CN110120077A - A kind of in-orbit relative radiometric calibration method of area array cameras based on attitude of satellite adjustment - Google Patents
A kind of in-orbit relative radiometric calibration method of area array cameras based on attitude of satellite adjustment Download PDFInfo
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Abstract
A kind of area array cameras in-orbit relative radiometric calibration method based on attitude of satellite adjustment before satellite progress pose adjustment is imaged over the ground, needs the CCD imaging parameters setting to the focal plane of satellite consistent；Ground uniformly dark target is chosen, this uniformly can according to target be covered by satellite imagery multirow；Satellite can be adjusted to normal attitude, be obtained the image of uniformly dark target, count image DN value, take average DN value as system dark signal by under conditions of the covering of satellite imagery multirow by meeting uniformly dark target；Satellite carries out pose adjustment and obtains ground image so that being imaged over the ground after Satellite CCD face array length edge direction is consistent with satellite flight direction, and satellite returns to satellite normal attitude；Image procossing is carried out to ground image, image carries out in-orbit relative calibration to treated, and according to the response consistency of satellite transit and face battle array optical camera, dynamic acquisition relative radiometric calibration coefficient guarantees in-orbit relative calibration precision.
Description
Technical field
The present invention relates to a kind of in-orbit relative radiometric calibration methods of area array cameras based on attitude of satellite adjustment, belong to radiation
Calibration technology field.
Background technique
Imaging-type optical camera before satellite launch can be calibrated on ground, but they enter the orbit after must be reset
Mark is declined with imaging performance caused by drift, particle pollution for eliminating calibration coefficient etc..Since these calibration variations are more or less
Independently of between detection member, therefore in-orbit relative calibration is necessary.Relative calibration is exactly as its name suggests not need absolute radiation
The transmitting or calibration of magnitude, and only pay close attention between the detector in each channel of photoelectronic imaging/detection system and detector array
Rdaiation response performance difference between pixel and how to eliminate this kind of difference.The focal plane subassembly of imaging-type optical camera generally needs
Splice, this results in response between imaging detector piece and piece and has differences, in addition the pixel difference of imaging detector itself
And the slit of splicing, it can all be had an impact to being ultimately imaged, be embodied in face battle array optical camera to large area homogeneous target
When imaging simultaneously unevenly but there is obvious partially bright or partially dark striped in image output.
Area array cameras carry out relative calibration can determine the relationship between area array cameras output characteristics, as between pixel uniformly
Property, nonlinearity etc., then picture noise is eliminated by image inverting, improve imaging effect.
Under lab, it is fairly simple (integrating sphere light source or big diffusing reflection plate) but right to generate a uniform surface light field
It is very difficult that a uniform atural object is shot in rail level battle array optical camera, this is because a typical imaging region (number on ground
Ten to kilometers up to a hundred) it is difficult have the consistent homogeneous target of numerous radiation characteristics.Deep space is a good uniform field, but is only suitable only for
In measurement bias level, calculating relative gain needs certain spoke brightness.In solar irradiation area, ocean is comparatively ideal uniform
Field but luminance shortage, cannot well calibrate the entire dynamic range of equipment.In north African, there are many relatively uniform sand
Unconcerned target, but area is not again sufficiently large for the in-orbit relative calibration of most of optical cameras.
Summary of the invention
Present invention solves the technical problem that are as follows: it overcomes the shortage of prior art, a kind of face based on attitude of satellite adjustment is provided
The in-orbit relative radiometric calibration method of array camera, what this method combination attitude of satellite adjusted, ground uniform field scape is imaged and optimizes
The advantage of relative calibration algorithm, according to the response consistency of satellite transit and face battle array imaging surface battle array optical camera, dynamic acquisition phase
To radiation calibration coefficient, guarantee in-orbit relative calibration precision；
A kind of technical solution that the present invention solves are as follows: in-orbit relative radiometric calibration of area array cameras based on attitude of satellite adjustment
Method, steps are as follows:
1) before satellite progress pose adjustment is imaged over the ground, need the planar array detector imaging parameters setting to satellite consistent；
2) ground uniformly dark target is chosen, uniformly dark target can be covered by satellite imagery multirow for this, specific preferred embodiment
Are as follows: when ground is imaged in satellite area array cameras single, Polaroid area size, which is equivalent to satellite area array cameras detector, to be had
Size is imitated in the size of floor projection area, chooses ground uniformly dark target area, it is general to choose calmness to the regional imaging
Lake water or sea, choose shooting region can cover satellite single to ground be imaged when area size.
