KR100860307B1 - Correction Device of Bad Pixel and Method thereof - Google Patents

Abstract

The present invention relates to a defective pixel correction device and a method for detecting and correcting defective pixels by receiving three lines of an image signal simultaneously and comparing them with each other.

In accordance with another aspect of the present invention, there is provided an apparatus for correcting a defective pixel, comprising: a first memory configured to store a first line of an image signal applied from the outside; A second memory for storing a second line of the video signal; The first and second lines of the image signal and the third line of the image signal stored in the first and second memories are simultaneously applied to the pixel values of the intermediate pixels of the second line and the first to third lines. Defective pixels to detect defective pixels by comparing a first or second operation value obtained by subtracting or adding a preset margin value to a minimum or maximum pixel value of neighboring pixels except the middle pixel of the second line Detection unit; And a defective pixel correcting unit that corrects by substituting the first or second calculation value into the defective pixel when the defective pixel is detected by the defective pixel detecting unit.

Bad pixel, correction, line, margin, max, min

Description

Bad pixel correction device and its method {Correction Device of Bad Pixel and Method

1 is a block diagram showing a defective pixel correction device according to the prior art.

2 is a flowchart sequentially showing a method for correcting a defective pixel according to the related art.

Figure 3 is a block diagram schematically showing a defective pixel correction device according to the present invention.

4 is a block diagram showing three lines of a video signal according to the present invention;

5 is a flowchart sequentially showing a method for correcting a defective pixel according to the present invention.

<Description of Symbols for Major Parts of Drawings>

310: first memory 320: second memory

330: Defective pixel detection unit 340: Defective pixel correction unit

a ~ i: Pixel of video signal

The present invention relates to an apparatus for correcting a defective pixel and a method thereof, and more particularly, to calculate defective pixels by simultaneously receiving three lines of an image signal and comparing them with each other, and adding and subtracting margin values to minimum or maximum peripheral pixel values. The present invention relates to a defective pixel correction device and a method for correcting defective pixels.

In general, an image sensor is an apparatus for taking an image by using a property in which a semiconductor reacts to light. That is, the device senses the brightness and wavelength of different light emitted from each subject and reads them as an electric value. It is the role of the image sensor to make this electric value a signal processable level.

These image sensor products have been commercialized in various applications according to the development of semiconductor technology, digital signal processor (DSP), and storage device technology. In particular, the digital camera has been developed with 10 million pixels, and the camera technology for mobile phones is also close to the technology of digital cameras. Due to technical shortages, the low resolution CIF (Common Intermediate Format) and VGA (Video Graphics Array) ) Image sensors are used a lot, but the development of high resolution image sensors is progressing due to the recent increase in the number of pixels.

In low resolution image sensors, the line width of the circuit is relatively small and is not affected by dust or noise. On the other hand, in a high resolution image sensor, the circuit width is minute and is influenced by dust or noise. Therefore, the probability that a specific pixel falls into an inoperable state increases. There are many difficulties in making uniformity with respect to.

The inoperable pixel is divided into a white defect or a black defect and is called a bad pixel as it is clearly distinguished from the surrounding pixels.

The image sensor including the defective pixel is subject to defect determination, but may not be determined according to the method of improving the defect. In particular, there is always a possibility that a defective pixel may occur in a mega image sensor, and if all of the defective pixels are judged to be defective, methods for processing the same are being studied.

Then, the defective pixel correction apparatus according to the prior art will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing a defective pixel correction apparatus according to the prior art.

First, as shown in FIG. 1, the conventional defective pixel correction device includes a defective pixel detection unit 110 and a defective pixel correction unit 120.

Here, the defective pixel detection unit 110 may display one line including three pixels G1, G2, and G3 among the image signals applied from the outside, that is, the image signals captured by the image sensor connected to the defective pixel correction apparatus. Each pixel of the line is sequentially applied and stored, and the stored first pixel G1 and the second pixel G2 are compared with each other to determine whether or not a defective pixel is present.

