CN117168619A - Spectrum calibration method and system for satellite-borne hyperspectral imager - Google Patents
Spectrum calibration method and system for satellite-borne hyperspectral imager Download PDFInfo
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Abstract
The invention provides a spectrum calibration method and a system for a satellite-borne hyperspectral imager, which belong to the technical field of remote sensing optics and comprise the following steps: acquiring relative spectral irradiance distribution of the to-be-calibrated satellite-borne hyperspectral imager by monochromatic parallel light irradiation of a monochromator, and acquiring calibration images of the to-be-calibrated satellite-borne hyperspectral imager; obtaining a plurality of calibration images according to the starting wavelength and the ending wavelength of the satellite-borne hyperspectral imager to be calibrated; determining the corresponding row number of each center wavelength and the maximum value in the calibration images by utilizing a plurality of calibration images; calculating a relative spectral response function of the satellite-borne hyperspectral imager to be calibrated based on the relative spectral irradiance distribution, the plurality of calibration images and the row numbers corresponding to the maximum values; and determining half-maximum full waves corresponding to each center wavelength of the satellite-borne hyperspectral imager to be calibrated according to the relative spectral response function. The invention obtains the spectrum calibration parameters necessary for quantitative application of the remote sensing satellite, and fills the blank of the spectrum calibration method of the linear gradient filter type hyperspectral imager.
Description
Technical Field
The invention relates to the technical field of remote sensing optics, in particular to a spectrum calibration method and system of a satellite-borne hyperspectral imager.
Background
The remote sensing spaceborne hyperspectral imager generally has tens to hundreds of spectral channels, the spectral resolution of the remote sensing spaceborne hyperspectral imager can reach the order of one percent of the central wavelength, and the remote sensing spaceborne hyperspectral imager has the advantages of large information quantity, good recognition effect and the like. In the present stage, several spectrum spectroscopic methods are commonly used, including dispersive, interferometric, and optical filters. Compared with the dispersion type or the interference type, the optical filter type has the advantages of compact optical path, less number of optical components contained in the optical system, light weight and controllable cost. The linear graded filter type has the following two remarkable advantages: the number of the spectrum channels is large, and can reach tens to hundreds in general; the spectrum resolution is high, which is generally better than 10nm, so the method has wide application.
The existing spectrum calibration method of the hyperspectral imager lacks a calibration flow of the corresponding relation between the center wavelength and the position of the imaging device, and the measurement and calculation of the relative spectrum response function do not relate to the situation that the number of spectrum channels is large and the center wavelength is variable. Therefore, the existing method is suitable for a dispersion type or interference type hyperspectral imager, but cannot meet the requirements of a linear gradient filter type hyperspectral imager with multiple spectral channels and variable channel centers and widths.
Therefore, a new spectrum calibration method is required to be proposed for the linear graded filter type hyperspectral imager.
Disclosure of Invention
The invention provides a spectrum calibration method and a system for a satellite-borne hyperspectral imager, which are used for solving the defect that the spectrum calibration method for a linear gradient filter hyperspectral imager is lacking in the prior art.
In a first aspect, the present invention provides a method for spectral calibration of an on-board hyperspectral imager, comprising:
s1, acquiring the preset number of dark background image data of a satellite-borne hyperspectral imager to be calibrated in a dark background imaging mode;
s2, acquiring the relative spectral irradiance distribution of the to-be-calibrated satellite-borne hyperspectral imager by monochromatic parallel light irradiation of the monochromator, and acquiring a calibration image of the to-be-calibrated satellite-borne hyperspectral imager;
s3, obtaining a plurality of calibration images from the initial wavelength and the termination wavelength of the satellite-borne hyperspectral imager to be calibrated;
s4, determining the row number corresponding to the maximum value in each center wavelength and the calibration images by utilizing the plurality of calibration images;
s5, calculating a relative spectral response function of the satellite-borne hyperspectral imager to be calibrated based on the relative spectral irradiance distribution, the plurality of calibration images and the row numbers corresponding to the maximum values;
and S6, determining half-maximum full waves corresponding to each center wavelength of the satellite-borne hyperspectral imager to be calibrated according to the relative spectral response function.
