Background technique
Currently, infrared imaging is extremely important in industry, military and medical applications, because its available people's is infrared
Information.
Infrared focal plane array (IRFPA) is mainly used for infrared imaging system, and infrared focal plane array IRPFA is by small-scale transfer
Sensor and reading circuit composition, belong on infrared optical system focal plane, can make in entire visual field each pixel of scenery with
One sensitive first corresponding polynary planar array infrared detector.
For infrared focal plane array IRPFA, due to the variation of parameter in the mismatch and manufacturing process of element, pixel
The bias voltage of roomage response and reading circuit is different.Inhomogeneities leads to heterogeneity noise, and referred to as fixed mode is made an uproar
Sound (FPN), its presence seriously reduce the quality of infrared image collected.Wherein, in view of in infrared focal plane array IRPFA
In, reading circuit is usually same row pixel or shares the same output circuit with a line pixel.Due to column output circuit
Bias voltage is not quite identical, causes comprising the fringes noise with longitudinal stripe (i.e. column striped) for main feature in image, i.e.,
For non-uniform noise.
In order to promote the quality of infrared image, carry out Nonuniformity Correction (non-uniformity correction,
It NUC), is the steps necessary for improving infrared image.
Detector a row or column, which exports, shares an amplifier, therefore can generate heterogeneity item laterally or longitudinally
Line, this fringes noise heterogeneity noise special as one kind is especially prominent in infrared focal plane imaging system, commonly
Some Nonuniformity Corrections or two o'clock asymmetric correction method can not all filter out such noise.
In early stage research, by using statistics, it is assumed that by the mean value of each sensor and standard deviation and gain and deviation
Parameter is associated, it is assumed that input irradiation level is equally distributed stochastic variable, and all pixels sensor is having the same
Value and standard deviation, in this way can be by using linear model, to estimate the biasing and gain of each sensor.But this vacation
If it is only very long in image sequence and move it is sufficiently large so that when many different pieces of the inswept scene of each sensor
It is reasonable.
Non-uniform correction method of the another kind based on algebra scene, this method is independent of any system about scene temperature
Meter or scene diversity are it is assumed that it is used to extract about deviation using the estimation of the interframe sub-pixel shift in image sequence with linear
The interpolation model of the movement of heteropical information.The gain of each sensor and bias modeling are Gauss-by scheme also
Markov stochastic variable, and update the gain of these sensors using Kalman filter and bias estimated value.It is basic herein
On, by disabling Kalman filter parallel, according to the dynamic model parameters of itself, to estimate the gain and partially of each sensor
Difference.Realize that gain and the final of deviation are estimated by forming the weighted superposition of all estimations presented by each Kalman filter
Meter.
But the existing treatment scheme to infrared single-frame images, complex, real-time is poor, has one
Fixed limitation can not timely and effectively be corrected fringes noise present in infrared single-frame images, promote final obtain
Infrared single-frame images picture quality.
Summary of the invention
In view of this, the object of the present invention is to provide a kind of removing method of infrared image fringes noise, it can be timely
Effectively fringes noise present in infrared single-frame images is corrected, promotes the image of the infrared single-frame images finally obtained
Quality has great practice significance.
For this purpose, the present invention provides a kind of removing methods of infrared image fringes noise, comprising the following steps:
The first step obtains the original infrared single-frame images comprising column fringes noise;
Second step, according to original infrared single-frame images, establish the column fringes noise of adjacent column in original infrared single-frame images
Between departure function;
Third step minimizes departure function, then utilizes recursive fashion, estimates the column fringes noise of each column
Noise figure;
4th step, by the original infrared single-frame images comprising column fringes noise, subtract the column of each column estimated
The noise figure of fringes noise obtains the infrared list for having eliminated fringes noise to realize the correction to original infrared single-frame images
Frame image.
Wherein, in the first step, it from the output signal of infrared sensor, obtains original infrared comprising column fringes noise
Single-frame images.
Wherein, in the first step, the formula of original infrared single-frame images z (i, j) indicates are as follows:
Z (i, j)=u (i, j)+b (j), formula (1);
In the equation above, i, j are the line number and columns of pixel respectively, and b (j) is in infrared focal plane array IRFPA
Jth row reading circuit biasing, z is original infrared single-frame images, and u is ideal true infrared image.
Wherein, in second step, in original infrared single-frame images between the column fringes noise of adjacent column departure function E public affairs
Formula, specific as follows:
In the equation above, M is the line number of image, and u (j) is the average value of jth column pixel, ux(j) be u (j) ladder
Degree.
Wherein, by solution Euler-Lagrange equation, carry out the minimum of function to achieve the objective E, specific formula is as follows:
zxx(j)-bxx(j)-λ [b (j)]=0;
In the equation above, zxx(j)、bxxIt (j) is z (j) respectively, the second dervative of deviation b (j) is iterative process
Intermediate quantity.
By the above technical solution provided by the invention as it can be seen that compared with prior art, the present invention provides a kind of infrared
The removing method of image stripe noise timely and effectively can carry out school to fringes noise present in infrared single-frame images
Just, the picture quality of the infrared single-frame images finally obtained is promoted, there is great practice significance.
Specific embodiment
In order to enable those skilled in the art to better understand the solution of the present invention, with reference to the accompanying drawing with embodiment to this
Invention is described in further detail.
Referring to Fig. 1, it is based on the red of recursive fashion that the present invention, which provides a kind of removing method of infrared image fringes noise,
The removing method of outer image stripe noise, specifically includes the following steps:
The first step obtains the original infrared single-frame images comprising column fringes noise;
In the first step, it in specific implementation, can directly obtain from the output signal of infrared sensor comprising column striped
The original infrared single-frame images of noise.
