Coherent Wind Measuring Lidar Calibration System and Method

Abstract

The present invention discloses a calibration system and method for a coherent wind-measuring lidar. The calibration system includes: a setting module for setting the wind speed and the atmospheric scenario; a modulation control module for calculating a frequency shift control signal according to the set wind speed and converting the set atmospheric scenario into an intensity control signal; a modulation and amplification module for performing frequency modulation and amplitude modulation on the seed laser input to the radar system to be measured under the drive of a drive module and performing optical power amplification to obtain an analog echo signal; a coupler for coupling the analog echo signal into the radar system to be measured for inversion according to the data of the analog echo signal, and completing calibration by comparing the data after inversion with the data of the analog echo signal. The present invention can calibrate the main optoelectronic parameters and indexes of the coherent wind-measuring lidar under laboratory or on-site environmental conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic instruments, and particularly to a calibration system and method for a coherent wind-measuring lidar. Background Art

[0002] The atmosphere provides a very important guarantee for the survival and development of mankind. The movement of atmospheric wind speed is closely related to human life. Accurate observation of atmospheric wind speed is of great significance for detecting air pollution, military environmental forecasting, improving the safety of aerospace, improving the accuracy of long-term weather forecasting, improving climate research models, etc. Observation of regional wind speed can not only provide guarantee for the safe takeoff and landing of aircraft, but also serve for arranging reasonable aircraft takeoff and landing density at airports. At the same time, it is also becoming increasingly important for high-tech wars. On the artillery battlefield, the wind speed at the positions of guns, projectiles and arrows has an important impact on shooting accuracy. On aircraft carriers and other ships, the safe takeoff and landing of aircraft groups depend on the accurate measurement of the surrounding atmospheric wind speed. In terms of satellite and missile launches, real-time wind speed data is not only a prerequisite for safety guarantee, but also an important factor for improving the launch success rate and missile hit rate. In the utilization of wind energy resources, accurate wind speed measurement can also improve the efficiency of wind power generation. Therefore, the measurement of atmospheric wind speed has received more and more attention, and organizations such as the International Civil Aviation Organization, the World Meteorological Organization, and aerospace research institutions in various countries around the world are actively carrying out research and development of wind speed detection systems.

[0003] As an active atmospheric remote sensing instrument newly developed in recent years, the wind-measuring lidar has the advantages of small volume, high wind speed measurement accuracy, high time and space resolution, etc. The wind-measuring lidar mainly measures the wind speed of the atmosphere by using the principle of Doppler frequency shift, and can be divided into coherent detection (also known as heterodyne detection) and non-coherent detection (also known as direct detection) according to different detection principles.

[0004] Coherent detection realizes the measurement of atmospheric wind speed through the coherence (beat frequency) of the atmospheric echo signal of the emitted laser and the local oscillator laser. The measurement accuracy of the wind-measuring lidar is a crucial index, which mainly includes the accuracy of the wind speed magnitude and the accuracy of the direction. The common coherent wind-measuring lidar is composed of an optical fiber optical path. Due to the differences in the line width, pulse shape, energy magnitude and repetition frequency of the coherent wind-measuring lidar laser, as well as the specific properties of the optical fiber devices and the end face reflection conditions, these factors may cause differences in the accuracy of the wind-measuring lidar. In addition, the selection of the balanced detector and the signal processing differences of the subsequent electronic system are also important reasons for the accuracy differences of the coherent wind-measuring lidar.

[0005] The calibration of a wind measurement lidar generally involves comparing the data from a wind cup and an anemometer with the data in a meteorological wind tower. The calibration is generally carried out under field conditions. Moreover, the atmospheric wind speed in the field is uncontrollable, making it difficult to calibrate the wind speed at different wind force levels within a certain period of time. The windy time is also uncertain, which will affect the calibration. At the same time, the aerosol environment for the radar operation is different in different regions. The existing calibration methods are difficult to meet the requirement of calibrating the wind speed measurement results under different aerosol environments at the same location within a certain period of time, and it is difficult to meet the needs of autonomous, regular, and on-site calibration.

