CN115931789A - Method for measuring and calculating atmospheric spectral transmittance in infrared absorption band - Google Patents

Abstract

The invention relates to a method for measuring and calculating the atmospheric spectral transmittance of an infrared absorption waveband, which relates to the field of detection and comprises the following steps of selecting a spectrometer capable of covering the absorption waveband, and additionally installing an atmospheric absorption waveband optical filter on the spectrometer; selecting corresponding attenuation sheets according to parameters of minimum and maximum measurement values of the spectrometer; directly aligning a spectrometer to the sun to acquire spectral data, and reading a background average corresponding digital value measured by the spectrometer; eliminating the calculated spectrum data dead pixels; quantitatively inverting the rejected spectral data by using spectral calibration data in a laboratory, and calculating the radiance of a spectrometer; calculating the spectral brightness of the absorption waveband when the sun reaches the ground; according to the calculated spectrometer radiation brightness and the spectrum brightness of the absorption waveband that the sun reaches the ground, the atmospheric spectrum transmittance is directly calculated.

Description

Method for measuring and calculating atmospheric spectral transmittance in infrared absorption band

Technical Field

The invention relates to the technical field of detection, in particular to a method for measuring and calculating atmospheric spectral transmittance in an infrared absorption waveband.

Background

The infrared absorption band means that the atmospheric light energy is greatly absorbed under the band due to the absorption influence of water vapor and carbon dioxide in the atmospheric air, but in research, the absorption band is very significant for detection, for example, in view detection under the space base, the band needs to be selected to avoid the interference influence of the earth background, but the atmospheric transmittance can also be influenced during observation.

Therefore, in order to overcome the above disadvantages, it is necessary to provide a method for measuring and calculating the atmospheric spectral transmittance in the infrared absorption band.

Disclosure of Invention

Technical problem to be solved

The invention aims to solve the technical problem of quantitative sensing of atmospheric transmittance in an infrared absorption band.

(II) technical scheme

In order to solve the above technical problems, the present invention provides a method for measuring and calculating the atmospheric spectral transmittance in the infrared absorption band, comprising the following steps,

selecting a spectrometer capable of covering an absorption waveband, and additionally installing an atmospheric absorption band waveband optical filter on the spectrometer;

estimating the energy of the solar absorption wave band; then selecting corresponding attenuation sheets according to parameters of minimum and maximum measurement values of the spectrometer;

directly aligning the spectrometer to the sun to acquire spectral data, and reading a background average corresponding digital value measured by the spectrometer;

IV, eliminating the calculated spectrum data dead pixels;

v, quantitatively inverting the rejected spectrum data by using the spectrum calibration data in the laboratory, and calculating the radiance of the spectrometer;

VI, calculating the spectral brightness of the absorption waveband when the sun reaches the ground;

and VII, directly calculating the atmospheric spectral transmittance according to the calculated spectrometer radiation brightness and the spectrum brightness of the absorption waveband that the sun reaches the ground.

As a further illustration of the present invention, the wavelength range of the spectrometer is preferably selected to be 2 to 15 μm.

As a further illustration of the invention, a 2.7 μm narrow band filter in the absorption band is preferably chosen.

As a further explanation of the present invention, preferably, the quantitative inversion step of the rejected spectrum data is:

L _device (λ)＝DN ₀ (λ)×Gain(λ)+Offset(λ)

wherein DN ₀ (λ) is the background mean response digital value measured by the spectrometer;

gain (lambda) and Offset (lambda) are spectral radiance calibration parameters of the spectrometer.

As a further illustration of the invention, it is preferred that the solar to ground absorption band spectral luminance L _earth (λ) is:

L _earth (λ)＝L _device (λ)·σ(λ)·K(λ)

wherein σ (λ) is the attenuation coefficient of the attenuation sheet;

k (lambda) is the filter transmittance.

As a further illustration of the present invention, it is preferred that the absorption band atmospheric transmittance is:

wherein L is _space (λ) is the solar spectral radiance outside the atmosphere, which is a stable and known value.

(III) advantageous effects

The technical scheme of the invention has the following advantages:

the invention provides a method for measuring and calculating the atmospheric spectral transmittance of an infrared absorption waveband, which can be applied to improving the quantitative sensing capability of a sensor adopting an absorption band working waveband in some fields.

Drawings

FIG. 1 is a process flow diagram of the present invention;

FIG. 2 is a diagram showing the effect of the present invention before and after dead pixel removal;

FIG. 3 is a graph of luminance data obtained by the ground spectrometer of the present invention;

FIG. 4 is a graph of calculated solar spectral luminance outside the atmosphere in accordance with the present invention;

FIG. 5 is a chart of the atmospheric transmission spectra of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

A method for measuring and calculating the atmospheric spectral transmittance in an infrared absorption band is shown in figure 1 and comprises the following steps:

1. selecting a broad spectrum spectrometer:

a spectrometer covering the absorption band is selected, for example, a 2-15 μm MR304SC spectrometer is selected in the present invention.

2. Selecting an atmospheric absorption band wave band filter:

because the energy of the sun reaching the ground in the absorption waveband is weak, the spectrometer is mainly used for measuring the solar radiation energy, the absorption waveband optical filter is mainly used for filtering out the strong energy of the sun in other wavebands, and only the required spectral band energy is reserved.

