A non-coherent wind laser radar and atmospheric wind speed measurement method

Abstract

The present invention provides a non-coherent wind laser radar and an atmospheric wind speed measurement method, wherein a pulsed linear polarized light is generated by a transmitting system, and the pulsed linear polarized light is emitted to the atmosphere after being adjusted in polarization state by an optical processing system, and the echo signal reflected by the atmospheric molecules is received and processed; the optical processing system divides the echo signal into two paths, one path is detected by a first photodetector after being processed by a metastable barium atom discriminator, and the other path is detected by a second photodetector; the metastable barium atom discriminator discriminates the signal using the resonance absorption characteristics of barium atoms, and the data acquisition and processing system collects the signal intensity calculation ratio of the first photodetector and the second photodetector, and calculates the Doppler frequency shift and inverts the atmospheric wind speed according to the corresponding relationship between the signal intensity ratio and the Doppler frequency shift. In this scheme, a metastable barium atom discriminator is used to filter the aerosol interference part in the atmospheric echo signal, so as to solve the problem that the atmospheric wind field detection is easily interfered by aerosols, thereby realizing accurate detection of the atmospheric wind speed.

Description

Technical Field

[0001] The invention relates to the technical field of laser remote sensing, and in particular to an incoherent wind measurement laser radar and an atmospheric wind speed measurement method. Background Art

[0002] The use of LiDAR technology for atmospheric wind speed detection is an advanced optical active remote sensing technology with the remarkable characteristics of high temporal and spatial resolution and large detection range. The laser is emitted by a laser source, and then is collimated by the emission system and emitted to the atmosphere. After being attenuated by the atmosphere, it is scattered by particles in the atmosphere. Atmospheric backscattering includes Mie scattering, Rayleigh scattering, Raman scattering, etc. The atmospheric backscattered laser is extinguished again by the atmosphere on the way back, and then received by the receiving optical system. Through the photoelectric detector and the collection and counting system, the echo signal is finally processed to obtain the measured wind speed information.

[0003] In the prior art, due to the low aerosol content in the middle and upper atmosphere, coherent laser radar cannot measure the wind speed in the middle and upper atmosphere. Therefore, an incoherent wind laser radar based on atmospheric molecular scattering is used to measure the wind speed in the middle and upper atmosphere. In the optical receiving system of the incoherent wind laser radar, an optical discriminator is required to obtain the frequency shift of the outgoing laser due to the Doppler effect, thereby obtaining the wind speed result. The discriminators currently used mainly include Fabry-Perot etalons and iodine absorption cells. The incoherent wind laser radar using the above discriminator, in the low troposphere region (2-5km) where the top of the boundary layer transitions to the free space atmosphere, on the one hand, is disturbed by the aerosol scattering signal, and there are problems such as distortion of the discriminator curve and large error of the frequency response function; on the other hand, since the aerosol concentration varies greatly during the day with the boundary layer height, thermal convection, wind shear, etc., the above errors are difficult to eliminate through system calibration. Summary of the invention

[0004] In view of this, an embodiment of the present invention provides a non-coherent wind measurement lidar and an atmospheric wind speed measurement method to solve the problem that the detection of the atmospheric wind field in the lower troposphere is susceptible to aerosol interference, thereby achieving the purpose of accurately detecting the atmospheric wind speed in the lower troposphere region where the top of the boundary layer transitions to the free space atmosphere.

[0005] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0006] The first aspect of the embodiment of the present invention discloses an incoherent wind laser radar, which includes: a transmitting system, a light processing system, a first photodetector, a second photodetector, a metastable barium atom frequency discriminator and a data acquisition and processing system;

[0007] The transmitting system is used to generate pulsed linearly polarized light;

[0008] The optical processing system is used to process the pulsed linearly polarized light to obtain an outgoing laser pointing in the direction of atmospheric detection; adjust the polarization state of the received first atmospheric echo signal to obtain a second atmospheric echo signal; and perform branching processing on the second atmospheric echo signal to obtain a third atmospheric echo signal and a target signal;

[0009] The metastable barium atom frequency discriminator is used to perform frequency discriminator processing on the third atmosphere echo signal to obtain a fourth atmosphere echo signal;

[0010] The data acquisition and processing system is used to collect the signal strength of the fourth atmospheric echo signal through the first photoelectric detector to obtain a first signal strength value; collect the signal strength of the target signal through the second photoelectric detector to obtain a second signal strength value; calculate a target ratio between the first signal strength value and the second signal strength value; obtain a target Doppler frequency shift corresponding to the target ratio based on a correspondence between the signal strength ratio and the Doppler frequency shift obtained in advance by experiments; and obtain the atmospheric wind speed based on inversion of the target Doppler frequency shift.

