Dual-telescope atmospheric turbulence lidar detection system and inversion method

Abstract

The dual-telescope atmospheric turbulence lidar detection system disclosed in the present invention includes a pulse laser, a collimation and beam expansion system, a spectroscopic system, and a photoelectric conversion system arranged along the optical path, and the above systems are respectively connected to a power supply and a data processing system. The inversion method for detecting atmospheric turbulence intensity of the present invention includes: 1. Selecting a laser incident path according to the environmental conditions of the detection site; 2. Selecting a corresponding inversion algorithm according to the laser incident path selected in step 1; 3. Calculating the turbulence intensity through the inversion algorithm. The inversion method of the present invention solves the problems in the prior art that the detection of atmospheric turbulence requires a complex combination of equipment, is greatly affected by uncontrollable factors, is not convenient for real-time detection, and has low spatial resolution.

Description

Technical Field

[0001] The invention relates to the technical field of laser active remote sensing detection, and in particular to a dual-telescope atmospheric turbulence laser radar detection system. The invention also relates to an inversion method for atmospheric turbulence intensity using the system. Background Art

[0002] Atmospheric turbulence can cause the refractive index of a light beam to fluctuate during transmission in the atmosphere, which in turn causes random changes in the amplitude and phase of the light wave, and further produces macroscopic phenomena such as light intensity fluctuations, phase fluctuations, beam drift, and beam expansion. This increases the difficulty of research in the field of atmospheric optics, and will especially affect the accuracy of lidar detection, astronomical observation accuracy, and the efficiency of free-space optical communications.

[0003] As a technology for actively detecting turbulent areas in the atmosphere, the dual-telescope atmospheric turbulence lidar relies on the backscattering amplification effect when the light beam is transmitted in atmospheric turbulence. In essence, when the laser passes through atmospheric turbulence, due to the mutual coherence effect when the light beam passes through the same random medium in the forward and backward directions, the strictly axial backscattering radiation intensity will be greater than the non-axial backscattering intensity. Therefore, during detection, the intensity of atmospheric turbulence in the area where the light beam passes can be inverted by the ratio of the on-axis and off-axis echo signals received by the dual telescopes.

[0004] The existing atmospheric turbulence optical detection technologies mainly include atmospheric turbulence optical passive detection technology and atmospheric turbulence optical active detection technology. The present invention belongs to optical active detection technology, which has the advantages of simple equipment, high controllable factors, strong real-time detection and high spatial resolution. Other detection technologies have complex equipment, are greatly affected by uncontrollable factors, and are not convenient for real-time detection. Summary of the invention

[0005] The purpose of the present invention is to provide a dual-telescope atmospheric turbulence lidar detection system, which solves the problems in the prior art that atmospheric turbulence detection requires a complex equipment combination, is greatly affected by uncontrollable factors, is not convenient for real-time detection and has low spatial resolution.

[0006] Another object of the present invention is to provide an inversion method for detecting atmospheric turbulence intensity using the above-mentioned dual-telescope atmospheric turbulence lidar detection system.

[0007] The technical solution adopted by the present invention is a dual-telescope atmospheric turbulence lidar detection system, including a pulse laser 1, a variable-magnification beam expander 2, a spectroscopic system and a photoelectric conversion system arranged in sequence along the optical path. The pulse laser 1 and the photoelectric conversion system are connected to a data processing system 19, and the photoelectric conversion system is also connected to a power supply 18.

[0008] The present invention is also characterized in that

[0009] The spectroscopic system includes a one-way lens 3 and a 50:50 spectroscope 4 arranged along the emitting direction of the laser light path, and a coaxial narrowband filter 5 and an off-axis narrowband filter 6 arranged in parallel on the echo light beam path. The coaxial narrowband filter 5 also has a coaxial converging convex lens 8 and a coaxial aperture diaphragm 9 arranged in sequence along the echo light beam direction, and the off-axis narrowband filter 6 also has an off-axis converging convex lens 7 and an off-axis aperture diaphragm 10 arranged in sequence along the echo light beam direction.

[0010] The photoelectric conversion system includes an off-axis photoelectric conversion system 11 arranged behind the optical path of the off-axis aperture stop 10 and a coaxial photoelectric conversion system 15 arranged behind the optical path of the coaxial aperture stop 9 .

