CN117368124A - Radiation calibration method, system, device and medium for hyperspectral camera - Google Patents
Radiation calibration method, system, device and medium for hyperspectral camera Download PDFInfo
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Abstract
The invention discloses a radiation calibration method, a radiation calibration system, a radiation calibration device and a radiation calibration medium for a hyperspectral camera, wherein the radiation calibration method comprises the following steps: acquiring response curves of different spectral bands under different integration stages; calculating the center wavelength and the spectral resolution according to the response curve; matching the radiation source according to the center wavelength and the spectral resolution; performing radiation calibration through a radiation light source pair to obtain radiation data; carrying out data acquisition on the radiation data by using an extremum traversal method to obtain input radiation brightness and an output response image; nonlinear elimination is carried out through a least square method, and then an absolute radiation calibration coefficient is obtained through calculation; and calculating by a least square method to obtain the relative radiation calibration coefficient. The radiation light sources of different spectrum channels can be rapidly matched to complete radiation calibration, and the method can be widely applied to the technical field of radiation calibration.
Description
Technical Field
The invention relates to the technical field of radiometric calibration, in particular to a radiometric calibration method, a radiometric calibration system, a radiometric calibration device and a radiometric calibration medium for a hyperspectral camera.
Background
The hyperspectral camera can combine imaging technology and spectrum detection technology, while imaging the spatial features of the target, form tens or even hundreds of narrow wave bands for each spatial pixel to carry out continuous spectrum coverage, can fully reflect the differences of physical structures and chemical components in the ground object through different spectrum information, can carry out spatial and spectral three-dimensional imaging on the ground object compared with optical spatial two-dimensional imaging, acquire the unique continuous feature spectrum of the ground object in a wide spectrum range under a certain spatial resolution, has outstanding advantages for fine classification and identification of the ground object, and is an important front technical means for remote sensing of the ground at present.
However, the existing hyperspectral camera has a large number of channels in the spectral band, the radiation characteristics of each spectral band are large in difference, the radiation calibration input is difficult to unify, and the radiation calibration time is long.
Disclosure of Invention
In view of the above, an object of the embodiments of the present invention is to provide a radiation calibration method, system, device and medium for a hyperspectral camera, so as to solve the problems that the number of channels in a hyperspectral camera spectral band is large, the difference of radiation characteristics of each spectral band is large, the radiation calibration input is difficult to unify, and the radiation calibration time is long.
In a first aspect, an embodiment of the present invention provides a radiation calibration method for a hyperspectral camera, including the following steps:
performing spectrum calibration on the hyperspectral camera to obtain different spectral response curves under different integral stages;
calculating the center wavelength and the spectrum resolution of different spectral bands under different integral stages according to the response curve;
a radiation source matching different spectral channels according to the center wavelength and the spectral resolution;
carrying out radiometric calibration on the hyperspectral camera through a radiation light source to obtain radiation data of different spectral bands;
carrying out data acquisition on the radiation data of different spectral ranges by using an extremum traversal method to obtain input radiation brightness and output response images of different spectral ranges;
the input radiation brightness and the output response image of different spectral bands are subjected to nonlinear elimination through a least square method, and then absolute radiation calibration coefficients of different spectral bands are obtained through calculation;
and calculating to obtain relative radiation calibration coefficients of different spectral bands according to the nonlinear rejected output response image, the input radiation brightness and a least square method.
Optionally, calculating the center wavelength and the spectral resolution of different spectral bands under different integration stages according to the response curve specifically includes:
respectively obtaining different spectral response curves under different integral series;
calculating according to response curves of different spectral bands under the same integral series to obtain the center wavelength and the spectral resolution of the spectral band of the same integral series;
and obtaining the center wavelength and the spectral resolution of different spectral bands under different integration levels after the calculation of the different integration levels.
Optionally, the radiation source matching different spectrum channels according to the center wavelength and the spectrum resolution specifically includes:
constructing a response function according to the center wavelength and the spectrum separately rate;
solving optimal wavelengths of different spectrum channels according to the response function, wherein the optimal wavelengths represent wavelengths optimally adapted to the spectrum channels;
the radiation sources of the different spectral channels are matched according to the optimal wavelengths of the different spectral channels.
Optionally, the radiation source matching different spectrum channels further includes:
acquiring the saturated electron number of the hyperspectral camera;
obtaining maximum entrance pupil brightness of different spectral bands based on the saturated electron number;
and matching the radiation sources of different spectrum channels according to the maximum entrance pupil brightness of different spectrum segments.
