Atmospheric wind field inversion method based on Fabry-Perot interferometer and computer equipment

Abstract

The invention provides an atmospheric wind field inversion method based on a Fabry-Perot interferometer and computer equipment, and the method comprises the steps: 1, constructing an airglow radiation function, and substituting a preset central wavelength initial value into the airglow radiation function; 2, carrying out convolution on an airglow radiation function and an instrument function, and carrying out independent simulation on each interference ring of the FABRY-PEROT interferometer to obtain a peak value position of each interference ring of a simulation curve; 3, comparing measured data observed by the instrument with the peak position of the corresponding interference ring to obtain a difference value between the peak position and the measured data; fourthly, if the difference value obtained in the third step is larger than the set threshold value, the value of the center wavelength in the first step is changed, and the first step is executed again; 5, circulating the steps 1-4 until the difference value between the peak value position of the simulation interference circular ring and the actually measured value is smaller than or equal to a set threshold value, and correspondingly obtaining the airglow center wavelength of each observation data; and 6, calculating the wind speed value of each interference ring by using the airglow center wavelength obtained in the step 5. According to the invention, the inversion precision is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of atmospheric optical detection, and relates to a method for retrieving atmospheric wind field based on a Fabry-Perot interferometer and a computer device, in particular to a method for retrieving atmospheric wind field for each interference ring based on a Fabry-Perot interferometer. Background Technique

[0002] The atmospheric wind field is one of the basic parameters of the near space and the middle and upper atmosphere. The wind field not only plays an important role in the energy transfer between the upper and lower layers of the atmosphere, but also has a great impact on the safety and operating orbit of spacecraft, and is an important space environmental parameter. Therefore, the wind field measurement results can be used as important basic data for establishing an atmospheric model, and at the same time provide important detection data for the research on the coupling process of atmospheric dynamics and photochemistry. At present, the passive optical instruments used for wind field measurement mainly include Fabry-Perot interferometers, Michelson interferometers, and asymmetric spatial heterodyne interferometers. Among them, the Fabry-Perot interferometer has the advantages of high sensitivity, high spectral resolution, and simple structure. There are no moving parts in its optical path, belonging to static interference imaging spectroscopy technology, with high stability, strong anti-seismic interference ability, high energy utilization rate and detection sensitivity. Therefore, the Fabry-Perot interferometer is widely used in spaceborne measurement of the wind speed in the middle and upper atmosphere.

[0003] The research on the algorithm for retrieving the middle and upper atmosphere wind speed based on the Fabry - Perot interferometer began in the 1960s. Hernandez et al. studied and analyzed the analytical model of the Fabry - Perot interferometer, and expounded the defect broadening function that affects the transfer function of the Fabry - Perot interferometer, and simulated the instrument transfer function of the Fabry - Perot interferometer in practical applications. Based on this transfer function, Hays and Roble proposed a non - linear least - squares method to invert the atmospheric wind speed and temperature. It is based on the convolution of the Airy function with the spherical defect function, the planar roughness defect function, and the aperture broadening function to establish the instrument function, without considering the influence of factors such as optical distortion and asymmetry. Therefore, it cannot well simulate and obtain an accurate instrument function, thus limiting the improvement of the wind speed inversion accuracy. Shiokawa et al. based on the relationship between the peak radius of the interference ring and the atmospheric wind speed, first obtained the peak radius by Gaussian fitting, and then directly calculated the wind speed. It is based on the same - order interference rings in two opposite directions of ground - based observations to determine the relationship between the wind speed and the radius of the interference ring. This method directly establishes the relationship between the wind speed and the radius of the interference ring. Therefore, it does not need to obtain accurate instrument parameters in other optical systems, the inversion principle is relatively simple, and the accuracy is relatively high, but it is only applicable to ground - based observations. Harding et al. proposed to establish a forward model of the Fabry - Perot interferometer based on the Airy function, then obtain the instrument function based on the model and laser calibration data, and then invert the middle and upper atmosphere wind field. This method maximizes the simulation of the influence of the interference pattern brought by the instrument function through the improved Airy function. Therefore, its inversion accuracy is also relatively high, but the calculation amount is large. Compared with the international research situation of the Fabry - Perot interferometer algorithm, the research on related algorithms in China started relatively late and the research content is relatively less.

