CN110567584B - Method for detecting, extracting and correcting blind pixels of real-time infrared detector - Google Patents
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Abstract
The invention discloses a method for detecting, extracting and correcting blind pixels of a real-time infrared detector, which comprises the following steps of: 1) there is no sensing pixel point or pixel point with very low response rate; 2) comparing the response rate of the uniform heat radiation surface with the response rate of the normal pixel point pair, and obtaining pixel points with very large response rate change difference; 3) with the contrast of normal pixel point to even thermal radiation face response rate, the pixel that the difference is less than in the change of response rate detects respectively and draws, can use on uncooled infrared detector's core assembly, need not to interrupt product normal work to the extraction and the correction of infrared detector blind pixel in real time, effectively eliminates because of the blind pixel that strong impact, vibration in-process appear, promotes infrared detector's environmental suitability.
Description
Technical Field
The invention belongs to the technical field of infrared imaging, and particularly relates to a method for detecting, extracting and correcting blind pixels of a real-time infrared detector.
Background
Uncooled infrared detectors have been widely used in sights and other viewing instruments. The infrared sighting telescope can generate blind pixels in the processes of impact and vibration. The image blind pixels can seriously influence the use of products and are not beneficial to the identification of the target by an observer. Therefore, the uncooled infrared detector needs to be subjected to real-time blind pixel extraction and correction. In the conventional blind pixel extraction, firstly, under the condition of stopping the use of a product, the blind pixels need to be identified by human eyes, and the blind pixel coordinates are positioned through key operation or serial port software operation; the operation method is very complicated and seriously influences the real-time performance of the product. Therefore, it is necessary to intelligently extract and correct the blind pixels of the infrared detector in real time.
Disclosure of Invention
Aiming at the defects of the existing blind pixel extraction, the invention provides a real-time infrared detector blind pixel detection, extraction and correction method which is applied to a movement assembly of an uncooled infrared detector and can be used for detecting, extracting and correcting the infrared detector blind pixels in real time.
In order to achieve the purpose, the invention adopts the technical scheme that: the method for detecting, extracting and correcting the blind pixels of the real-time infrared detector is characterized by comprising the following steps of:
1) blind pixel extraction with very large response rate variation difference compared with the response rate of a normal pixel point pair on a uniform heat radiation surface
Outputting the infrared detector images line by line, and further utilizing a gradient matrix A = { -1, -1, -1; -1, 1, -1; -1, -1, -1} performing convolution operation to obtain a pixel value B, and if the absolute value of B is greater than the corresponding threshold value, determining that the pixel value B is a blind pixel which is compared with the response rate of the normal pixel point to the uniform heat radiation surface and has a very large response rate variation difference;
2) blind pixel extraction completely without any induction or with very low response rate
Acquiring multiple frames of different images through image acquisition, averaging the image gray value time domain of each pixel point of all the frame images, and if the value of a certain pixel point is smaller than a corresponding threshold value, judging that no induction exists or a blind pixel with a very low response rate exists completely;
3) blind pixel extraction with small difference of response rate variation compared with normal pixel point to uniform heat radiation surface response rate
The response of the blind pixel with smaller variation difference of response rate to the infrared image is close to the output of a normal pixel point, the blind pixel is treated as the heterogeneity of the infrared detector, the blind pixel has a certain response rate, but the homogeneity is poor, and the heterogeneity is utilized to repair the blind pixel; the normal image processing method for the infrared image non-uniformity repair utilizes a blocking piece correction technology, when the image non-uniformity is corrected, blind pixels are extracted in real time by utilizing a finally output image, when the blocking piece correction is carried out, the gray value output by the image is very uniform, an acquired blocking piece image X is taken, the average value of the gray values of the image is EX, if the absolute value of the difference between the gray value of a certain blind pixel and the EX is greater than a threshold value, the blind pixel is judged to be compared with the response rate of a normal pixel point to a uniform heat radiation surface, and the variation difference of the response rate is smaller;
4) blind pixel correction processing
Through the steps, all blind pixels appearing in the use process of an actual product can be extracted, and after the blind pixel coordinates are determined, the gray value of the blind pixel is replaced by the gray value of the adjacent non-blind pixel, so that the blind pixel correction processing is achieved.