3) meeting uniformly dark target can be by under conditions of the covering of satellite imagery multirow, and satellite carries out pose adjustment, passes through
Gesture stability makes satellite yaw angle go to 90 ° from 0 °, so that satellite planar array detector longitudinal direction and satellite flight direction one
It causes, it is imaged over the ground, obtains the image of uniformly dark target, count image DN value (gray value), take average DN value dark as system
Signal (DN)-_Sdark；
4) satellite keeps 90 ° of yaw angle of posture, and satellite planar array detector longitudinal direction is consistent with satellite flight direction,
Under this condition, being imaged over the ground, ground image is obtained；So that satellite yaw angle is returned to 0 ° from 90 ° by gesture stability, that is, returns to satellite
Normal attitude；
5) image procossing is carried out to the ground image that step 4) obtains, so that same atural object approximation is in the same horizontal line；
6) in-orbit relative calibration is carried out to step 5) treated image, obtains each pixel responsiveness of planar array detector
Correction coefficient and system dark signal correction coefficient；Secretly believed according to the correction coefficient of each pixel responsiveness of planar array detector and system
Number correction coefficient, the image after being calibrated；
7) judgment step 6) whether the image after obtained calibration there is Strip phenomenon, if there is Strip phenomenon, according to item
Band evaluation condition judges whether to need to re-scale, if desired, return step 4), otherwise, it is determined that the image after step 6) calibration
It meets the requirements, completes calibration, the processing for subsequent in-orbit image.
The covering of satellite image multirow, refers to: the unilateral length of uniform field is greater than satellite face battle array optical camera face battle array narrow side length.
The imaging parameters setting of the planar array detector of satellite is consistent, comprising: the setting of each pixel of planar array detector is all provided with
It is set to unified time for exposure and gain.
Planar array detector is preferably panchromatic CCD
Uniformly dark target refers to: uniformly dark target and uniform scene be not be overlapped；
Uniform dark target, preferably includes: ocean, tranquil lake surface.
Satellite area array cameras, including planar array detector (preferably area array CCD and face battle array cmos detector), electronics equipment and
Optical machine main body.Planar array detector is mainly responsible for photosensitive, converts digital signal for the scenery that satellite area array cameras is shot；Electronics
Equipment is responsible for powering to area array cameras, controls camera and processing image information etc.；Optical machine main body by area array cameras structure and light
Camera lens composition is learned, optical lens is mounted in the structure of area array cameras, and planar array detector, electronics equipment are also mountable in face battle array
In the structure of camera.
Planar array detector is preferably in rectangle, preferably 7920 × 6144 planar array detector, and 7920 × 6144 indicate face array length
While being 7920 pixels, short side is 6144 pixels.
Band evaluation condition specifically: the image after step 6) calibration is chosen to be evaluated image, takes evaluated image
Column average, by the image after column average pass through respectively one by 101 smooth rank median filters of 25 rank sample means and
One 2001 rank median filter smooth by 51 rank sample means, obtains two curves, two curve absolute value of the difference are anti-
The band situation of entire image is reflected；If two curve differences are met the requirements, judgement meets band evaluation condition, otherwise, it is determined that
It is unsatisfactory for band evaluation condition；
Step 2) chooses ground uniformly dark target, and uniformly dark target can be covered by satellite imagery multirow for this, preferred embodiment
Are as follows: when ground is imaged in satellite area array cameras single, Polaroid area size, which is equivalent to satellite area array cameras detector, to be had
Size is imitated in the size of floor projection area, chooses ground uniformly dark target area, it is general to choose calmness to the regional imaging
Lake water or sea, choose shooting region can cover satellite single to ground be imaged when area size.
Step 5) carries out image procossing to the ground image that step 4) obtains, so that same atural object is in the same horizontal line,
Preferred embodiment are as follows: after attitude of satellite adjustment, the same area is imaged in each pixel of planar array detector, and obtaining image is in 45 ° (i.e. 45 °
Leveling), imaging relations are as shown in Figure 3.Image progressive adjustment, with the first row first row gray value of image DN1,1On the basis of, it will incline
Oblique 45 ° of image correction is same horizontal line, so that same atural object approximation is in the same horizontal line, as shown in formula (1-1).
