Rayleigh temperature measurement laser radar metrological characteristic evaluation method based on Monte Carlo method

Abstract

The invention discloses a Rayleigh temperature measurement laser radar metrological characteristic evaluation method based on a Monte Carlo method. The method comprises the following steps: acquiring Rayleigh temperature measurement laser radar parameters; setting a target atmospheric density and temperature profile; calculating a Rayleigh backscattering coefficient and an atmosphere two-way transmittance; calculating a Rayleigh temperature measurement laser radar echo photon number by using a laser radar equation; utilizing a Monte Carlo method to generate an echo photon number random sample; inverting an atmospheric density profile sample by using the echo photon number sample; inverting an atmospheric temperature sample by using the atmospheric density profile sample and the reference temperature; and calculating the average deviation of the atmospheric temperature, the measurement uncertainty and other metrological characteristics. According to the method, the relationship among the Rayleigh laser radar parameters, the target temperature and the measured temperature is established, comprehensive evaluation of the Rayleigh temperature measurement laser radar metrological characteristics is realized through a Monte Carlo simulation test, and the method can be used for optimizing the design of a laser radar system.

Description

Technical Field

[0001] The invention belongs to the technical field of laser radar atmospheric detection and test measurement, and specifically is a method for evaluating the metrological characteristics of a Rayleigh temperature measurement laser radar based on a Monte Carlo method. Background Art

[0002] Rayleigh temperature lidar is the main remote sensing equipment for atmospheric detection. It consists of a laser transmitting system, an optical receiving system, a data acquisition and control system, a data analysis and processing system, etc. Its working principle is to utilize the Rayleigh scattering effect of the transmitted laser and atmospheric molecules, invert the atmospheric density profile by measuring the intensity of the Rayleigh scattering echo signal, and calculate the atmospheric temperature profile using the hydrostatic equilibrium and the ideal gas equation, thereby realizing the measurement of atmospheric density and temperature.

[0003] At present, Rayleigh temperature laser radar detection technology has developed relatively maturely at home and abroad, but the metrological characteristics evaluation of Rayleigh temperature laser radar is still imperfect. At altitudes below 30km, the atmospheric in-situ detection data can be used as a benchmark to obtain measurement deviations. It is difficult to obtain benchmark data above 30km. Photon noise is usually used to calculate the measurement uncertainty of temperature through the uncertainty propagation formula. This method does not introduce laser radar parameters and cannot fully evaluate the metrological characteristics of Rayleigh temperature laser radar. Summary of the invention

[0004] The present invention aims to provide an evaluation method for comprehensively evaluating the metrological characteristics of Rayleigh temperature measurement laser radar by introducing laser radar parameters, so as to solve the problems in the background technology.

[0005] To achieve the purpose of the present invention, the present invention provides a method for evaluating the metrological characteristics of a Rayleigh temperature measuring laser radar based on the Monte Carlo method, and the technical scheme adopted is as follows:

[0006] Step 1: Obtain the Rayleigh temperature measurement lidar parameters;

[0007] Step 2: Set the target atmospheric density and temperature profile;

[0008] Step 3: Calculate the Rayleigh backscattering coefficient and atmospheric two-way transmittance using the Rayleigh temperature laser radar parameters and the target atmospheric density;

[0009] Step 4: Calculate the number of echo photons of Rayleigh temperature measurement lidar using the lidar equation;

[0010] Step 5: Generate random samples of echo photon numbers using the Monte Carlo method according to the characteristics of the Poisson distribution of the number of received photons;

[0011] Step 6: Use the echo photon number samples to invert the atmospheric density profile samples;

[0012] Step 7: Invert the atmospheric temperature sample using the atmospheric density profile sample and the reference temperature;

[0013] Step 8: Calculate metrological characteristics such as mean deviation and measurement uncertainty of atmospheric temperature.

[0014] In one embodiment, the step 2 of setting the target atmospheric density and temperature profile is specifically as follows: generating a detection height column vector according to the lidar detection range and height resolution parameters, and using the atmospheric density and temperature of the 1976 U.S. standard atmosphere to obtain the target atmospheric profile by cubic spline interpolation to the detection height.

[0015] In one embodiment, the Rayleigh backscattering coefficient calculation method in step 3 is:

[0016]

[0017] β(λ, z) = n A (z)σ(λ,z)

[0018] The calculation method of atmospheric two-way transmittance in step 3 is:

[0019]

[0020]

[0021] Among them, σ(z, λ) is the Rayleigh signal backscattering cross section, λ is the laser wavelength, β(λ,z) ​​is the Rayleigh signal backscattering coefficient, and n A (z) is the number density of atmospheric molecules, α(λ,z) ​​is the atmospheric extinction coefficient, T 2 (z, λ) is the atmospheric two-way transmittance.