According to the spectral calibration method of the satellite-borne hyperspectral imager provided by the invention, the step S1 is preceded by the following steps:
and obtaining the original device parameters of the satellite-borne hyperspectral imager to be calibrated.
According to the spectrum calibration method of the satellite-borne hyperspectral imager provided by the invention, the step S2 comprises the following steps:
the monochromator outputs monochromatic light after receiving a broad-spectrum illumination light source;
the monochromatic light is irradiated through a collimator to obtain monochromatic parallel light;
the monochromatic parallel light irradiates the satellite-borne hyperspectral imager to be calibrated to obtain the relative spectral irradiance distribution;
and acquiring and measuring the relative spectral irradiance distribution with preset times to obtain the calibration image.
According to the spectrum calibration method of the satellite-borne hyperspectral imager provided by the invention, the step S3 comprises the following steps:
and (2) repeating the step (S2) with the preset central wavelength change step of the monochromator from the initial wavelength of the to-be-calibrated satellite-borne hyperspectral imager until the final wavelength of the to-be-calibrated satellite-borne hyperspectral imager is reached, so as to obtain the plurality of calibration images.
According to the spectrum calibration method of the satellite-borne hyperspectral imager provided by the invention, the step S4 comprises the following steps:
s401, determining any central wavelength calibration image in the plurality of calibration images, calculating an average remote sensing image pixel brightness value of the any central wavelength calibration image row by row, extracting a row number corresponding to a maximum value in the average remote sensing image pixel brightness value, and determining any central wavelength output row based on the row number corresponding to the maximum value;
and S402, repeating the step S401 one by one according to the central wavelength, and obtaining the central wavelength output rows corresponding to different central wavelengths through least square fitting.
According to the spectrum calibration method of the satellite-borne hyperspectral imager provided by the invention, the step S5 comprises the following steps:
s501, calculating the ratio of the pixel brightness value of the average remote sensing image of any central wavelength calibration image to the relative spectral irradiance distribution of the corresponding monochromatic light, dividing the ratio by the maximum value of the ratio between the lower limit of the wavelength of any central wavelength spectral channel and the upper limit of the wavelength of any central wavelength spectral channel, and obtaining the relative spectral response function of any central wavelength;
s502, fitting the relative spectral response function of any central wavelength spectral channel by adopting a least square method to obtain the relative spectral response function of the satellite-borne hyperspectral imager to be calibrated in any central wavelength corresponding spectral channel;
and S503, repeating the step S501 and the step S502 one by one according to the central wavelength, and obtaining the relative spectral response functions of the spectral channels corresponding to different central wavelengths.
According to the spectrum calibration method of the satellite-borne hyperspectral imager provided by the invention, the step S6 comprises the following steps:
s601, determining a short wave wavelength which is one half of the peak response in a relative spectral response function of any central wavelength corresponding to a spectral channel and is positioned at a short wave, and a long wave wavelength which is positioned at a long wave, and subtracting the short wave wavelength from the long wave wavelength to obtain a half-maximum full wave of any central wavelength corresponding to the spectral channel;
s602, repeating the step S601 one by one according to the central wavelength, and obtaining half-maximum full waves of the spectrum channels corresponding to different central wavelengths.
