A Method and System for Secondary Spectrum Filtering of Hyperspectral Cameras

Abstract

The present invention discloses a method and system for second-order spectrum filtering of a hyperspectral camera, including determining the theoretical overlapping wavelengths of the first-order spectrum and the second-order spectrum based on the theoretical wavelength range and the actual wavelength range measurable by the hyperspectral camera, and obtaining the actual wavelength range of the second-order spectrum within the overlapping region; adjusting the integration time, analyzing the corresponding relationship between the first-order spectrum intensity and the second-order spectrum intensity in each band within the actual wavelength range of the second-order spectrum in the overlapping region to obtain relationship parameters, and obtaining a characteristic parameter matrix; interpolating to generate the second-order spectrum data of the overlapping wavelength range according to the actual wavelength range of the second-order spectrum in the overlapping region and the characteristic parameter matrix; filtering the second-order spectrum data from the original spectrum to obtain the final hyperspectral data, realizing the filtering of the second-order spectrum in the hyperspectral camera, solving the problem of adjacent-order spectrum overlap generated during grating spectroscopy, reducing the interference of the second-order spectrum on the first-order spectrum, and improving the accuracy of spectral analysis.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary spectral filtering of a hyperspectral camera, and in particular to a secondary spectral filtering method and system for a hyperspectral camera. Background Art

[0002] In a hyperspectral camera, when a grating is used for spectral separation, except for the zero-order spectrum line, the other spectra usually follow the order of short wave to long wave from the inside to the outside. According to the grating equation, starting from the secondary spectrum, there will be overlap between adjacent spectra, especially the short-wave part of the secondary spectrum and the long-wave part of the primary spectrum. This phenomenon is unacceptable in spectral analysis because it interferes with the analysis results. For example, in a hyperspectral camera operating in the wavelength range of 400-1000nm, the secondary spectrum of 400-500nm may overlap with the primary spectrum of 800-1000nm, thus affecting the accuracy of spectral analysis. Therefore, the secondary spectra in these overlapping areas must be eliminated.

[0003] At present, hyperspectral cameras on the market usually use a semi-coated long-wave pass filter installed in front of the detector to filter out the secondary spectrum. However, this method has two main problems: first, due to the limitations of the coating process, the edge of the semi-coated filter may cause unknown light scattering, resulting in distortion of the measured spectrum, which is not conducive to accurate spectral analysis; second, the use of filters will increase the production time and cost of the instrument. Therefore, it is necessary to find a new solution to effectively filter out the secondary spectrum while reducing the impact on spectral analysis and reducing production cycle and cost. Summary of the invention

[0004] In view of the problems in the related art, the present invention proposes a secondary spectral filtering method for a hyperspectral camera to overcome the above-mentioned technical problems existing in the existing related art.

[0005] To this end, the specific technical solution adopted by the present invention is as follows:

[0006] A secondary spectral filtering method for a hyperspectral camera, comprising:

[0007] S1: Based on the theoretical wavelength range and actual wavelength range that can be measured by the hyperspectral camera, the theoretical overlapping wavelength of the primary spectrum and the secondary spectrum is determined, and the actual wavelength range of the secondary spectrum in the overlapping area is obtained;

[0008] S2: Adjust the integration time, analyze the corresponding relationship between the primary spectrum intensity and the secondary spectrum intensity of each band in the actual wavelength range of the secondary spectrum in the overlapping area to obtain the relationship parameters, fill the relationship parameters into the characteristic matrix as characteristic parameters, and obtain the characteristic parameter matrix of the actual wavelength range of the secondary spectrum in the overlapping area;

[0009] S3: Interpolate the secondary spectrum data within the overlapping wavelength range based on the actual wavelength range of the secondary spectrum within the overlapping region and the characteristic parameter matrix.

[0010] S4: Filter out the secondary spectrum data from the original spectrum to obtain the final hyperspectral data.

[0011] Further, step S1 includes:

[0012] S1.1: Obtain the theoretical wavelength range and the actual wavelength range that can be measured by the hyperspectral camera, and determine the theoretical overlapping wavelength between the first-order spectrum and the secondary spectrum based on the diffraction theory.

