KR100966689B1 - A method and a apparatus of compensation defect pixel for digital camera - Google Patents

Abstract

The present invention does not deteriorate image quality by supplementing a defect pixel image signal of a digital camera with a median filter-processed peripheral pixel, and includes a photographing unit configured to capture an image with a plurality of pixels and to output the digital signal; A buffer unit which records, stores and outputs the digital image signal of the photographing unit; A color separator which separates and outputs an image signal applied from the buffer into a red cyan color; A high frequency detector for analyzing high frequency components of each pixel applied from the color separator and neighboring neighboring pixels, and detecting and outputting a defective pixel whose pixel is larger than a high frequency value of the neighboring pixels; A median filter unit for outputting a median value obtained by performing a median filtering process on the high frequency value of the neighboring pixel of the defective pixel applied from the high frequency detector; Characterized in that it comprises a correction unit for correcting the defect pixel of the digital image signal applied from the buffer unit to the median value applied from the median filter unit, and also to store the image signal captured by the digital camera in the buffer unit process; A high frequency process of separating the image signals photographed in the process for each color and analyzing high frequency component values of all pixels; A median process of performing a median filter process on the pixel at which the average absolute difference between each pixel value and the neighboring pixel is greater than a corresponding threshold value by the above process; And a correction process for correcting the defective pixel image signal value of the process to the image signal value of the median-filtered pixel and recording and storing the image signal in a corresponding standard and format.

Description

Defective pixel compensation device and method of digital camera {A METHOD AND A APPARATUS OF COMPENSATION DEFECT PIXEL FOR DIGITAL CAMERA}

1 is a functional block diagram of a defect pixel complement of a digital camera according to the prior art;

2 is a functional block diagram of a defective pixel complement of a digital camera according to the present invention;

3 is a flowchart of a method for compensating for a defective pixel of a digital camera according to the present invention;

4 is an explanatory diagram of defect pixel determination according to the present invention;

5 is an explanatory diagram of a median filter process according to the present invention.

          ** Explanation of symbols on the main parts of the drawing **

100: recording unit 110: buffer unit 120: color separation unit

130: high frequency detector 132: first detector 134: second detector

Reference numeral 136: third detector 140: median filter 142: first median

144: second median unit 146: third median unit 150: correction unit

160: control unit 170: image storage unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication terminal, and more particularly, to an apparatus and method for compensating for a defective pixel of a digital camera for compensating a value of a defect pixel generated during photographing by median filtering.

Digital cameras (DICA: DIGITAL CAMERA) do not use a film to record and store IMAGE signals that are chemically reacted to an incoming optical signal, and do not use a C-MOS (COMPLEMENTARY METAL OXIDE SEMICONDUCTOR) or CCD ( A camera for converting the photographed optical image signal into an electrical image signal and recording and storing the image in the memory using an image pickup device of CHARGE COUPLED DEVICE.

Recently, communication equipment has been developed from a communication method using an audio signal to a multimedia communication method including a data communication method using text and symbols and a video communication method using a video signal. In particular, the spread of mobile communication terminal (MS: MOBILE STATION) (MS) with built-in camera function for video signal recording and multimedia communication is rapidly spreading. In the digital camera, C- MOS or CCD is used.

The imaging devices C-MOS and CCD convert an optical signal input to the pixel PIXEL into an electrical signal and output the electrical signal. As the number of pixels having a smaller size per unit area is configured, the image quality of the video signal is better. The development of technology for increasing the degree of integration of pixels per unit area continues.

However, as the degree of integration of the imaging device C-MOS or CCD increases as described above, the occurrence of defects or defects of pixels or pixels in the production process is difficult to be avoided by the current technology, and the C-MOS and CCD as described above are used. In the process of manufacturing a digital camera there is a problem that the number of the defective pixel is further increased.

Therefore, there is a need to develop a method of effectively compensating for the defective pixels naturally occurring in the manufacturing and manufacturing process of the C-MOS and CCD devices of the digital camera.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A defect pixel compensating method of a digital camera according to the prior art will be described with reference to the accompanying drawings.

Attached to explain the prior art, Figure 1 is a functional block diagram of a defect pixel complement of a digital camera according to the prior art.

