CN102096273B - Automatic exposure method of space camera based on target characteristics - Google Patents
Automatic exposure method of space camera based on target characteristics Download PDFInfo
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- CN102096273B CN102096273B CN201010622643.1A CN201010622643A CN102096273B CN 102096273 B CN102096273 B CN 102096273B CN 201010622643 A CN201010622643 A CN 201010622643A CN 102096273 B CN102096273 B CN 102096273B
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Abstract
The invention relates to an automatic exposure method of a space camera based on target characteristics, belonging to the technical field of aerospace optical remote sensors, in particular to an automatic exposure method applied in aerospace optical remote sensing CMOS (complementary metal oxide semiconductor) camera. The method provided by the invention comprises the following steps: carrying out noise-removing processing on image data generated by the camera, thus obtaining an image subjected to background noise removal so as to prepare for recognizing the target characteristics; then adopting a multilevel tree method to label the brightness information of a target in the image, thus obtaining the current brightness information of the target; and finally utilizing an exposure adjusting method to determine the exposure time of an image of the next frame of the space camera. According to the automatic exposure method of the space camera based on the target characteristics is adopted to recognize and extract the target information for carrying out automatic exposure adjustment, so that the adaptive ability of the camera when imaging is carried out in the space environment is improved.
Description
Technical field
The present invention relates to a kind of space camera automatic explosion method of based target characteristic, belong to spacer remote sensing device person in electronics.
Background technology
Small-sized low-power consumption face battle array CMOS camera has been widely used in satellite body mechanism, survey of deep space, space station and spaceborne video remote measurement; There have been activities such as it just can be opened Satellite Orbit Maneuver, change attitude, engine operation, the sun span, antenna expansion to keep watch on and assess; Judge on ground that for researcher the satellite working condition provides the image foundation, be successfully applied to a plurality of models.
When camera is worked at rail; Whether the time shutter is suitable extremely important, and too short meeting of time shutter causes scenery very dark, and the long scenery luminance saturation that can cause; Therefore the time shutter adjusting is essential; But the time shutter is regulated very complicated, regulates badly may be absorbed in the time shutter disorder dark situation when bright when occurring.Whether what therefore the time shutter was regulated is suitable, is vital to camera imaging, is related to the success or failure of task.
Present civilian digital camera is at the technical comparative maturity of automatic exposure, can set needed different exposure modes according to night scene, daytime, portrait etc., and effect is fine, if but be applied to space flight and just its limitation arranged.When camera is taken target object in the sky; Because the application characteristic of CMOS camera; Can't accurately foresee in advance shot object position, brightness, account for information such as image area size, and the scenery of many times mutually confidential shooting all can't reappear again, for once; Open such as the sun span; If pass image back and confirm again behind the ground to select what exposure mode and time shutter, missed right moment for camera, so confirm that in real time time shutter and exposure mode are the outstanding features that camera space is distinguished civilian camera.
At present; The method of space optical remote camera adjustments exposure is also few; Large-scale remote sensing of the earth camera is because the determinacy of its terrain object; Can use spoke Luminance Analysis software, camera optics and sensor chip characteristic to draw the accurate time shutter, only need to switch according to several grades of time shutter of different set of ground scenery.The stepping exposure method can not solve the needs of CMOS camera to the real-time automatic exposure of scenery equally, can reduce the one-tenth scape rate of camera, and a few width of cloth images possibly have only one can use.
The domestic automatic explosion method that is applied to space flight CMOS camera at present can't be discerned effective target owing to camera; When in the visual field during scenery relative complex; Can't distinguish exposure; It is big disturbed by noise and non-effective target, makes that object scene brightness is difficult in the suitable scope in the image, has increased the automatic exposure difficulty.
Summary of the invention
Technology of the present invention is dealt with problems and is: overcome the deficiency of prior art, a kind of automatic explosion method of space camera of based target characteristic is provided, this method is obtained target information through recognition objective; To the target adjusting that makes public; Shielded other factors interference such as background, it is with strong points that the time shutter is regulated, thereby improved the one-tenth scape rate and the adaptive faculty of camera image; Utilize the instantaneous exposure control method at last, realized the space camera automatic exposure of based target characteristic.
