CN103604420A - Method for compensating two-dimensional image motion by using rotation of secondary mirror of foldback system - Google Patents

Abstract

The invention relates to a method for compensating a two-dimensional image motion by using rotation of a secondary mirror of a foldback system. The method comprises the steps: 1, when a camera performs aviation photographing, respectively obtaining a forward image motion amount and a whiskbroom motion amount; 2, calculating an angle, needing to rotate around an X axis, of the secondary mirror in the optical system according to the forward image motion amount and a parameter of the optical system, and calculating an angle, needing to rotate around a Y axis, of the secondary mirror in the optical system according to the whiskbroom motion amount and the parameter of the optical system, wherein the X axis is a horizontal direction vertical to a plane of an optical axis of the optical system, and the Y axis is a vertical direction of a plane of the optical axis of the optical system; and 3, carrying out rotation control on the secondary mirror in the optical system according to the angles, needing to rotate around the X axis and the Y axis, of the secondary mirror and compensating the image motion. The invention provides a method for compensating the two-dimensional image motion by using the rotation of the secondary mirror of the foldback system, which is capable of enabling an aviation camera to meet high resolution and large width and simultaneously obtaining a clear image.

Description

The method of two-dimentional IMC is carried out in turn back system secondary mirror rotation of utilization

Technical field

The invention belongs to Optical System Design and applied technical field, relate to a kind of IMC method, relate in particular to turn back system secondary mirror rotation of a kind of utilization and carry out the method for two-dimentional IMC.

Background technology

Along with the development of air photo technique, more and more higher to the requirement of aerial photographic camera, require aerial photographic camera to have under flying speed faster, obtain the ability of large format picture rich in detail.When aerial camera is taken pictures in the air, due to the motion of target with respect to camera, image is also mobile in detector image planes, therefore can produce picture and move.Picture moves target imaging on detector is thickened, and when the picture amount of moving surpasses to a certain degree, can not obtain high-resolution image.Cause that the principal element that camera looks like to move has the attitude variation of flying speed, flying height, system focal length, flying platform, the vibration of aircraft etc.Conventionally, the single image width that camera is taken is subject to the restriction of the factors such as optical system focal length and detector size, field angle, relation between focal length and target surface as shown in Equation (1), in order to obtain high-resolution image, require the focal length of optical system to want long enough, in the situation that detector size is certain, the single image width that camera is taken can reduce, in order to obtain the image of large format width, conventionally the way of taking is in aircraft flight, camera is carried out to sweeping, now, camera is except the forward direction being caused by aircraft flight looks like to move, also exist sweeping to look like to move.

$2\mathrm{\θ}=\arctan \frac{y}{2f}---\left(1\right)$

In formula: θ is system level angle of half field-of view; Y is detector horizontal width; F is optical system focal length.

Forward direction looks like to move and scans picture and moves and all belong to motor image and move, and it is main relevant with the high ratio of speed, focal length and time shutter that forward direction looks like to move size, and its relation is determined by following formula:

Wherein: S _{forward direction}that forward direction looks like the amount of moving; T _exposureit is the time shutter; υ is flying speed; F ' is optical lens focal length; H is flying height.

The size that scanning picture moves is relevant with camera sweeping speed, system focal length and time shutter, and its relation as shown in Equation (3).

S _scanning=f ' tan (ω T _exposure) (3)

Wherein: S _scanningit is the scanning picture amount of moving; F ' is optical lens focal length; ω is sweeping angular velocity; T _exposureit is the time shutter.

Total picture that comprehensive forward direction looks like to move and motor image moves moves effect as shown in Figure 1, in figure, forward direction looks like to move length that vector sweeping looks like to move vector and depends on that forward direction looks like the size that the amount of moving and sweeping look like the amount of moving, when total picture amount of moving surpasses respective threshold, image blur degree, by degradation, cannot obtain satisfied image.

Optics two dimension IMC need to be controlled at optical system front end or rear end increase plane mirror conventionally, making it carry out Two Dimensional Rotating compensates forward direction and looks like to move with sweeping and look like to move, the drawback that adds plane mirror in optical system front portion is that catoptron is excessive, control power and the corresponding increase of size that motor needs, cause entire system size and weight significantly to increase.System rear end increases catoptron needs rear cut-off distance longer conventionally, and Optical System Design difficulty is increased, and above-mentioned two kinds of methods all need to increase optical element and realize in the optical system designing.