In a second aspect, the present invention also provides a spectral scaling system for a satellite-borne hyperspectral imager, comprising:
the acquisition module is used for acquiring the preset number of dark background image data of the satellite-borne hyperspectral imager to be calibrated in a dark background imaging mode;
the acquisition module is used for acquiring the relative spectral irradiance distribution of the to-be-calibrated satellite-borne hyperspectral imager through monochromatic parallel light irradiation of the monochromator and acquiring a calibration image of the to-be-calibrated satellite-borne hyperspectral imager;
the calibration module is used for obtaining a plurality of calibration images from the starting wavelength and the ending wavelength of the satellite-borne hyperspectral imager to be calibrated;
the determining module is used for determining the row number corresponding to the maximum value in each center wavelength and the calibration images by utilizing the plurality of calibration images;
the calculation module is used for calculating the relative spectral response function of the satellite-borne hyperspectral imager to be calibrated based on the relative spectral irradiance distribution, the plurality of calibration images and the row numbers corresponding to the maximum values;
and the comprehensive module is used for determining half-maximum full waves corresponding to each center wavelength of the satellite-borne hyperspectral imager to be calibrated according to the relative spectral response function.
In a third aspect, the invention also provides an electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing any one of the above-mentioned on-board hyperspectral imager spectral scaling methods when executing the program.
In a fourth aspect, the invention also provides a non-transitory computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements a method of spectral scaling of a satellite borne hyperspectral imager as described in any one of the above.
According to the spectrum calibration method and system for the satellite-borne hyperspectral imager, provided by the invention, the blank of the spectrum calibration method for the linear gradient filter hyperspectral imager is filled by obtaining the spectrum calibration parameters required by quantitative application of a remote sensing satellite, so that phenomena such as overexposure and the like in the process of acquiring calibration image data are avoided, and the effectiveness of calibration data is ensured; accidental errors are avoided through multiple collection and calculation, accuracy of calibration data is guaranteed, the central wavelength change step is adopted, the number of repeated operation is reduced, and spectrum calibration efficiency is improved; common optical analysis instruments such as parallel light pipes, broad-spectrum illumination light sources and the like are used in the calibration process, so that the difficulty of spectral calibration in a laboratory is reduced. Therefore, the laboratory spectrum calibration parameters obtained by the method are important bases for carrying out laboratory absolute radiometric calibration and satellite on-orbit substitution calibration before emission, and have important significance for quantitative application of hyperspectral remote sensing satellites.
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In order to more clearly illustrate the invention or the technical solutions of the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the invention, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic flow chart of a spectral calibration method of a satellite-borne hyperspectral imager provided by the invention;
FIG. 2 is a second flow chart of the spectral calibration method of the satellite-borne hyperspectral imager provided by the invention;
FIG. 3 is a schematic diagram of the spectral calibration system of the satellite-borne hyperspectral imager provided by the invention;
fig. 4 is a schematic structural diagram of an electronic device provided by the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Because of the general lack of a spectrum calibration method for a linear gradient filter type hyperspectral imager in the prior art, the invention develops a complete laboratory spectrum calibration method.
Fig. 1 is a schematic flow chart of a spectrum calibration method of a satellite-borne hyperspectral imager according to an embodiment of the present invention, as shown in fig. 1, including:
s1, acquiring the preset number of dark background image data of a satellite-borne hyperspectral imager to be calibrated in a dark background imaging mode;
s2, acquiring the relative spectral irradiance distribution of the to-be-calibrated satellite-borne hyperspectral imager by monochromatic parallel light irradiation of the monochromator, and acquiring a calibration image of the to-be-calibrated satellite-borne hyperspectral imager;
s3, obtaining a plurality of calibration images from the initial wavelength and the termination wavelength of the satellite-borne hyperspectral imager to be calibrated;
s4, determining the row number corresponding to the maximum value in each center wavelength and the calibration images by utilizing the plurality of calibration images;
s5, calculating a relative spectral response function of the satellite-borne hyperspectral imager to be calibrated based on the relative spectral irradiance distribution, the plurality of calibration images and the row numbers corresponding to the maximum values;
and S6, determining half-maximum full waves corresponding to each center wavelength of the satellite-borne hyperspectral imager to be calibrated according to the relative spectral response function.