The filter of the absorption band to be measured and calculated is selected, for example, the invention selects the narrow band filter of the absorption band of 2.7 μm.

3. And an atmospheric absorption band wave band filter is additionally arranged on the wide-spectrum spectrometer.

4. Estimating the energy of the solar absorption wave band;

the energy range of the absorption waveband is estimated by utilizing the existing atmosphere transmittance calculation software and the spectral brightness distribution of the sun outside the atmosphere.

5. And (5) selecting a corresponding attenuation sheet according to the result of the step (4) and parameters such as the minimum and maximum measurement values of the spectrometer.

6. Utilizing the measuring equipment in the steps 1-5 to directly aim at the sun for spectrum data acquisition, reading a background average response digital value measured by a spectrometer and recording the background average response digital value as DN ₀ (lambda). And during measurement, an optical lens with a proper view field size is selected, so that the whole detection view field is full of the sun.

7. Spectrum data dead pixel elimination:

and (3) eliminating the spectral data dead pixels calculated in the step (6), wherein the elimination of individual singular points or singular points is mainly realized, and as shown in fig. 2, a is the effect before the dead pixels are eliminated, and b is the effect after the dead pixels are eliminated.

8. Carrying out quantitative inversion on the data obtained in the step (7) by using spectral calibration data in a laboratory, and calculating the radiance obtained by a spectrometer; the inversion steps are as follows:

L _device (λ)＝DN ₀ (λ)×Gain(λ)+Offset(λ)

wherein DN ₀ (λ) is the background mean response digital value measured by the spectrometer;

gain (lambda) and Offset (lambda) are spectral radiance calibration parameters of the spectrometer.

9. Calculating the spectral brightness of the absorption band (before filtering and attenuation) of the sun to the ground:

L _eart (λ)＝L _device (λ)·σ(λ)·K(λ)

wherein σ (λ) is the attenuation coefficient of the attenuation sheet;

k (lambda) is the transmittance of the filter;

the results shown in fig. 3 were obtained.

10. Obtaining the outside-atmosphere solar spectrum radiation brightness L _space (λ), this value is known and stable, as shown in fig. 4. Note that: the spectral intervals are now aligned with the spectrometer measurements.

11. The results of 8 and 9 were used to calculate the absorption band atmospheric transmittance:

wherein L is _space (λ) is the solar spectral radiance outside the atmosphere, which is a stable and known value. The inversion results are shown in fig. 5.

In conclusion, the invention provides a short wave infrared absorption band atmospheric transmittance spectrum measurement and inversion method with practical operability, which is used for carrying out quantitative analysis on solar irradiation spectrum of the short wave infrared absorption band of the sun by acquiring solar spectrum measurement data and calculating inversion atmospheric transmittance spectrum; the invention expands the measurement and inversion means of the research of the short wave infrared absorption band atmospheric transmittance spectrum, and can be applied to the quantitative perception capability improvement of the sensor adopting the absorption band working wave band in some fields.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (6)

1. A method for measuring and calculating the atmospheric spectral transmittance in an infrared absorption waveband is characterized by comprising the following steps: comprises the following steps of (a) carrying out,

selecting a spectrometer capable of covering an absorption band, and additionally arranging an atmospheric absorption band filter on the spectrometer;

estimating the energy of the solar absorption wave band; then selecting corresponding attenuation sheets according to parameters of minimum and maximum measurement values of the spectrometer;

directly aligning the spectrometer to the sun to acquire spectral data, and reading a background average corresponding digital value measured by the spectrometer;

IV, eliminating the dead spots of the calculated spectral data;

carrying out quantitative inversion on the rejected spectrum data by using the spectrum calibration data in a laboratory, and calculating the radiance of the spectrometer;

VI, calculating the spectral brightness of the absorption waveband when the sun reaches the ground;

and VII, directly calculating the atmospheric spectral transmittance according to the calculated spectrometer radiation brightness and the absorption band spectral brightness of the sun reaching the ground.

2. The method for measuring and calculating the atmospheric spectral transmittance in the infrared absorption band according to claim 1, wherein: the wave band range of the spectrometer is selected to be 2-15 mu m.

3. The method for measuring and calculating the atmospheric spectral transmittance in the infrared absorption waveband according to claim 2, wherein: a2.7 μm narrow-band filter with absorption band was selected.

4. The method for measuring and calculating the atmospheric spectral transmittance in the infrared absorption waveband according to claim 1, wherein: the quantitative inversion steps of the rejected spectral data are as follows:

L _device (λ)＝DN ₀ (λ)×Gain(λ)+Offsset(λ)

wherein DN ₀ (λ) is the background mean response digital value measured by the spectrometer;

gain (lambda) and offset (lambda) are spectral radiation calibration parameters of the spectrometer.

5. The method for measuring and calculating the atmospheric spectral transmittance in the infrared absorption waveband as claimed in claim 4, wherein the method comprises the following steps: absorption band spectral brightness L of the sun to ground _earth (λ) is:

L _earth (λ)＝L _device (λ)·σ(λ)·K(λ)

wherein σ (λ) is the attenuation coefficient of the attenuation sheet;

k (lambda) is the filter transmittance.

6. The method for measuring and calculating the atmospheric spectral transmittance in the infrared absorption band according to claim 5, wherein: the absorption band atmospheric transmittance is:

wherein L is _space (λ) is the solar spectral radiance outside the atmosphere, which is a stable and known value.

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