Optionally, the acquiring the saturated electron number of the hyperspectral camera specifically includes:
the method comprises the steps of obtaining a change curve of signal electronic numbers of a hyperspectral camera, wherein the specific calculation formula of the signal electronic numbers is as follows:
wherein S represents the number of signal electrons, L represents the entrance pupil luminance, τ represents the optical system transmittance of the hyperspectral camera, T int Represents the integration time, R COMS Representing the sensitivity of the CMOS detector of the hyperspectral camera, F representing the ratio of the focal length of the lens to the lens aperture in the hyperspectral camera's optical system;
and determining the saturated electron number according to the change curve and a preset rule, wherein the preset rule represents the maximum signal electron number on the obtained change curve.
Optionally, the calculating to obtain the absolute radiation scaling coefficients of different spectral bands after the nonlinear rejection is performed on the input radiation brightness and the output response image of different spectral bands by the least square method specifically includes:
performing linear fitting on the input radiance and the output response image combinations of different spectral bands by a least square method to obtain a fitting graph;
removing nonlinear points which are not on the fitting graph line;
repeatedly fitting the fitting curve by a least square method to obtain absolute radiometric calibration curves of different spectral bands;
determining the absolute radiometric calibration coefficients of different spectral bands based on the absolute radiometric calibration curves of different spectral bands and a preset calculation rule.
Optionally, the calculating according to the nonlinear rejected output response image, the input radiation brightness and the least square method to obtain the relative radiation scaling coefficients of different spectral bands specifically includes:
calculating a first response value of each column of pixels of different spectral bands under different input radiation brightness according to the output response image and the input radiation brightness;
acquiring second response values of a plurality of detectors in the hyperspectral camera;
calculating the linear relation between the first response value and the second response value through a least square method;
and calculating the relative radiation calibration coefficients of different spectral bands according to the linear relation and the calculation rule under different spectral bands.
In a second aspect, an embodiment of the present invention provides a radiometric calibration system for a hyperspectral camera, comprising:
the first module is used for carrying out spectrum calibration on the hyperspectral camera to obtain different spectral response curves under different integration series;
the second module is used for calculating the center wavelength and the spectral resolution of different spectral bands under different integration stages according to the response curve;
a third module for matching radiation sources of different spectral channels according to the center wavelength and the spectral resolution;
a fourth module, configured to perform radiometric calibration on the hyperspectral camera by using a radiation light source to obtain radiation data of different spectral bands;
a fifth module, configured to acquire data of the radiation data of different spectral bands by using an extremum traversal method, so as to obtain input radiation brightness and output response images of different spectral bands;
a sixth module, configured to perform nonlinear rejection on the input radiation brightness and the output response image of different spectral bands by using a least square method, and then calculate to obtain absolute radiation calibration coefficients of different spectral bands;
and a seventh module, configured to calculate, according to the output response image after nonlinear rejection, the input radiation brightness, and a least square method, a relative radiation scaling coefficient of different spectral bands.
In a third aspect, an embodiment of the present invention provides a radiation calibration device of a hyperspectral camera, including:
at least one processor;
at least one memory for storing at least one program;
the at least one program, when executed by the at least one processor, causes the at least one processor to implement the method as described above.
In a fourth aspect, embodiments of the present invention provide a computer readable storage medium having stored therein a processor executable program for performing the method as described above when executed by a processor.
The embodiment of the invention has the following beneficial effects: the embodiment of the invention provides a radiation calibration method of a hyperspectral camera, which comprises the following steps: performing spectrum calibration on the hyperspectral camera to obtain different spectral response curves under different integral stages; calculating the center wavelength and the spectrum resolution of different spectral bands under different integral stages according to the response curve; a radiation source matching different spectral channels according to the center wavelength and the spectral resolution; carrying out radiometric calibration on the hyperspectral camera through a radiation light source to obtain radiation data of different spectral bands; carrying out data acquisition on the radiation data of different spectral ranges by using an extremum traversal method to obtain input radiation brightness and output response images of different spectral ranges; the input radiation brightness and the output response image of different spectral bands are subjected to nonlinear elimination through a least square method, and then absolute radiation calibration coefficients of different spectral bands are obtained through calculation; and calculating to obtain relative radiation calibration coefficients of different spectral bands according to the nonlinear rejected output response image, the input radiation brightness and a least square method. The center wavelength and the spectral resolution of different spectral bands are obtained through response curves of different spectral bands under different integration levels, so that the radiation sources of different spectral channels are matched, response images are obtained, absolute radiation calibration coefficients and relative radiation calibration coefficients are obtained after processing, the radiation sources of different spectral channels can be quickly matched, and radiation calibration is completed.
