Rayleigh wind lidar frequency discrimination method and system

Abstract

The invention belongs to the technical field of laser radars, and particularly relates to a Rayleigh wind measurement laser radar frequency discrimination method and system. The frequency discrimination method comprises the following steps: emitting dual-frequency laser to the atmosphere in a time-sharing manner, and receiving an atmosphere echo signal after interaction between the dual-frequency laser and atmospheric molecules; introducing the atmospheric echo signal into an energy detection channel and a Fabry-Perot interferometer channel through a spectroscope; acquiring the signal intensity of the dual-frequency laser passing through the energy detection channel and the signal intensity of the dual-frequency laser passing through a Brillouin-Perot interferometer channel; and the Doppler frequency shift amount is obtained through the signal intensity of the dual-frequency laser after passing through the energy detector channel and the Fabry-Perot interferometer channel. The method has the advantages of being high in implementation performance, capable of reducing cost and complexity and high in optical stability.

Description

Technical Field

[0001] The invention belongs to the technical field of laser radars, and in particular relates to a frequency discrimination method and system of a Rayleigh wind laser radar. Background Art

[0002] The discriminator is the core component of the incoherent Rayleigh wind laser radar, which is used to detect the Doppler frequency shift of the atmospheric echo signal scattered by atmospheric molecules, and realize the measurement of wind speed. At present, the dual-channel or three-channel Fabry-Perot interferometer is mainly used as the discriminator to detect the Doppler frequency shift of the atmospheric echo signal scattered by atmospheric molecules. In order to achieve locking with the laser frequency, the discriminator of the Fabry-Perot interferometer is required to have a precise cavity length tuning function, and during the cavity length tuning process, the two interferometer cavity mirrors remain in parallel, which has a very high technical threshold.

[0003] At present, the two main technical solutions being studied in China are interferometer filters and atomic and molecular filters. For atomic and molecular filters, the edge of the absorption spectrum of suitable atoms or molecules is mainly used to make a single edge discriminator. For example, the Ocean University of China uses the absorption spectrum of iodine molecules, and the Wuhan Institute of Physics and Mathematics of the Chinese Academy of Sciences uses the absorption spectrum of sodium atoms. The atomic and molecular filter determines that this technology can only be applied to laser radars of a certain wavelength. For example, iodine molecular filters are mainly used in green light bands such as 532nm wavelength, and sodium atomic filters are used for 589nm wavelength. Due to the limitations of sky background light and laser technology, the detection performance of Rayleigh wind laser radar using these two discriminators is reduced during the day. Therefore, there is an urgent need for a frequency discrimination method and system for Rayleigh wind laser radar. Summary of the invention

[0004] In order to solve the above problems, the present application discloses a frequency discrimination method and system for a Rayleigh wind laser radar.

[0005] A frequency discrimination method for a Rayleigh wind laser radar comprises the following steps:

[0006] emitting dual-frequency lasers into the atmosphere in a time-sharing manner, and receiving atmospheric echo signals after the dual-frequency lasers interact with atmospheric molecules;

[0007] The atmospheric echo signal is introduced into the energy detection channel and the Fabry-Perot interferometer channel respectively through a spectroscope;

[0008] Acquire the signal intensity of the dual-frequency laser passing through the energy detection channel and the signal intensity of the dual-frequency laser passing through the Brillouin-Perot interferometer channel;

[0009] The Doppler frequency shift amount is obtained through the signal intensity of the dual-frequency laser after passing through the energy detector channel and the Fabry-Perot interferometer channel.

[0010] Furthermore, the frequency of the dual-frequency laser is locked to a first preset value and a second preset value, and the first preset value and the second preset value are symmetrical about the center frequency of the Fabry-Perot interferometer, and the dual-frequency laser is input into the Fabry-Perot interferometer channel alternately in time division;

[0011] The Fabry-Perot interferometer is a single-channel Fabry-Perot interferometer, and the central wavelength is not tunable.

[0012] Furthermore, obtaining the Doppler frequency shift amount by the signal intensity after the dual-frequency laser passes through the Fabry-Perot interferometer specifically comprises the following steps:

[0013] Through simulation, a response function lookup table is obtained based on the performance parameters detected by the Rayleigh wind laser radar, the frequency value of the dual-frequency laser, and the transmittance function of the Fabry-Perot interferometer;

[0014] Based on the signal intensity of the dual-frequency laser passing through the energy detection channel and the signal intensity after passing through the Fabry-Perot interferometer channel in actual measurement, a response function is calculated;

[0015] The Doppler frequency shift amount is obtained by searching the response function lookup table using the response function.