[0006] Therefore, it is necessary to invent a hardware calibration system for coherent wind measurement lidar to calibrate the main optoelectronic parameters and algorithms of the coherent wind measurement lidar under laboratory or field environmental conditions. Summary of the Invention

[0007] The main purpose of the present invention is to provide a calibration system and method for coherent wind measurement lidar that can calibrate the main optoelectronic parameters and algorithms of the coherent wind measurement lidar under laboratory or field environmental conditions.

[0008] The technical solution adopted by the present invention is as follows:

[0009] Provide a calibration system for coherent wind measurement lidar, including a setting module, a modulation control module, a driving module, a modulation amplification module, and a coupler, wherein:

[0010] The setting module is used to set the wind speed and atmospheric scenario;

[0011] The modulation control module is connected to the input module and is used to calculate the Doppler frequency shift corresponding to different time points according to the set wind speed and convert it into a frequency shift control signal; this modulation control module is also used to convert the set atmospheric scenario into an intensity control signal;

[0012] The modulation amplification module is used to perform frequency modulation and amplitude modulation on the seed laser input to the radar system to be measured according to the frequency shift control signal and intensity control signal generated by the modulation control module under the drive of the driving module, and perform optical power amplification to obtain an analog echo signal;

[0013] The coupler is used to couple the analog echo signal into the radar system to be measured, and generate a beat signal with the seed laser of the radar system to be measured, so that the radar system to be measured can obtain the data of the analog echo signal for inversion according to this beat signal, and complete the calibration by comparing the inverted data with the data of the analog echo signal.

[0014] According to the above technical solution, the modulation amplification module is time-synchronized with the coherent wind measurement lidar system to be measured, and the synchronization signal is provided by the coherent wind measurement lidar system to be measured.

[0015] Continuing with the above technical solution, the modulation and amplification module specifically matches different PRFs of the radar system under test through a synchronization signal.

[0016] Continuing with the above technical solution, the coupler is also used to control the divergence angle of the analog echo signal through flat-top divergence to be much larger than the receiving field of view angle of the lidar to be measured.

[0017] Continuing with the above technical solution, the modulation and amplification module performs intermediate frequency modulation on the seed laser, and the range is 80 MHz - 200 MHz.

[0018] Continuing with the above technical solution, the setting module is specifically used to freely set the wind speed information and atmospheric scene through user input, or set by selecting different preset levels of wind speed and atmospheric scene.

[0019] Continuing with the above technical solution, the different preset levels of wind speed include gale frequency, strong wind frequency, and gentle breeze frequency.

[0020] Continuing with the above technical solution, the different preset atmospheric scenes include heavy pollution, moderate pollution, and light pollution, and different atmospheric scenes correspond to different absorption and scattering of light by aerosol particles.

[0021] The present invention also provides a calibration method for a coherent wind lidar, including the following steps:

[0022] Set the wind speed and atmospheric scene;

[0023] Calculate the Doppler frequency shift corresponding to different time points according to the set wind speed and convert it into a frequency shift control signal; convert the set atmospheric scene into an intensity control signal;

[0024] Perform frequency modulation and amplitude modulation on the seed laser input to the radar system under test according to the frequency shift control signal and intensity control signal, and perform optical power amplification to obtain an analog echo signal;

[0025] Couple the analog echo signal into the radar system under test, and generate a beat frequency signal with the seed laser of the radar system under test, so that the radar system under test can obtain the data of the analog echo signal according to the beat frequency signal for inversion;

[0026] Compare the data after inversion with the data of the analog echo signal to complete calibration.

[0027] Continuing with the above technical solution, when performing frequency modulation and amplitude modulation, a synchronization signal is provided by the coherent wind lidar system under test to achieve time synchronization.

