CN111340712A - Cold reflection restoration method for environment temperature self-adaptive infrared imaging system - Google Patents
Cold reflection restoration method for environment temperature self-adaptive infrared imaging system Download PDFInfo
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Abstract
An environment temperature self-adaptive infrared imaging system cold reflection repairing method includes that when cold reflection black spots appear before an infrared imaging system leaves a factory, distribution parameters of each pixel of an image are calculated and stored in the system, and meanwhile, the current temperature TS and the temperature T0 calibrated by non-uniformity coefficients before leaving the factory are stored; when the device is powered on for use, the distribution parameters of each pixel, TS and T0 are read from the storage device; when the equipment is electrified and non-uniformly corrected, recording the temperature Tc during correction; when the device is used, each pixel is subjected to non-uniform correction, a temperature correlation coefficient is calculated in real time according to the current system temperature T, TS, T0 and Tc, a repair parameter of each pixel is calculated according to the distribution parameter and the temperature correlation coefficient, the repair parameter is superposed on the non-uniform correction result of each pixel, and finally, an image subjected to cold reflection black spot repair is output.
Description
Technical Field
The invention relates to the technical field of infrared imaging, in particular to a method for repairing cold reflection black spots of an infrared imaging system.
Background
When the refrigeration type infrared imaging system with the optical system is used for imaging, a refrigeration surface of an internal detector is reflected by a preposed optical element, the detector can detect a signal of a self-refrigeration surface with a much lower temperature relative to the environment, a black spot is formed in the center of a field of view, the imaging quality and target identification are seriously influenced, and the imaging defect caused by repeated reflection is called cold reflection and also called temperature difference regeneration effect. The temperature of the infrared focal plane is controlled between 90K and 110K, the thermal difference with the ambient temperature of 300K is large, and the phenomenon of strong cold reflection can also occur in extremely weak reflection. The control of cold reflection is a difficult point of a refrigeration type infrared optical system, particularly for a complex zooming optical system, the difficulty of controlling a cold image in a zooming process is higher, a better processing mode is not available at present, the control can be only carried out on design and film coating, the design and processing difficulty is increased, and the complete removal is difficult. The traditional non-uniform correction algorithm can correct cold reflection when the current temperature is not changed, but when the position of a view field is switched and the temperature of an imaging system changes along with the ambient temperature, the cold reflection intensity also changes along with the change, at the moment, the traditional non-uniform correction algorithm cannot completely correct the cold reflection, and black spots still appear in an image.
Disclosure of Invention
The invention aims to solve the problem of black spots generated during imaging of the existing refrigeration type infrared imaging system, and provides a method for repairing cold reflection black spots of the infrared imaging system, which can repair the cold reflection problem in the infrared imaging system along with the change of the environmental temperature, reduce the optical design difficulty and the processing process requirement, reduce the influence of cold reflection on imaging and improve the image quality.
The technical scheme of the invention is as follows:
an environment temperature self-adaptive infrared imaging system cold reflection restoration method is characterized by comprising the following steps:
(1) when the infrared imaging system is tested before leaving factory, when the image has cold reflection black spots, the distribution parameter delta of each pixel of the image is calculatedi,jThe calculation method is as follows:
δi,j＝Xij—Xi,j
wherein, Xi,jOutputting raw data of any pixel for the detector, XijIs the mean value of the whole image;
simultaneously storing the cloth quantity delta in a memory of an infrared imaging systemi,jAnd the temperature T at this timeS；
(2) When the non-uniformity coefficient is calibrated before the infrared imaging system leaves the factory, the temperature T during calibration is recorded and stored in the memory of the infrared imaging system0；
(3) Before the infrared imaging system is used, when the infrared imaging system is powered on, the stored distribution parameter delta is read from the storage devicei,jAnd TS、T0Then non-uniformity correction is performed, recording and storing are performedTemperature Tc at the time of correction;
(4) in the using process of the infrared imaging system, non-uniform correction is carried out according to a preset period, and in each non-uniform correction period, non-uniform correction is carried out on each pixel of each frame of image and a correction result is stored;
meanwhile, the system temperature T at each time of non-uniformity correction is obtained, and the temperature correlation coefficient η is calculated according to the following formula:
η＝τ[(T-T0)]/[(Ts-T0)-(Tc-T0)/(Ts-T0)]
＝τ(T-Tc)/(Ts-T0)
η, representing the temperature dependency coefficient of the cold reflection black spot along with the temperature change;
τ: normalized cold reflection intensity-temperature gain coefficient;
t: the current temperature of the system;
T0: the temperature of the detector when leaving factory calibration;
ts: calculating distribution parameter delta before leaving factoryi,jThe temperature of (d);
tc: temperature at non-uniformity correction before use;
(5) cloth parameter delta obtained according to the step (1)i,jAnd (4) obtaining a temperature correlation coefficient η, and calculating a repair parameter delta of each pixel (i, j) of each frame image obtained according to the following formulaij：
Δi,j＝ηδi,j
(6) And (5) superposing the repair parameter delta obtained in the step (5) on the non-uniform correction result of each pixel of each frame image obtained in the step (4)i,jAnd finally, outputting the image after the cold reflection black spot is repaired.