Step 6) carries out in-orbit relative calibration to step 5) treated image, obtains the school of each pixel responsiveness of CCD
Positive coefficient and system dark signal correction coefficient；Specifically: in-orbit relative calibration is carried out to the image after 45 ° of step 5) leveling, is obtained
To the correction coefficient and system dark signal correction coefficient of each pixel responsiveness of CCD；According to the correction of each pixel responsiveness of CCD
Coefficient and system dark signal correction coefficient, the image after being calibrated, satellite area array cameras relative calibration expression formula have the table of choosing
It is as follows up to formula:
In formula:
The output of-dark signal, the fitting coefficient of least squares fitting curve；
- each pixel responsiveness；
In Laboratory Calibration, under same spoke brightness, the DN value of each pixel is calculated, the gray scale for acquiring all pixels is average
ValueThen under different luminance points, all pixel average gray are sought, the function between average gray value and spoke brightness closes
System is expressed as follows by least square method:
In formula:
The output of-average dark signal, the fitting coefficient of least squares fitting curve；
The average response degree of-all pixels, the fitting coefficient of least squares fitting curve；
Step 3. Satellite is to uniform dark target imaging (such as ocean, tranquil lake surface etc.), statistics
The average value of each pixel is as in-orbit relative calibration dark signal value
Homogeneous target is imaged after attitude of satellite adjustment, the radiant illumination of each pixel is consistent that (ground object target is more equal
Even, calibration effect is better).After planar array detector output gray level image is changed into satellite area array cameras incidence spoke luminance picture,
The corresponding radiance L of each pixelm,n(unified to be indicated with L), camera input radiance retrieval formula should be consistent are as follows:
It is as follows that formula (1-4) substitution formula (1-3) obtains average DN value expression:
To take average gray value (i.e. to each pixel gray value of homogeneous target imaging after attitude of satellite adjustment)；Each pixel number value after enabling relative calibration is equal to average code value (i.e.)；Dark signal value is
Each pixel dark signal output is acquired (i.e. to the dark target such as ocean)；Gray value after then correcting is write
Are as follows:
In formula:
The correction coefficient-of pixel responsiveness
Dark signal correction coefficient-
It brings correction coefficient into formula (1-6) and obtains the correction function matrix of in-orbit relative calibration:
The image after obtaining in-orbit relative radiometric calibration is handled in-orbit image using formula (1-7).
Step 7) judgment step 6) whether the image after obtained calibration there is Strip phenomenon, if there is Strip phenomenon, root
According to band evaluation condition, judge whether to need to re-scale, if desired, return step 4), otherwise, it is determined that after step 6) calibration
Image meets the requirements, and preferred embodiment is as follows:
The average value of each column of image after taking step 6) to calibrate, becomes one-dimensional curve shape for the Two dimensional Distribution of face system of battle formations picture
Formula, the one-dimensional curve after being averaged pass through one by 101 smooth rank median filters of 25 rank sample means and one respectively
By 2001 smooth rank median filters of 51 rank sample means, two curves are obtained, two curve differences form a new song
Line, the absolute value of new curve reflect the band situation of image after calibration, and each spike of new curve indicates a band, if newly
Curve has more than 3 obvious spikes, then the image after step 6) calibration is undesirable, need to re-scale.
The advantages of the present invention over the prior art are that:
(1) present invention takes full advantage of the ability of satellite platform yaw-position adjustment, is imaged in conjunction with to ground uniform field scape
With the advantage of the relative calibration algorithm of optimization, the satellite face battle array in-orbit relative radiometric calibration of optical camera is easily realized；
(2) present invention substantially reduces the area coverage being imaged over the ground due to the imaging pattern using attitude of satellite adjustment,
Both the uniformity that ensure that ground scene also reduces dependence of the in-orbit relative calibration to dedicated calibration field；
(3) present invention takes into account satellite optical camera imaging model using matrix model using the relative calibration algorithm of optimization
With the programmability of scaling algorithm, the jump of face battle array optical camera focal plane arrays (FPA) splicing is overcome, to satellite face battle array optics phase
The in-orbit relative calibration of machine has stronger practicability；
(4) present invention due to being imaged the small advantage of area coverage over the ground, to multi-detector splicing and detector in rectangle
The in-orbit relative calibration of optical camera has very strong Practical significance；
(5) present invention is assessed by band guarantees scaled quality, essentially eliminates the band of remote sensing images, ensure that image
Radiation quality.