Specifically, as shown in fig. 2, the embodiment of the present invention first makes the to-be-determined high-spectrum imager work in a dark background imaging mode, and collects dark background image data for several times, for example, 50 times, for eliminating background noise generated by the high-spectrum imager due to dark current;
the monochromatic light is output from a broad spectrum illumination light source through a monochromator and passes through a collimatorIlluminating a target elevation spectral imager, measuring relative spectral irradiance distribution of monochromatic parallel light using a spectral radiometerCollecting a calibration image output by a spectrum imager with a to-be-calibrated elevation;
starting from the initial wavelength of the spectrum imager with the elevation to be determined, taking 1nm as the variation step distance of the output center wavelength of the monochromator, and repeating the steps until reaching the final wavelength of the spectrum imager with the elevation to be determined;
determining the line number corresponding to the maximum value on each center wavelength and the calibration image thereof by utilizing the image of the spectrum imager to be calibrated acquired in the previous step;
and then the image and relative spectral irradiance distribution of the spectrum imager with the target elevation acquired in the previous step are utilizedCalculating a relative spectral response function of the to-be-determined elevation spectrum imager;
and finally, according to the obtained relative spectral response function, determining half maximum full wave (Full Width at Half Maximum, FWHM) corresponding to each center wavelength.
The invention designs a laboratory spectrum calibration method aiming at the characteristics of multiple spectrum channels and variable channel centers and widths of the linear gradient filter type hyperspectral imager, can obtain spectrum calibration parameters necessary for quantitative application of remote sensing satellites, and fills the blank of the spectrum calibration method of the linear gradient filter type hyperspectral imager.
On the basis of the above embodiment, step S1 further includes:
and obtaining the original device parameters of the satellite-borne hyperspectral imager to be calibrated.
Specifically, before formal calibration, many original device parameters of the linear gradient filter hyperspectral imager, such as spectrum calibration parameters of bandpass transmittance, etc., need to be acquired.
On the basis of the above embodiment, step S2 includes:
the monochromator outputs monochromatic light after receiving a broad-spectrum illumination light source;
the monochromatic light is irradiated through a collimator to obtain monochromatic parallel light;
the monochromatic parallel light irradiates the satellite-borne hyperspectral imager to be calibrated to obtain the relative spectral irradiance distribution;
and acquiring and measuring the relative spectral irradiance distribution with preset times to obtain the calibration image.
Specifically, monochromatic light is output from a broad-spectrum illumination light source through a monochromator, and then a collimator irradiates a spectrum imager to be positioned. Measuring relative spectral irradiance distribution of monochromatic parallel light using a spectral radiometerAt least 50 measurements should be made each time, and at least 50 calibration images output by the to-be-calibrated elevation spectrum imager should be acquired.
The setting method of the imaging parameters of the hyperspectral imager can avoid overexposure and other phenomena in the process of acquiring the calibration image data, and ensure the effectiveness of the calibration data; accidental errors are avoided through multiple collection and calculation, and accuracy of calibration data is ensured.
On the basis of the above embodiment, step S3 includes:
and (2) repeating the step (S2) with the preset central wavelength change step of the monochromator from the initial wavelength of the to-be-calibrated satellite-borne hyperspectral imager until the final wavelength of the to-be-calibrated satellite-borne hyperspectral imager is reached, so as to obtain the plurality of calibration images.
Specifically, in the embodiment of the invention, for a scene covering all wavelength bands, setting is performed from the initial wavelength of the to-be-determined elevation spectrum imager, and step S2 is repeated according to the preset central wavelength change step, usually 1nm, as the change step of the output central wavelength of the monochromator until the final wavelength of the to-be-determined elevation spectrum imager is reached.
According to the laboratory spectrum calibration method designed by the invention, 1nm is used as the variation step of the output center wavelength of the monochromator, so that the number of repeated operation is reduced, and the spectrum calibration efficiency is improved; common optical analysis instruments such as parallel light pipes, broad-spectrum illumination light sources and the like are used in the calibration process, so that the difficulty of spectral calibration in a laboratory is reduced.