In this case, the comparison method includes a first pixel value of a first pixel G1 that is a peripheral pixel of the second pixel G2 and a second pixel value that is a pixel value of the second pixel G2 positioned in the middle of the line. The defective pixel is detected by determining whether the first operation value obtained by subtracting the pixel value is larger or smaller than the preset threshold.

If the first operation value is smaller than the threshold value, the first operation value is compared with the pixel value of the third pixel G3 to determine whether the second pixel G2 is defective. If larger than the threshold value, the second pixel G2 determines that the defective pixel is a defective pixel, and transmits it to the defective pixel correction unit 120 to correct it.

In addition, the comparison method with the pixel value of the third pixel G3 for judging the second pixel G2 is similar to the comparison method with the first pixel G1. It is determined whether the second operation value obtained by subtracting the three pixel values is larger or smaller than the threshold value.

If the second operation value is smaller than the threshold value, the second pixel G2 is determined to be normal data instead of defective pixels, and is immediately output without correction. If the second operation value is larger than the threshold value, the second pixel is output. Determining that G2 is a defective pixel and transferring it to the defective pixel correction unit 120 to correct it.

The defective pixel correction unit 120 corrects and outputs a defective pixel detected by the defective pixel detection unit 110. If the first or second operation value has a value larger than the threshold value and the second pixel G2 is detected as a defective pixel, the first and third pixels which are the peripheral pixels of the second pixel G2. After calculating an average of pixel values of the pixels G1 and G3, the calculated average value is substituted into the pixel value of the second pixel G2.

Accordingly, the second pixel value G2, which is the bad pixel, is set to a pixel value close to the first and third pixel values that are replaced by the average value of the first and third pixel values. Can be corrected by the data G2 '.

Hereinafter, a method of correcting defective pixels using a conventional defective pixel correcting apparatus will be described in detail with reference to FIG. 2.

2 is a flowchart sequentially illustrating a method for correcting a defective pixel according to the prior art.

First, as shown in FIG. 2, the first pixel value and the pixel of the second pixel, which are pixel values of the first pixel of the applied line, are applied by receiving one line consisting of three pixels among the image signals applied from the outside. The value second pixel value and the pixel value of the third pixel are stored, respectively (S201, S202, S203).

Then, in order to detect whether the second pixel is a defective pixel, a first threshold value obtained by subtracting the first pixel value from the second pixel value is compared with a preset threshold value (S204).

In this case, when the first operation value is larger than the threshold value, the second pixel is determined to be a bad pixel, and the average value of the pixel values of the first and second pixels, which are peripheral pixels of the second pixel, is calculated to calculate the average value. Substitute the pixel value of the second pixel (S205).

If the first operation value is less than the threshold value, a second operation value is calculated by subtracting a third pixel value from the second pixel value to determine whether the second pixel is defective. The calculated second operation value is compared with the threshold (S206).

If the second operation value is smaller than the threshold in step S206, the second pixel is determined to be a normal pixel instead of a defective pixel, and is output as it is without correction (S207).

If the second operation value is larger than the threshold value, the second pixel is determined to be a bad pixel, and the average value of the pixel values of the first and second pixels, which are peripheral pixels of the second pixel, is calculated to calculate the average value. Is substituted into the pixel value of the second pixel to correct the second pixel, which is a defective pixel (S205).

However, since the defective pixel correcting apparatus and method receive one line composed of three pixels from an externally applied image signal and compare the pixel values of the lines to detect the defective pixel, all of the lines are defective. If the pixel is recognized as normal data and immediately outputted without correction, there was a problem that the defective pixel may be included in the image as it is and output.

In addition, when the second pixel of the image signal is a pixel representing the boundary region of the image, it is determined that the defective pixel is corrected to an average value of neighboring pixels, so that the boundary region to be clearly expressed is blurred and reliability is low. there was.