Goal of the invention

In order to solve the above-mentioned technical matters existing in background technology, the invention provides and a kind ofly make aerial camera meet utilization that high-resolution and large format width the obtain picture rich in detail simultaneously system secondary mirror rotation of turning back to carry out the method for two-dimentional IMC.

Technical solution of the present invention is: the invention provides turn back system secondary mirror rotation of a kind of utilization and carry out the method for two-dimentional IMC, its special character is: the described utilization method that the rotation of system secondary mirror carries out two-dimentional IMC of turning back comprises the following steps:

1), when camera carries out aviation and takes pictures, obtain respectively that forward direction looks like the amount of moving and sweeping looks like the amount of moving;

2) according to the resulting forward direction of step 1), look like the angle that in the calculation of parameter optical system of the amount of moving and optical system, secondary mirror need to rotate around X-axis;

And, according to the resulting sweeping of step 1), look like the angle that in the calculation of parameter optical system of the amount of moving and optical system, secondary mirror need to rotate around Y-axis;

Described X-axis is perpendicular to the horizontal direction of the plane of system optical axis; Described Y-axis is perpendicular to the vertical direction of the plane of system optical axis;

3) according to step 2) angle that need to rotate around X-axis and Y-axis of resulting secondary mirror be rotated control to the secondary mirror in optical system, and retrieved image moves.

Above-mentioned steps 1) obtain manner that in, forward direction looks like the amount of moving is:

Wherein:

S _{forward direction}that forward direction looks like the amount of moving;

T _exposureit is the time shutter;

U is flying speed;

F ' is optical lens focal length;

H is flying height.

Above-mentioned steps 1) obtain manner that in, sweeping looks like the amount of moving is:

S _scanning=f ' tan (ω T _exposure)

Wherein:

S _scanningit is the scanning picture amount of moving;

F ' is optical lens focal length;

ω is sweeping angular velocity;

T _exposureit is the time shutter.

The specific implementation of the angle that above-mentioned steps 2) in calculating optical system, secondary mirror need to rotate around X-axis and Y-axis is:

Δy ₁＝d×tan2α

Wherein:

Δ y ₁' be that forward direction looks like the amount of moving or sweeping looks like the amount of moving;

D is that optical system secondary mirror summit is to the distance of secondary mirror image planes point;

α is that secondary mirror need to be around the angle of X-axis or Y-axis rotation.

Advantage of the present invention is:

The present invention adopts the method for rotation secondary mirror to carry out two-dimentional IMC does not increase optical system components, and light beam bore after primary mirror compression is less, when secondary mirror is controlled, the power of required motor and size are all very little, can increase system dimension and weight hardly, the popularization of the method, the picture rich in detail that obtains high resolving power, large fabric width for aerial camera has good facilitation, obtains the image of same fabric width, can reduce the Sortie of aircraft, significantly promote cost effectiveness.The present invention on the basis that does not increase optical element quantity, utilize catadioptric optical system in secondary mirror rotation carry out two-dimentional IMC, according to the forward direction of system in various flight parameters compensation flight courses, look like to move and sweeping looks like to move, when making aerial camera meet high-resolution, large format width, obtain picture rich in detail.

Accompanying drawing explanation

Fig. 1 is that in prior art, picture moves synthetic result schematic diagram;

Fig. 2 is the optical system structure schematic diagram of compensation method provided by the present invention institute foundation;

Wherein:

1-secondary mirror; 2-primary mirror; The follow-up lens of 3-.

Embodiment

Referring to Fig. 2, the present invention is based on conventional optical system and compensate.

System adopts conventional Zigzag type optical system, primary mirror 2, secondary mirror 1, follow-up lens 3, consists of.A point is the picture point of axle glazed thread after primary mirror, A ' is A point imaging point after secondary mirror, and B ' is A ' some imaging after follow-up lens combination, is when picture does not move, axle glazed thread imaging point, when system exists picture to move, the size according to the picture amount of moving, is rotated secondary mirror, in figure, green line is the postrotational position of secondary mirror, now A ' moves to A ", final picture point moves to B from B ' ", reaches the object of forward direction IMC.

