signal into an electrical pulse signal without distortion, and then converts the electrical pulse signal into an optical pulse signal without distortion, and modulates the optical pulse power within a single pulse in real time to achieve arbitrary laser waveform modulation.

[0010] Secondly, this specification provides a method for generating laser radar target echoes, including:

[0011] The lidar volume target echo simulation system selects a volume target simulation model that matches the volume target from a pre-established library of typical target models; based on the volume target simulation model, it uses lidar to simulate the multi-channel optical characteristics of the volume target, generating volume target echo simulation data of typical targets under different intersection conditions.

[0012] The lidar target echo generation module performs pulse echo detection with a half-bandwidth of nanoseconds based on the target echo simulation data; it converts the pulse current signal into an electrical pulse signal without distortion, and then converts the electrical pulse signal into an optical pulse signal without distortion, modulating the optical pulse power within a single pulse in real time to achieve arbitrary laser waveform modulation.

[0013] The beneficial effects of this invention are as follows:

[0014] This specification provides a lidar target echo generation device. This device uses a lidar volume target echo simulation system to select a volume target simulation model matching the target from a typical target model library. It then uses lidar to simulate the multi-channel optical characteristics of the volume target, generating simulated volume target echo data for typical targets under different intersection conditions. The lidar volume target echo generation module performs pulse echo detection with a half-bandwidth of nanoseconds based on the simulated volume target echo data. It converts the pulse current signal into an electrical pulse signal without distortion, and then converts the electrical pulse signal into an optical pulse signal without distortion, modulating the optical pulse power within a single pulse in real time. This device solves the problems of current lidar point target echo generation devices, which generate simple target echo characteristics, making it difficult to simulate the true characteristics of the echo, and resulting in low accuracy of target echo characteristics due to the limited simulation of intersection conditions. It also addresses the issues of missing short-range information in target echo characteristics, the limited target range, and high experimental costs. This device employs a combination of hardware and software. It uses a lidar target echo simulation system to generate simulation data and a lidar target echo generation module to regenerate the target echo optical signal. This combination of hardware and software enables real-time simulation of lidar target echoes under complex intersection conditions, providing richer and more comprehensive performance verification for lidar products. Attached Figure Description

[0015] The accompanying drawings, which are included to provide a further understanding of this specification and form part of this specification, illustrate exemplary embodiments and are used to explain this specification, but do not constitute an undue limitation thereof. In the drawings:

[0016] Figure 1 This is a schematic diagram of a lidar target echo generation device provided in the embodiments of this specification;

[0017] Figure 2 This is a schematic diagram illustrating the principle of volume target reflection provided in the embodiments of this specification;

[0018] Figure 3 This is a schematic diagram of a pulse echo detection module provided in the embodiments of this specification;

[0019] Figure 4 This is a schematic diagram of a volume target echo electrical signal generation module provided in the embodiments of this specification;

[0020] Figure 5 This is a schematic diagram illustrating the principle of generating an arbitrary waveform laser as provided in the embodiments of this specification;

[0021] Figure 6 This is a schematic diagram of an arbitrary laser echo generation module provided in the embodiments of this specification;

[0022] Figure 7 This is a schematic diagram of a lidar target echo generation method provided in the embodiments of this specification. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this specification clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments in this specification, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort are within the scope of protection of this document.

[0024] The technical solutions provided in the various embodiments of this specification are described in detail below with reference to the accompanying drawings. Specific Implementation Example 1:

[0026] This embodiment provides a lidar target echo generation device; see [link to documentation]. Figure 1 This includes: a lidar target echo simulation system and a lidar target echo generation module;

[0027] The lidar target echo simulation system and the lidar target echo generation module are connected by optical fiber.

[0028] Specifically, the functions of each module are as follows:

[0029] The lidar volume target echo simulation system is used to select a volume target simulation model that matches the volume target from a pre-established typical target model library; based on the volume target simulation model, the lidar is used to simulate the multi-channel optical characteristics of the volume target, and generate volume target echo simulation data of the lidar for typical targets under different intersection conditions.

[0030] The lidar target echo generation module is used to perform pulse echo detection with a half bandwidth of nanoseconds based on the target echo simulation data; it converts the pulse current signal into an electrical pulse signal without distortion, and then converts the electrical pulse signal into an optical pulse signal without distortion, and modulates the optical pulse power within a single pulse in real time to achieve arbitrary laser waveform modulation.

[0031] The working principle of each module will be explained in detail below:

[0032] Current lidar point target echo generation devices have simple target echo characteristics. However, in real intersection processes, targets have certain geometric dimensions. At close range, different parts of the target have different distances from the lidar, different reflectivities, and echo signals from different parts of the target exhibit both detection distance and reflection intensity differences. This simplification leads to a lack of close-range information on target echo characteristics. Furthermore, current lidar point target echo generation devices treat both the lidar and the target as two points, thus approximating linear motion and resulting in a single intersection condition. However, in real intersection processes, the lidar's laser beam has a range, and both the lidar product and the target possess complex attitude information. The simplification of the single intersection condition leads to a decrease in the accuracy of target echo characteristics. Replacing a volume target with a point target results in the loss of crucial target echo characteristic information. To address these issues, this embodiment establishes a lidar volume target echo simulation system.

[0033] The lidar target echo simulation system includes: a target model library establishment unit, a target model screening unit, a lidar model and parameter configuration unit, a target characteristic simulation unit, and an echo power calculation unit, wherein:

[0034] The target model library establishment unit is used to establish a typical target model library, wherein the typical target model library is a target three-dimensional solid model constructed using the surface element method, wherein the target three-dimensional solid model includes coordinate system definition method, surface element number, mesh size, skin material, coating color, and reflectivity;

[0035] The typical target model library includes three-dimensional target models and target surface material reflection characteristic models.