Second step, according to original infrared single-frame images, establish the column fringes noise of adjacent column in original infrared single-frame images
Between departure function;
Third step minimizes departure function, then utilizes recursive fashion, estimates the column fringes noise of each column
Noise figure;
4th step, by the original infrared single-frame images comprising column fringes noise, subtract the column of each column estimated
The noise figure (i.e. noise vector value) of fringes noise, to realize the correction to original infrared single-frame images, item has been eliminated in acquisition
The infrared single-frame images of line noise.
In the present invention, about the linear imaging model of infrared sensor.The output signal of infrared sensor is (i.e. practical defeated
Infrared image and original infrared single-frame images out) formula of z (i, j) can indicate are as follows:
Z (i, j)=u (i, j)+b (j), formula (1);
In the equation above, i, j are the line number and columns of pixel respectively, and b (j) is infrared focal plane array (IRFPA)
In jth row reading circuit biasing, z is noisy reality output infrared image (i.e. original infrared single-frame images), and u is reason
The true infrared image (not having noisy infrared single-frame images, also the infrared single-frame images to have eliminated fringes noise) thought.
It should be noted that for the present invention, according to formula (1), in order to restore incident in image z from being destroyed
Infra-red radiation, should estimate first bias b (j).In infrared image, the infra-red radiation of adjacent pixel is typically considered in space
It is highly relevant, therefore the average value of the column pixel of true picture u should be slowly varying signal.And deviation b (j) is only
Vertical random noise, it will lead to quick localized variation.Therefore, the notable difference between the column of reality output infrared image z
Mainly generated by deviation b (j), and the difference between the column of true infrared image u should be smaller, therefore, original infrared single frames
In image between the column fringes noise of adjacent column departure function E (also referred to as objective function) formula, it is specific as follows:
In the equation above, M is the line number of image, and u (j) is the average value of jth column pixel.ux(j) be u (j) ladder
Degree.
On the other hand, it is not enough to change the dynamic range of true infrared image u, therefore, adjacent column in view of deviation b (j)
Departure function (also referred to as objective function) E can be between column fringes noise is defined as:
In the equation above, z (j) is the average value that jth arranges in reality output infrared image, zx(j) be z (j) ladder
Degree, bxIt (j) is to bias the gradient of b (j), and know based on formula (1): u (j)=z (j) b (j).By minimizing target letter
Number (i.e. minimum departure function) carrys out estimated bias b (j).Wherein, the first item of objective function is known as smooth item, it is intended to minimize
Correct the difference between the column of image.Section 2 is known as bound term, and for guarding against deviations, b (j) excessively significantly changes image.Ginseng
Number λ controls the balance between two.
In the present invention, the minimum of function to achieve the objective E can be carried out, specifically by solving Euler-Lagrange equation
Formula is as follows:
zxx(j)-bxx(j)-λ [b (j)]=0, formula (4);
In the equation above, zxx(j)、bxxIt (j) is z (j) respectively, the second dervative of deviation b (j) is iterative process
Intermediate quantity.The numerical value solution of formula (4) is as follows:
In the equation above, bo(i, j) is primary data, and n is the number of iterations.Δ t is the iteration of control convergence speed
?.Iteration may cannot be restrained since step-length is excessive.Show the step Δ t in [0.1,0.01] range most by experiment
It is suitable for this method.Using second-order central finite difference calculus, the second dervative for obtaining z (i, j) and b (i, j) can be calculated.
In the present invention, the deviation of estimation can be used, the reality output infrared image Z (i, j) that Lai Jiaozheng is observed is
Meet following formula:
WhereinInfrared image to use the above method to estimate obtains each column deviation,It indicates using estimation
Deviation correction after close to ideal image.Since deviation b (j) is changed over time slowly, it can be considered that adjacent frame
Between deviation be constant.The estimation of biasing b (j) does not need to realize within the time of a frame.Bias the recursive estimation of b (j)
It is written as follows:
In the equation above, t indicates frame number.This recursive method can independently iterate to calculate the deviation of every frame,
It is significant in a frame time to reduce calculating, it is very suitable to the application of real-time display.
It was proved that parameter lambda is appropriate value in [0.01,0.1] range.It, can be by λ in specific implementation
It is respectively set to 0.1 with Δ t, the number of iterations is fixed on 200 times.
It should be noted that being based on above technical scheme it is found that considering the single-frame images based on scene for the present invention
Processing, and algorithm complexity is reduced, there is positive help to the promotion of Nonuniformity Correction.It is provided by the invention to be based on
The removing method of the infrared image fringes noise of recursive fashion.This method can estimate striped deviation based on scene image, thus
Fringes noise is corrected, and is suitable for the non-uniform situation of striped.
Compared with prior art, for the removing method of infrared image fringes noise provided by the invention, have with
Under advantageous effects:
1, output valve is considered as linear model with the variation of row reading circuit deviation by the present invention.It, will be infrared according to the model
Difference in image between adjacent column is described as departure function, by finding deviation, keeps difference as small as possible.To infrared image into
Row correction eliminates fringes noise using the deviation of estimation.
2, the present invention can substantially reduce calculation amount in a frame time, improve algorithm speed by recursive mode.
In conclusion compared with prior art, a kind of removing method of infrared image fringes noise provided by the invention,
It can timely and effectively be corrected fringes noise present in infrared single-frame images, promote the infrared single frames finally obtained
The picture quality of image has great practice significance.
The above is only a preferred embodiment of the present invention, it is noted that for the ordinary skill people of the art
For member, various improvements and modifications may be made without departing from the principle of the present invention, these improvements and modifications are also answered
It is considered as protection scope of the present invention.