[0028] The beneficial effects produced by the present invention are as follows: The system of the present invention can obtain the frequency shift control signals corresponding to different time points according to the set wind speed, and obtain the intensity control signal according to the set atmospheric scenario. Based on these two control signals, the seed laser input to the radar system to be measured can be frequency modulated and amplitude modulated, so as to obtain an analog echo signal. The radar system to be measured performs inversion based on the data of the analog echo signal and then compares it with the data of the analog echo signal. If it meets the preset conditions, it indicates that the radar system to be measured meets the calibration standard; otherwise, it does not meet the standard, thus completing the calibration. In addition, the parameters of the radar system to be measured can be adjusted according to the comparison results to make it meet the calibration conditions. The present invention creatively realizes the analog echo signals of various different wind speeds and atmospheric scenarios, so as to adapt to the calibration requirements of various different radar systems to be measured.

[0029] Furthermore, the modulation and amplification module is time synchronized with the coherent wind lidar system to be measured, and the synchronization signal is provided by the coherent wind lidar system to be measured, that is, the time when the radar emits a pulsed light beam is the same as the time of the synchronization signal. Through time synchronization, the flight time of the light beam can be calculated. The time difference between the received echo time and the transmitted pulse time is the flight time of the light beam. By accurately measuring this time interval of the flight time of the light beam and combining the propagation speed of the laser in the atmosphere, the distance between the atmospheric scenario (corresponding to different target aerosols) and the coherent wind lidar can be accurately calculated.

[0030] Furthermore, by using the pulse synchronization signal of the coherent wind lidar to be calibrated to synchronize the optical pulse, the calibration of lidar systems with different repetition frequencies can be realized.

[0031] Furthermore, the optical signal after modulation and amplification in the present invention is flat-top divergent, and its divergence angle is much larger than the receiving field of view angle of the laser radar to be measured. Therefore, its coupling efficiency is only related to the coupling distance and is not sensitive to the misalignment angle between the optical axes of the two.

[0032] Furthermore, by performing intermediate frequency modulation on the seed laser, it can adapt to coherent wind lidar systems with different intermediate frequencies.

[0033] Furthermore, due to the complexity of the concentration, composition and distribution of aerosols, the present invention freely sets the wind speed information and atmospheric scenario through user input, or sets it by selecting different preset levels of wind speed and atmospheric scenario, so as to more conveniently simulate atmospheric scenarios with different levels of wind speed and aerosols with different concentrations and distributions.

[0034] Of course, it is not necessary for any product implementing the present invention to simultaneously achieve all the above-mentioned advantages. Description of the Drawings

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0036] Figure 1A It is a schematic structural diagram of a calibration system for a coherent wind-measuring lidar according to an embodiment of the present invention;

[0037] Figure 1B It is a schematic structural diagram of a calibration system for a coherent wind-measuring lidar according to another embodiment of the present invention;

[0038] Figure 2 It is a schematic diagram of signal input of a calibration system for a coherent wind-measuring lidar according to an embodiment of the present invention;

[0039] Figure 3 It is a schematic diagram of the working process of a calibration system for a coherent wind-measuring lidar according to an embodiment of the present invention. Detailed implementation manners

[0040] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further details the present invention in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] It should be noted that the diagrams provided in the embodiments of the present invention only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape and size of the components in actual implementation. The types, quantities and proportions of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0042] In the present invention, it should also be noted that when terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application. In addition, when terms such as "first" and "second" appear, they are only used for descriptive and distinguishing purposes and cannot be understood as indicating or implying relative importance.

[0043] The wind measurement lidar is an important tool for detecting and measuring the atmospheric wind speed, aerosol distribution, and atmospheric dynamic changes. In practical applications, the intensity of the backscattered light is affected by various factors, resulting in large variations. These factors include the inverse square law of distance, exponential attenuation, and uneven aerosol distribution.