Technical solution of the present invention is:
A kind of space camera automatic explosion method of based target characteristic, step is following:
(1) the present image subtracting background noise image that space camera was obtained according to the initial exposure time, the image after the noise is removed in formation, gets into step (2) afterwards;
(2) generate the multistage tree of removing the image after the noise described in the step (1), get into step (3) afterwards; The method that generates the multistage tree of removing the image after the noise described in the step (1) is following:
Corresponding four node of the number of plies n of said multistage tree >=4 and each node; The said image that removes after the noise is divided into some image blocks; The quantity of image block equals the number of multistage tree bottom node, and multistage tree bottom node is corresponding one by one with image block;
Pass through formula
Calculate the value V of bottom node
L, m is the ground unrest maximal value, is preset value;
Pass through formula
Calculate the value V of non-bottom node in the multistage tree
i
(3) according to the value of the multistage tree bottom node that obtains in the step (2) and the value of non-bottom node, through formula
L
i＝V
n-1×2
n-1+V
n-2×2
n-2+…+V
2×2
2+V
1×2
1+V
0×2
0
Calculate the weights Li of the corresponding image block of each multistage tree bottom node; Wherein, V
0Be multistage tree bottom node, the i.e. value of first order node; V
1Be the even higher level of node of above-mentioned bottom node, i.e. the value of second level node; V
2Be the last two-stage node of above-mentioned bottom node, the i.e. value of third level node; In like manner, V
N-1Be the last n-1 level node of above-mentioned bottom node, the i.e. value of n level node;
(4) according to the weights Li of each image block that obtains in the step (3), through formula:
Calculate the pixel average E of weights greater than 8 all images piece; Wherein, M is weights greater than 8 image block number;
N * N is the size of image block, and promptly the length of image block and wide is N pixel; v
(x, y)Be the pixel value of weights greater than pixel in 8 the image block;
(5) weights that draw according to step (4) are greater than the pixel average E of 8 all images piece, through formula:
Calculate the next frame time shutter N_INI of space camera, wherein, C_INI is the current time shutter of space camera, and max_INI is the maximal value of space camera time shutter.
The present invention's beneficial effect compared with prior art is:
(1) the present invention can effectively improve the automatic exposure performance under the situation of comparing the speed of not influencing with existing method, has improved the imaging capability and the picture quality of camera.The present invention mainly is used on the CMOS camera of small-sized low-power consumption space; This camera has characteristics such as small-sized low-power consumption, and to take resource few, and require to have the fast imaging ability, and this just needs the automatic exposure adjusting time short; The multistage tree method that the present invention adopts can identify object scene fast and effectively; And extract its monochrome information, and with strong points, improved the performance of automatic exposure.
(2) the present invention utilizes multistage tree construction that image-region is marked, and has reduced the complexity to image statistics, has improved the identification probability of effective target, has shielded the interference of invalid target image.More existing automatic explosion methods; Can't distinguish the effective target in the visual field; Adopt and directly all pixels in the entire image are averaged or simple threshold value screening, when the scenery difference in brightness is big in the visual field, object scene will occurs and cross bright or dark excessively situation like this; And adopted multistage tree construction; Can carry out multilevel hierarchy to the scenery of different brightness in the visual field handles; Can when taking into account other scenery, focus on effective target is carried out automatic exposure, can obtain more suitably time shutter and better pictures thereby compare additive method.
(3) the present invention adopts the monochrome information of multistage tree construction memory image, has improved automatic exposure speed to a great extent, compares existing exposure method and has significantly improved one-tenth scape rate.Existing exposure method is not preserved the monochrome information of piece image, and whether the back piece image down of exposure is compared piece image suitable, and whether effective target brightness is suitable, does not form feedback relationship, therefore also just can't form quick convergent trend; And adopt multistage tree construction only to need the little hardware resource just can preserve image luminance information; Thereby whether suitable reference is provided for what next width of cloth image exposuring time was regulated; Improved the speed of automatic exposure greatly, for assurance being provided in the real-time automatic exposure of rail.
(4) the present invention has greatly improved video remote measurement image of camera adaptive capacity to environment; Because the supervision of CMOS camera might be the satellite movable device to picture; Such as sun wing windsurfing, before the sun span is opened with launch shape, size and the brightness of back in the space camera visual field very big difference all arranged, the present invention can both can be to the sun wing blur-free imaging before having launched through multistage tree method; Can lock the sun wing after the expansion again very soon; And confirm the suitable time shutter, for space mechanisms such as satellite in orbit situation keep watch on important leverage be provided, for researcher provides visual information directly perceived clearly to the understanding and the improvement of satellite transit situation.
Description of drawings
Fig. 1 is a space camera automatic exposure schematic flow sheet of the present invention;
Fig. 2 is the multistage tree construction synoptic diagram of the present invention;
Fig. 3 divides synoptic diagram for the multistage tree of the present invention.