[0016] Furthermore, the response function lookup table is obtained through simulation based on the performance parameters detected by the Rayleigh wind laser radar, the frequency value of the dual-frequency laser, and the transmittance function of the Fabry-Perot interferometer, including:

[0017] Under simulation conditions, an atmospheric echo signal corresponding to the dual-frequency laser is obtained under performance parameter conditions based on Rayleigh wind laser radar detection;

[0018] The signal strength I in the energy detection channel where the dual-frequency laser is located is obtained based on the atmospheric echo signal. E，i ; Based on the atmospheric echo signal and the transmittance function of the Fabry-Perot interferometer, the signal strength I after passing through the Fabry-Perot interferometer is obtained R，i ;

[0019] Based on the signal strength I E，i and signal strength I R，i Get the response function lookup table.

[0020] Furthermore, the step of obtaining the atmospheric echo signal corresponding to the dual-frequency laser under the performance parameter conditions of Rayleigh wind laser radar detection under the simulation conditions includes:

[0021] The atmospheric echo signal received by the Rayleigh wind lidar telescope between the vertical heights z and z+Δz is obtained as:

[0022]

[0023] Where: m is the pulse accumulation number; G(z) is the geometric overlap factor of the laser radar; η 0 is the total transmittance of the transmitting and receiving optical units; η is the quantum efficiency of the detector; E 0 is the emitted laser pulse energy; L is the wavelength of the emitted laser; h = 6.626 × 10 -34 J is Planck's constant; c = 3 × 10 8 m / s is the speed of light; A 0 is the receiving area of ​​the receiving telescope; z is the vertical height; Δz is the vertical distance resolution; β M (λ L ,z) and β R (λ L , z) are the backscattering coefficients of atmospheric molecules and aerosols respectively; α=α M +α R is the total extinction coefficient, α M is the atmospheric molecular extinction coefficient, α R is the aerosol extinction coefficient.

[0024] Furthermore, the signal strength I in the energy detection channel where the dual-frequency laser is located is obtained based on the atmospheric echo signal. E，i ; Based on the atmospheric echo signal and the transmittance function of the Fabry-Perot interferometer, the signal strength I after passing through the Fabry-Perot interferometer is obtained R，i ,include:

[0025] The signal strength I in the energy detection channel where the dual-frequency laser is located is obtained based on the atmospheric echo signal. E，i , based on the atmospheric echo signal and the transmittance function of the Fabry-Perot interferometer, the signal strength I after passing through the Fabry-Perot interferometer is obtained. R，i , signal strength I E，i and signal strength I R，i The expression is:

[0026] I E,i =a 2 I i (2)

[0027] I R,i =a 1 I i T R,i (3)

[0028] Among them, a 1 , a 2are calibration constants, which are the transmittance calibration constant and reflectance calibration constant of the spectrometer respectively. where f R,i (v) is the broadened spectrum of Rayleigh scattering under the action of dual-frequency laser; h is the transmittance curve of Fabry-Perot interferometer; represents convolution, i=1,2, and v is the echo signal frequency.

[0029] The present application also discloses another inventive concept, a frequency discrimination system of a Rayleigh wind laser radar, the frequency discrimination system comprising a transmitting unit, a receiving unit and a data processing unit;

[0030] The transmitting unit is used to transmit two-frequency lasers into the atmosphere in a time-sharing manner;

[0031] The receiving unit includes a first spectroscope, an energy detection channel and a Fabry-Perot interferometer channel;

[0032] The first beam splitter is used to introduce the received atmospheric echo signal into the energy detection channel and the Fabry-Perot interferometer channel respectively;

[0033] The data processing unit is connected to the transmitting unit and the receiving unit respectively, and is used to execute the above-mentioned frequency discrimination method of the Rayleigh wind laser radar.

[0034] Furthermore, the frequency discrimination system also includes a frequency locking unit, which includes a second optical fiber, and the two ends of the second optical fiber are respectively connected to the transmitting unit and the receiving unit. The frequency locking unit is used to lock the frequency of the dual-frequency laser to a first preset value and a second preset value respectively, and input them into the Fabry-Perot interferometer channel alternately in time-sharing.