[0022] In one embodiment, the method for calculating the number of echo photons in step 4 is:

[0023]

[0024] Among them, N R (λ, z) is the number of echo photons received within the range of z-Δz / 2 to z+Δz / 2, z is the height, P L (λ) is the average power of the emitted laser, Δt is the integration time, h is Planck's constant, c is the speed of light, λ is the laser wavelength, β(λ, z) is the Rayleigh signal backscattering coefficient, α(λ, z) is the atmospheric extinction coefficient, T 2 (z, λ) is the atmospheric two-way transmittance, Δz is the distance resolution, A is the receiving telescope area, and η is the system efficiency.

[0025] In one embodiment, in step 5, the random sample of echo photon numbers obeys the expected Poisson distribution of the echo photon numbers obtained in step 4, and the random sample of echo photon numbers is an m×n-order matrix, where m is the length of the detection height column vector and n is the number of Monte Carlo simulation experiments.

[0026] In one embodiment, the atmospheric density inversion method in step 6 is:

[0027]

[0028] Among them, n A (z) and n A (z0) are the atmospheric densities at z and z0 respectively; z0 is the reference height of atmospheric Rayleigh scattering; N R (λ, z) and N R (λ, z0) corresponds to the number of atmospheric echo photons at altitude z and z0 respectively; is the atmospheric two-way transmittance from height z0 to z, and α(λ, z) is the atmospheric extinction coefficient.

[0029] In one embodiment, the atmospheric temperature inversion method in step 7 is:

[0030]

[0031] Among them, T(z u ) and n A (z u ) are respectively the atmospheric temperature and density at the upper boundary height, n A (z) is the atmospheric density at altitude z, R is the universal gas constant, g(z) is the gravitational acceleration, M is the molar mass of atmospheric molecules, z u The upper boundary height.

[0032] In one embodiment, the metrological characteristic evaluation method in step 8 is:

[0033] The mean deviation of the atmospheric temperature is:

[0034]

[0035] The standard uncertainty is:

[0036]

[0037] Among them, T i is the i-th group of inverted atmospheric temperature values, n is the number of Monte Carlo simulation experiments, and To(z) is the target atmospheric temperature at height z.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] The present invention establishes the relationship between Rayleigh laser radar parameters, target temperature and measurement temperature, and realizes the comprehensive evaluation of metrological characteristics such as measurement deviation and measurement uncertainty of the full detection height of Rayleigh temperature measuring laser radar through Monte Carlo simulation test. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 A flowchart of a method for evaluating the metrological characteristics of a Rayleigh temperature measuring laser radar based on the Monte Carlo method according to a specific embodiment of the present invention is shown;

[0042] Figure 2 A sample diagram of setting target atmospheric density and temperature profiles provided according to a specific embodiment of the present invention is shown;

[0043] Figure 3 A sample graph of the Rayleigh backscattering coefficient of the 532nm wavelength laser and the atmospheric two-way transmittance profile calculated according to a specific embodiment of the present invention is shown;

[0044] Figure 4 A sample graph of the photon number profile of the Rayleigh temperature measurement laser radar echo calculated according to a specific embodiment of the present invention is shown;

[0045] Figure 5 A sample graph of a random sample profile of a Monte Carlo simulation echo photon number provided according to a specific embodiment of the present invention is shown. DETAILED DESCRIPTION

[0046] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in 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.

[0047] like Figure 1As shown, the method for evaluating the metrological characteristics of a Rayleigh temperature measuring laser radar based on the Monte Carlo method provided in an embodiment of the present invention comprises the following specific steps:

[0048] Step 1: Obtain the Rayleigh temperature measurement lidar parameters;

[0049] Use a laser power meter to measure the average laser power P L (λ);

[0050] The laser wavelength λ is measured using a laser wavelength level;

[0051] Use a tape measure to measure the telescope aperture A;

[0052] Obtain the optical efficiency of each optical component by checking its factory manual, obtain the quantum efficiency of the photodetector by checking its factory manual, and multiply them to obtain the system efficiency η;

[0053] Set the altitude range, altitude resolution Δz and integration time Δt according to the data acquisition and processing parameters of the LiDAR system;

[0054] Set the reference density n according to the measured atmospheric data or atmospheric model (such as USSA-76) data A (z0) and the corresponding height z0, reference temperature T(z u ) and the upper boundary height z u ;

[0055] Step 2: Set the target atmospheric density and temperature profile;

[0056] Generate a detection height column vector z (such as [30,31,…,70]') based on the laser radar detection range (such as 30-70km) and height resolution (such as 1km) parameters;

[0057] The atmospheric density and temperature of the 1976 United States Standard Atmosphere (USSA-76) are interpolated to the detection altitude through cubic spline to obtain the target atmospheric density profile (column vector), as follows: Figure 2 As shown, Figure 2 (a) is a sample diagram of the target atmospheric density profile. Figure 2 (b) is a sample diagram of the temperature profile.