[0011] The off-axis photoelectric conversion system 11 is composed of an off-axis photoelectric conversion system amplifier circuit and an off-axis photomultiplier tube.

[0012] The coaxial photoelectric conversion system 15 is composed of a coaxial photoelectric conversion system amplifier circuit and a coaxial photomultiplier tube.

[0013] Another technical solution adopted by the present invention is that the inversion method of the laser radar system detecting the atmospheric turbulence intensity comprises the following steps:

[0014] Step 1: Select the laser incident path according to the environmental conditions of the detection site;

[0015] Step 2: Select a corresponding inversion algorithm according to the laser incident path selected in step 1;

[0016] Step 3: Calculate the turbulence intensity through the inversion algorithm.

[0017] In step 1, the specific method for selecting the laser incident path is: determine whether there is a hard target behind the atmospheric turbulence to be measured in the field environment. When there is a hard target, the laser irradiates the hard target; when there is no hard target, the laser directly irradiates the turbulent area that may exist in the atmosphere to be measured.

[0018] The calculation method in step 3 is:

[0019] Calculation method when there is a hard target behind the laser irradiation atmospheric turbulence:

[0020] Step 3.1 According to the generalized Huygens-Fresnel principle of light beam propagation in atmospheric turbulence and the mutual interference principle of the forward path and backward path of laser propagation in atmospheric turbulence, the light intensity at the telescope receiving point is obtained as: I(p)

[0021] p represents the distance between the on-axis and off-axis. When p = 0, I(p) represents the on-axis light intensity; when p → ∞, I(p) represents the off-axis light intensity. Therefore, the backscattering amplification factor can be defined as:

[0022]

[0023] in:

[0024]

[0025]

[0026]

[0027] Where w0 represents the beam radius, represents the variance of the Gaussian process due to the characteristics of the beam expander, ρ0 represents the atmospheric coherence length in turbulence, k represents the wave number in rad / m, and a r represents the size of the light beam incident on the target, L represents the distance from the light source to the target, σ x represents the logarithmic amplitude variance of the spherical wave;

[0028] Step 3.2 The received power of the coaxial photoelectric conversion system is:

[0029]

[0030] Where P1 is the actual hard target reflected power, P BG1 is the coaxial background noise power, P PMT1 is the noise power generated by the coaxial photomultiplier tube (PMT);

[0031] The received power of the off-axis photoelectric conversion system is:

[0032]

[0033] Where P2 is the actual hard target reflected power, P BG2 is the off-axis background noise power, P PMT2 is the noise power generated by the off-axis photomultiplier tube (PMT);

[0034] By recording the background light P of the current environment BG1 and P BG2 The background noise power, and P under no light conditions PMT1 and P PMT2 The noise power of , thus obtaining the actual echo signal power:

[0035]

[0036]

[0037] Because a 50:50 beam splitter with a splitting ratio of 50:50 is used at the coaxial position, the PMT will attenuate the hard target reflected echo signal by half, so the actual coaxial power should be 2P1. The backscattering amplification factor is obtained by comparing the above coaxial and off-axis powers:

[0038]

[0039] Step 3.3: Combine equation (1) and equation (9), that is,

[0040]

[0041] Substituting equations (1), (2), (3), (4), (7), (8), and (9) into equation (10) yields the refractive index structure constant used to represent the average intensity of atmospheric turbulence on the detection path:

[0042] Step 3.4: If the hard target 23 moves along the beam path, the turbulence intensity profile along the beam path within the moving interval can be obtained as follows:

[0043] According to step 3.3, the hard target can be found to be at position x n The average turbulence intensity at and position x n-1 The average turbulence intensity at When x n and x n-1 When the relative position is very close, x can be obtained n and x n-1 The average turbulence intensity between the two periods can be considered as x n The turbulence intensity at

[0044]

[0045] Step 3.5: The hard target 23 is slowly and uniformly moved along the beam path to obtain positions x1, x2, ..., x1 evenly spaced along the beam path. n , repeat step 3.4 to get the moving paths x1, x2, ..., x n Upper turbulence intensity profile.