The corresponding threshold value in the step 1) is 100; the corresponding threshold value in the step 2) is 3000; the threshold value in the step 3) is 50.
Collecting multiple frames of different images in the step 1), wherein the number of the different images is 20 or more than 20.
The image acquisition frame frequency of the infrared detector is 50Hz, and the original data acquired by the 14-bit AD of the image of the infrared detector is used as image processing original data.
Adopt above-mentioned technical scheme's beneficial effect: according to the method for detecting, extracting and correcting the blind pixels of the real-time infrared detector, the blind pixels are firstly classified into three types according to the characteristics of the blind pixels: 1) there is no sensing pixel point or pixel point with very low response rate; 2) comparing the response rate of the uniform heat radiation surface with the response rate of the normal pixel point pair, and obtaining pixel points with very large response rate change difference; 3) and comparing the response rate of the uniform heat radiation surface with the response rate of the normal pixel point pair, and obtaining the pixel point with smaller response rate change difference. The above three blind pixels, especially the first two blind pixels, seriously affect the infrared image observation and the target identification, and all need to be repaired in real time. How to extract three types of blind pixels of the infrared detector is the key point of the method, the method can extract and correct the blind pixels in real time, and the normal work of products does not need to be interrupted; the algorithm execution efficiency is high, more resources do not need to be occupied, and the implementation of platforms such as an FPGA and the like is facilitated; the misjudgment rate of the blind pixels is low. After the blind pixels are corrected, the target recognition rate can be effectively improved, and the blind pixels are prevented from being used as weak and small targets. The method is suitable for products of guns and cannon sights of non-refrigeration infrared detectors, and can automatically replace blind pixels of the infrared detectors in strong impact and vibration processes through an intelligent algorithm for detecting, extracting and correcting the blind pixels of the infrared image sensors.
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The following describes in further detail embodiments of the present invention with reference to the accompanying drawings.
FIG. 1: is an algorithm flow chart of the invention;
FIG. 2: completely without any sensing or blind pixel schematic diagram with very low response rate;
FIG. 3: blind pixel schematic diagrams with very large response rate change difference compared with the response rate of a normal pixel point to the uniform heat radiation surface;
FIG. 4: and comparing the response rate of the normal pixel point to the uniform heat radiation surface, and obtaining a blind pixel schematic diagram with small response rate change difference.
Detailed Description
As shown in fig. 1: the method for detecting, extracting and correcting the blind pixels of the real-time infrared detector is implemented according to the following steps:
1) the first step is as follows:
outputting the infrared detector images line by line, and further utilizing a gradient matrix A = { -1, -1, -1; -1, 1, -1; -1, -1, -1} convolution operation is carried out to obtain a pixel value B, if the absolute value of B is greater than corresponding 3000, the blind pixel is judged to be compared with the response rate of the normal pixel point to the uniform heat radiation surface, and the response rate change difference is very large, so that the blind pixel shown in fig. 3 is extracted. And replacing the gray value of the blind pixel by the gray value of the adjacent non-blind pixel.
2) The second step is that:
through image acquisition, 20 different images are acquired, the image gray value of each pixel point of the 20 images is averaged in the time domain, if a certain pixel point value is smaller than corresponding 100, blind pixels without any induction or with very low response rate are judged, and therefore the blind pixels shown in fig. 2 are extracted. And replacing the gray value of the blind pixel by the gray value of the adjacent non-blind pixel.
