Laser echo simulation device and method

Abstract

The invention provides a laser echo simulation device and method which can be applied to the technical field of laser. The device comprises a pulse generation module used for generating an analog pulse electric signal. The echo modulation module comprises a laser used for outputting a reference laser signal; the interferometer is used for modulating the reference laser signal under the action of the analog pulse electric signal to generate a first intermediate laser signal; the beam splitter is used for splitting the first intermediate laser signal to obtain a first laser echo signal and a second intermediate laser signal; the modulator is used for modulating the wavelength and the polarization state of the second intermediate laser signal to obtain a second laser echo signal and a third laser echo signal. And the echo output module is used for outputting laser echo signals fed back to the tested laser radar, the laser echo signals comprise a first laser echo signal, a second laser echo signal or a third laser echo signal, and the laser echo signals are used for testing the performance of the tested laser radar.

Description

Technical Field

[0001] This disclosure relates to the field of laser technology, and more specifically, to a laser echo simulation apparatus and method. Background Technology

[0002] LiDAR is widely used in aerospace, surveying and mapping, and autonomous driving. Performance testing of LiDAR requires a laser echo simulation device.

[0003] Among related technologies, laser echo simulation devices have relatively low testing efficiency. Summary of the Invention

[0004] In view of this, embodiments of the present disclosure provide a laser echo simulation apparatus and method.

[0005] One aspect of this disclosure provides a laser echo simulation device, including a pulse generation module, an echo modulation module, and an echo output module. The pulse generation module generates an analog pulse electrical signal. The echo modulation module includes a laser, an interferometer, a beam splitter, and a modulator. The laser outputs a reference laser signal; the interferometer modulates the reference laser signal under the action of the analog pulse electrical signal to generate a first intermediate laser signal; the beam splitter splits the first intermediate laser signal to obtain a first laser echo signal and a second intermediate laser signal, wherein the wavelength of the first laser echo signal is a first wavelength; the modulator modulates the wavelength and polarization state of the second intermediate laser signal to obtain a second laser echo signal and a third laser echo signal, wherein the wavelengths of the second and third laser echo signals are second wavelengths, and the polarization states of the second and third laser echo signals are different. The echo output module is used to output a laser echo signal fed back to the lidar under test. The laser echo signal includes the first laser echo signal, the second laser echo signal, or the third laser echo signal. The laser echo signal is used to test the performance of the lidar under test.

[0006] According to an embodiment of this disclosure, the modulator includes: a wavelength modulator for modulating the wavelength of the second intermediate laser signal to obtain a third intermediate laser signal; and a polarization controller for modulating the polarization state of the third intermediate laser signal to obtain the second laser echo signal and the third laser echo signal.

[0007] According to an embodiment of the present disclosure, the wavelength modulator includes: a frequency multiplier for multiplying the second intermediate laser signal to obtain a mixed laser echo signal having the first wavelength and the second wavelength; and a beam splitter for separating the second wavelength signal from the mixed laser echo signal to obtain the third intermediate laser signal.

[0008] According to an embodiment of this disclosure, the polarization controller includes: a half-wave plate for adjusting the components of different polarization states in the third intermediate laser signal; and a polarization beam splitter for separating the different polarization states of the third intermediate laser signal to obtain the second laser echo signal and the third laser echo signal.

[0009] According to an embodiment of this disclosure, the echo modulation module further includes: a compensator, configured to respond to the nonlinear distortion generated by the first intermediate laser signal, input the first intermediate laser signal into a nonlinear distortion function to generate a compensation electrical signal, and perform pre-distortion compensation on the analog pulse electrical signal according to the compensation electrical signal.

[0010] According to an embodiment of this disclosure, the echo modulation module further includes: a power monitoring module, configured to monitor the power of at least one of the first laser echo signal, the second laser echo signal, or the third laser echo signal, and to send an adjustment signal to the first fiber optic attenuator in response to the power not being a first preset power; the first fiber optic attenuator is configured to adjust the power of at least one of the first laser echo signal, the second laser echo signal, or the third laser echo signal to the first preset power in response to the adjustment signal.

[0011] According to an embodiment of this disclosure, the pulse generation module includes: a controller, configured to delay the arrival time of the laser indicated by the received laser trigger signal by a simulated duration to obtain a trigger timing signal, wherein the simulated duration is determined based on the simulated distance between the lidar and the target; and a digital-to-analog converter, configured to read pre-stored echo waveform data from the controller in response to the trigger timing signal and convert the echo waveform data into the simulated pulse electrical signal, wherein the echo waveform data is determined based on at least one of an atmospheric transmission model or physical parameters of the target.

[0012] According to an embodiment of this disclosure, the device further includes: a laser receiving module, configured to receive an emitted laser signal emitted by a lidar, and generate a laser trigger signal based on the emitted laser signal.

[0013] According to an embodiment of this disclosure, the laser receiving module includes: an off-axis laser receiving mirror for quasi-directly receiving the emitted laser signal emitted by the lidar; a second fiber optic attenuator for adjusting the power of the emitted laser signal to a second preset power; and a photodetector for generating a laser trigger signal based on the reception time of the emitted laser signal.

[0014] According to an embodiment of this disclosure, the apparatus further includes a control module for controlling the temperature of the echo modulation module within a predetermined temperature range.

[0015] According to an embodiment of this disclosure, the echo output module includes: an indicator light module for generating an indicator laser signal, wherein the indicator laser signal is visible light; a multiplexer for determining the laser echo signal from the indicator laser signal, the first laser echo signal, the second laser echo signal, or the third laser echo signal; an off-axis reflector for collimating the laser echo signal; and an electrically controlled turntable for controlling the angle of the laser echo signal.

[0016] Another aspect of this disclosure provides a laser echo simulation method, comprising: generating a simulated pulse electrical signal using a pulse generation module; outputting a reference laser signal using a laser included in an echo modulation module; modulating the reference laser signal under the action of the simulated pulse electrical signal using an interferometer included in the echo modulation module to generate a first intermediate laser signal; splitting the first intermediate laser signal using a beam splitter included in the echo modulation module to obtain a first laser echo signal and a second intermediate laser signal, wherein the wavelength of the first laser echo signal is a first wavelength; modulating the wavelength and polarization state of the second intermediate laser signal using a modulator included in the echo modulation module to obtain a second laser echo signal and a third laser echo signal, wherein the wavelengths of the second laser echo signal and the third laser echo signal are second wavelengths, and the polarization states of the second laser echo signal and the third laser echo signal are different; and outputting a laser echo signal using an echo output module, wherein the laser echo signal includes the first laser echo signal, the second laser echo signal, or the third laser echo signal.

[0017] According to embodiments of this disclosure, in a laser echo simulation device, a pulse generation module generates a corresponding analog pulse electrical signal to modulate an interferometer based on the echo simulation requirements. In the echo modulation module, a reference laser signal is output from a laser. Under the action of the analog pulse electrical signal, the reference laser signal is modulated by an interferometer to generate a first intermediate laser signal with a wavelength of a first wavelength, thus achieving modulation of the first intermediate laser signal according to the echo simulation requirements. A beam splitter is used to split the first intermediate laser signal into a first laser echo signal and a second intermediate laser signal. A modulator is used to modulate the wavelength and polarization state of the second intermediate laser signal. By modulating the wavelength and polarization state of the second intermediate laser signal, a second laser echo signal and a third laser echo signal with a wavelength of a second wavelength are obtained. The second and third laser echo signals have different polarization states, thus generating laser echo signals with different wavelengths and polarization states. An echo output module selects the first, second, or third laser echo signal as the laser echo signal to be fed back to the lidar under test, thereby achieving the output of a laser echo signal. The laser echo simulation device can generate and feed back multi-wavelength laser echo signals with polarization control, thereby adapting to the testing requirements of multi-wavelength lidar and improving testing efficiency. Attached Figure Description

[0018] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments of the disclosure with reference to the accompanying drawings, in which the accompanying drawings are shown.