[0035] Further, the Fabry-Perot interferometer channel includes a Fabry-Perot interferometer, a first filter, a first focusing lens and a first photomultiplier tube which are arranged in sequence, and the first photomultiplier tube is connected to the data processing unit;

[0036] The energy detection channel includes a second filter, a second focusing lens and a second photomultiplier tube which are arranged in sequence, and the second photomultiplier tube is connected to the data processing unit.

[0037] Furthermore, the transmitting unit also includes a second spectroscope, an energy monitoring module and a frequency monitoring module, wherein the second spectroscope is used to direct the laser emitted by the laser into the energy monitoring module and the frequency monitoring module, and the energy monitoring module and the frequency monitoring module are connected to the data processing unit.

[0038] Beneficial effects:

[0039] (1) Technical feasibility: Using a dual-channel or triple-channel Fabry-Perot interferometer as a frequency discrimination system for detecting the Doppler frequency shift of atmospheric echo signals scattered by atmospheric molecules, in order to achieve locking with the laser frequency, the frequency discriminator of the Fabry-Perot interferometer is required to have a precise cavity length tuning function, and during the cavity length tuning process, the two interferometer cavity mirrors remain in parallel, which has a very high technical threshold. However, this application uses dual-frequency ratio frequency discrimination technology to use a laser to emit dual-frequency lasers in a time-sharing manner. The two laser frequencies are symmetrically distributed on both sides of the center frequency of the single-channel Fabry-Perot interferometer, and the technical feasibility is relatively strong.

[0040] (2) Reduce cost and complexity: By adopting dual-frequency ratio frequency discrimination technology and using a single-channel Fabry-Perot interferometer instead of the traditional dual-channel or triple-channel Fabry-Perot interferometer, the size of the discrimination system can be greatly reduced while meeting the detection accuracy requirements. The optical path is relatively simple, and the cost of the discrimination system is reduced.

[0041] (3) Optical stability: By using a single-channel Fabry-Perot interferometer based on laser frequency hopping technology to replace the traditional dual-channel or triple-channel Fabry-Perot interferometer frequency detection technology, it is no longer necessary for the two interferometer cavity mirrors to remain in parallel during the adjustment process, thereby improving the optical stability of the detection system.

[0042] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 A frequency discrimination principle diagram of a Rayleigh wind laser radar according to an embodiment of the present invention is shown;

[0045] Figure 2 It shows a convolution diagram of atmospheric molecular spectral lines and etalon transmittance in a frequency discrimination method of a Rayleigh wind laser radar according to an embodiment of the present invention;

[0046] Figure 3 It shows various energy and transmittance curves in a frequency discrimination method of a Rayleigh wind laser radar according to an embodiment of the present invention;

[0047] Figure 4 A relationship diagram between a signal response function and Doppler frequency shift of a Rayleigh wind laser radar using a frequency discrimination method according to an embodiment of the present invention is shown;

[0048] Figure 5 A response function lookup table diagram of a frequency discrimination method of a Rayleigh wind laser radar according to an embodiment of the present invention is shown;

[0049] Figure 6 A structural principle diagram of a frequency discrimination system of a Rayleigh wind laser radar according to an embodiment of the present invention is shown.

[0050] In the figure: 10, laser; 11, second collimator; 12, second spectroscope; 13, energy monitoring module; 14, frequency monitoring module; 20, receiving telescope; 21, first collimator; 22, beam expander; 23, first spectroscope; 241, Fabry-Perot interferometer; 242, first filter; 243, first focusing lens; 244, first photomultiplier tube; 251, second filter; 252, second focusing lens; 253, second photomultiplier tube. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] like Figure 1 As shown, the present invention discloses a frequency discrimination method for Rayleigh wind laser radar, and the frequency discrimination method comprises the following steps:

[0053] emitting dual-frequency lasers into the atmosphere in a time-sharing manner, and receiving atmospheric echo signals after the dual-frequency lasers interact with atmospheric molecules;

[0054] The atmospheric echo signal is introduced into the energy detection channel and the Fabry-Perot interferometer channel respectively through a spectroscope;

[0055] Acquire the signal intensity of the dual-frequency laser passing through the energy detection channel and the signal intensity of the dual-frequency laser passing through the Brillouin-Perot interferometer channel;

[0056] The Doppler frequency shift amount is obtained through the signal intensity of the dual-frequency laser after passing through the energy detector channel and the Fabry-Perot interferometer channel.

