CN113497934A - Dead pixel detection and correction method for image sensor - Google Patents

Dead pixel detection and correction method for image sensor Download PDF

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Publication number
CN113497934A
CN113497934A CN202110536809.6A CN202110536809A CN113497934A CN 113497934 A CN113497934 A CN 113497934A CN 202110536809 A CN202110536809 A CN 202110536809A CN 113497934 A CN113497934 A CN 113497934A
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pixel
dead
pixel values
formula
values
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陈烨
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Nanjing Weipaishi Semiconductor Technology Co ltd
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Nanjing Weipaishi Semiconductor Technology Co ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N17/00—Diagnosis, testing or measuring for television systems or their details
    • H04N17/002—Diagnosis, testing or measuring for television systems or their details for television cameras
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
    • H04N25/60—Noise processing, e.g. detecting, correcting, reducing or removing noise
    • H04N25/68—Noise processing, e.g. detecting, correcting, reducing or removing noise applied to defects

Abstract

The invention relates to a method for detecting and correcting dead pixels of an image sensor, which comprises the following steps: 1. sorting the pixel values, for each central pixel in the image
Figure 383301DEST_PATH_IMAGE001
The method comprises the steps of sorting pixel values in the field, 2, carrying out weighted average processing on the pixel values, carrying out weighted average on the sorted pixel values through a matrix A, 3, calculating an absolute difference value, 4, setting a threshold value for detecting dead pixels, 5, judging dead pixel detection, and 6, correcting the dead pixels. The invention does not need to record and store the position information of the dead pixel in advance, does not need to store the position information in a storage space, can detect and correct the dead pixel which appears in the using process of the product at the same time, meets the transformation and the requirement of different scenes, and has high accuracy of dead pixel detection and high efficiency of dead pixel correction.