[0013] S1.2: Use a monochromator to collect several wavelength segments of the theoretical overlapping wavelength between the first-order spectrum and the secondary spectrum, obtain the actual overlapping wavelength range between the secondary spectrum and the first-order spectrum for each wavelength segment and process it, and then perform fitting respectively to obtain several accurate first-order spectrum wavelengths and several accurate secondary spectrum wavelengths.

[0014] S1.3: Analyze the corresponding relationship between several accurate first-order spectrum wavelengths and several accurate secondary spectrum wavelengths, determine the final overlapping wavelength range between the secondary spectrum and the first-order spectrum, and obtain the actual wavelength range of the secondary spectrum within the overlapping region.

[0015] Further, in step S1.2, when processing the actual overlapping wavelength range between the secondary spectrum and the first-order spectrum for each wavelength segment, the dark background of the spectrum is deducted, and Gaussian fitting is used during fitting.

[0016] Further, step S2 includes:

[0017] S2.1: Use a band-pass filter and a broadband light source to adjust the integration time T 1 -T n , measure the average values of the first-order spectrum intensity and the secondary spectrum intensity at different integration times for each wavelength within the actual wavelength range of the secondary spectrum within the overlapping region, and obtain several groups of average first-order spectrum intensities and several groups of average secondary spectrum intensities.

[0018] S2.2: Fit several groups of average first-order spectrum intensities and several groups of average secondary spectrum intensities to obtain the relationship between the first-order spectrum intensity and the secondary spectrum intensity at this wavelength segment.

[0019] S2.3: Fill the wavelength and the parameters in its corresponding relationship as characteristic parameters into the characteristic matrix to obtain the characteristic parameter matrix of the actual wavelength range of the secondary spectrum within the overlapping region.

[0020] Further, S3 includes: performing dark background subtraction on the data collected by the hyperspectral camera, and generating corresponding secondary spectral data by interpolating according to the obtained primary spectral wavelength range, the secondary spectral wavelength range overlapping with the primary spectral wavelength range, and the characteristic parameter matrix.

[0021] Further, S4 includes: subtracting the secondary spectral data obtained in step S3 from the hyperspectral data after dark background subtraction to obtain the hyperspectral data after filtering the secondary spectrum as the final hyperspectral data.

[0022] A secondary spectrum filtering system for a hyperspectral camera, which is used to implement the secondary spectrum filtering method for a hyperspectral camera described in any one of the above, includes:

[0023] Actual wavelength range acquisition module for the secondary spectrum in the overlapping region: Based on the theoretical wavelength range and the actual wavelength range measurable by the hyperspectral camera, determine the theoretical overlapping wavelength of the primary spectrum and the secondary spectrum, and obtain the actual wavelength range of the secondary spectrum in the overlapping region;

[0024] Characteristic parameter matrix generation module: Adjust the integration time, analyze the corresponding relationship between the primary spectral intensity and the secondary spectral intensity in each band within the actual wavelength range of the secondary spectrum in the overlapping region to obtain the relationship parameters, and fill the relationship parameters into the characteristic matrix to obtain the characteristic parameter matrix of the actual wavelength range of the secondary spectrum in the overlapping region;

[0025] Secondary spectral data generation module: Generate secondary spectral data in the overlapping wavelength range by interpolating according to the actual wavelength range of the secondary spectrum in the overlapping region and the characteristic parameter matrix;

[0026] Secondary spectral data filtering module: Filter the secondary spectral data from the original spectrum to obtain the final hyperspectral data.

[0027] Further, the actual wavelength range acquisition module for the secondary spectrum in the overlapping region includes:

[0028] Theoretical overlapping wavelength determination module for the primary spectrum and the secondary spectrum: Obtain the theoretical wavelength range and the actual wavelength range measurable by the hyperspectral camera, and determine the theoretical overlapping wavelength of the primary spectrum and the secondary spectrum based on the diffraction theory;

[0029] Fitting module: Use a monochromator to collect several wavelength segments of the theoretical overlapping wavelength of the primary spectrum and the secondary spectrum, obtain the actual overlapping wavelength range of the secondary spectrum and the primary spectrum in each wavelength segment and perform processing, and then perform fitting respectively to obtain several accurate primary spectral wavelengths and several accurate secondary spectral wavelengths;

[0030] Secondary spectrum actual wavelength range acquisition module within the overlapping region: Analyze the correspondence between several accurate wavelengths of the primary spectrum and several accurate wavelengths of the secondary spectrum, determine the overlapping wavelength range between the final secondary spectrum and the primary spectrum, and obtain the actual wavelength range of the secondary spectrum within the overlapping region.