[0004] Although the current inversion methods have been improved, the traditional inversion methods are still easily affected by the background radiation stray light, thus affecting the inversion accuracy. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art or related technologies.

[0006] For this reason, the present invention provides a method for inverting the atmospheric wind field based on a Fabry - Perot interferometer and a computer device. The inversion method of the present invention performs independent simulations for each ring respectively, which can avoid the influence of stray light to the greatest extent, thereby improving the inversion accuracy.

[0007] The technical solution of the present invention is as follows:

[0008] According to one aspect, a method for inverting the atmospheric wind field based on a Fabry - Perot interferometer is provided, and the inversion method includes:

[0009] Step 1: Construct the airglow radiation function and substitute the initial value of the preset central wavelength into the airglow radiation function;

[0010] Step 2: Convolve the airglow radiation function obtained in Step 1 with the instrument function, and on this basis, individually simulate each interference ring of the Fabry-Perot interferometer to obtain the peak position of each interference ring of the simulated curve;

[0011] Step 3: For each interference ring, compare the measured data observed by the instrument with the peak position of the corresponding interference ring to obtain the difference between the peak position and the measured data;

[0012] Step 4: Determine whether the difference obtained in Step 3 is greater than the set threshold. If so, change the value of the central wavelength in Step 1 and execute Step 1 again;

[0013] Step 5: Loop through Steps 1 to 4 until the difference between the peak position of the simulated interference ring and the measurement is less than or equal to the set threshold, and accordingly obtain the airglow central wavelength of each observation data;

[0014] Step 6: According to the Doppler frequency shift principle, calculate the wind speed value of each interference ring using the airglow central wavelength obtained in Step 5;

[0015] Step 7: Average the wind speed values of each interference ring obtained in Step 6 to obtain the final wind speed inversion result of this observation data.

[0016] Further, the airglow radiation function is constructed by the following formula:

[0017]

[0018] where \(Y(\lambda)\) is the airglow radiation function, \(Y\) bg is the background radiation, \(Y\) line is the airglow radiation intensity, \(\lambda\) is the wavelength, \(\lambda\) c is the central wavelength with wind speed information, and \(\Delta\lambda\) is the Doppler broadening.

[0019] Further, the convolution of the airglow radiation function obtained in Step 1 with the instrument function is performed by the following formula:

[0020]

[0021] where \(S(r)\) is the convolution function, \(B\) is the CCD count offset value, \(A_i(r,\lambda)\) represents the instrument function of the interferometer, and \(r\) represents the radius.

[0022] Further, in Step 4, changing the value of the central wavelength in Step 1 specifically includes:

[0023] Change the value of the central wavelength in Step 1 according to the positive or negative of the difference. Specifically, if the difference is positive, the central wavelength moves towards the short-wave direction; otherwise, it moves in the opposite direction.

[0024] Further, the threshold is set to 0.01 pixel, corresponding to a wind speed of 0.5 m / s.

[0025] Further, the method further includes performing data preprocessing on the measured data, and the data preprocessing includes median filtering, mean filtering, circular integration, and extraction of each ring.

[0026] According to another aspect, a computer device is provided, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the above inversion method is implemented.

[0027] The inversion method provided by the above technical solution performs independent simulations for each ring respectively, including strategies such as designing threshold comparison and changing the central wavelength. Thereby, the influence of stray light can be avoided, and the inversion accuracy can be improved. Based on certain airglow observation data, the wind speed is inverted using the inversion algorithm of the present invention. Comparing the inversion results with those obtained by traditional methods, the inversion accuracy is significantly improved, especially when the influence of stray light is large. Description of the Drawings

[0028] The included drawings are used to provide a further understanding of the embodiments of the present invention. They form a part of the specification, are used to illustrate the embodiments of the present invention, and are used to explain the principles of the present invention together with the text description. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0029] Figure 1 It is a two-dimensional interference ring diagram obtained by a Fabry-Perot interferometer CCD two-dimensional detector with strong background radiation and stray light interference;

[0030] Figure 2 It is a one-dimensional interference ring diagram obtained by circular integration of the two-dimensional interference rings of a Fabry-Perot interferometer;

[0031] Figure 3 It is the comparison result between the forward simulation and the measured value of a single ring of a Fabry-Perot interferometer;

[0032] Figure 4 It is the main flow steps of the wind speed inversion of the present invention;