(6) the present invention is based on the in-orbit relative calibration concepts of attitude of satellite adjustment, as the acquisition earth table from track
The face battle array optical camera of face information generates a homogeneous target.The purpose for generating homogeneous target is in order to which face battle array optical camera is each
Detection member can receive identical spoke brightness.After attitude of satellite adjustment, satellite face battle array optical camera is made by spinning satellite
Identical ground target is imaged in each detection pixel, does not have to use special ground calibration field, as long as there is the equal of fritter on ground
It can be carried out to shimming in-orbit relative calibration.The common calibrating method of the technological improvement reduces the band on image, obtains
Better than the image of Nonuniformity Correction, the standard for calculating relative gain can be used as.
Detailed description of the invention
Fig. 1 is the in-orbit relative radiometric calibration flow chart based on attitude of satellite adjustment；
Fig. 2 is perspective view of the attitude of satellite adjustment front and back detector focal plane on ground；
Fig. 3 is the detector pixel arrangement schematic diagram of attitude of satellite adjustment front and back；
Specific embodiment
The invention will be described in further detail in the following with reference to the drawings and specific embodiments.
A kind of in-orbit relative radiometric calibration method of area array cameras based on attitude of satellite adjustment of the present invention, satellite carry out posture
Before adjustment is imaged over the ground, need the CCD imaging parameters setting to the focal plane of satellite consistent；Ground uniformly dark target is chosen, it should
Uniformly it can according to target be covered by satellite imagery multirow；Meet the condition that uniformly dark target can be covered by satellite imagery multirow
Under, satellite is adjusted to normal attitude, is obtained the image of uniformly dark target, is counted image DN value, take average DN value as system
Dark signal；Satellite carries out pose adjustment, so that be imaged over the ground after Satellite CCD face array length edge direction is consistent with satellite flight direction,
Ground image is obtained, satellite returns to satellite normal attitude；Image procossing is carried out to ground image, image carries out to treated
Rail relative calibration, according to the response consistency of satellite transit and face battle array optical camera, dynamic acquisition relative radiometric calibration coefficient is protected
Demonstrate,prove in-orbit relative calibration precision.
The present invention on the battle array in-orbit relative calibration of optical camera of face, obviously eliminated by image inverting by the image after calibration
Picture noise improves imaging effect.Original in-orbit relative calibration is needed using dedicated ground calibration field, and dedicated ground is fixed
Mark field requires atural object uniform, and diffusing characteristic diffuser is good, so as to simulation laboratory's internal calibration, generates a uniform surface light field.But it is in-orbit
It is very difficult that optical camera shoots a uniform atural object, this is because a typical imaging region is (tens of to up to a hundred on ground
Kilometer) it is difficult have the consistent homogeneous target of numerous radiation characteristics.Deep space is a good uniform field, but it is inclined to be only adapted to measurement
Level is set, calculating relative gain needs certain spoke brightness.In solar irradiation area, ocean is comparatively ideal uniform field but brightness
Deficiency cannot well calibrate the entire dynamic range of equipment.In north African, there are many relatively uniform desert targets, but
Equably object plane product is not again sufficiently large on ground for the in-orbit relative calibration of most of optical cameras.This patent is based on the attitude of satellite
The in-orbit relative calibration concept of adjustment scans the face each detection pixel of battle array optical camera detector by spinning satellite identical
Ground target, to complete the generation of uniform field.The technology does not have to selection and does not have to use special ground calibration field, as long as ground has
The uniform place of fritter can be carried out in-orbit relative calibration.The common calibrating method of the technological improvement, subtracts the band on image
It is few, the image better than Nonuniformity Correction has been obtained, can be used as the standard for calculating relative gain.It, can by using the technology
So that the relative calibration of satellite in orbit by it is pervious annually or several times, develop the calibration mode for business normalization.