[0046] Calculation method when there is no hard target behind the laser irradiating the target atmospheric turbulence:

[0047] Step 3.1 According to the principle of aerosol backscattering lidar, the system receives backscattered light generated by particles at a distance L, which is coaxial after photoelectric conversion. and off-axis The power is expressed as:

[0048]

[0049]

[0050] Where P0 is the single pulse energy of the laser beam, O(L) is the overlap factor of the laser radar system, c is the speed of light, τ is the width of the laser pulse, and A is R is the receiving area of ​​the telescope, β(L) is the backscattering coefficient of the particle cluster at distance z, σ(L) represents the atmospheric extinction coefficient, and S(p) represents the atmospheric turbulence factor;

[0051] Step 3.2 The received power of the coaxial photoelectric conversion system is:

[0052]

[0053] Where P1(L) is the actual atmospheric backscatter power, P BG1 is the coaxial background noise power, P PMT1 is the noise power generated by the coaxial photomultiplier tube;

[0054] The received power of the off-axis photoelectric conversion system is:

[0055]

[0056] Where P2(L) is the actual atmospheric backscatter power, P BG2 is the off-axis background noise power, P PMT2 is the noise power generated by the off-axis photomultiplier tube;

[0057] By recording the background light P of the current environment BG1 and P BG2 The background noise power, and P under no light conditions PMT1 and P PMT2 The noise power of , thus obtaining the actual echo signal power:

[0058]

[0059]

[0060] Step 3.3: Because a 50:50 beam splitter with a splitting ratio of 50:50 is used at the coaxial position, the atmospheric backscatter echo signal will be attenuated by half, so the actual coaxial power should be 2P1(L). The backscatter amplification factor is obtained by comparing the above coaxial and off-axis powers:

[0061]

[0062] Where P1(L) and P2(L) are the actual powers of the light beam backscattered by the aerosol along the propagation path. This power is composed of the backscattered signals of each aerosol particle on the propagation path.

[0063] P1(L)=P1(L1)+P1(L2)+…+P1(L N ) (19)

[0064] P2(L)=P2(L1)+P2(L2)+…+P2(L N ) (20)

[0065] Where L is the transmission path length, L1, L2, ..., L N are the positions on each path respectively, that is, the actual backscattering power on the path is differentiated, and then equations (19) and (20) are substituted into equation (18) to obtain the turbulence intensity profile K(L) used to represent the turbulence intensity of the light beam on the detection path as the detection path length L changes. K(L) is a function on the detection path L. When there is no turbulence in the atmosphere, the backscattering amplification coefficient K(L) is always 1. If there is turbulence in the atmosphere, the backscattering amplification coefficient is greater than 1. The larger the coefficient, the greater the turbulence intensity.

[0066] The dual-telescope atmospheric turbulence lidar detection system proposed in the present invention can realize remote sensing detection of turbulent areas in the atmosphere, and can directly invert the intensity of the turbulent areas detected in the atmosphere without the need for other parallel detection equipment, and can calibrate the intensity parameters of the turbulent areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 It is a schematic diagram of the structure of the radar detection system of the present invention (when the laser irradiates a hard target);

[0068] Figure 2 is a schematic diagram of the structure of the radar detection system of the present invention (when the laser irradiates the atmospheric turbulence);

[0069] Figure 3 It is an inversion flow chart of the radar detection system of the present invention for detecting the atmospheric turbulence intensity.

[0070] In the figure, 1. pulse laser, 2. variable magnification beam expander, 3. one-way lens, 4. 50:50 beam splitter, 5. coaxial narrowband filter, 6. off-axis narrowband filter, 7. off-axis converging convex lens, 8. coaxial converging convex lens, 9. coaxial aperture diaphragm, 10. off-axis aperture diaphragm, 11. off-axis photoelectric conversion system, 12. off-axis signal output cable, 13. off-axis photomultiplier tube power supply cable, 14. off-axis amplifier circuit power supply cable, 15. coaxial photoelectric conversion system, 16. coaxial photomultiplier tube power supply cable, 17. coaxial amplifier circuit power supply cable, 18. power supply, 19. data processing system, 20. coaxial signal output cable, 21. laser control cable, 22. atmospheric turbulence, 23. movable hard target. DETAILED DESCRIPTION

