CN115379199A - Bad point detection method for image sensor - Google Patents
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- CN115379199A CN115379199A CN202210820290.9A CN202210820290A CN115379199A CN 115379199 A CN115379199 A CN 115379199A CN 202210820290 A CN202210820290 A CN 202210820290A CN 115379199 A CN115379199 A CN 115379199A
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Abstract
The invention relates to a method for detecting a dead pixel of an image sensor, belonging to the technical field of image processing. The detection method comprises the following steps: 1. partitioning the image; 2. calculating the average value blockMean of each divided image block, performing expansion calculation on the blockMean, comparing a first judgment value and a second judgment value obtained by calculation with a threshold value, and judging a dead pixel; 3. and traversing all the images and detecting all the dead pixels. The method realizes the accurate detection of the dead pixel by performing the block mean expansion calculation on the average value of the image block and comparing the calculated average value with a set threshold value; the invention does not need to record and store the position information of the dead pixel in advance, does not need a storage space to store the position information, and can detect the dead pixel occurring in the using process of the product.
Description
Technical Field
The invention relates to a method for detecting a dead pixel of an image sensor, belonging to the technical field of image processing.
Background
The imaging process of the camera is the process of digitizing the optical signal. Light firstly passes through a lens to reach a photosensitive element, namely an image sensor (CCD, CMOS and the like), light signals are converted into digital signals, and the digital signals are transmitted to equipment such as a camera after being subjected to subsequent signal processing by a special digital signal processing chip. Generally, an image sensor includes a plurality of photosensitive elements, each of which corresponds to a pixel in an image output from the image sensor.
Due to the manufacturing process, the transportation or the storage mode, some photosensitive units of the image sensor are damaged and cannot normally sense light, and pixel points corresponding to the photosensitive units which cannot normally sense light in the image are called dead pixels.
The dead pixel mainly comprises the following three types: 1. dark-spot dead pixels, which are mainly formed as a result of the photosensitive cells being completely damaged, are represented as a dark spot in the image; 2. the bright spot dead pixel is mainly formed by direct short circuit of a photosensitive diode and a power supply in the photosensitive unit, so that the voltage of the photosensitive unit is always at a high level and is represented as a bright spot in an image; 3. the response of the photosensitive unit to the light intensity is different from the normal response of the peripheral photosensitive units due to the manufacturing deviation, the unstable dead pixel is represented in the image that the pixel value of the photosensitive unit is higher or lower than the pixel value of the peripheral pixel point, and the influence of the dead pixel on the image changes along with the change of the external environment. Accordingly, it is known that the dead pixel has a certain influence on the image quality of the image, and therefore, the dead pixel must be handled.
Disclosure of Invention
In order to solve the above technical problems, the present invention provides a method for detecting a dead pixel of an image sensor, which has the following specific technical scheme:
an image sensor dead pixel detection method comprises the following steps:
step 1: and (3) calculating an average value: dividing the selected image into a plurality of image blocks, and calculating the average value blockMean of each image block;
step 2: and (3) dead pixel detection: setting threshold values a, b and c, wherein the value range of the threshold value a is 280-320, the value range of the threshold value b is 0.6-0.8, the value range of the threshold value c is 2-3, and when the blockMean is greater than a, calculating any pixel in the image block as shown in formula (1)
T0 = abs(1 – pdata/blockMean) （1）
When the blockMean is less than or equal to a, calculating any pixel in the image block as shown in formula (2)
T1 = pdata/blockMean （2）
Wherein T0 is a first judgment value, T1 is a second judgment value, pdata is the value of any pixel in the image block; when T0 is more than or equal to b or T1 is more than or equal to c, the pixel point is a dead pixel;
and step 3: image traversal: and completely traversing all image blocks of the image division to find out all dead pixel. The mean value of the image block is blockMean, when the width and the height of the image block are 20x20, 400 pixel values exist in the image block, the 400 pixel values are added, and then the sum is divided by 400, so that the mean value blockMean of the image block is obtained.
Further, the selected image is divided into a plurality of 20 × 20 image blocks in step 1.
Further, in the step 2, the value of the threshold a is 300, the value of the threshold b is 0.7, and the value of the threshold c is 2.5.pdata is divided by the mean of the image block in which it is located, and the result is compared with a threshold to determine whether it is a dead pixel.
The invention has the beneficial effects that:
the method realizes the precise detection of the dead pixel by the expansion calculation of the block mean value of the image block and the comparison with the set threshold value; the invention does not need to record and store the position information of the dead pixel in advance, does not need a storage space to store the position information, and can detect the dead pixel in the using process of the product.
Drawings
Figure 1 is a schematic flow diagram of the present invention,
figure 2 is a schematic diagram I of the invention of a pre-detection dead pixel,
figure 3 is a graph of dead pixel labeling after the detection of figure 2,
figure 4 is a schematic diagram II of the invention of a pre-detection dead pixel,
fig. 5 is a graph of dead pixel labeling after the detection of fig. 4.
Detailed Description
The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams each illustrating the basic structure of the present invention only in a schematic manner, and thus show only the constitution related to the present invention.