[0031] Furthermore, the characteristic parameter matrix generation module includes:

[0032] Average value calculation module: Utilize a band-pass filter and a broadband light source to adjust the integration time T 1 -T n , measure the average values of the primary spectrum intensity and the secondary spectrum intensity at different integration times for each wavelength within the actual wavelength range of the secondary spectrum in the overlapping region, and obtain several groups of average values of the primary spectrum intensity and several groups of average values of the secondary spectrum intensity;

[0033] Average value fitting module: Fit several groups of average values of the primary spectrum intensity and several groups of average values of the secondary spectrum intensity to obtain the relationship between the primary spectrum intensity and the secondary spectrum intensity in this wavelength range;

[0034] Characteristic parameter matrix analysis and generation module: Fill the wavelength and the parameters in its corresponding relationship into the characteristic matrix to obtain the characteristic parameter matrix of the actual wavelength range of the secondary spectrum in the overlapping region.

[0035] The beneficial effects of the present invention are as follows:

[0036] (1). The present application proposes a new method to filter the secondary spectrum in a hyperspectral camera, solving the problem of adjacent spectral overlap generated during grating spectroscopy. This method reduces or eliminates the interference of the secondary spectrum on the primary spectrum and improves the accuracy of spectral analysis;

[0037] (2). By avoiding the use of semi-coated filters, the present application reduces the spectral distortion caused by scattering at the coating edge, improves the accuracy of spectral analysis, and reduces the production cycle and cost of the hyperspectral camera, reducing the dependence on complex coating processes. Description of the Drawings

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the following described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0039] Figure 1 It is a flowchart of the steps of a method for filtering the secondary spectrum of a hyperspectral camera in Embodiment 1 of the present invention;

[0040] Figure 2It is a schematic diagram of measuring the first-order spectrum of a single wavelength and the corresponding second-order spectrum in a method for filtering the second-order spectrum of a hyperspectral camera according to Embodiment 1 of the present invention;

[0041] Figure 3 It is a relationship diagram between the wavelength of the second-order spectrum and the wavelength of the first-order spectrum obtained by fitting in a method for filtering the second-order spectrum of a hyperspectral camera according to Embodiment 1 of the present invention;

[0042] Figure 4 It is a schematic diagram of measuring the first-order spectrum and the corresponding second-order spectrum using a band-pass filter and a broadband light source in a method for filtering the second-order spectrum of a hyperspectral camera according to Embodiment 1 of the present invention;

[0043] Figure 5 It is a relationship diagram between the intensity of the second-order spectrum and the intensity of the first-order spectrum corresponding to the wavelength of Channel 1 at different integration times obtained by fitting in a method for filtering the second-order spectrum of a hyperspectral camera according to Embodiment 1 of the present invention;

[0044] Figure 6 It is a relationship diagram between the intensity of the second-order spectrum and the intensity of the first-order spectrum corresponding to the wavelength of Channel 50 at different integration times obtained by fitting in a method for filtering the second-order spectrum of a hyperspectral camera according to Embodiment 1 of the present invention;

[0045] Figure 7 It is an effect diagram of filtering the second-order spectrum in a method for filtering the second-order spectrum of a hyperspectral camera according to Embodiment 1 of the present invention. Detailed implementation manners

[0046] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with 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. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Embodiment 1

[0047] According to an embodiment of the present invention, a method for filtering the second-order spectrum of a hyperspectral camera is provided, as Figures 1-7 shown, including:

[0048] S1: Based on the theoretical wavelength range and the actual wavelength range measurable by the hyperspectral camera, determine the theoretical overlapping wavelength of the first-order spectrum and the second-order spectrum, and obtain the actual wavelength range of the second-order spectrum within the overlapping region. Specifically:

[0049] S1.1: Obtain the theoretical wavelength range of 400 - 1000 nm that the hyperspectral camera can measure and the actual wavelength range of 376 - 1021 nm. Based on the diffraction theory and the hyperspectral camera design method, preliminarily determine that the wavelength range of the second-order spectrum overlapping within the hyperspectral detection range of 400 - 1000 nm is 400 - 500 nm, which overlaps with the first-order spectrum in the range of 800 - 1000 nm. Since the theoretical wavelength range of the first-order spectrum corresponding to the second-order spectrum wavelength falling within the actual wavelength range of 385.6 - 521.9 nm should be 188 - 511 nm, but the actual camera starts from the 376 nm band, so 376 nm is used as the starting point of the band range, that is, the theoretical overlapping wavelength of the first-order spectrum and the second-order spectrum is 385.6 - 521.9 nm;

[0050] S1.2: As Figure 2 shown, use a monochromator to collect several wavelength segments within 385.6 - 521.9 nm, obtain the overlapping wavelength range of the actual second-order spectrum and the first-order spectrum for each wavelength segment and perform dark background subtraction processing on the spectrum. The processed curve is first peak-searched, as Figure 3 shown, and then the Gaussian function is used to fit the first-order spectrum and the second-order spectrum respectively to obtain the center positions, and several accurate wavelengths of the first-order spectrum and several accurate wavelengths of the second-order spectrum are obtained;

[0051] S1.3: Analyze the corresponding relationship between several accurate wavelengths of the first-order spectrum and several accurate wavelengths of the second-order spectrum, determine the overlapping wavelength of the first-order spectrum and the second-order spectrum as 751.4 - 1021.7 nm, and obtain the actual wavelength range of the second-order spectrum within the overlapping region as 385.6 - 521.9 nm.

[0052] S2: Adjust the integration time. Within the actual wavelength range of the second-order spectrum of 385.6 - 521.9 nm in the overlapping region, analyze the corresponding relationship between the first-order spectrum intensity and the second-order spectrum intensity for each band to obtain the relationship parameter, and fill the relationship parameter into the feature matrix as the feature parameter to obtain the feature parameter matrix of the actual wavelength range of the second-order spectrum within the overlapping region;

[0053] Step S2 includes:

[0054] S2.1: As Figure 4 shown, use a band-pass filter and a broadband light source to adjust the integration time T 1 -T n , measure the average values of the first-order spectrum intensity and the second-order spectrum intensity at different integration times for each wavelength within the actual wavelength range of the second-order spectrum in the overlapping region, and obtain several groups of average values of the first-order spectrum intensity I 1n and several groups of average values of the second-order spectrum intensity I 2n , as shown in the following table:

[0055]

[0056] S2.2: Because the data is accidental, the average values of the primary spectral intensity and the secondary spectral intensity are taken, and the average value is fitted to obtain I in this wavelength band 1n and I 2n The linear relationship formula of, that is, to find: . The function represented by f can be a linear function, a quadratic function, etc. For example Figure 5 and 6 As shown, it is assumed to be a linear relationship here, so the fitting relationship formula becomes: , using the least squares method for fitting, the slope a and the intercept b are obtained by fitting (if it is a quadratic function, the parameters a, b, and c are obtained by fitting), as shown in the following table:

[0057]

[0058] S2.3: And fill the wavelength, slope, and intercept into the feature matrix as eigenvalues to obtain the feature parameter matrix, as shown in the following table:

[0059]

[0060] S3: Perform dark background subtraction on the data obtained by the hyperspectral camera each time. According to the obtained primary spectral wavelength range and the secondary spectral wavelength range overlapping with the primary spectral wavelength range, and the feature parameter matrix, interpolate to generate the corresponding secondary spectral data. According to the position of each wavelength in the feature matrix, extract the corresponding feature parameters, and generate the corresponding values according to the actually collected primary spectrum of the hyperspectral, to generate the corresponding secondary spectral data. However, in practice, according to the linear correspondence relationship between the primary spectrum and the secondary spectrum fitted by us, the secondary spectral wavelength may not exactly correspond to the band of the hyperspectral camera. For example, the secondary spectral wavelength corresponding to 385.6nm may fall between the central wavelengths of two bands. Therefore, we perform linear interpolation on the obtained secondary spectral data to satisfy the acquisition of the secondary spectral data corresponding to the integer band corresponding to the hyperspectral band.