Embodiment
Further describe in detail below in conjunction with the accompanying drawing specific embodiments of the invention:
Small-sized low-power consumption face battle array CMOS camera has been widely used in satellite body mechanism, survey of deep space, space station and spaceborne video remote measurement; Had it just can Satellite Orbit Maneuver, change activities such as attitude, engine operation, the sun span are opened, antenna expansion and keep watch on and assess; Judge on ground that for researcher the satellite working condition provides the image foundation, be successfully applied to a plurality of models.
When camera is worked at rail; Whether the time shutter is suitable extremely important, and too short meeting of time shutter causes scenery very dark, and the long scenery luminance saturation that can cause; Therefore the time shutter adjusting is essential; But the time shutter is regulated very complicated, regulates badly may be absorbed in the time shutter disorder dark situation when bright when occurring.Whether what therefore the time shutter was regulated is suitable, is vital to camera imaging, is related to the success or failure of task.
Present civilian digital camera is technical very ripe in automatic exposure; Can set needed different exposure modes according to night scene, daytime, portrait etc.; If but when being applied to the CMOS camera; Can't accurately foresee in advance shot object position, brightness, account for information such as image area size, can not select exposure mode and time shutter in real time, cause missing right moment for camera.
The domestic automatic explosion method that is applied to space flight CMOS camera at present; Though can accomplish in real time, owing to camera can't be discerned target, when the background complicacy; When there is action in space mechanism in the visual field; Can't distinguish exposure, receive noise and background interference big, make that scenery brightness is difficult in the suitable scope in the image.
Be illustrated in figure 1 as the process flow diagram of the space camera automatic explosion method that the present invention is based on target property, said automatic exposure is meant through the methods analyst image obtains effective information, and then calculates down the time shutter of piece image automatically.Comprise noise remove, generate multistage tree, calculate each multistage tree bottom node correspondence image piece weights, computed image piece pixel average and calculate this several steps of next frame time shutter.Noise remove mainly be to the long noise that causes of the intrinsic dark current noise in the image, time shutter and dark a little less than non-imageable target remove; Obtain not having the image of noise; To reduce influence to multistage tree construction; Be about to the present image subtracting background noise image that space camera obtained according to the initial exposure time, the image after the noise is removed in formation.The initial exposure time is preset value.According to formula
DN(j，k)＝p(j，k)-n(j，k)
View data behind the calculating denoising, the pixel value of space camera present image is p, and the ground unrest image pixel value is n, is the prevision value, and image pixel value is DN after the denoising;
Generate to remove the multistage tree of image behind the noise, said multistage tree construction can the statistical picture Luminance Distribution, can find the continuous scenery that occupies certain pixel number in the image easily through it, and can play the effect of isolating the invalid scenery that accounts for small number of pixels; Corresponding four node of the number of plies n of said multistage tree >=4 and each node; The said image that removes after the noise is divided into the identical image block of some sizes; The quantity of image block equals the number of multistage tree bottom node, and multistage tree bottom node is corresponding one by one with image block, the corresponding image block of the bottom node of each multistage tree construction; Get its size and be N * N, the promptly long and wide image block that is N pixel;
The size that at first accounts for image according to object scene is confirmed the image block size of multistage tree bottom node representative; Probably account for 512 * 512 pixels such as effective target; The image that its downstream site is corresponding is 256 * 256; But for fear of the effective target of failing to judge, generally down divide the bottom node of one-level as multistage tree again, the image block size of promptly multistage tree bottom node representative is 128 * 128.Multistage tree synoptic diagram is as shown in Figure 2, and division methods is as shown in Figure 3.
Accomplish multistage tree and divide the back according to formula
Calculate the value V of bottom node
L, m is the ground unrest maximal value, is preset value;
Pass through formula
Calculate the value V of non-bottom node in the multistage tree
i
Value V according to bottom node
LValue V with non-bottom node
i, through formula
L
i＝V
n-1×2
n-1+V
n-2×2
n-2+…+V
2×2
2+V
1×2
1+V
0×2
0
Calculate the weights Li of the corresponding image block of each multistage tree bottom node; Wherein, V
0Be multistage tree bottom node, the i.e. value of first order node; V
1Be the even higher level of node of above-mentioned bottom node, i.e. the value of second level node; V
2Be the last two-stage node of above-mentioned bottom node, the i.e. value of third level node; In like manner, V
N-1Be the last n-1 level node of above-mentioned bottom node, the i.e. value of the value of n level node; For example the value of a bottom node is 1, and its upper layer node value is 1, and the upper layer node value is 1 again, and the weights Li of the image block that then this multistage tree bottom node is corresponding is 7;
According to the weights Li of each image block that obtains, through formula:
Calculate the pixel average E of weights greater than 8 all images piece; Wherein, M is weights greater than 8 image block number;
N * N is the size of image block, and promptly the length of image block and wide is N pixel; v
(x, y)Be the pixel value of weights greater than pixel in 8 the image block; For example weights have 4 greater than 8 branch, and its correspondence image piece average is C
1=100, C
2=120, C
3=130, C
4=150, then the average gray value E of effective target is:
Get into the exposure adjusting stage at last, according to effective target average gray value E, through formula:
Calculate the next frame time shutter N_INI of space camera, wherein, C_INI is the current time shutter of space camera, and max_INI is the maximal value of space camera time shutter, is preset value.