[0019] Figure 1 A schematic diagram of a laser echo simulation system in the related art is shown.

[0020] Figure 2 A schematic diagram of a laser echo simulation apparatus according to an embodiment of the present disclosure is shown.

[0021] Figure 3 A schematic diagram illustrating pre-compensation of an interferometer according to an embodiment of the present disclosure is shown.

[0022] Figure 4 A schematic diagram of a laser receiving module according to an embodiment of the present disclosure is shown.

[0023] Figure 5 A schematic diagram of a laser echo simulation apparatus according to an embodiment of the present disclosure is shown.

[0024] Figure 6 The diagram illustrates a signal trigger detection module determining the arrival time of a laser trigger signal according to an embodiment of the present disclosure.

[0025] Figure 7A schematic diagram illustrating the generation of an analog pulse electrical signal by a pulse generation module according to an embodiment of the present disclosure is shown.

[0026] Figure 8 A schematic diagram of an echo output module according to an embodiment of the present disclosure is shown.

[0027] Figure 9 A flowchart illustrating a laser echo simulation method according to an embodiment of the present disclosure is shown schematically. Detailed Implementation

[0028] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0029] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0030] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0031] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0032] The performance of lidar can be tested using a laser echo simulation device. This device generates a laser echo signal upon receiving the laser signal emitted by the lidar under test, simulating the laser echo signal generated after the laser signal illuminates a target object under different distances or reflectivities.

[0033] In some schemes, the laser echo simulation device can control the laser to generate a laser signal through a laser echo control signal, and then generate the required laser echo signal after beam shaping.

[0034] Figure 1 A schematic diagram of a laser echo simulation system in the related art is shown.

[0035] like Figure 1 As shown, the laser echo simulation system in related technologies may include a host computer, a laser echo controller, and a laser echo simulator. The host computer sends control commands to the laser echo controller via a serial port, transmits these commands to the encoding signal generation module through the communication control module in the laser echo controller, generates a laser signal through the laser diode driving module in the laser echo simulator, and uses the beam shaping system in the laser echo simulator to generate the required laser echo signal. The host computer receives the conditioning results from the self-test feedback signal conditioning module through the communication control module, thus enabling the laser echo controller to perform a self-test.

[0036] In related technologies, laser signals generated via laser diode drive modules suffer from insufficient time delay accuracy, making it difficult to meet the sub-nanosecond time control requirements of lidar. Preset simulation functions implemented using fixed analog circuits are limited in functionality. Furthermore, generating a single-band laser echo signal makes it difficult to control the polarization state of the laser echo signal.

[0037] Using a fixed analog circuit to generate laser echo signals for lidar performance testing makes it difficult to control the polarization state of the laser echo signals and adapt to the testing requirements of multi-wavelength lidars, thus reducing testing efficiency.

[0038] In view of this, embodiments of the present disclosure provide a laser echo simulation apparatus and method.

[0039] For ease of understanding, Figure 2 The laser echo simulation apparatus provided in the embodiments of this disclosure has been described in general. The following will use... Figure 2 Taking the laser echo simulation device shown as an example, combined with the attached... Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 and Figure 9 The laser echo simulation device described in the embodiments of this application will be further described. Specifically, Figure 3 The process of pre-compensating the interferometer for the echo modulation module is explained. Figure 4 The laser receiving module in the laser echo simulation device is described. Figure 5 The laser echo simulation device was further explained. Figure 6The method for determining the arrival time of the laser trigger signal using the signal trigger detection module is explained. Figure 7 The generation of analog pulse electrical signals by the pulse generation module is explained. Figure 8 The echo output module in the laser echo simulation device is explained. Figure 9 The laser echo simulation method is explained.

[0040] Figure 2 A schematic diagram of a laser echo simulation apparatus according to an embodiment of the present disclosure is shown.

[0041] like Figure 2 As shown, the laser echo simulation device may include a pulse generation module, an echo modulation module, and an echo output module. The echo modulation module may include a laser, an interferometer, a beam splitter, and a modulator.

[0042] The pulse generation module can be used to generate analog pulse electrical signals. For example, the pulse generation module can generate analog pulse electrical signals according to preset parameters based on the testing requirements of the lidar under test. The analog pulse electrical signals can be used as driving signals for laser echo simulation.

[0043] Lasers can be used to output reference laser signals. To achieve stable and accurate interferometric modulation, the reference laser signal needs to possess single-frequency characteristics and a stable frequency; therefore, a single-frequency laser signal can be generated using a laser as the reference laser signal. For example, a narrow-linewidth fiber laser with an output wavelength of 1064 nm can be used, which can output a P-polarized single-frequency laser source. The 1064 nm P-polarized reference laser signal output by the laser is transmitted to the interferometer through a polarization-maintaining fiber to maintain the polarization state of the reference laser signal during transmission. Furthermore, the laser incorporates a relative intensity noise suppression module to reduce intensity noise in the reference laser signal, ensuring that the power jitter of the reference laser signal is less than 0.2%, thereby improving the stability of the reference laser signal.

[0044] An interferometer can be used to modulate a reference laser signal under the action of an analog pulse electrical signal to generate a first intermediate laser signal.

[0045] Under the influence of a simulated pulsed electrical signal, the reference laser signal transmitted in the interferometer can change, thereby generating a first intermediate laser signal. One implementation method is a Mach-Zehnder interferometer. A Mach-Zehnder interferometer has two interferometer arms. When the reference laser signal is input to the input port of the Mach-Zehnder interferometer, the reference laser signal is split into two laser signals of equal power. After passing through the two interferometer arms, the two laser signals are recoupled and output at the output port of the Mach-Zehnder interferometer. The phase of the optical signal transmitted in the interferometer arms can be adjusted by controlling the arm length. This allows for the output of a laser signal with continuously changing intensity. Therefore, a Mach-Zehnder interferometer can be used to modulate the reference laser signal under the influence of a simulated pulsed electrical signal.

[0046] Electro-optic materials change their internal optical properties in response to changes in the applied electric field, and this change is reversible and fast-responding, thus enabling the material to quickly recover its optical properties after the applied electric field is removed.

[0047] Based on the above, a Mach-Zehnder interferometer can be constructed using electro-optic materials. The arm length of the Mach-Zehnder interferometer constructed using electro-optic materials varies with the simulated pulse electrical signal. By applying a varying simulated pulse electrical signal to the arm of the Mach-Zehnder interferometer, the change in the simulated pulse electrical signal is converted into a change in the optical signal, thereby modulating the reference laser signal and generating the first intermediate laser signal.

[0048] A beam splitter can be used to split the first intermediate laser signal into two beams, resulting in a first laser echo signal and a second intermediate laser signal.