[0036] Specifically, the three-dimensional structural model of a typical target established in this embodiment mainly realizes the management and reading of target 3-D structural model files in commonly used standard formats; the target entity model (three-dimensional geometric model) is constructed using the panel method, and provides standard information such as the coordinate system definition method, panel number, mesh size, skin material, coating color, and reflectivity description of the model, which facilitates the subsequent expansion of the number of models.

[0037] The volume target model screening unit is used to screen out volume target simulation models that match the volume target from the typical target model library;

[0038] The lidar model and parameter configuration unit is used to set the lidar model and set the lidar multi-channel parameters.

[0039] The multi-channel parameters of the lidar include the number of lidar channels n and the included angle of the multi-channel lidar. Laser radar wavelength λ, transmitting module coordinate system (X f Yf X f ), launch module tilt angle α, launch module field of view Ω f Transmit power P, transmit pulse width τ, repetition frequency f, receiver module coordinate system (X) j Y j X j ), receiver module tilt angle β, receiver module field of view Ω j , the optical aperture S of the receiving module, and the photoelectric responsivity of the receiving module.

[0040] The rendezvous conditions include the lidar starting point (X0, Y0, X0) and the lidar velocity (V). X0 V Y0 V Z0 ), LiDAR attitude (θ) X0 ,θ Y0 ,θ Z0 ), Target starting point (X1, Y1, X1), Target velocity (V) X1 V Y1 V Z1 ), target pose (θ) X1 ,θ Y1 ,θ Z1 ).

[0041] The target characteristic simulation unit is used to simulate the laser radar illuminating the target from multiple angles and to acquire multi-channel echo data using the laser radar model and the target simulation model.

[0042] Specifically, the volume target characteristic simulation unit is used for:

[0043] Based on the characteristics of volume target echoes, a rich target optical model library is established to calculate the multi-channel volume target echoes of lidar in complex intersection scenarios.

[0044] The echo power calculation unit is used to calculate the intersection trajectory and the area of ​​the irradiated region based on the multi-channel echo data and the preset intersection conditions, and then determine the echo power of each surface element.

[0045] Specifically, the echo power calculation unit is used for:

[0046] The detection situation is determined by combining the intersection conditions, the position of each channel, the tilt angle and the field of view. The area of ​​the target illuminated area and the effective echo power received by the lidar are statistically analyzed. Finally, the multi-channel target echo data are saved.

[0047] Specific examples:

[0048] Specifically, in multi-channel detection, each channel has a different detection angle to perform target detection and discrimination;

[0049] (1) The calculation process for the irradiated area is as follows:

[0050] In the lidar detection process, such as Figure 2 As shown, at a certain trajectory point, the topology criterion is first checked: subsequent judgments are made if and only if the topology criterion indicates that there is a laser detection beam of a certain channel that will illuminate a certain area of ​​the target; otherwise, the simulation calculation of the next trajectory point is performed.

[0051] 1) Determine if the target is within the beam range.

[0052] 2) Detection status of each transmission channel of the positioning lidar;

[0053] 3) Detect backlight criterion, i.e., the laser beam is projected onto the back of the surface element;

[0054] 4) Illumination detection criteria: The illumination area of ​​each channel of the lidar is limited, and only a small part of the surface element of the target is illuminated. If the surface element is not within the detection range of a certain channel after calculation, the laser detection beam of that channel will not illuminate the surface element.

[0055] 5) Detect subdivision criteria. If a surface element is indicated to be illuminated by the laser detection beam after the illumination criteria are met, the subdivision type of the surface element is determined, and it is subdivided into an illuminated area and an unilluminated area, and the area S of the illuminated area is calculated.

[0056] (2) The calculation process for echo power is as follows:

[0057] 1) Target BRDF calculation and simulation function based on intersection conditions

[0058] The main function is to calculate the bidirectional reflection distribution function (BRDF) of a target under arbitrary intersection conditions. Simultaneously, it corrects relevant parameters in the model according to different target types and intersection conditions, outputting BRDF data for different targets under different intersection conditions. The data content is arranged by frame number; the frame header includes the target centroid coordinates, velocity vector, and intersection conditions, while the data content includes the coordinates of the elements involved in the calculation and the BRDF values ​​of those elements.

[0059] The BRDF expression for the target surface is as follows:

[0060] In the formula, These are the zenith angle and azimuth angle in spherical coordinates, respectively, with the subscripts i and r representing the incident and reflected amounts, respectively. for Reflection brightness in the direction, for The incident illuminance in the direction is then defined as the bidirectional reflectance distribution function along the direction. Radiance emitted in a specific direction Along Irradiance incident on the surface being measured The ratio.

[0061] 2) Target LRCS calculation and simulation function based on intersection conditions

[0062] Since BRDF describes the ratio of two infinitesimal quantities, it is not suitable for practical calculations. When quantitatively describing the laser echo characteristics of a target, the Laser Radar Cross-Section (LRCS) is typically used. The LRCS is an equivalent area. When the laser energy intercepted by this area at a certain energy flux density is scattered isotropically in all directions, the scattered power per unit solid angle is exactly equal to the power scattered by the target it represents within a unit solid angle towards the receiving beam. The LRCS and BRDF have the following relationship: σ = 4πf r cosθ i cosθ r S;

[0063] In the formula, σ represents LRCS, which has the dimension of area. When calculating the reflected power of the target, we have θ i =θ r S is the area irradiated by the laser.