Accordingly, an object of the present invention is to solve the above problems, and an object of the present invention is to simultaneously receive three lines of an image signal, compare them with each other, detect defective pixels, and add or subtract margin values to minimum or maximum peripheral pixel values. The present invention relates to a defective pixel correcting apparatus and a method for correcting the defective pixels by substituting arithmetic values.

In accordance with an aspect of the present invention, there is provided an apparatus for correcting a defective pixel, comprising: a first memory configured to store a first line of an image signal applied from the outside; A second memory for storing a second line of the video signal; The first and second lines of the image signal and the third line of the image signal stored in the first and second memories are simultaneously applied to the pixel values of the intermediate pixels of the second line and the first to third lines. Defective pixels to detect defective pixels by comparing a first or second operation value obtained by subtracting or adding a preset margin value to a minimum or maximum pixel value of neighboring pixels except the middle pixel of the second line Detection unit; And a defective pixel correcting unit that corrects by substituting the first or second calculation value into the defective pixel when the defective pixel is detected by the defective pixel detecting unit.

In the defective pixel correction device according to an embodiment of the present invention, the defective pixel detection unit may be configured such that the pixel value of an intermediate pixel of the second line among the first, second, and third lines is smaller than the first calculated value. The intermediate pixel of the second line is detected as a defective pixel.

In the defective pixel correction device according to the present invention, the defective pixel detection unit is further configured to generate the pixel when the pixel value of the intermediate pixel of the second line among the first, second, and third lines is larger than the second operation value. The intermediate pixel of the second line is detected as a defective pixel.

In the defective pixel correcting apparatus according to the present invention, the defective pixel processing unit is configured to convert the first calculated value to the second calculated value when the pixel value of the intermediate pixel of the second line is smaller than the first calculated value. The correction is performed by substituting the pixel value of the intermediate pixel.

On the other hand, in the defective pixel correction apparatus according to the present invention, when the pixel value of the intermediate pixel of the second line is larger than the second operation value, the second operation value is set to the pixel value of the intermediate pixel of the second line. Correct by substituting. In this case, the image signal is an image signal captured by the image sensor, wherein the first, second and third lines are each composed of three pixels.

In addition, a method for correcting a defective pixel according to the present invention for achieving the above object comprises the steps of: a) storing a first line of an image signal applied from the outside; b) storing a second line of the video signal; c) simultaneously applying the stored first and second lines and a third line of the image signal; d) determining whether a pixel value of an intermediate pixel of the second line is smaller than a first operation value obtained by subtracting a preset margin value to a minimum pixel value among pixel values of the pixel other than this; e) when the pixel value of the intermediate pixel of the second line is greater than the first operation value in step d), the pixel value of the intermediate pixel of the second line is equal to the maximum pixel value of the pixel value except the pixel; Determining whether the margin value is greater than the second calculated value; And f) if the pixel value of the intermediate pixel of the second line is larger than the second operation value in step e), substitute the second operation value with the pixel value of the intermediate pixel of the second line to correct defective pixels. It comprises; a.

Further, in the defective pixel correction method of the present invention, when the pixel value of the intermediate pixel of the second line determined in step d) is smaller than the first operation value, the first operation value is intermediate to the second line. The defective pixel is corrected by substituting the pixel value of the pixel.

In the defective pixel correction method of the present invention, when the pixel value of the intermediate pixel of the second line determined in step e) is smaller than a second operation value, the intermediate pixel of the second line is determined as a normal pixel. It is characterized in that the output without correction.

In the defective pixel correction method of the present invention, the video signal is an image signal captured by an image sensor, and the first, second, and third lines each include three pixels.

The above objects, features, and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, whereby those skilled in the art may easily implement the technical idea of the present invention. There will be.

In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

Hereinafter, the defective pixel correction apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

3 is a block diagram schematically showing an apparatus for compensating for defective pixels according to the present invention, and FIG. 4 is a block diagram showing three lines of an image signal according to the present invention.