[0011] Preferably, the metastable barium atom frequency discriminator comprises: a pump laser, a vacuum pump, a barium atom pool and a heating control system;

[0012] The vacuum pump is connected to the barium atomic pool and is used to extract the air in the barium atomic pool so that the barium atomic pool does not contain oxygen;

[0013] The heating control system is used to heat the barium atomic pool that does not contain oxygen so that the barium atomic pool is maintained at a preset temperature;

[0014] The pump laser is used to emit pump laser into the barium atomic pool to excite the barium atoms in the barium atomic pool to a metastable state, so as to utilize the resonant absorption characteristics of the barium atoms transitioning between energy levels to absorb the signal of the target frequency in the third atmospheric echo signal, obtain a fourth atmospheric echo signal, and allow the fourth atmospheric echo signal to be emitted into the first photodetector; there is a corresponding relationship between the target frequency and the preset temperature, and there is a corresponding relationship between the absorption ratio of the signal of the target frequency in the third atmospheric echo signal and the preset temperature.

[0015] Preferably, the heating control system comprises: a stainless steel heating furnace and an insulating heating belt;

[0016] The insulating heating belt is wound around the stainless steel heating furnace, and is used to place the barium atomic pool that does not contain oxygen into the stainless steel heating furnace, and to heat the barium atomic pool by the insulating heating belt, so that the barium atomic pool is maintained at a preset temperature.

[0017] Preferably, the transmitting system comprises: a tunable pulse laser and a beam expander;

[0018] The tunable pulse laser is used to generate pulsed linear polarized light to be processed, and inject the pulsed linear polarized light to be processed into the beam expander;

[0019] The beam expander is used to perform beam expansion processing and divergence angle compression processing on the pulsed linear polarized light to be processed, so as to obtain pulsed linear polarized light and inject the pulsed linear polarized light into the light processing system.

[0020] Preferably, the light processing system comprises: a polarizing beam splitter prism, a quarter wave plate, a telescope system, a filter and a non-polarizing beam splitter prism;

[0021] The polarization beam splitter prism is used to filter out the S polarized light in the pulsed linear polarized light to obtain the pulsed linear polarized light containing only P polarized light, and inject the pulsed linear polarized light containing only P polarized light into the quarter wave plate; filter out the S polarized light in the second atmosphere echo signal injected by the quarter wave plate to obtain the second atmosphere echo signal containing only P polarized light, and inject the second atmosphere echo signal containing only P polarized light into the filter;

[0022] The quarter wave plate is used to adjust the polarization state of the pulsed linear polarized light containing only P polarized light to obtain an outgoing laser, and emit the outgoing laser into the telescope system; adjust the polarization state of the first atmospheric echo signal received by the telescope system to obtain a second atmospheric echo signal, and emit the second atmospheric echo signal into the polarization splitter prism;

[0023] The telescope system is used to point the outgoing laser to the direction of atmospheric detection; receive a first atmospheric echo signal generated by atmospheric molecules reflecting the outgoing laser; and emit the first atmospheric echo signal into the quarter-wave plate;

[0024] The optical filter is used to filter out the background light signal in the second atmospheric echo signal containing only P-polarized light, obtain the interference-free second atmospheric echo signal, and emit the interference-free second atmospheric echo signal into the non-polarized beam splitter prism;

[0025] The non-polarization beam splitter prism is used to split the interference-free second atmosphere echo signal into a third atmosphere echo signal and a target signal; inject the third atmosphere echo signal into the metastable barium atom frequency discriminator; and inject the target signal into the second photoelectric detector.

[0026] Preferably, the non-polarizing beam splitter prism is specifically used for:

[0027] 80% of the interference-free second atmosphere echo signal is divided into a third atmosphere echo signal, and 20% of the interference-free second atmosphere echo signal is divided into a target signal; the third atmosphere echo signal is injected into the metastable barium atom discriminator; and the target signal is injected into the second photodetector.

[0028] Preferably, it further comprises: a first coupling lens;

[0029] The first coupling lens is disposed between the metastable barium atom frequency discriminator and the first photodetector, and is used for performing coupling processing on the fourth atmosphere echo signal, and injecting the coupled fourth atmosphere echo signal into the first photodetector.

[0030] Preferably, it further comprises: a second coupling lens;

[0031] The second coupling lens is disposed between the light processing system and the second photodetector, and is used to perform coupling processing on the target signal, and emit the coupled target signal into the second photodetector.

[0032] Preferably, the wavelength of the pulsed linearly polarized light is 354.8 nm.

