A frequency discrimination method and system for a Rayleigh wind lidar

Abstract

The present application belongs to the technical field of laser radar, and particularly relates to a frequency discrimination method and system for Rayleigh wind measurement laser radar. The frequency discrimination method comprises the following steps: time-divisionally emitting dual-frequency laser into the atmosphere, receiving atmospheric backwave signals after the dual-frequency laser interacts with atmospheric molecules; introducing the atmospheric backwave signals into an energy detection channel and a Fabry-Perot interferometer channel through a beam splitter respectively; acquiring signal intensity of the dual-frequency laser passing through the energy detection channel and signal intensity of the dual-frequency laser passing through the Fabry-Perot interferometer channel; and obtaining a Doppler frequency shift amount through the signal intensity of the dual-frequency laser passing through the energy detection channel and the Fabry-Perot interferometer channel. The present application has the characteristics of strong implementation, reduced cost and complexity, and strong optical stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of laser radar, and particularly relates to a frequency discrimination method and system of a Rayleigh wind measurement laser radar. BACKGROUND

[0002] The frequency discriminator is a core component of the non-coherent Rayleigh wind measurement laser radar, which is used for detecting the Doppler frequency shift of the atmospheric molecular Rayleigh scattering atmospheric echo signal to realize the measurement of the wind speed. At present, the double-channel or triple-channel Fabry-Perot interferometer is mainly used as the frequency discriminator for detecting the Doppler frequency shift of the atmospheric molecular Rayleigh scattering atmospheric echo signal. In order to realize the 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 interference cavity mirrors remain parallel, which has a very high technical threshold.

[0003] At present, two technical schemes of the interferometer filter and the atomic molecular filter are mainly researched in China. For the atomic molecular filter, a single-edge frequency discriminator is mainly made by using the edge of the absorption spectrum line of a suitable atom or molecule, for example, the iodine molecular filter of Ocean University of China and the sodium atomic filter of Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences. The atomic molecular filter determines that this technology can only be applied to a certain specific wavelength of the laser radar, for example, the iodine molecular filter is mainly used for the green light band of 532 nm wavelength, and the sodium atomic filter is used for 589 nm wavelength. Due to the limitation of the sky background light and the laser technology, the detection performance of the Rayleigh wind measurement laser radar using the two frequency discriminators is reduced in the daytime. Therefore, there is an urgent need for a frequency discrimination method and system of a Rayleigh wind measurement laser radar. SUMMARY

[0004] In view of the above problems, the application discloses a frequency discrimination method and system of a Rayleigh wind measurement laser radar.

[0005] A frequency discrimination method of a Rayleigh wind measurement laser radar, comprising the following steps:

[0006] Time-sharing emits dual-frequency laser into the atmosphere, and receives the atmospheric echo signal after the dual-frequency laser interacts with atmospheric molecules;

[0007] The atmospheric echo signal is introduced into an energy detector channel and a Fabry-Perot interferometer channel through a beam splitter respectively;

[0008] Obtains the signal intensity of the dual-frequency laser passing through the energy detector channel and the signal intensity of the dual-frequency laser passing through the Fabry-Perot interferometer channel;

[0009] Obtains the Doppler frequency shift by the signal intensity of the dual-frequency laser passing through the energy detector channel and the Fabry-Perot interferometer channel.

[0010] Further, the frequency of the dual-frequency laser corresponds to locking on 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 alternately input into the Fabry-Perot interferometer channel in time.

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

[0012] Further, the signal intensity after the dual-frequency laser passes through the Fabry-Perot interferometer to obtain the Doppler frequency shift amount includes the following steps:

[0013] Through simulation, a response function lookup table is obtained based on the performance parameters of the Rayleigh wind detection 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, the response function is calculated;

[0015] The response function is used to search in the response function lookup table to obtain the Doppler frequency shift amount.

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

[0017] Under the condition of simulation, the large atmospheric echo signal corresponding to the dual-frequency laser based on the performance parameters of the Rayleigh wind detection laser radar is obtained;

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

[0019] Based on the signal intensity I E，i and the signal intensity I R，i , a response function lookup table is obtained.