At present, the dead pixel is generally detected in advance and stored, the dead pixel is searched in the collected image according to the position information of the dead pixel, and the interpolation processing is carried out on the dead pixel by using a preset interpolation algorithm. As shown in fig. 1, a method for detecting bad pixels of an image sensor according to the present invention is disclosed. Firstly, averagely dividing a selected image into a plurality of 20x20 image blocks, and calculating the average value blockMean of each image block. Wherein, the width and height of the image block are 20 × 20, there are 400 pixel values in the image block, and the 400 pixel values are added and then divided by 400 to obtain the mean blockMean of the image block. Then, the thresholds a, b, and c are set according to experience and requirements. Wherein the value of the threshold value a is 300, the value of the threshold value b is 0.7, and the value of the threshold value c is 2.5. When the blockMean is more than a, calculating any pixel in the image block as shown in formula (1)
T0 = abs(1 – pdata/blockMean) （1）
When the blockMean is less than or equal to a, calculating any pixel in the image block as shown in formula (2)
T1 = pdata/blockMean （2）
Wherein T0 is a first judgment value, T1 is a second judgment value, pdata is the value of any pixel in the image block; when T0 ≧ b or T1 ≧ c, this pixel is identified as a dead pixel, as shown in FIGS. 2-5. Wherein pdata is divided by the mean value of the image block in which pdata is located, and the obtained result is compared with a threshold value to determine whether the pixel is a dead pixel. And finally, traversing all image blocks of the image, and detecting all dead pixels of the image so as to correct the subsequent dead pixels.
In light of the foregoing description of the preferred embodiment of the present invention, many modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.
Claims (3)
1. An image sensor dead pixel detection method is characterized by comprising the following steps:
step 1: and (3) calculating an average value: dividing the selected image into a plurality of image blocks, and calculating the average value blockMean of each image block;
step 2: and (3) dead pixel detection: setting threshold values a, b and c, wherein the value range of the threshold value a is 280-320, the value range of the threshold value b is 0.6-0.8, the value range of the threshold value c is 2-3, and when the blockMean is greater than a, calculating any pixel in the image block as shown in formula (1)
T0 = abs(1 – pdata/blockMean) （1）
When the blockMean is less than or equal to a, calculating any pixel in the image block as shown in formula (2)
T1 = pdata/blockMean （2）
Wherein T0 is a first judgment value, T1 is a second judgment value, pdata is the value of any pixel in the image block; when T0 is more than or equal to b or T1 is more than or equal to c, the pixel point is a dead pixel;
and 3, step 3: image traversal: and completely traversing all image blocks of the image division to find out all dead pixel.
2. The method of claim 1, wherein: the selected image is divided into a plurality of 20x20 image blocks in step 1.
3. The method of claim 1, wherein the step of detecting the bad pixel comprises: in the step 2, the value of the threshold a is 300, the value of the threshold b is 0.7, and the value of the threshold c is 2.5.
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| CN202210820290.9A CN115379199A (en) | 2022-07-13 | 2022-07-13 | Bad point detection method for image sensor |
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Citations (7)
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| US20120086829A1 (en) * | 2010-10-07 | 2012-04-12 | Hohjoh Daisuke | Image processing unit, image processing method, and image processing program |
| CN105163114A (en) * | 2015-08-21 | 2015-12-16 | 深圳创维－Rgb电子有限公司 | Method and system for detecting screen dead pixel based on camera |
| JP2019219273A (en) * | 2018-06-20 | 2019-12-26 | 株式会社日本マイクロニクス | Image generation device and image generation method |
| CN110830795A (en) * | 2020-01-09 | 2020-02-21 | 武汉精立电子技术有限公司 | Image sensor dead pixel detection method and device and electronic equipment |
| CN113497934A (en) * | 2021-05-17 | 2021-10-12 | 南京威派视半导体技术有限公司 | Dead pixel detection and correction method for image sensor |
| CN113873229A (en) * | 2021-09-26 | 2021-12-31 | 江西盛泰精密光学有限公司 | Image dead pixel detection method, system and device |
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2022
- 2022-07-13 CN CN202210820290.9A patent/CN115379199A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1595957A (en) * | 2004-06-22 | 2005-03-16 | 东软飞利浦医疗设备系统有限责任公司 | Method for determining automatic detection threshold of bad pixel of medical image |
| US20120086829A1 (en) * | 2010-10-07 | 2012-04-12 | Hohjoh Daisuke | Image processing unit, image processing method, and image processing program |
| CN105163114A (en) * | 2015-08-21 | 2015-12-16 | 深圳创维－Rgb电子有限公司 | Method and system for detecting screen dead pixel based on camera |
| JP2019219273A (en) * | 2018-06-20 | 2019-12-26 | 株式会社日本マイクロニクス | Image generation device and image generation method |
| CN110830795A (en) * | 2020-01-09 | 2020-02-21 | 武汉精立电子技术有限公司 | Image sensor dead pixel detection method and device and electronic equipment |
| CN113497934A (en) * | 2021-05-17 | 2021-10-12 | 南京威派视半导体技术有限公司 | Dead pixel detection and correction method for image sensor |
| CN113873229A (en) * | 2021-09-26 | 2021-12-31 | 江西盛泰精密光学有限公司 | Image dead pixel detection method, system and device |
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