[0061] S4: Subtract the secondary spectral data obtained in step S3 from the hyperspectral data after dark background subtraction to obtain the hyperspectral data after filtering the secondary spectrum as the final hyperspectral data. As Figure 7 Shown, the method of this application is used for secondary spectrum filtering. The dotted line in the figure is: the original spectral data without filtering; the dotted line with dots is: the generated secondary spectral data; the straight line is: the clean hyperspectral data after filtering the secondary spectrum.

[0062] In summary, using the method of this application to filter the secondary spectrum in the hyperspectral camera can solve the problem of adjacent spectral overlap generated during grating spectroscopy. This method reduces or eliminates the interference of the secondary spectrum on the primary spectrum and improves the accuracy of spectral analysis. Embodiment 2

[0063] A secondary spectrum filtering system for a hyperspectral camera, which is used to implement the secondary spectrum filtering method for a hyperspectral camera in Embodiment 1, includes:

[0064] A module for obtaining the actual wavelength range of the secondary spectrum in the overlapping region: Based on the theoretical wavelength range and the actual wavelength range measurable by the hyperspectral camera, determine the theoretical overlapping wavelength of the primary spectrum and the secondary spectrum, and obtain the actual wavelength range of the secondary spectrum in the overlapping region;

[0065] A characteristic parameter matrix generation module: Adjust the integration time, analyze the corresponding relationship between the intensity of the primary spectrum and the intensity of the secondary spectrum in each band within the actual wavelength range of the secondary spectrum in the overlapping region to obtain relationship parameters, fill the relationship parameters into the characteristic matrix as characteristic parameters, and obtain the characteristic parameter matrix of the actual wavelength range of the secondary spectrum in the overlapping region;

[0066] A secondary spectrum data generation module: Interpolate according to the actual wavelength range of the secondary spectrum in the overlapping region and the characteristic parameter matrix to generate secondary spectrum data in the overlapping wavelength range;

[0067] A secondary spectrum data filtering module: Filter the secondary spectrum data from the original spectrum to obtain the final hyperspectral data.

[0068] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A secondary spectrum filtering method for a hyperspectral camera, characterized in that: include: S1: Based on the theoretical wavelength range and actual wavelength range that can be measured by the hyperspectral camera, the theoretical overlapping wavelength of the primary spectrum and the secondary spectrum is determined based on the diffraction theory, and the actual wavelength range of the secondary spectrum in the overlapping area is obtained; S2: Adjust the integration time, analyze the corresponding relationship between the primary spectrum intensity and the secondary spectrum intensity of each band in the actual wavelength range of the secondary spectrum in the overlapping area to obtain the relationship parameters, fill the relationship parameters into the characteristic matrix as characteristic parameters, and obtain the characteristic parameter matrix of the actual wavelength range of the secondary spectrum in the overlapping area, including: S2.1: Adjust the integration time T1-T n , measuring the average values ​​of the primary spectrum intensity and the secondary spectrum intensity at different integration times at each wavelength within the actual wavelength range of the secondary spectrum in the overlapping region, and obtaining several groups of primary spectrum intensity average values ​​and several groups of secondary spectrum intensity average values; S2.2: Fitting several groups of average primary spectrum intensities and several groups of average secondary spectrum intensities to obtain a relationship between the primary spectrum intensity and the secondary spectrum intensity in any wavelength band within the actual wavelength range of the secondary spectrum in the overlapping region; S2.3: Fill the wavelength and the parameters in the corresponding relationship as characteristic parameters into the characteristic matrix to obtain the characteristic parameter matrix of the actual wavelength range of the secondary spectrum in the overlapping area; S3: according to the position of each wavelength in the characteristic matrix, extract the characteristic parameters corresponding to the actual wavelength range of the secondary spectrum in the overlapping area, and perform linear interpolation on the characteristic parameters to generate secondary spectrum data of the overlapping wavelength range; S4: Filter out the secondary spectrum data from the original spectrum to obtain the final hyperspectral data.

