CN101980283A - Method for dynamically compensating blind pixel - Google Patents

Abstract

The invention discloses a method for dynamically compensating a blind pixel. The method comprises the following steps of: arranging pixel gray values of a 3*3 window matrix dot picture element from small to large according to the remarkable abnormity of the blind pixel in a local window; if the absolute value of the difference value between a medium value and other picture element gray value is greater than a preset threshold value, determining the picture element as the blind pixel; detecting all picture elements of an M*N array by using a medium gray value instead of a blind pixel gray value; and compensating all blind pixels. Therefore, a high-quality image is obtained in a display device.

Description

A kind of dynamic blind element compensation method

Technical field

The present invention relates to non-refrigeration infrared detection technique field, be specifically related to the dynamic blind element compensation method of the optimization in the infrared image processing.

Background technology

(Infrared Focal Plane Array IRFPA) has been widely used in each military affairs, civil area as present latest generation detector to infrared focal plane array.Because the influence of factors such as manufacture craft, material, there is the blind element problem inevitably in the IRFPA device, thereby influences the signal to noise ratio (S/N ratio) of the image of infrared imaging system output.Blind element, or claim the unit of losing efficacy, be meant the too high or too low unit of response in the IRFPA device.The quantity of blind element and distribution have seriously influenced the output image quality of infrared imaging system, and blind element shows as bright spot or dim spot in image, in the imaging stage blind element are detected and compensate, and help to improve the quality of image.

The infrared focal plane array seeker of M * N, pixel responsiveness R _{(i, j)}For IRFPA under a frame period and certain dynamic range condition, the output signal voltage that pixel produces the per unit irradiation power,

I=1～M in the formula, j=1～N, V _s(i, j) be the (i, j) pixel is corresponding to the response voltage of irradiation power P, P be the (i, j) pixel the irradiation power to accepting.

The mean value of each effective pixel responsiveness of IRFPA,

M and N are respectively the line number and the columns of IRFPA pixel in the formula; D and h are respectively dead pixel number and overheated pixel number.In the actual measurement, d and h obtain through iterative computation repeatedly.

Blind element comprises dead pixel and overheated pixel, according to regulation among the GB GB/T17444-1998 " infrared focus plane Acceptance Test technical standard ", dead pixel is the pixel that responsiveness is lower than average response rate 1/10, and overheated pixel is the pixel that responsiveness is higher than 10 times of average response rates.In general, the response of the last normal probe unit imaging of IRFPA in certain dynamic range along with ambient temperature is linear change, as the curve among Fig. 12; Blind element is then different, the normal dynamic range of its response theory, and generally do not change with external environment.In addition, according to the response size, blind element comprises dead pixel and overheated pixel, respectively as curve 1 and the curve 3 of Fig. 1.

Processing to blind element comprises that blind element detects and two aspects of blind element compensation.It is the prerequisite and the basis of blind element compensation that blind element detects, and detects improperly then can bring extra noise to infrared image.Blind element compensation is the process that adopts the image information of effective image information around the blind element or front and back frame that the information of blind element position is predicted and substituted, therefore the thinking of blind element compensation has both direction: first, time bias, promptly utilize the frame-to-frame correlation of sequence image, obtain compensated information from consecutive frame.Its advantage is finely to be held in the edge of picture, and shortcoming is strong to the dependence of front and back frame; The second, space compensation, it is by the Pixel Information around the blind element it to be compensated.As linear interpolation compensation, medium filtering etc.This class methods advantage is that flow process is simple, workable.

Summary of the invention

Problem to be solved by this invention is: how a kind of dynamic blind element compensation method is provided, and this method is workable, and versatility is good, can detect blind element effectively, and blind element is compensated.

Technical matters proposed by the invention is to solve like this: a kind of dynamic blind element compensation method is provided, infrared focal plane array for M * N, if S (i, j) be the center be (i, j), size is 3 * 3 window matrix, wherein i ∈ (1, M), j ∈ (1, N), the pixel grey scale of each pixel is designated as S in the window _K(i, j), k=1,2 ... 9, S _K(i is j) from S ₁(i j) begins to S ₉(wherein the pixel grey scale of intermediate value is S for i, j) ascending arrangement ₅(i j), may further comprise the steps:

Step 1: with 3 * 3 window matrix S (i j) carries out line direction along view data and moves, promptly central point (i, j) traversal from point (2,2) begin to (2, j) have a few j=2,3...N-2;

Step 2: move a point, (i, j) grey scale pixel value of Nei all pixels is got intermediate value S by arranging from small to large with S at every turn ₅(i, j);

Step 3: calculate other pixel gray-scale values S except that intermediate value _k(i is j) with intermediate value S ₅(i, difference DELTA S j) _k(i, j), Δ S _k(i, j)=| S ₅(i, j)-S _k(i, j) |;

Step 4: all Δ S relatively _k(i, j) and the size of predetermined threshold value δ, if Δ S _k(i, j)＞δ, then this point is a blind element, uses S ₅(i j) replaces this grey scale pixel value S _k(i, j);

Step 5: return step 1,, jump to next line, begin to travel through new delegation up to j=N-1;

Step 6: up to (i j) travels through the some pixel at all non-edges,

S＝{(i，j)|i∈[2，M-1]，j∈[2，N-1]}。

Infrared imaging system mainly is the Real-time and Dynamic imaging to scenery, and the present invention is the medium filtering blind element compensation technique for a kind of optimization, and its algorithm is simple, can detect and compensate dynamic blind element.Beneficial effect is: algorithm is simple, is easy to hardware and realizes that versatility is good, can detect blind element effectively, and keep the edge of image details.Can realize that blind element detects and the unification of blind element compensation,, when detecting blind element apace, can carry out the blind element compensation effectively without the position of mark blind element.It is a kind of dynamic blind element backoff algorithm of instant processing, the significance difference opposite sex of utilizing in the scene motion process effectively pixel and the response of blind element in local window to exist, both can detect compensation, also can detect blind element at random with compensating images to the fixedly blind element of infrared focal plane array.