First, as illustrated in FIG. 3, the defective pixel correcting apparatus according to the present invention includes a first memory 310, a second memory 320, a defective pixel detection unit 330, and a defective pixel correction unit 340. The image signal applied from the outside is divided into first, second, and third lines each consisting of three pixels, and the pixel value of the intermediate pixel of the second line among the three lines is the pixel value of the peripheral pixel thereof. The controller determines whether the pixel is a bad pixel, and corrects the output if the middle pixel of the second line is a bad pixel. In this case, the image signal applied from the outside is an image signal captured by an image sensor (not shown) connected to the defective pixel correction apparatus.

In the first line of the image signal, pixel values of three pixels forming the first line are stored in the second memory 320. Then, when the second line of the image signal is applied, the pixel value stored in the second memory 320 is stored in the first memory 310 and each pixel value of the second line is stored in the second memory. Stored at 320.

After the first line and the second line are stored in the first memory 310 and the second memory 320, the third line is applied and simultaneously stored in the first and second memories 310 and 320. First and second lines are applied to the defective pixel detection unit 330.

The defective pixel detection unit 330 forms the applied first to third lines in one block to detect defective pixels that may be included in the defective pixels.

That is, as shown in Fig. 4, when the first line is a, b, c, the second line is d, e, f, and the third line is g, h, i, they are 3x3 blocks. After that, it is detected whether the e pixel, which is the middle pixel of the second line, is a defective pixel.

In the process of detecting whether the e pixel is a bad pixel, first, a minimum pixel value of each pixel value of a, b, c, d, f, g, h, and i pixels, which are peripheral pixels of the e pixel, is detected. Then, the first operation value is calculated by subtracting a margin set in advance to the minimum pixel value. In this case, the margin value is a threshold value for determining a defective pixel and may be set by a user.

The pixel value of the e pixel is smaller than the first operation value by comparing the pixel value of the e pixel, which is the intermediate pixel of the second line, with the calculated first operation value, to determine the e pixel as a defective pixel.

If the pixel value of the e pixel is larger than the first operation value, the e pixel is judged, and each of the pixels a, b, c, d, f, g, h and i which are the peripheral pixels of the e pixel. The maximum pixel value of the pixel values is detected. Then, a second operation value is calculated by adding the margin value to the maximum pixel value.

Then, the pixel value of the e pixel, which is the intermediate pixel of the second line, is compared with the calculated second operation value, and when the pixel value of the e pixel is smaller than the second operation value, the e pixel is not a bad pixel. If it is determined that it is not corrected, it is output as it is.

If the pixel value of the e pixel is larger than the second operation value, the e pixel is determined to be a bad pixel, and the e pixel is transmitted to the bad pixel correcting unit 340.

Meanwhile, as another embodiment of the process of determining whether the defective pixel detection unit 330 is the defective pixel, that is, peripheral pixels excluding the e pixel, that is, a, b, c, d, f, g, h and i When no defective pixel is detected in any of the pixels, the defective pixel may be detected by performing the above-described defective pixel determination process except for the pixel having the maximum pixel value and the minimum pixel value among the surrounding pixels.

Accordingly, the defective pixel detection unit 330 receives the first, second and third lines each consisting of three pixels, and compares the intermediate pixel value of the second line, which is an intermediate pixel, with the pixel value of the peripheral pixel. By determining whether the defective pixel is a pixel value of the pixel a, c, d, f, g, i or a, b, c, g, h, i In the case of a boundary area indicating a boundary of an image having a large difference, it can be judged as normal data instead of a defective pixel. There is an advantage that it is possible to accurately detect defective pixels.

The defective pixel correcting unit 340 receives the first to third lines of the image signal applied from the defective pixel detection unit 330, and when the e pixel that is the middle pixel of the second line of the image signal is not a defective pixel, This is immediately output without correction. If the e pixel is a defective pixel, the correction is performed to output the corrected e '.