[0033] A second aspect of an embodiment of the present invention discloses an atmospheric wind speed measurement method, which is applied to any incoherent wind measurement laser radar disclosed in the first aspect of an embodiment of the present invention, and the method comprises:

[0034] generating pulsed linearly polarized light using a transmitting system;

[0035] The pulsed linearly polarized light is processed by an optical processing system to obtain an outgoing laser pointing in the direction of atmospheric detection; the polarization state of the received first atmospheric echo signal is adjusted to obtain a second atmospheric echo signal, and the second atmospheric echo signal is split to obtain a third atmospheric echo signal and a target signal;

[0036] Performing frequency discrimination processing on the third atmosphere echo signal by using a metastable barium atom frequency discriminator to obtain a fourth atmosphere echo signal;

[0037] The data acquisition and processing system collects the signal strength of the fourth atmospheric echo signal through a first photoelectric detector to obtain a first signal strength value, collects the signal strength of the target signal through a second photoelectric detector to obtain a second signal strength value, calculates a target ratio between the first signal strength value and the second signal strength value, obtains a target Doppler frequency shift corresponding to the target ratio based on a correspondence between the signal strength ratio and the Doppler frequency shift obtained in advance experiments, and obtains the atmospheric wind speed based on the inversion of the target Doppler frequency shift.

[0038] Based on the above-mentioned embodiment of the present invention, a non-coherent wind measurement laser radar and an atmospheric wind speed measurement method are provided, the non-coherent wind measurement laser radar includes: a transmitting system, a light processing system, a first photodetector, a second photodetector, a metastable barium atom discriminator and a data acquisition and processing system; the transmitting system is used to generate pulsed linearly polarized light; the light processing system is used to process the pulsed linearly polarized light to obtain an outgoing laser pointing in the direction of atmospheric detection; the polarization state of the received first atmospheric echo signal is adjusted to obtain a second atmospheric echo signal; the second atmospheric echo signal is branched to obtain a third atmospheric echo signal and a target signal; the metastable The barium atom frequency discriminator is used to perform frequency discriminator processing on the third atmospheric echo signal to obtain a fourth atmospheric echo signal; the data acquisition and processing system is used to collect the signal strength of the fourth atmospheric echo signal through the first photoelectric detector to obtain a first signal strength value; collect the signal strength of the target signal through the second photoelectric detector to obtain a second signal strength value; calculate the target ratio between the first signal strength value and the second signal strength value; obtain the target Doppler frequency shift corresponding to the target ratio based on the correspondence between the signal strength ratio and the Doppler frequency shift obtained in advance by experiments; and obtain the atmospheric wind speed by inverting the target Doppler frequency shift. In this scheme, a metastable barium atom frequency discriminator that pumps barium atoms from the ground state to the metastable state to generate resonant transition absorption is used as an optical frequency discriminator to filter the aerosol interference part in the atmospheric echo signal, solve the problem that the detection of the atmospheric wind field in the lower troposphere is susceptible to aerosol interference, and thus realize accurate detection of the atmospheric wind speed in the lower troposphere region where the boundary layer top transitions to the free space atmosphere. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0040] Figure 1 An optical path diagram of an incoherent wind measurement laser radar disclosed in an embodiment of the present invention;

[0041] Figure 2 A schematic diagram of a transmittance function and Rayleigh-Brillouin scattering spectrum of a metastable barium atom discriminator disclosed in an embodiment of the present invention;

[0042] Figure 3 A flow chart of an atmospheric wind speed measurement method disclosed in an embodiment of the present invention;

[0043] Among them, 1 is a tunable pulse laser, 2 is a beam expander, 3 is a polarization beam splitter, 4 is a quarter wave plate, 5 is a reflector, 6 is a telescope, 7 is a first photodetector, 8 is a first coupling lens, 9 is a barium atomic pool heating system, 10 is a filter, 11 is a non-polarization beam splitter, 12 is a data acquisition and processing system, 13 is a pump laser, 14 is a second photodetector, and 15 is a second coupling lens. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0045] In this application, the terms "comprises", "comprising" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element.

[0046] As can be seen from the background technology, when measuring atmospheric wind speed, the existing incoherent wind laser radar is easily interfered by aerosol scattering signals, has problems such as distortion of the discrimination curve and large error of the frequency response function, and is difficult to calibrate.

[0047] Therefore, an embodiment of the present invention discloses an incoherent wind measurement lidar and an atmospheric wind speed measurement method. In this scheme, a metastable barium atom discriminator that pumps barium atoms from the ground state to the metastable state to produce resonant transition absorption is used as an optical discriminator to filter out the aerosol interference portion of the atmospheric echo signal, thereby solving the problem that the detection of the atmospheric wind field in the lower troposphere is susceptible to aerosol interference, thereby achieving accurate detection of the atmospheric wind speed in the lower troposphere region where the top of the boundary layer transitions to the free space atmosphere.

[0048] like Figure 1 , which is a light path diagram of an incoherent wind measurement laser radar disclosed in an embodiment of the present invention.

[0049] Among them, the incoherent wind measurement laser radar includes: a transmitting system, a light processing system, a first photodetector 7, a second photodetector 14, a metastable barium atom discriminator and a data acquisition and processing system 12, and the data acquisition and processing system 12 is communicatively connected to the first photodetector 7 and the second photodetector 14.

[0050] The transmitting system is used for generating pulsed linearly polarized light and transmitting the pulsed linearly polarized light into the light processing system.