[0064] The irradiated area S of a single surface element was calculated. i Angle of incidence θ i The echo power reflected from this surface element to the lidar detector can be calculated as follows:

[0065] In the formula, P t R represents the peak power of the emitted pulse, and R is the distance from the laser radar to the surface element. t For the launch axis angle, view t For the launch roll angle, S r For the receiving area of ​​the receiving optical system, τ t τ r These are the transmittance of the transmitting and receiving optical systems, respectively.

[0066] Based on the LRCS calculation formula and the echo power calculation formula, calculate the LRCS value and echo power of each element, output the LRCS value, element area, and element coordinate information to a file, and output the echo power to the receiving module.

[0067] It should be noted that the acquisition of target characteristics by lidar typically involves field tests using real targets or 1:1 models. This process is lengthy, involves limited target types, and makes it difficult to acquire rich target data quickly. The lidar volume target echo simulation system solves this problem of limited target types. Its rich target model library helps lidar products quickly acquire and analyze the volume target echo characteristics of various targets. Furthermore, current lidar target characteristic acquisition test scenarios are complex, particularly for large and fast-moving targets, where simulation testing is difficult, limited, and expensive. The lidar volume target echo simulation system addresses this cost issue. Using this device instead of field tests eliminates limitations imposed by weather and field conditions, shortens development cycles, and effectively reduces manpower and financial costs. This is of great significance for reducing testing costs and improving lidar target detection capabilities.

[0068] Based on this, this embodiment solves the problem of traditional target echo simulation systems having a single intersection scenario (approximately linear motion) and distortion of close-range echo signals by setting up a lidar volume target echo simulation system. It realizes lidar multi-channel volume target echo calculation in complex intersection scenarios and can realize the dual differences in echo signal detection distance and reflection intensity of different parts of close-range targets.

[0069] Furthermore, the lidar target echo generation module includes: a pulse echo detection module, a target echo electrical signal generation module, and an arbitrary laser echo generation module;

[0070] The pulse echo detection module, the volume target echo electrical signal generation module, and the arbitrary laser echo generation module are connected in sequence.

[0071] The following is a detailed description of each module:

[0072] The pulse echo detection module consists of an optical pulse comparator detector, a power supply module, interfaces, and circuit boards. A block diagram is shown below. Figure 3 .

[0073] The pulse echo detection module is used to convert the optical pulse input from the optical fiber into a TTL electrical pulse signal and transmit it to the control system through the port;

[0074] The working principle and process of the pulse echo detection module are as follows:

[0075] 1) The light pulse is transmitted to the photosensitive surface of the PIN detector through the optical fiber.

[0076] 2) The PIN detector generates an electrical pulse signal. The signal is processed by the comparator circuit. When the voltage exceeds the threshold, a TTL pulse signal is generated.

[0077] 3) TTL data is transmitted to the port and then to the control system via the port.

[0078] To achieve pulse echo detection with a half-bandwidth of nanoseconds and avoid severe timing errors caused by pulse waveform distortion during the conversion of pulse current signals into voltage signals, a high-bandwidth PIN detector and transimpedance amplifier were selected.

[0079] Based on this, this embodiment achieves pulse echo detection with a half-bandwidth in the nanosecond range by setting up a pulse echo detection module. This ensures that the pulse waveform is undistorted during the conversion of the pulse current signal into a voltage signal, and that the laser triggering moment is identified without error.

[0080] Furthermore, the target echo electrical signal generation module includes: a DAC model, a filtering module, a power amplification module, and a 1×N terminal switching matrix.

[0081] The target echo electrical signal generation module is used to convert the laser radar target echo data into electrical pulse signals via a DAC, filter, control the power, and amplify the DAC output signal, and then output one control signal in N time-division multiplexing via a 1×N terminal switching matrix; thus realizing the output of multi-channel target echo electrical signals. (See [link]). Figure 4 .

[0082] The working principle and process of the target echo electrical signal generation module are as follows:

[0083] 1) After receiving the trigger signal, the target echo electrical signal generation module reads the target echo simulation data and sends it to the DAC model.

[0084] 2) The simulation data is converted into electrical pulse signals by a DAC, then filtered, power controlled, and amplified before being sent to a 1×N terminal switching matrix.

[0085] 3) Output N channels of laser radar body target echo electrical signals.

[0086] Based on this, this embodiment converts the laser radar target echo into an electrical pulse signal by setting up a volume target echo electrical signal generation module, ensuring that the waveform is not distorted during the conversion process.

[0087] Furthermore, the arbitrary laser echo generation module is used to convert the volume target echo electrical pulse signal into an optical pulse signal, modulate the optical pulse signal power according to the amplitude of the volume target echo electrical signal, modulate the optical pulse power within a single pulse in real time, and linearly load the volume target echo electrical signal onto the optical signal without distortion.

[0088] Specifically, the arbitrary laser echo generation module is used for:

[0089] Based on the characteristics of the target echo, using optical radio technology, the target echo electrical signal is driven by a driving circuit to increase its driving capability. Then, through an electro-optic modulation control module, a driving current containing modulation information is generated. This driving current is applied to a high-speed laser to generate an optical power waveform corresponding to the voltage of the target echo electrical signal, achieving arbitrary waveform modulation. (See also...) Figure 5 .

[0090] The arbitrary laser echo generation module includes: a driving circuit, a laser, and an attenuator.