As shown in FIG. 1, a conventional digital camera defect pixel compensator includes: a photographing unit 10 which converts an image signal input as an optical signal into an electrical signal, and comprises a C-MOS or CCD element; LOW PASS FILTER (LPF) 20 for filtering defect pixels from the image signal photographed by the photographing unit 10; A controller 30 for digitally processing the video signal filtered by the low frequency filter 20 and converting the video signal into a video signal having a predetermined format and standard, and controlling and monitoring each functional unit of the digital camera; The video storage unit 40 stores a digital video signal applied from the control unit 30.

Hereinafter, the operation of the conventional digital camera defect pixel complementary device having the above configuration will be described in detail with reference to the accompanying drawings.

First, the photographing unit 10 photographs a subject and outputs an image signal. At this time, the C-MOS or CCD device constituting the photographing unit 10 converts the input optical image signal into an electrical image signal and outputs the converted electrical image signal. However, since the C-MOS or CCD device is manufactured to increase the degree of integration of the pixels PIXEL in the manufacturing process, some crystal pixels are generated among hundreds of thousands or millions of pixels. Therefore, as the integration degree of the pixel increases in the C-MOS or CCD device, the defect pixel increases.

The development of reducing defects generated in the production process of the C-MOS or CCD devices is in progress. However, in the process of manufacturing the photographing unit 10 using the high pixel integration device as described above, defect pixels are again generated. Occurs. The defective pixels generated as described above deteriorate the image quality of the digital video signal.
Therefore, in order to reduce the image quality deterioration as described above, the image signal output from the image capturing unit 10 is filtered by the low frequency filter (LPF) 20 to deteriorate the image signal input from the image capturing unit.

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In other words, in order to conceal the defect of the degradation caused by the small number of defect pixels, the image signal generated from the normal multiple pixels is degraded to a certain level. That is, since the overall quality of the image is lowered, the deterioration problem caused by the defective pixel is compensated for.

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The video signal uniformly degraded by the low frequency filter 20 as described above is digitally processed by the control unit 30 and then converted into a video signal of a predetermined format and standard, and the image signal is allocated to an allocated area of the image storage unit 40. It is stored and output if necessary to be displayed on the display or printed through a printing apparatus.

Therefore, the conventional technique as described above is a method of forcibly degrading a high quality image signal photographed by a large number of normal pixels in order to reduce the defect of degradation caused by the small number of defective pixels of the photographing unit 10, so that the image quality is high. There is a problem to bear the falling point.

It is an object of the present invention to provide an apparatus and method for compensating for a defective pixel of a digital camera capable of compensating for a defect in an image signal generated from a few defective pixels of a digital camera.

In order to achieve the above object, a drawback pixel complement device of a digital camera according to the present invention includes a photographing unit for photographing an image with an imaging device having a plurality of pixels; A color separator for separating the photographed video signal into a red cyan color; A high frequency detector for detecting defect pixels by analyzing high frequency components of each pixel of the image signal applied from the color separator and neighboring pixels; A median filter unit which medians the peripheral pixel values of the defective pixel detected by the high frequency detector and outputs a median value; And a correction unit for correcting the defect pixel of the photographed digital image signal with a median value output from the median filter unit.
In addition, a method for compensating for a defective pixel of a digital camera according to the present invention devised to achieve the above object includes: photographing a subject with a camera; Separating the photographed video signal into three primary colors; Detecting a defective pixel by analyzing a high frequency component of each pixel and a high frequency component of a peripheral pixel of the image signal separated into three primary colors; Outputting a median value by performing a median filter process on the peripheral pixel values of the detected defective pixel; And correcting the defect pixel of the detected video signal with a median value output from the median filter unit.

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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings.

FIG. 2 is a block diagram of a defect pixel compensating device for a digital camera according to the present invention, and FIG. 3 is a flowchart illustrating a method for compensating for a defective pixel of a digital camera according to the present invention. 4 is an explanatory diagram of defect pixel determination according to the present invention, and FIG. 5 is an explanatory diagram of a median filter process according to the present invention.