Knot attached drawing is described in detail the present invention below, and specific steps realize that process is as follows:
1. choosing uniform earth's surface, guarantee that the unilateral length of uniform scene is greater than satellite face battle array optical camera in the projection on ground
N, as shown in Figure 2.If the detector of satellite face battle array optical camera is made of two pieces of face battle array rectangular detectors, the ruler of rectangular detector
Very little is 7800 pixels × 5400 pixels, and the face battle array that two pieces of detector long side splicings form a 15600 pixel × 5400 pixels is burnt
Plane, on the track of 500km, imaging area is 15.6km × 5.4km to single over the ground.It is in-orbit opposite for this area array cameras
When calibration, the unilateral length of the uniform scene in ground is greater than 5.4km.
2. choosing ground uniformly dark target, uniformly dark target can be covered by satellite imagery multirow for this, preferred embodiment are as follows: defend
When ground is imaged in star area array cameras single, Polaroid area size is equivalent to satellite area array cameras detector effective dimensions
In the size of floor projection area, ground uniformly dark target area is chosen, it is general to choose tranquil lake water to the regional imaging
Or sea, the region for choosing shooting can cover area size of the satellite single to ground imaging when.The area array cameras single pair
Ground imaging area is 15.6km × 5.4km, chooses target of the lake surface greater than 5.4km as uniform dark target.
3. meeting uniformly dark target can be by under conditions of the covering of satellite imagery multirow, satellite carries out pose adjustment, passes through
Gesture stability makes satellite yaw angle go to 90 ° from 0 °, so that 15600 pixel of satellite planar array detector (long side) direction and satellite fly
Line direction is consistent, is imaged over the ground, obtains the image of uniformly dark target, counts image DN value (gray value), average DN value is taken to make
For system dark signal (DN)-_ Sdark；
4. satellite keeps 90 ° of yaw angle of posture, 15600 pixel of satellite planar array detector (long side) direction and satellite flight
Direction is consistent, under this condition, is imaged over the ground, obtains ground image；Satellite yaw angle is returned to from 90 ° by gesture stability
0 °, that is, return to satellite normal attitude；
5. the ground image that pair step 4) obtains carries out image procossing, so that same atural object approximation is in the same horizontal line,
After attitude of satellite adjustment, the same area is imaged in each pixel of planar array detector, and obtaining image is in 45 °, imaging relations such as Fig. 3 institute
Show.Image progressive adjustment, with the first row first row gray value of image DN1,1On the basis of, it is same by the image correction for tilting 45 °
Horizontal line, so that same atural object approximation is in the same horizontal line, as shown in formula (1-1).
At this point, it is preferred that m=15600, n=5400
6. the image after 45 ° of pair step 5) leveling carries out in-orbit relative calibration, the correction of each pixel responsiveness of CCD is obtained
Coefficient and system dark signal correction coefficient；According to the correction coefficient and system dark signal correction coefficient of each pixel responsiveness of CCD,
Image after being calibrated, satellite area array cameras relative calibration expression formula:
In formula:
The output of-dark signal, the fitting coefficient of least squares fitting curve；
- each pixel responsiveness；
In Laboratory Calibration, under same spoke brightness, the DN value of each pixel is calculated, the gray scale for acquiring all pixels is average
ValueThen under different luminance points, all pixel average gray are sought, the function between average gray value and spoke brightness closes
System is expressed as follows by least square method:
In formula:
The output of-average dark signal, the fitting coefficient of least squares fitting curve；
The average response degree of-all pixels, the fitting coefficient of least squares fitting curve；
Step 3. Satellite is to uniform dark target imaging (such as ocean, tranquil lake surface etc.), statisticsThe average value of each pixel is as in-orbit relative calibration dark signal value
Homogeneous target is imaged after attitude of satellite adjustment, the radiant illumination of each pixel is consistent that (ground object target is more equal
Even, calibration effect is better).After planar array detector output gray level image is changed into satellite area array cameras incidence spoke luminance picture,
The corresponding radiance L of each pixelm,n(unified to be indicated with L), camera input radiance retrieval formula should be consistent are as follows:
It is as follows that formula (1-4) substitution formula (1-3) obtains average DN value expression:
To take average gray value (i.e. to each pixel gray value of homogeneous target imaging after attitude of satellite adjustment)；Each pixel number value after enabling relative calibration is equal to average code value (i.e.)；Dark signal value is
Each pixel dark signal output is acquired (i.e. to the dark target such as ocean)；Gray value after then correcting is write
Are as follows:
In formula:
The correction coefficient-of pixel responsiveness
Dark signal correction coefficient-
It brings correction coefficient into formula (1-6) and obtains the correction function matrix of in-orbit relative calibration:
The image after obtaining in-orbit relative radiometric calibration is handled in-orbit image using formula (1-7).