[0044] For a single laser pulse, at the emission wavelength λ (nm) of the transmitter, the power P(λ, X) of the atmospheric backscattered echo signal received from a distance X (m) can be expressed as:

[0045]

[0046] Among them, T L is the total transmittance of the emission system, E0 (J) is the energy of a single laser pulse, c (m / s -1 ) is the speed of light, A R (m 2 ) is the effective area of the receiving telescope, β(λ, X) (m -1 sr -1 ) is the total backscattering coefficient, and α(λ, X) (m -1 ) is the total extinction coefficient.

[0047] First, according to the lidar equation, the intensity of the backscattered light is inversely proportional to the square of the target distance. The farther the distance, the weaker the intensity of the backscattered light. Second, during the propagation of the laser, due to the absorption and scattering of gases and aerosol particles in the atmosphere, the light intensity decays exponentially. The distribution of aerosols is usually uneven, resulting in uneven scattering and absorption when the laser propagates in the atmosphere, further affecting the intensity and stability of the echo signal. In addition, different types of aerosols and gases have different reflection and scattering characteristics for the laser, and these differences will affect the intensity of the backscattered light.

[0048] The present invention aims to provide a coherent wind measurement lidar calibration system and method with simple operation and high accuracy in simulating echo signals.

[0049] As Figure 1A shown, the coherent wind measurement lidar calibration system in the embodiment of the present invention includes a setting module, a modulation control module, a driving module, a modulation amplification module, and a coupler, where:

[0050] The setting module is used to set the wind speed and atmospheric scenario;

[0051] The modulation control module is connected to the input module and is used to calculate the Doppler frequency shift corresponding to different time points according to the set wind speed and convert it into a frequency shift control signal; the modulation control module is also used to convert the set atmospheric scenario into an intensity control signal;

[0052] The modulation and amplification module is used to perform frequency modulation and amplitude modulation on the seed laser input by the radar system to be measured according to the frequency shift control signal and intensity control signal generated by the modulation control module under the drive of the drive module, and perform optical power amplification to obtain an analog echo signal. It can be seen that the amplitude modulation of this system is used to simulate the scattering and extinction of laser by atmospheric components (such as aerosols and molecules), and the frequency modulation is used to simulate the radial wind speed.

[0053] The coupler is used to couple the analog echo signal into the radar system to be measured, and generate a beat signal with the seed laser of the radar system to be measured, so that the radar system to be measured can obtain the data of the analog echo signal according to the beat signal for inversion, and complete the calibration by comparing the inverted data with the data of the analog echo signal.

[0054] This system uses the seed light of the coherent wind lidar to be calibrated for modulation, so as to ensure that beat frequency (in-phase) can be performed, generate a beat signal, and perform measurement through coherent light.

[0055] Specifically, in a preferred embodiment of the present invention, the modulation and amplification module is time-synchronized with the coherent wind lidar system to be measured, and the synchronization signal is provided by the coherent wind lidar system to be measured. That is, the time when the radar emits a pulsed light beam is the same as the time of the synchronization signal. Through time synchronization, the flight time of the light beam can be calculated. The time difference between the received echo time and the transmitted pulse time is the flight time of the light beam. By accurately measuring this time interval of the flight time of the light beam and combining the propagation speed of the laser in the atmosphere, the distance between the atmospheric scene (corresponding to different target aerosols) and the coherent wind lidar can be accurately calculated.

[0056] Furthermore, the modulation and amplification module specifically matches the radar systems to be measured with different repetition frequencies through the synchronization signal. By synchronizing the optical pulse with the pulse synchronization signal of the coherent wind lidar to be calibrated, the lidar systems with different repetition frequencies can be calibrated.

[0057] Furthermore, the coupler is also used to control the divergence angle of the analog echo signal with flat-top divergence to be much larger than the receiving field angle of the lidar to be measured. By setting the divergence angle of the flat-top divergence to be one order of magnitude larger than the receiving field angle of the lidar to be measured, its coupling efficiency is only related to the coupling distance and is not sensitive to the misalignment angle between the optical axes of the two.