[0049] As one implementation method, the beam splitter can be a fiber optic beam splitter. Therefore, by using a fiber optic beam splitter, the first intermediate laser signal can be split into two beams while keeping the first wavelength unchanged, resulting in a first laser echo signal and a second intermediate laser signal. In other words, the wavelengths of the first intermediate laser signal, the first laser echo signal, and the second intermediate laser signal are all the same as the first wavelength. When using a narrow-linewidth fiber laser with an output wavelength of 1064 nm, the first wavelength is 1064 nm.

[0050] The modulator can be used to modulate the wavelength and polarization state of the second intermediate laser signal to obtain the second laser echo signal and the third laser echo signal.

[0051] The modulator can modulate the wavelength of the second intermediate laser signal to obtain a second laser echo signal and a third laser echo signal with the second wavelength. The modulator can also modulate the polarization state of the second intermediate laser signal, so that the second laser echo signal and the third laser echo signal have different polarization states.

[0052] The echo output module can be used to output the laser echo signal fed back to the lidar under test.

[0053] When testing the performance of a lidar under test (DUT), a laser echo signal can be fed back to the DUT to test its performance. Therefore, in the echo output module, a laser echo signal of different wavelengths or polarization states can be selected to be fed back to the DUT according to the testing requirements. The laser echo signal can include a first laser echo signal, a second laser echo signal, or a third laser echo signal.

[0054] According to embodiments of this disclosure, in a laser echo simulation device, a pulse generation module generates a corresponding analog pulse electrical signal to modulate an interferometer based on the echo simulation requirements. In the echo modulation module, a reference laser signal is output from a laser. Under the action of the analog pulse electrical signal, the reference laser signal is modulated by an interferometer to generate a first intermediate laser signal with a wavelength of a first wavelength, thus achieving modulation of the first intermediate laser signal according to the echo simulation requirements. A beam splitter is used to split the first intermediate laser signal into a first laser echo signal and a second intermediate laser signal. A modulator is used to modulate the wavelength and polarization state of the second intermediate laser signal. By modulating the wavelength and polarization state of the second intermediate laser signal, a second laser echo signal and a third laser echo signal with a wavelength of a second wavelength are obtained. The second and third laser echo signals have different polarization states, thus generating laser echo signals with different wavelengths and polarization states. An echo output module selects the first, second, or third laser echo signal as the laser echo signal to be fed back to the lidar under test, thereby achieving the output of a laser echo signal. The laser echo simulation device can generate and feed back multi-wavelength laser echo signals with polarization control, thereby adapting to the testing requirements of multi-wavelength lidar and improving testing efficiency.

[0055] According to embodiments of this disclosure, the laser echo simulation device may further include a laser receiving module. The laser receiving module can be used to receive the emitted laser signal from the lidar and generate a laser trigger signal based on the emitted laser signal.

[0056] When testing the performance of a lidar, it is necessary to first use the laser receiving module of a laser echo simulation device to receive the emitted laser signal from the lidar under test. Once the laser echo simulation device receives the emitted laser signal, it performs a laser echo simulation.

[0057] According to an embodiment of this disclosure, after the lidar under test emits a laser signal, it is received by a laser receiving module, which records the receiving time and generates a laser trigger signal. The laser trigger signal is then used to provide a start signal for the pulse generation module and the echo modulation module in the laser echo simulation device.

[0058] According to embodiments of this disclosure, the laser echo simulation device may further include a control module. The control module can be used to control the temperature of the echo modulation module within a predetermined temperature range.

[0059] The predetermined temperature range can be the temperature range within which each component in the laser echo simulation device can operate stably.

[0060] In environments with varying temperatures, the length of the interferometer's arms in the echo modulation module changes, thus reducing the modulation accuracy of the reference laser signal. Furthermore, the accuracy of other components in the echo modulation module is also affected by temperature variations. Therefore, the control module can utilize active temperature control to maintain the temperatures of the laser, interferometer, beam splitter, and modulator within a predetermined range, thereby achieving stable laser echo modulation.

[0061] To achieve temperature detection, temperature sensors can be used to acquire the temperature of each component. For example, a thermistor or resistance temperature detector can be used to acquire the temperature of each component. Based on the temperature acquired by the temperature sensor, the control module can use active temperature control to maintain the temperature of the echo control module within a predetermined temperature range. The control module can be a control system with a microcontroller, such as a Field Programmable Gate Array (FPGA). If the control module determines that the temperature is not within the predetermined temperature range, it will use active temperature control to bring the temperature of the echo control module back within the predetermined temperature range.

[0062] As one implementation method, active temperature control can include using temperature control commands determined by a proportional-integral-derivative (PID) control algorithm to control the heating or cooling of the thermoelectric cooler (TEC) so that the temperature of the echo modulation module is within a predetermined temperature range.

[0063] In addition, to ensure that the temperature of the echo modulation module remains within a predetermined temperature range, a heat dissipation unit can be incorporated into the echo modulation module to effectively dissipate the heat generated by the module. The heat dissipation unit may include at least one of a heat sink or a heat dissipation unit.

[0064] According to embodiments of this disclosure, the temperature of the echo modulation module is stabilized within a predetermined temperature range by a control module, thereby ensuring that the components in the echo modulation module have a stable operating temperature and reducing the adverse effects of temperature fluctuations on the laser echo simulation device.

[0065] According to embodiments of this disclosure, the pulse generation module may include a controller and a digital-to-analog converter.

[0066] The controller can be used to simulate the delay duration of the laser arrival time indicated by the received laser trigger signal to obtain the trigger timing signal.

[0067] The simulation duration can be determined based on the simulated distance between the lidar and the target.

[0068] The controller can receive and store echo waveform data from different targets. Upon receiving a laser trigger signal, the controller determines the simulation duration based on the distance between the measured lidar and the target. Based on the laser arrival time indicated by the trigger signal and the simulation duration, the generation time of the trigger timing signal is obtained. This trigger timing signal can serve as the starting point for the digital-to-analog converter to generate the analog pulse electrical signal.

[0069] One implementation method is to use an FPGA as the controller, which can receive and store external input data. Utilizing the powerful computing capabilities of the FPGA, it can calculate the simulation duration based on the distance between the LiDAR being measured and the target object, with a simulation duration accuracy of 100 ps.

[0070] Since the laser echoes generated by lidar detection of different targets are different, simulating laser echoes from different targets requires generating corresponding simulated pulse electrical signals using different echo waveform data to modulate the interferometer. For example, a custom waveform with a step size of 0.5 ns can be used to simulate the laser echo generated by lidar illuminating a target, thereby generating the corresponding laser echo signal. Therefore, the controller can receive and store external echo waveform data, and during laser echo simulation, determine the echo waveform data corresponding to the target. The simulation duration is determined based on the distance between the lidar under test and the target, and the laser arrival time is delayed by the simulation duration to determine the generation time of the trigger timing signal.

[0071] A digital-to-analog converter can be used to read pre-stored echo waveform data from a controller in response to a trigger timing signal and convert the echo waveform data into an analog pulse electrical signal. The echo waveform data can be determined based on at least one of an atmospheric transmission model or the physical parameters of the target object.

[0072] A digital-to-analog converter (DAC) can read pre-stored echo waveform data from the controller and convert the digital echo waveform data into analog signal form. DACs can be high-speed DACs, enabling rapid digital-to-analog conversion to meet the testing requirements of high-precision lidar.