[0057] Furthermore, the frequency of the dual-frequency laser is correspondingly locked at a first preset value and a second preset value, and the first preset value and the second preset value are symmetrical about the center frequency of the Fabry-Perot interferometer, and the dual-frequency laser is input into the Fabry-Perot interferometer channel alternately in time division. The purpose of locking is to lock the dual-frequency laser near the waistline of the FP interferometer, and on the basis of laser locking, the optimal frequency discrimination sensitivity and accuracy can be obtained.

[0058] Exemplarily, the center frequency of the Fabry-Perot interferometer is v 0 , laser frequency v 1 and the laser frequency v 2 Located at the center frequency v 0 on both sides, and with the center frequency v 0 The absolute difference is the same. The laser is used to emit dual-frequency lasers in time-sharing mode. The two laser frequencies are symmetrically distributed on both sides of the center frequency of the single-channel Fabry-Perot interferometer, which converts the traditional dual-edge technology into adjusting the emission frequency of the laser. The technology is highly feasible.

[0059] In one embodiment, the actual optimized value near the waistline of the FP interferometer is ±2.1 GHz around the center frequency, that is, the laser hopping frequency is 4.2 GHz, which can also be said to be a dual-frequency laser interval.

[0060] The Fabry-Perot interferometer is a single-channel Fabry-Perot interferometer, and the central wavelength is not tunable. The Fabry-Perot interferometer has only one receiving channel, and the central wavelength is not tunable. The existing technology is basically a three-channel FP interferometer. This technology uses a single-channel Fabry-Perot interferometer, and uses dual-frequency laser technology instead of the original dual-edge technology. When the dual-frequency laser is time-sharing emitted, there will be a certain delay in time, which can be obtained through the first optical fiber transmission and the acquisition card to collect the time-sharing signal.

[0061] Furthermore, the calculation of the Doppler frequency shift amount based on the signal strength of the dual-frequency laser after passing through the Fabry-Perot interferometer specifically includes the following steps:

[0062] The method of obtaining the Doppler frequency shift amount by the signal intensity after the dual-frequency laser passes through the Fabry-Perot interferometer specifically comprises the following steps:

[0063] Through simulation, a response function lookup table is obtained based on the performance parameters detected by the Rayleigh wind laser radar, the frequency value of the dual-frequency laser, and the transmittance function of the Fabry-Perot interferometer;

[0064] Based on the signal intensity of the dual-frequency laser passing through the energy detection channel and the signal intensity after passing through the Fabry-Perot interferometer channel in actual measurement, a response function is calculated;

[0065] The Doppler frequency shift amount is obtained by searching the response function lookup table using the response function.

[0066] The response function lookup table is obtained through simulation based on the performance parameters detected by the Rayleigh wind laser radar, the frequency value of the dual-frequency laser, and the transmittance function of the Fabry-Perot interferometer, including:

[0067] Under simulation conditions, an atmospheric echo signal corresponding to the dual-frequency laser is obtained under performance parameter conditions based on Rayleigh wind laser radar detection;

[0068] The signal strength I in the energy detection channel where the dual-frequency laser is located is obtained based on the atmospheric echo signal. E，i ; Based on the atmospheric echo signal and the transmittance function of the Fabry-Perot interferometer, the signal strength I after passing through the Fabry-Perot interferometer is obtained R，i ;

[0069] Based on the signal strength I E，i and signal strength I R，i Get the response function lookup table.

[0070] In one embodiment, the performance input parameters of Rayleigh wind laser radar detection are set as follows:

[0071]

[0072] For example, the time-sharing emission of dual-frequency laser into the atmosphere refers to the emission of two lasers of different frequencies into the atmosphere by a laser at a predetermined pulse repetition frequency. For example, a laser with a central wavelength of 355 nm emits a laser with a frequency of v into the atmosphere at a pulse repetition frequency of 60 Hz. 1 and v 2 The dual-frequency laser beam is input into the Fabry-Perot interferometer channel in a time-sharing manner. After the dual-frequency laser interacts with atmospheric molecules in the atmosphere, it is received by the receiving telescope and enters the frequency discrimination system. The signal entering the frequency discrimination system includes the backscattered spectrum line f of the atmospheric molecules. R,i ; Atmospheric echo signal I entering the frequency discrimination system i , i=1,2.