Drawings
FIG. 1 is a schematic flow chart of steps of a radiometric calibration method for a hyperspectral camera according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a hyperspectral camera according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of spectral filtering of a graded filter according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a spectral graph of spectral scaling results provided by an embodiment of the present invention;
FIG. 5 is a schematic diagram of a spectrum scaling device according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a spectral scaling apparatus according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of digital domain TDI imaging provided by an embodiment of the present invention;
FIG. 8 is a schematic view of a linear fit of an input radiance and output response image provided by an embodiment of the invention;
FIG. 9 is a schematic diagram of a radiation targeting device according to an embodiment of the present invention;
FIG. 10 is a schematic diagram of relative radiation calibration correction provided by an embodiment of the present invention;
FIG. 11 is a schematic diagram of a radiation calibration system for a hyperspectral camera provided by an embodiment of the present invention;
fig. 12 is a schematic diagram of a radiation calibration device of a hyperspectral camera according to an embodiment of the present invention;
reference numerals: the optical lens 1, the graded filter 2, the area array detector component 3, the light 4, the halogen tungsten light source 5, the slit 6, the monochromator 7, the collimator 8, the camera body 9, the quick-vision system 10, the control system 11, the integrating sphere opening 12, the integrating sphere light source 13, the integrating sphere control box 14, the camera 15, the data processing system 16, the ground 17, the spectrum radiometer 18 and the adjustable workbench 19.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the invention.
In the description of the present invention, it should be understood that references to orientation descriptions such as upper, lower, front, rear, left, right, etc. are based on the orientation or positional relationship shown in the drawings, are merely for convenience of description of the present invention and to simplify the description, and do not indicate or imply that the apparatus or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present invention.
In the description of the present invention, a number means one or more, a number means two or more, and greater than, less than, exceeding, etc. are understood to not include the present number, and above, below, within, etc. are understood to include the present number. The description of the first and second is for the purpose of distinguishing between technical features only and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.
In the description of the present invention, unless explicitly defined otherwise, terms such as arrangement, installation, connection, etc. should be construed broadly and the specific meaning of the terms in the present invention can be reasonably determined by a person skilled in the art in combination with the specific contents of the technical scheme.
As shown in fig. 1, an embodiment of the present invention provides a radiation calibration method for a hyperspectral camera, including the following steps:
s100, spectrum calibration is carried out on the hyperspectral camera to obtain different spectral response curves under different integral series.
Specifically, the light-splitting hyperspectral camera with the gradient filter is adopted, the specific structure is shown in fig. 2, the light-splitting hyperspectral camera with the variable filter comprises an optical lens 1, the gradient filter 2 and an area array detector assembly 3, the optical lens 1 acquires light rays 4 of ground object target information and converges the light rays, then spectrum light splitting is carried out through the gradient filter 2, the specific spectrum light splitting can refer to fig. 3, and light in different spectrum sections is obtained through light splitting through the gradient filter 2. In-orbit hyperspectral imaging is achieved by the digital domain TDI (Time Delay Integration ) technique of the area array detector assembly 3, and thus a response curve of the spectrum is obtained. A spectrometer can be used in a laboratory to emit monochromatic light with 1nm as an interval in the spectrum range of 400nm to 1000nm, and the relative spectral response curves corresponding to each CMOS (Complementary Metal-Oxide-Semiconductor) detector are tested.
S200, calculating the center wavelength and the spectral resolution of different spectral bands under different integral stages according to the response curve.
Specifically, referring to fig. 4, a spectrum curve diagram of a spectrum calibration result is shown, and according to a response curve in the spectrum curve diagram, a center wavelength and a spectrum resolution of the spectrum under a certain integral series can be obtained. The specific integral series and spectrum can be acquired by itself according to the needs, and the center wavelength of the abscissa and the spectrum resolution of the ordinate can be acquired clearly and intuitively in the spectrum curve diagram.
Optionally, calculating the center wavelength and the spectral resolution of different spectral bands under different integration stages according to the response curve specifically includes:
s210, respectively acquiring different spectral response curves under different integral series;
s220, calculating the center wavelength and the spectral resolution of the spectrum section of the same integral stage according to response curves of different spectrum sections under the same integral stage;
s230, the center wavelength and the spectral resolution of different spectral bands under different integration series are obtained after the calculation of the different integration series.