[0051] Specifically, the transmitting system includes: a tunable pulse laser 1 and a beam expander 2.

[0052] The tunable pulse laser 1 is used for generating pulsed linear polarized light to be processed and injecting the pulsed linear polarized light to be processed into the beam expander 2.

[0053] The beam expander 2 is used to expand the pulsed linear polarized light to be processed and to compress the divergence angle to obtain the pulsed linear polarized light and inject the pulsed linear polarized light into the light processing system.

[0054] The optical processing system is used to adjust the polarization state of pulsed linear polarized light to obtain an outgoing laser; point the outgoing laser to the direction of atmospheric detection; receive a first atmospheric echo signal generated by atmospheric molecules reflecting the outgoing laser, and adjust the polarization state of the first atmospheric echo signal to obtain a second atmospheric echo signal; perform branching processing on the second atmospheric echo signal to obtain a third atmospheric echo signal and a target signal; inject the third atmospheric echo signal into a metastable barium atom discriminator; and inject the target signal into a second photodetector 14.

[0055] It should be noted that the first atmospheric echo signal reflected by the 2-5km atmosphere contains interference signals formed by aerosols or thin clouds. Atmospheric molecules refer to gas molecules, while aerosols refer to a gaseous dispersion system composed of solid or liquid particles suspended in a gas medium.

[0056] Specifically, the light processing system includes: a polarization beam splitter prism 3 , a quarter wave plate 4 , a telescope system, a filter 10 and a non-polarization beam splitter prism 11 .

[0057] The polarization beam splitter prism 3 is used for filtering out the S polarized light in the pulse linear polarized light to obtain the pulse linear polarized light containing only the P polarized light, and injecting the pulse linear polarized light containing only the P polarized light into the quarter wave plate 4.

[0058] It should be noted that the polarization beam splitting prism 3 only allows P-polarized light to pass through, and S-polarized light is reflected on the beam splitting surface.

[0059] The quarter wave plate 4 is used to adjust the polarization state of the pulsed linear polarized light containing only P polarized light to obtain output laser light, and emit the output laser light into the telescope system.

[0060] Adjusting the polarization state includes: converting linearly polarized light into circularly polarized light, or converting circularly polarized light into linearly polarized light.

[0061] The telescopic system includes a reflector 5 and a telescope 6 .

[0062] The reflector 5 is used to reflect the outgoing laser to the telescope 6 and reflect the first atmospheric echo signal emitted by the telescope 6 to the quarter-wave plate 4.

[0063] The telescope 6 is used to direct the outgoing laser to the direction of atmospheric detection, receive the first atmospheric echo signal generated by the atmospheric molecules reflecting the outgoing laser, and emit the first atmospheric echo signal into the reflecting mirror 5.

[0064] It can be understood that the reflector 5 is only used to convert the direction of light and does not process the light itself.

[0065] It should be noted that the atmospheric molecules in the atmosphere at 2 to 5 km reflect the outgoing laser to form a first atmospheric echo signal, which is then collected by the telescope 6 and then emitted into the reflector 5 .

[0066] Correspondingly, the quarter wave plate 4 is used to adjust the polarization state of the first atmospheric echo signal to obtain the second atmospheric echo signal, and emit the second atmospheric echo signal into the polarization beam splitter prism 3 .

[0067] The polarization beam splitter prism 3 filters out the S polarized light in the second atmosphere echo signal to obtain a second atmosphere echo signal containing only P polarized light, and injects the second atmosphere echo signal containing only P polarized light into the filter 10 .

[0068] The filter 10 is used to filter out the background light signal in the second atmosphere echo signal containing only P-polarized light, obtain the interference-free second atmosphere echo signal, and emit the interference-free second atmosphere echo signal into the non-polarization beam splitter prism 11 .

[0069] It should be noted that the function of the filter 10 is to selectively transmit or block light within a specific wavelength range, and at the same time reflect or absorb light of other wavelengths.

[0070] The non-polarization beam splitter prism 11 is used to split the interference-free second atmosphere echo signal into a third atmosphere echo signal and a target signal, inject the third atmosphere echo signal into the metastable barium atom frequency discriminator, and inject the target signal into the second photodetector 14 .

[0071] Preferably, a non-polarization beam splitter prism 11 with a beam splitting ratio of 4 to 1 is used, so that 80% of the light enters the metastable barium atom discriminator and 20% of the light enters the second photodetector 14 .

[0072] Accordingly, the non-polarization beam splitter prism 11 is specifically used for:

[0073] 80% of the interference-free second atmosphere echo signal is divided into the third atmosphere echo signal, and 20% of the interference-free second atmosphere echo signal is divided into the target signal; the third atmosphere echo signal is injected into the metastable barium atom discriminator; and the target signal is injected into the second photodetector 14.