Principle of the present invention is:

Set up departments system for right-handed coordinate system, optical axis direction is system Z axis forward, be Y-axis forward straight up, system secondary mirror summit is d to the distance of A ' of secondary mirror image planes, when secondary mirror is when X-axis is rotated an angle [alpha], the light anglec of rotation is 2 α, and the picture point A ' of secondary mirror will move to A in Y direction " position, mobile vertical range is:

Δy ₁＝d×tan2α

The vertical axle enlargement ratio of follow-up lens combination is ratio, A, and " after lens combination, its image height change amount of imaging is

Δy ₂＝Δy ₁×ratio

In like manner, in sweeping direction, while existing sweeping to look like to move, as secondary mirror, around an angle beta of y axle rotation, light rotates 2 β, and picture point has an offset Δ x in X-axis ₂, its size is

Δx ₂＝Δx ₁×ratio

When camera carries out aviation and takes pictures, calculate forward direction and look like to move Δ y according to the high ratio of speed, focal length, time shutter, according to sweeping angular velocity, focal length, time shutter, calculating sweeping looks like to move, according to the picture amount of moving calculating, secondary mirror is controlled, the picture amount of moving of bucking-out system both direction, compensation process is as follows.

1) calculate that forward direction looks like to move and sweeping looks like to move;

2) according to step (1) and optical system parameter, resolving secondary mirror need be around X-axis, the Y-axis anglec of rotation;

3) secondary mirror is controlled to rotation, retrieved image moves.

Claims (4)

1. the method for two-dimentional IMC is carried out in turn back system secondary mirror rotation of utilization, it is characterized in that: the described utilization method that the rotation of system secondary mirror carries out two-dimentional IMC of turning back comprises the following steps:

1), when camera carries out aviation and takes pictures, obtain respectively that forward direction looks like the amount of moving and sweeping looks like the amount of moving;

2) according to the resulting forward direction of step 1), look like the angle that in the calculation of parameter optical system of the amount of moving and optical system, secondary mirror need to rotate around X-axis;

And, according to the resulting sweeping of step 1), look like the angle that in the calculation of parameter optical system of the amount of moving and optical system, secondary mirror need to rotate around Y-axis;

Described X-axis is perpendicular to the horizontal direction of the plane of system optical axis; Described Y-axis is perpendicular to the vertical direction of the plane of system optical axis;

3) according to step 2) angle that need to rotate around X-axis and Y-axis of resulting secondary mirror be rotated control to the secondary mirror in optical system, and retrieved image moves.

2. the method for two-dimentional IMC is carried out in turn back system secondary mirror rotation of utilization according to claim 1, it is characterized in that: in described step 1), forward direction looks like the obtain manner of the amount of moving and is:

Wherein:

S _{forward direction}that forward direction looks like the amount of moving;

T _exposureexposure is the time shutter;

U is flying speed;

F ' is optical lens focal length;

H is flying height.

3. the method for two-dimentional IMC is carried out in turn back system secondary mirror rotation of utilization according to claim 1, it is characterized in that: in described step 1), sweeping looks like the obtain manner of the amount of moving and is:

S _scanning=f ' tan (ω T _exposure)

Wherein:

S _scanningit is the scanning picture amount of moving;

F ' is optical lens focal length;

ω is sweeping angular velocity;

T _exposureit is the time shutter.

4. according to turn back system secondary mirror rotation of the utilization described in claim 1 or 2 or 3, carry out the method for two-dimentional IMC, it is characterized in that: the specific implementation of the angle that described step 2) in calculating optical system, secondary mirror need to rotate around X-axis and Y-axis is:

Δy _l＝d×tan2α

Wherein:

Δ y ₁' be that forward direction looks like the amount of moving or sweeping looks like the amount of moving;

D is that optical system secondary mirror summit is to the distance of secondary mirror image planes point;

α is that secondary mirror need to be around the angle of X-axis or Y-axis rotation.

Images