In a specific embodiment, the device for calibrating the spectrum of the graded filter split hyperspectral camera mainly comprises a halogen tungsten lamp light source 5, a slit 6, a monochromator 7, a reflective collimator 8, a control system 11, a quick-vision system 10 and other devices. The spectral scaling structure is schematically shown in figure 5. The monochromator 7 emits monochromatic light with 1nm as interval, the hyperspectral camera adopts an area array imaging function to determine the windowing line position of each spectral band, the integral series of each spectral band is respectively changed, the spectral response curves of each spectral band under different integral series are analyzed by adopting an on-orbit push-broom imaging mode, the central wavelength and the spectral resolution of each integral series spectral band are calculated, and the spectral curve diagram of the spectral calibration result of a certain spectral band of the hyperspectral camera is shown in fig. 4, so that the central wavelength and the spectral resolution of each spectral band can be obtained according to the spectral curve.
In a specific embodiment, the visible spectrum range of the graded filter beam splitting hyperspectral camera is 400-1000nm, the number of channels is 32, the imaging breadth is 150km, the total imaging breadth is composed of 3 CMOS detectors, the number of pixels of each CMOS detector is 5056×2968, the pixel size is 4.25 μm, the graded filter 2 is arranged at the front end of the area array detector 3, the graded filter 2 averagely divides light waves of 400-1000nm into 32 spectral bands, each spectral band occupies about 2968/32=92 lines on the CMOS detector, 8-level integral imaging is carried out by using 8-line pixels for each spectral band, and the spectral distribution diagram of the area array detector assembly 3 is shown in fig. 6. The digital domain TDI imaging principle of the area array detector assembly is shown in fig. 7, and fig. 7 (a) is that a first row of objects A in a certain spectral band of the detector is imaged; FIG. 7 (B) is a view of a first row of objects B imaged and a second row of objects A imaged as the satellite moves; FIG. 7 (C) is a view of a first row of objects C imaged, a second row of objects B imaged, and a third row of objects A imaged as the satellite moves; similarly, 8 integral images of the same scene are realized for each row.
TABLE 1 center wavelength and spectral resolution for each spectral band
As shown in table 1, the center wavelength and the spectral resolution of each spectrum were obtained from the spectral curves. According to the table, the obtained center wavelength is the same as the ideal wavelength of the spectrum, so that the light source of each spectrum channel can be accurately and quickly matched.
S300, matching the radiation sources of different spectrum channels according to the center wavelength and the spectrum resolution.
Specifically, according to the obtained central wavelengths and spectrum resolutions of different spectrum ranges under different integration levels, the central wavelengths and spectrum resolutions correspond to different spectrum channels of the hyperspectral camera, and the radiation light sources are matched according to the central wavelengths and spectrum resolutions corresponding to the spectrum channels, so that the radiation light sources are matched with the spectrum channels as much as possible.
Optionally, the radiation source matching different spectrum channels according to the center wavelength and the spectrum resolution specifically includes:
s310, constructing a response function according to the center wavelength and the spectrum separately rate;
s320, solving optimal wavelengths of different spectrum channels according to the response function, wherein the optimal wavelengths represent wavelengths optimally adapted to the spectrum channels;
s330, the radiation sources of the different spectrum channels are matched according to the optimal wavelengths of the different spectrum channels.
Specifically, the response function of the spectrum channel and the wavelength is built through the center wavelength and the spectrum respectively rate corresponding to each spectrum channel under different integral series, and the best wavelength of the best matching spectrum channel is obtained through the maximum value of the response function. And then the radiation light source corresponding to the optimal wavelength is matched with the spectrum channel, so that the light source matching of the spectrum channel is completed, and the input light sources are unified.
Optionally, the radiation source matching different spectrum channels further includes:
s340, acquiring the saturated electron number of the hyperspectral camera;
s350, acquiring maximum entrance pupil brightness of different spectral bands based on the saturated electron number;
s360, the radiation light sources of different spectrum channels are matched according to the maximum entrance pupil brightness of different spectrum segments.
Specifically, a calculation formula of the signal electron number can be obtained according to an optical camera illuminance calculation formula and a detector photoelectric conversion formula, and the saturated electron number of the hyperspectral camera is calculated according to the calculation formula of the signal electron number. And obtaining the maximum entrance pupil brightness of different spectral bands according to the calculated saturated electron number, and matching the radiation light sources of different spectral channels according to the maximum entrance pupil brightness.