[0058] Furthermore, the modulation and amplification module performs intermediate frequency modulation on the seed laser, and its range is 80 MHz - 200 MHz. This modulation and amplification module can perform frequency modulation without amplitude attenuation of 80 MHz - 200 MHz on the light input by the seed laser (the laser of the radar system to be measured in the present invention) to adapt to the coherent wind lidar systems to be measured with different intermediate frequencies.

[0059] Further, the setting module is specifically configured to freely set the wind speed information and atmospheric scenarios through user input, or to set them by selecting different preset levels of wind speed and atmospheric scenarios. The preset different levels of wind speed include gale frequency, strong wind frequency, and gentle breeze frequency. The preset different atmospheric scenarios include heavy pollution, moderate pollution, and light pollution, and different atmospheric scenarios correspond to different absorption and scattering of light by aerosol particles. As Figure 2 shown, the specific frequencies of various different wind speeds and the aerosol scenarios under various different pollution levels are given.

[0060] As Figure 1B , Figure 2 shown, in another embodiment of the present invention, the coherent wind lidar calibration system A1 includes a user interface input module A2, a driving module A3, a modulation control module A4, a modulation and amplification module A5, and a coupler A7. Among them, the user interface input module A2 is used to set the wind speed information and aerosol background, and to input the wind speed. The user can freely set the wind speed information on the user interface, and can also select the preset wind speed in the system for setting, such as the wind speed of different wind force levels (as Figure 2 shown in the upper left). The user can freely set the aerosol background on the user interface, and there are multiple preset aerosol backgrounds in the system: heavy pollution, moderate pollution, and light pollution (as Figure 2 shown in the upper right), which is convenient for simulating the radar echo under different aerosol backgrounds and calibrating the radar to be measured more comprehensively. The input form of the user interface input module can be multiple, all of which are used to simulate and set different meteorological environmental conditions such as atmospheric wind speed and aerosol.

[0061] The driving module A3 of this embodiment is responsible for generating and providing the electrical drive and control signals required for the fiber laser amplifier and the acousto-optic modulator. At the same time, the frequency drift of this module is less than 10 kHz high, and it can simulate a radial wind speed (wind speed) of 0.01 m / s; the switching speed of this driving module can reach the order of dozens of nanoseconds, meeting the requirements of the wind lidar for a 10 m spatial resolution. Through the effective management of this driving module, the user can drive the acousto-optic modulator to perform frequency modulation or amplitude modulation or simultaneous time-frequency modulation, so as to coordinately realize the coherent wind lidar atmospheric echo signal for simulating the set scene wind speed. The driving module A3 may include a wind speed mapping module, the power supplies for driving each device, and the circuits for controlling the seed laser, the modulation and amplification module, and the beam switch. Among them, the wind speed mapping module calculates the corresponding Doppler frequency shift through the set wind speed information (as Figure 2 shown in the upper left), converts this frequency shift into a frequency shifter control signal, and is used to drive the frequency shifter for accurate frequency shifting (as Figure 2 shown in the lower left), and converts the aerosol background information into an intensity control signal for the analog echo signal, and is used to drive the amplitude modulation module to control the signal intensity of the analog echo optical signal (as Figure 2as shown in the lower right); the driving of the amplification module can also be configured with the amplified signal power.

[0062] The seed light A6 is output by the continuous-wave narrow-linewidth seed laser A9 of the measured coherent wind lidar system A13 and is divided into two parts. One part is connected to the balanced detector of the measured system, and the other part is connected to the calibration system for modulation. A coherent lidar measures the Doppler shift through coherent detection, which means continuously scanning the interference fringes of two beams of light with strong coherence and small frequency difference, obtaining the change of the optical signal in the interference field and converting it into an electrical signal, that is, beat frequency + optoelectronic conversion. And a condition for beat frequency is that the echo and the local oscillator light of the radar have the same phase. Using the seed laser of the measured radar system can enable the analog echo after modulation by the calibration system and the local oscillator light of the radar to perform beat frequency with the same phase.