[0020] Further, the large atmospheric echo signal corresponding to the dual-frequency laser based on the performance parameters of the Rayleigh wind detection laser radar is obtained under the condition of simulation, including:

[0021] The large atmospheric echo signal received by the Rayleigh wind detection laser radar between the vertical height z~z+Δz is obtained, which is:

[0022]

[0023] 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.

[0024] Furthermore, the signal intensity 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 intensity I after passing through the Fabry-Perot interferometer is obtained R，i ,include:

[0025] The signal intensity 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 intensity 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 =a2I i (2)

[0027] I R,i =a1I i T R,i (3)

[0028] 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 a Rayleigh scattering broadened spectral line under the action of dual-frequency laser; h is a transmittance curve of the Fabry-Perot interferometer; represents convolution, i = 1, 2, and v is a frequency of the echo signal.

[0029] The application further discloses another inventive concept, a frequency discrimination system of a Rayleigh wind measurement lidar, the frequency discrimination system comprising a transmitting unit, a receiving unit and a data processing unit;

[0030] The transmitting unit is configured to transmit laser beams of two frequencies to the atmosphere in time division.

[0031] The receiving unit comprises a first beam splitter, an energy detection channel and a Fabry-Perot interferometer channel.

[0032] The first beam splitter is configured to guide the received atmospheric echo signals 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 configured to execute the frequency discrimination method of the Rayleigh wind measurement lidar.

[0034] Further, the frequency discrimination system further comprises a frequency locking unit, the frequency locking unit comprising a second optical fiber, two ends of the second optical fiber being connected to the transmitting unit and the receiving unit respectively, the frequency locking unit being configured to correspondingly lock the frequencies of the dual-frequency laser on first and second preset values and input into the Fabry-Perot interferometer channel in time division alternately.

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

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

[0037] Further, the transmitting unit further comprises a second beam splitter, an energy monitoring module and a frequency monitoring module, the second beam splitter being configured to guide the laser beams 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 requires that the frequency discriminator of the Fabry-Perot interferometer have a precise cavity length tuning function in order to achieve locking with the laser frequency. In addition, during the cavity length tuning process, the two interferometer mirrors must remain parallel, which has a very high technical threshold. However, this application uses dual-frequency ratio frequency discrimination technology to use a laser to time-share dual-frequency lasers. The two laser frequencies are symmetrically distributed on both sides of the center frequency of the single-channel Fabry-Perot interferometer, which has strong technical feasibility.

[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 volume of the frequency discrimination system can be greatly reduced while meeting the detection accuracy conditions. The optical path is relatively simple, and the cost of the frequency 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 discrimination technology, it is no longer necessary for the two interferometer cavity mirrors to remain parallel during the adjustment process, thereby improving the optical stability of the discrimination system.

[0042] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be 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 is a brief introduction to 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 any 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 Shows 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 signal response function and Doppler shift relationship diagram of a frequency discrimination method of a Rayleigh wind measurement laser radar is shown according to an embodiment of the present application;

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

[0049] Figure 6 A structure schematic diagram of a frequency discrimination system of a Rayleigh wind measurement laser radar is shown according to an embodiment of the present application.

[0050] In the figure: 10, laser; 11, second collimator; 12, second beam splitter; 13, energy monitoring module; 14, frequency monitoring module; 20, receiving telescope; 21, first collimator; 22, beam expander; 23, first beam splitter; 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] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0052] As shown in Figure 1 The present application discloses a frequency discrimination method of a Rayleigh wind measurement laser radar, which comprises the following steps:

[0053] Time-divisionally emitting dual-frequency laser into atmosphere, receiving atmospheric echo signals after the dual-frequency laser interacts with atmospheric molecules;

[0054] Introducing the atmospheric echo signals into an energy detection channel and a Fabry-Perot interferometer channel through a beam splitter respectively;

[0055] Obtaining signal intensity of the dual-frequency laser through the energy detection channel and signal intensity of the dual-frequency laser through the Fabry-Perot interferometer channel;

[0056] Obtaining Doppler shift amount through the signal intensity of the dual-frequency laser through the energy detection channel and the Fabry-Perot interferometer channel.

[0057] Further, the frequency of the dual-frequency laser is locked on 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 alternately input into the Fabry-Perot interferometer channel in time. The purpose of locking is to lock the dual-frequency laser near the waist line of the FP interferometer. On the basis of laser locking, the optimal frequency discrimination sensitivity and accuracy can be obtained.