Optionally, the acquiring the saturated electron number of the hyperspectral camera specifically includes:
s341, acquiring a change curve of the signal electronic number of the hyperspectral camera, wherein the specific calculation formula of the signal electronic number is as follows:
wherein S represents the number of signal electrons, L represents the entrance pupil luminance, τ represents the optical system transmittance of the hyperspectral camera, T int Represents the integration time, R COMS Representing the sensitivity of the CMOS detector of the hyperspectral camera, F representing the ratio of the focal length of the lens to the lens aperture in the hyperspectral camera's optical system;
s342, determining the saturated electron number according to the change curve and a preset rule, wherein the preset rule represents the maximum signal electron number on the change curve.
Specifically, under the condition that camera parameters remain unchanged, the maximum entrance pupil brightness L which can be accepted by different spectral bands can be calculated according to the saturated electron number of the detector, the emergent radiance of the radiant light source is known in a radiation calibration experiment in a laboratory, and the proper radiant light source can be matched for the camera by comparing the radiant light source radiance with the calculated different camera entrance pupil brightness L.
S400, performing radiometric calibration on the hyperspectral camera through a radiation light source to obtain radiation data of different spectral bands.
Specifically, a radiation light source is radiated to a hyperspectral camera for radiation calibration, a radiation calibration result is obtained after the radiation calibration is completed, and radiation data of different spectral bands are obtained according to the radiation calibration result.
S500, carrying out data acquisition on the radiation data of different spectral ranges by an extremum traversal method to obtain input radiation brightness and output response images of different spectral ranges.
Specifically, the acquired radiation data in different spectral ranges are acquired through an extremum traversal method, unnecessary data are removed, the original properties of the data are restored as much as possible, the data processing capacity is reduced, and the accuracy of the data processing result is guaranteed. The input radiation brightness and the output response image of different spectral ranges can be obtained from the collected radiation data.
S600, carrying out nonlinear elimination on the input radiation brightness and the output response image of different spectral bands by a least square method, and then calculating to obtain absolute radiation calibration coefficients of different spectral bands.
Specifically, referring to fig. 8, linear fitting is performed on input radiation brightness and output response images of different spectral bands, when nonlinear points (i.e., points not on a fitting curve) caused by excessive darkness, overexposure or misoperations of a stored image exist, the nonlinear points are automatically removed, the linear correlation is combined by repeated fitting response through a least square method, finally, absolute radiation calibration linear curves of different parameters of each spectral band can be obtained, absolute radiation calibration coefficients can be obtained according to the absolute radiation calibration linear curves, and therefore the absolute radiation calibration coefficients of different spectral bands are obtained.
Optionally, the calculating to obtain the absolute radiation scaling coefficients of different spectral bands after the nonlinear rejection is performed on the input radiation brightness and the output response image of different spectral bands by the least square method specifically includes:
s610, performing linear fitting on the input radiance and the output response image combinations of different spectral bands by a least square method to obtain a fitting graph;
s620, eliminating nonlinear points which are not on the fitting graph line;
s630, repeatedly fitting the fitting curve through a least square method to obtain absolute radiometric calibration curves of different spectral bands;
s640, determining the absolute radiometric calibration coefficients of different spectral bands based on the absolute radiometric calibration curves of the different spectral bands and a preset calculation rule.
In a specific embodiment, the radiation targeting device mainly comprises an integrating sphere light source 13, an adjustable workbench 19, a spectrum radiometer 18, a data processing system 16 and the like. The schematic structure of the radiometric calibration device is shown in fig. 9, the camera is arranged on an adjustable working platform 19, the working platform 19 is adjusted to enable the light-transmitting hole of the camera 15 to be positioned at the center of the integrating sphere light source 13, and the optical axis of the camera is perpendicular to the integrating sphere light source 13, so that the coverage of the full aperture and the full field of view is realized. The light of the integrating sphere light source is controlled by the integrating sphere control box. Because the number of the spectrum channels of the gradient filter split hyperspectral camera is large, the radiation characteristics of each spectrum are large in difference, and the light source 13 of an integrating sphere is difficult to simultaneously consider all the spectrums, the condition that the response of a certain spectrum is low and the response of a certain spectrum is saturated can occur, if a single spectrum is used for selecting an input light source combination, the time consumption is long, errors are prone to occur, and great difficulty is brought to subsequent image processing work, therefore, according to the spectrum calibration result of the hyperspectral camera, a radiation response model can be established with the spectrum of a halogen lamp of a common radiation light source, the positions of the radiation light sources under the condition that all the spectrum channels respond to saturation are established, the proper simulated radiation light sources are matched, the response model is utilized to determine that each spectrum covers the high, medium and low radiation input range, the response condition is not required to be determined one by one spectrum, and the radiation data acquisition can be simultaneously carried out on all the spectrums by adopting an extremum traversal method.