7. the average value of each column of the image after taking step 6) to calibrate, becomes one-dimensional curve for the Two dimensional Distribution of face system of battle formations picture
Form, the one-dimensional curve after being averaged pass through a 101 rank median filters and one smooth by 25 rank sample means respectively
A 2001 rank median filters smooth by 51 rank sample means, obtain two curves, two curve differences formed one it is new
Curve, the absolute value of new curve reflect the band situation of image after calibration, and each spike of new curve indicates a band, if
New curve has more than 3 obvious spikes, then the image after step 6) calibration is undesirable, need to re-scale.
Based on the in-orbit relative calibration concept of attitude of satellite adjustment, as the face for obtaining earth surface information from track
Battle array optical camera generates a homogeneous target.The purpose for generating homogeneous target is in order to which the face battle array each detection member of optical camera can connect
Receive identical spoke brightness.After attitude of satellite adjustment, each detection picture of satellite face battle array optical camera is made by spinning satellite
Identical ground target is imaged in member, does not have to use special ground calibration field, as long as ground has the uniform place of fritter can
To carry out in-orbit relative calibration.The common calibrating method of the technological improvement reduces the band on image, has obtained better than non-homogeneous
Property correction image, can be used as calculate relative gain standard.
The present invention takes full advantage of the ability of satellite platform yaw-position adjustment, easily realizes satellite face battle array optics phase
The in-orbit relative radiometric calibration of machine；The present invention uses the imaging pattern of attitude of satellite adjustment, substantially reduces the covering being imaged over the ground
Area both ensure that the uniformity of ground scene, also reduce dependence of the in-orbit relative calibration to dedicated calibration field；
The present invention using optimization relative calibration algorithm, using matrix model, take into account satellite optical camera imaging model with
The programmability of scaling algorithm overcomes the jump of face battle array optical camera focal plane arrays (FPA) splicing, to satellite face battle array optical camera
In-orbit relative calibration has stronger practicability；The present invention can make the relative calibration of satellite in orbit by it is pervious annually or
Several times, develop the calibration mode (once a week or one month twice) for business normalization.
The present invention chooses uniform earth's surface as shown in Figure 1, guarantees that the unilateral length of uniform scene is greater than satellite face battle array optics phase
Machine ground projection N, as shown in Figure 2.Imaging parameters setting needs all detections in focal plane before carrying out attitude of satellite adjustment
The imaging parameters setting of device is consistent, and such as panchromatic CCD is set as unified time for exposure and gain entirely；Satellite to uniform dark target at
As (such as ocean, tranquil lake surface etc.), statistical picture DN value (gray value) takes average DN value as system dark signalAttitude of satellite adjustment, optical surface battle array optical camera and satellite are connected, and the adjustment attitude of satellite makes optical surface battle array optics phase
Projection of the detector of machine on ground is rotated by 90 °, as shown in Fig. 2, making detector longitudinal direction consistent with heading.Posture
Projected length N after adjustment on ground is far smaller than M, when choosing uniform earth's surface progress in-orbit relative calibration test, lesserly
Face scene can covering surface battle array optical camera whole pixels, for wide visual field space optical camera, this method is especially advantageous.