[0058] For example, the center frequency of the Fabry-Perot interferometer is v0, the laser frequency v1 and the laser frequency v2 are located on both sides of the center frequency v0, and the absolute difference with the center frequency v0 is the same. The dual-frequency laser is emitted by the laser in time, and the two laser frequencies are symmetrically distributed on both sides of the center frequency of the single-channel Fabry-Perot interferometer. The traditional double-edge technology is converted into adjusting the emission frequency of the laser, and the technology is more implementable.

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

[0060] The Fabry-Perot interferometer is a single-channel Fabry-Perot interferometer, and the center wavelength is not tunable. The Fabry-Perot interferometer has only one receiving channel, and the center wavelength is not tunable. The prior art is basically a three-channel FP interferometer. This technology uses a single-channel Fabry-Perot interferometer to replace the original double-edge technology. When the dual-frequency laser is emitted in time, there will be a certain time delay. After the first optical fiber transmission and the acquisition card collects the time-sharing signal, it can be obtained.

[0061] Further, the signal intensity after the dual-frequency laser passes through the Fabry-Perot interferometer is calculated to obtain the Doppler frequency shift amount, which includes the following steps:

[0062] The signal intensity after the dual-frequency laser passes through the Fabry-Perot interferometer is calculated to obtain the Doppler frequency shift amount, which includes the following steps:

[0063] Through simulation, the performance parameters of the Rayleigh wind measurement laser radar, the frequency value of the dual-frequency laser, and the transmission function of the Fabry-Perot interferometer are used to obtain a response function lookup table;

[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, the response function is calculated;

[0065] The response function is used to search for the Doppler frequency shift amount in the response function lookup table.

[0066] The response function lookup table is obtained based on the performance parameters of the Rayleigh wind lidar detection, the frequency value of the double-frequency laser, and the transmittance function of the Fabry-Perot interferometer through simulation, and includes:

[0067] Under the simulation condition, the atmospheric backwave signal corresponding to the double-frequency laser under the condition of the performance parameters of the Rayleigh wind lidar detection is obtained.

[0068] Based on the atmospheric backwave signal, the signal intensity I E，i in the energy detection channel of the double-frequency laser is obtained; and based on the atmospheric backwave signal and the transmittance function of the Fabry-Perot interferometer, the signal intensity I R，i after passing through the Fabry-Perot interferometer is obtained.

[0069] Based on the signal intensity I E，i and the signal intensity I R，i , a response function lookup table is obtained.

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

[0071]

[0072] For example, the time-sharing emission of the double-frequency laser into the atmosphere means that the laser emits two different frequency lasers into the atmosphere according to a predetermined pulse repetition frequency. For example, a laser with a center wavelength of 355 nm sends laser beams with frequencies v1 and v2 into the atmosphere according to a pulse repetition frequency of 60 Hz, and the double-frequency laser is time-shared and alternately input into the Fabry-Perot interferometer channel. After the double-frequency laser interacts with atmospheric molecules and the like in the atmosphere, it is received by a receiving telescope and enters a frequency discrimination system. The signal entering the frequency discrimination system includes atmospheric molecular backscattering spectrum f R,i ; the atmospheric backwave signal I i entering the frequency discrimination system, i=1,2.

[0073] Further, the atmospheric backwave signal corresponding to the double-frequency laser under the condition of the performance parameters of the Rayleigh wind lidar detection under the simulation condition includes:

[0074] The atmospheric backwave signal received by the Rayleigh wind lidar telescope between the vertical height z~z+Δz is obtained as follows:

[0075]

[0076] wherein: m is the number of pulse accumulations; G(z) is the geometric overlap factor of the lidar; η0is the total transmittance of the transmitting and receiving optical units; η is the quantum efficiency of the detector; E0is the transmitted laser pulse energy; λ L is the emitted laser wavelength; h = 6.626 x 10 -34 J is the Planck constant; c = 3 x 10 8 m / s is the speed of light; A0is the receiving area of the receiving telescope; z is the vertical height; Δz is the vertical range 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, and α R is the aerosol extinction coefficient.

[0077] The atmospheric backwave signal entering the frequency discrimination system is expanded by the expansion mirror and is split by the beam splitter. A small part of the signal is introduced into the energy detection channel, and the remaining signal is introduced into the Fabry-Perot interferometer channel through the beam splitter.

