CN100432697C - Linear array scan image non-uniform correction method based on statistical restraint model - Google Patents

Abstract

The present invention relates to a linear array scan image non-uniform correction method based on a statistical restraint model, which is used for scanning images by pushing a broom. The present invention comprises the following steps: step a, an initial image correcting parameter is obtained by a radiation scaling method or an image statistical model method, etc.; step b, target image data is corrected in a non-uniform mode, and a corrected image is output; step c, a certain statistical method is used to get a new correcting parameter in a non-uniform correction process; step d, the new correcting parameter and the initial image correcting parameter correct the model of the initial correcting parameter; step e, the images are listed by repeating step b to d until a preset requirement is reached. The non-uniform correction method of the present invention can be applied to spectral images and gray scale images, effectively eliminate the nonuniformity of the DN value of the image due to the response of the nonuniformity of a CCD detector, and effectively reduce the influence of ground objects existing in an adaptability algorithm based on a scene on the images.

Description

Linear array scan image non-uniform correction method based on statistical restraint model

Technical field:

The present invention relates to a kind of asymmetric correction method of linear array scan image, specifically, is a kind of airborne broom pushing type digital imaging system image non-uniform correction method based on statistical restraint model.

Background technology:

It is unescapable at present that the scanning imaging system of pushing broom is influenced by the spatial inhomogeneity distribution of linear CCD detector cells, and this non-homogeneous form makes the image quality decrease of acquisition, influences visual effect or follow-up application.The task of Nonuniformity Correction (NUC) algorithm is exactly compensation space heterogeneity, raising picture quality.The nonuniformity correction technology can be divided into two classes, based on demarcating and based on the alignment technique of scene.It is necessary that scaling method is accurately measured in the application of temperature at needs.Yet, in a lot of practical applications, do not need very accurate result, eliminate fixed pattern noise and only need corresponding heterogeneity to compensate.

In airborne remote sensing and mapping industry, the aviation digital camera is the trend of following aeroplane photography development, at present and deposit two kinds of high spatial resolution digital cameras---face battle array frame width of cloth formula and linear array push-broom type, many, the visual field broad of the every capable pixel number of linear array push-broom type camera wherein, utilize the position and attitude measuring system to solve a location difficult problem again, thereby quite paid attention at present.The high spatial resolution digital camera of push-scanning image is at every turn to the delegation's pixel imaging perpendicular to heading on ground, frequency is generally up to 200Hz, just can gather in per 10 minutes and surpass 100,000 row images, data volume is big, therefore entire image is proofreaied and correct, need on the one hand efficiently, on the other hand because instrument state, the environmental change that may exist in the data acquisition, the corresponding algorithm of needs introducing is revised in real time correction parameter or is upgraded, and improves calibration result.

Summary of the invention

The objective of the invention is to view data, its gray scale is carried out Nonuniformity Correction, in the hope of reaching the better image quality at hyperspectral imager acquisition in the existing remote sensing system.Nonuniformity Correction based on scene is subjected to the influence of atural object big, and the present invention revises the correction parameter model coefficient by the method for statistical weight, in order to reduce the influence of atural object to correction parameter.

Technical scheme of the present invention is as follows:

According to a kind of linear pull-broom type image non-uniform correction method of the present invention based on statistical restraint model, system directly carries out correction parameter Model Calculation and its coefficient Constraints Processing with radiation calibration or original image statistics and view data as the object of Treatment Analysis, and its step comprises:

A. obtain the initial calibration parameter model by methods such as radiation calibration or image statisticses;

B. generate new correction parameter: read an image block, view data is carried out mathematical statistics, obtain the needed statistics of Nonuniformity Correction model, thereby generate new correction parameter based on scene;

C. upgrade correction parameter: utilize image statistics data and new correction parameter original correction parameter to be revised the correction parameter that obtains upgrading according to the parameter update model;

D. utilize the correction parameter after upgrading image block to be carried out Nonuniformity Correction, the output calibration image;

E. read Next image block, repeating step b～d proofreaies and correct up to finishing entire image.

Further in step b, also utilize methods such as weighting statistics to obtain new correction coefficient, the assembly average of supposing the output signal of each probe unit of arbitrary wave band in the entire image scope is constant, reaches the removal of images band by each the probe unit signal weighting to non-homogeneous high spectrum image.For example gray scale row equalization is exactly a kind of image homogeneity correction statistical method, and this statistical method thinks that the heterogeneity equivalence of row causes that for the gain of row pixel is different based on this point, the modified value (just new parameter) that obtains each pixel is:

$X(i,j)=X^{\′}(i,j)\×\frac{M}{M\left(j\right)},$

Wherein: (i j) is revised value to X; (i j) is measured value to X '; M is the average gray of entire image.M (j) goes up the mean value of corresponding photosensitive first entire image previous column for CCD:

$M\left(j\right)=\frac{\underset{i=0}{\overset{m}{\mathrm{\Σ}}}{\mathrm{DN}}_{\mathrm{pixel}(i,j)}}{m},$

$M=\frac{\underset{i=0}{\overset{k}{\mathrm{\Σ}}}\underset{j=0}{\overset{m}{\mathrm{\Σ}}}{\mathrm{DN}}_{\mathrm{pixel}(i,j)}}{k\×m},$ In the formula, i, the row and column on the j difference representative image, k, line number and columns on the m difference representative image; DN _{Pixel (i, j)}Pixel l (i, digital value j) on the representative image then.

In step c, the parameter update rule can according to circumstances design, and the simplest renewal can be adopted the weighted mean algorithm, establishes M ₀Be initial parameter, M ₁Be the new argument based on scene, M ' is the parameter after upgrading, and then the weighted mean algorithmic notation is:

M′＝aM ₀+bM ₁；

In steps d, adopt the correction parameter after upgrading that original correction parameter model is revised, because the Nonuniformity Correction based on scene is subjected to the influence of atural object big, the objective of the invention is to method by statistical weight, constantly revise the correction parameter model coefficient, thereby reduce the influence of atural object image.Correction model has been considered original image and subsequent image, makes it have more adaptability.

As mentioned above, advantage of the present invention is: new correction parameter is revised original correction parameter model with original correction parameter, and the effect of initial calibration coefficient and image statistics parameter has all been considered.And, the present invention directly carries out correction parameter Model Calculation and its coefficient Constraints Processing with radiation calibration or original image statistics and view data as the object of Treatment Analysis, therefore, do not increase the design complexities of existing hardware system and increase cost and just can increase to picture quality.

Description of drawings

Fig. 1 is the algoritic module block diagram among the present invention.

Fig. 2 is the algorithm flow chart among the present invention.

Fig. 3-1～Fig. 3-the 6th, according to the result image of the inventive method to the high spectrum image of selected one data that hundreds thousand of row are arranged, wherein Fig. 3-1,3-3,3-5 are original image, Fig. 3-2,3-4,3-6 are for through the image behind the Nonuniformity Correction.

Embodiment:

Provide embodiments of the invention below in conjunction with Fig. 1～Fig. 3-6, and described in detail, so that this method characteristics and function are described better, enable to be easier to understand the present invention, rather than be used for limiting scope of the present invention.

Please consult Fig. 1 earlier, as shown in the figure, Fig. 1 is the heteropical correcting algorithm module frame chart of set lasting statistical restraint model in the airborne broom pushing type digital imaging system, and each functions of modules is described as follows:

Initial calibration parameter model module M1 is by the initial calibration parameter model that is obtained by radiation calibration or great amount of images statistics;

Nonuniformity Correction module M2 carries out the heterogeneity image statistics to destination image data D2, exports the Nonuniformity Correction parameter based on scene, and under the acceptable situation of rectification parameter image is proofreaied and correct;

Nonuniformity correction parameter model module M3, its new certain model of statistics utilization that utilizes M2 to produce to the initial calibration parameter retrains;

Utilize methods such as weighting statistics to obtain new correction coefficient in the Nonuniformity Correction process, wherein: (i j) is revised value to X; (i j) is measured value to X '; M is the average gray of entire image.Then the modified value of each pixel is: $X(i,j)=X^{\′}(i,j)\×\frac{M}{M\left(j\right)};$ New correction parameter is revised original correction parameter model with original correction parameter, can use average weighted algorithm, and weighting coefficient is set according to system's needs;

Image sequence is repeated the operation steps of module M1～M3, final output is subjected to scene to influence little image homogeneity correction parameter, the image of output can be the correction result who utilizes the correction parameter of each step output, also can be the correction result who obtains at last behind the final correction parameter.

Of the present invention based on the linear array scan image non-uniform correction method that continues statistical restraint model, implementation step is as follows:

1) obtains by methods such as radiation calibration or image statisticses and generate the initial calibration parameter model behind the initial pictures;

2) get image i piece;

3) method by statistical average generates new parameter;

4) new argument and the initial parameter that generate are synthesized the new parameter of correction parameter model by weighted-average method, and this parameter is stored wherein as the undated parameter of initial calibration model;

5) with the calibration model that has synthetic parameters image block i is carried out Nonuniformity Correction;

6) judge whether the image block quality after proofreading and correct meets the demands, if do not satisfy, then execution in step 7); If meet the demands, then execution in step 8);

7) parameter update;

8) get image block i+1, judge whether image finishes, if do not finish, then repeating step 2)～6); Otherwise just finish.