For the collected images with different radiation brightness of each channel, linear fitting is carried out on all radiation calibration input radiation brightness and output response image combinations through a least square method, nonlinear points are automatically removed as shown in fig. 8, the response combination linear correlation is repeatedly fitted through the least square method, and finally absolute radiation calibration linear curves under different parameters of each spectrum can be obtained. The radiance Le (lambda) given by the integrating sphere light source 13 and the response DN value of each spectral band of the camera, le (lambda) =k·DN+b, k is the slope of a linear curve, b is the intercept of the curve, r 2 The correlation coefficient corresponding to the linear fitting represents the response linearity of the camera, and according to the obtained k value and b value, the spectral response characteristics of the target ground object under different spectral bands can be inverted through DN value response of the camera, wherein DN (Digital Number) represents the brightness and darkness of an image, and the larger and brighter the smaller and darker the larger and darker the DN (Digital Number) is also called as a gray value.
S700, calculating to obtain relative radiation scaling coefficients of different spectral bands according to the output response image after nonlinear rejection, the input radiation brightness and a least square method.
Specifically, under different input radiation brightness according to the output response image and the input radiation brightness, each column of pixel response values of the output response image and the response average value of the 3 CMOS detectors are calculated, and then coordinate combinations corresponding to the pixel response values and the response average values are obtained. And taking the pixel response value as an abscissa, taking the response mean value as an ordinate, connecting a plurality of coordinate points under different input radiation brightness into a line, and solving the slope and intercept of the line to obtain the relative radiation calibration coefficient of the column pixels.
Optionally, the calculating according to the nonlinear rejected output response image, the input radiation brightness and the least square method to obtain the relative radiation scaling coefficients of different spectral bands specifically includes:
s710, calculating a first response value of each column of pixels of different spectral ranges under different input radiation brightnesses according to the output response image and the input radiation brightness;
s720, obtaining second response values of a plurality of detectors in the hyperspectral camera;
s730, calculating the linear relation between the first response value and the second response value through a least square method;
s740, calculating the relative radiation calibration coefficients of different spectral bands according to the linear relation and the calculation rule under different spectral bands.
In a specific embodiment, the focal plane of the graded filter split hyperspectral camera is spliced and imaged by adopting 3 CMOS detectors, the breadth is 150km, and in order to ensure the uniformity of the radiation response displayed after the 3 CMOS detectors are spliced, the relative radiation correction needs to be carried out on each column of pixels of push-broom imaging. According to the combination of different input radiance and camera output DN values screened by the absolute radiation least square method, calculating corresponding combination of a first response value DN1 of each column of pixels under different brightnesses and a second response value DN2 of 3 CMOS detectors, wherein the second response value DN2 is an average response value of 3 CMOS detectors. And calculating the linear relation between DN1 and DN2 by a least square method, and finally obtaining the relative radiation calibration linear curve under different parameters of each spectrum. As shown in fig. 10, the hyperspectral camera is calibrated and corrected by relative radiation, the dotted scattered lines are gray scale curves of CMOS1, CMOS2 and CMOS3 before relative radiation correction, and the solid straight lines are curves after relative radiation correction, so that the radiation response uniformity of the three detector column pixels after relative radiation correction can be obtained.
The embodiment of the invention has the following beneficial effects: the invention provides a radiation calibration method of a hyperspectral camera, which comprises the following steps: performing spectrum calibration on the hyperspectral camera to obtain different spectral response curves under different integral stages; calculating the center wavelength and the spectrum resolution of different spectral bands under different integral stages according to the response curve; a radiation source matching different spectral channels according to the center wavelength and the spectral resolution; carrying out radiometric calibration on the hyperspectral camera through a radiation light source to obtain radiation data of different spectral bands; carrying out data acquisition on the radiation data of different spectral ranges by using an extremum traversal method to obtain input radiation brightness and output response images of different spectral ranges; the input radiation brightness and the output response image of different spectral bands are subjected to nonlinear elimination through a least square method, and then absolute radiation calibration coefficients of different spectral bands are obtained through calculation; and calculating to obtain relative radiation calibration coefficients of different spectral bands according to the nonlinear rejected output response image, the input radiation brightness and a least square method. The center wavelength and the spectral resolution of different spectral bands are obtained through response curves of different spectral bands under different integration levels, so that the radiation sources of different spectral channels are matched, response images are obtained, absolute radiation calibration coefficients and relative radiation calibration coefficients are obtained after processing, the radiation sources of different spectral channels can be quickly matched, and radiation calibration is completed.