[0078] The signal intensity I E，i in the energy detection channel of the dual-frequency laser based on the atmospheric backwave signal is obtained; the signal intensity I R，i after the Fabry-Perot interferometer based on the atmospheric backwave signal and the transmittance function of the Fabry-Perot interferometer is obtained, and the expressions of the signal intensity I E，i , the signal intensity I R，i and the signal intensity I E,i are as follows:

[0079] I i (2)

[0080] I R,i = a1I i T R,i (3)

[0081] wherein a1and a2are calibration constants, which are the transmittance calibration constant and the reflectance calibration constant of the beam splitter, respectively, wherein f R,i (v) is the Rayleigh scattering broadened spectrum under the action of the dual-frequency laser; h is the transmittance function of the Fabry-Perot interferometer; denotes convolution, wherein i = 1, 2, and v is the frequency of the echo signal, wherein Figure 2 is a graph of the convolution of the corresponding Rayleigh scattering broadened spectrum under the action of the dual-frequency laser with the transmittance function of the Fabry-Perot interferometer at the frequency v1and the frequency v2.

[0082] like Figure 3 As shown in the figure, when there is no Doppler 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 in a positive direction, the intensity of the atmospheric echo signal at the laser frequency v1 received after passing through the Fabry-Perot interferometer increases, while the intensity of the atmospheric echo signal at the laser frequency v2 decreases; similarly, when the frequency of the atmospheric echo signal moves in a negative direction, the intensity of the atmospheric echo signal at the laser frequency v1 received after passing through the Fabry-Perot interferometer decreases, while the intensity of the atmospheric echo signal at the laser frequency v2 increases. Combined with the above theory, according to the signal intensity 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 is the transmittance of the Fabry-Perot interferometer corresponding to the laser with a frequency of v1, T R,2 is the transmittance of the Fabry-Perot interferometer corresponding to the laser with a frequency of v2, where Figure 4 is the response function of the Doppler frequency shift corresponding to the dual-frequency laser with frequencies v1 and v2.

[0089]

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

[0091] Combining formulas (4), (5) and (6) to simplify:

[0092]

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

[0094] According to formula (1), the signal intensity I E，i of the two frequency lasers in the energy detection channel can be obtained by substituting the simulated large atmospheric echo signal into formula (2), and the signal intensity I R，i after passing through the Fabry-Perot interferometer can be obtained by formula (3), based on the performance parameters of the Rayleigh wind detection laser radar and the frequency values corresponding to the dual-frequency lasers, the response function curve diagram corresponding to the Doppler frequency shift amount and temperature is obtained as shown in Figure 5 .

[0095] In the actual measurement process, the response function measured by the laser radar experiment is substituted into the frequency response function curve diagram obtained in the theoretical case for comparison, and the corresponding frequency shift amount can be found. As shown in Figure 5 , the response function curve in the theoretical case is directly compared with the response function curve in the actual case, assuming that the actual obtained response function is (1.34, 0.43), and the temperature is found to be about 210K in the two-dimensional lookup table, that is, the Doppler frequency shift amount is-0.242GHz.

[0096] Further, due to the effect of atmospheric wind or the movement of atmospheric particles, there is a Doppler frequency shift between the received light frequency and the transmitted laser, and the radial wind speed V r can be directly obtained by using the Doppler frequency measured by the optical spectrum analysis laser radar system according to the following formula:

[0097]

[0098] As Figure 6 shown in another embodiment of the present application, a frequency discrimination system of a Rayleigh wind lidar is also disclosed, which comprises a transmitting unit, a receiving unit and a data processing unit 26.

[0099] The transmitting unit is used to transmit two frequency lasers to the atmosphere in time division;

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

[0101] The first beam splitter 23 is used to guide the received atmospheric backscatter 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 lidar as described in any one of the above embodiments.

[0103] Specifically, the laser 10 transmits two frequency lasers to the atmosphere in time division, and the backscattering signal is received by the receiving telescope 20 after interacting with atmospheric molecules. The signal is transmitted to the beam expander 22 through the first optical fiber and the first collimator 21, and is emitted onto the first beam splitter 23 after being expanded by the beam expander 22. The first beam splitter 23 sends a small part of the backscattering signal to the energy detection channel, and the remaining signal is guided 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 work through the output signal.