Consult Fig. 2, it illustrates the present invention and resides at lasting statistical restraint model Nonuniformity Correction program 100 in the airborne broom pushing type digital imaging system, and operating procedure is as follows:

S1000 generates the initial calibration parameter model by methods such as radiation calibration or original image statistics, and its parameter matrix is

S1001 gets image i piece, I _i

S1002 is by the new parameter matrix of method generation of statistical average

S1003 is with the new argument matrix that generates

With the initial parameter matrix

By the synthetic new parameter matrix of correction parameter model of weighted-average method ${\stackrel{\mathrm{\ρ}}{R}}^{\′}=\frac{m}{m+n}{\stackrel{\mathrm{\ρ}}{R}}_i\left(I_i\right)+\frac{n}{m+n}{\stackrel{\mathrm{\ρ}}{R}}_0\left(I_0\right),$ And as the storage of the undated parameter of initial calibration model wherein with this parameter;

S1004 is with having the synthetic parameters matrix

Calibration model image block i is carried out Nonuniformity Correction;

S1005, whether the image block quality after judge proofreading and correct meets the demands, if do not satisfy, execution in step S1006 then, if meet the demands, execution in step S1007 then;

S1006, parameter update;

S1007 gets image block i+1, judges whether image finishes, if finish, and repeating step S1001～S1005 then; Otherwise just carry out S1008, EOP (end of program).

At last, see also Fig. 3-1～Fig. 3-6, Fig. 3-1 wherein, Fig. 3-3, Fig. 3-5 are original image; Correspondingly, Fig. 3-2, Fig. 3-4, the image of Fig. 3-6 after for the Nonuniformity Correction of doing through the inventive method can find out very clearly that secret note band fuzzy in the original graph is through Nonuniformity Correction, become and desalinated, illustrate that the gradation of image value after proofreading and correct has better homogeneity.

Claims (4)

1, a kind of linear array scan image non-uniform correction method based on statistical restraint model comprises step:

A. obtain initial pictures by radiation calibration or original image statistical method and obtain the initial calibration parameter model;

B. read an image block, destination image data is carried out mathematical statistics, obtain the needed statistics of Nonuniformity Correction model, generate new correction parameter based on scene;

C. utilize image statistics data or new correction parameter original correction parameter to be revised the correction parameter that obtains upgrading according to the parameter update model;

D. utilize the correction parameter after upgrading the target image piece to be carried out Nonuniformity Correction, the target image of output calibration;

E. read next image block, repeating step b～d finishes up to the entire image correction.

2, the linear array scan image non-uniform correction method based on statistical restraint model according to claim 1, it is characterized in that, among the step b, also utilize the weighting statistical method to obtain new correction coefficient, the assembly average of setting the output signal of each probe unit of arbitrary wave band in the entire image scope is constant, comes the removal of images band by each the probe unit signal weighting to non-homogeneous high spectrum image.

3, the linear array scan image non-uniform correction method based on statistical restraint model according to claim 1, it is characterized in that among the step c, the image non-uniform that obtains at system is apparent in view when weak signal, adopt gray scale row equalization, the modified value that obtains each pixel is: $X(i,j)=X^{\′}(i,j)\×\frac{M}{M\left(j\right)},$

Wherein: X (i, j) be revised value, X ' (i is the average gray, M (j) of the entire image mean value for corresponding photosensitive first entire image previous column on the CCD for measured value, M j):

$M\left(j\right)=\frac{\underset{i=0}{\overset{m}{\mathrm{\Σ}}}{\mathrm{DN}}_{\mathrm{pixel}(i,j)}}{m},$

$M=\frac{\underset{i=0}{\overset{k}{\mathrm{\Σ}}}\underset{j=0}{\overset{m}{\mathrm{\Σ}}}{\mathrm{DN}}_{\mathrm{pixel}(i,j)}}{k\×m},$ In the formula, i, the row and column on the j difference representative image, k, line number and columns on the m difference representative image; DN _{Pixel (i, j)}Pixel l (i, digital value j) on the representative image then.

4, the linear array scan image non-uniform correction method based on statistical restraint model according to claim 1, it is characterized in that, in the steps d, also adopt new correction parameter original correction parameter model to be revised with original correction parameter, revise the correction parameter model coefficient, reduce the influence of atural object image.

Images