On the basis of the above embodiment, step S4 includes:
s401, determining any central wavelength calibration image in the plurality of calibration images, calculating an average remote sensing image pixel brightness value of the any central wavelength calibration image row by row, extracting a row number corresponding to a maximum value in the average remote sensing image pixel brightness value, and determining any central wavelength output row based on the row number corresponding to the maximum value;
and S402, repeating the step S401 one by one according to the central wavelength, and obtaining the central wavelength output rows corresponding to different central wavelengths through least square fitting.
Specifically, the embodiment of the invention determines the line number corresponding to the maximum value on each center wavelength and the calibration image thereof by using the images of the to-be-calibrated elevation spectrum imager acquired in the steps S2 and S3, and specifically comprises the following steps:
s401, taking the center wavelength asCalculating pixel brightness value (Digital Number, DN) of the average remote sensing image line by line, comparing the average DN value, and taking the line with the maximum average DN value as the center wavelength +.>Output line +.>；
S402, repeating the step S401 for each center wavelength to obtain output rows corresponding to different center wavelengthsThe method comprises the steps of carrying out a first treatment on the surface of the And the relation between the two is obtained through least square fitting:
= P（/>）
the imaging device position corresponding to any center wavelength can be calculated by utilizing the relation.
On the basis of the above embodiment, step S5 includes:
s501, calculating the ratio of the pixel brightness value of the average remote sensing image of any central wavelength calibration image to the relative spectral irradiance distribution of the corresponding monochromatic light, dividing the ratio by the maximum value of the ratio between the lower limit of the wavelength of any central wavelength spectral channel and the upper limit of the wavelength of any central wavelength spectral channel, and obtaining the relative spectral response function of any central wavelength;
s502, fitting the relative spectral response function of any central wavelength spectral channel by adopting a least square method to obtain the relative spectral response function of the satellite-borne hyperspectral imager to be calibrated in any central wavelength corresponding spectral channel;
and S503, repeating the step S501 and the step S502 one by one according to the central wavelength, and obtaining the relative spectral response functions of the spectral channels corresponding to different central wavelengths.
Specifically, the embodiment of the invention uses the images and the relative spectral irradiance distribution of the to-be-localized elevation spectral imager acquired in the steps S2 and S3The method for calculating the relative spectral response function of the to-be-determined elevation spectrum imager specifically comprises the following steps:
s501, calculating a relative spectral response function R (lambda) of a current spectral channel of the to-be-determined elevation spectral imager according to the following formula according to the relative spectral irradiance distribution of monochromatic parallel light:
R（λ） =
where λ is the center wavelength, R (λ) is the corresponding normalized spectral response, DN (λ) is the corresponding output DN value, the average DN value of all pixels on each row is taken as the output DN value, RL (λ) is the relative spectral irradiance distribution of the corresponding monochromatic light,for the spectral imaging device with the elevation to be determined, the lower wavelength limit of the spectral channel is +.>The upper limit of the wavelength of the spectrum channel is the spectrum imager with the elevation to be determined;
s502, fitting by using a least square method to obtain a relative spectral response function R (lambda) of the spectral channel of the spectrum imager with the elevation to be determined;
and S503, repeating the steps S501 and S502 for each center wavelength to obtain a relative spectral response function R (lambda) corresponding to different center wavelengths.
On the basis of the above embodiment, step S6 includes:
s601, determining a short wave wavelength which is one half of the peak response in a relative spectral response function of any central wavelength corresponding to a spectral channel and is positioned at a short wave, and a long wave wavelength which is positioned at a long wave, and subtracting the short wave wavelength from the long wave wavelength to obtain a half-maximum full wave of any central wavelength corresponding to the spectral channel;
s602, repeating the step S601 one by one according to the central wavelength, and obtaining half-maximum full waves of the spectrum channels corresponding to different central wavelengths.