In this case, the method of correcting the e pixel determined as the defective pixel by the defective pixel correcting unit 340 is a peripheral pixel of the e pixel if the defective pixel is smaller than this compared with the first operation value. By substituting the first operation value obtained by subtracting the first margin value to the minimum pixel value among the a, b, c, d, f, g, h, and i pixels as the first correction value, the defective pixel e pixel is substituted. The defective pixel is corrected to e 'and output.

If the pixel e is larger than the second operation value and is a defective pixel, the maximum pixel value among the pixels of a, b, c, d, f, g, h, and i, which are neighboring pixels of the e pixel, is determined. The defective pixel is corrected to e 'and outputted by substituting the second correction value obtained by adding the second calculated value to the pixel e, which is the defective pixel.

Meanwhile, instead of the first and second correction values, an average of pixel values of the a, b, c, d, f, g, h, and i pixels, which are peripheral pixels of the e pixel, is calculated and used as the correction value. By substituting, the pixel e as the defective pixel can be corrected.

Accordingly, the defective pixel correcting apparatus according to the present invention receives an image signal simultaneously to the first, second, and third lines each consisting of three pixels, and receives the intermediate pixel values of the second line, which is the intermediate pixel, of the peripheral pixels. By comparing the first operation value obtained by subtracting the margin value to the minimum pixel value among the values, and comparing the second operation value obtained by adding the margin value to the maximum pixel value among the peripheral pixel values, it is determined whether or not the defective pixel is There is an advantage that the boundary region and the defective pixel can be accurately detected than the conventional defective pixel correcting device which judges the defective pixel only by the line.

Hereinafter, a defective pixel correction method according to the present invention will be described in detail with reference to the accompanying drawings.

5 is a flowchart sequentially showing a method for correcting a defective pixel according to the present invention.

As illustrated in FIG. 5, the defective pixel correcting method according to the present invention receives a first line consisting of three pixels as an image signal applied from the outside and stores the applied first line (S410). In this case, the image signal applied from the outside is an image signal captured by the image sensor.

After storing the first line, the second line of the image signal is received and stored (S420).

The stored first and second lines and the third line of the image signal are simultaneously applied (S430).

The pixel value of the intermediate pixel of the second line among the first, second and third lines of the applied image signal is preset to the pixel value of the pixel having the minimum pixel value among the pixels other than the intermediate pixel of the second line. The margin value is compared with the first calculated value subtracted (S440).

If the pixel value of the intermediate pixel of the second line is smaller than the first operation value in step S440, the intermediate pixel of the second line is determined as a defective pixel.

At this time, when it is determined that the intermediate pixel of the second line is a defective pixel, the first operation value obtained by subtracting the margin value to the minimum pixel value of the neighboring pixels is used as a first correction value of the intermediate pixel of the second line. By substituting the pixel value, the intermediate pixel of the second line, which is a defective pixel, is corrected (S445).

If the intermediate pixel value of the second line is greater than the first operation value in step S440, the maximum pixel value of the peripheral pixel value is determined based on the maximum pixel value of the peripheral pixel value to determine whether or not the pixel of the intermediate pixel of the second line is defective. The second operation value obtained by adding the margin value is compared with the pixel value of the intermediate pixel of the second line (S450).

If the pixel value of the intermediate pixel of the second line is smaller than the second operation value as a result of the comparison in step S450, the pixel value of the intermediate pixel of the second line is determined to be a normal pixel instead of a defective pixel and is not corrected. Output

On the other hand, when the pixel value of the intermediate pixel of the second line is larger than the second operation value as a result of the comparison in step S450, the intermediate pixel of the second line is determined to be a defective pixel.

If it is determined that the intermediate pixel of the second line is a bad pixel, the second operation value obtained by adding the margin value to the pixel value of the pixel having the largest pixel value among the peripheral pixels is used as the second correction value. By substituting the pixel value of the intermediate pixel of the line, the intermediate pixel of the second line, which is a defective pixel, is corrected.