[0091] The arbitrary laser echo generation module consists of a control signal input interface, a drive circuit, a semiconductor laser, an optical fiber attenuator, and an optical fiber output interface. (See [link]). Figure 6 ;

[0092] It should be noted that the drive circuit design fully considers the requirements of laser target echo generation on the rising edge, falling edge, and saturation signal of the optical pulse, ensuring that the target echo electrical signal is linearly and without distortion applied to the optical signal. To achieve a fast rising edge, fast power devices, a high-speed D / A converter, and a high-frequency operational amplifier are selected. Simultaneously, the exponential charging effect of the capacitor is utilized to achieve a smooth transition at the top of the circuit. To achieve a steep falling edge initially, but gradually decreasing to zero near the end, in addition to the normal pulse reference voltage dropping to 0, an anti-correlation interruption pulse is added to the inverting input of the operational amplifier to accelerate the discharge speed of the control circuit. In the discharge section of the power drive circuit, the discharge speed is adjusted to ensure that the backlash is not excessive. To prevent excessive pulse width, hardware circuitry is used to monitor each pulse individually. When the pulse width exceeds the set maximum, the monitoring circuit activates, pulling down the power control circuit. Simultaneously, a positive feedback circuit is used to accelerate the circuit's operation.

[0093] The selection of fiber optic attenuators fully considers the large dynamic range of the laser target echo signal amplitude, and a MEMS digitally adjustable fiber optic attenuator is adopted.

[0094] The working principle and process of the arbitrary laser echo generation module are as follows:

[0095] 1) The simulated signal of the target body is transmitted to the drive circuit through the coaxial cable and the MCX interface.

[0096] 2) The driving circuit generates a simulated current for the target volume and inputs it into the laser.

[0097] 3) The laser generates a simulated light pulse for the target and inputs it to the fiber optic attenuator through an optical fiber.

[0098] 4) The attenuated target simulated optical pulse is output through the optical fiber interface.

[0099] It should be noted that the arbitrary laser echo generation module must not only ensure the bandwidth requirement of the optical pulse signal and the linearity requirement, but also meet the requirement of a large dynamic range for different powers of the target echo electrical signal to be converted, so as to fully guarantee the characteristics of the laser target echo.

[0100] Based on this, this embodiment achieves arbitrary laser waveform modulation through an arbitrary laser echo generation module. During the conversion from the volume target echo electrical signal to the optical pulse signal, it overcomes the problem of the laser requiring a certain amount of energy accumulation and triggering time to switch from off to on, thus enabling the optical pulse rising edge to follow the input electrical pulse signal; it also overcomes the complexity of the volume target echo signal, achieving a wide dynamic range of optical pulse power.

[0101] In summary, this embodiment utilizes a lidar volume target echo simulation system to select a volume target simulation model matching the volume target from a typical target model library. It then uses lidar to simulate the multi-channel optical characteristics of the volume target, generating volume target echo simulation data for typical targets under different intersection conditions. The lidar volume target echo generation module performs pulse echo detection with a half-bandwidth of nanoseconds based on the volume target echo simulation data. It converts the pulse current signal into an electrical pulse signal without distortion, and then converts the electrical pulse signal into an optical pulse signal without distortion, modulating the optical pulse power within a single pulse in real time. This solves the problems of current lidar point target echo generation devices, which generate simple target echo characteristics, making it difficult to simulate the true characteristics of the echo, and resulting in low accuracy of target echo characteristics due to the limited simulation of intersection conditions. It also addresses the issues of missing near-range information in target echo characteristics, the limited target representation, and high experimental costs. This device employs a combination of hardware and software. It uses a lidar target echo simulation system to generate simulation data and a lidar target echo generation module to regenerate the target echo optical signal. This combination of hardware and software enables real-time simulation of lidar target echoes under complex intersection conditions, providing richer and more comprehensive performance verification for lidar products. Specific Implementation Example 2:

[0103] This embodiment provides a lidar target echo generation device, including: a lidar volume target echo simulation system and a lidar volume target echo generation module;

[0104] The functions of each part are explained in detail below:

[0105] I. LiDAR Volume Target Echo Simulation System

[0106] The lidar volume target echo simulation system fully considers the optical characteristics of typical targets; the spectral characteristics of the laser emitted by the laser; the energy and size variation characteristics of the laser spot illuminating the target; the characteristics of laser transmission through the atmosphere; and the motion characteristics under different intersection conditions. Based on this, it generates volume target echo simulation data of typical targets under different intersection conditions.

[0107] 1.1. Establish a three-dimensional structural model of a typical target.

[0108] It mainly implements the management and reading of target 3D structural model files in commonly used standard formats.

[0109] The target solid model (3D geometric model) is constructed using the panel method, and the model is provided with specifications such as coordinate system definition, panel number, mesh size, skin material, coating color, and reflectivity description, which facilitates the subsequent expansion of the model number.

[0110] 1.2 Simulation of Optical Characteristics of Volume Targets in Multi-channel LiDAR

[0111] Simulation of the optical characteristics of lidar targets based on multi-channel parameter settings.

[0112] Considering that the detection angles of each channel are different during multi-channel detection, target detection and discrimination are performed.

[0113] In the lidar detection process, such as Figure 2 As shown, at a certain trajectory point, the topology criterion is first checked: subsequent judgments are made only if the topology criterion indicates that there is a laser detection beam of a certain channel that will illuminate a certain area of ​​the target; otherwise, the simulation calculation of the next trajectory point is performed.

[0114] (1) Determine whether the target is within the beam range.

[0115] (2) Detection status of each transmission channel of the positioning lidar;

[0116] (3) Detect backlight criterion, i.e., the laser beam is projected onto the back of the surface element;

[0117] (4) Illumination criterion: The illumination area of ​​each channel of the lidar is limited. Only a small part of the surface element of the target is illuminated. If the surface element is not within the detection range of a certain channel after calculation, the laser detection beam of that channel will not illuminate the surface element.