Specifically, according to the relative spectral response function calculated in step S5, the embodiment of the present invention determines the FWHM corresponding to each center wavelength, which specifically includes:
s601, center wavelengthThe relative spectral response function of (2) is R (>) The response value is one half of the peak response and the wavelength at the short wave is recorded as +.>The wavelength at the long wave is marked +.>The half-wave width FWHM at this time can be calculated by:
FWHM =-/>
and S602, repeating the step S601 for each center wavelength, and obtaining FWHM corresponding to different center wavelengths.
The laboratory spectrum calibration parameters obtained in the invention are important bases for carrying out laboratory absolute radiometric calibration and satellite on-orbit substitution calibration before emission later, and have important significance for quantitative application of hyperspectral remote sensing satellites.
The spectrum calibration system of the satellite-borne hyperspectral imager provided by the invention is described below, and the spectrum calibration system of the satellite-borne hyperspectral imager described below and the spectrum calibration method of the satellite-borne hyperspectral imager described above can be correspondingly referred to each other.
Fig. 3 is a schematic structural diagram of a spectrum calibration system of a satellite-borne hyperspectral imager according to an embodiment of the present invention, as shown in fig. 3, including: the device comprises an acquisition module 31, an acquisition module 32, a calibration module 33, a determination module 34, a calculation module 35 and a synthesis module 36, wherein:
the acquisition module 31 is used for acquiring the preset number of dark background image data of the satellite-borne hyperspectral imager to be calibrated in a dark background imaging mode; the acquisition module 32 is configured to acquire a relative spectral irradiance distribution of the to-be-calibrated on-board hyperspectral imager by monochromatic parallel light irradiation of the monochromator, and acquire a calibration image of the to-be-calibrated on-board hyperspectral imager; the calibration module 33 is configured to obtain a plurality of calibration images from the start wavelength and the end wavelength of the to-be-calibrated on-board hyperspectral imager; the determining module 34 is configured to determine, using the plurality of calibration images, a line number corresponding to a maximum value in each of the center wavelengths and the calibration images; the calculating module 35 is configured to calculate a relative spectral response function of the to-be-calibrated on-board hyperspectral imager based on the relative spectral irradiance distribution, the plurality of calibration images, and the row numbers corresponding to the maximum values; the synthesis module 36 is configured to determine a half-maximum full-wave corresponding to each center wavelength of the to-be-calibrated spaceborne hyperspectral imager according to the relative spectral response function.
Fig. 4 illustrates a physical schematic diagram of an electronic device, as shown in fig. 4, which may include: processor 410, communication interface (Communications Interface) 420, memory 430 and communication bus 440, wherein processor 410, communication interface 420 and memory 430 communicate with each other via communication bus 440. The processor 410 may invoke logic instructions in the memory 430 to perform a method of spectral scaling of an on-board hyperspectral imager, the method comprising: acquiring the preset number of dark background image data of the satellite-borne hyperspectral imager to be calibrated in a dark background imaging mode; acquiring the relative spectral irradiance distribution of the to-be-calibrated satellite-borne hyperspectral imager by monochromatic parallel light irradiation of a monochromator, and acquiring a calibration image of the to-be-calibrated satellite-borne hyperspectral imager; obtaining a plurality of calibration images according to the starting wavelength and the ending wavelength of the satellite-borne hyperspectral imager to be calibrated; determining a row number corresponding to the maximum value in each center wavelength and the calibration images by utilizing the plurality of calibration images; calculating a relative spectral response function of the to-be-calibrated satellite-borne hyperspectral imager based on the relative spectral irradiance distribution, the plurality of calibration images and the row numbers corresponding to the maximum values; and determining half maximum full waves corresponding to each center wavelength of the satellite-borne hyperspectral imager to be calibrated according to the relative spectral response function.