As shown in FIG. 2, a defect pixel compensating apparatus for a digital camera according to the present invention includes a photographing unit 100 including a C-MOS imaging device or a CDS imaging device, and the photographing unit ( A buffer unit 110 for storing the digital image signal photographed at 100 and a color separation unit for separating the image signal applied from the buffer unit 110 into red-green-blue (R, G, B) colors and outputting the respective colors ( 120 and a high frequency detector 130 for detecting a defective pixel by analyzing high frequency components of each pixel and neighboring neighboring pixels in the image signal separated by the color separator 120; The median filter unit 140 performs a median filter unit 140 which performs median filtering on the defect pixels detected by the high frequency detector 130, and a defect pixel of the digital image signal applied from the buffer unit 110. A correction unit 150 for correcting the median value outputted from the control unit, a control unit 160 for converting the digital image signal corrected by the correction unit 150 into a predetermined format and standard, and outputting the converted digital image signal. And an image storage unit 170 for storing the output digital image signal.
The high frequency detector 130 receives the red (R: RED) image signal separated by the color separator 120 and detects a defective pixel larger than a high threshold value of a neighboring pixel by more than a threshold value. ; A second detector 134 receiving a green (G) image signal output from the color separator 120 and detecting and outputting a defective pixel larger than a high threshold value of a neighboring pixel; The third detector 136 is configured to receive a blue (B: BLUE) image signal separated by the color separator 120 and detect and output a defective pixel larger than a threshold value of a neighboring pixel.
The median filter 140 is a median filter 142 that outputs a median value by performing a median filter on a high frequency value of a neighboring pixel instead of a defective pixel value detected by the first detector 132 of the high frequency detector 130. ); A second median unit 144 for outputting a median value by performing a median filtering process on a high frequency value of a neighboring pixel instead of the defect pixel value detected by the second detection unit 134; Instead of the defect pixel value detected by the third detector 136, the third median unit 146 outputs a median value by performing a median filter process on a high frequency value of a neighboring pixel.

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Hereinafter, with reference to the accompanying drawings a defect pixel complement device of a digital camera according to the present invention configured as described above will be described in detail.

First, the photographing unit 100 photographs a subject by an imaging device including a C-MOS or a CCD, and the photographed digital image signal is recorded in the buffer unit 110. The buffer unit 100 outputs the recorded digital image signal to the color separation unit 120 and the correction unit 150 under the control of the controller 160.

The color separator 120 separates an image signal captured by all the pixels PIXEL in the photographing unit 100 into three primary colors, that is, red (R), green (G), and blue (B). After output to the high frequency detection unit 130.

The high frequency detector 130 detects a high frequency component value included in an image signal of each pixel to be input and compares it with an average value of neighboring pixels. As a result of the comparison, when the detected high frequency component value is larger than a predetermined threshold value, the pixel is judged to be defective pixels.

That is, since normal pixels are similar to video signals captured by neighboring neighboring pixels, the averaged high frequency values are similar to each other, and thus the detected high frequency component values are smaller than a predetermined threshold value. However, since the DEFECT PIXEL does not capture an image signal or captures an abnormal image signal, an absolute value processing of an average high frequency value and a difference value of neighboring pixels is detected to be larger than the predetermined threshold value. .
4 shows an example of determining a defective pixel according to the present invention.

Referring to FIG. 4, when it is assumed that the X pixel is a defective pixel, the high frequency detector 130 may set the high frequency value of the X pixel to be the high frequency of the neighboring pixels 1, 2, 3, 4, 5, 6, 7, 8. The difference value is calculated by comparing with the component mean value, and it is determined whether the absolute value of the calculated difference value is larger than the threshold value Y as in the following equation.

(Equation)

| X-(1 + 2 + 3 + 4 + 5 + 6 + 7 + 8) | > Y

only; X is a pixel for analyzing whether a pixel is defective.

(1 + 2 + 3 + 4 + 5 + 6 + 7 + 8) is an average value of the high frequency components of pixels 1 to 8.

Y is a threshold set arbitrarily by experiment.