[0118] (5) Detect subdivision criteria. If a surface element is indicated to be irradiated by the laser detection beam after the illumination criteria, the subdivision type of the surface element is determined, and it is subdivided into the irradiated area and the unirradiated area, and the area S of the irradiated area is calculated.

[0119] 1.3. Target BRDF Calculation and Simulation Function Based on Intersection Conditions

[0120] The main function is to calculate the bidirectional reflection distribution function (BRDF) of a target under arbitrary intersection conditions. Simultaneously, it corrects relevant parameters in the model according to different target types and intersection conditions, outputting BRDF data for different targets under different intersection conditions. The data content is arranged by frame number; the frame header includes the target centroid coordinates, velocity vector, and intersection conditions, while the data content includes the coordinates of the elements involved in the calculation and the BRDF values ​​of those elements.

[0121] The BRDF expression for the target surface is as follows:

[0122] In the formula, These are the zenith angle and azimuth angle in spherical coordinates, respectively, with the subscripts i and r representing the incident and reflected amounts, respectively. for Reflection brightness in the direction, for The incident illuminance in the direction is then defined as the bidirectional reflectance distribution function along the direction. Radiance emitted in a specific direction Along Irradiance incident on the surface being measured The ratio.

[0123] 1.4. Target LRCS Calculation and Simulation Function Based on Intersection Conditions

[0124] Since BRDF describes the ratio of two infinitesimal quantities, it is not suitable for practical calculations. When quantitatively describing the laser echo characteristics of a target, the Laser Radar Cross-Section (LRCS) is typically used. The LRCS is an equivalent area. When the laser energy intercepted by this area at a certain energy flux density is scattered isotropically in all directions, the scattered power per unit solid angle is exactly equal to the power scattered by the target it represents within a unit solid angle towards the receiving beam. The LRCS and BRDF have the following relationship: σ = 4πf r cosθ i cosθ r S;

[0125] In the formula, σ represents LRCS, which has the dimension of area. When calculating the reflected power of the target, we have θ i =θ r S is the area irradiated by the laser.

[0126] The irradiated area S of a single surface element was calculated. i Angle of incidence θ iThe echo power reflected from this surface element to the lidar detector can be calculated as follows:

[0127] In the formula, P t R represents the peak power of the emitted pulse, and R is the distance from the laser radar to the surface element. t For the launch axis angle, view t For the launch roll angle, S r For the receiving area of ​​the receiving optical system, τ t τ r These are the transmittance of the transmitting and receiving optical systems, respectively.

[0128] Based on the LRCS calculation formula and the echo power calculation formula, the LRCS value and echo power of each element are calculated. The LRCS value, element area, element coordinates and other information are output to a file, and the echo power is output to the receiving module.

[0129] 2. LiDAR target echo generation module

[0130] 2.1. Pulse Echo Detection Module

[0131] The function of the pulse echo detection module is to convert the optical pulses input from the optical fiber into TTL electrical pulse signals and transmit them to the control system through the port. It consists of an optical pulse comparator detector, a power supply module, interfaces, and circuit boards. The block diagram is shown below. Figure 3 .

[0132] Its working principle and process are as follows:

[0133] 1. The light pulse is transmitted to the photosensitive surface of the PIN detector through the optical fiber.

[0134] 2. The PIN detector generates an electrical pulse signal. The signal is processed by a comparator circuit. When the voltage exceeds the threshold, a TTL pulse signal is generated.

[0135] 3. TTL data is transmitted to the port and then to the control system via the port.

[0136] To achieve pulse echo detection with a half-bandwidth of nanoseconds and avoid severe timing errors caused by pulse waveform distortion during the conversion of pulse current signals into voltage signals, a high-bandwidth PIN detector and transimpedance amplifier were selected.

[0137] 2.2. Target Echo Electrical Signal Generation Module

[0138] The target echo electrical signal generation module converts the laser radar target echo into an electrical pulse signal via a DAC. The DAC output signal undergoes filtering, power control, and amplification. Then, through a 1×N terminal switching matrix, one control signal is output in a time-division N-way manner, achieving multi-channel target echo electrical signal output. Figure 4 As shown.

[0139] Its working principle and process are as follows:

[0140] 1. After receiving the trigger signal, the target echo electrical signal generation module reads the target echo simulation data and sends it to the DAC model.

[0141] 2. The simulation data is converted into electrical pulse signals by a DAC, then filtered, power controlled, and amplified before being sent to a 1×N terminal switching matrix.

[0142] 3. Output N channels of laser radar body target echo electrical signals.

[0143] 2.3 Arbitrary Laser Echo Generation Module

[0144] The main function of the arbitrary laser echo generation module is to convert the volume target echo electrical signal into an optical pulse signal. The power of the optical pulse signal needs to be modulated according to the amplitude of the volume target echo electrical signal, and the real-time modulation of the optical pulse power within a single pulse needs to be achieved. At the same time, it is necessary to ensure that the volume target echo electrical signal is linearly loaded onto the optical signal without distortion.

[0145] The arbitrary laser echo generation module must ensure both the bandwidth and linearity requirements of the optical pulse signal. At the same time, it must also meet the requirement of a large dynamic range for different powers of the target echo electrical signal to be converted, so as to fully guarantee the characteristics of the laser target echo.

[0146] Based on the characteristics of volumetric target echoes, optical radio technology is used. The volumetric target echo electrical signal is driven by a driving circuit to increase its driving capability. Then, through an electro-optic modulation control module, a driving current containing modulation information is generated. This driving current is applied to a high-speed laser to generate an optical power waveform corresponding to the voltage of the volumetric target echo electrical signal, achieving arbitrary waveform modulation, such as... Figure 5 .