After attitude of satellite adjustment, each pixel of detector is successively imaged same atural object, and obtaining image is in 45 °, imaging relations
As shown in Figure 3.Since pose adjustment imaging time section is very short, it is believed that same atural object visits first gray value showed i.e. different
Caused by inconsistency to visit member response；
Image procossing after pose adjustment, to obtain imaging of the detector under same atural object, image progressive adjustment, with first
Row first row gray value of image DN1,1On the basis of, it is same horizontal line by the image correction for tilting 45 °, so that same atural object is approximate
In the same horizontal line, as shown in formula (1-1)；
Relative calibration carries out in-orbit relative calibration processing on the image that 45 ° level, at formula (1-2)~(1-7)
Reason, is calculated the correction coefficient and dark signal corrected value of each pixel responsiveness, carries out in-orbit relative calibration correction by pixel；
Satellite face battle array optical camera relative calibration expression formula:
In formula:
The output of-dark signal, the fitting coefficient of least squares fitting curve；
- each pixel responsiveness；
In Laboratory Calibration, under same spoke brightness, the DN value of each pixel is calculated, the gray scale for acquiring all pixels is average
ValueThen under different luminance points, all CCD pixel average gray, the letter between average gray value and spoke brightness are asked
Number relationship is expressed as follows by least square method:
In formula:
The output of-average dark signal, the fitting coefficient of least squares fitting curve；
The average response degree of-all pixels, the fitting coefficient of least squares fitting curve；
Step 3. Satellite is to uniform dark target imaging (such as ocean, tranquil lake surface etc.), statisticsThe average value of each pixel is as in-orbit relative calibration dark signal value
Homogeneous target is imaged after attitude of satellite adjustment, the radiant illumination of each pixel is consistent that (ground object target is more equal
Even, calibration effect is better).After detector output gray level image is changed into satellite face battle array optical camera incidence spoke luminance picture,
The corresponding radiance L of each pixelm,n(unified to be indicated with L), camera input radiance retrieval formula should be consistent are as follows:
It is as follows that formula (1-4) substitution formula (1-3) obtains average DN value expression:
To take average gray value (i.e. to each pixel gray value of homogeneous target imaging after attitude of satellite adjustment)；Each pixel number value after enabling relative calibration is equal to average code value (i.e.)；Dark signal value is
Each pixel dark signal output is acquired (i.e. to the dark target such as ocean)；Gray value after then correcting is write
Are as follows:
In formula:
The correction coefficient-of pixel responsiveness
Dark signal correction coefficient-
It brings correction coefficient into formula (1-6) and obtains the correction function matrix of in-orbit relative calibration:
The image after obtaining in-orbit relative radiometric calibration is handled in-orbit image using formula (1-7).
The pixel responsiveness correction coefficient and dark signal correction coefficient that calibrating method of the invention obtains do not adapt to own
The processing of ground scenery, to the water body of uniform scene such as Low emissivity magnitude, the rainforest of Intermediate radiation magnitude, the sand of height radiation magnitude
Strip phenomenon can be clearly observed from image when desert, snowfield, cloud layer imaging.It needs to carry out calibration treated image
Relative detector calibration is assessed, and the band situation of image, determines satellite sensor picture according to the statistical result of band after statistical correction
Whether member response and dark signal corrected value need to reset mark；
Band assessment of the invention takes the column average of chosen assessment image, and averagely rear image is passed through a warp respectively
Cross 101 smooth rank median filters of 25 rank sample means and a 2001 rank median filterings smooth by 51 rank sample means
Device obtains two curves.The latter filter removes spike and striped in image.Two curve absolute value of the difference reflect
The band situation of entire image, wherein the spike of curve indicates a separate panels.The band assessed value of whole image is all
Separate panels are averaged.
Pixel responsiveness correction coefficient and dark signal correction coefficient by assessment, as in-orbit relative detector calibration system
Number need to re-start band assessment without band assessment, meet band evaluation condition for the processing of subsequent in-orbit image,
Finally realize radiation calibration.
Unspecified part of the present invention belongs to common sense well known to those skilled in the art.