[0073] Different target objects have different echo waveforms. The atmospheric transmission model for the same target object also differs under different atmospheric transmission environments; therefore, the echo waveform data for the same target object will vary under different atmospheric transmission environments. Thus, echo simulation data can be determined based on the target object's physical parameters and the atmospheric transmission model.

[0074] According to embodiments of this disclosure, a controller can be used to input and store external echo waveform data and calculate the simulation duration. A digital-to-analog converter is used to read the pre-stored echo waveform data and convert it into an analog pulse electrical signal that can modulate an interferometer. This enables the laser echo simulation device to simulate complex laser echoes and provides high accuracy in controlling the delay simulation duration.

[0075] According to embodiments of this disclosure, the echo modulation module may further include a compensator.

[0076] The compensator can be used to respond to the nonlinear distortion generated by the first intermediate laser signal, input the first intermediate laser signal into the nonlinear distortion function, generate a compensation electrical signal, and perform pre-distortion compensation on the analog pulse electrical signal according to the compensation electrical signal.

[0077] Figure 3 The illustration shows a schematic diagram of pre-compensation of the interferometer according to an embodiment of the present disclosure.

[0078] like Figure 3 As shown, the reference laser signal is input into the Mach-Zehnder interferometer through the input port. When the reference laser signal is input into the Mach-Zehnder interferometer, the reference laser signal is split into two laser signals with equal power. After passing through two interference arms, the two laser signals are recoupled and output through the output port of the Mach-Zehnder interferometer.

[0079] When an interferometer modulates a reference laser signal under the action of a simulated pulse electrical signal V(t), the interferometer's own nonlinear response causes nonlinear distortion in the first intermediate laser signal. Therefore, it is necessary to pre-construct a nonlinear distortion function to compensate for this distortion. To construct the nonlinear distortion function, the first intermediate laser signal output from the interferometer is input into the nonlinear distortion function to generate the compensation electrical signal V. b By compensating the electrical signal V bPre-distortion compensation is applied to the analog pulse electrical signal so that the interferometer can output an approximately linear first intermediate laser signal.

[0080] Taking the Mach-Zehnder interferometer as an example, the nonlinear distortion function can be constructed in the following way.

[0081] First, the laser signals output by the Mach-Zehnder interferometer under different input voltages were obtained through experimental measurements. By analyzing the output laser signals, the nonlinearity of the interferometer's output laser signal can be determined. The relationship between the output laser signal of the Mach-Zehnder interferometer and the applied analog pulse electrical signal can satisfy the following formula (1):

[0082] (1)

[0083] Among them, E out (t) represents the laser signal output by the Mach-Zehnder interferometer. E in The input is the reference laser signal for the Mach-Zehnder interferometer. V(t) is the voltage of the analog pulse electrical signal. π For half-wave voltage, φ b This is the bias phase.

[0084] Then, based on the nonlinearity of the laser signal output by the interferometer, an inverse function is constructed, and a mapping relationship between the first intermediate laser signal and the inverse function is established, thereby obtaining the nonlinear distortion function. In this way, a compensation electrical signal can be obtained based on the first intermediate laser signal output by the interferometer.

[0085] By performing pre-distortion compensation on the analog pulse signal using a compensation electrical signal, the Mach-Zehnder interferometer can output an approximately linear first intermediate laser signal. This allows the phase of the first intermediate laser signal to be locked within a 0.5° range, the linear range to a 60° range, and the power jitter to be less than 1%.

[0086] According to embodiments of this disclosure, a pre-distortion compensation is performed on the analog pulse signal using a compensation electrical signal, making the output of the interferometer approximately linear, thereby outputting an approximately linear first intermediate laser signal, which at least partially solves the distortion problem of the first intermediate laser signal.

[0087] According to embodiments of this disclosure, the echo modulation module may further include a power monitoring module and a first fiber optic attenuator.

[0088] The power monitoring module can be used to monitor the power of at least one of the first laser echo signal, the second laser echo signal, or the third laser echo signal, and in response to the power not being the first preset power, it sends an adjustment signal to the first fiber optic attenuator.

[0089] In one implementation, the power monitoring module can use an optical power meter to monitor the power of at least one of the first, second, or third laser echo signals. The first preset power can be a laser power pre-set according to the laser echo simulation requirements. If the power monitoring module detects that the power is not the first preset power, it sends an adjustment signal to the first fiber optic attenuator to adjust the power of the laser echo signal.

[0090] The first fiber optic attenuator can be used to adjust the power of at least one of the first laser echo signal, the second laser echo signal, or the third laser echo signal to a first preset power in response to an adjustment signal.

[0091] As one implementation, a first fiber optic attenuator can be used to attenuate the power of at least one of the first, second, or third laser echo signals. For example, the first fiber optic attenuator may include a microelectromechanical system (MEMS) based fiber optic attenuator. A MEMS fiber optic attenuator can dynamically adjust the attenuation of the laser signal by controlling the displacement of a micromirror or movable optical element via an electrical signal, thereby adjusting the power of the laser echo signal.

[0092] According to embodiments of this disclosure, a power monitoring module monitors the power of the laser echo signal output by the echo modulation module and generates an adjustment signal. A first fiber optic attenuator adjusts the power of the laser echo signal based on the adjustment signal, thereby establishing closed-loop control of the laser echo signal power and achieving power regulation of the laser echo signal output by the laser echo simulation device, thus stabilizing the power of the laser echo signal output by the laser echo simulation device.

[0093] According to embodiments of this disclosure, the laser receiving module may include an off-axis laser receiving mirror, a second fiber optic attenuator, and a photodetector.

[0094] Off-axis laser receivers can be used to receive laser signals emitted by lidar in a quasi-direct manner.

[0095] When testing the performance of a lidar system, collimation can be performed on the received laser signal to facilitate its reception by the laser receiving module. For example, an off-axis laser receiving mirror can be used to receive the laser signal emitted by the lidar. The mirror of the off-axis laser receiving mirror can be a parabolic reflector, which can collimate the laser signals emitted by lidars of different wavelengths without adjusting the position or angle of the receiving mirror.

[0096] The second fiber optic attenuator can be used to adjust the power of the emitted laser signal to a second preset power.

[0097] The second preset power can be the power between the minimum laser power that the photodetector in the laser receiving module can detect and the maximum power that the laser receiving module can withstand. In order to achieve stable operation of the laser receiving module, the power of the emitted laser signal received by the laser receiving module needs to be limited to the maximum power that the laser receiving module can withstand, and the minimum detection power requirement of the photodetector needs to be met so that the photodetector can detect the emitted laser signal.

[0098] The second fiber optic attenuator can adjust the attenuation of the emitted laser signal power as needed. For example, the second fiber optic attenuator can be a mechanically adjustable aperture attenuator, which can adjust the attenuation of the emitted laser signal power by changing the light transmission path or the blocking area through a mechanical structure.

[0099] Photodetectors can be used to generate laser trigger signals based on the timing of receiving the emitted laser signal.

[0100] Photodetectors are used to detect the emitted laser signals from lidar. To accommodate lidar systems with different wavelengths, photodetectors covering a wide wavelength range are needed to detect the emitted laser signals. For example, a silicon photoelectric free-space detector can be used, with a detection wavelength range covering 350 nm to 1100 nm, which can meet the testing requirements of lidar systems with a wide wavelength range. The photodetector receives the emitted laser signal and can generate an electrical laser trigger signal based on the optical signal of the emitted laser signal. The laser trigger signal can be an analog pulse signal.

