CN101144740A - High-altitude infrared imaging method based on multi-element surface array splicing - Google Patents

Abstract

The invention discloses an altitude infrared imaging method based on a multi-element area array splicing. An area array picture frame type imaging is adopted, a large breadth is gained through the object space scan on the passing rail direction of a swing mirror, the swing mirror works in a scanning and gazing imaging mode, the infrared area array detector images by exposure when the swing mirror is at the gazing position, the overlapping ratio between two adjacent images is kept 10 percent and above, the splicing of the adjacent images adopts the measure algorithm of the correlation function in image matching, and the seamless splicing of the images is ensured. The imaging method improves the integration time of the system, and efficiently improves the sensibility of the infrared system, and the picture frame type imaging solves the severe distortion of the image caused by the posture affection of a plane. The invention solves the technological problems of the high resolution, the large breadth, and the high sensitivity of an altitude on-board infrared camera.

Description

High-altitude infrared imaging method based on multi-element surface array splicing

Technical field

The present invention relates to high-altitude Airborne IR camera remotely sensed image method, specifically be meant the formation method that adopts multi-element surface array splicing.

Background technology

Infrared camera mainly contains three kinds of imaging modes, as shown in Figure 1:

Shake the mode of sweeping: detector adopts unit component, and the imaging of wearing the rail direction is realized that by scanning mechanism the motion of aircraft then realizes along the imaging of rail direction.This mode can realize big view field imaging, detector pixel minimum number.But owing to adopt object space mechanical scanning, volume is big, and the pixel residence time is short, is unfavorable for improving the detection sensitivity of system.

Push away the mode of sweeping: detector adopts multicomponent device (face battle array or linear array), wears the rail direction by the imaging simultaneously of a plurality of pixels, is finished by moving of aircraft along the imaging of rail direction.Owing to adopt the scanning of picture side, there is not mechanical scanning mechanism, system bulk is little, in light weight, and the pixel residence time is long, helps improving the detection sensitivity of system.Shortcoming is to cut secondary width and spatial resolution when higher, needs the optical system of high-resolution sensitive detection parts and big visual field, and system is difficult to realize.

Polynary and the formula of sweeping claims mixed type scanning again: be between a kind of light spectrum image-forming mode of shaking between the formula of sweeping and the push-broom type.Detector adopts multicomponent device, what be different from push-broom type is that the multiunit detector imaging is not to wear the rail direction but along the imaging simultaneously of rail direction, it is once inswept to be that the rail direction is worn on the every edge of scanning mechanism, and detector n pixel will be simultaneously along wearing the parallel inswept n band of rail direction.Its advantage is in the big detection sensitivity that can effectively improve system under the secondary width of cutting.Shortcoming is to be subjected to aspect to influence image to produce distortion.

These three kinds of imaging modes are ripe technically, can satisfy the needs of infrared system design in certain application, but under high-altitude high sensitivity and the requirement of wide visual field, can not satisfy the requirement of system design.

Summary of the invention

The purpose of this invention is to provide a kind of high-altitude Airborne IR camera imaging method based on multi-element surface array splicing, the scanning form of this method adopts oscillatory scanning, detector adopts the multi-element surface array infrared focal plane detector, solved by multi-element surface array and surveyed the seamless spliced of imaging, reached the requirement of high sensitivity, high spatial resolution and the big fabric width of high-altitude infrared imaging.

A kind of high-altitude Airborne IR camera imaging method based on multi-element surface array splicing, its step comprises: wearing the rail direction, adopt the scanning of 45 ° of pendulum mirrors, system optics observation visual field covers a sweep trace from left to right, when motor-driven pendulum mirror swings to when staring the position, face battle array infrared focal plane detector begins exposure image, end exposure is read and is write down frame data by electronic system, finish an imaging cycle, wait for that motor movement restarts to expose and signal is read to frame position down, overlapping 10% between the consecutive frame, to guarantee the seamless spliced of under the unstable condition of aspect ground image.

