Infrared absorption band atmospheric spectral transmittance measurement method

Abstract

The present application relates to a kind of infrared absorption waveband atmospheric spectral transmittance measurement method, it is related to detection field, including the following steps, selecting the spectrometer capable of covering absorption waveband, and installing atmospheric absorption band filter on spectrometer;According to the minimum, maximum measurement value of spectrometer parameter selection corresponding attenuator;Spectrometer is directly aimed at solar spectrum data acquisition, reads the background average corresponding digital value measured by spectrometer;The bad point of calculated spectral data is rejected;Using the spectral calibration data in laboratory, the spectral data that has been rejected is quantitatively inversed, the radiation brightness of spectrometer is calculated;The absorption waveband spectral brightness of solar reaching ground is calculated;According to the radiation brightness of calculated spectrometer and the absorption waveband spectral brightness of solar reaching ground, atmospheric spectral transmittance is directly calculated, the present application has the advantages of expanding the measurement and inversion means of shortwave infrared absorption band atmospheric transmittance spectral research.

Description

Technical Field

[0001] This invention relates to the field of detection technology, and in particular to a method for calculating atmospheric spectral transmittance in the infrared absorption band. Background Technology

[0002] The infrared absorption band refers to the band in which atmospheric water vapor and carbon dioxide absorb a large amount of light energy. However, the absorption band is very meaningful for research. For example, in space-based downward-looking observation, this band is selected to avoid interference from the Earth's background. However, the observation is also affected by atmospheric transmittance.

[0003] Therefore, to address the above shortcomings, a method for calculating atmospheric spectral transmittance in the infrared absorption band is needed. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] The technical problem to be solved by this invention is to solve the problem of quantitative sensing of atmospheric transmittance in the infrared absorption band.

[0006] (II) Technical Solution

[0007] To address the aforementioned technical problems, this invention provides a method for calculating atmospheric spectral transmittance in the infrared absorption band, comprising the following steps:

[0008] Ⅰ. Select a spectrometer that can cover the absorption band and install an atmospheric absorption band filter on the spectrometer;

[0009] II. Estimate the energy in the solar absorption band; then select the appropriate attenuator based on the minimum and maximum measured values ​​of the spectrometer.

[0010] III. Point the spectrometer directly at the sun to collect spectral data and read the corresponding digital value of the background average measured by the spectrometer;

[0011] IV. Remove bad pixels from the calculated spectral data;

[0012] V. Using spectral calibration data in the laboratory, quantitative inversion is performed on the removed spectral data to calculate the radiance of the spectrometer;

[0013] VI. Calculate the spectral brightness of the absorption band of the sun reaching the ground;

[0014] VII. Based on the calculated spectrometer radiance and the spectral radiance of the absorption band of the sun reaching the ground, the atmospheric spectral transmittance can be directly calculated.

[0015] As a further explanation of the present invention, preferably, the wavelength range of the spectrometer is selected as 2 to 15 μm.

[0016] As a further explanation of the present invention, preferably, a narrowband filter with an absorption band of 2.7 μm is selected.

[0017] As a further explanation of the present invention, preferably, the quantitative inversion step of the removed spectral data is as follows:

[0018] L device (λ)=DN0(λ)×Gain(λ)+Offset(λ)

[0019] Wherein, DN0(λ) is the digital value of the background average response measured by the spectrometer;

[0020] Gain(λ) and Offset(λ) are the spectral radiometric calibration parameters of the spectrometer.

[0021] As a further explanation of the present invention, preferably, the spectral brightness L of the absorption band of the sun reaching the ground is... earth (λ) is:

[0022] L earth (λ)=L device (λ)·σ(λ)·K(λ)

[0023] Where σ(λ) is the attenuation coefficient of the attenuator;

[0024] K(λ) is the transmittance of the filter.

[0025] As a further explanation of the present invention, preferably, the atmospheric transmittance in the absorption band is:

[0026]

[0027] Where L space (λ) represents the solar spectral radiance outside the atmosphere, a stable and known value.

[0028] (III) Beneficial Effects

[0029] The above-described technical solution of the present invention has the following advantages:

[0030] This invention proposes a method for calculating the transmittance of atmospheric spectra in the infrared absorption band, which can be applied to improve the quantitative sensing capability of sensors using the absorption band in certain fields. Attached Figure Description

[0031] Figure 1 This is a flowchart of the processing of the present invention;

[0032] Figure 2 These are images showing the effect before and after defect removal according to the present invention.

[0033] Figure 3 This is a brightness data map obtained by the ground spectrometer of the present invention;

[0034] Figure 4 This is a diagram showing the calculated brightness of the solar spectrum outside the atmosphere according to the present invention;

[0035] Figure 5 This is the atmospheric transmittance spectrum of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] A method for calculating atmospheric spectral transmittance in the infrared absorption band, such as Figure 1 As shown, it includes the following steps:

[0038] 1. Selection of broadband spectrometer:

[0039] A spectrometer capable of covering the absorption band is selected; for example, the MR304SC spectrometer with a wavelength of 2–15 μm is selected in this invention.