Preferred embodiments of the present invention described above are disclosed for the purpose of illustration, and various substitutions, modifications, and changes within the scope without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains. It will be appreciated that such substitutions, changes, and the like should be considered to be within the scope of the following claims.

As described above, the defective pixel correction device and the method according to the present invention are applied to the first, second and third lines composed of three pixels at the same time, the middle of the second line which is an intermediate pixel thereof. The pixel value is compared with the first operation value obtained by subtracting the margin value to the minimum pixel value among the peripheral pixel values, and the second operation value obtained by adding the margin value to the maximum pixel value of the peripheral pixel values to determine whether or not the defective pixel is present. By determining, the image is improved by accurately detecting the boundary area and the defective pixel, thereby improving the reliability of the defective pixel correcting device.

Claims (12)

A first memory for storing a first line of an image signal applied from the outside; A second memory for storing a second line of the video signal; The first and second lines of the image signal and the third line of the image signal stored in the first and second memories are simultaneously applied to the pixel values of the intermediate pixels of the second line and the first to third lines. Defective pixels to detect defective pixels by comparing a first or second operation value obtained by subtracting or adding a preset margin value to a minimum or maximum pixel value of neighboring pixels except the middle pixel of the second line Detection unit; And A defective pixel correction unit for correcting by substituting the first or second calculation value into the defective pixel when the defective pixel detection unit detects the defective pixel; Defective pixel correction device comprising a. The method of claim 1, The defective pixel detection unit, If the pixel value of the intermediate pixel of the second line among the first, second and third lines is smaller than the first operation value, the defective pixel correction of the intermediate pixel of the second line is detected as a defective pixel. Device. The method of claim 1, The defective pixel detection unit, If the pixel value of the intermediate pixel of the second line among the first, second and third lines is larger than the second operation value, the defective pixel correction of the intermediate pixel of the second line is detected as a defective pixel. Device. The method of claim 1, The defective pixel processing unit, And when the pixel value of the intermediate pixel of the second line is smaller than the first operation value, correcting the first computed value by substituting the pixel value of the intermediate pixel of the second line. The method of claim 1, And correcting the second operation value by substituting the pixel value of the intermediate pixel of the second line when the pixel value of the intermediate pixel of the second line is larger than the second operation value. The method of claim 1, And the video signal is an image signal picked up by an image sensor. The method of claim 1, And the first, second and third lines are each composed of three pixels. a) storing a first line of an image signal applied from the outside; b) storing a second line of the video signal; c) simultaneously applying the stored first and second lines and a third line of the image signal; d) determining whether a pixel value of an intermediate pixel of the second line is smaller than a first operation value obtained by subtracting a preset margin value to a minimum pixel value among pixel values of the pixel other than this; e) when the pixel value of the intermediate pixel of the second line is greater than the first operation value in step d), the pixel value of the intermediate pixel of the second line is equal to the maximum pixel value of the pixel value of the pixel except for the above; Determining whether the margin value is greater than the second calculated value; And f) correcting the defective pixel by substituting the second operation value with the pixel value of the intermediate pixel of the second line when the pixel value of the intermediate pixel of the second line is larger than the second operation value in step e). step; Defective pixel correction method comprising a. The method of claim 8, If the pixel value of the intermediate pixel of the second line determined in step d) is smaller than the first operation value, the defective pixel is corrected by substituting the first operation value with the pixel value of the intermediate pixel of the second line. Defective pixel correction method, characterized in that. The method of claim 8, If the pixel value of the intermediate pixel of the second line determined in step e) is smaller than the second operation value, the defective pixel of the second line is determined as a normal pixel and output without being corrected. Correction method. The method of claim 8, And the video signal is an image signal captured by an image sensor. The method of claim 8, And the first, second, and third lines each comprise three pixels.

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