[0074] It can be understood that 20% of the second atmosphere echo signal is sufficient for the second photodetector 14 to detect, and injecting as much of the second atmosphere echo signal as possible into the metastable barium atom frequency discriminator helps to improve the accuracy of the measurement.

[0075] The metastable barium atom frequency discriminator is used to utilize the resonance absorption characteristics of barium atoms transitioning between energy levels to perform frequency discriminator processing on the third atmosphere echo signal to obtain a fourth atmosphere echo signal, and emit the fourth atmosphere echo signal into the first photodetector 7.

[0076] It should be noted that the metastable barium atomic frequency discriminator is an optical frequency discriminator (also known as an atomic filter), which uses the resonance frequency of atoms to selectively filter out signals of specific frequencies. It is widely used in laser non-invasive diagnosis and detection of gas, liquid spray and plasma, filtering of Rayleigh scattering, Raman scattering and Thompson scattering, and as a core component of high spectral resolution lidar (HSRL). By analyzing the hyperfine structure and sixth-order kinetic model of metastable barium atoms, a method for calculating the composition of metastable barium atoms can be established. State to The theoretical model of the absorption line characteristics of the state transition at 354.8nm is given, and its changing characteristics with the temperature, length, pump light intensity and particle number density of the steam pool are given.

[0077] It should also be noted that the barium atoms need to be pumped from the ground state to the metastable state to produce Resonant transition absorption forms a metastable barium atom discriminator to filter out the aerosol interference part in the atmospheric echo signal in the lower troposphere.

[0078] like Figure 2 , which is a schematic diagram of a transmittance function and Rayleigh-Brillouin scattering spectrum of a metastable barium atom discriminator disclosed in an embodiment of the present invention.

[0079] The horizontal axis (X-axis): marked as "Frequency (GHz)", represents the frequency in gigahertz (GHz).

[0080] Vertical axis (Y axis): marked as "transmission or intensity", indicating transmittance or signal intensity.

[0081] Figure 2 Three different curves are shown in Figure 1:

[0082] Ba Filter Function (FF): represents the transmittance function of the barium atomic discriminator, which is related to the heating temperature of the barium atomic pool in the metastable barium atomic discriminator and shows the transmittance of the discriminator to light of different frequencies.

[0083] Rayleigh-Brillouin Spectrum(RBS): stands for Rayleigh-Brillouin scattering spectrum, which shows the frequency distribution of Rayleigh scattering and Brillouin scattering in the atmosphere.

[0084] RBS×FF: filled area, representing the convolution result of the Rayleigh-Brillouin scattering spectrum and the barium atom discriminator filter function, showing the signal intensity distribution after the discriminator processing.

[0085] In an embodiment of the present invention, in order to ensure the accuracy of the calculated Doppler frequency shift, it is necessary to measure the actual absorption spectrum of the metastable barium atomic discriminator to the atmospheric echo signal in advance through experiments (the temperature of the barium atomic pool is kept at a preset temperature during the experiment), and then the actual absorption spectrum is convolved with the Rayleigh-Brillouin scattering spectrum of the atmospheric echo signal to obtain the atmospheric echo signal after passing through the metastable barium atomic discriminator. According to the convolution result, the signal intensity ratio between the atmospheric echo signal after passing through the metastable barium atomic discriminator and the atmospheric echo signal without passing through the metastable barium atomic discriminator at different Doppler frequency shifts can be calculated, thereby obtaining the corresponding relationship between the signal intensity ratio and the Doppler frequency shift, and the Doppler frequency shift is subsequently calculated using the corresponding relationship.

[0086] It should be noted that through convolution, a function can be obtained that describes how the signal strength after being processed by the metastable barium atomic discriminator changes with the Doppler shift. This function reveals the quantitative relationship between the change in signal strength (i.e., the change between the signal strength after the discriminator and the signal strength without the discriminator) and the Doppler shift in the atmosphere. This relationship is determined by comparing the ratio of the actual signal strength to the signal strength without the metastable barium discriminator. This ratio is directly related to the Doppler shift because the Doppler shift affects the efficiency of the metastable barium atomic discriminator to absorb light.

[0087] Specifically, the metastable barium atom frequency discriminator includes: a pump laser 13 and a barium atom pool heating system 9 .

[0088] The barium atomic pool heating system 9 includes: a barium atomic pool and a heating control system.

[0089] The heating control system is used for heating the barium atomic pool which does not contain oxygen, so that the barium atomic pool is kept at a preset temperature.

[0090] It should be noted that the preset temperature is consistent with the preset temperature in the process of obtaining the corresponding relationship between the signal intensity ratio and the Doppler frequency shift in the above experiment.

[0091] Preferably, the heating control system comprises: a stainless steel heating furnace and an insulating heating belt.

[0092] The insulating heating tape is wound around the stainless steel heating furnace, and is used to place the oxygen-free barium atomic pool into the stainless steel heating furnace and heat the barium atomic pool using the insulating heating tape, so that the barium atomic pool is maintained at a preset temperature.

