CN102752504B - Relative radiation correction method for wide-view-field linear array CCD (Charge Coupled Device) camera - Google Patents

Relative radiation correction method for wide-view-field linear array CCD (Charge Coupled Device) camera Download PDF

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CN102752504B
CN102752504B CN201210243727.3A CN201210243727A CN102752504B CN 102752504 B CN102752504 B CN 102752504B CN 201210243727 A CN201210243727 A CN 201210243727A CN 102752504 B CN102752504 B CN 102752504B
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visual field
view
linear array
array ccd
ccd camera
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CN102752504A (en
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王爱春
傅俏燕
闵祥军
潘志强
韩启金
李晓进
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China Center for Resource Satellite Data and Applications CRESDA
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Abstract

The invention relates to a relative radiation correction method for a wide-view-field linear array CCD (Charge Coupled Device) camera, which comprises the following steps: (1) selecting a uniform scene image; (2) dividing sub view fields by dividing detection image elements of the linear array CCD camera into different view fields by separating the view field angles of the wide-view-field linear array CCD camera at preset angular intervals; (3) calculating the widths of different sub view fields and the number of the contained detection image elements; (4) calculating an average value of the detection image elements DN in each of the sub view fields and calculating a yield value of the detection image elements in each of the sub view fields, according to the obtained number of the detection image elements; (5) on the basis of the sub view fields at the angular intervals, re-dividing the sub-view-fields into different sub-view-field areas at equimultiple angular intervals according to the multiple of the angular intervals, repeating the steps (3) and (4) for different areas, thereby performing uniform scene calculation on the sub-view-field areas at different multiple angular intervals; and (6) integrally fitting different yield values of the detection image elements in each of the sub view fields obtained by calculating the sub-view-field areas at different multiple angular intervals, thereby obtaining a relative radiation correction coefficient of the wide-view-field linear array CCD camera.