[0101] According to embodiments of this disclosure, an off-axis laser receiver mirror can collimate laser signals of different wavelengths without adjusting the position or angle of the receiver mirror, thereby adapting to the testing requirements of lidar at different wavelengths. A second fiber optic attenuator can attenuate the power of the emitted laser signal, preventing excessive power from damaging the photodetector of the laser receiver module. After recognizing the emitted laser signal, the photodetector generates a laser trigger signal, thereby determining the reception time of the emitted laser signal.

[0102] According to embodiments of this disclosure, the modulator may include a wavelength modulator and a polarization controller.

[0103] A wavelength modulator can be used to modulate the wavelength of the second intermediate laser signal to obtain the third intermediate laser signal.

[0104] To obtain laser echo signals of different wavelengths, the wavelength of the second intermediate laser signal needs to be modulated. By modulating the wavelength of the second intermediate laser signal using a wavelength modulator, a third intermediate laser signal with the second wavelength can be obtained.

[0105] The polarization controller can be used to modulate the polarization state of the third intermediate laser signal to obtain the second and third laser echo signals.

[0106] To obtain laser echo signals with different polarization states, the polarization state of the third intermediate laser signal needs to be modulated. By modulating the polarization state of the third intermediate laser signal using a polarization controller, second and third laser echo signals with different polarization states can be obtained.

[0107] According to embodiments of this disclosure, a wavelength modulator is used to modulate the wavelength of a second intermediate laser signal to obtain a laser signal with a wavelength different from that of the first laser echo signal, namely a third intermediate laser signal. A polarization modulator is then used to separate the polarization state of the third intermediate laser signal to obtain second and third laser signals with different polarization states. By using the wavelength modulator and polarization controller, the laser echo simulation device can obtain laser echo signals with multiple wavelengths and multiple polarization states, thereby adapting the laser echo simulation device to the testing requirements of multi-mode lidar.

[0108] According to embodiments of this disclosure, the wavelength modulator may include a frequency multiplier and a beam splitter.

[0109] A frequency multiplier can be used to multiply the frequency of a second intermediate laser signal to obtain a mixed laser echo signal with a first wavelength and a second wavelength.

[0110] A frequency multiplier can multiply the frequency of a laser signal, increasing the frequency of the incident laser signal several times. For example, a laser signal with a wavelength of 1064 nm can be multiplied by a frequency multiplier to obtain a laser signal with a wavelength of 532 nm.

[0111] As one implementation, the frequency multiplier can include a periodically polarized potassium titanium phosphate (PPKTP) crystal. PPKTP crystal is a high-performance ferroelectric dielectric nonlinear crystal that achieves frequency conversion through quasi-phase matching, thereby multiplying the second intermediate laser signal. The frequency multiplication efficiency of PPKTP crystal is approximately 1%. After multiplying the second intermediate laser signal using a PPKTP crystal, a mixed laser echo signal with wavelengths of both the first and second wavelengths will simultaneously exist. Alternatively, the frequency multiplier can also include a waveguide frequency multiplier or a fiber frequency multiplier for multiplying the second laser signal.

[0112] Beam splitters can be used to separate the second wavelength signal from the mixed laser echo signal to obtain the third intermediate laser signal.

[0113] To obtain the third intermediate laser signal at the second wavelength, a beam splitter is needed to separate the mixed laser signal according to different wavelengths. The beam splitter can be a dichroic mirror or a harmonic beam splitter. A dichroic mirror can separate laser signals of different wavelengths by designing the cutoff wavelength of a multilayer dielectric film. For example, with a first wavelength of 1064 nm and a second wavelength of 532 nm, a dichroic mirror reflects the 1064 nm laser signal while simultaneously transmitting the 532 nm third intermediate laser signal, thus obtaining the third intermediate laser signal.

[0114] According to embodiments of this disclosure, a frequency multiplier is used to multiply the second intermediate laser signal to obtain a mixed laser echo signal having a first wavelength and a second wavelength, thereby achieving modulation of the wavelength of the second intermediate laser signal. Due to the frequency multiplication efficiency limitation of the frequency multiplier, a mixed laser signal is obtained after modulation. A beam splitter is used to separate the laser signals of different wavelengths in the mixed laser signal to obtain a third intermediate laser signal with a wavelength of the second wavelength, thereby achieving modulation of the wavelength of the second intermediate laser signal.

[0115] According to embodiments of this disclosure, the polarization controller may include a half-wave plate and a polarizing beam splitter.

[0116] Half-wave plates can be used to adjust the components of different polarization states in the third intermediate laser signal.

[0117] A half-wave plate can rotate the vibration direction of linearly polarized light. Since the third intermediate laser signal is linearly polarized, the components with different polarization states in the third intermediate laser signal can be adjusted by rotating the half-wave plate. For example, the S-polarized and P-polarized components in the third intermediate laser signal can be adjusted using a half-wave plate to make them identical.

[0118] A polarization beam splitter can be used to separate the different polarization states of the third intermediate laser signal to obtain the second and third laser echo signals.

[0119] A polarizing beam splitter (PBS) can be used to separate or combine light rays with different polarization states. In a laser echo simulation device, a polarizing beam splitter can be used to separate the different polarization states of a third intermediate laser signal. When the third intermediate laser signal is incident on the incident mirror of the PBS, the S-polarized laser signal is reflected, thus obtaining the second laser echo signal, while the P-polarized laser signal is transmitted, thus obtaining the third laser echo signal.

[0120] According to embodiments of this disclosure, a half-wave plate is used to adjust the components of different polarization states in the third intermediate laser signal, and a polarization beam splitter is used to separate the laser signals of different polarization states in the third intermediate laser signal, thereby obtaining a second laser echo signal and a third laser echo signal. This enables the laser echo simulation device to output laser echo signals of different polarization states, thereby adapting to the testing requirements of different lidars and improving testing efficiency.

[0121] According to embodiments of this disclosure, the echo output module may include an indicator light module, a multiplexer, an off-axis reflector, and an electrically controlled turntable.

[0122] The indicator light module can be used to generate an indicator laser signal. The indicator laser signal can be a visible light signal.

[0123] In simulating laser echoes, it is necessary to obtain the position of the laser echo signal output by the laser echo simulator. An indicator laser signal is generated by an indicator light module capable of generating visible light. Using the position indicated by the indicator laser signal, the target output position of the laser echo signal from the laser echo simulator can be determined.

[0124] A multiplexer can be used to determine a laser echo signal from an indicator laser signal, a first laser echo signal, a second laser echo signal, or a third laser echo signal.

[0125] A multiplexed optical switch enables arbitrary switching of output channels among multiple output optical signals. In laser echo simulation, an indicator laser signal is first determined as the output laser echo signal, used to indicate the position of the laser echo signal output by the laser echo simulation device. With the position of the laser echo signal output by the laser echo simulation device determined as the target output position, the multiplexed optical switch is used to switch between multiple laser echo signals according to the echo simulation requirements. This allows the laser echo signal to be fed back to the lidar from the first, second, or third laser echo signal. As one implementation, the multiplexed optical switch can include a MEMS-based single-mode fiber optic switch. In a MEMS-based single-mode fiber optic switch, the optical path can be controlled by controlling a micromirror array. For example, the angle of the micromirrors can be controlled by electrostatic or magnetic means to reflect laser echo signals from different channels into the output fiber, thereby completing the selection of the laser echo signal.

