CN107301316B - The off-axis remote sensing camera time of integration calculation method of push-broom type based on equivalent focal plane - Google Patents
The off-axis remote sensing camera time of integration calculation method of push-broom type based on equivalent focal plane Download PDFInfo
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Abstract
The present invention proposes a kind of off-axis remote sensing camera high-precision time of integration calculation method of the push-broom type based on equivalent focal plane, there are certain angles with substar horizontal plane for the focal plane of the off-axis remote sensing camera of push-broom type, this method is directed to the off-axis remote sensing camera of current push-broom type, there are off-axis angles with the optical axis for optical axis, in order to allow the optical axis that substar is imaged, camera needs pitching certain angle, causing focal plane with substar horizontal plane, there are certain angles, the time of integration calculates the problem of inaccuracy, by constructing the equivalent focal plane parallel with substar horizontal plane, establish strict geometrical relationship, find out the corresponding pixel dimension of real charge transfer time, to obtain the accurate time of integration, this method can effectively improve time of integration computational accuracy, effective means is provided for the in-orbit raising image quality of satellite.
Description
Technical field
The present invention relates to the off-axis remote sensing camera time of integration calculation methods of push-broom type based on equivalent focal plane, belong to satellite
In-orbit image quality technical field.
Background technique
Currently, the imaging performance of camera directly determines the whole of satellite with the rapid development of earth observation remote sensing satellite
Body performance and final image quality.Because inevitably there is central obscuration in axial symmetry reflective optics, central obscuration
In the presence of can not only lose luminous flux, but also reduce in system, the diffraction limit mtf value of low frequency.In order to solve axial symmetry reflection
Central obscuration problem existing for optical system, researcher propose off-axis reflection optical system, by increasing axial symmetry system
System aperture measures off axis, the off-axis field angle that increases axial symmetry reflecting system or both in conjunction with method avoid central obscuration.
Off axis reflector system eliminates central obscuration, but leads to reality by reasonably being tilted mirror surface and eccentric
There are certain angle (off-axis angles) for the border optical axis and optical axis, shown in the model of such satellite imagery such as Fig. 1 (b), the view of actual imaging
Axis farther out from substar, influences image quality；Current off-axis optics remote sensing satellite in order to allow as far as possible the optical axis to substar at
Picture, it will usually one angle of camera integral pitch be allowed to will lead to focal plane and substar horizontal plane at this time as shown in Fig. 1 (c)
There are certain angle, traditional time of integration calculation method will be due to the corresponding focal plane pixel dimension of practical charge transfer time
Variation and be unable to get the accurate time of integration.
Summary of the invention
Technology of the invention solves the problems, such as: overcome the deficiencies in the prior art, proposes a kind of pushing away based on equivalent focal plane
The off-axis remote sensing camera time of integration calculation method of formula is swept, time of integration computational accuracy is improved, accuracy of image motion compensation is improved, effectively mentions
High imaging quality.
The technical solution of the invention is as follows: the push-broom type off-axis remote sensing camera time of integration based on equivalent focal plane calculates
Method, there are certain angles with substar horizontal plane for the focal plane of the off-axis remote sensing camera of push-broom type, it is characterised in that including
The following steps:
(1), the extended line and camera of camera projection centre O and one terminal A of camera focal plane linear array center pel are defined
The intersection point of track horizontal plane be W, the line of another terminal B of camera projection centre O Yu camera focal plane linear array center pel and
The intersection point of track camera horizontal plane constructs equivalent focal plane center pel P using W and U as endpoint for UWU, calculate equivalent focal plane
Center pel size WU；The track camera horizontal plane be the central point T of camera focal plane linear array and with substar horizontal plane
Parallel plane；
(2), according to camera optical system focal length f and camera off-axis angle α, it is main away from f' to calculate the corresponding view of the camera optical axis；
(3), what the equivalent focal plane center pel size WU and step (2) being calculated according to step (1) were calculated
The corresponding view of the camera optical axis is main away from f', calculates camera integration time Tint:
In formula,It photographs the high ratio of spot speed for current time, wherein V current time photographs some ground velocity, and L takes the photograph for current time
Shadow point oblique distance.
The calculation formula of step (2) are as follows:
Step (1) calculates the specific steps of equivalent focal plane center pel size WU are as follows:
(1.1), the distance between W and T two o'clock WT is calculated:
In formula, d is the pixel dimension of camera focal plane, and η is the angle of camera optical axis and substar sight, the substar
Sight was the sight of projection centre Yu track horizontal plane；
(1.2), the distance between U and T two o'clock UT is calculated:
(1.3), the length of the pixel dimension WU in equivalent focal plane is calculated:
WU=WT+UT.
The speed is high than being obtained using the emulation of STK satellite simulation software modeling.
Compared with the prior art, the invention has the advantages that:
(1), the present invention proposes a kind of off-axis remote sensing camera time of integration calculation method of the push-broom type based on equivalent focal plane,
This method constructs the equivalent focal plane parallel with substar horizontal plane, by establishing strict geometrical relationship, finds out real electricity
Lotus transfer time corresponding pixel dimension, to obtain the more accurate time of integration.