Description

A kind of relative radiometric correction method of wide visual field linear array CCD camera
Technical field
The present invention relates to a kind of relative radiometric correction method of wide visual field linear array CCD camera, particularly a kind of relative detector calibration of environment disaster reduction satellite multispectral camera.
Background technology
The angle of visual field of linear array CCD camera limits the swath width of scanning, make remotely-sensed data realize round-the-clock, limited during the earth observation of round-the-clock, by increasing the length of line array CCD, increase the angle of visual field, the swath width of sensor scan can be made to increase, but field of view edge responsiveness is low, the restriction of raying brightness measurement technology, very difficult acquisition is terrestrial information as far as possible comprehensively, this makes to adopt total visual field of single-lens linear array CCD camera can not be very large, for this reason by two compared with small field of view and optical axis has two linear array CCD cameras of certain angle to carry out field stitching, thus realize the imaging on a large scale of wide visual field, such as, the angle of visual field after environment disaster reduction satellite two linear CCD assembling techniques is about at 57 ° (angle of visual field about 30 ° of angles of separate unit line array CCD imaging), one scape image just can cover 700km width, make the temporal resolution of CCD camera very high, the playback cycle only has 2 days, rapid evaluation can be carried out to the condition of a disaster.
In the ideal situation, the gray value that each pixel of linear array CCD camera exports is directly proportional to the spoke brightness of input, but due to each of ccd detector, each tap, each existence visiting the various destabilizing factor such as the pixel inconsistency of unit and the difference of circuit system causes its corresponding relation not exist, by relative detector calibration, the inconsistency between each pixel of line array CCD is corrected for this reason, the relative detector calibration of current satellite in orbit image often adopts even landscape statistic law, this method lacks the calibration data of launching front whole star docking to single-lens linear array CCD camera and the relative detector calibration of failing the internal calibration data obtained on star after launching obtains very good effect, but it is not but very desirable for adopting this kind of method to carry out relative detector calibration effect to the wide visual field linear array CCD camera that there is certain slanted angle, because the method does not consider that line array CCD inclination certain angle can introduce the picture planar light illumination nonlinear edge dim light phenomenon that pupil distorts, pupil type distorts and telecentricity causes, and this is a main source of error of wide visual field linear array CCD camera Non-uniform responsivity.
Summary of the invention
Technology of the present invention is dealt with problems and is: overcome the deficiencies in the prior art, and provide a kind of relative radiometric correction method of wide visual field linear array CCD camera, the method can solve the problem of wide visual field line array CCD imaging.
Technical solution of the present invention is: a kind of relative radiometric correction method of wide visual field linear array CCD camera, and step is as follows:
(1) even landscape image is chosen: require to cover all detection pixels, the instantaneous relative change of even landscape is less than the relative detector calibration required precision of satellite load;
(2) a point visual field is divided: the angle of visual field of wide visual field linear array CCD camera, with predetermined angle intervals, the detection pixel of linear array CCD camera is divided into different visual field;
(3) fabric width calculating different point visual field and the detection pixel number comprised;
(4) a point visual field even landscape corrects: detect pixel number according in obtained above point of visual field, calculates the mean value detecting pixel DN in each point of visual field, calculates the yield value detecting pixel in each point of visual field;
(5) field of view even landscape is divided to correct: to divide on the basis of visual field in above-mentioned angle intervals, angularly point visual field is divided into the difference point field of view of equimultiple angle intervals by the multiple at interval again, and this zones of different repetition step (3), (4) are carried out to different equimultiple angle intervals lower point of field of view even landscape and calculated;
(6) the entirety detection pixel of wide visual field linear array CCD camera corrects: Xia Fen visual field, above-mentioned different angles interval homogeneous area is calculated the different gains value detecting pixel in each point of visual field, carries out the relative detector calibration coefficient that overall fit can obtain wide visual field linear array CCD camera.
Described predetermined angle intervals is generally less than 1 °.
The present invention compared with prior art beneficial effect is:
(1) the present invention is directed to the imaging data feature of wide visual field linear array CCD camera, propose to adopt a point visual field even landscape statistic law, achieve the relative detector calibration technical problem of wide visual field linear array CCD camera.
(2) the present invention is according to the imaging geometry optics of wide visual field linear array CCD camera and photometry, loop iteration distribution is adopted to the angle of visual field of wide visual field linear array CCD camera, carry out a point visual field even landscape to correct, efficiently solve the picture planar light illumination nonunf ormity that wide visual field linear array CCD camera is caused by slanted angle.
(3) the present invention is the method that wide visual field linear array CCD camera proposes, and has taken into account wide visual field linear array CCD camera imaging characteristic and algorithm practicability, has also had very strong practicality to the application of homogeneous satellite.
Accompanying drawing explanation
Fig. 1 is the inventive method flow chart.
Embodiment
Below in conjunction with accompanying drawing, 1 couple of the present invention is described in detail, and concrete steps implementation procedure is as follows:
(1) even landscape image is chosen, and from angle of coverage, it requires to cover all detection units; Consider from angle of radiation, it requires that the instantaneous relative change (δ) of even landscape is less than the relative detector calibration required precision of satellite load, and 1. instantaneous relative change can calculate according to formula.
δ = σ DN / DN ‾ ①
In formula: for choosing the average of even landscape image DN value;
σ dNfor choosing the variance of even landscape image DN value;
(2) visual field is divided to divide, the angle of visual field θ of wide visual field linear array CCD camera fOV, with certain angle intervals, the detection pixel of linear array CCD camera is divided into different visual fields, and the fabric width calculating different point visual field and the detection pixel number comprised;
(2.1) angular divisions interval
Realize wide visual field by two linear array CCD camera field stitchings to cover, under its asterism, symmetrical placement divides visual field equally usually, and for this reason predetermined angle intervals θ is by the field of view angle of half divide equally for m decile, namely have 2. relation:
θ FOV 2 = m × θ ②
According to the linear array CCD camera angle of visual field to the impact analysis of transducer entrance pupil place radiance, suggestion arranges angle intervals θ and is less than 1 °, to realize high-precision relative detector calibration.
(2.2) visual field fabric width is divided to calculate
According to the relation of the angle of visual field, fabric width and satellite altitude, the fabric width L in each angle intervals 3. can be calculated by formula i;
L i+1＝[tan[(i+1)×θ]-tan[i×θ]]×H ③
In formula: i is i-th angle intervals, i ∈ [0, m-1];
H is satellite altitude;
L 0corresponding substar its as with reference to initial point;
(2.3) visual field fabric width contained detection pixel number is divided to calculate
By satellite ground pixel resolution GSD, contained detection pixel number N in each point of visual field fabric width 4. can be calculated by formula i;
N i = L i GSD ④
(3) divide visual field even landscape to correct, detect pixel number according in obtained above point of visual field, calculate the average detecting pixel DN in each point of visual field;
(4) yield value detecting pixel in each point of visual field 5. can be calculated by formula
G N i , j = DN i , j 1 N i Σ r = j N i + j DN i , r ⑤
In formula: N is total pixel number of linear array CCD camera;
R is the r pixel in i-th angle intervals, r ∈ [j, N i+ j];
J is the jth pixel dropping on linear array CCD camera in i-th angle intervals, herein for the ease of writing the initial pixel that it can be used as in i-th angle intervals, and j ∈ [1, N];
DN i, rthe DN value of r pixel in i-th angle intervals;
(5) field of view even landscape is divided to correct, divide on the basis of visual field at above-mentioned angle intervals θ, angularly point visual field is divided into the difference point field of view of equimultiple angle intervals by the multiple k θ at interval again, and this zones of different repetition step (3), (4) are carried out to different equimultiple angle intervals lower point of field of view even landscape and calculated;
Wherein: equimultiple angle intervals k θ, k ∈ [2, m];
Number of regions under k θ times angle intervals
K θ times of angle intervals lower area even landscape corrects pixel yield value and is designated as
(6) the entirety detection pixel of wide visual field linear array CCD camera corrects, and Xia Fen visual field, above-mentioned different angles interval homogeneous area is calculated the different gains value of each line array CCD detection pixel and carry out the relative detector calibration coefficient that overall fit can obtain wide visual field linear array CCD camera, the DN value utilizing original image and the relative detector calibration coefficient obtained are divided by, and obtain the image after radiant correction.
The unspecified part of the present invention belongs to general knowledge as well known to those skilled in the art.

