KR100566571B1 - Method and apparatus for auto compensating image sensor lens shading - Google Patents

Abstract

The present invention relates to a method and apparatus for correcting a lens shading phenomenon in an image sensor, and in particular, a method for automatically correcting a lens shading phenomenon in an image sensor capable of maintaining a quality of a raw image by automatically correcting a reduction of a signal size according to a pixel position. And to an apparatus. According to the present invention, the raw image is maintained by maintaining the original color as much as possible through automatic compensation of each RGB considering the characteristics of each color filter, and automatic compensation of each gain and level according to the light transmittance difference according to the position. It is possible to prevent the degradation of quality.

Image sensor, shading phenomenon, correction, pixel

Description

Method and apparatus for automatically compensating lens shading phenomenon in an image sensor

1 shows the difference in transmittance.

2 is a graph of change in signal magnitude with distance from pixel center.

3 is a view schematically showing the configuration of an image device according to an embodiment of the present invention.

4 is a diagram showing a detailed configuration of an automatic correction processing unit according to an embodiment of the present invention.

5 is a diagram illustrating a method of detecting a center pixel of a shading image according to an exemplary embodiment of the present invention.

6 illustrates a method of generating a correction register table in accordance with a preferred embodiment of the present invention.

7 illustrates an incorrect calibration register table.

8 is a flow chart showing the flow of the automatic correction method of the lens shading phenomenon according to an embodiment of the present invention.

9 illustrates a method of calculating a compensation value in an arbitrary block according to an exemplary embodiment of the present invention.

10 is a view showing a level and gain adjustment method according to an embodiment of the present invention.

11 is a view showing in detail the level and gain adjustment method according to an embodiment of the present invention.

12 is a view showing a method for setting to have a smoothed transmittance according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

130: automatic correction processing unit

200: pixel value analyzer 210: automatic exposure value setting unit

220: center position detection unit 230: table generation unit

240: level and gain adjustment unit 250: pixel position calculation unit

260: compensation curve generation unit 270: correction execution unit

The present invention relates to a method and apparatus for correcting a lens shading phenomenon in an image sensor, and in particular, a method for automatically correcting a lens shading phenomenon in an image sensor capable of maintaining a quality of a raw image by automatically correcting a reduction in signal size according to a pixel position. And to an apparatus.

Recently, portable devices (eg, digital cameras, mobile communication terminals, etc.) equipped with image sensors have been developed and sold. The image sensor is configured as an array of small photosensitive diodes called pixels or photosites. The pixels themselves usually do not extract color from light, but only convert photons from a broad spectral band into electrons. In order to record color images with a single sensor, the sensor is filtered so that different pixels receive different color illumination. This type of sensor is known as a color filter array or color filter array (CFA). Different color filters are arranged in a predefined pattern across the sensor.

The most common pattern is the Bayer color filter array (CFA) developed by Kodak. The CFA of a color image generally follows the Bayer Pattern. That is, half of the total number of pixels is green (G), and each quarter of the total number is allocated to red (R) and blue (B). To obtain color information, the color image pixels are formed in a repeating pattern with a red, green or blue filter, for example a 2 x 2 array for Bayer patterns.

The Bayer pattern is based on the premise that the human eye derives most of the luminance data from the green content of the scene. Thus, by allowing more of the pixels to be green, a higher resolution image can be produced compared to an alternate RGB color filter in the same number of red, green and blue pixels.

However, the conventional image sensor included in the recently developed and sold portable device has a problem of image distortion due to the geometric arrangement of the pixel array configuration. This is because it has a small external lens and a large f number.

A diagram showing the difference in transmittance is shown in FIG. 1, and a graph of the change in signal magnitude with distance from the center is shown in FIG. 2.

As shown in FIG. 1, pixels at the center of the CFA of the image sensor and pixels at the outside are exposed to the light source at different positions. These minute positional differences cause illuminance (illumination) difference, and the illuminance difference also affects the color due to the wavelength difference of the light and the refractive index difference of the lenses. As a result, color distortion and a reduction in signal size depending on the position of the pixel (see Fig. 2) inevitably occurs, which causes the quality of the raw image to deteriorate.

In order to overcome this problem, there was a method of correcting lens shading to have the same luminance as a whole when an image of a white region was taken. However, conventionally, in order to have the same luminance as a whole, it is a manual method of determining whether the luminance is the same with the human eye, and there is a problem of incorrect correction or setting of different luminance for each person.

Accordingly, an object of the present invention for solving the above problems is to provide a method and apparatus for automatically correcting a lens shading phenomenon in an image sensor that can prevent deterioration of a raw image.

It is another object of the present invention to automatically compensate for the overall illuminance of an image sensor, to automatically compensate for lens shading in an image sensor that can automatically compensate for color distortion due to each RGB color filter and signal size reduction for pixel position. It is to provide a method and apparatus.