[0147] The arbitrary laser echo generation module consists of a control signal input interface, a drive circuit, a semiconductor laser, an optical fiber attenuator, and an optical fiber output interface, such as... Figure 6 As shown. Its working principle and process:

[0148] 1. The simulated signal of the target body is transmitted to the drive circuit through the coaxial cable and MCX interface.

[0149] 2. The driving circuit generates a simulated current for the target volume and inputs it into the laser.

[0150] 3. The laser generates a simulated light pulse for the target and inputs it to the fiber optic attenuator through an optical fiber.

[0151] 4. The attenuated target simulated optical pulse is output through the optical fiber interface.

[0152] In designing the drive circuit, the requirements for the rising edge, falling edge, and saturation signal of the optical pulse during laser target echo generation are fully considered, ensuring that the target echo electrical signal is linearly and without distortion applied to the optical signal. To achieve a fast rising edge, fast power devices, a high-speed D / A converter, and a high-frequency operational amplifier are selected. Simultaneously, the exponential charging effect of the capacitor is utilized to achieve a smooth transition at the top of the circuit. To achieve a steep falling edge initially, which gradually decreases to zero near the end, in addition to the normal pulse reference voltage dropping to 0, an anti-correlation interruption pulse is added to the inverting input of the operational amplifier to accelerate the discharge speed of the control circuit. In the discharge section of the power drive circuit, the discharge speed is adjusted to ensure that the backlash is not excessive. To prevent excessive pulse width, hardware circuitry is used to monitor each pulse individually. When the maximum pulse width is exceeded, the monitoring circuit activates, pulling down the power control circuit. A positive feedback circuit is also used to accelerate the circuit's operation.

[0153] The selection of fiber optic attenuators fully considers the large dynamic range of the laser target echo signal amplitude, and a MEMS digitally adjustable fiber optic attenuator is adopted.

[0154] In summary, this embodiment utilizes a lidar volume target echo simulation system to select a volume target simulation model matching the volume target from a typical target model library. It then uses lidar to simulate the multi-channel optical characteristics of the volume target, generating volume target echo simulation data for typical targets under different intersection conditions. The lidar volume target echo generation module performs pulse echo detection with a half-bandwidth of nanoseconds based on the volume target echo simulation data. It converts the pulse current signal into an electrical pulse signal without distortion, and then converts the electrical pulse signal into an optical pulse signal without distortion, modulating the optical pulse power within a single pulse in real time. This solves the problems of current lidar point target echo generation devices, which generate simple target echo characteristics, making it difficult to simulate the true characteristics of the echo, and resulting in low accuracy of target echo characteristics due to the limited simulation of intersection conditions. It also addresses the issues of missing near-range information in target echo characteristics, the limited target representation, and high experimental costs. This device employs a combination of hardware and software. It uses a lidar target echo simulation system to generate simulation data and a lidar target echo generation module to regenerate the target echo optical signal. This combination of hardware and software enables real-time simulation of lidar target echoes under complex intersection conditions, providing richer and more comprehensive performance verification for lidar products. Specific Implementation Example 3:

[0156] This embodiment provides a method for generating target echoes using a lidar system. (See also...) Figure 7 ,include:

[0157] Step 702: The lidar volume target echo simulation system selects a volume target simulation model that matches the volume target from a pre-established typical target model library; based on the volume target simulation model, the lidar is used to simulate the multi-channel optical characteristics of the volume target, generating volume target echo simulation data of typical targets under different intersection conditions.

[0158] Specifically, one implementation of step 702 can be:

[0159] S21. Establish a typical target model library, wherein the typical target model library is a target three-dimensional solid model constructed using the surface element method, wherein the target three-dimensional solid model includes coordinate system definition method, surface element number, mesh size, skin material, coating color, and reflectivity;

[0160] S22. Select a volume target simulation model that matches the volume target from the typical target model library;

[0161] S23. Set up the lidar model and configure the lidar multi-channel parameters;

[0162] S24. Using the aforementioned lidar model and target simulation model, simulate lidar illuminating the target from multiple angles and acquire multi-channel echo data;

[0163] S25. Based on the multi-channel echo data and combined with preset intersection conditions, calculate the intersection trajectory and the area of ​​the irradiated region, and then determine the echo power of each surface element.

[0164] Step 704: The lidar target echo generation module performs pulse echo detection with a half-bandwidth of nanoseconds based on the target echo simulation data; it converts the pulse current signal into an electrical pulse signal without distortion, and then converts the electrical pulse signal into an optical pulse signal without distortion, modulating the optical pulse power within a single pulse in real time to achieve arbitrary laser waveform modulation.

[0165] Specifically, one implementation of step 704 can be:

[0166] S41. Convert the optical pulse input from the optical fiber into a TTL electrical pulse signal and transmit it to the control system through the port;

[0167] S42. The laser radar target echo data is converted into electrical pulse signals through a DAC. The DAC output signal is filtered, power controlled, and amplified. Then, the 1 control signal is output to N channels in a time-division manner through a 1×N terminal switching matrix.

[0168] S43. Convert the volume target echo electrical pulse signal into an optical pulse signal, modulate the optical pulse signal power according to the amplitude of the volume target echo electrical signal, modulate the optical pulse power within a single pulse in real time, and linearly load the volume target echo electrical signal onto the optical signal without distortion.

[0169] Specifically, based on the characteristics of the volume target echo, optical radio technology is used. The volume target echo electrical signal is driven by a driving circuit to increase its driving capability. Then, through an electro-optic modulation control module, a driving current containing modulation information is generated. The driving current is applied to a high-speed laser to generate an optical power waveform corresponding to the voltage of the volume target echo electrical signal, thereby realizing arbitrary waveform modulation.

