CN106559665B - A kind of off-axis camera integration time determines method - Google Patents
A kind of off-axis camera integration time determines method Download PDFInfo
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- CN106559665B CN106559665B CN201610917848.XA CN201610917848A CN106559665B CN 106559665 B CN106559665 B CN 106559665B CN 201610917848 A CN201610917848 A CN 201610917848A CN 106559665 B CN106559665 B CN 106559665B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N17/00—Diagnosis, testing or measuring for television systems or their details
- H04N17/002—Diagnosis, testing or measuring for television systems or their details for television cameras
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/50—Control of the SSIS exposure
- H04N25/53—Control of the integration time
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Abstract
A kind of off-axis camera integration time determines method, off-axis camera integration time is calculated for conventional method and the problem of deviation be present, using kinematical theory and solid geometry method, ground vector is calculated by satellite orbit, posture, imaging point parameter, build ground velocity, as speed, optical axis vector triangle, solve vector triangle to calculate as the size of speed and as fast vector, accurate off-axis camera integration time is calculated using parameters such as camera pixel dimension, focal length, photography point oblique distances.The inventive method is succinctly efficient, accurate reasonable；Avoid the deviation that traditional coordinate transformation method may be brought, by the accurate analysis to related physical magnitude relation, the time of integration of off-axis camera is accurately calculated, improves the accuracy of CCD time of integration result of calculations, improve satellite imagery quality, precision is higher in engineer applied；It can also further derive the computational methods of off-axis camera drift angle；And same camera shaft is equally applicable to, adaptability is wider.
Description
Technical field
The present invention relates to a kind of off-axis camera integration time to determine method, more particularly to a kind of to can be used for camera optical axis with regarding
The misaligned TDICCD camera integration time computational methods of axle.
Background technology
The time of integration is the important indicator of TDICCD push-broom types optical remote sensing camera on star, is related to that remote sensing satellite is imaged matter
The quality of amount, the time of integration needed for camera imaging on real-time star is accurately calculated, be the remote sensing of the earth image for obtaining high quality
One of important prerequisite.
Because camera is imaged using TDICCD devices, time of integration of camera needs to be adjusted according to satellite orbit.Root
According to TDICCD image-forming principles, the preferable time of integration is the time that atural object imaging on focal plane moves a line needs.When full
During sufficient true integral time conditions, as translational speed it is identical with TDICCD electric charge transfer speed.If the time of integration mismatches,
Motion-blurred will be caused, ssystem transfer function (MTF) declines.
Off-axis camera refers to the optical axis and the misaligned camera of optical axis.When analyzing camera integration time, important parameter is meter
The high ratio of speed is calculated, speed here refers to component of the ground velocity in CCD faces.There is the method using Coordinate Conversion in pertinent literature, by ground velocity
It is transformed into so that in the CCD planes of camera body system description, such a method has no problem for the camera of the optical axis and optical axis coincidence, but
It is for the misaligned camera of the optical axis and optical axis, then in the presence of certain deviation.This deviation when off-axis angle is smaller difference compared with
It is small, do not influence engineering use typically；When off-axis angle is larger, or when requirement of engineering precision is higher, then need with accurate
Algorithm eliminates the influence of the deviation.
The content of the invention
The technology of the present invention solves problem：Deviation be present to the calculating of off-axis camera integration time for conventional method to ask
Topic, propose that a kind of off-axis camera integration time determines method, this method can effectively solve increasing in current engineering design
Off-axis camera integration time calculates problem, improves the accuracy and precision of time of integration result of calculation.