[0071] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0072] The dual-telescope atmospheric turbulence laser radar system of the present invention has a structure as follows: Figure 1 and Figure 2 As shown, it includes a pulse laser 1 connected in sequence, with an output wavelength of 532nm, a pulse energy of 10uJ to 50uJ, a pulse width of 12ns to 25ns, a pulse repetition frequency of 1kHz to 10kHz, a beam diameter of 3mm, a divergence angle of 4mrad, and a variable-magnification beam expander 2 to control the output spot diameter at 40mm. After passing through a one-way lens 3, it reaches a 50:50 beam splitter 4 with a splitting ratio of 50:50. The beam splitter has a diameter of 76.2mm, and the acute angles of the incident and output beams are both 45°. The axial wavelengths of the coaxial narrowband filter 5 and the off-axis narrowband filter 6 are 532nm, the bandwidth is 20nm, and the diameters are both 25.4mm. The off-axis converging convex lens 7 The diameters of the coaxial converging convex lens 8 and the coaxial converging convex lens 8 are both 40 mm, and the focal lengths are both 160 mm. The diameters of the light holes of the coaxial aperture diaphragm 9 and the off-axis aperture diaphragm 10 are both 0.8 mm. The coaxial aperture diaphragm 9 is located behind the optical path of the coaxial converging convex lens 8, and the off-axis aperture diaphragm 10 is located behind the optical path of the off-axis converging convex lens 7. The off-axis photoelectric conversion system 11 collects the echo signals converged by the off-axis converging convex lens 7, and the coaxial photoelectric conversion system 15 collects the echo signals converged by the coaxial converging convex lens 8.

[0073] The power supply 18 supplies power to the amplifier circuit in the off-axis photomultiplier tube power supply cable 13, and the power supply 18 also supplies power to the photomultiplier tube in the off-axis photoelectric conversion system 11 through the off-axis amplifier circuit power supply cable 14. The off-axis photoelectric conversion system 11 transmits the echo signal to the data processing system platform 19 through the off-axis signal output cable 12; the power supply 18 supplies power to the amplifier circuit in the coaxial photomultiplier tube power supply cable 16, and the power supply 18 supplies power to the photomultiplier tube in the coaxial photoelectric conversion system 15 through the coaxial amplifier circuit power supply cable 17. The coaxial photoelectric conversion system 15 transmits the echo signal to the data processing system 19 through the coaxial signal output cable 20; the data processing system 19 also controls the pulse laser 1 through the laser control cable 21; the data processing system 19 processes the echo signals received from the coaxial photoelectric conversion system 15 and the off-axis photoelectric conversion system 11.

[0074] The inversion method of the laser radar system for detecting the atmospheric turbulence intensity of the present invention comprises the following steps:

[0075] Step 1: Select the laser incident path according to the environmental conditions of the detection site;

[0076] Step 2: Select a corresponding inversion algorithm according to the laser incident path selected in step 1;

[0077] Step 3: Calculate the turbulence intensity through the inversion algorithm.

[0078] The specific method for selecting the laser incident path is: in the field environment, judging whether there is a hard target behind the atmospheric turbulence area to be measured.

[0079] The detection process of laser entering the atmosphere and reaching the hard target is as follows:

[0080] The wavelength of the laser emitted by the pulse laser 1 is 532nm, the pulse energy is 10uJ to 50uJ, the pulse width is 12ns to 25ns, the pulse repetition frequency is 1kHz to 10kHz, the beam diameter is 3mm, and the divergence angle is 4mrad. After the laser beam is expanded by the variable-magnification beam expander 2, a laser beam with a beam diameter of 40mm and a divergence angle of 2mrad is formed. After being reflected by the one-way lens 3 and the 50:50 beam splitter 4 with a splitting ratio of 50:50 in sequence, it is emitted to the atmospheric turbulence 22 and reaches the movable hard target 23. The reflected light beam of the movable hard target 23 passes through the coaxial narrowband filter 5, is converged by the coaxial converging convex lens 8, and then passes through the coaxial aperture diaphragm 9 to the coaxial photoelectric conversion system 15. The reflected light beam of the movable hard target 23 passes through the off-axis narrowband filter 6, is converged by the off-axis converging convex lens 7, and then passes through the off-axis aperture diaphragm 10. to the off-axis photoelectric conversion system 11; the power supply 18 provides high voltage to the photomultiplier tube of the coaxial photoelectric conversion system 15 through the coaxial photomultiplier tube power supply cable 16, the power supply 18 provides voltage to the amplifier circuit of the coaxial photoelectric conversion system 15 through the coaxial amplifier circuit power supply cable 17, the power supply 18 provides high voltage to the photomultiplier tube of the off-axis photoelectric conversion system 11 through the off-axis photomultiplier tube power supply cable 13, and the power supply 18 provides voltage to the amplifier circuit of the off-axis photoelectric conversion system 11 through the off-axis amplifier circuit power supply cable 14; the data processing system 19 obtains coaxial echo signal data through the coaxial signal output cable 12, and the data processing system 19 obtains off-axis echo signal data through the off-axis signal output cable 20.