The red (R) image signal separated by the color separation unit 120 is input to the first detection unit 132 to analyze the corresponding high frequency component value of each pixel, and thus is a pixel having a greater absolute difference than the threshold value. Defective pixel is detected. The green (G) image signal is input by the second detector 134 to analyze a corresponding high frequency component value of each pixel, and thus detects a defective pixel that is a pixel having an absolute difference larger than the threshold, and blue (B). The video signal is input by the third detector 136 to analyze corresponding high frequency component values of each pixel, thereby detecting defect pixels that are pixels having an absolute difference larger than the threshold. The detected defect pixels are respectively output to the first median filter unit 142, the second median filter unit 144, and the third median filter unit 146 of the median filter unit 140, respectively.

The first to third median filter units 142, 144, and 146 of the median filter unit 140 may generate a median of high frequency values detected from a neighboring main station of the defect pixel detected by the high frequency detector 130. Filter and select the median value to output.
5 is a diagram illustrating a median filter process according to the present invention.
As shown in FIG. 5, the median filter unit 140 sorts the high frequency component values of pixels 1 to 9 including, for example, pixels 5 which are defect pixels, such as ascending or descending order. An intermediate value of the high frequency component values of the remaining pixels except for the high frequency component values of the defective pixels is analyzed. As a result of the analysis, when the high frequency component value 5 is determined as an intermediate value, the corresponding image signal value of the pixel 8 having the high frequency component value of 5 is set as a median value and output to the median value.

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The correction unit 150 compensates by replacing or replacing the defect pixel value of the image signal applied from the buffer unit 110 with the median value applied from the median filter unit 140.

That is, the correction unit 150 is a median value applied from the first median filter unit 142, the second median filter unit 144, and the third median filter unit 146 of the median filter unit 140, respectively. And the defect pixel information detected by the high frequency detector 130 to replace or replace the image signal of the defect pixel position of the image signal applied from the buffer unit 110 with the image signal of the pixel by the median value. Correct it.

Accordingly, the present invention outputs a normal video signal by eliminating the noise caused by the defective pixel and replacing or replacing it with an intermediate value of neighboring pixels without degrading the video signal captured by the photographing unit 100 as a whole.

In the method of compensating for a defective pixel of a digital camera according to the present invention, an image is captured by a digital camera, and the captured image signal is stored in the buffer unit 110. In order to separate the photographed video signal by color and to analyze high-frequency component values of all pixels, the present invention divides the video signal into red (R), green (G), and blue (B), respectively, to separate the high-frequency of all pixels. Analyze component values.

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As a result of the analysis, a defect pixel having an average absolute difference value between each pixel value and a neighboring pixel is larger than a corresponding threshold value is detected, and then the median filter is processed on the defect pixel. That is, according to the present invention, it is determined whether each pixel value and the neighbor absolute pixel mean absolute difference value are defective pixels having a value larger than the corresponding threshold value. The equation " | X-(average value of eight pixels around) | ; Value of the inspection pixel, Y; predetermined threshold value ". As a result of the determination, when the average absolute difference value is a defective pixel having a value larger than the threshold value, the neighboring pixel value of the corresponding pixel is sequentially arranged to select the intermediate value.
Thereafter, the defect pixel image signal value is corrected by the median filter process to correct the image signal value of the selected normal pixel, converted into a corresponding standard and format, and recorded and stored in the image storage unit.
Hereinafter, a method for compensating for a defective pixel of a digital camera according to the present invention will be described in more detail with reference to FIG. 3.

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When photographing an image signal using a digital camera (S100), the photographed image signal is stored in the buffer unit 110 (S110), and the stored image signal is red (R) green in the color separation unit 120. (G) The light is separated into three primary colors of blue (B), and the high frequency component values of all the pixels of the separated image signal are checked and analyzed (S120).

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The high frequency component values of all the pixels checked and analyzed as described above are illustrated in, for example, FIG. 4, and a defect pixel (DEFECT PIXEL) is determined using the following equation (S130).

(Equation)

| X-(average value of eight pixels around) | > Y

only; X is the analysis pixel, the average value of the surrounding eight pixels is (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8) / 8, Y is a threshold that is arbitrarily set by the experiment.

If the specific pixel value is determined to be a defective pixel having an absolute difference value greater than a predetermined threshold value by the above equation, the median filter unit 140 processes the pixel. That is, the median filter is performed by including eight pixels around the neighborhood, and the median value is selected and set as the median value.