[0073] Furthermore, the step of obtaining the atmospheric echo signal corresponding to the dual-frequency laser under the performance parameter conditions of Rayleigh wind laser radar detection under the simulation conditions includes:

[0074] The atmospheric echo signal received by the Rayleigh wind lidar telescope between the vertical heights z and z+Δz is obtained as:

[0075]

[0076] Where: m is the pulse accumulation number; G(z) is the geometric overlap factor of the laser radar; η 0 is the total transmittance of the transmitting and receiving optical units; η is the quantum efficiency of the detector; E 0 is the emitted laser pulse energy; L is the wavelength of the emitted laser; h = 6.626 × 10 -34 J is Planck's constant; c = 3 × 10 8 m / s is the speed of light; A 0 is the receiving area of ​​the receiving telescope; z is the vertical height; Δz is the vertical distance resolution; β M (λ L ,z) and β R (λ L , z) are the backscattering coefficients of atmospheric molecules and aerosols respectively; α=α M +α R is the total extinction coefficient, α M is the atmospheric molecular extinction coefficient, α R is the aerosol extinction coefficient.

[0077] After entering the frequency discrimination system, the atmospheric echo signal is expanded by a beam expander and then split by a beam splitter. A small portion of the signal is directed to the energy detection channel, while the remaining signal is directed to the Fabry-Perot interferometer channel through a beam splitter.

[0078] The signal strength I in the energy detection channel where the dual-frequency laser is located is obtained based on the atmospheric echo signal E，i ; Based on the atmospheric echo signal and the transmittance function of the Fabry-Perot interferometer, the signal strength I after passing through the Fabry-Perot interferometer is obtained R，i , signal strength I E，i and signal strength I R，i The expression is:

[0079] I E,i =a 2 I i (2)

[0080] I R,i =a 1 I i T R,i (3)

[0081] Among them, a 1 , a 2 are calibration constants, which are the transmittance calibration constant and reflectance calibration constant of the spectrometer respectively. where f R,i (v) is the broadened spectrum of Rayleigh scattering under the action of dual-frequency laser; h is the transmittance function of Fabry-Perot interferometer; represents convolution, where i = 1, 2, v is the echo signal frequency, Figure 2 The frequency is v 1 and frequency v 2 Convolution curve of the corresponding Rayleigh scattering broadening spectrum line and the transmittance function of the Fabry-Perot interferometer under the action of dual-frequency laser.

[0082] like Figure 3 As shown in the figure, when there is no Doppler frequency shift, the intensities of the atmospheric echo scattering signals at the two frequencies received by the Fabry-Perot interferometer are the same; when the frequency of the atmospheric echo signal moves forward, the laser frequency v received after the Fabry-Perot interferometer 1 The atmospheric echo signal strength increases, and the laser frequency v 2 The intensity of the atmospheric echo signal on the surface decreases; similarly, when the frequency of the atmospheric echo signal moves negatively, the laser frequency v received after passing through the Fabry-Perot interferometer 1 The atmospheric echo signal intensity decreases, and the laser frequency v 2 The atmospheric echo signal strength increases. Combining the above theory, according to the signal strength I R,2 and signal strength I R,1 The Doppler frequency shift can be calculated.

[0083] Further, based on the signal strength I E，i and signal strength I R，i Obtaining a response function lookup table includes the following steps:

[0084] Specifically, the response function lookup table includes the relationship between the Doppler frequency shift and the response function corresponding to the temperature, based on the signal strength I E，i and signal strength I R，i Get the response function lookup table, including:

[0085] The response functions corresponding to the Doppler frequency shift and temperature are obtained and expressed as

[0086]

[0087] R Temp =T R,1 +T R,2 (4)

[0088] Among them, v d represents the Doppler frequency shift of the echo signal, Temp represents the temperature corresponding to the height at which the echo signal is collected, T R,1 The frequency is v 1 The Fabry-Perot interferometer transmittance corresponding to the laser, T R,2 The frequency is v 2The Fabry-Perot interferometer transmittance corresponding to the laser is Figure 4 The frequency is v 1 and frequency v 2 The response function of the Doppler frequency shift corresponding to the dual-frequency laser.

[0089]

[0090] Where k is the scaling factor, I R,1 It represents the signal intensity measured after the atmospheric echo signal corresponding to the first frequency laser passes through the Fabry-Perot interferometer, I E,1 It indicates the signal intensity of the atmospheric echo signal corresponding to the first frequency laser through the energy detection channel; I R,2 It represents the signal intensity detected by the atmospheric echo signal corresponding to the second frequency laser after passing through the Fabry-Perot interferometer, I E,2 It indicates the signal strength of the atmospheric echo signal corresponding to the second frequency laser passing through the energy detection channel.