[0093] Preferably, the metastable barium atom frequency discriminator further comprises:

[0094] The vacuum pump connected to the barium atomic cell is used to extract the air in the barium atomic cell so that the barium atomic cell does not contain oxygen.

[0095] The pump laser 13 is used to inject pump laser into the barium atomic pool to excite the barium atoms in the barium atomic pool to a metastable state, so as to utilize the resonant absorption characteristics of the barium atoms transitioning between energy levels to absorb the signal of the target frequency in the third atmospheric echo signal, obtain the fourth atmospheric echo signal, and make the fourth atmospheric echo signal enter the first photodetector 7.

[0096] There is a corresponding relationship between the target frequency and the preset temperature, and there is a corresponding relationship between the absorption ratio of the signal of the target frequency in the third atmospheric echo signal and the preset temperature.

[0097] Preferably, the wavelength of the pump laser is 791 nm.

[0098] It should be noted that the pump laser 13 injects pump laser into the barium atom pool to excite the barium atoms in the barium atom pool to a metastable state to generate Resonant transition absorption forms a metastable barium atom discriminator to filter out the aerosol part of the atmospheric echo signal in the lower troposphere.

[0099] The first photoelectric detector 7 is used to detect the signal strength of the fourth atmosphere echo signal.

[0100] Preferably, before the fourth atmospheric echo signal is emitted into the first photodetector 7, it needs to pass through a first coupling lens 8 arranged between the metastable barium atom discriminator and the first photodetector 7, which is used to couple the fourth atmospheric echo signal and emit the coupled fourth atmospheric echo signal into the first photodetector 7.

[0101] The second photoelectric detector 14 is used to detect the signal strength of the target signal.

[0102] Preferably, before the target signal is emitted into the second photodetector 14 , it needs to pass through a second coupling lens 15 disposed between the non-polarizing beam splitter prism 11 and the second photodetector 14 to couple the target signal and emit the coupled target signal into the second photodetector 14 .

[0103] The data acquisition and processing system 12 is used to acquire the signal strength of the fourth atmospheric echo signal to obtain a first signal strength value; acquire the signal strength of the target signal to obtain a second signal strength value; calculate a target ratio between the first signal strength value and the second signal strength value; based on the corresponding relationship between the signal strength ratio and the Doppler frequency shift and the target ratio, obtain a target Doppler frequency shift corresponding to the target ratio; the corresponding relationship is obtained by conducting experiments on a metastable barium atomic discriminator in advance; and the atmospheric wind speed is obtained by inverting the target Doppler frequency shift.

[0104] Specifically, the target signal has not passed through the metastable barium atom discriminator, and its intensity is recorded as the first signal intensity value I 0 When the atmospheric wind speed is not zero, due to the generation of Doppler frequency shift, the center frequency of the atmospheric echo signal is offset relative to the center frequency of the metastable barium atom discriminator, and the intensity of the atmospheric echo signal changes. The signal intensity at this time is recorded as the second signal intensity value I 1 Because the beam splitting ratio of the non-polarization beam splitter 11 is constant (and consistent with the beam splitting ratio used in the process of obtaining the corresponding relationship between the signal intensity ratio and the Doppler frequency shift in the experiment), the first signal intensity value I 0 and the second signal strength value I 1 The Doppler frequency shift can be calculated by the ratio of the signal strength ratio and the corresponding relationship between the signal strength ratio and the Doppler frequency shift obtained in the above experiment, and the atmospheric wind speed can be inverted.

[0105] Based on the incoherent wind measurement lidar disclosed in the above-mentioned embodiment of the present invention, in this scheme, a metastable barium atom discriminator that pumps barium atoms from the ground state to the metastable state to produce resonant transition absorption is used as an optical discriminator to filter out the aerosol interference part in the atmospheric echo signal, thereby solving the problem that the detection of the atmospheric wind field in the lower troposphere is susceptible to aerosol interference, thereby realizing the atmospheric wind speed detection in the lower troposphere area where the top of the boundary layer transitions to the free space atmosphere.

[0106] Based on the above-mentioned embodiment of the present invention, a non-coherent wind measurement laser radar is disclosed, such as Figure 3 FIG. 1 is a flow chart of an atmospheric wind speed measurement method disclosed in an embodiment of the present invention. The method is applied to any of the incoherent wind measurement laser radars disclosed in the above-mentioned embodiments of the present invention, and includes the following steps:

[0107] Step S301: Generate pulsed linearly polarized light using a transmitting system, and inject the pulsed linearly polarized light into a light processing system.

[0108] In step S301 , the wavelength of the pulsed linearly polarized light is 354.8 nm.