[0063] The modulation and amplification module of this embodiment includes a modulation module and an amplification module, which are mainly responsible for modulating and amplifying the seed light in the measured wind lidar system. During this process, according to the preset meteorological environmental conditions such as aerosol and wind speed, the seed light is modulated accordingly to simulate the corresponding wind speed and aerosol environment. Among them, the modulation module can achieve amplitude modulation with a high suppression ratio, so as to quantitatively simulate the real coherent wind lidar echo signal, thereby meeting the quantitative calibration of the detection distance of the coherent wind lidar. At the same time, the signal is amplified by the amplification module to ensure that the intensity of the simulated lidar echo signal meets the requirements for coupling into the coherent wind lidar system, so as to achieve the accurate calibration of parameters such as the detection distance and wind measurement accuracy of the coherent wind lidar.

[0064] The modulation module can further include a frequency modulation module and an amplitude modulation module. Among them, the frequency modulation module can perform frequency modulation on the light input by the seed laser without amplitude attenuation in the range of 80 MHz - 200 MHz to adapt to different intermediate frequency coherent wind lidar systems under test. The amplitude modulation module can perform amplitude modulation by simulating the atmospheric scenarios set by the user. The amplification module amplifies the modulated optical signal with configurable output power and then connects it to coupler A7. The frequency modulation module A5 converts the digital control signal of the control module A4 into a corresponding electrical signal for frequency modulation. The amplitude modulation module converts the digital control signal of the drive module A3 into a corresponding electrical signal for amplitude modulation. Among them, during the modulation and amplification processes, time synchronization with the coherent wind lidar system under test is required. The synchronization signal A12 is provided by the system under test and can match lidar systems with different repetition frequencies such as 1 kHz, 5 kHz, 10 kHz, 20 kHz, 30 kHz, etc. Time synchronization is mainly used for calculating the time of flight of the light beam. The time of the radar transmitting the pulsed light beam is the same as the time of the synchronization signal. The time of receiving the echo minus the time of the transmitting pulse is the time of flight of the light beam. From this, the distance between the aerosol generating the echo and the telescope can be calculated. The time of flight (TOF) of the lidar refers to the time interval experienced by the pulsed signal after the laser emits a pulsed laser, propagates to the target aerosol, and then the detector receives the aerosol echo signal. By accurately measuring this time interval and combining the propagation speed of the laser in the atmosphere, the distance between the target aerosol and the coherent wind lidar can be accurately calculated.

[0065] In practical applications, due to the complexity of the concentration, composition, and distribution of aerosols, this lidar system is designed with a controllable aerosol simulation module that can simulate aerosol scenarios with various concentrations and distributions. This module can generate aerosol echo signals for different range gates by adjusting the laser reflection intensity and propagation characteristics.

[0066] The divergence angle of the coupler module A7 can be set to be much larger than the field of view angle of the coherent wind lidar system under test, which is easy to couple and use, and can ensure the quantitative input of the coupled optical signal into the system under test.

[0067] As Figure 3 shown, the light output by the seed laser of the coherent wind lidar system under test enters the frequency modulation module for frequency modulation, then enters the amplitude modulation module for amplitude modulation, then enters the amplifier for amplification with controllable output power, and finally is coupled and output by the coupler and enters the telescope of the system under test. The synchronization signal required for the process is given by the radar under test.

[0068] After the wind speed is set, the corresponding Doppler frequency shift is calculated by the following formula and the Doppler frequency shift amount is converted into the frequency shift amount according to the intermediate frequency of the frequency shifter used.

[0069] fd = 2V Los /

[0070] where V Los is the set radial wind speed of the radar telescope under test, f d is the calculated Doppler frequency shift, and λ is the wavelength of light.