[0091] Combining formula (4), (5), (6) and simplifying, we get:

[0092]

[0093] In theory, I can be calculated based on the atmospheric model and the lidar equation. R,1 ,I E,2 ,I R,2 ,I E,1 , and then the response function corresponding to the Doppler frequency shift in the theoretical case can be calculated according to formula (7).

[0094] Substituting the atmospheric echo signal obtained in the simulation according to formula (1) into formula (2) can obtain the signal intensity I of the two frequency lasers in the energy detection channel: E，i , and the signal strength I after passing through the Fabry-Perot interferometer is obtained by formula (3) R，i Based on the performance parameters of the Rayleigh wind lidar detection and the frequency values ​​corresponding to the dual-frequency laser, the following is obtained: Figure 5 The response function curve corresponding to the Doppler frequency shift and temperature is shown.

[0095] In the actual measurement process, the response function measured by the laser radar experiment is substituted into the frequency response function curve obtained under the theoretical condition for comparison, and the corresponding frequency shift can be found. Figure 5As shown, the response function curve under theoretical conditions is directly compared with the response function curve under actual conditions. If the actual response function is (1.34, 0.43), a search in the two-dimensional lookup table shows that the temperature is around 210K, that is, the Doppler frequency shift we get is -0.242GHz.

[0096] Furthermore, due to the effect of atmospheric wind or the movement of atmospheric particles, the received light frequency has a Doppler shift relative to the transmitted laser. The Doppler frequency measured by the laser radar system is analyzed by optical spectrum analysis, so the radial wind speed V can be directly obtained by the following formula: r :

[0097]

[0098] like Figure 6 As shown, in another embodiment of the present invention, a frequency discrimination system of a Rayleigh wind laser radar is also disclosed. The frequency discrimination system includes a transmitting unit, a receiving unit and a data processing unit 26.

[0099] The transmitting unit is used to transmit two-frequency lasers into the atmosphere in a time-sharing manner;

[0100] The receiving unit includes a receiving telescope 20, a first collimator 21, a beam expander 22, and a first beam splitter 23 arranged in sequence according to the optical path, and also includes an energy detection channel and a Fabry-Perot interferometer channel arranged in parallel;

[0101] The first beam splitter 23 is used to introduce the received atmospheric echo signal into the energy detection channel and the Fabry-Perot interferometer channel respectively;

[0102] The data processing unit 26 is connected to the transmitting unit and the receiving unit respectively, and is used to execute the frequency discrimination method of the Rayleigh wind laser radar described in any one of the above embodiments.

[0103] Specifically, the laser 10 emits two frequencies of laser light into the atmosphere in a time-sharing manner. After interacting with atmospheric molecules, the backscattered signal is received by the receiving telescope 20. The backscattered signal is transmitted to the beam expander 22 through the first optical fiber and the first collimator 21. After beam expansion by the beam expander 22, the backscattered signal is emitted to the first beam splitter 23. The first beam splitter 23 sends a small part of the backscattered signal to the energy detection channel, and the remaining signal is introduced into the Fabry-Perot interferometer channel. The energy detection channel and the Fabry-Perot interferometer channel send the output signal to the data processing unit 26, and the data processing unit 26 performs frequency discrimination through the output signal.

[0104] Furthermore, the frequency discrimination system also includes a frequency locking unit, and the frequency discrimination system also includes a frequency locking unit, and the frequency locking unit includes a second optical fiber, and the two ends of the second optical fiber are respectively connected to the transmitting unit and the receiving unit. Specifically, the two ends of the second optical fiber are respectively connected to the laser 10 and the first collimator 21, and are used to lock the frequency of the dual-frequency laser emitted by the transmitting unit in time-sharing correspondence to the first preset value and the second preset value, and the first preset value and the second preset value are symmetrical about the center frequency of the Fabry-Perot interferometer 241, and the dual-frequency laser is alternately input into the Fabry-Perot interferometer channel in time-sharing, wherein the Fabry-Perot interferometer is a single-channel Fabry-Perot interferometer, and the center wavelength is not tunable.

[0105] Further, the Fabry-Perot interferometer channel includes a Fabry-Perot interferometer 241, a first filter 242, a first focusing lens 243 and a first photomultiplier tube 244 which are arranged in sequence, and the first photomultiplier tube 244 is connected to the data processing unit 26;

[0106] The energy detection channel includes a second filter 251 , a second focusing lens 252 , and a second photomultiplier tube 253 which are arranged in sequence. The second photomultiplier tube 253 is connected to the data processing unit 26 .