[0081] The detection process of laser directly incident on the atmosphere is:

[0082] The wavelength of the laser emitted by the pulse laser 1 is 532nm, the pulse energy is 10uJ to 50uJ, the pulse width is 12ns to 25ns, the pulse repetition frequency is 1kHz to 10kHz, the beam diameter is 3mm, and the divergence angle is 4mrad. After the laser beam is expanded by the variable magnification beam expander 2, a laser beam with a beam diameter of 40mm and a divergence angle of 2mrad is formed. After being reflected by the one-way lens 3 and the 50:50 beam splitter 4 with a splitting ratio of 50:50, it is emitted to the atmospheric turbulence 22. The backscattered light passes through the coaxial narrowband filter 5 and is converged by the coaxial converging convex lens 8, and then passes through the coaxial aperture diaphragm 9 to the coaxial photoelectric conversion system 15. The atmospheric backscattered light passes through the off-axis narrowband filter 6 and is converged by the off-axis converging convex lens 7, and then passes through the off-axis aperture diaphragm 10 to the off-axis photoelectric conversion system 11. The power supply 18 provides high voltage to the photomultiplier tube in the coaxial photoelectric conversion system 15 through the coaxial photomultiplier tube power supply cable 16. The power supply 18 provides voltage to the amplifier circuit in the coaxial photoelectric conversion system 15 through the coaxial amplifier circuit power supply cable 17. The power supply 18 provides high voltage to the photomultiplier tube in the off-axis photoelectric conversion system 11 through the off-axis photomultiplier tube power supply cable 13. The power supply 18 provides voltage to the amplifier circuit in the off-axis photoelectric conversion system 11 through the off-axis amplifier circuit power supply cable 14. The data processing system 19 obtains coaxial echo signal data through the coaxial signal output cable 20, and the data processing system 19 obtains off-axis echo signal data through the off-axis signal output cable 12.

[0083] The data processing system 19 not only needs to complete the analog-to-digital conversion of the parallel signals of the two channels, but also needs to implement the inversion algorithm for the atmospheric turbulence lidar detection system.

[0084] The inversion algorithm used in the above detection process is:

[0085] Calculation method when there is a hard target behind the laser irradiation atmospheric turbulence:

[0086] Step 3.1 According to the generalized Huygens-Fresnel principle of light beam propagation in atmospheric turbulence and the mutual interference principle of the forward path and backward path of laser propagation in atmospheric turbulence, the light intensity at the telescope receiving point is obtained as: I(p)

[0087] p represents the distance between the on-axis and off-axis. When p = 0, I(p) represents the on-axis light intensity; when p → ∞, I(p) represents the off-axis light intensity. Therefore, the backscattering amplification factor can be defined as:

[0088]

[0089] in:

[0090]

[0091]

[0092]

[0093] Where w0 represents the beam radius, represents the variance of the Gaussian process due to the characteristics of the beam expander, ρ0 represents the atmospheric coherence length in turbulence, k represents the wave number in rad / m, and a r represents the size of the light beam incident on the target, L represents the distance from the light source to the target, σ x represents the logarithmic amplitude variance of the spherical wave;

[0094] Step 3.2 The received power of the coaxial photoelectric conversion system is:

[0095]

[0096] Where P1 is the actual hard target reflected power, P BG1 is the coaxial background noise power, P PMT1 is the noise power generated by the coaxial photomultiplier tube (PMT);

[0097] The received power of the off-axis photoelectric conversion system is:

[0098]

[0099] Where P2 is the actual hard target reflected power, P BG2 is the off-axis background noise power, P PMT2 is the noise power generated by the off-axis photomultiplier tube (PMT);

[0100] By recording the background light P of the current environment BG1 and P BG2 The background noise power, and P under no light conditions PMT1 and P PMT2 The noise power of , thus obtaining the actual echo signal power:

[0101]

[0102]