(2), speed high ratio is calculated at the time of the difference of the invention according to locating for satellite, calculated result is more in line with practical feelings
Condition, precision are higher；
(3), simulation analysis show the present invention than in previous research directly using original pixel dimension and depending on leading away from acquiring
Time of integration precision can improve 1.2%.
Detailed description of the invention
Fig. 1 is different optical system imaging schematic diagrames；
Fig. 1 (a) is traditional no off-axis angle coaxial optical system imaging model；
Fig. 1 (b) is the optical system imaging model for having off-axis angle, focal plane parallel with substar horizontal plane；
Fig. 1 (c) is the optical system imaging model for having off-axis angle, focal plane and substar horizontal plane to form an angle；
The interior photography point of visual field and photography oblique distance schematic diagram when Fig. 2 is camera imaging；
Fig. 3 is that there are imaging geometry schematic diagrames when certain angle with substar horizontal plane for focal plane；
Fig. 4 is the pixel dimension and equivalent focal length geometrical relationship schematic diagram in equivalent focal plane；
Fig. 5 is the calculating comparing result for calculating the time of integration with conventional method using the present invention.
Specific embodiment
Below in conjunction with attached drawing, the present invention is described in detail with specific embodiment.
(1), without off-axis angle, the time of integration calculation method of substar imaging
Shown in traditional coaxial optical system imaging model such as Fig. 1 (a), camera integration time calculation formula is as follows:
In above formula: d is pixel dimension；
F is camera optical system focal length；
Photograph the high ratio of spot speed for current time, wherein V current time photograph some ground velocity, L be current time photography tiltedly
Away from.
As shown in Fig. 2, photography point ground velocity V is defined as movement velocity of the earth's surface photography point relative to camera focal plane center.
Photography point oblique distance L is the distance on photograph axis from Satellite Camera focal plane projection centre to photography point.As it can be seen that a certain
Imaging moment, the corresponding photography oblique distances of different photography points have differences in visual field when camera imaging.Speed Gao Bitong under normal conditions
The emulation of STK satellite simulation software modeling is crossed to obtain.Specific steps are as follows: use in STK satellite simulation software according to track (orbit)
Parameter, the visual field angular dimensions of satellite (satellite) parameter and camera (sensor), establish camera imaging model, simulation is appointed
Anticipate moment photography point ground velocity V and photography point oblique distance L, and the ratio of the two is the high ratio of speed at corresponding moment.
(2), there is off-axis angle, the optical axis is not to the time of integration calculation method of substar imaging
If it is off-axis camera, there are certain off-axis angles between the optical axis and optical axis, if do not considered under optical axis face star
The problem of point imaging, as shown in Fig. 1 (b), since focal plane is parallel, practical charge transfer time pair with substar horizontal plane
There is no variations for the pixel dimension answered, as long as being away from substitution with depending on main by the camera optical system focal length in formula (1) at this time
Can, time of integration calculation formula is as follows:
In formula, d is pixel dimension；
F' be the corresponding view of the camera optical axis lead away from；
Photograph the high ratio of spot speed for current time, wherein V current time photograph some ground velocity, L be current time photography tiltedly
Away from；
The corresponding view of the camera optical axis is main away from f' are as follows:
In formula, f is camera optical system focal length；
α is camera off-axis angle；
(3), the off-axis remote sensing camera time of integration calculation method of push-broom type based on equivalent focal plane
The off-axis remote sensing camera of push-broom type is the trend of Future Earth Observation moonlet development, in order to allow the optical axis to star as far as possible
Lower point imaging, in push-broom type off-axis remote sensing camera design at present, it will usually one angle of camera integral pitch is allowed, such as Fig. 1 (c) institute
Show, will lead to focal plane and substar horizontal plane at this time there are certain angle, the charge actual transfer time is corresponding apart from small
In original pixel dimension, the schematic diagram of focal plane and orbital plane is as shown in Figure 3 at this time.
It can be seen that according to geometrical light-path in this case and calculate the time of integration and need to find out satellite at this time and fly over ground
Time used in resolution ratio respective distances is only the real accurate time of integration.The present invention using optical axis, the optical axis and substar it
Between imaging geometry, calculate pixel dimension in equivalent focal plane by deriving, improve time of integration calculation formula.Specifically
Include the following steps:
(1), camera projection centre O and camera focal plane linear array center pel are defined (i.e. at camera focal plane linear array center
Pixel) extended line of terminal A and the intersection point of track camera horizontal plane be W, camera projection centre O and camera focal plane linear array
The line of another terminal B of center pel and the intersection point of track camera horizontal plane are U, using W and U as endpoint, are constructed equivalent burnt flat
Face center pel PWU, calculate equivalent focal plane center pel size WU；The track camera horizontal plane was camera focal plane line
The central point T of battle array and the plane parallel with substar horizontal plane, as shown in Figure 4.Photography point horizontal plane under equivalent focal plane and star
In parallel, photography point horizontal plane is parallel under the center pel with star of equivalent focal plane.