[0040] 2. Selection of filters for atmospheric absorption bands:

[0041] Since the energy reaching the ground from the sun is weaker in the absorption band, solar radiation energy measurement using a spectrometer mainly uses absorption band filters to filter out the strong energy of the sun in other bands, retaining only the energy in the required spectral bands.

[0042] Select a filter for the absorption band to be measured. For example, in this invention, a narrowband filter with a 2.7μm absorption band is selected.

[0043] 3. Install an atmospheric absorption band filter on the broadband spectrometer.

[0044] 4. Energy prediction for solar absorption band;

[0045] The energy range of the absorption band is estimated using existing atmospheric transmittance calculation software and the spectral brightness distribution of the sun outside the atmosphere.

[0046] 5. Based on the results of step 4, select the appropriate attenuator according to the minimum and maximum measured values ​​of the spectrometer.

[0047] 6. Using the measuring equipment from steps 1-5, directly aim at the sun to collect spectral data, and read the average digital value of the background response measured by the spectrometer, denoted as DN0(λ). During measurement, select an optical lens with an appropriate field of view to ensure that the sun fills the entire detection field of view.

[0048] 7. Defect removal from spectral data:

[0049] The defect removal process for the spectral data calculated in step 6 mainly aims to remove individual outliers or singularities, such as... Figure 2 As shown, a represents the effect before removing bad pixels, and b represents the effect after removing bad pixels.

[0050] 8. Using the spectral calibration data in the laboratory, perform quantitative inversion on the data obtained in step 7 to calculate the radiance acquired by the spectrometer; the inversion steps are as follows:

[0051] L device (λ)=DN0(λ)×Gain(λ)+Offset(λ)

[0052] Wherein, DN0(λ) is the digital value of the background average response measured by the spectrometer;

[0053] Gain(λ) and Offset(λ) are the spectral radiometric calibration parameters of the spectrometer.

[0054] 9. Calculate the spectral brightness of the absorption band of the sun reaching the ground (before filtering and attenuation):

[0055] L eart (λ)=L device (λ)·σ(λ)·K(λ)

[0056] Where σ(λ) is the attenuation coefficient of the attenuator;

[0057] K(λ) is the transmittance of the filter;

[0058] Get as Figure 3 The results are shown.

[0059] 10. Obtain the solar spectral radiance L outside the atmosphere space (λ), this value is known and stable, such as Figure 4 As shown. Note: The spectral interval is aligned with the measurement of the spectrometer at this time.

[0060] 11. Calculate the atmospheric transmittance in the absorption band using the results from 8 and 9:

[0061]

[0062] Where L space (λ) represents the solar spectral radiance outside the atmosphere; this value is stable and known. The inversion results are as follows: Figure 5 As shown.

[0063] In summary, this invention provides a practical method for measuring and inverting atmospheric transmittance spectra in the shortwave infrared absorption band. By acquiring solar spectral measurement data, quantitative analysis of the solar irradiation spectrum in the shortwave infrared absorption band is conducted, and the atmospheric transmittance spectrum is calculated and inverted. This invention expands the measurement and inversion methods for studying atmospheric transmittance spectra in the shortwave infrared absorption band and can be applied to improve the quantitative sensing capabilities of sensors operating in the absorption band in certain fields.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating atmospheric spectral transmittance in the infrared absorption band, characterized in that: Includes the following steps, Ⅰ. Select a spectrometer that can cover the absorption band and install an atmospheric absorption band filter on the spectrometer; II. Estimate the energy range of the absorption band using existing atmospheric transmittance calculation software and the spectral brightness distribution of the sun outside the atmosphere; then select the appropriate attenuator based on the parameters of the minimum and maximum measured values ​​of the spectrometer. III. Point the spectrometer directly at the sun to collect spectral data, and read the corresponding digital value of the background average measured by the spectrometer; IV. Remove bad pixels from the calculated spectral data; V. Using spectral calibration data in the laboratory, quantitative inversion is performed on the removed spectral data to calculate the radiance of the spectrometer; VI. Calculate the spectral brightness of the absorption band of the sun reaching the ground; VII. Based on the calculated spectrometer radiance and the spectral radiance of the absorption band of the sun reaching the ground, the atmospheric spectral transmittance is directly calculated.

2. The method for calculating atmospheric spectral transmittance in the infrared absorption band according to claim 1, characterized in that: The wavelength range of the spectrometer was selected from 2 to 15 μm.

3. The method for calculating atmospheric spectral transmittance in the infrared absorption band according to claim 2, characterized in that: A narrowband filter with an absorption band of 2.7 μm was selected.

4. The method for calculating atmospheric spectral transmittance in the infrared absorption band according to claim 1, characterized in that: The quantitative inversion steps for the removed spectral data are as follows: in, Radiance; The digital value of the background average response measured by the spectrometer; and These are the spectral radiometric calibration parameters for the spectrometer.

5. The method for calculating atmospheric spectral transmittance in the infrared absorption band according to claim 4, characterized in that: Sun's spectral brightness in the absorption band reaching the ground for: in The attenuation coefficient of the attenuator; This represents the transmittance of the filter.

6. The method for calculating atmospheric spectral transmittance in the infrared absorption band according to claim 5, characterized in that: Atmospheric transmittance in the absorption band is: in This represents the solar spectral radiance outside the atmosphere; this value is stable and known.

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