Description of drawings

Fig. 1 is an infrared focal plane array seeker pixel response curve synoptic diagram, and curve 1 is dead pixel, and curve 2 is normal pixel, and curve 3 is overheated pixel;

Fig. 2 be 3 * 3 window matrix S (i, j) in the grey scale pixel value of each pixel signature of arranging from small to large, k=1 in the square frame, 2...9 represents the grey scale pixel value S of pixel successively ₁(i, j), S ₂(i, j) ... S ₉(i, j), wherein gray scale intermediate value sentinel is S ₅(i, j);

The square frame 2 of Fig. 3 Intermediate grey be the window matrix S (i, center pixel j) (i, the pixel point that j) in M * N pixel, will travel through set S={ (i, j) | i ∈ [2, M-1], j ∈ [2, N-1] }.

Embodiment

Below in conjunction with accompanying drawing the present invention is further described:

Detailed technology scheme of the present invention is:

For the infrared focal plane array of M * N, establish S (i, j) be the center be (i, j), size is 3 * 3 window matrix, wherein (1, M), (1, N), the pixel grey scale of each pixel is designated as S to j ∈ to i ∈ in the window _k(i, j), k=1,2K 9.S _k(i is j) from S ₁(i j) begins to S ₉(wherein the pixel grey scale of intermediate value is S for i, j) ascending arrangement ₅(i, j), as Fig. 2.

Medium filtering blind element backoff algorithm process is as follows:

(1). with 3 * 3 window matrix S (i j) carries out line direction along view data and moves, promptly central point (i, j) from point (2,2) begin the traversal have a few (2, j), j=2,3...N-2;

(2). move a point, (i, j) grey scale pixel value of Nei all pixels as Fig. 2, is got intermediate value S by arranging from small to large with S at every turn ₅(i, j);

(3). calculate other pixel gray-scale values S except that intermediate value _k(i is j) with intermediate value S ₅(i, difference DELTA S j) _k(i, j), Δ S _k(i, j)=| S ₅(i, j)-S _k(i, j) |

(4). all Δ S relatively _k(i, j) and the size of predetermined threshold value δ, if Δ S _k(i, j)＞δ, then this point is a blind element, uses S ₅(i j) replaces this grey scale pixel value S _k(i, j)

(5). return step (1),, jump to next line, begin to travel through new delegation up to j=N-1;

(6). up to (i j) travels through the some pixel at all non-edges, and S={ (i, j) | i ∈ [2, M-1], j ∈ [2, N-1] }, as Fig. 3.

According to the local significantly abnormality of blind element, with the center be (i, j), size be 3 * 3 window matrix S (i, j), the blind element of traversal detection M * N image that infrared focus plane becomes.(i, the j) gray-scale value of interior all pixels is arranged from small to large, is labeled as S with S earlier ₁(i, j), S ₂(i, j) ... S ₉(i, j), intermediate value is S ₅(i, j).Get the difference of intermediate value and other gray-scale values, the absolute value delta S of its difference _k(i, j)=| S ₅(i, j)-S _k(i, j) |, compare Δ S _k(i, j) and the size of predetermined threshold value δ, if Δ S _k(i, j)＞δ, then this point is a blind element, uses S ₅(i j) replaces this grey scale pixel value S _k(i, j).(i j) follows all blind element points that direction detects compensation M * N pixel array with the window matrix S.

Claims (1)

1. dynamic blind element compensation method, for the infrared focal plane array of M * N, establish S (i, j) be the center be (i, j), size is 3 * 3 window matrix, wherein (1, M), (1, N), the pixel grey scale of each pixel is designated as S to j ∈ to i ∈ in the window _k(i, j), k=1,2 ... 9, S _k(i is j) from S ₁(i j) begins to S ₉(wherein the pixel grey scale of intermediate value is S for i, j) ascending arrangement ₅(i j), is characterized in that, may further comprise the steps:

Step 1: with 3 * 3 window matrix S (i j) carries out line direction along view data and moves, promptly central point (i, j) traversal from point (2,2) begin to (2, j) all point, j=2,3...N-2;

Step 2: move a point, (i, j) grey scale pixel value of Nei all pixels is got intermediate value S by arranging from small to large with S at every turn ₅(i, j);

Step 3: calculate other pixel gray-scale values S except that intermediate value _k(i is j) with intermediate value S ₅(i, difference DELTA S j) _k(i, j), Δ S _k(i, j)=| S ₅(i, j)-S _k(i, j) |;

Step 4: all Δ S relatively _k(i, j) and the size of predetermined threshold value δ, if Δ S _k(i, j)＞δ, then this point is a blind element, uses S ₅(i j) replaces this grey scale pixel value S _k(i, j);

Step 5: return step 1,, jump to next line, begin to travel through new delegation up to j=N-1;

Step 6: up to (i j) travels through the some pixel at all non-edges,

S＝{(i，j)|i∈[2，M-1]，j∈[2，N-1]}。

Images