[0126] Off-axis mirrors can be used to collimate laser echo signals.

[0127] The off-axis reflector is a parabolic reflector, which can collimate laser echo signals of different wavelengths without adjusting the position or angle of the reflector. This allows for the collimation of the laser echo signal in a laser echo simulation device without switching the collimating reflector. For example, the parabolic reflector can be a 90° parabolic reflector with an off-axis angle of 90°. This allows the propagation direction of the laser echo signal output from the multi-channel optical switch to change by 90° after passing through the parabolic reflector, meaning the incident and exit angles of the laser echo signal are perpendicular.

[0128] An electronically controlled turntable can be used to control the angle of the laser echo signal.

[0129] The electrically controlled turntable allows for precise small-angle adjustments, thereby controlling the output angle of the laser echo signal. In a laser echo simulation device, an off-axis mirror can be deployed on the turntable. By adjusting the angle of the turntable, the output angle of the off-axis mirror can be controlled, thus adjusting the output angle of the laser echo signal. Furthermore, the mirror surface of the off-axis mirror can also be controlled via the turntable, thereby controlling the output angle of the laser echo signal.

[0130] According to embodiments of this disclosure, the echo output module is equipped with an indicator light module capable of generating visible light band laser signals, which can be used to indicate the output position of the laser echo signal output by the echo output module. A multiplexer can determine which laser signals to output. An off-axis reflector can collimate laser echo signals of different wavelengths without adjusting the reflector's position or angle, adapting to different wavelengths of laser echo signals output by the system. An electrically controlled turntable can control the output angle of the laser echo signal, facilitating adjustment of the laser signal's output position and ensuring accurate output of the laser echo signal.

[0131] The following will combine Figures 4 to 8 The laser echo simulation apparatus according to embodiments of this disclosure will be described.

[0132] Figure 4 A schematic diagram of a laser receiving module according to an embodiment of the present disclosure is shown.

[0133] like Figure 4 As shown, the laser receiving module may include an off-axis laser receiving mirror, a second fiber attenuator, a diffuse scattering sheet, and a photodetector. The laser receiving module can be used to receive the emitted laser signal from the lidar and generate a laser trigger signal based on the reception time of the emitted laser signal.

[0134] In one implementation, the emitted laser signal from the lidar is received and collimated by an off-axis laser receiver mirror, and its power is adjusted by a second fiber optic attenuator. For example, using an aperture attenuator, the power of the emitted laser signal is adjusted manually by changing the aperture diameter of the attenuator, ensuring the power meets the detection requirements of the photodetector without damaging the laser receiver module. The power-adjusted emitted laser signal then enters a diffuser, which homogenizes the signal for accurate detection by the photodetector. The emitted laser signal can be transmitted to the photodetector using a multimode fiber with an SMA905 interface. The length of the multimode fiber needs precise calibration; for example, a 3m multimode fiber with a numerical aperture (NA) of 0.22.

[0135] A photodetector can generate a laser trigger signal based on the reception time of the emitted laser signal. As one implementation, the photodetector can be a silicon photoelectric free-space detector, capable of detecting emitted laser signals in the wavelength range of 350 nm to 1100 nm, meeting the testing requirements of lidar across a wide wavelength range. The silicon photoelectric free-space detector incorporates a low-noise transimpedance amplifier, achieving a 2 GHz bandwidth and 100 mW saturation power, enabling the laser receiving module to isolate stray light and adapt to the testing needs of various lidar systems.

[0136] Figure 5 A schematic diagram of a laser echo simulation apparatus according to an embodiment of the present disclosure is shown.

[0137] like Figure 5 As shown, the pulse generation module of the laser echo simulation device may include a controller and a digital-to-analog converter.

[0138] The controller may include an FPGA. The FPGA can receive and store echo waveform data generated by the lidar illuminating different targets. The FPGA can include a signal trigger detection module to detect the laser trigger signal output by the photodetector and determine its arrival time. Upon detecting the laser trigger signal, the simulation delay duration is determined based on the distance between the lidar and the target, and the generation time of the trigger timing signal is determined based on this simulation delay duration. The FPGA can achieve a simulation delay duration setting of 1 ms to 4 ms in 5 ns increments.

[0139] A digital-to-analog converter (DAC) can be a high-speed digital-to-analog converter. A high-speed DAC can read pre-stored echo waveform data from an FPGA at a sampling rate of 2 Gsps and a resolution of 8 bits, and convert the echo waveform data into analog pulse electrical signals.

[0140] Figure 6 The diagram illustrates how the signal trigger detection module of this disclosure determines the arrival time of the laser trigger signal.

[0141] like Figure 6 As shown, the signal trigger detection module in the FPGA first performs filtering and timing discrimination processing on the laser trigger signal. Filtering removes circuit noise carried in the laser trigger signal. Timing discrimination determines the arrival time of the laser trigger signal. Since the pulse width and amplitude of the laser trigger signal vary significantly, the leading-edge timing method can be used for timing discrimination. The leading-edge timing method sets a predetermined threshold, triggering timing discrimination after the rising edge of the laser trigger signal reaches the predetermined threshold, thus reducing time measurement errors caused by morphological fluctuations in the laser trigger signal.

[0142] Figure 7 The diagram illustrates a pulse generation module generating an analog pulse electrical signal according to an embodiment of the present disclosure.

[0143] like Figure 7 As shown, the FPGA can receive and store echo waveform data via an RS232 serial communication interface. When the FPGA receives a laser trigger signal, it determines the simulation delay duration based on the distance between the lidar and the target, and then determines the generation time of the trigger timing signal based on the simulation delay duration. The digital-to-analog converter responds to the trigger timing signal by reading the echo waveform data from the FPGA and converting it into an analog pulse electrical signal.

[0144] In the pulse generation module, the clock module (i.e., CLK) provides a 400 MHz clock signal to the FPGA to drive the internal logic operations and data transmission of the FPGA, and provides a 2 GHz clock signal to the digital-to-analog converter to drive the digital-to-analog converter to convert the echo waveform data into analog pulse electrical signals.

[0145] refer to Figure 5 The echo modulation module of the laser echo simulation device may include a laser, an interferometer, a beam splitter, and a modulator.

[0146] To achieve high-precision laser echo modulation, the laser can be a single-frequency polarization-maintaining laser, ensuring that the output reference laser signal is a single-frequency laser signal. For example, a single-frequency polarization-maintaining laser with an output reference laser signal wavelength of 1064 nm and a P-polarized state can be used. The reference laser signal output from the single-frequency polarization-maintaining laser is transmitted to the interferometer through a polarization-maintaining fiber. Transmitting the reference laser signal through the polarization-maintaining fiber ensures that the polarization state of the reference laser signal remains unchanged during transmission. Furthermore, active temperature control stabilizes the operating temperature of the single-frequency polarization-maintaining laser, thereby stabilizing the wavelength of the reference laser signal output by the single-frequency polarization-maintaining laser.

[0147] The interferometer can be a Mach-Zehnder interferometer. The reference laser signal is input to the input port of the Mach-Zehnder interferometer through a polarization-maintaining fiber. The reference laser signal is modulated by modulating the arm length of the Mach-Zehnder interferometer by an analog pulse electrical signal to obtain the first intermediate laser signal.