The splicing of consecutive frame image is adopted the related function in the image coupling to estimate algorithm, mutual select target point and point to be matched and is discerned same place.Same place is the same unique point in adjacent two width of cloth doubling of the image zones.Concrete grammar is as follows:

A. determine earlier in preceding piece image that a point to be located is an impact point, with this put be the center select the individual pixel of m * n (getting m=n) the gray scale array as target area D, gray matrix is G (g _{I, j}) (i=1,2 ..., m; J=1,2 ..., n), m and n are odd number, the gray scale function corresponding with G is g (x, y) ((x, y) ∈ D);

B. estimate the scope that same place may exist, to be the center with the mutual point of selecting to be matched of mouse, the gray scale array of setting up the individual pixel in k * 1 (k〉m, 1〉n) is as field of search D ' in the piece image of back, gray matrix be G ' (g ' _{I, j}) (i=1,2 ..., k; J=1,2 ..., 1), k and 1 also is an odd number, the gray scale function corresponding with G ' is g ' (x ', y ') ((x ', y ') ∈ D '); The sub-piece of the capable n row of any one m among the G ', promptly search window is designated as: G ' _{R, c}=(g ' _{I+r, j+c}) (i=1,2 ..., m; J=1,2 ..., n;

r＝int(m/2)+1，int(m/2)+2，…，k-int(m/2)；c＝int(n/2)+1，int(n/2)+2，…，1-int(n/2))。

C. the estimation formulas of discrete gradation data pair correlation function is:

$R(c,r)=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{g}_{i,j}{g}_{i+r,j+c}^{\′},---\left(3\right)$

If R (c ₀, r ₀) R (c, r) (r ≠ r ₀, c ≠ c ₀), c then ₀And r ₀Be the row, column parameter of field of search image with respect to the target area blurring, the center pixel of search window is considered to same place.

Image rectification and the splicing of location, overlapping region:

Right simplification is closed and is based on adjacent two width of cloth image slices of affined transformation:

$\left\{\begin{array}{c}{X}_2=a_0+a_1{x}_1+a_2{y}_1\\ y_2=b_0+b_1{X}_1+b_2{y}_1,\end{array}\right.---\left(4\right)$

The relative position orientation of adjacent two width of cloth images is determined by 6 parameters in the formula (4), by discerning 3 unique points of the same name of two width of cloth images, tries to achieve this 6 transformation parameters, just can transform to the back piece image in the image space coordinate system of preceding piece image.Weave into software according to above-mentioned consecutive frame image split-joint method and be stored in the computing machine, carry out the later stage pre-service and the correction of image, finish the splicing of each two field picture by software.

The invention has the advantages that: employing face battle array staring imaging, improved the detector integrates time, system guarantees high-temperature sensitivity in high spatial resolution; It is minimum that the scalloping that the imaging of picture formula is introduced aspect reaches; Make system can reach big observation visual field more than 45 ° by pendulum mirror scanning; Overlapping 10% between the consecutive frame, to guarantee the seamless spliced of under the unstable condition of aspect ground image.

Description of drawings

Fig. 1 is existing three kinds of imaging mode synoptic diagram;

Fig. 2 is an imaging mode principle schematic of the present invention;

Fig. 3 is pendulum mirror motion angular velocity curve map;

Fig. 4 is pendulum mirror movement position curve map;

Fig. 5 is a camera optics system equivalence index path;

Fig. 6 is the image mosaic software flow pattern.

Embodiment

Below in conjunction with drawings and Examples a kind of high-altitude Airborne IR camera imaging method based on multi-element surface array splicing of the present invention is described in further detail:

The concrete parameter of infrared camera is as follows:

Total visual field: 45 °;

Flying height: 12,000～20,000 meter high-altitude;

Pixel number: 320 * 256 yuan;

Instantaneous field of view: 0.1mrad;

Wave band: 3～5um;

Temperature control: be better than 0.1K;

Optical system bore: 100mm.

1. pendulum mirror 1 adopts the almag metallic mirror, is driven by high-precision motor, finishes the spacescan of camera instantaneous field of view.Angular scanning speed curve such as Fig. 3 of pendulum mirror, position curve such as Fig. 4 of pendulum mirror.Pendulum mirror drive motor adopts brush DC swing angle electric (Cambridge Technology, the Model 6900 of Inc), and pendulum angle is ± 11.25 °.