[0109] Step S302: the optical processing system adjusts the polarization state of the pulsed linear polarized light to obtain an outgoing laser, and directs the outgoing laser to the direction of atmospheric detection, receives a first atmospheric echo signal generated by the atmospheric molecules reflecting the outgoing laser, adjusts the polarization state of the first atmospheric echo signal to obtain a second atmospheric echo signal, performs branching processing on the second atmospheric echo signal to obtain a third atmospheric echo signal and a target signal, injects the third atmospheric echo signal into a metastable barium atom discriminator, and injects the target signal into a second photodetector.

[0110] In step S302, polarization state adjustment includes: filtering out S polarized light and retaining P polarized light.

[0111] The branching process specifically branches the second atmospheric echo signal according to a beam splitting ratio of 4 to 1 to obtain a third atmospheric echo signal and a target signal.

[0112] Step S303: The metastable barium atom frequency discriminator performs frequency discriminator processing on the third atmosphere echo signal by utilizing the resonance absorption characteristic of the transition of barium atoms between energy levels to obtain a fourth atmosphere echo signal, and emits the fourth atmosphere echo signal into the first photodetector.

[0113] In step S303, the metastable barium atom discriminator pumps the metastable barium atoms at a preset temperature to filter out the aerosol interference part in the atmospheric echo signal in the lower troposphere region.

[0114] Step S304: the first photoelectric detector detects the signal strength of the fourth atmosphere echo signal.

[0115] Step S305: The second photodetector detects the signal strength of the target signal.

[0116] Step S306: The data acquisition and processing system acquires the signal strength of the fourth atmospheric echo signal to obtain a first signal strength value; acquires the signal strength of the target signal to obtain a second signal strength value, calculates a target ratio between the first signal strength value and the second signal strength value, obtains a target Doppler frequency shift corresponding to the target ratio based on the correspondence between the signal strength ratio and the Doppler frequency shift and the target ratio, and obtains the atmospheric wind speed based on the inversion of the target Doppler frequency shift.

[0117] The corresponding relationship between the signal intensity ratio and the Doppler frequency shift is obtained by conducting experiments on a metastable barium atom discriminator in advance.

[0118] In step S306, the specific calculation principle and explanation have been described in detail in the above embodiments of the present invention, and reference may be made to each other.

[0119] Based on the atmospheric wind speed measurement method disclosed in the above-mentioned embodiment of the present invention, in this scheme, a metastable barium atom discriminator that pumps barium atoms from the ground state to the metastable state to produce resonant transition absorption is used as an optical discriminator to filter out the aerosol interference part in the atmospheric echo signal, thereby solving the problem that the atmospheric wind field detection in the lower troposphere is susceptible to aerosol interference, thereby realizing the atmospheric wind speed detection in the lower troposphere region where the top of the boundary layer transitions to the free space atmosphere.

[0120] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can refer to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system or system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment. The system and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without creative work.

[0121] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0122] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An incoherent wind laser radar, characterized in that: The incoherent wind laser radar comprises: a transmitting system, a light processing system, a first photodetector, a second photodetector, a metastable barium atom frequency detector and a data acquisition and processing system; The transmitting system is used to generate pulsed linearly polarized light; The optical processing system is used to process the pulsed linearly polarized light to obtain an outgoing laser pointing in the direction of atmospheric detection; adjust the polarization state of the received first atmospheric echo signal to obtain a second atmospheric echo signal; and perform branching processing on the second atmospheric echo signal to obtain a third atmospheric echo signal and a target signal; The metastable barium atom frequency discriminator is used to perform frequency discriminator processing on the third atmosphere echo signal to obtain a fourth atmosphere echo signal; The data acquisition and processing system is used to collect the signal strength of the fourth atmospheric echo signal through the first photoelectric detector to obtain a first signal strength value; collect the signal strength of the target signal through the second photoelectric detector to obtain a second signal strength value; calculate a target ratio between the first signal strength value and the second signal strength value; obtain a target Doppler frequency shift corresponding to the target ratio based on a correspondence between the signal strength ratio and the Doppler frequency shift obtained in advance by experiments; and obtain the atmospheric wind speed based on inversion of the target Doppler frequency shift.

2. The incoherent wind laser radar according to claim 1, characterized in that: The metastable barium atom frequency discriminator comprises: a pump laser, a vacuum pump, a barium atom pool and a heating control system; The vacuum pump is connected to the barium atomic pool and is used to extract the air in the barium atomic pool so that the barium atomic pool does not contain oxygen; The heating control system is used to heat the barium atomic pool that does not contain oxygen so that the barium atomic pool is maintained at a preset temperature; The pump laser is used to emit pump laser into the barium atomic pool to excite the barium atoms in the barium atomic pool to a metastable state, so as to utilize the resonant absorption characteristics of the barium atoms transitioning between energy levels to absorb the signal of the target frequency in the third atmospheric echo signal, obtain a fourth atmospheric echo signal, and allow the fourth atmospheric echo signal to be emitted into the first photodetector; there is a corresponding relationship between the target frequency and the preset temperature, and there is a corresponding relationship between the absorption ratio of the signal of the target frequency in the third atmospheric echo signal and the preset temperature.