[0170] In summary, this embodiment utilizes a lidar volume target echo simulation system to select a volume target simulation model matching the volume target from a typical target model library. It then uses lidar to simulate the multi-channel optical characteristics of the volume target, generating volume target echo simulation data for typical targets under different intersection conditions. The lidar volume target echo generation module performs pulse echo detection with a half-bandwidth of nanoseconds based on the volume target echo simulation data. It converts the pulse current signal into an electrical pulse signal without distortion, and then converts the electrical pulse signal into an optical pulse signal without distortion, modulating the optical pulse power within a single pulse in real time. This solves the problems of current lidar point target echo generation devices, which generate simple target echo characteristics, making it difficult to simulate the true characteristics of the echo, and resulting in low accuracy of target echo characteristics due to the limited simulation of intersection conditions. It also addresses the issues of missing near-range information in target echo characteristics, the limited target representation, and high experimental costs. This device employs a combination of hardware and software. It uses a lidar target echo simulation system to generate simulation data and a lidar target echo generation module to regenerate the target echo optical signal. This combination of hardware and software enables real-time simulation of lidar target echoes under complex intersection conditions, providing richer and more comprehensive performance verification for lidar products. Specific Implementation Example 4:

[0172] This embodiment provides a lidar target echo generation device, which specifically includes the following:

[0173] Due to the lack of research on the echo characteristics of volume targets under complex intersection conditions, intersection conditions are often simplified and point targets are used instead of volume targets, resulting in the loss of key information on target echo characteristics. To address the problem of missing echo characteristic information for point targets, a system is designed to simulate the echo of volume targets from a lidar system under complex intersection conditions.

[0174] First, establish a library of typical target models, covering three-dimensional target models and target surface material reflection characteristic models.

[0175] Then, based on the spectral characteristics of the high repetition rate and narrow pulse width lidar, the energy, position, and size of the laser spot on the target illuminated by the lidar under different intersection conditions are calculated.

[0176] Finally, the atmospheric transmission characteristics of the lidar were analyzed, and simulation data of the volume target echo of the lidar to typical targets under different intersection conditions were generated.

[0177] Furthermore, in response to the limitations of the current target echo production module, a lidar volume target echo generation module was designed; it can generate simulation data based on the lidar volume target echo simulation system, and realize the generation of arbitrary laser echoes with high precision.

[0178] First, a pulse echo detection module is designed to achieve pulse echo detection with a half-bandwidth in the nanosecond range. This ensures that the pulse waveform is distortion-free during the conversion of the pulse current signal to a voltage signal, and that the laser triggering moment is error-free.

[0179] Then, a target echo electrical signal generation module was designed to convert the laser radar target echo into an electrical pulse signal, ensuring that the waveform is not distorted during the conversion process.

[0180] Finally, an arbitrary laser echo generation module was designed to achieve arbitrary laser waveform modulation. In the conversion process from the volume target echo electrical signal to the optical pulse signal, the problem of the laser requiring a certain amount of energy accumulation and triggering time to switch from off to on state was overcome, enabling the optical pulse rising edge to follow the input electrical pulse signal; it also overcame the complexity of the volume target echo signal, achieving a wide dynamic range of optical pulse power generation.

[0181] Furthermore, this embodiment also provides a workflow for generating laser radar volume target echoes, specifically as follows:

[0182] The first step is to run the lidar target echo simulation system.

[0183] The second step is to set the target model, lidar model, and intersection conditions according to the experimental or testing requirements, and generate lidar volume target echo simulation data.

[0184] The third step is to save the simulation data in the lidar target generation device.

[0185] The fourth step is to run the lidar target echo generation module.

[0186] Fifth, the light pulse signal emitted by the lidar is transmitted to the pulse echo detection module through optical fiber.

[0187] The sixth step involves the pulse echo detection module converting the optical signal into an electrical signal (trigger signal) and transmitting the trigger signal to the volume target echo generation module.

[0188] Step 7: After receiving the trigger signal, the target echo generation module control system calls the laser radar target echo simulation data, generates the laser radar target echo electrical signal, and transmits it to any laser echo generation module.

[0189] Step 8: The arbitrary laser echo generation module generates the laser radar target echo light signal, which is then controlled by an electrically controlled fiber optic attenuator to complete the laser echo amplitude modulation control before being coupled to the optical fiber.

[0190] The ninth step involves transmitting the light to the lidar receiving module via optical fiber.

[0191] In summary, this embodiment utilizes a lidar volume target echo simulation system to select a volume target simulation model matching the volume target from a typical target model library. It then uses lidar to simulate the multi-channel optical characteristics of the volume target, generating volume target echo simulation data for typical targets under different intersection conditions. The lidar volume target echo generation module performs pulse echo detection with a half-bandwidth of nanoseconds based on the volume target echo simulation data. It converts the pulse current signal into an electrical pulse signal without distortion, and then converts the electrical pulse signal into an optical pulse signal without distortion, modulating the optical pulse power within a single pulse in real time. This solves the problems of current lidar point target echo generation devices, which generate simple target echo characteristics, making it difficult to simulate the true characteristics of the echo, and resulting in low accuracy of target echo characteristics due to the limited simulation of intersection conditions. It also addresses the issues of missing near-range information in target echo characteristics, the limited target representation, and high experimental costs. This device employs a combination of hardware and software. It uses a lidar target echo simulation system to generate simulation data and a lidar target echo generation module to regenerate the target echo optical signal. This combination of hardware and software enables real-time simulation of lidar target echoes under complex intersection conditions, providing richer and more comprehensive performance verification for lidar products.