2. optical system adopts the Cassegrain telescope mode, and optical system as shown in Figure 5.Primary mirror 3 and secondary mirror 2 are non-spherical reflector, and the silver-plated reflectance coating of minute surface is to improve the optical efficiency of system.

3. detector is selected SOFRADIR company 320 * 256 focal plane HgCdTe devices in the detector assembly 4, and response wave length is 3～5 μ m, and the pixel number is 320 * 256 yuan, and photosensitive elemental size is 30 μ m * 30 μ m, and detectivity is greater than 1 * 10 ¹¹CmHz ^1/2W ^-1, working temperature is 77K～90K, the supporting IDTL061 sterlin refrigerator of sterlin refrigerator apolegamy SOFRADIR company.Above-mentioned infrared camera parameter is to be used for illustrating feature of the present invention, technical feature and functional characteristics, but not is used for limiting the scope of the invention.

Adopt the inventive method in the laboratory simulation imaging, to obtain test findings preferably.

Claims (2)

1. the high-altitude infrared imaging method based on multi-element surface array splicing is characterized in that comprising the steps:

Wearing the rail direction, adopt the scanning of 45 ° of pendulum mirrors, system optics observation visual field covers a sweep trace from left to right, when motor-driven pendulum mirror swings to when staring the position, face battle array infrared focal plane detector begins exposure image, and end exposure is read and write down frame data by electronic system, finish an imaging cycle, wait for that motor movement restarts exposure and signal is read to frame position down, overlapping 10% between the consecutive frame image, to guarantee the seamless spliced of under aspect shakiness condition ground image.

2. according to a kind of high-altitude infrared imaging method based on multi-element surface array splicing of claim 1, it is characterized in that: the splicing of said consecutive frame image is adopted the related function in the image coupling to estimate algorithm, mutual select target point and point to be matched and is discerned same place; Same place is the same unique point in adjacent two width of cloth doubling of the image zones, and concrete grammar is as follows:

A. determine earlier in preceding piece image that a point to be located is an impact point, with this put be the center select the individual pixel of m * n (getting m=n) the gray scale array as target area D, gray matrix is G (g _{I, j}) (i=1,2 ..., m; J=1,2 ..., n), m and n are odd number, the gray scale function corresponding with G is g (x, y) ((x, y) ∈ D);

B. estimate the scope that same place may exist, in the piece image of back to be the center with the mutual point of selecting to be matched of mouse, set up a k * l (k＞m, the gray scale array of the individual pixel of l＞n) be as field of search D ', gray matrix be G ' (g ' _{I, j}) (i=1,2 ..., k; J=1,2 ..., l), k and l also are odd number, the gray scale function corresponding with G ' is g ' (x ', y ') ((x ', y ') ∈ D '); The sub-piece of the capable n row of any one m among the G ', promptly search window is designated as: G ' _{R, c}=(g ' _{I+r, j+c}) (i=1,2 ..., m; J=1,2 ..., n; R=int (m/2)+1, int (m/2)+2 ..., k-int (m/2); C=int (n/2)+1, int (n/2)+2 ..., l-int (n/2));

C. the estimation formulas of discrete gradation data pair correlation function is:

$R(c,r)=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{g}_{i,j}{g^{\′}}_{i+r,j+c}---\left(3\right)$

If R (c ₀, r ₀)＞R (c, r) (r ≠ r ₀, c ≠ c ₀), c then ₀And r ₀Be the row, column parameter of field of search image with respect to the target area blurring, the center pixel of search window is considered to same place;

Image rectification and the splicing of location, overlapping region:

Right simplification is closed and is based on adjacent two width of cloth image slices of affined transformation:

$\left\{\begin{array}{c}{x}_2=a_0+a_1{x}_1+a_2{y}_1\\ y_2=b_0+b_1{x}_1+b_2{y}_1\end{array}\right.,---\left(4\right)$

The relative position orientation of adjacent two width of cloth images is determined by 6 parameters in the formula (4), by discerning 3 unique points of the same name of two width of cloth images, tries to achieve this 6 transformation parameters, just can transform to the back piece image in the image space coordinate system of preceding piece image;

Above-mentioned consecutive frame image split-joint method is weaved into software and is stored in the computing machine, carries out the later stage pre-service and the correction of image by software, finishes the splicing of each two field picture.

Images