The method simultaneously utilizes the correlation between the system temperature and the cold reflection intensity and the black spot coordinate position formed by cold reflection to generate cold reflection repair parameters which change along with the temperature and the coordinate position for each pixel in the infrared image in an image processing algorithm, thereby realizing the repair of the cold reflection problem in the infrared imaging system. The method can optimize the image display effect to a greater extent, particularly can effectively repair the phenomena of central black spots and edge lightening generated by cold reflection under the condition of high temperature of the system, does not introduce other display problems in the normal display process, is easier to realize compared with optical design and coating control methods, and solves the edge lightening problem caused by cold reflection.
Detailed Description
The principle of the method for repairing the cold reflection black spot of the infrared imaging system is as follows:
in the practical application of the refrigeration type infrared imaging system, the corrected image can be uniform by carrying out non-uniformity correction before use, but black spots formed by cold reflection become more and more obvious along with the rise of temperature in the use process. The position of the black spot formed by cold reflection in the image is fixed, and the obvious degree of the black spot has correlation with the system temperature, so that the coordinate position of the black spot and the intensity of the black spot can be recorded, and the black spot formed by cold reflection is compensated and repaired at different temperatures.
Setting the coordinate position of each pixel of each frame of image acquired by the detector as (i, j), and setting the original data of each pixel as Xi,jAfter completion of the non-uniformity correction, the image data is Yi,jAnd is recorded as:
Yi,j＝NUC(Xi,j) 1)
the cold reflection restoration algorithm of the invention is used, namely, a restoration parameter delta is superposed after the original output imagei,jIf the restored image data is Y', then:
Y’＝NUC(Xi,j)-Δi,j2)
in the present invention, the repair parameter Δi,jThe cold reflection black spot temperature-dependent image analysis system consists of two parts, wherein one part is a temperature dependence coefficient η for representing the change of the cold reflection black spot with temperature, and the other part is a distribution parameter delta for representing the relation between the intensity and the position of the cold reflection black spot in an imagei,j. Thus, the repair parameter Δi,jIs defined as:
Δi,j＝ηδi,j3)
distribution parameter deltai,jIs the mean value of the original response of each pixel and the whole imageThe difference of (a):
δi,j＝Xij-Xi,j(4)
temperature correlation coefficient η, current system temperature T in use, and temperature T when non-uniformity correction coefficient before factory calibration0The temperature at which the cold reflection black spot image is stored Ts, the temperature before use of non-uniformity correction Tc, and the cold reflection intensity are related to a temperature gain coefficient τ, expressed as:
η＝τ[(T-T0)]/[(Ts-T0)-(Tc-T0)/(Ts-T0)]
＝τ(T-Tc)/(Ts-T0)5)
wherein:
η, temperature dependence coefficient;
τ: normalized cold reflection intensity-temperature gain coefficient;
t: the current temperature of the system;
T0: the temperature of the detector when leaving factory calibration;
ts: storing the temperature of the cold reflection black spot pattern;
tc: temperature non-uniformity corrected before use.
The normalized cold reflection intensity-temperature gain coefficient τ is obtained by:
taking the gray level of the image of the central black spot area and the image of the corner highlight area as the difference, and marking as epsilon, the gray level difference epsilon of the central edge increases along with the rise of the temperature, and the gray level difference epsilon is expressed as:
ε＝f(T) 6)
the expression for f (T) can be found by polynomial fitting:
f(T)＝∑k＝0 nωkPk(T) 7)
the normalized cold reflection intensity-temperature gain coefficient is obtained by the following equation:
τ＝f(T)/f’(Ts) 8)
the invention uses second-order fitting in concrete engineering application, and the obtained normalized cold reflection intensity-temperature gain coefficient is as follows:
τ＝0.003612T-0.8273 9)
before the product is used, the invention finds that the cold reflection black spot is more obviousIn time, the distribution parameter δ is stored in advance for each pixeli,jThe temperature correlation coefficient is calculated η in real time according to the current temperature in the using process, and the cold reflection black spot is repaired in real time along with the change of the temperature, the definition of the temperature correlation coefficient η shows that the coefficient is smaller under the normal condition, the coefficient is 0 when the non-uniform correction is completed, and the coefficient is larger when the temperature is higher and the deviation correction temperature is farther, so that the repair parameters can be adjusted according to the ambient temperature to correct the cold reflection black spot of the fixed pattern in real time, and a better imaging effect is obtained.