[0071] Use the calculated frequency shift amount ( Figure 2 left data upload) to control the frequency modulation module to modulate the light generated by the seed laser, and use the echo signal intensity corresponding to the aerosol background ( Figure 2 right data upload) to control the amplitude modulation module for amplitude modulation. After modulation, the signal enters the amplifier for power-adjustable amplification, and finally a coupler is used to couple the analog echo optical signal with the telescope of the laser radar under test and input it into the telescope A11 of the laser radar under test. Comparing the standard data of the preset wind speed with the wind speed data calculated by the laser radar under test can obtain the accuracy of the wind speed measurement and wind speed inversion of the laser radar under test.

[0072] Example: The intermediate frequency of the laser radar under test is 80 MHz, the available number of points of the frequency shifter is 128 points, and the set wind speed information ( Figure 2 -B1) is converted into the control signal of the frequency shifter ( Figure 2 -B3). The set aerosol background ( Figure 2 -B2) is converted into the amplitude information of the analog echo signal, and further converted into the control signal of the frequency shifter ( Figure 2 -B4). Among them, for frequency modulation to achieve frequency modulation without amplitude attenuation, a frequency shifter with a small amplitude attenuation and an intermediate frequency of 200 MHz is selected for modulation, and then a frequency shift of -120 MHz is performed to match the intermediate frequency of 80 MHz of the system under test.

[0073] During actual use, only need to couple the coupler of the calibration system with the telescope of the system under test, connect the seed light generated by the laser of the system under test to the calibration system, and use the synchronization signal A12 generated by the system under test as the trigger A8 to input it into the calibration system. Such as Figure 3Shown is a coherent wind lidar with a wavelength of 1550 nm, a repetition frequency of 10 kHz for laser pulses, and a single-pulse energy of 110 μJ. During the test, the seed light of the lidar under test is divided into two parts. One part is connected to the balanced detector A10 of the lidar under test for beat frequency, and the extracted part is connected to the modulation and amplification module A5 of the calibration system for frequency modulation and amplitude modulation. The modulation process is controlled by the drive module A3 according to the preset information. After modulation, amplification with adjustable output power is performed, and finally, it is connected to a coupler and coupled into the telescope of the lidar under test. The synchronization signal trigger required for the modulation process is given by the synchronization signal of the lidar under test. The lidar under test performs inversion on the received signal, and the user can calibrate the lidar under test by comparing the data inverted by the lidar under test with the standard data given by the calibration system.

[0074] The present invention also provides a method for calibrating a coherent wind lidar, comprising the following steps:

[0075] S1. Set the wind speed and atmospheric scenario;

[0076] S2. Calculate the Doppler frequency shift corresponding to different time points according to the set wind speed and convert it into a frequency shift control signal; convert the set atmospheric scenario into an intensity control signal;

[0077] S3. Perform frequency modulation and amplitude modulation on the seed laser input to the lidar system under test according to the frequency shift control signal and the intensity control signal, and perform optical power amplification to obtain an analog echo signal;

[0078] S4. Couple the analog echo signal into the lidar system under test and generate a beat frequency signal with the seed laser of the lidar system under test, so that the lidar system under test can obtain the data of the analog echo signal according to the beat frequency signal for inversion;

[0079] S5. Compare the data after inversion with the data of the analog echo signal to complete the calibration.

[0080] Further, when performing frequency modulation and amplitude modulation, a synchronization signal is provided by the coherent wind lidar system under test to achieve time synchronization.

[0081] This method is mainly based on the above calibration system and is used to calibrate the main optoelectronic parameters and indicators of the coherent wind lidar to be tested under laboratory or field environmental conditions. Through the system and method embodiments of the present invention, indicators such as the wind speed measurement accuracy and detection range of the coherent wind lidar to be tested can be obtained quantitatively.

[0082] The present application also provides a computer-readable storage medium, such as a flash memory, a hard disk, a multimedia card, a card-type memory (e.g., SD or DX memory, etc.), a random access memory (RAM), a static random access memory (SRAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a programmable read-only memory (PROM), a magnetic memory, a magnetic disk, an optical disk, a server, an App application store, etc., on which a computer program is stored, and when the program is executed by a processor, corresponding functions are implemented. When the computer-readable storage medium of this embodiment is executed by a processor, the coherent wind lidar calibration method of the method embodiment is implemented.