2. The secondary spectrum filtering method for a hyperspectral camera according to claim 1, characterized in that: Step S1 includes: S1.1: Obtain the theoretical wavelength range and actual wavelength range that can be measured by the hyperspectral camera, and determine the theoretical overlapping wavelength of the primary spectrum and the secondary spectrum based on the diffraction theory; S1.2: Collect several wavelength bands of theoretical overlapping wavelengths of the primary spectrum and the secondary spectrum, obtain the overlapping wavelength range of the actual secondary spectrum and the primary spectrum in each wavelength band and process them, and then perform fitting to obtain several precise wavelengths of the primary spectrum and several precise wavelengths of the secondary spectrum; S1.3: Analyze the correspondence between several precise wavelengths of the primary spectra and several precise wavelengths of the secondary spectra, determine the overlapping wavelength range of the final secondary spectrum and the primary spectrum, and obtain the actual wavelength range of the secondary spectrum in the overlapping area.

3. The secondary spectrum filtering method for a hyperspectral camera according to claim 2, characterized in that: In step S1.2, the dark background of the spectrum is deducted when processing the overlapping wavelength range of the actual secondary spectrum and the primary spectrum of each wavelength band, and Gaussian fitting is used for fitting.

4. The secondary spectrum filtering method for a hyperspectral camera according to claim 1, characterized in that: S4 includes: deducting the secondary spectrum data obtained in step S3 from the hyperspectral data after deducting the dark background, and obtaining the hyperspectral data after filtering out the secondary spectrum as the final hyperspectral data.

5. A secondary spectral filtering system for a hyperspectral camera, used to implement the secondary spectral filtering method for a hyperspectral camera described in any one of claims 1 to 4, characterized in that: include: The module for acquiring the actual wavelength range of the secondary spectrum in the overlapping area: based on the theoretical wavelength range and actual wavelength range that can be measured by the hyperspectral camera, the theoretical overlapping wavelength of the primary spectrum and the secondary spectrum is determined based on the diffraction theory, and the actual wavelength range of the secondary spectrum in the overlapping area is obtained; Characteristic parameter matrix generation module: adjust the integration time, analyze the corresponding relationship between the primary spectrum intensity and the secondary spectrum intensity of each band in the actual wavelength range of the secondary spectrum in the overlapping area to obtain the relationship parameters, fill the relationship parameters into the characteristic matrix as characteristic parameters, and obtain the characteristic parameter matrix of the actual wavelength range of the secondary spectrum in the overlapping area, including: Adjust the integration time T1-T n , measuring the average values ​​of the primary spectrum intensity and the secondary spectrum intensity at different integration times at each wavelength within the actual wavelength range of the secondary spectrum in the overlapping region, and obtaining several groups of primary spectrum intensity average values ​​and several groups of secondary spectrum intensity average values; The average values ​​of several groups of primary spectrum intensities and the average values ​​of several groups of secondary spectrum intensities are fitted to obtain the relationship between the primary spectrum intensity and the secondary spectrum intensity in any wavelength band within the actual wavelength range of the secondary spectrum in the overlapping area; Fill the wavelength and the parameters in the corresponding relationship as characteristic parameters into the characteristic matrix to obtain the characteristic parameter matrix of the actual wavelength range of the secondary spectrum in the overlapping area; Secondary spectrum data generation module: according to the position of each wavelength in the characteristic matrix, the characteristic parameters corresponding to the actual wavelength range of the secondary spectrum in the overlapping area are extracted, and the characteristic parameters are linearly interpolated to generate the secondary spectrum data of the overlapping wavelength range; Secondary spectral data filtering module: filter out secondary spectral data from the original spectrum to obtain the final hyperspectral data.

6. The secondary spectral filtering system for a hyperspectral camera according to claim 5, characterized in that: The module for acquiring the actual wavelength range of the secondary spectrum in the overlapping area includes: Obtain the theoretical wavelength range and actual wavelength range that can be measured by the hyperspectral camera, and determine the theoretical overlapping wavelength of the primary spectrum and the secondary spectrum based on diffraction theory; Collecting several wavelength bands of theoretical overlapping wavelengths of the primary spectrum and the secondary spectrum, obtaining the overlapping wavelength range of the actual secondary spectrum and the primary spectrum in each wavelength band and processing them, and then fitting them to obtain several precise wavelengths of the primary spectrum and several precise wavelengths of the secondary spectrum; The corresponding relationship between several precise wavelengths of the primary spectra and several precise wavelengths of the secondary spectra is analyzed, the overlapping wavelength range of the final secondary spectrum and the primary spectrum is determined, and the actual wavelength range of the secondary spectrum in the overlapping area is obtained.

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