[0104] Further, the frequency discrimination system further comprises a frequency locking unit, the frequency discrimination system further comprises a frequency locking unit, the frequency locking unit comprises a second optical fiber, both ends of the second optical fiber are connected to the transmitting unit and the receiving unit respectively, specifically, both ends of the second optical fiber are connected to the laser 10 and the first collimator 21 respectively, and the frequency of the dual-frequency laser transmitted by the transmitting unit in time division is locked on the first preset value and the second preset value, and the first preset value and the second preset value are symmetric about the center frequency of the Fabry-Perot interferometer 241, and the dual-frequency laser is input into the Fabry-Perot interferometer channel in time division alternately, 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 comprises Fabry-Perot interferometer 241, first filter 242, first focusing lens 243 and first photomultiplier tube 244 arranged in sequence, and the first photomultiplier tube 244 is connected with the data processing unit 26.

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

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

[0108] After the first beam splitter 23 directs the backscattering signal into the energy detection channel, the second filter 251 filters, and then the second photomultiplier tube 253 collects after focusing by the second focusing lens 252, and the second photomultiplier tube 253 is connected with the data processing unit 26.

[0109] Further, the transmitting unit further comprises second collimator 11, second beam splitter 12, energy monitoring module 13 and frequency monitoring module 14 arranged in sequence in the optical path, the second beam splitter 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 with the data processing unit 26.

[0110] Specifically, the laser 10 passes a small part of the emitted laser through the second collimator 11 into the second beam splitter 12 through the third optical fiber, and the second beam splitter 12 splits the beam, one beam enters the energy monitoring module 13, and the other beam enters the frequency monitoring module 14, and the energy monitoring module 13 and the frequency monitoring module 14 are connected with the data processing unit 26 to transmit the energy and frequency of the entering 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 with the laser 10, and the signal of the monitoring module is acquired by processing to control the energy and frequency of the laser beam of the laser 10.

[0112] In another embodiment of the present application, a computer device is also disclosed, which comprises a processor and a storage medium, and the storage medium has a computer program stored thereon. The processor reads and runs the computer program from the storage medium to execute the frequency discrimination method of the Rayleigh wind lidar according to any one of the above embodiments.

[0113] Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some of the technical features can be replaced by equivalents, and these modifications or replacements 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 application.

Claims

1. A frequency discrimination method for a 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; Directing the atmospheric echo signal 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 Fabry-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 the 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 the Rayleigh wind laser radar according to claim 2, characterized in that: Obtaining the Doppler frequency shift amount by the signal intensity of the dual-frequency laser after passing 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 lidar, the frequency value of the dual-frequency laser, and the transmittance function of the Fabry-Perot interferometer; The response function is calculated 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; The Doppler frequency shift amount is obtained by searching the response function lookup table using the response function.

4. The frequency discrimination method of the Rayleigh wind laser radar according to claim 3, characterized in that: The simulation method obtains a response function lookup table based on the performance parameters detected by the Rayleigh wind lidar, the frequency value of the dual-frequency laser, and the transmittance function of the Fabry-Perot interferometer, including: Under simulation conditions, obtaining an atmospheric echo signal corresponding to the dual-frequency laser under the performance parameter conditions of Rayleigh wind lidar detection; The signal intensity 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 intensity 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 the Rayleigh wind laser radar according to claim 4, characterized in that: The step of obtaining, under simulation conditions, an atmospheric echo signal corresponding to the dual-frequency laser under the performance parameter conditions of Rayleigh wind lidar detection includes: The atmospheric echo signal received by the Rayleigh wind lidar telescope between 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 the Rayleigh wind laser radar according to claim 5, characterized in that: The signal intensity 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 intensity I after passing through the Fabry-Perot interferometer is obtained R，i ,include: The signal intensity 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 intensity 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 Rayleigh scattering broadening spectrum 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 spectroscope is used to guide 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 according to any one of claims 1 to 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. 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 includes a Fabry-Perot interferometer, a first filter, a first focusing lens, and a first photomultiplier tube 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 spectrometer, an energy monitoring module and a frequency monitoring module. The second spectrometer 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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