[0033] Figure 5Comparison of the results obtained by using traditional one-time fitting and the inversion of interference fringes one by one according to the present invention with other reference results. Detailed implementation manners

[0034] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way restrictive of the present invention and its application or use. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0035] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0036] Unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions, and values set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that, for the sake of convenience of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationships. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but should be regarded as part of the authorized specification when appropriate. In all the examples shown and discussed herein, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0037] Since the wavelength used in laser calibration is inconsistent with the wavelength of airglow, it is necessary to reconvolve the instrument function with the airglow radiation function to establish a forward airglow interference model of the Fabry-Perot interferometer. The specific steps are as follows:

[0038] As Figure 4 shown, in an embodiment of the present invention, there is provided an atmospheric wind field inversion method based on a Fabry-Perot interferometer. The inversion method includes:

[0039] Step 1: Construct an airglow radiation function and substitute a preset initial value of the central wavelength into the airglow radiation function;

[0040] Step 2: Convolve the airglow radiation function obtained in Step 1 with the instrument function, and on this basis, individually simulate each interference ring of the Fabry - Perot interferometer to obtain the peak position of each interference ring of the simulated curve;

[0041] Step 3: For each interference ring, compare the measured data observed by the instrument with the peak position of the corresponding interference ring to obtain the difference between the peak position and the measured data (i.e., the former minus the latter);

[0042] Step 4: Determine whether the difference obtained in Step 3 is greater than a set threshold. If so, change the value of the central wavelength in Step 1 and execute Step 1 again (i.e., repeat the above steps starting from Step 1);

[0043] Step 5: Loop through Steps 1 to 4 until the difference between the peak position of the simulated interference ring and the measured value is less than or equal to the set threshold, and accordingly obtain the airglow central wavelength of each observation data;

[0044] Step 6: According to the Doppler frequency shift principle, calculate the wind speed value of each interference ring using the airglow central wavelength obtained in Step 5;

[0045] Step 7: Average the wind speed values of each interference ring obtained in Step 6 to obtain the final wind speed inversion result of this observation data.

[0046] That is, when the Fabry - Perot interferometer is severely affected by strong background radiation stray light, different interference rings on the two - dimensional detector of the Fabry - Perot interferometer are affected differently (as Figure 1 shown), the background radiation intensity of each ring is different, so the background of each ring after circumferential integration is also different. The specific results are as Figure 2 shown: Figure 2 In it, the background radiation level (the lowest DN value) of each ring is different. In this case, it is very difficult to simulate the actual observation effect using the traditional forward model, resulting in a poor inversion result.

[0047] Therefore, in the embodiments of the present invention, the airglow radiation function is convolved with the instrument function, and each interference ring of the Fabry-Perot interferometer is separately simulated to obtain the peak position of each interference ring of the simulated curve. Then, the corresponding measured data is compared with the peak position of the interference ring, and the difference between the two is calculated. This method can avoid the problem of non-convergence of the simulation caused by background stray light, thereby obtaining a better inversion result. If the calculated difference is greater than the set threshold, the airglow central wavelength will be changed according to the positive or negative of the difference, so as to establish a new interference simulation curve of the Fabry-Perot interferometer; the above steps are cycled until the difference between the peak position of the simulated interference ring and the measured value is within the set threshold, so as to obtain the airglow central wavelength of each observation data.

[0048] Applying the above configuration method, by separately simulating each ring, including strategies such as designing threshold comparison and changing the central wavelength, the influence of stray light can be avoided, thereby improving the inversion accuracy. Based on certain airglow observation data, the wind speed inversion is carried out using the inversion algorithm of the present invention, and the inversion result is compared with the result obtained by the traditional method. The inversion accuracy is significantly improved, especially when the influence of stray light is large.

[0049] In the above embodiment, the airglow radiation function is constructed by the following formula:

[0050]

[0051] where Y(λ) is the airglow radiation function, Y bg is the background radiation, Y line is the airglow radiation intensity, λ is the wavelength, λ c is the central wavelength with wind speed information, and Δλ is the Doppler broadening.

[0052] That is to say, in step four, if the difference obtained in step three is greater than the set threshold, the value of the central wavelength λc in step one is changed.