[0103] Because a 50:50 beam splitter with a splitting ratio of 50:50 is used at the coaxial position, the PMT will attenuate the hard target reflected echo signal by half, so the actual coaxial power should be 2P1. The backscattering amplification factor is obtained by comparing the above coaxial and off-axis powers:

[0104]

[0105] Step 3.3: Combine equation (1) and equation (9), that is,

[0106]

[0107] Substituting equations (1), (2), (3), (4), (7), (8), and (9) into equation (10) yields the refractive index structure constant used to represent the average intensity of atmospheric turbulence on the detection path:

[0108] Step 3.4: If the hard target 23 moves along the beam path, the turbulence intensity profile along the beam path within the moving interval can be obtained as follows:

[0109] According to step 3.3, the hard target can be found to be at position x n The average turbulence intensity at and position x n-1 The average turbulence intensity at When x n and x n-1 When the relative position is very close, x can be obtained n and x n-1 The average turbulence intensity between the two periods can be considered as x n The turbulence intensity at

[0110]

[0111] Step 3.5: The hard target 23 is slowly and uniformly moved along the beam path to obtain positions x1, x2, ..., x1 evenly spaced along the beam path. n , repeat step 3.4 to get the moving paths x1, x2, ..., x n Upper turbulence intensity profile.

[0112] Calculation method when there is no hard target behind the laser irradiating the target atmospheric turbulence:

[0113] Step 3.1 According to the principle of aerosol backscattering lidar, the system receives backscattered light generated by particles at a distance L, which is coaxial after photoelectric conversion. and off-axis The power is expressed as:

[0114]

[0115]

[0116] Where P0 is the single pulse energy of the laser beam, O(L) is the overlap factor of the laser radar system, c is the speed of light, τ is the width of the laser pulse, and A is Ris the receiving area of ​​the telescope, β(L) is the backscattering coefficient of the particle cluster at distance z, σ(L) represents the atmospheric extinction coefficient, and S(p) represents the atmospheric turbulence factor;

[0117] Step 3.2 The received power of the coaxial photoelectric conversion system is:

[0118]

[0119] Where P1(L) is the actual atmospheric backscatter power, P BG1 is the coaxial background noise power, P PMT1 is the noise power generated by the coaxial photomultiplier tube;

[0120] The received power of the off-axis photoelectric conversion system is:

[0121]

[0122] Where P2(L) is the actual atmospheric backscatter power, P BG2 is the off-axis background noise power, P PMT2 is the noise power generated by the off-axis photomultiplier tube;

[0123] By recording the background light P of the current environment BG1 and P BG2 The background noise power, and P under no light conditions PMT1 and P PMT2 The noise power of , thus obtaining the actual echo signal power:

[0124]

[0125]

[0126] Step 3.3: Because a 50:50 beam splitter with a splitting ratio of 50:50 is used at the coaxial position, the atmospheric backscatter echo signal will be attenuated by half, so the actual coaxial power should be 2P1(L). The backscatter amplification factor is obtained by comparing the above coaxial and off-axis powers:

[0127]

[0128] Where P1(L) and P2(L) are the actual powers of the light beam backscattered by the aerosol along the propagation path. This power is composed of the backscattered signals of each aerosol particle on the propagation path.

[0129] P1(L)=P1(L1)+P1(L2)+…+P1(L N ) (19)

[0130] P2(L)=P2(L1)+P2(L2)+…+P2(LN ) (20)

[0131] Where L is the transmission path length, L1, L2, ..., L N are the positions on each path respectively, that is, the actual backscattering power on the path is differentiated, and then equations (19) and (20) are substituted into equation (18) to obtain the turbulence intensity profile K(L) used to represent the turbulence intensity of the light beam on the detection path as the detection path length L changes. K(L) is a function on the detection path L. When there is no turbulence in the atmosphere, the backscattering amplification coefficient K(L) is always 1. If there is turbulence in the atmosphere, the backscattering amplification coefficient is greater than 1. The larger the coefficient, the greater the turbulence intensity.