Claims (2)

1. a relative radiometric correction method for wide visual field linear array CCD camera, is characterized in that step is as follows:
(1) even landscape image is chosen: require to cover all detection pixels, the instantaneous relative change of even landscape is less than the relative detector calibration required precision of satellite load;
(2) a point visual field is divided: the angle of visual field of wide visual field linear array CCD camera, with predetermined angle intervals, the detection pixel of linear array CCD camera is divided into different visual field;
(3) fabric width calculating different point visual field and the detection pixel number comprised;
(4) a point visual field even landscape corrects: detect pixel number according in obtained above point of visual field, calculates the mean value detecting pixel digital value DN in each point of visual field, calculates the yield value detecting pixel in each point of visual field;
(5) field of view even landscape is divided to correct: to divide on the basis of visual field in above-mentioned angle intervals, angularly point visual field is divided into the difference point field of view of equimultiple angle intervals by the multiple at interval again, and these different points of field of view repetition step (3), (4) are carried out to different equimultiple angle intervals lower point of field of view even landscape and calculated;
(6) the entirety detection pixel of wide visual field linear array CCD camera corrects: Xia Fen visual field, above-mentioned different angles interval homogeneous area is calculated the different gains value detecting pixel in each point of visual field, carry out the relative detector calibration coefficient that overall fit can obtain wide visual field linear array CCD camera, the image after utilizing the relative detector calibration coefficient obtained to obtain radiant correction.
2. the relative radiometric correction method of a kind of wide visual field linear array CCD camera according to claim 1, is characterized in that: described predetermined angle intervals is less than 1 °.
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CN104580944B (en) * 2013-10-10 2017-11-17 中国科学院光电研究院 The method that relative detector calibration is carried out to ccd image
CN103679673B (en) * 2013-11-22 2016-06-08 中国资源卫星应用中心 A kind of wide visual field linear CCD image geometric distortion analogy method
CN103776466B (en) * 2014-01-14 2016-05-04 中国空间技术研究院 Attitude adjustment to the imaging of non-homogeneous scene the same area and nonlinear calibration method
CN104537614B (en) * 2014-12-03 2021-08-27 中国资源卫星应用中心 CCD image orthorectification method for environment satellite I
CN104729535B (en) * 2015-03-17 2017-07-28 航天东方红卫星有限公司 A kind of in-orbit absolute calibration method of space camera based on fixed star
CN109544473B (en) * 2018-11-12 2020-12-29 中国资源卫星应用中心 Method, system and medium for calculating relative radiation correction coefficient of optical satellite
CN110006452B (en) * 2019-04-17 2023-06-23 武汉大学 Relative geometric calibration method and system for high-resolution six-size wide-view-field camera

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