[0058] Step 3: Calculate the Rayleigh backscattering coefficient and atmospheric two-way transmittance using the Rayleigh temperature laser radar parameters and the target atmospheric density, as follows: Figure 3 As shown, Figure 3 (a) is a sample graph of the Rayleigh backscattering coefficient profile of a 532nm wavelength laser. Figure 3 (b) is a sample diagram of the atmospheric two-way transmittance profile.

[0059] The Rayleigh backscatter coefficient is calculated as:

[0060]

[0061] β(λ, z) = n A (z)σ(λ,z)

[0062] The calculation method of atmospheric two-way transmittance is:

[0063]

[0064]

[0065] The calculation results of the Rayleigh backscattering coefficient and the atmospheric two-way transmittance of 532nm wavelength laser are as follows: Figure 3 shown.

[0066] Where σ(z,λ) is the Rayleigh signal backscattering cross section (m -1 ), λ is the laser wavelength (m), β(λ,z) ​​is the Rayleigh signal backscattering coefficient (m-1sr-1), n A (z) is the atmospheric molecular density (m-3), α(λ,z) ​​is the atmospheric extinction coefficient (m -1 ), T 2 (z, λ) is the atmospheric two-way transmittance.

[0067] Step 4: Calculate the number of echo photons of Rayleigh temperature measurement lidar using the lidar equation;

[0068] The LiDAR equation is:

[0069]

[0070] Among them, N R (λ, z) is the number of echo photons received within the range of z-Δz / 2 to z+Δz / 2, z is the height (m), P L (λ) is the average power of the emitted laser (W), Δt is the integration time (s), and h is Planck’s constant (6.6262×10 - 34 J·s, c is the speed of light (2.99792458×10 8 m / s), λ is the laser wavelength (m), β(λ, z) is the Rayleigh signal backscattering coefficient (m-1sr-1), α(λ, z) is the atmospheric extinction coefficient (m -1 ), T 2 (z, λ) is the atmospheric two-way transmittance, Δz is the distance resolution (m), and A is the receiving telescope area (m 2 ), η is the system efficiency.

[0071] The calculation result of echo photon number is as follows: Figure 4 shown.

[0072] Step 5: Generate random samples of echo photon numbers using the Monte Carlo method according to the characteristics of the Poisson distribution of the number of received photons;

[0073] The random sample of the echo photon number obeys the expected Poisson distribution of the echo photon number obtained in step 4, and the sample is an m×n-order matrix, where m is the length of the detection height column vector and n is the number of Monte Carlo simulation experiments (10,000 times).

[0074] Echo photon number random sample profile sample Figure 5 shown.

[0075] Step 6: Use the echo photon number samples to invert the atmospheric density profile samples;

[0076] The atmospheric density inversion method is:

[0077]

[0078] Among them, n A (z) and n A (z0) are the atmospheric densities at z and z0 respectively; z0 is the reference height of atmospheric Rayleigh scattering; N R (λ, z) and N R (λ, z0) corresponds to the number of echo photons at height z and z0 respectively; is the two-way transmittance of the atmosphere from height z0 to z.

[0079] Step 7: Invert the atmospheric temperature sample using the atmospheric density profile sample and the reference temperature;

[0080] The atmospheric temperature inversion method is:

[0081]

[0082] Among them, T(z u ) and n A (z u ) are respectively the atmospheric temperature and density at the upper boundary height, n A (z) is the atmospheric density at altitude z, R is the gas universal constant (8.31 J / (mol·K)), g(z) is the gravitational acceleration, M is the molar mass of atmospheric molecules (28.959 g / mol), z u The upper boundary height.

[0083] Step 8: Calculate metrological characteristics such as mean deviation and measurement uncertainty of atmospheric temperature.