Claims (10)
1. a kind of in-orbit relative radiometric calibration method of area array cameras based on attitude of satellite adjustment, it is characterised in that steps are as follows:
1) before satellite progress pose adjustment is imaged over the ground, need the planar array detector imaging parameters setting to satellite consistent；
2) ground uniformly dark target is chosen, uniformly dark target can be covered by satellite imagery multirow for this；
3) meeting uniformly dark target can be by under conditions of the covering of satellite imagery multirow, and satellite carries out pose adjustment, passes through posture
Control makes satellite yaw angle go to 90 ° from 0 °, so that satellite planar array detector longitudinal direction is consistent with satellite flight direction, over the ground
Imaging obtains the image of uniformly dark target, counts image DN value, take average DN value as system dark signal (DN)-_ Sdark；
4) satellite keeps 90 ° of yaw angle of posture, and satellite planar array detector longitudinal direction is consistent with satellite flight direction, at this
It under part, is imaged over the ground, obtains ground image；So that satellite yaw angle is returned to 0 ° from 90 ° by gesture stability, that is, it is normal to return to satellite
Posture；
5) image procossing is carried out to the ground image that step 4) obtains, so that same atural object is in the same horizontal line；
6) in-orbit relative calibration is carried out to step 5) treated image, obtains the correction of each pixel responsiveness of planar array detector
Coefficient and system dark signal correction coefficient；According to the correction coefficient of each pixel responsiveness of planar array detector and system dark signal school
Positive coefficient, the image after being calibrated；
7) judgment step 6) whether the image after obtained calibration there is Strip phenomenon, if there is Strip phenomenon, commented according to band
Estimate condition, judge whether to need to re-scale, if desired, return step 4), otherwise, it is determined that the image after step 6) calibration meets
It is required that.
2. a kind of in-orbit relative radiometric calibration method of area array cameras based on attitude of satellite adjustment according to claim 1,
It is characterized by: satellite image multirow covers, refer to: it is long that the unilateral length of uniform field is greater than satellite face battle array optical camera face battle array narrow side
Degree.
3. a kind of in-orbit relative radiometric calibration method of area array cameras based on attitude of satellite adjustment according to claim 1,
It is characterized by: the imaging parameters setting of the planar array detector of satellite is consistent, comprising: the setting of each pixel of planar array detector,
It is disposed as unified time for exposure and gain.
4. a kind of in-orbit relative radiometric calibration method of area array cameras based on attitude of satellite adjustment according to claim 1,
It is characterized by: planar array detector is panchromatic CCD.
5. a kind of in-orbit relative radiometric calibration method of area array cameras based on attitude of satellite adjustment according to claim 1,
It is characterized by: uniform dark target specifically: uniformly dark target and uniform scene be not be overlapped.
6. a kind of in-orbit relative radiometric calibration method of area array cameras based on attitude of satellite adjustment according to claim 1,
It is characterized by: uniform dark target, comprising: ocean, tranquil lake surface.
7. a kind of in-orbit relative radiometric calibration method of area array cameras based on attitude of satellite adjustment according to claim 1,
It is characterized by: the area array cameras of satellite, including planar array detector, electronics equipment and optical machine main body, planar array detector can
It carries out photosensitive, converts digital signal for the scenery that satellite area array cameras is shot；Electronics equipment be used for power supply to area array cameras,
Control camera and processing image information；Optical machine main body is made of the structure and optical lens of area array cameras.
8. a kind of in-orbit relative radiometric calibration method of area array cameras based on attitude of satellite adjustment according to claim 1,
It is characterized by: planar array detector is in rectangle, rectangle is that 7920 × 6144,7920 × 6144 expression face array length sides are 7920 pictures
Member, short side are 6144 pixels.
9. a kind of in-orbit relative radiometric calibration method of area array cameras based on attitude of satellite adjustment according to claim 1,
It is characterized by: band evaluation condition specifically: the image after step 6) calibration is chosen to be evaluated image, takes evaluated figure
Image after column average is passed through a 101 rank median filters smooth by 25 rank sample means by the column average of picture respectively
With a 2001 rank median filters smooth by 51 rank sample means, two curves, two curve absolute value of the difference are obtained
Reflect the band situation of entire image；If two curve differences are met the requirements, judgement meets band evaluation condition, otherwise, sentences
Surely it is unsatisfactory for band evaluation condition.
10. a kind of in-orbit relative radiometric calibration method of area array cameras based on attitude of satellite adjustment according to claim 1,
It is characterized by: step 2) chooses ground uniformly dark target, uniformly dark target can be covered by satellite imagery multirow for this, specifically
Are as follows: when ground is imaged in satellite area array cameras single, Polaroid area size, which is equivalent to satellite area array cameras detector, to be had
Size is imitated in the size of floor projection area, ground uniformly dark target area is chosen, to the regional imaging, chooses tranquil lake
Water or sea, the region for choosing shooting can cover area size of the satellite single to ground imaging when.
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