The present invention has been successfully applied to CMOS camera of hope, certain model lunar exploration satellite monitoring camera.Hope that the clear China's first that photographed of CMOS camera opens earth panorama photochrome; Certain model lunar exploration satellite monitoring camera has been passed a plurality of videos such as sun span open procedure, directional antenna rotation, 490N engine braking back, and has arrived the beautiful earth and the moon in the lunar trajectory photographs.Following this camera also will be widely used in satellization authority, survey of deep space, space station and extravehicular activity of astronaut are carried out to picture, obtain a large amount of valuable video telemetry intelligence (TELINT)s.
The content of not doing to describe in detail in the instructions of the present invention belongs to those skilled in the art's known technology.
Claims (1)
1. the space camera automatic explosion method of a based target characteristic is characterized in that step is following:
(1) the present image subtracting background noise image that space camera was obtained according to the initial exposure time, the image after the noise is removed in formation, gets into step (2) afterwards;
(2) generate the multistage tree of removing the image after the noise described in the step (1), get into step (3) afterwards; The method that generates the multistage tree of removing the image after the noise described in the step (1) is following:
Corresponding four node of the number of plies n of said multistage tree >=4 and each node; The said image that removes after the noise is divided into some image blocks; The quantity of image block equals the number of multistage tree bottom node, and multistage tree bottom node is corresponding one by one with image block;
Pass through formula
Calculate the value V of bottom node
0, m is the ground unrest maximal value, is preset value;
Pass through formula
Calculate the value V of non-bottom node in the multistage tree
i
(3) according to the value of the multistage tree bottom node that obtains in the step (2) and the value of non-bottom node, through formula
L
i=V
N-1* 2
N-1+ V
N-2* 2
N-2++ V
2* 2
2+ V
1* 2
1+ V
0* 2
0Calculate the weights L of the corresponding image block of each multistage tree bottom node
iWherein, V
0Be multistage tree bottom node, the i.e. value of first order node; V
1Be the even higher level of node of above-mentioned bottom node, i.e. the value of second level node; V
2Be the last two-stage node of above-mentioned bottom node, the i.e. value of third level node; In like manner, V
N-1Be the last n-1 level node of above-mentioned bottom node, the i.e. value of n level node;
(4) according to the weights Li of each image block that obtains in the step (3), through formula:
Calculate the pixel average E of weights greater than 8 all images piece; Wherein, M is weights greater than 8 image block number;
N * N is the size of image block, and promptly the length of image block and wide is N pixel; v
(x, y)Be the pixel value of weights greater than pixel in 8 the image block;
(5) weights that draw according to step (4) are greater than the pixel average E of 8 all images piece,
Pass through formula:
Calculate the next frame time shutter N_INI of space camera, wherein, C_INI is the current time shutter of space camera, and max_INI is the maximal value of space camera time shutter.
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| US9189451B1 (en) | 2011-10-06 | 2015-11-17 | RKF Engineering Solutions, LLC | Detecting orbital debris |
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| CN104184958B (en) * | 2014-09-17 | 2017-07-11 | 中国科学院光电技术研究所 | Automatic exposure control method and device based on FPGA (field programmable Gate array) and suitable for space detection imaging |
| CN104917975B (en) * | 2015-06-01 | 2018-01-05 | 北京空间机电研究所 | A kind of adaptive automatic explosion method based on target signature |
| CN105430293B (en) * | 2015-12-03 | 2018-05-22 | 哈尔滨工业大学 | The in-orbit dynamic scene real-time matching method of Optical remote satellite |
| CN109740393A (en) * | 2018-12-06 | 2019-05-10 | 无锡盈达聚力科技有限公司 | Bar code scanning system and method |
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| 李威等.胶片型空间相机的快门设计和研究.《光学精密工程》.2005,第13卷9-14. * |
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