Further, the logic instructions in the memory 430 described above may be implemented in the form of software functional units and may be stored in a computer-readable storage medium when sold or used as a stand-alone product. Based on this understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution, in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a personal computer, a server, a network device, etc.) to perform all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
In another aspect, the present invention also provides a non-transitory computer readable storage medium having stored thereon a computer program which, when executed by a processor, is implemented to perform the method for spectral scaling of a satellite borne hyperspectral imager provided by the methods described above, the method comprising: acquiring the preset number of dark background image data of the satellite-borne hyperspectral imager to be calibrated in a dark background imaging mode; acquiring the relative spectral irradiance distribution of the to-be-calibrated satellite-borne hyperspectral imager by monochromatic parallel light irradiation of a monochromator, and acquiring a calibration image of the to-be-calibrated satellite-borne hyperspectral imager; obtaining a plurality of calibration images according to the starting wavelength and the ending wavelength of the satellite-borne hyperspectral imager to be calibrated; determining a row number corresponding to the maximum value in each center wavelength and the calibration images by utilizing the plurality of calibration images; calculating a relative spectral response function of the to-be-calibrated satellite-borne hyperspectral imager based on the relative spectral irradiance distribution, the plurality of calibration images and the row numbers corresponding to the maximum values; and determining half maximum full waves corresponding to each center wavelength of the satellite-borne hyperspectral imager to be calibrated according to the relative spectral response function.
The apparatus embodiments described above are merely illustrative, wherein the elements illustrated as separate elements may or may not be physically separate, and the elements shown as elements may or may not be physical elements, may be located in one place, or may be distributed over a plurality of network elements. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art will understand and implement the present invention without undue burden.
From the above description of the embodiments, it will be apparent to those skilled in the art that the embodiments may be implemented by means of software plus necessary general hardware platforms, or of course may be implemented by means of hardware. Based on this understanding, the foregoing technical solution may be embodied essentially or in a part contributing to the prior art in the form of a software product, which may be stored in a computer readable storage medium, such as ROM/RAM, a magnetic disk, an optical disk, etc., including several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the method described in the respective embodiments or some parts of the embodiments.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the 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 scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. The spectrum calibration method of the satellite-borne hyperspectral imager is characterized by comprising the following steps of:
s1, acquiring the preset number of dark background image data of a satellite-borne hyperspectral imager to be calibrated in a dark background imaging mode;
s2, acquiring the relative spectral irradiance distribution of the to-be-calibrated satellite-borne hyperspectral imager by monochromatic parallel light irradiation of the monochromator, and acquiring a calibration image of the to-be-calibrated satellite-borne hyperspectral imager;
s3, obtaining a plurality of calibration images from the initial wavelength and the termination wavelength of the satellite-borne hyperspectral imager to be calibrated;
s4, determining the row number corresponding to the maximum value in each center wavelength and the calibration images by utilizing the plurality of calibration images;
s5, calculating a relative spectral response function of the satellite-borne hyperspectral imager to be calibrated based on the relative spectral irradiance distribution, the plurality of calibration images and the row numbers corresponding to the maximum values;
and S6, determining half-maximum full waves corresponding to each center wavelength of the satellite-borne hyperspectral imager to be calibrated according to the relative spectral response function.
2. The method for calibrating a spectrum of an on-board hyperspectral imager as claimed in claim 1, wherein step S1 is preceded by:
and obtaining the original device parameters of the satellite-borne hyperspectral imager to be calibrated.
3. The method for calibrating a spectrum of an on-board hyperspectral imager as claimed in claim 1, wherein step S2 comprises:
the monochromator outputs monochromatic light after receiving a broad-spectrum illumination light source;
the monochromatic light is irradiated through a collimator to obtain monochromatic parallel light;
the monochromatic parallel light irradiates the satellite-borne hyperspectral imager to be calibrated to obtain the relative spectral irradiance distribution;
and acquiring and measuring the relative spectral irradiance distribution with preset times to obtain the calibration image.