The technical scheme is that：A kind of off-axis camera integration time determines method, comprises the following steps：
(1) according to kinematic principle Computed Ground Speed vector vGround=-ωe×R+(vs+ωb×H)；Wherein ωeIt is earth angle speed
Vector is spent, R is vector of the earth's core to imaging point, vsIt is satellite velocity vector, ωbIt is the angular speed that satellite body coordinate system has
Vector, H are distance vector of the satellite to imaging point；
(2) vector triangle of relevant speed vector composition is built, and judges projection components of the ground velocity on boresight direction
Direction；
Form vector triangle three vectors be respectively：Ground velocity vGround, as fast vccd, component v of the ground velocity on the optical axisThe optical axis；
If ground vector vGroundBelow CCD planes, then vThe optical axisDirection is downward, i.e., points to imaging point from satellite；If ground vector vGroundIn CCD
It is more than plane, then vThe optical axisDirection is upward, i.e., points to satellite from imaging point；
(3) it is calculated as fast vccdUnit vector nccd, i.e., the direction as speed in CCD planes；
Wherein obtain vGroundUnit vector nGround, the unit vector n of optical axisOptical axis,
(4) calculate as the size of speed and as fast vector；
N is calculated respectivelyThe optical axis、nGround、nccdAngle α between three vectorsThe optical axis-ground、αThe optical axis-ccd,
αThe optical axis-ground=cos-1(nThe optical axis·nGround), αThe optical axis-ccd=cos-1(nThe optical axis·nccd)
If αThe optical axis-ground<αThe optical axis-ccd, show ground vector below CCD planes, then αThe optical axis-ccdTake its supplementary angle；
If αThe optical axis-ground>αThe optical axis-ccd, show ground vector more than CCD planes, αThe optical axis-groundTake its supplementary angle；
Vector triangle is solved, by sine：There is vccd=| vccd|·nccd；
(5) time of integration is obtained according to as fast vector and relevant parameterWherein vccdxFor vector vccdAlong CCD
Piece pushes away the component for sweeping direction, and h is size of the CCD pieces to photography point oblique distance, and f is the focal length of camera, and d is the CCD pixel chis of camera
It is very little.
Compared with the prior art, the invention has the advantages that：
(1) the inventive method uses kinematical theory and solid geometry method, and the succinct calculation formula efficiently, derived is accurate
Really rationally；
(2) inventive process avoids the deviation that traditional coordinate transformation method may be brought, by related physical quantity
The accurate analysis of relation, the time of integration of off-axis camera can be accurately calculated, improve the accurate of CCD time of integration result of calculations
Property and precision, improve satellite imagery quality, precision is higher in engineer applied；
(3) the inventive method can also further derive the computational methods of off-axis camera drift angle；
(4) the inventive method is equally applicable to same camera shaft, and adaptability is wider.
Brief description of the drawings
Fig. 1 is the inventive method flow chart；
Fig. 2 is that off-axis camera integration time calculates dependent vector schematic diagram；
Fig. 3 is that off-axis camera integration time calculates vector triangle schematic diagram (ground vector is below CCD planes)；
Fig. 4 is that off-axis camera integration time calculates vector triangle schematic diagram (ground vector is more than CCD planes)；
Fig. 5 is as fast direction calculating schematic diagram.
Embodiment
(1) according to kinematic principle Computed Ground Speed vector；
The velocity of following is subtracted equal to absolute velocity according to relative velocity, for ordinary circumstance, imaging point is relative to satellite
Speed, it can be calculated with following formula：
vGround=ωe×R-(vs+ωb×H) (1)
Wherein ωeIt is earth rate vector, R is vector of the earth's core to imaging point, vsIt is satellite velocity vector, ωbIt is to defend
The angular velocity vector that star body coordinate system has, H are distance vector of the satellite to imaging point.
Define ground velocity be satellite with respect to the speed of imaging point, have
vGround=-ωe×R+(vs+ωb×H) (2)
(2) vector triangle of several relevant speed vector compositions is built, and judges projection of the ground velocity on boresight direction
Component direction；
Form vector triangle three vectors be respectively：Ground velocity vGround(having been obtained in previous step), as fast vccd(
Fast vGroundThere is component in CCD planes, size, direction wait to ask), ground velocity is on the optical axis (satellite points to the vector of imaging point)
Component vThe optical axis(size is waited to ask, direction along the optical axis or its opposite direction).
If ground vector vGroundBelow CCD planes (Fig. 2), then vThe optical axis(point to imaging point from satellite) downwards in direction；Instead
It, if ground vector vGroundMore than CCD planes (Fig. 3), then vThe optical axis(point to satellite from imaging point) upwards in direction.
(3) it is calculated as fast vccdUnit vector nccd, i.e., the direction as speed in CCD planes；
Obtain vGroundUnit vector nGround, nGroundFor the unit vector in ground vector direction, nccdIt is ground velocity in CCD planes
Projection.See Fig. 4.