The principle of the invention is analyzed, and the specific implementation steps of the invention are as follows:
(1) when the infrared imaging system is tested before leaving factory, when the image has cold reflection black spots, the distribution parameter delta of each pixel of the image is calculatedi,jSaid distribution parameter δi,jRepresenting the relation between the intensity and the position of the cold reflection black spots distributed in the image, wherein the value of the relation is the difference between the original response of each pixel and the mean value of the whole image; setting the coordinate position of each pixel as (i, j), and outputting the original data of any pixel as X by the detectori,jThe mean value of the whole image is Xij，δi,jCalculated according to equation 4) above as follows:
δi,j＝Xij—Xi,j；
storing the distribution parameter delta of each pixel of the cold reflection black spot image in the memory of the infrared imaging systemi,jAnd the temperature T at this timeS；
(2) When the non-uniformity coefficient is calibrated before the infrared imaging system leaves the factory, the temperature T during calibration is recorded and stored in the memory of the infrared imaging system0；
(3) When the infrared imaging system is powered on before being used, the stored distribution parameter delta is read from the storage devicei,jAnd TS、T0(ii) a When non-uniform correction is carried out after electrification, recording and storing the temperature Tc when the non-uniform correction is carried out;
(4) in the using process of the infrared imaging system, non-uniformity correction is carried out according to a preset period, and in each non-uniformity correction period, the non-uniformity correction result of each pixel of each frame of image is calculated according to the formula 1);
meanwhile, the system temperature T during each non-uniformity correction is obtained, and a temperature correlation coefficient η is calculated according to the formula 5);
η＝τ[(T-T0)]/[(Ts-T0)-(Tc-T0)/(Ts-T0)]
＝τ(T-Tc)/(Ts-T0)
wherein:
η, representing the temperature dependency coefficient of the cold reflection black spot along with the temperature change;
τ: normalized cold reflection intensity-temperature gain coefficient, related to the current temperature of the system, calculated as in equations 6) -9) above;
τ＝0.003612T-0.8273
t: the current temperature of the system;
T0: the temperature of the detector when leaving factory calibration;
ts: calculating distribution parameter delta before leaving factoryi,jThe temperature of (d);
tc: temperature at non-uniformity correction before use;
(5) cloth parameter delta obtained according to the step (1)i,jAnd (4) obtaining a temperature correlation coefficient η, and calculating a repair parameter delta of each pixel (i, j) of each frame of the obtained image according to the formula 3)ij；
Δi,j＝ηδi,j
(6) And (3) superposing the repair parameters delta obtained in the step (5) on the non-uniform correction result of each pixel of each frame image obtained in the step (4) according to the formula 2)i,jAnd finally, outputting the image after the cold reflection black spot is repaired.
Claims (1)
1. An environment temperature self-adaptive infrared imaging system cold reflection restoration method is characterized by comprising the following steps:
(1) when the infrared imaging system is tested before leaving factory, when the image has cold reflection black spots, each pixel of the image is countedCalculating the distribution parameter deltai,jThe calculation method is as follows:
δi,j＝Xij—Xi,j
wherein, Xi,jOutputting raw data of any pixel for the detector, XijIs the mean value of the whole image;
simultaneously storing the cloth quantity delta in a memory of an infrared imaging systemi,jAnd the temperature T at this timeS；
(2) When the non-uniformity coefficient is calibrated before the infrared imaging system leaves the factory, the temperature T during calibration is recorded and stored in the memory of the infrared imaging system0；
(3) Before the infrared imaging system is used, when the infrared imaging system is powered on, the stored distribution parameter delta is read from the storage devicei,jAnd TS、T0Then, carrying out non-uniform correction, and recording and storing the temperature Tc when carrying out non-uniform correction;
(4) in the using process of the infrared imaging system, non-uniform correction is carried out according to a preset period, and in each non-uniform correction period, non-uniform correction is carried out on each pixel of each frame of image and a correction result is stored;
meanwhile, the system temperature T at each time of non-uniformity correction is obtained, and the temperature correlation coefficient η is calculated according to the following formula:
η＝τ[(T-T0)]/[(TS-T0)-(Tc-T0)/(TS-T0)]
＝τ(T-Tc)/(TS-T0)
η, representing the temperature dependency coefficient of the cold reflection black spot along with the temperature change;
τ: normalized cold reflection intensity-temperature gain coefficient;
t: the current temperature of the system;
T0: the temperature of the detector when leaving factory calibration;
TS: calculating distribution parameter delta before leaving factoryi,jThe temperature of (d);
tc: temperature at non-uniformity correction before use;
(5) cloth parameter delta obtained according to the step (1)i,jAnd (4) obtaining a temperature correlation coefficient η, and calculating a repair parameter delta of each pixel (i, j) of each frame image obtained according to the following formulaij：
Δi,j＝ηδi,j
(6) And (5) superposing the repair parameter delta obtained in the step (5) on the non-uniform correction result of each pixel of each frame image obtained in the step (4)i,jAnd finally, outputting the image after the cold reflection black spot is repaired.
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| CN111968066A (en) * | 2020-08-27 | 2020-11-20 | 烟台艾睿光电科技有限公司 | Infrared image correction method, device and equipment and refrigeration infrared imaging system |
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| CN111968066A (en) * | 2020-08-27 | 2020-11-20 | 烟台艾睿光电科技有限公司 | Infrared image correction method, device and equipment and refrigeration infrared imaging system |
| CN111968066B (en) * | 2020-08-27 | 2023-01-10 | 烟台艾睿光电科技有限公司 | Infrared image correction method, device and equipment and refrigeration infrared imaging system |
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Application publication date: 20200626 |