Description

Dead pixel detection and correction method for image sensor
Technical Field
The invention relates to a method for detecting and correcting dead pixels of an image sensor, and belongs 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 light-sensing units, each corresponding 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: firstly, dark-point dead pixels are formed mainly because the photosensitive units are completely damaged, and are represented as dark points in an image; secondly, lightening a dead pixel, wherein the 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 point in an image; and thirdly, unstable dead pixels, wherein 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 pixel value of the photosensitive unit is higher or lower than that of the peripheral pixel points in the image, and the influence of the dead pixels on the image is changed 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 and correcting a dead pixel of an image sensor, which has the following specific technical scheme:
a method for detecting and correcting dead pixels of an image sensor comprises the following steps:
step 1: sorting the pixel values, for each central pixel in the image
Figure 809498DEST_PATH_IMAGE001
The pixel values in the neighborhood are sorted, as shown in equation (1),
Figure 581145DEST_PATH_IMAGE002
（1）
in the formula
Figure 407150DEST_PATH_IMAGE003
And wherein the unexpanded element is
Figure 86393DEST_PATH_IMAGE001
Pixel values within a neighborhood;
step 2: weighted average processing is carried out on the pixel values, weighted average is carried out on the pixel values which are sorted in the step 1 through a matrix A, the pixel values are made into result values result (xi, yi) of the central pixel, as shown in a formula (2),
Figure 173298DEST_PATH_IMAGE004
（2）
wherein K is the sum of all elements in the matrix A;
and step 3: calculating the absolute difference value
Figure 194474DEST_PATH_IMAGE001
And (xi, yi) as shown in equation (3)
Figure 429147DEST_PATH_IMAGE005
（3）；
And 4, step 4: setting a threshold value, setting a threshold value T for detecting a dead pixel, as shown in formula (4)
Figure 849764DEST_PATH_IMAGE006
（4）
In the formula
Figure 400962DEST_PATH_IMAGE007
Represents the mean of the image I;
and 5: the dead pixel detection and judgment are carried out, the absolute difference diff (yi, xi) is compared with a threshold value T, when the diff (yi, xi) is larger than or equal to T, the pixel point is judged to be a dead pixel and is corrected, otherwise, the pixel point is a normal pixel point;
step 6: and (5) correcting the dead pixel, namely detecting and judging the dead pixel in the step (5), correcting the dead pixel to ensure that the pixel value of the dead pixel is changed into the result value of the central pixel, as shown in a formula (5)
Figure 983253DEST_PATH_IMAGE008
（5）
In the formula
Figure 501959DEST_PATH_IMAGE009
Representing the pixel value after dead pixel correction.
Further, when the pixel values in the step 1 are sorted, the central pixel is sorted
Figure 273737DEST_PATH_IMAGE001
Is ordered by the pixel values in the 3x3 neighborhood as shown in
Figure 69655DEST_PATH_IMAGE010
In the formula
Figure 213060DEST_PATH_IMAGE011
，
Figure 828849DEST_PATH_IMAGE012
，
Figure 669897DEST_PATH_IMAGE013
，
Figure 648218DEST_PATH_IMAGE014
，
Figure 447677DEST_PATH_IMAGE001
，
Figure 81921DEST_PATH_IMAGE015
，
Figure 444769DEST_PATH_IMAGE016
，
Figure 825066DEST_PATH_IMAGE017
And
Figure 185640DEST_PATH_IMAGE018
is that
Figure 900656DEST_PATH_IMAGE001
Pixel values in the 3x3 neighborhood.
Further, the matrix A in the step 2 is a 3x3 matrix,
Figure 806208DEST_PATH_IMAGE019
，K=16。
the invention has the beneficial effects that:
the invention does not need to record and store the position information of the dead pixel in advance, does not need to store the position information in a storage space, can detect and correct the dead pixel which appears in the using process of the product at the same time, meets the transformation and the requirement of different scenes, and has high accuracy of dead pixel detection and high efficiency of dead pixel correction.
Drawings
Figure 1 is a schematic flow diagram of the present invention,
figure 2 is an image I containing a dead pixel,
figure 3 is the image of figure 2 after dead-spot correction,
figure 4 is an image II containing a dead spot,
figure 5 is the image of figure 4 after dead-spot correction,
figure 6 is an image III containing a dead spot,
fig. 7 is an image of fig. 6 after dead pixel correction.
Detailed Description
The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic views illustrating only the basic structure of the present invention in a schematic manner, and thus show only the constitution related to the present invention.
As shown in fig. 1, a method for detecting and correcting a dead pixel of an image sensor according to the present invention is disclosed. First, the pixel values are sorted, with each center pixel in the image
Figure 696804DEST_PATH_IMAGE001
The pixel values in the neighborhood are sorted, as shown in equation (1),
Figure 87334DEST_PATH_IMAGE002
（1）
in the formula
Figure 243640DEST_PATH_IMAGE003
And wherein the unexpanded element is
Figure 620395DEST_PATH_IMAGE001
Pixel values within a neighborhood; at this time, the center pixel is selected
Figure 490131DEST_PATH_IMAGE001
Is ordered by the pixel values in the 3x3 neighborhood as shown in
Figure 5557DEST_PATH_IMAGE010
In the formula
Figure 570530DEST_PATH_IMAGE011
，
Figure 141189DEST_PATH_IMAGE012
，
Figure 819426DEST_PATH_IMAGE013
，
Figure 427125DEST_PATH_IMAGE014
，
Figure 604028DEST_PATH_IMAGE001
，
Figure 588165DEST_PATH_IMAGE015
，
Figure 120908DEST_PATH_IMAGE016
，
Figure 289722DEST_PATH_IMAGE017
And
Figure 563708DEST_PATH_IMAGE018
is that
Figure 961323DEST_PATH_IMAGE001
Pixel values in the 3x3 neighborhood. Secondly, the pixel values are weighted-averaged, and the sorted pixel values are weighted-averaged by the matrix A to form the result value result (xi, yi) of the center pixel, as shown in formula (2)
Figure 597840DEST_PATH_IMAGE020
（2）
Where K is the sum of all the elements in matrix A, matrix A is a 3x3 matrix,
Figure 547342DEST_PATH_IMAGE019
and K = 16. Then, the absolute difference is calculated, and