3) The third step:
the response of the blind pixel with smaller variation difference of the response rate to the infrared image is close to the output of a normal pixel point, and then the blind pixel can be treated as the nonuniformity of the infrared detector, namely, the blind pixel has a certain response rate, but the uniformity is poor, and the nonuniformity needs to be utilized for repairing. The normal image processing method for infrared image nonuniformity repair comprises the following steps: and (5) image calibration and baffle correction. Image calibration requires a calibration source (black body with uniform heat radiation), and the device cannot be found in actual product equipment. The invention utilizes the blocking sheet correction technology to extract the blind pixels in real time by utilizing the finally output image when the image is corrected in a non-uniform way. When the blocking piece is corrected, the gray value output by the image is very uniform, the collected blocking piece image X is taken, the average gray value of the image is EX, if the absolute value of the difference between the gray value of a certain blind pixel and EX is more than 50, the blind pixel is judged to be a blind pixel which is compared with the response rate of a normal pixel point to the uniform heat radiation surface, and the difference of the response rate change is small. Thereby extracting blind pixels as shown in fig. 4. And replacing the gray value of the blind pixel by the gray value of the adjacent non-blind pixel.
The method of the invention adopts a basic scheme for infrared detector hardware as follows: because the video frequency recognizable by human eyes is 25Hz, under the condition of not influencing the final output observation video frame rate, the advantage of processing time domain algorithm by combining infrared images is taken, and the hardware image acquisition frame frequency of the infrared movement is as follows: 50 Hz. The infrared movement adopts a blocking piece correction technology to correct and compensate the non-uniformity of the infrared image. The original data acquired by the 14-bit AD is used as the original data for image processing, so that the image details can be effectively reserved, and the analysis of the image blind metadata is facilitated.
Claims (4)
1. A method for detecting, extracting and correcting blind pixels of a real-time infrared detector is characterized by comprising the following steps:
1) blind pixel extraction with very large response rate variation difference compared with the response rate of a normal pixel point pair on a uniform heat radiation surface
Outputting the infrared detector images line by line, and further utilizing a gradient matrix A = { -1, -1, -1; -1, 1, -1; -1, -1, -1} performing convolution operation to obtain a pixel value B, and if the absolute value of B is greater than the corresponding threshold value, determining that the pixel value B is a blind pixel which is compared with the response rate of the normal pixel point to the uniform heat radiation surface and has a very large response rate variation difference;
2) blind pixel extraction completely without any induction or with very low response rate
Acquiring multiple frames of different images through image acquisition, averaging the image gray value time domain of each pixel point of all the frame images, and if the value of a certain pixel point is smaller than a corresponding threshold value, judging that no induction exists or a blind pixel with a very low response rate exists completely;
3) blind pixel extraction with small difference of response rate variation compared with normal pixel point to uniform heat radiation surface response rate
The response of the blind pixel with smaller variation difference of response rate to the infrared image is close to the output of a normal pixel point, the blind pixel is treated as the heterogeneity of the infrared detector, the blind pixel has a certain response rate, but the homogeneity is poor, and the heterogeneity is utilized to repair the blind pixel; the normal image processing method for the infrared image non-uniformity repair utilizes a blocking piece correction technology, when the image non-uniformity is corrected, blind pixels are extracted in real time by utilizing a finally output image, when the blocking piece correction is carried out, the gray value output by the image is very uniform, an acquired blocking piece image X is taken, the average value of the gray values of the image is EX, if the absolute value of the difference between the gray value of a certain blind pixel and the EX is greater than a threshold value, the blind pixel is judged to be compared with the response rate of a normal pixel point to a uniform heat radiation surface, and the variation difference of the response rate is smaller;
4) blind pixel correction processing
Through the steps, all blind pixels appearing in the use process of an actual product can be extracted, and after the blind pixel coordinates are determined, the gray value of the blind pixel is replaced by the gray value of the adjacent non-blind pixel, so that the blind pixel correction processing is achieved.
2. The method for extracting and correcting the blind pixel detection of the real-time infrared detector according to claim 1, characterized in that: the corresponding threshold value in the step 1) is 100; the corresponding threshold value in the step 2) is 3000; the threshold value in the step 3) is 50.
3. The method for extracting and correcting the blind pixel detection of the real-time infrared detector according to claim 1, characterized in that: collecting multiple frames of different images in the step 1), wherein the number of the different images is 20 or more than 20.
4. The method for extracting and correcting the blind pixel detection of the real-time infrared detector according to claim 1, characterized in that: the image acquisition frame frequency of the infrared detector is 50Hz, and the original data acquired by the 14-bit AD of the image of the infrared detector is used as image processing original data.
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