In other words, as shown in FIG. 5, the median filter unit 140 sequentially processes the high-frequency component values of pixels 1 to 9 in the vicinity of the vicinity including the pixel 5 which is determined to be a defective pixel. The pixels corresponding to the intermediate value are selected from the high frequency component values of the remaining pixels except for the high frequency component value of the pixel 5 which is determined to be a defective pixel.

The pixel selected as described above is, for example, pixel 8 having a high frequency component value of 5, and the image signal value of pixel 8 is set as a median value and corrected by the image signal value of pixel 5, which is the defect pixel. do.

Since the value of the defective pixel is a pixel that operates substantially abnormally, it has a value of a video signal having a large difference from white or black or a peripheral value, and can be classified as a noise when viewed as a whole video signal.

In order to remove the noise, median filter processing is performed on the video signal value of the neighboring pixels, and the video signal value corresponding to the median value is selected as the median value and corrected to the defect pixel value classified as the noise. Eliminates noise without compromising image quality.

The present invention having the above-described configuration corrects the noise caused by the defect pixel of the digital camera using the CMOS or the CD image pickup device to the image signal value of the median-processed pixel, thereby effectively removing the noise without degrading the overall image quality. There is an industrial use effect.

In addition, since noise by the image pickup device is removed and image quality of a video signal is not deteriorated, there is a convenient effect in improving performance and reliability of a digital camera.

Claims (13)

A photographing unit which photographs an image with an imaging device of a plurality of pixels; A color separator for separating the photographed video signal into a red cyan color; A high frequency detector for analyzing the high frequency components of each pixel and neighboring neighboring pixels of the image signal applied from the color separation unit and detecting the corresponding pixels as defect pixels when the high frequency component of each pixel is larger than the high frequency components of the neighboring pixels; A median filter unit which medians the peripheral pixel values of the defective pixel detected by the high frequency detector and outputs a median value; And a correction unit for correcting the defect pixel of the photographed digital image signal with a median value output from the median filter unit. delete The method of claim 1, wherein the photographing unit, Device for complementing the defective pixel of the digital camera, characterized in that consisting of CMOS image pickup device or CD image pickup device. The method of claim 1, wherein the high frequency detection unit A first detector which receives a red image signal separated by the color separator and detects a defect pixel larger than a high frequency component of a neighboring pixel by a threshold value or more; A second detector which receives a green image signal separated by the color separator and detects and outputs a defective pixel larger than a high frequency component of a neighboring pixel by a threshold value; And a third detector which receives the blue image signal separated by the color separator and detects and outputs a defective pixel larger than a high frequency component of a neighboring pixel by a threshold value. The method of claim 1, wherein the median filter unit A first median unit which medians the high frequency values of the neighboring pixels and outputs the median value instead of the defect pixel value detected by the first detection unit of the high frequency detector; A second median unit which medians a high frequency value by surrounding pixels and outputs a median value instead of the defect pixel value detected by the second detection unit of the high frequency detector; And a third median unit for outputting a median value by performing a median filter process on the high frequency value of the surrounding pixels instead of the defect pixel value detected by the third detection unit of the high frequency detector. The method of claim 1, wherein the correction unit, The defect pixel complement of a digital camera, characterized in that for correcting a median value applied from a median filter unit with a corresponding defect pixel value. Photographing a subject with a camera; Separating the photographed video signal into three primary colors; Analyzing the high frequency component of each pixel and the high frequency component of the peripheral pixel of the video signal separated into the three primary colors to obtain the difference between the average of the high frequency component value of each pixel and the high frequency component value of the peripheral pixel, and the absolute value of the difference Detecting pixels larger than a threshold as defect pixels; Outputting a median value by performing a median filter process on the peripheral pixel values of the detected defective pixel; And correcting the defect pixel of the detected image signal by the median value output from the median filter unit. delete delete delete The method of claim 7, wherein the correction process, And correcting the video signal of the defective pixel by replacing the video signal with the median filtered video signal. delete 8. The median value of claim 7, wherein the median value is And an intermediate value obtained by sequentially arranging high-frequency component values of neighboring pixels of the detected defective pixel.

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