[0148] Because the process of modulating the Mach-Zehnder interferometer with the simulated pulse electrical signal introduces chirp, and the Mach-Zehnder interferometer also generates amplitude-frequency errors under the influence of the simulated pulse electrical signal, the output first intermediate laser signal suffers nonlinear distortion. Therefore, the echo modulation module is also equipped with a compensator to monitor the first intermediate laser signal output by the Mach-Zehnder interferometer. When the first intermediate laser signal exhibits nonlinear distortion, it is input into a pre-constructed nonlinear distortion function to generate a compensation electrical signal. Based on the compensation electrical signal, the simulated pulse electrical signal is pre-distorted to compensate for the distortion, thereby obtaining an approximately linear first intermediate laser signal.

[0149] The first intermediate laser signal is transmitted to the beam splitter via a polarization-maintaining fiber. The beam splitter can split the first intermediate laser signal according to optical power. In one implementation, the beam splitter can split the first intermediate laser signal into 10% and 90% optical power beams. The 10% optical power laser signal serves as the first laser echo signal, and the 90% optical power laser signal serves as the second intermediate laser signal. The beam splitting loss of the beam splitter is 3 dB, and the wavelengths of the first laser echo signal and the second intermediate laser signal are the first wavelength, i.e., 1064 nm.

[0150] The laser echo simulation device will now be described along the transmission direction of the second intermediate laser signal.

[0151] The second intermediate laser signal is transmitted through a polarization-maintaining fiber. At the output port of the polarization-maintaining fiber, the second intermediate laser signal is coupled into the first collimating lens 51 in the form of spatial light. After being collimated by the first collimating lens 51, the second intermediate laser signal is coupled into a frequency multiplier. The frequency multiplier can be a PPKTP crystal, which can multiply the frequency of the second intermediate laser signal. Since the frequency multiplication efficiency of the PPKTP crystal is approximately 1%, after multiplying the second intermediate laser signal, a mixed laser echo signal with wavelengths of the first and second wavelengths will exist simultaneously. The mixed laser echo signal is collimated by the second collimating lens 52 and then passes through a beam splitter. The beam splitter can separate the mixed laser signals of different wavelengths. By splitting the mixed laser echo signal using the beam splitter, a third intermediate laser signal with a wavelength of the second wavelength and a mixed laser signal with a wavelength of the first wavelength can be obtained. The mixed laser signal with a wavelength of the first wavelength is reflected by the beam splitter and absorbed by a blackbody. The wavelength of the third intermediate laser signal is 532 nm. The P-polarization and S-polarization components of the third intermediate laser signal are adjusted by a half-wave plate to make their components equal. The third intermediate laser signal, adjusted by a half-wave plate, is separated by a PBS. When the third intermediate laser signal is incident on the incident mirror of the PBS, the S-polarized laser signal is reflected, thus obtaining the second laser echo signal, while the P-polarized laser signal is transmitted, thus obtaining the third laser echo signal. The second laser echo signal is coupled into the output optical fiber through the first lens 53, and the third laser echo signal is coupled into the output optical fiber through the second lens 54.

[0152] In the echo modulation module, the output power of the laser echo signal is adjusted by the first fiber optic attenuator to meet the preset first power.

[0153] The first fiber optic attenuator may include a first attenuator 55, a second attenuator 56, and a third attenuator 57. The first attenuator 55 adjusts the output power of the first laser echo signal, the second attenuator 56 adjusts the output power of the second laser echo signal, and the third attenuator 57 adjusts the power of the third laser echo signal. The first fiber optic attenuator can be a MEMS-based fiber optic attenuator, capable of achieving a maximum attenuation greater than 30 dB and a polarization extinction ratio greater than 13 dB for laser echo signal output through manual or automatic attenuation adjustment.

[0154] Figure 8 A schematic diagram of an echo output module according to an embodiment of the present disclosure is shown.

[0155] like Figure 8 As shown, the echo output module may include: an indicator light module, a multiplexer, an off-axis reflector, and an electrically controlled turntable.

[0156] The indicator optical module generates an indicator laser signal with a wavelength in the visible light band. The multiplexer can determine the output laser echo signal from the indicator laser signal, the first laser echo signal, the second laser echo signal, or the third laser echo signal. When feeding back a laser echo signal to the lidar under test, the indicator laser signal is first selected as the output optical signal of the multiplexer. Since the indicator laser signal is in the visible light band, the output position of the laser echo signal can be determined by its output position. Once the output position of the laser echo signal is determined, the multiplexer is switched according to the lidar testing requirements to determine the laser echo signal to be fed back to the lidar from the first, second, or third laser echo signal. The first, second, and third laser echo signals are input to the multiplexer via a single-mode polarization-maintaining fiber.

[0157] With the laser echo signal selected by a multiplexer, the laser echo signal is transmitted to an off-axis mirror via a single-mode polarization-maintaining fiber. The off-axis mirror is a parabolic reflector, which can collimate laser echo signals of different wavelengths without adjusting the mirror's position or angle, thus satisfying the output of laser echo signals at both 532 nm and 1064 nm wavelengths. The divergence angle of the output laser echo signal can be less than 10 mrad, and the spot diameter can be less than 20 cm (1 / e).

[0158] To achieve precise control of the laser echo signal output position, the output angle of the off-axis reflector can be controlled via an electrically controlled turntable, thereby adjusting the position of the laser echo signal. Furthermore, the reflective surface of the off-axis reflector can also be controlled via the electrically controlled turntable to precisely adjust the output position of the laser echo signal. The electrically controlled turntable can achieve a rotation adjustment accuracy of 3.5 μrad and an adjustment range greater than 5 degrees.

[0159] According to embodiments of this disclosure, the laser echo simulation device can generate laser echo signals with an extinction ratio greater than 30 dB, and can output laser echo signals with wavelengths of 532 nm or 1064 nm. It can also control S-polarization or P-polarization. Furthermore, the laser echo simulation device can achieve safety protection by adjusting the attenuation of the laser echo signal power by the first fiber attenuator or by shutting down the output channel of the multiplexer, to avoid injury to operators or damage to the equipment under test during testing.

[0160] This disclosure also provides a host computer for laser echo simulation. The host computer can implement software installation, device control, and data storage for dynamic laser echo simulation. For example, the host computer can set the operating wavelength and polarization state of the laser echo simulation device, and select a first laser echo signal of 1064nm, a second laser echo signal with a 532nm-S polarization state, or a third laser echo signal with a 532nm-S polarization state as the output laser echo signal. The host computer can set the control parameters of the first fiber optic attenuator, such as switching between automatic and manual control modes and setting the attenuation amount of the attenuator on the laser echo signal. The host computer can set the output power and pulse width of the laser echo signal; for example, the power of the 1064nm wavelength laser echo signal is adjusted within the range of 10nW to 11µW, and the pulse width is adjusted within the range of 10ns to 100ns. The power of the 532nm wavelength laser echo signal is adjusted within the range of 30nW to 0.1µW, and the pulse width is adjusted within the range of 100ns to 400ns. The laser echo signal power adjustment step size for 1064nm or 532nm wavelengths is 1nW, with a power adjustment accuracy of 0.1% of maximum power. The pulse width adjustment step size is 0.5 ns, and it can achieve an adjustment accuracy of 0.1% of maximum pulse width, making it suitable for testing ultra-high-speed lidar. Furthermore, the interferometer's operating status can be monitored in the host computer, and abnormal prompts can be provided in case of interferometer malfunction. The laser temperature, wavelength, power, and status display of the laser are also monitored.