[0083] It should be noted that, according to the needs of implementation, the various steps / components described in the present application can be split into more steps / components, or two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0084] In the above embodiments, the magnitudes of the sequence numbers of the steps do not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0085] It should be understood that those of ordinary skill in the art can make improvements or transformations according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A coherent wind laser radar calibration system, characterized in that: It includes a setting module, a modulation control module, a driving module, a modulation amplification module and a coupler, wherein: Setting module, used to set wind speed and atmospheric scenes; A modulation control module is connected to the input module and is used to calculate the Doppler frequency shift corresponding to different time points according to the set wind speed and convert it into a frequency shift control signal; the modulation control module is also used to convert the set atmospheric scene into an intensity control signal; The modulation and amplification module is used to perform frequency modulation and amplitude modulation on the seed laser input by the radar system under test according to the frequency shift control signal and intensity control signal generated by the modulation control module under the drive of the driving module, and perform optical power amplification to obtain a simulated echo signal; wherein the amplitude modulation is used to simulate the scattering and extinction of the laser by the atmospheric components, and the frequency modulation is used to simulate the radial wind speed; The coupler is used to couple the analog echo signal into the radar system under test, and generate a beat signal with the seed laser of the radar system under test, so that the radar system under test obtains the data of the analog echo signal according to the beat signal for inversion, and completes the calibration by comparing the inverted data with the data of the analog echo signal.

2. The coherent wind laser radar calibration system according to claim 1, characterized in that: The modulation and amplification module is time synchronized with the coherent wind measurement laser radar system under test, and the synchronization signal is provided by the coherent wind measurement laser radar system under test.

3. The coherent wind laser radar calibration system according to claim 1, characterized in that: The modulation and amplification module specifically matches the radar system under test with different repetition frequencies through a synchronization signal.

4. The coherent wind laser radar calibration system according to claim 1, characterized in that: The coupler is also used to control the divergence angle of the simulated echo signal diverged through the flat top to be much larger than the receiving field of view angle of the laser radar to be tested.

5. The coherent wind laser radar calibration system according to claim 1, characterized in that: The modulation and amplification module performs intermediate frequency modulation on the seed laser, and the range is 80MHz-200MHz.

6. The coherent wind laser radar calibration system according to claim 1, characterized in that: The setting module is specifically used to freely set the wind speed information and the atmospheric scene through user input, or to set them by selecting preset wind speeds and atmospheric scenes of different levels.

7. The coherent wind laser radar calibration system according to claim 6, characterized in that: The preset wind speed levels include squall frequency, strong wind frequency and moderate wind frequency.

8. The coherent wind laser radar calibration system according to claim 6, characterized in that: The preset different atmospheric scenes include heavy pollution, moderate pollution and light pollution. Different atmospheric scenes correspond to different aerosol particles' absorption and scattering of light.

9. A coherent wind laser radar calibration method, characterized in that: The following steps are involved: Set wind speed and atmospheric scenes; The Doppler frequency shift corresponding to different time points is calculated according to the set wind speed and converted into a frequency shift control signal; the set atmospheric scene is converted into an intensity control signal; The seed laser input to the radar system under test is frequency modulated and amplitude modulated according to the frequency shift control signal and the intensity control signal, and the optical power is amplified to obtain a simulated echo signal; Amplitude modulation is used to simulate the scattering and extinction of laser light by atmospheric components, and frequency modulation is used to simulate radial wind speed. The simulated echo signal is coupled into the radar system under test, and a beat frequency signal is generated with the seed laser of the radar system under test, so that the radar system under test obtains data of the simulated echo signal according to the beat frequency signal for inversion; The inverted data is compared with the data of the simulated echo signal to complete the calibration.

10. The coherent wind laser radar calibration method according to claim 9, characterized in that: When frequency modulation and amplitude modulation are performed, the coherent wind measurement lidar system under test provides a synchronization signal to achieve time synchronization.

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