Figure 715149DEST_PATH_IMAGE001
and (xi, yi) as shown in equation (3)
Figure 775509DEST_PATH_IMAGE005
(3). Subsequently, a threshold value is set, and a threshold value T for detecting a dead pixel is set as shown in equation (4)
Figure 532112DEST_PATH_IMAGE006
（4）
In the formula
Figure 527881DEST_PATH_IMAGE007
Representing the mean of the image I. And (4) bad pixel detection and judgment, comparing the absolute difference diff (yi, xi) with a threshold value T, judging the pixel point to be a bad pixel and correcting the pixel point when the diff (yi, xi) is more than or equal to T, otherwise, judging the pixel point to be a normal pixel point. Finally, bad point correction, in step 5, bad point is detected and judged, and the bad point is corrected, so that the pixel value of the bad point is changed into that of the central pixelThe resulting value, as shown in equation (5)
Figure 42039DEST_PATH_IMAGE008
（5）
In the formula
Figure 233986DEST_PATH_IMAGE009
Representing the pixel value after dead pixel correction. The method for correcting the dead pixel generally comprises the steps of detecting and storing position information of the dead pixel in advance, searching the dead pixel in an acquired image according to the position information of the dead pixel, and carrying out interpolation processing on the dead pixel by using a preset interpolation algorithm. As shown in fig. 2, fig. 3, fig. 4, fig. 5 and fig. 6, by the method for detecting and correcting dead pixel of image sensor of the present invention, the dead pixel appearing in fig. 2 is corrected as shown in fig. 3, the dead pixel appearing in fig. 4 is corrected as shown in fig. 5, and the dead pixel corrected in fig. 6 is shown in fig. 7.
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. A method for detecting and correcting dead pixels of an image sensor is characterized by comprising the following steps: the method comprises the following steps:
step 1: sorting the pixel values, for each central pixel in the image
Figure 826138DEST_PATH_IMAGE001
The pixel values in the neighborhood are sorted, as shown in equation (1),
Figure 775640DEST_PATH_IMAGE002
（1）
in the formula
Figure 661556DEST_PATH_IMAGE003
And wherein the unexpanded element is
Figure 987495DEST_PATH_IMAGE001
Pixel values within a neighborhood;
step 2: weighted average processing is carried out on the pixel values, weighted average is carried out on the pixel values which are sorted in the step 1 through a matrix A, the pixel values are made into result values result (xi, yi) of the central pixel, as shown in a formula (2),
Figure 947361DEST_PATH_IMAGE004
（2）
wherein K is the sum of all elements in the matrix A;
and step 3: calculating the absolute difference value
Figure 943130DEST_PATH_IMAGE001
And (xi, yi) as shown in equation (3)
Figure 457288DEST_PATH_IMAGE005
（3）；
And 4, step 4: setting a threshold value, setting a threshold value T for detecting a dead pixel, as shown in formula (4)
Figure 445973DEST_PATH_IMAGE006
（4）
In the formula
Figure 463607DEST_PATH_IMAGE007
Represents the mean of the image I;
and 5: the dead pixel detection and judgment are carried out, the absolute difference diff (yi, xi) is compared with a threshold value T, when the diff (yi, xi) is larger than or equal to T, the pixel point is judged to be a dead pixel and is corrected, otherwise, the pixel point is a normal pixel point;
step 6: and (5) correcting the dead pixel, namely detecting and judging the dead pixel in the step (5), correcting the dead pixel to ensure that the pixel value of the dead pixel is changed into the result value of the central pixel, as shown in a formula (5)
Figure 99119DEST_PATH_IMAGE008
（5）
In the formula
Figure 959628DEST_PATH_IMAGE009
Representing the pixel value after dead pixel correction.
2. The method of claim 1, wherein the method further comprises: when the pixel values in the step 1 are sorted, the central pixel is sorted
Figure 627369DEST_PATH_IMAGE001
Is ordered by the pixel values in the 3x3 neighborhood as shown in
Figure 640456DEST_PATH_IMAGE010
In the formula
Figure 696137DEST_PATH_IMAGE011
，
Figure 653728DEST_PATH_IMAGE012
，
Figure 527DEST_PATH_IMAGE013
，
Figure 992754DEST_PATH_IMAGE014
，
Figure 750494DEST_PATH_IMAGE001
，
Figure 726541DEST_PATH_IMAGE015
，
Figure 611451DEST_PATH_IMAGE016
，
Figure 786081DEST_PATH_IMAGE017
And
Figure 855668DEST_PATH_IMAGE018
is that
Figure 663218DEST_PATH_IMAGE001
Pixel values in the 3x3 neighborhood.
3. The method of claim 1, wherein the method further comprises: the matrix a in step 2 is a 3x3 matrix,
Figure 476453DEST_PATH_IMAGE019
，K=16。
CN202110536809.6A 2021-05-17 2021-05-17 Dead pixel detection and correction method for image sensor Pending CN113497934A (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006180210A (en) * 2004-12-22 2006-07-06 Sony Corp Imaging apparatus and method, and program
US20130120609A1 (en) * 2011-11-11 2013-05-16 Olympus Imaging Corporation Imaging device and control method for imaging device
CN103475828A (en) * 2013-10-10 2013-12-25 旗瀚科技有限公司 Method for rectifying missing pixels and image sensor
CN106815821A (en) * 2017-01-23 2017-06-09 上海兴芯微电子科技有限公司 The denoising method and device of near-infrared image
CN107016669A (en) * 2017-03-27 2017-08-04 福州瑞芯微电子股份有限公司 A kind of dead pixel points of images detection method and device
CN107613229A (en) * 2017-09-30 2018-01-19 杭州雄迈集成电路技术有限公司 A kind of dead pixels of image sensor surveys means for correcting and method

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006180210A (en) * 2004-12-22 2006-07-06 Sony Corp Imaging apparatus and method, and program
US20130120609A1 (en) * 2011-11-11 2013-05-16 Olympus Imaging Corporation Imaging device and control method for imaging device
CN103475828A (en) * 2013-10-10 2013-12-25 旗瀚科技有限公司 Method for rectifying missing pixels and image sensor
CN106815821A (en) * 2017-01-23 2017-06-09 上海兴芯微电子科技有限公司 The denoising method and device of near-infrared image
CN107016669A (en) * 2017-03-27 2017-08-04 福州瑞芯微电子股份有限公司 A kind of dead pixel points of images detection method and device
CN107613229A (en) * 2017-09-30 2018-01-19 杭州雄迈集成电路技术有限公司 A kind of dead pixels of image sensor surveys means for correcting and method

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