3. The incoherent wind laser radar according to claim 2, characterized in that: The heating control system comprises: a stainless steel heating furnace and an insulating heating belt; The insulating heating belt is wound around the stainless steel heating furnace, and is used to place the barium atomic pool that does not contain oxygen into the stainless steel heating furnace, and to heat the barium atomic pool by the insulating heating belt, so that the barium atomic pool is maintained at a preset temperature.

4. The incoherent wind laser radar according to claim 1, characterized in that: The transmitting system comprises: a tunable pulse laser and a beam expander; The tunable pulse laser is used to generate pulsed linear polarized light to be processed, and inject the pulsed linear polarized light to be processed into the beam expander; The beam expander is used to perform beam expansion processing and divergence angle compression processing on the pulsed linear polarized light to be processed, so as to obtain pulsed linear polarized light and inject the pulsed linear polarized light into the light processing system.

5. The incoherent wind laser radar according to claim 1, characterized in that: The light processing system includes: a polarization beam splitter prism, a quarter wave plate, a telescope system, a filter, and a non-polarization beam splitter prism; The polarization beam splitter prism is used to filter out the S polarized light in the pulsed linear polarized light to obtain the pulsed linear polarized light containing only P polarized light, and inject the pulsed linear polarized light containing only P polarized light into the quarter wave plate; filter out the S polarized light in the second atmosphere echo signal injected by the quarter wave plate to obtain the second atmosphere echo signal containing only P polarized light, and inject the second atmosphere echo signal containing only P polarized light into the filter; The quarter wave plate is used to adjust the polarization state of the pulsed linear polarized light containing only P polarized light to obtain an outgoing laser, and emit the outgoing laser into the telescope system; adjust the polarization state of the first atmospheric echo signal received by the telescope system to obtain a second atmospheric echo signal, and emit the second atmospheric echo signal into the polarization splitter prism; The telescope system is used to point the outgoing laser to the direction of atmospheric detection; receive a first atmospheric echo signal generated by atmospheric molecules reflecting the outgoing laser; and emit the first atmospheric echo signal into the quarter-wave plate; The optical filter is used to filter out the background light signal in the second atmospheric echo signal containing only P-polarized light, obtain the interference-free second atmospheric echo signal, and emit the interference-free second atmospheric echo signal into the non-polarized beam splitter prism; The non-polarization beam splitter prism is used to split the interference-free second atmosphere echo signal into a third atmosphere echo signal and a target signal; inject the third atmosphere echo signal into the metastable barium atom frequency discriminator; and inject the target signal into the second photoelectric detector.

6. The incoherent wind laser radar according to claim 5, characterized in that: The non-polarizing beam splitter prism is specifically used for: 80% of the interference-free second atmosphere echo signal is divided into a third atmosphere echo signal, and 20% of the interference-free second atmosphere echo signal is divided into a target signal; the third atmosphere echo signal is injected into the metastable barium atom discriminator; and the target signal is injected into the second photodetector.

7. The incoherent wind laser radar according to claim 1, characterized in that: Also includes: a first coupling lens; The first coupling lens is disposed between the metastable barium atom frequency discriminator and the first photodetector, and is used for performing coupling processing on the fourth atmosphere echo signal, and injecting the coupled fourth atmosphere echo signal into the first photodetector.

8. The incoherent wind laser radar according to claim 1, characterized in that: Also includes: A second coupling lens; The second coupling lens is disposed between the light processing system and the second photodetector, and is used to perform coupling processing on the target signal, and emit the coupled target signal into the second photodetector.

9. The incoherent wind laser radar according to any one of claims 1 to 8, characterized in that: The wavelength of the pulsed linearly polarized light is 354.8 nm.

10. A method for measuring atmospheric wind speed, characterized in that: The incoherent wind laser radar according to any one of claims 1 to 9 is applied, and the method comprises: generating pulsed linearly polarized light using a transmitting system; The pulsed linearly polarized light is processed by an optical processing system to obtain an outgoing laser pointing in the direction of atmospheric detection; the polarization state of the received first atmospheric echo signal is adjusted to obtain a second atmospheric echo signal, and the second atmospheric echo signal is split to obtain a third atmospheric echo signal and a target signal; Performing frequency discrimination processing on the third atmosphere echo signal by using a metastable barium atom frequency discriminator to obtain a fourth atmosphere echo signal; The data acquisition and processing system collects the signal strength of the fourth atmospheric echo signal through a first photoelectric detector to obtain a first signal strength value, collects the signal strength of the target signal through a second photoelectric detector to obtain a second signal strength value, calculates a target ratio between the first signal strength value and the second signal strength value, obtains a target Doppler frequency shift corresponding to the target ratio based on a correspondence between the signal strength ratio and the Doppler frequency shift obtained in advance experiments, and obtains the atmospheric wind speed based on the inversion of the target Doppler frequency shift.

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