The specific calculating step of equivalent focal plane center pel size WU is discussed in detail below with reference to Fig. 4:
(1.1), θ is found out in triangle Δ AOT ' first1；Then in triangle Δ ATW, W is calculated according to sine
The distance between T two o'clock WT:
In formula, d is the pixel dimension of camera focal plane, and η is the angle of camera optical axis and substar sight, the substar
Sight was the sight of projection centre Yu track horizontal plane；
(1.2), θ similarly is found out in triangle BOT '5, U and T is then calculated according to sine in triangle BTU
The distance between two o'clock UT:
(1.3), the length of the pixel dimension WU in equivalent focal plane is calculated:
(2), according to camera optical system focal length f and camera off-axis angle α, it is main away from f' to calculate the corresponding view of the camera optical axis:
(3), what the equivalent focal plane center pel size WU and step (2) being calculated according to step (1) were calculated
The corresponding view of the camera optical axis is main away from f', calculates camera integration time Tint:
In formula,It photographs the high ratio of spot speed for current time, wherein V current time photographs some ground velocity, and L takes the photograph for current time
Shadow point oblique distance.The speed is high than being obtained using the emulation of STK satellite simulation software modeling.
Embodiment:
Method is determined for the push-broom type proposed by the invention based on the equivalent focal plane off-axis remote sensing camera time of integration
It is emulated, input is made the following assumptions in emulation:
Orbit altitude: h=645km
I=97.97 ° of orbit inclination angle
D=25 μm of pixel dimension of camera focal plane device TDICCD (Time Delayed and Integration)
Camera optical system focal length: f=543mm
Camera off-axis angle: α=9.4 °
Angle η=8.95 ° of camera optical axis and substar visual field
Satellite and camera model are established in satellite simulation software STK (Satellit Tool Kit), by southbound node 10:
30, the image center optical axis two neighboring moment (interval is obtained with the Pattern Intersection modular simulation in STK software
1s) with the position coordinates of earth surface intersection point (x, y, z) and oblique distance L, ground velocity calculates as follows:
Vx=dx/dt
Vy=dy/dt
Vz=dz/dt
Wherein, dt is data sampling interval, is set as 1s here.
According to the above simulated conditions, using time of integration calculation method proposed in this paper it can be concluded that camera imaging process
In, the time of integration range of center pel is 4.18-4.34ms, and comparison does not consider the time of integration of focal plane angle with horizontal plane
Range is 4.23-440ms, and computational accuracy improves 1.2%, and comparing result is as shown in Figure 5.
The off-axis camera integration time proposed in this paper based on equivalent focal plane is used it can be seen from the above comparative analysis
Calculation method can effectively improve time of integration computational accuracy, to improve as moving matching precision, improve in-orbit image quality.
The part that the present invention is not described in detail is the common knowledge of those skilled in the art.
Claims (4)
1. the off-axis remote sensing camera time of integration calculation method of push-broom type based on equivalent focal plane, the off-axis remote sensing phase of push-broom type
There are certain angles with substar horizontal plane for the focal plane of machine, it is characterised in that includes the following steps:
(1), the extended line and track camera of camera projection centre O and one terminal A of camera focal plane linear array center pel are defined
The intersection point of horizontal plane is W, the line and camera of another terminal B of camera projection centre O Yu camera focal plane linear array center pel
The intersection point of track horizontal plane constructs equivalent focal plane center pel P using W and U as endpoint for UWU, calculate equivalent focal plane center
Pixel dimension WU；The track camera horizontal plane was the central point T of camera focal plane linear array and parallel with substar horizontal plane
Plane；
(2), according to camera optical system focal length f and camera off-axis angle α, it is main away from f' to calculate the corresponding view of the camera optical axis；
(3), the camera that the equivalent focal plane center pel size WU and step (2) being calculated according to step (1) are calculated
The corresponding view of the optical axis is main away from f', calculates camera integration time Tint:
In formula,It photographs the high ratio of spot speed for current time, wherein V current time photograph some ground velocity, and L is current time photography point
Oblique distance.
2. the off-axis remote sensing camera time of integration calculation method of the push-broom type according to claim 1 based on equivalent focal plane,
It is characterized in that the calculation formula of step (2) are as follows:
3. the off-axis remote sensing camera time of integration calculation method of the push-broom type according to claim 1 based on equivalent focal plane,
It is characterized in that step (1) calculates the specific steps of equivalent focal plane center pel size WU are as follows:
(1.1), the distance between W and T two o'clock WT is calculated:
In formula, d is the pixel dimension of camera focal plane, and η is the angle of camera optical axis and substar sight, the substar sight
For the sight for crossing projection centre and track horizontal plane；
(1.2), the distance between U and T two o'clock UT is calculated:
(1.3), the length of the pixel dimension WU in equivalent focal plane is calculated:
WU=WT+UT.
4. the off-axis remote sensing camera time of integration calculation method of the push-broom type according to claim 1 based on equivalent focal plane,
It is characterized in that the speed is high than being obtained using the emulation of STK satellite simulation software modeling.
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