[0192] The above description is merely a preferred embodiment of this specification and is not intended to limit this specification. Various modifications and variations can be made to this specification by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this specification should be included within the scope of protection of this specification.

Claims

1. A laser radar target echo generation device, characterized in that, include: LiDAR target echo simulation system and LiDAR target echo generation module; The lidar volume target echo simulation system is used to select a volume target simulation model that matches the volume target from a pre-established library of typical target models; based on the volume target simulation model, the lidar is used to simulate the multi-channel optical characteristics of the volume target, and generate volume target echo simulation data of the lidar for typical targets under different intersection conditions. The lidar target echo generation module is used to perform pulse echo detection with a half bandwidth of nanoseconds based on the target echo simulation data; it converts the pulse current signal into an electrical pulse signal without distortion, and then converts the electrical pulse signal into an optical pulse signal without distortion, and modulates the optical pulse power within a single pulse in real time to achieve arbitrary laser waveform modulation.

2. The apparatus according to claim 1, characterized in that, The lidar target echo simulation system includes: a target model library establishment unit, a target model screening unit, a lidar model and parameter configuration unit, a target characteristic simulation unit, and an echo power calculation unit, wherein: The target model library establishment unit is used to establish a typical target model library, wherein the typical target model library is a target three-dimensional solid model constructed using the surface element method, wherein the target three-dimensional solid model includes coordinate system definition method, surface element number, mesh size, skin material, coating color, and reflectivity; The volume target model screening unit is used to screen out volume target simulation models that match the volume target from the typical target model library; The lidar model and parameter configuration unit is used to set the lidar model and set the lidar multi-channel parameters. The target characteristic simulation unit is used to simulate the laser radar illuminating the target from multiple angles and to acquire multi-channel echo data using the laser radar model and the target simulation model. The echo power calculation unit is used to calculate the intersection trajectory and the area of ​​the irradiated region based on the multi-channel echo data and the preset intersection conditions, and then determine the echo power of each surface element.

3. The apparatus according to claim 2, characterized in that, The typical target model library covers target 3D models and target surface material reflection property models.

4. The apparatus according to claim 3, characterized in that, The multi-channel parameters of the lidar include the number of lidar channels, the included angle of the multi-channel lidar, the lidar wavelength, the coordinate system of the transmitting module, the tilt angle of the transmitting module, the field of view of the transmitting module, the transmitting power, the transmitting pulse width, the repetition frequency, the coordinate system of the receiving module, the tilt angle of the receiving module, the field of view of the receiving module, the optical aperture of the receiving module, and the photoelectric responsivity of the receiving module. The rendezvous conditions include: lidar starting point, lidar velocity, lidar attitude, target starting point, target velocity, and target attitude.

5. The apparatus according to claim 4, characterized in that, The volume target characteristic simulation unit is specifically used for: Based on the characteristics of volume target echoes, a rich target optical model library is established to calculate the multi-channel volume target echoes of lidar in complex intersection scenarios. The echo power calculation unit is specifically used for: The detection situation is determined by combining the intersection conditions, the position of each channel, the tilt angle and the field of view. The area of ​​the target illuminated area and the effective echo power received by the lidar are counted, and the multi-channel target echo data are saved.

6. The system according to claim 5, characterized in that, The lidar target echo generation module includes: a pulse echo detection module, a target echo electrical signal generation module, and an arbitrary laser echo generation module; The pulse echo detection module, the volume target echo electrical signal generation module, and the arbitrary laser echo generation module are connected in sequence. The pulse echo detection module is used to convert the optical pulse input from the optical fiber into a TTL electrical pulse signal and transmit it to the control system through the port; The target echo electrical signal generation module is used to convert the laser radar target echo data into electrical pulse signals through a DAC, filter, control the power, and amplify the DAC output signal, and then output one control signal in N time-division multiplexing through a 1×N terminal switching matrix. The arbitrary laser echo generation module is used to convert the volume target echo electrical pulse signal into an optical pulse signal, modulate the optical pulse signal power according to the amplitude of the volume target echo electrical signal, modulate the optical pulse power within a single pulse in real time, and linearly load the volume target echo electrical signal onto the optical signal without distortion.

7. The apparatus according to claim 6, characterized in that, The arbitrary laser echo generation module is specifically used for: Based on the characteristics of the target echo, optical radio technology is used. The target echo electrical signal is driven by a driving circuit to increase its driving capability. Then, through an electro-optic modulation control module, a driving current containing modulation information is generated. The driving current is applied to a high-speed laser to generate an optical power waveform corresponding to the voltage of the target echo electrical signal, thus realizing arbitrary waveform modulation.

8. The apparatus according to claim 7, characterized in that, The target echo signal generation module includes: a DAC model, a filtering module, a power amplification module, and a 1×N terminal switch matrix.

9. The apparatus according to claim 8, characterized in that, The arbitrary laser echo generation module includes: a driving circuit, a laser, and an attenuator.

10. A method for generating laser radar target echoes, applied to the apparatus according to any one of claims 1 to 9, characterized in that, include: The lidar volume target echo simulation system selects a volume target simulation model that matches the volume target from a pre-established library of typical target models; based on the volume target simulation model, it uses lidar to simulate the multi-channel optical characteristics of the volume target, generating volume target echo simulation data of typical targets under different intersection conditions. The lidar target echo generation module performs pulse echo detection with a half-bandwidth of nanoseconds based on the target echo simulation data; it converts the pulse current signal into an electrical pulse signal without distortion, and then converts the electrical pulse signal into an optical pulse signal without distortion, modulating the optical pulse power within a single pulse in real time to achieve arbitrary laser waveform modulation.

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