Obtain the unit vector n of optical axisOptical axis, nOptical axisPerpendicular to the normal of CCD planes, as CCD planes, intermediate quantity n is calculated1
=nOptical axis×nGround
By n1Normalization, n1For the unit vector in CCD planes
Due to nccdFor projection of the ground velocity in CCD planes, therefore nOptical axis、nGround、nccdIt is coplanar, both perpendicular to n1, so having
(4) it is calculated as the size of speed and as fast vector；
N is calculated respectivelyThe optical axis、nGround、nccdAngle α between three vectorsThe optical axis-ground、αThe optical axis-ccd,
αThe optical axis-ground=cos-1(nThe optical axis·nGround) (4)
αThe optical axis-ccd=cos-1(nThe optical axis·nccd) (5)
Judge：
If a) αThe optical axis-ground<αThe optical axis-ccd, illustrate ground vector (Fig. 2), α below CCD planesThe optical axis-ccdTake its supplementary angle；
If b) αThe optical axis-ground>αThe optical axis-ccd, illustrate ground vector (Fig. 3), α more than CCD planesThe optical axis-groundTake its supplementary angle；
Vector triangle is solved, by sine：
Have
vccd=| vccd|·nccd (7)
(5) time of integration is calculated according to as fast vector and relevant parameter.
The high ratio of speed is calculated first.Obtain vector vccdThe component v for sweeping direction is pushed away along CCD piecesccdx, CCD pieces to photography point oblique distance
H size, can calculate fast height is than B, specific formula for calculation：
Then the time of integration, its calculation formula according to corresponding to the focal length of fast high ratio and camera, pixel dimension calculate CCD
For：
Wherein f be camera focal length, d be camera CCD pixel dimensions, vxThe component for sweeping direction is pushed away in CCD pieces for picture speed.
The content not being described in detail in description of the invention belongs to the known technology of professional and technical personnel in the field.
Claims (1)
1. a kind of off-axis camera integration time determines method, it is characterised in that comprises the following steps：
(1) according to kinematic principle Computed Ground Speed vector vGround=-ωe×R+(vs+ωb×H)；Wherein ωeIt is earth rate arrow
Amount, R are vector of the earth's core to imaging point, vsIt is satellite velocity vector, ωbIt is the angular velocity vector that satellite body coordinate system has,
H is distance vector of the satellite to imaging point；
(2) vector triangle of relevant speed vector composition is built, and judges projection components direction of the ground velocity on boresight direction；
Form vector triangle three vectors be respectively：Ground velocity vGround, as fast vccd, component v of the ground velocity on the optical axisThe optical axis；If ground
Fast vector vGroundBelow CCD planes, then vThe optical axisDirection is downward, i.e., points to imaging point from satellite；If ground vector vGroundIn CCD planes
More than, then vThe optical axisDirection is upward, i.e., points to satellite from imaging point；
(3) it is calculated as fast vccdUnit vector nccd, i.e., the direction as speed in CCD planes；
Wherein obtain vGroundUnit vector nGround, the unit vector n of optical axisOptical axis；
(4) calculate as the size of speed and as fast vector；
N is calculated respectivelyThe optical axis、nGround、nccdAngle α between three vectorsThe optical axis-ground、αThe optical axis-ccd, wherein nThe optical axisFor the unit vector of the optical axis；
αThe optical axis-ground=cos-1(nThe optical axis·nGround), αThe optical axis-ccd=cos-1(nThe optical axis·nccd)
If αThe optical axis-ground<αThe optical axis-ccd, show ground vector below CCD planes, then αThe optical axis-ccdTake its supplementary angle；
If αThe optical axis-ground>αThe optical axis-ccd, show ground vector more than CCD planes, αThe optical axis-groundTake its supplementary angle；
Vector triangle is solved, by sine：There is vccd=| vccd|·nccd；
(5) time of integration is obtained according to as fast vector and relevant parameterWherein vccdxFor vector vccdPushed away along CCD pieces
The component in direction is swept, h is size of the CCD pieces to photography point oblique distance, and f is the focal length of camera, and d is the CCD pixel dimensions of camera.
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| CN107301316B (en) * | 2017-06-01 | 2019-09-06 | 航天东方红卫星有限公司 | The off-axis remote sensing camera time of integration calculation method of push-broom type based on equivalent focal plane |
| CN107702697B (en) * | 2017-09-27 | 2019-11-29 | 中国科学院长春光学精密机械与物理研究所 | The line frequency calculation method of the vertical rail rotation sweeping imaging of TDI camera |
| CN109672880B (en) * | 2018-12-29 | 2020-02-14 | 中国科学院长春光学精密机械与物理研究所 | Grouping drift angle real-time adjusting method of wide-width space camera |
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| CN103913148A (en) * | 2014-03-26 | 2014-07-09 | 中国科学院长春光学精密机械与物理研究所 | Full-link numerical simulation method of aerospace TDICCD (Time Delay and Integration Charge Coupled Device) camera |
| CN104581144A (en) * | 2015-01-16 | 2015-04-29 | 航天东方红卫星有限公司 | Full-field integral time determining method for satellite-borne linear array push broom camera |
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