As shown in fig. 11, an embodiment of the present invention further provides a system for automatically calibrating coordinates of a robot end assembly, including:
a first module for acquiring image data of an extract of the first tool tip 8 of the robot;
a second module, configured to acquire reference image data, and acquire a first coordinate offset of the first tool end 8 according to pixel coordinates between the image data and the reference image data, where the pixel coordinates represent image coordinates of a pixel point;
a third module, configured to obtain a first tool 3 length, a first tool angle 6, a first body arm length 11, and a second body arm length 21 of the tip assembly, and determine tip coordinates of a first tool tip 8 according to the first tool 3 length, the first tool angle 6, the first body arm length 11, and the second body arm length 21, wherein the first tool angle 6 characterizes an angle between the first tool 3 and the second body arm 2;
a fourth module, configured to obtain target data of a target point, where the target point represents a hole site to be aligned after the first tool end 8 moves;
a fifth module, configured to obtain a center coordinate of a connection center point of the body first arm 1 and the body second arm 2, determine a first C-axis angle 12 based on the end coordinate, the center coordinate, and the target data, where the first C-axis angle 12 characterizes a C-axis angle when the first tool end 8 is aligned with the target point;
a sixth module for determining a first target coordinate from the first coordinate offset and the first C-axis angle 12, wherein the first target coordinate characterizes a coordinate of the first tool tip 8 when aligned with the target point;
a seventh module for moving the first tool end 8 to the first target coordinates.
It can be seen that the content in the above method embodiment is applicable to the system embodiment, and the functions specifically implemented by the system embodiment are the same as those of the method embodiment, and the beneficial effects achieved by the method embodiment are the same as those achieved by the method embodiment.
As shown in fig. 12, the embodiment of the present invention further provides an apparatus for automatically calibrating coordinates of a robot end assembly, including:
at least one processor;
at least one memory for storing at least one program;
the at least one program, when executed by the at least one processor, causes the at least one processor to carry out the method steps described in the method embodiments above.
It can be seen that the content in the above method embodiment is applicable to the embodiment of the present device, and the functions specifically implemented by the embodiment of the present device are the same as those of the embodiment of the above method, and the beneficial effects achieved by the embodiment of the above method are the same as those achieved by the embodiment of the above method.
Furthermore, embodiments of the present application disclose a computer program product or a computer program, which is stored in a computer readable storage medium. The computer program may be read from a computer readable storage medium by a processor of a computer device, the processor executing the computer program causing the computer device to perform the method as described above. Similarly, the content in the above method embodiment is applicable to the present storage medium embodiment, and the specific functions of the present storage medium embodiment are the same as those of the above method embodiment, and the achieved beneficial effects are the same as those of the above method embodiment.
It is to be understood that all or some of the steps, systems, and methods disclosed above may be implemented in software, firmware, hardware, and suitable combinations thereof. Some or all of the physical components may be implemented as software executed by a processor, such as a central processing unit, a digital information processor, or a microprocessor, or as hardware, or as an integrated circuit, such as an application specific integrated circuit. Such software may be distributed on computer readable media, which may include computer storage media (or non-transitory media) and communication media (or transitory media). The term computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data, as known to those skilled in the art. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital Versatile Disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by a computer. Furthermore, as is well known to those of ordinary skill in the art, communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data message such as a carrier wave or other transport mechanism and includes any information delivery media.
The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of one of ordinary skill in the art without departing from the spirit of the present invention.
Claims (10)
1. A method for radiometric calibration of a hyperspectral camera, comprising:
performing spectrum calibration on the hyperspectral camera to obtain different spectral response curves under different integral stages;
calculating the center wavelength and the spectrum resolution of different spectral bands under different integral stages according to the response curve;
a radiation source matching different spectral channels according to the center wavelength and the spectral resolution;
carrying out radiometric calibration on the hyperspectral camera through a radiation light source to obtain radiation data of different spectral bands;
carrying out data acquisition on the radiation data of different spectral ranges by using an extremum traversal method to obtain input radiation brightness and output response images of different spectral ranges;
the input radiation brightness and the output response image of different spectral bands are subjected to nonlinear elimination through a least square method, and then absolute radiation calibration coefficients of different spectral bands are obtained through calculation;
and calculating to obtain relative radiation calibration coefficients of different spectral bands according to the nonlinear rejected output response image, the input radiation brightness and a least square method.