Claims

1. Dual-telescope atmospheric turbulence lidar detection system, characterized in that: A pulse laser (1), a variable-magnification beam expander (2), a spectroscopic system and a photoelectric conversion system are sequentially arranged along an optical path. The pulse laser (1) and the photoelectric conversion system are connected to a data processing system (19). The photoelectric conversion system is also connected to a power supply (18). The data processing system (19) runs a turbulence detection inversion algorithm. The turbulence detection inversion algorithm comprises the following steps: Step 1: Select the laser incident path according to the environmental conditions of the detection site; Step 2: Select a corresponding inversion algorithm according to the laser incident path selected in step 1; Step 3: Calculate the turbulence intensity by the following steps: Calculation method when there is a hard target behind the laser irradiation atmospheric turbulence: Step 3.1 According to the generalized Huygens-Fresnel principle of light beam propagation in atmospheric turbulence and the mutual interference principle of the forward path and the backward path of laser propagation in atmospheric turbulence, the light intensity at the receiving point of the telescope is obtained as: I(p); p represents the distance between the on-axis and off-axis. When p = 0, I(p) represents the on-axis light intensity; when p → ∞, I(p) represents the off-axis light intensity. Therefore, the backscattering amplification factor can be defined as: in: Where w0 represents the beam radius, represents the variance of the Gaussian process due to the characteristics of the beam expander, ρ0 represents the atmospheric coherence length in turbulence, k represents the wave number in rad / m, and a r represents the size of the light beam incident on the target, L represents the distance from the light source to the target, σ x represents the logarithmic amplitude variance of the spherical wave; Step 3.2 The received power of the coaxial photoelectric conversion system is: Where P1 is the actual hard target reflected power, P BG1 is the coaxial background noise power, P PMT1 is the noise power generated by the coaxial photomultiplier tube PMT; The received power of the off-axis photoelectric conversion system is: Where P2 is the actual hard target reflected power, P BG2 is the off-axis background noise power, P PMT2 is the noise power generated by the off-axis photomultiplier tube PMT; By recording the background light P of the current environment BG1 and P BG2 The background noise power, and P under no light conditions PMT1 and P PMT2 The noise power of , thus obtaining the actual echo signal power: Because a 50:50 beam splitter with a splitting ratio of 50:50 is used at the coaxial position, the PMT receives the hard target reflected echo signal which will be attenuated by half. Therefore, the actual coaxial power should be 2P1. The backscattering amplification factor is obtained by comparing the above coaxial and off-axis powers: Step 3.3: Combine equation (1) and equation (9), namely: Substituting equations (1), (2), (3), (4), (7), (8), and (9) into equation (10) yields the refractive index structure constant used to represent the average intensity of atmospheric turbulence on the detection path: Step 3.4: If the hard target 23 moves along the beam path, the turbulence intensity profile along the beam path within the moving interval can be obtained as follows: According to step 3.3, the hard target can be found to be at position x n The average turbulence intensity at and position x n-1 The average turbulence intensity at When x n and x n-1 When the relative position is very close, x can be obtained n and x n-1 The average turbulence intensity between the two periods can be considered as x n The turbulence intensity at is: Step 3.5: The hard target 23 is slowly and uniformly moved along the beam path to obtain positions x1, x2, ..., x1 evenly spaced along the beam path. n , repeat step 3.4 to get the moving paths x1, x2, ..., x n Upper turbulence intensity profile; Calculation method when there is no hard target behind the laser irradiating the target atmospheric turbulence: Step 3.1 According to the principle of aerosol backscattering lidar, the system receives backscattered light generated by particles at a distance L, which is coaxial after photoelectric conversion. and off-axis The power is expressed as: Where P0 is the single pulse energy of the laser beam, O(L) is the overlap factor of the laser radar system, c is the speed of light, τ is the width of the laser pulse, and A is R is the receiving area of ​​the telescope, β(L) is the backscattering coefficient of the particle cluster at distance z, σ(L) represents the atmospheric extinction coefficient, and S(p) represents the atmospheric turbulence factor; Step 3.2 The received power of the coaxial photoelectric conversion system is: Where P1(L) is the actual atmospheric backscatter power, P BG1 is the coaxial background noise power, P PMT1 is the noise power generated by the coaxial photomultiplier tube; The received power of the off-axis photoelectric conversion system is: Where P2(L) is the actual atmospheric backscatter power, P BG2 is the off-axis background noise power, P PMT2 is the noise power generated by the off-axis photomultiplier tube; By recording the background light P of the current environment BG1 and P BG2 The background noise power, and P under no light conditions PMT1 and P PMT2 The noise power of , thus obtaining the actual echo signal power: Step 3.3: Because a 50:50 beam splitter with a splitting ratio of 50:50 is used at the coaxial position, the atmospheric backscatter echo signal will be attenuated by half, so the actual coaxial power should be 2P1(L). The backscatter amplification factor is obtained by comparing the above coaxial and off-axis powers: Where P1(L) and P2(L) are the actual powers of the light beam backscattered by aerosol along the propagation path. This power is composed of the backscattered signals of each aerosol particle on the propagation path, and is: P1(L)=P1(L1)+P1(L2)+···+P1(L N ) (19) <h2 style=";text-align:left;direction:ltr">P2(L) = P2(L1) + P2(L2) + ···+P2(L<h2 style=";text-align:left;direction:ltr"> N <h2 style=";text-align:left;direction:ltr"> (20) Where L is the transmission path length, L1, L2, ···, L N are the positions on each path respectively, that is, the actual backscattering power on the path is differentiated, and then equations (19) and (20) are substituted into equation (18) to obtain the turbulence intensity profile K(L) used to represent the turbulence intensity of the light beam on the detection path as the detection path length L changes. K(L) is a function on the detection path L. When there is no turbulence in the atmosphere, the backscattering amplification coefficient K(L) is always 1. If there is turbulence in the atmosphere, the backscattering amplification coefficient is greater than 1. The larger the coefficient, the greater the turbulence intensity.