[0161] Figure 9 A flowchart illustrating a laser echo simulation method according to an embodiment of the present disclosure is shown schematically.

[0162] like Figure 9 As shown, the laser echo simulation method includes operations S910 to S960.

[0163] According to embodiments of this disclosure, it is possible to Figure 9 The laser echo simulation method is applied to the aforementioned laser echo simulation device.

[0164] When operating the S910, the pulse generation module is used to generate analog pulse electrical signals.

[0165] When operating the S920, the laser output reference laser signal is utilized by the laser included in the echo modulation module.

[0166] In operation of S930, the interferometer included in the echo modulation module modulates the reference laser signal under the action of analog pulse electrical signal to generate the first intermediate laser signal.

[0167] In operation S940, the first intermediate laser signal is split into two beams using the beam splitter included in the echo modulation module to obtain a first laser echo signal and a second intermediate laser signal, wherein the wavelength of the first laser echo signal is the first wavelength.

[0168] In operation of S950, the wavelength and polarization state of the second intermediate laser signal are modulated by the modulator included in the echo modulation module to obtain the second laser echo signal and the third laser echo signal.

[0169] Among them, the wavelengths of the second laser echo signal and the third laser echo signal are the second wavelengths, and the polarization states of the second laser echo signal and the third laser echo signal are different.

[0170] When operating the S960, the laser echo signal is output using the echo output module.

[0171] The laser echo signal includes a first laser echo signal, a second laser echo signal, or a third laser echo signal.

[0172] It should be noted that the laser echo simulation method section in the embodiments of this disclosure corresponds to the laser echo simulation device section in the embodiments of this disclosure. For a detailed description of the laser echo simulation method section, please refer to the laser echo simulation device section, which will not be repeated here.

[0173] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, may be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions. Those skilled in the art will understand that the features recited in the various embodiments and / or claims of this disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not expressly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure may be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0174] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A laser echo simulation device, comprising: The pulse generation module is used to generate analog pulse electrical signals; The echo modulation module includes: A laser used to output a reference laser signal; An interferometer is used to modulate the reference laser signal under the action of the analog pulse electrical signal to generate a first intermediate laser signal; A beam splitter is used to split the first intermediate laser signal into two beams to obtain a first laser echo signal and a second intermediate laser signal, wherein the wavelength of the first laser echo signal is a first wavelength. A modulator is used to modulate the wavelength and polarization state of the second intermediate laser signal to obtain a second laser echo signal and a third laser echo signal, wherein the wavelengths of the second laser echo signal and the third laser echo signal are both the second wavelength, and the polarization states of the second laser echo signal and the third laser echo signal are different; and An echo output module is used to output a laser echo signal fed back to the lidar under test. The laser echo signal includes a first laser echo signal, a second laser echo signal, or a third laser echo signal. The laser echo signal is used to test the performance of the lidar under test.

2. The apparatus according to claim 1, wherein, The modulator includes: A wavelength modulator is used to modulate the wavelength of the second intermediate laser signal to obtain a third intermediate laser signal; and A polarization controller is used to modulate the polarization state of the third intermediate laser signal to obtain the second laser echo signal and the third laser echo signal.

3. The apparatus according to claim 2, wherein, The wavelength modulator includes: A frequency multiplier is used to multiply the frequency of the second intermediate laser signal to obtain a mixed laser echo signal having the first wavelength and the second wavelength; and A beam splitter is used to separate the second wavelength signal from the mixed laser echo signal to obtain the third intermediate laser signal.

4. The apparatus according to claim 2 or 3, wherein, The polarization controller includes: A half-wave plate, used to adjust the components of the third intermediate laser signal with different polarization states; and A polarizing beam splitter is used to separate the different polarization states of the third intermediate laser signal to obtain the second laser echo signal and the third laser echo signal.

5. The apparatus according to any one of claims 1 to 3, wherein, The echo modulation module also includes: The compensator is used to respond to the nonlinear distortion generated by the first intermediate laser signal by inputting the first intermediate laser signal into a nonlinear distortion function to generate a compensation electrical signal, and to perform pre-distortion compensation on the analog pulse electrical signal according to the compensation electrical signal.

6. The apparatus according to any one of claims 1 to 3, wherein, The echo modulation module also includes: A power monitoring module is configured to monitor the power of at least one of the first laser echo signal, the second laser echo signal, or the third laser echo signal, and, in response to the power not being a first preset power, send an adjustment signal to the first fiber optic attenuator; and The first fiber optic attenuator is configured to adjust the power of at least one of the first laser echo signal, the second laser echo signal, or the third laser echo signal to the first preset power in response to the adjustment signal.

7. The apparatus according to any one of claims 1 to 3, wherein, The pulse generation module includes: A controller is configured to delay the arrival time of the laser indicated by the received laser trigger signal by a simulated duration to obtain a trigger timing signal, wherein the simulated duration is determined based on the simulated distance between the lidar and the target object; and A digital-to-analog converter is configured to read pre-stored echo waveform data from the controller in response to the trigger timing signal and convert the echo waveform data into the analog pulse electrical signal, wherein the echo waveform data is determined based on at least one of an atmospheric transmission model or physical parameters of the target object.

8. The apparatus according to claim 7, wherein, Also includes: A laser receiving module is used to receive the emitted laser signal from the lidar and generate the laser trigger signal based on the emitted laser signal.

9. The apparatus according to claim 8, wherein, The laser receiving module includes: An off-axis laser receiver is used to quasi-directly receive the emitted laser signal emitted by the lidar. A second fiber optic attenuator is used to adjust the power of the emitted laser signal to a second preset power; and A photodetector is used to generate the laser trigger signal based on the receiving time of the emitted laser signal.

10. The apparatus according to any one of claims 1 to 3, wherein, Also includes: A control module is used to control the temperature of the echo modulation module within a predetermined temperature range.

11. The apparatus according to any one of claims 1 to 3, wherein, The echo output module includes: An indicator light module is used to generate an indicator laser signal, wherein the indicator laser signal is visible light; A multiplexed optical switch is used to determine the laser echo signal from the indicator laser signal, the first laser echo signal, the second laser echo signal, or the third laser echo signal; An off-axis mirror is used to collimate the laser echo signal; and An electrically controlled turntable is used to control the angle of the laser echo signal.

12. A laser echo simulation method, comprising: The pulse generation module is used to generate analog pulse electrical signals; The laser output reference laser signal is utilized by the laser included in the echo modulation module; The interferometer included in the echo modulation module modulates the reference laser signal under the action of the analog pulse electrical signal to generate a first intermediate laser signal; The first intermediate laser signal is split into two beams using the beam splitter included in the echo modulation module to obtain a first laser echo signal and a second intermediate laser signal, wherein the wavelength of the first laser echo signal is a first wavelength. The wavelength and polarization state of the second intermediate laser signal are modulated using the modulator included in the echo modulation module to obtain a second laser echo signal and a third laser echo signal, wherein the wavelength of the second laser echo signal and the third laser echo signal is the second wavelength, and the polarization states of the second laser echo signal and the third laser echo signal are different; and The laser echo signal is output using an echo output module, wherein the laser echo signal includes the first laser echo signal, the second laser echo signal, or the third laser echo signal.

Images