2. The method according to claim 1, wherein the calculating the absolute radiation scaling coefficients of different spectral bands after nonlinear rejection of the input radiation brightness and the output response image of different spectral bands by the least square method specifically includes: performing linear fitting on the input radiance and the output response image combinations of different spectral bands by a least square method to obtain a fitting graph;
removing nonlinear points which are not on the fitting graph line;
repeatedly fitting the fitting curve by a least square method to obtain absolute radiometric calibration curves of different spectral bands;
determining the absolute radiometric calibration coefficients of different spectral bands based on the absolute radiometric calibration curves of different spectral bands and a preset calculation rule.
3. The method according to claim 1, wherein said radiation sources matching different spectral channels according to said center wavelength and said spectral resolution, in particular comprises:
constructing a response function according to the center wavelength and the spectrum separately rate;
solving optimal wavelengths of different spectrum channels according to the response function, wherein the optimal wavelengths represent wavelengths optimally adapted to the spectrum channels;
the radiation sources of the different spectral channels are matched according to the optimal wavelengths of the different spectral channels.
4. The method of claim 3, wherein the radiation source matching different spectral channels further comprises: acquiring the saturated electron number of the hyperspectral camera;
obtaining maximum entrance pupil brightness of different spectral bands based on the saturated electron number;
and matching the radiation sources of different spectrum channels according to the maximum entrance pupil brightness of different spectrum segments.
5. The method according to claim 4, wherein the obtaining the saturated electron number of the hyperspectral camera specifically comprises:
the method comprises the steps of obtaining a change curve of signal electronic numbers of a hyperspectral camera, wherein the specific calculation formula of the signal electronic numbers is as follows:
wherein S represents the number of signal electrons, L represents the entrance pupil luminance, τ represents the optical system transmittance of the hyperspectral camera, T int Represents the integration time, R COMS Representing the sensitivity of the CMOS detector of the hyperspectral camera, F representing the ratio of the focal length of the lens to the lens aperture in the hyperspectral camera's optical system;
and determining the saturated electron number according to the change curve and a preset rule, wherein the preset rule represents the maximum signal electron number on the obtained change curve.
6. The method according to claim 1, wherein calculating the center wavelength and the spectral resolution of different spectral bands at different integration orders from the response curve comprises:
respectively obtaining different spectral response curves under different integral series;
calculating according to response curves of different spectral bands under the same integral series to obtain the center wavelength and the spectral resolution of the spectral band of the same integral series;
and obtaining the center wavelength and the spectral resolution of different spectral bands under different integration levels after the calculation of the different integration levels.
7. The method according to claim 1, wherein the calculating the relative radiation scaling coefficients of different spectral bands according to the nonlinear-culled output response image, the input radiation brightness and the least square method specifically includes:
calculating a first response value of each column of pixels of different spectral bands under different input radiation brightness according to the output response image and the input radiation brightness;
acquiring second response values of a plurality of detectors in the hyperspectral camera;
calculating the linear relation between the first response value and the second response value through a least square method;
and calculating the relative radiation calibration coefficients of different spectral bands according to the linear relation and the calculation rule under different spectral bands.
8. A radiation targeting system for a hyperspectral camera, comprising:
the first module is used for carrying out spectrum calibration on the hyperspectral camera to obtain different spectral response curves under different integration series;
the second module is used for calculating the center wavelength and the spectral resolution of different spectral bands under different integration stages according to the response curve;
a third module for matching radiation sources of different spectral channels according to the center wavelength and the spectral resolution;
a fourth module, configured to perform radiometric calibration on the hyperspectral camera by using a radiation light source to obtain radiation data of different spectral bands;
a fifth module, configured to acquire data of the radiation data of different spectral bands by using an extremum traversal method, so as to obtain input radiation brightness and output response images of different spectral bands;
a sixth module, configured to perform nonlinear rejection on the input radiation brightness and the output response image of different spectral bands by using a least square method, and then calculate to obtain absolute radiation calibration coefficients of different spectral bands;
and a seventh module, configured to calculate, according to the output response image after nonlinear rejection, the input radiation brightness, and a least square method, a relative radiation scaling coefficient of different spectral bands.
9. A radiation targeting device for a hyperspectral camera, comprising:
at least one processor;
at least one memory for storing at least one program;
the at least one program, when executed by the at least one processor, causes the at least one processor to implement the method of any of claims 1-7.
10. A computer readable storage medium, in which a processor executable program is stored, characterized in that the processor executable program is for performing the method according to any of claims 1-7 when being executed by a processor.
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