2. The dual-telescope atmospheric turbulence lidar detection system according to claim 1, characterized in that: In the step 1, the specific method for selecting the laser incident path is: determine whether there is a hard target behind the atmospheric turbulence to be measured in the field environment. When there is a hard target, the laser irradiates the hard target; when there is no hard target, the laser directly irradiates the atmospheric turbulence to be measured.

3. The dual-telescope atmospheric turbulence lidar detection system according to claim 1, characterized in that: The optical splitting system comprises a one-way lens (3) arranged along the exit direction of the laser light path, a 50:50 beam splitter (4), and a coaxial narrowband filter (5) and an off-axis narrowband filter (6) arranged in parallel on the echo light path; the coaxial narrowband filter (5) is also provided with a coaxial convergent convex lens (8) and a coaxial aperture diaphragm (9) arranged in sequence along the echo light path; and the off-axis narrowband filter (6) is also provided with an off-axis convergent convex lens (7) and an off-axis aperture diaphragm (10) arranged in sequence along the echo light path.

4. The dual-telescope atmospheric turbulence lidar detection system according to claim 3, characterized in that: The diameter of the 50:50 beam splitter (4) is 76.2 mm, the axial wavelength of the coaxial narrowband filter (5) and the off-axis narrowband filter (6) are both 532 nm, the bandwidth is 20 nm, and the diameter is 25.4 mm. The diameter of the off-axis converging convex lens (7) and the coaxial converging convex lens (8) are both 40 mm, and the focal length is 160 mm. The diameter of the light hole of the coaxial aperture diaphragm (9) and the off-axis aperture diaphragm (10) is both 0.8 mm.

5. The dual-telescope atmospheric turbulence lidar detection system according to claim 1, characterized in that: The photoelectric conversion system comprises an off-axis photoelectric conversion system (11) arranged behind the optical path of the off-axis aperture stop (10) and a coaxial photoelectric conversion system (15) arranged behind the optical path of the coaxial aperture stop (9).

6. The dual-telescope atmospheric turbulence lidar detection system according to claim 5, characterized in that: The off-axis photoelectric conversion system (11) is composed of an off-axis photoelectric conversion system amplifier circuit and an off-axis photomultiplier tube.

7. The dual-telescope atmospheric turbulence lidar detection system according to claim 5, characterized in that: The coaxial photoelectric conversion system (15) is composed of a coaxial photoelectric conversion system amplifier circuit and a coaxial photomultiplier tube.

8. The dual-telescope atmospheric turbulence lidar detection system according to claim 1, characterized in that: The pulse laser (1) is a pulse laser, the emitted laser wavelength is 532nm, the pulse energy is 10uJ to 50uJ, the pulse width is 12ns to 25ns, the pulse repetition frequency is 1kHz to 10kHz, the beam diameter is 3mm, the divergence angle is 4mrad, and the spot diameter output after passing through the variable magnification beam expander (2) is 40mm.

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