[0053] In the above embodiment, the airglow radiation function obtained in step one is convolved with the instrument function by the following formula:

[0054]

[0055] where S(r) is the convolution function, B is the CCD count offset value, Ai(r,λ) represents the instrument function of the interferometer, and r represents the radius.

[0056] Specifically, the core component of the Fabry-Perot interferometer is a parallel glass plate coated with a reflective film, that is, an etalon. Let the etalon plate spacing be t and the incident light wavelength be λ, then the ideal instrument function (i.e., the Airy function) of the Fabry-Perot interferometer is:

[0057]

[0058] In Equation 1, I is the intensity, R is the etalon reflectivity, n is the atmospheric refractive index, and θi is the angle with the optical axis, which is a function of the interference ring radius and the focal length. From Equation 1, it can be obtained that there is a trigonometric function relationship between the wavelength λ and the interference ring radius. When other parameters remain unchanged, the change of the central wavelength will cause the movement of the interference ring. Therefore, through Equation 1, the forward model of the interference ring of the FABRY-PEROT interferometer can be established, and thus the relationship model between the wavelength and the interference ring radius can be established. In addition, in this embodiment, an intensity function and a point spread function are introduced to better describe the actual situation of the optical system of the FABRY-PEROT interferometer. Therefore, the Airy function

[0059] Equation 1 then becomes:

[0060]

[0061] Each pixel of the improved Airy function is the weighting of adjacent pixels of the ideal Airy function. The point spread function broadens the fringes, thus simulating the influence of optical distortion. Equation 2 is the instrument function of the FABRY-PEROT interferometer. Convolving it with the radiation function and adding the CCD bias factor, then

[0062]

[0063] In Equation 3, B is the CCD count offset value, Y is the airglow and background radiation function, which is a function of the airglow radiation intensity, background radiation, wavelength, and spectral width. The wavelength and spectral width are respectively related to the wind speed and temperature. Therefore, the airglow radiation function with the changes of wind speed and temperature information can be expressed as:

[0064]

[0065] In Equation 4, Y bg is the background radiation, Y line is the airglow radiation intensity, λ is the wavelength, λ c is the central wavelength with wind speed information, and Δλ is the Doppler broadening. Among them,

[0066]

[0067] In Equation 5, λ0 is the wavelength at zero wind speed, v is the wind speed, c is the speed of light, k is the Boltzmann constant, T is the temperature, and m is the molar mass.

[0068] In the above embodiment, in Step 4, changing the value of the central wavelength in Step 1 specifically includes:

[0069] Change the value of the central wavelength in Step 1 according to the positive or negative of the difference. Specifically, if the difference is positive, the central wavelength moves towards the short - wave direction, and vice versa.

[0070] Preferably, the threshold is set to 0.01 pixel, corresponding to a wind speed of 0.5 m / s.

[0071] According to another embodiment, a computer device is provided, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the inversion method of the above - mentioned embodiment is implemented.

[0072] To have a further understanding of the method of the present invention, the following takes a specific embodiment for detailed description:

[0073] As Figure 4 shown, the specific steps of the method of this embodiment are as follows:

[0074] (1) First, construct an airglow radiation function for the observed object airglow of the Fabry - Perot interferometer, and construct an instrument function based on the performance parameters of the Fabry - Perot interferometer itself;

[0075] (2) Convolve the airglow radiation function with the instrument function to obtain the simulated observation results of each ring of the Fabry - Perot interferometer. At the same time, perform data pre - processing on the actual observation results, including median filtering, mean filtering, circular integration, and extraction of each ring;

[0076] (3) Compare and analyze the observed simulation values and measured values of each ring to obtain the wind speed inversion value of each ring;

[0077] (4) Average the wind speed inversion values of each ring to obtain the final wind speed inversion result.

[0078] Based on the above - mentioned method, two inversion methods are used to invert the atmospheric wind field for the observation data of 630.0 nm on September 1, 2023, and the inversion results are shown in the following figure:

[0079] Figure 5Among them, the data of the atmospheric wind field obtained by the Canadian instrument KEO are the data of the circular-line, the data of the wind speed obtained by the traditional method of fitting all interference rings at one time are the data of the *-line, and the remaining line data are the wind field results obtained by independently fitting each interference ring separately according to the present invention. The results obtained by the two methods are compared and analyzed with the KEO results. The average error obtained by the method of one-time overall fitting is 14.6065 m / s, and the average error of the wind field obtained by inverting each ring is 7.5344 m / s. It can be seen that the inversion of each ring can significantly improve the inversion accuracy of the wind speed, especially when the influence of stray light is serious, the improvement of the wind speed inversion accuracy is more obvious (such as the comparison of the observation results at UTC time 16-18).