[0084] The metrological characteristics assessment method is:

[0085] Mean deviation of atmospheric temperature:

[0086]

[0087] Standard uncertainty:

[0088]

[0089] Among them, T i is the i-th group of inverted atmospheric temperature values, n is the number of atmospheric profile groups (the number of Monte Carlo simulation experiments), and To(z) is the target atmospheric temperature at height z.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for evaluating the metrological characteristics of Rayleigh temperature-measuring laser radar based on Monte Carlo method, characterized in that: The method comprises the following steps: Step 1: Obtain the Rayleigh temperature measurement lidar parameters; Step 2: Set the target atmospheric density and temperature profile; Step 3: Calculate the Rayleigh backscattering coefficient and atmospheric two-way transmittance using the Rayleigh temperature laser radar parameters and the target atmospheric density; Step 4: Calculate the number of echo photons of Rayleigh temperature measurement lidar using the lidar equation; Step 5: Generate a random sample of the number of echo photons using the Monte Carlo method according to the characteristics of the Poisson distribution of the number of received echo photons; Step 6: Use the echo photon number samples to invert the atmospheric density profile samples; Step 7: Invert the atmospheric temperature sample using the atmospheric density profile sample and the reference temperature; Step 8: Calculate metrological characteristics such as mean deviation and measurement uncertainty of atmospheric temperature.

2. The method for evaluating the metrological characteristics of Rayleigh temperature measuring laser radar based on Monte Carlo method according to claim 1 is characterized in that: The step 2 of setting the target atmospheric density and temperature profile is specifically as follows: generating a detection height column vector according to the lidar detection range and height resolution parameters, and obtaining the target atmospheric profile by using the atmospheric density and temperature of the 1976 U.S. standard atmosphere through cubic spline interpolation to the detection height.

3. The method for evaluating the metrological characteristics of Rayleigh temperature-measuring laser radar based on Monte Carlo method according to claim 1 is characterized in that: The Rayleigh backscattering coefficient calculation method in step 3 is: β(λ,z)=n A (z)σ(λ,z) The calculation method of atmospheric two-way transmittance in step 3 is: Among them, σ(z, λ) is the Rayleigh signal backscattering cross section, λ is the laser wavelength, β(λ,z) ​​is the Rayleigh signal backscattering coefficient, and n A (z) is the number density of atmospheric molecules, α(λ,z) ​​is the atmospheric extinction coefficient, T 2 (λ, z) is the atmospheric two-way transmittance.

4. The method for evaluating the metrological characteristics of Rayleigh temperature measurement laser radar based on Monte Carlo method according to claim 1 or 3, characterized in that: The method for calculating the number of echo photons in step 4 is: Among them, N R (λ, z) is the number of echo photons received within the range of z-Δz / 2 to z+Δz / 2, z is the height, P L (λ) is the average power of the emitted laser, Δt is the integration time, h is Planck's constant, c is the speed of light, λ is the laser wavelength, β(λ,z) ​​is the Rayleigh signal backscattering coefficient, α(λ,z) ​​is the atmospheric extinction coefficient, T 2 (z, λ) is the atmospheric two-way transmittance, Δz is the distance resolution, A is the receiving telescope area, and η is the system efficiency.

5. The method for evaluating the metrological characteristics of Rayleigh temperature-measuring laser radar based on Monte Carlo method according to claim 1 is characterized in that: In step 5, the random sample of the number of echo photons obeys the expected Poisson distribution of the number of echo photons obtained in step 4, and the random sample of the number of echo photons is an m×n-order matrix, where m is the length of the detection height column vector and n is the number of Monte Carlo simulation experiments.

6. The method for evaluating the metrological characteristics of Rayleigh temperature-measuring laser radar based on Monte Carlo method according to claim 1 is characterized in that: The atmospheric density inversion method in step 6 is: Among them, n A (z) and n A (z0) are the atmospheric densities at altitudes z and z0 respectively; z0 is the reference altitude for atmospheric Rayleigh scattering; N R (λ,z) ​​and N R (λ,z0) corresponds to the number of echo photons at height z and z0 respectively; is the atmospheric two-way transmittance from height z0 to z, and α(λ,z) ​​is the atmospheric extinction coefficient.

7. The method for evaluating the metrological characteristics of Rayleigh temperature-measuring laser radar based on Monte Carlo method according to claim 1 is characterized in that: The atmospheric temperature inversion method in step 7 is: Among them, T(z u ) and n A (z u ) are respectively the atmospheric temperature and atmospheric density at the upper boundary height, n A (z) is the atmospheric density at altitude z, R is the universal gas constant, g(z) is the gravitational acceleration, M is the molar mass of atmospheric molecules, z u The upper boundary height.

8. The method for evaluating the metrological characteristics of Rayleigh temperature-measuring laser radar based on Monte Carlo method according to claim 1 is characterized in that: The metrological characteristic evaluation method in step 8 is: The mean deviation of the atmospheric temperature is: The standard uncertainty is: Among them, T i is the i-th group of inverted atmospheric temperature values, n is the number of Monte Carlo simulation experiments, and To(z) is the target atmospheric temperature at height z.

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