[0107] Specifically, after the received signal passes through the Fabry-Perot interferometer 241 , the first filter 242 filters it, and then it is focused by the first focusing lens 243 and then collected by the first photomultiplier tube 244 , and the first photomultiplier tube 244 is connected to the data processing unit 26 .

[0108] After the first spectroscope 23 introduces the backscattered signal into the energy detection channel, the second filter 251 filters it, and then it is focused by the second focusing lens 252 and collected by the second photomultiplier tube 253. The second photomultiplier tube 253 is connected to the data processing unit 26.

[0109] Furthermore, the transmitting unit also includes a second collimator 11, a second spectrometer 12, an energy monitoring module 13 and a frequency monitoring module 14 arranged in sequence according to the optical path, and the second spectrometer 12 is used to guide the laser emitted by the laser 10 into the energy monitoring module 13 and the frequency monitoring module 14, and the energy monitoring module 13 and the frequency monitoring module 14 are connected to the data processing unit 26.

[0110] Specifically, the laser 10 guides a small portion of the emitted laser into the second beam splitter 12 through the third optical fiber via the second collimator 11, and the second beam splitter 12 splits the laser beam. One laser beam enters the energy monitoring module 13, and the other laser beam enters the frequency monitoring module 14. The energy monitoring module 13 and the frequency monitoring module 14 are connected to the data processing unit 26 to transmit the energy and frequency of the incoming laser to the data processing unit 26.

[0111] Specifically, the purpose of the monitoring module is to monitor the performance of the emitted laser, including the emitted energy and frequency stability. The data processing unit 26 is connected to the laser 10 and controls the laser beam energy and frequency of the laser 10 by processing the signal obtained from the monitoring module.

[0112] In another embodiment of the present invention, a computer device is disclosed, including a processor and a storage medium, wherein a computer program is stored on the storage medium. The processor reads and runs the computer program from the storage medium to execute the frequency discrimination method of the Rayleigh wind laser radar as described in any one of the above embodiments.

[0113] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A frequency discrimination method for Rayleigh wind laser radar, characterized in that: The following steps are involved: emitting dual-frequency lasers into the atmosphere in a time-sharing manner, and receiving atmospheric echo signals after the dual-frequency lasers interact with atmospheric molecules; The atmospheric echo signal is introduced into the energy detection channel and the Fabry-Perot interferometer channel respectively through a spectroscope; Acquire the signal intensity of the dual-frequency laser passing through the energy detection channel and the signal intensity of the dual-frequency laser passing through the Brillouin-Perot interferometer channel; The Doppler frequency shift amount is obtained through the signal intensity of the dual-frequency laser after passing through the energy detector channel and the Fabry-Perot interferometer channel.

2. The frequency discrimination method of Rayleigh wind laser radar according to claim 1, characterized in that: The frequencies of the dual-frequency laser are locked to a first preset value and a second preset value, and the first preset value and the second preset value are symmetrical about the center frequency of the Fabry-Perot interferometer. The dual-frequency laser is input into the Fabry-Perot interferometer channel alternately in a time-sharing manner. The Fabry-Perot interferometer is a single-channel Fabry-Perot interferometer, and the central wavelength is not tunable.

3. The frequency discrimination method of Rayleigh wind laser radar according to claim 2, characterized in that: The method of obtaining the Doppler frequency shift amount by the signal intensity after the dual-frequency laser passes through the Fabry-Perot interferometer specifically comprises the following steps: Through simulation, a response function lookup table is obtained based on the performance parameters detected by the Rayleigh wind laser radar, the frequency value of the dual-frequency laser, and the transmittance function of the Fabry-Perot interferometer; Based on the signal intensity of the dual-frequency laser passing through the energy detection channel and the signal intensity after passing through the Fabry-Perot interferometer channel in actual measurement, a response function is calculated; The Doppler frequency shift amount is obtained by searching the response function lookup table using the response function.

4. The frequency discrimination method of Rayleigh wind laser radar according to claim 3, characterized in that: The response function lookup table is obtained through simulation based on the performance parameters detected by the Rayleigh wind laser radar, the frequency value of the dual-frequency laser, and the transmittance function of the Fabry-Perot interferometer, including: Under simulation conditions, an atmospheric echo signal corresponding to the dual-frequency laser is obtained under performance parameter conditions based on Rayleigh wind laser radar detection; The signal strength I in the energy detection channel where the dual-frequency laser is located is obtained based on the atmospheric echo signal. E，i ; Based on the atmospheric echo signal and the transmittance function of the Fabry-Perot interferometer, the signal strength I after passing through the Fabry-Perot interferometer is obtained R，i ; Based on the signal strength I E，i and signal strength I R，i Get the response function lookup table.