[0080] Features described and / or illustrated above for one embodiment can be used in the same or similar manner in one or more other embodiments, and / or combined with or substitute for features in other embodiments.

[0081] It should be emphasized that the term "comprising / including" when used herein refers to the presence of features, whole things, steps or components, but does not exclude the presence or addition of one or more other features, whole things, steps, components or combinations thereof.

[0082] The above method of the present invention can be implemented by hardware or by a combination of hardware and software. The present invention relates to such a computer-readable program that, when executed by a logic component, can enable the logic component to implement the device or component described above, or enable the logic component to implement the various methods or steps described above. The present invention also relates to a storage medium for storing the above program, such as a hard disk, a magnetic disk, an optical disk, a DVD, a flash memory, etc.

[0083] Many features and advantages of these embodiments are clear from this detailed description, so the appended claims are intended to cover all such features and advantages of these embodiments that fall within their true spirit and scope. In addition, since many modifications and changes are readily conceivable by those skilled in the art, the embodiments of the present invention are not to be limited to the exact structures and operations illustrated and described, but may cover all suitable modifications and equivalents falling within their scope.

[0084] The parts not detailed in the present invention are well-known technologies to those skilled in the art.

Claims

1. An atmospheric wind field inversion method based on a Fabry-Perot interferometer, characterized in that, The inversion method includes: Step 1: Construct an airglow radiation function and substitute a preset initial value of the central wavelength into the airglow radiation function; Step 2: Convolve the airglow radiation function obtained in Step 1 with the instrument function, and on this basis, separately simulate each interference ring of the Fabry - Perot interferometer to obtain the peak position of each interference ring of the simulated curve; Step 3: For each interference ring, compare the measured data observed by the instrument with the peak position of the corresponding interference ring to obtain the difference between the peak position and the measured data; Step 4: Determine whether the difference obtained in Step 3 is greater than a set threshold. If so, change the value of the central wavelength in Step 1 and execute Step 1 again; Step 5: Loop Steps 1 to 4 until the difference between the peak position of the simulated interference ring and the measurement is less than or equal to the set threshold, and accordingly obtain the airglow central wavelength of each observation data; Step 6: According to the Doppler frequency shift principle, calculate the wind speed value of each interference ring using the airglow central wavelength obtained in Step 5; Step 7: Average the wind speed values of each interference ring obtained in Step 6 to obtain the final wind speed inversion result of the current observation data.

2. The atmospheric wind field inversion method based on a Fabry - Perot interferometer according to claim 1, characterized in that The airglow radiation function is constructed by the following formula: Among them, Y(λ) is the airglow radiation function, Y bg is the background radiation, Y line is the airglow radiation intensity, λ is the wavelength, λ c is the central wavelength with wind speed information, and Δλ is the Doppler broadening.

3. A method for retrieving atmospheric wind field based on Fabry - Perot interferometer according to claim 2, characterized in that, The airglow radiation function obtained in Step 1 is convolved with the instrument function by the following formula: where S(r) is the convolution function, B is the CCD count offset value, Ai(r,λ) represents the instrument function of the interferometer, and r represents the radius.

4. A method for retrieving atmospheric wind field based on Fabry - Perot interferometer according to any one of claims 1 - 3, characterized in that, In Step 4, changing the value of the central wavelength in Step 1 specifically includes: Changing the value of the central wavelength in Step 1 according to the positive or negative of the difference. Among them, if the difference is positive, the central wavelength moves towards the short - wave direction, and vice versa.

5. A method for retrieving atmospheric wind field based on a Fabry-Perot interferometer according to any one of claims 1-4, characterized in that, The threshold is set to 0.01 pixel, corresponding to a wind speed of 0.5 m / s.

6. The method for retrieving atmospheric wind field based on a Fabry - Perot interferometer according to claim 1, wherein, The method further includes data pre - processing of the measured data, and the data pre - processing includes median filtering, mean filtering, circular integration, and extraction of each ring.

7. A computer device, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the inversion method according to any one of claims 1 - 6.

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