4. The method for calibrating a spectrum of an on-board hyperspectral imager as claimed in claim 1, wherein step S3 comprises:
and (2) repeating the step (S2) with the preset central wavelength change step of the monochromator from the initial wavelength of the to-be-calibrated satellite-borne hyperspectral imager until the final wavelength of the to-be-calibrated satellite-borne hyperspectral imager is reached, so as to obtain the plurality of calibration images.
5. The method for calibrating a spectrum of an on-board hyperspectral imager as claimed in claim 1, wherein step S4 comprises:
s401, determining any central wavelength calibration image in the plurality of calibration images, calculating an average remote sensing image pixel brightness value of the any central wavelength calibration image row by row, extracting a row number corresponding to a maximum value in the average remote sensing image pixel brightness value, and determining any central wavelength output row based on the row number corresponding to the maximum value;
and S402, repeating the step S401 one by one according to the central wavelength, and obtaining the central wavelength output rows corresponding to different central wavelengths through least square fitting.
6. The method for calibrating a spectrum of an on-board hyperspectral imager as claimed in claim 1, wherein step S5 comprises:
s501, calculating the ratio of the pixel brightness value of the average remote sensing image of any central wavelength calibration image to the relative spectral irradiance distribution of the corresponding monochromatic light, dividing the ratio by the maximum value of the ratio between the lower limit of the wavelength of any central wavelength spectral channel and the upper limit of the wavelength of any central wavelength spectral channel, and obtaining the relative spectral response function of any central wavelength;
s502, fitting the relative spectral response function of any central wavelength spectral channel by adopting a least square method to obtain the relative spectral response function of the satellite-borne hyperspectral imager to be calibrated in any central wavelength corresponding spectral channel;
and S503, repeating the step S501 and the step S502 one by one according to the central wavelength, and obtaining the relative spectral response functions of the spectral channels corresponding to different central wavelengths.
7. The method for calibrating a spectrum of an on-board hyperspectral imager as claimed in claim 1, wherein step S6 comprises:
s601, determining a short wave wavelength which is one half of the peak response in a relative spectral response function of any central wavelength corresponding to a spectral channel and is positioned at a short wave, and a long wave wavelength which is positioned at a long wave, and subtracting the short wave wavelength from the long wave wavelength to obtain a half-maximum full wave of any central wavelength corresponding to the spectral channel;
s602, repeating the step S601 one by one according to the central wavelength, and obtaining half-maximum full waves of the spectrum channels corresponding to different central wavelengths.
8. A spectral scaling system for a satellite-borne hyperspectral imager, comprising:
the acquisition module is used for acquiring the preset number of dark background image data of the satellite-borne hyperspectral imager to be calibrated in a dark background imaging mode;
the acquisition module is used for acquiring the relative spectral irradiance distribution of the to-be-calibrated satellite-borne hyperspectral imager through monochromatic parallel light irradiation of the monochromator and acquiring a calibration image of the to-be-calibrated satellite-borne hyperspectral imager;
the calibration module is used for obtaining a plurality of calibration images from the starting wavelength and the ending wavelength of the satellite-borne hyperspectral imager to be calibrated;
the determining module is used for determining the row number corresponding to the maximum value in each center wavelength and the calibration images by utilizing the plurality of calibration images;
the calculation module is used for calculating the relative spectral response function of the satellite-borne hyperspectral imager to be calibrated based on the relative spectral irradiance distribution, the plurality of calibration images and the row numbers corresponding to the maximum values;
and the comprehensive module is used for determining half-maximum full waves corresponding to each center wavelength of the satellite-borne hyperspectral imager to be calibrated according to the relative spectral response function.
9. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements the method for spectral scaling of an on-board hyperspectral imager as claimed in any one of claims 1 to 7 when the program is executed by the processor.
10. A non-transitory computer readable storage medium having stored thereon a computer program, which when executed by a processor implements the method of spectral scaling of a satellite borne hyperspectral imager as claimed in any one of claims 1 to 7.
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