5. The frequency discrimination method of Rayleigh wind laser radar according to claim 4, characterized in that: The step of obtaining the atmospheric echo signal corresponding to the dual-frequency laser under the performance parameter conditions of Rayleigh wind laser radar detection under the simulation conditions includes: The atmospheric echo signal received by the Rayleigh wind lidar telescope between the vertical heights z and z+Δz is obtained as: Where: m is the pulse accumulation number; G(z) is the geometric overlap factor of the laser radar; η0 is the total transmittance of the transmitting and receiving optical units; η is the quantum efficiency of the detector; E0 is the energy of the transmitted laser pulse; λ L is the wavelength of the emitted laser; h = 6.626 × 10 -34 J is Planck's constant; c = 3 × 10 8 m / s is the speed of light; A0 is the receiving area of ​​the receiving telescope; z is the vertical height; Δz is the vertical distance resolution; β M (λ L ,z) and β R (λ L , z) are the backscattering coefficients of atmospheric molecules and aerosols respectively; α=α M +α R is the total extinction coefficient, α M is the atmospheric molecular extinction coefficient, α R is the aerosol extinction coefficient.

6. The frequency discrimination method of Rayleigh wind laser radar according to claim 5, characterized in that: The signal strength I in the energy detection channel where the dual-frequency laser is located is obtained based on the atmospheric echo signal E，i ; Based on the atmospheric echo signal and the transmittance function of the Fabry-Perot interferometer, the signal strength I after passing through the Fabry-Perot interferometer is obtained R，i ,include: The signal strength I in the energy detection channel where the dual-frequency laser is located is obtained based on the atmospheric echo signal. E，i , based on the atmospheric echo signal and the transmittance function of the Fabry-Perot interferometer, the signal strength I after passing through the Fabry-Perot interferometer is obtained. R，i , signal strength I E，i and signal strength I R，i The expression is: I E,i =a2I i (2) I R,i =a1I i T R,i (3) Among them, a1 and a2 are calibration constants, which are the transmittance calibration constant and reflectance calibration constant of the spectrometer respectively. where f R,i (v) is the broadened spectrum of Rayleigh scattering under the action of dual-frequency laser; h is the transmittance curve of Fabry-Perot interferometer; represents convolution, i=1,2, ν is the echo signal frequency.

7. A frequency discrimination system for a Rayleigh wind laser radar, characterized in that: The frequency discrimination system includes a transmitting unit, a receiving unit and a data processing unit; The transmitting unit is used to transmit two-frequency lasers into the atmosphere in a time-sharing manner; The receiving unit includes a first spectroscope, an energy detection channel and a Fabry-Perot interferometer channel; The first beam splitter is used to introduce the received atmospheric echo signal into the energy detection channel and the Fabry-Perot interferometer channel respectively; The data processing unit is connected to the transmitting unit and the receiving unit respectively, and is used to execute the frequency discrimination method of the Rayleigh wind laser radar described in any one of claims 1-6.

8. The frequency discrimination system of the Rayleigh wind laser radar according to claim 7, characterized in that: The frequency discrimination system also includes a frequency locking unit, which includes a second optical fiber, and the two ends of the second optical fiber are respectively connected to the transmitting unit and the receiving unit. The frequency locking unit is used to lock the frequency of the dual-frequency laser to a first preset value and a second preset value respectively, and input them into the Fabry-Perot interferometer channel alternately in time-sharing.

9. The frequency discrimination system of the Rayleigh wind laser radar according to claim 7, characterized in that: The Fabry-Perot interferometer channel comprises a Fabry-Perot interferometer, a first filter, a first focusing lens and a first photomultiplier tube which are arranged in sequence, and the first photomultiplier tube is connected to the data processing unit; The energy detection channel includes a second filter, a second focusing lens and a second photomultiplier tube which are arranged in sequence, and the second photomultiplier tube is connected to the data processing unit.

10. The frequency discrimination system of the Rayleigh wind laser radar according to claim 7, characterized in that: The transmitting unit also includes a second spectroscope, an energy monitoring module and a frequency monitoring module. The second spectroscope is used to guide the laser emitted by the laser into the energy monitoring module and the frequency monitoring module. The energy monitoring module and the frequency monitoring module are connected to the data processing unit.

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