Another object of the present invention is to maximize the original color through automatic compensation of each RGB considering the characteristics of each color filter, automatic compensation of each gain (Gain) and level according to the difference in light transmittance according to the position The present invention provides a method and apparatus for automatically correcting a lens shading phenomenon in a sustainable image sensor.

It is still another object of the present invention to provide a method and apparatus for automatically correcting a lens shading phenomenon in an image sensor capable of automatically correcting a position of a center pixel of a shading image.

In order to achieve the above object, according to an aspect of the present invention, (a) generating the analysis information corresponding to each pixel using a digital image signal sequentially received from the sensor unit corresponding to each pixel; (b) measuring an average brightness of an area having a predetermined size with respect to the first center pixel of the pixel array based on the analysis information and setting an automatic exposure value; (c) detecting a second center pixel in a shading image corresponding to the digital video signal; (d) generating and storing block-specific compensation values classified according to distances from the second center pixel and corresponding to the automatic exposure value; (e) calculating a distance between any compensation target pixel and the second center pixel; calculating a compensation value corresponding to the compensation target pixel by using a block-specific compensation value corresponding to the distance; And (g) generating correction pixel information by adding analysis information corresponding to the compensation target pixel and the compensation value to provide automatic correction of the lens shading phenomenon in the image sensor.

Preferably, steps (e) to (g) are performed sequentially for each of the sequentially received pixels, and in step (c), an automatic exposure upper limit and an automatic exposure lower limit having a predetermined interval are automatically adjusted. Setting the exposure value to a median value; Adjusting the automatic exposure upper limit and the automatic exposure lower limit to detect intersection pixels between the automatic exposure upper limit and the automatic exposure lower limit and the horizontal center line and the vertical center line passing through the first center pixel; And detecting the second center pixel using the intersection pixels. Step (d) may include (d-1) dividing blocks according to the distance from the second center pixel; And (d-2) changing the compensation value for each block, and counting the number of pixels having a value equal to or less than the upper limit of the automatic exposure and higher than the lower limit of the automatic exposure among pixels included in the block to which the changed block-based compensation value is applied; And (d-3) storing the compensation value for each block when the count value is the largest, and repeating steps (d-1) to (d-3) for the entire image area photographed. Can be done.

The analysis information may include any one of luminance information, level information, gain information, and a combination thereof, and the compensation value for each block corresponds to the luminance information, level compensation value, and gain compensation according to the analysis information. And a compensation value for each block is two compensation values generated by using the difference between the analysis information of each block start position and block end position and the automatic exposure value, and the (f) ) The step of selecting a block corresponding to the distance; Extracting two compensation values corresponding to the selected block; Generating a linear equation that passes the extracted two compensation values and has the distance as a variable; And calculating a compensation value corresponding to the distance using the linear equation.

The digital video signal is a Bayer pattern video signal, and the block-specific compensation value is generated based on a luminance component based on the green (G) pixel, and the step (d) includes the generated block. Checking an error of a respective compensation value; And generating a compensation value for each block newly when there is an error, and storing the compensation value for each block if there is no error, and checking the error of the generated compensation value for each block. If the compensation value of the block having the closest distance from the second center pixel is less than or equal to the compensation value of the far block, it may be determined that there is an error.

In order to achieve the above objects, according to another aspect of the present invention, there is provided an image processor of an image device for automatically correcting a lens shading phenomenon in an image sensor, wherein the image device includes a sensor unit, the image processor and a display unit. And generating analysis information corresponding to a digital image signal sequentially input from the sensor unit corresponding to each pixel, and measuring average brightness of an area having a predetermined size around the first center pixel of the pixel array. Setting the automatic exposure value, detecting a second center pixel in a shading image corresponding to the digital image signal, generating a block-specific compensation value corresponding to the automatic exposure value, which is classified according to the distance from the second center pixel; And calculates a distance between an arbitrary compensation target pixel and the second center pixel, Compensation value corresponding to the pixel to be compensated is calculated by using a block-specific compensation value corresponding to a predetermined distance, and automatically corrected to generate and output correction pixel information by adding analysis information corresponding to the pixel to be compensated and the compensation value. Processing unit; And a subsequent processor configured to process the correction pixel information so that the corrected pixel information can be displayed through the display unit.

Preferably, the apparatus further includes an interpolation processor that performs an interpolation process using the correction pixel information, and the subsequent processor may receive the interpolated correction pixel information.

In order to achieve the above object, according to another aspect of the present invention, in the automatic lens shading phenomenon automatic correction device for automatically correcting the lens shading phenomenon in the image sensor, from the sensor unit for photographing the subject to generate a digital image signal A pixel value analyzer configured to generate analysis information corresponding to each pixel by using the digital image signals sequentially input; An automatic exposure value setting unit configured to measure an average brightness of an area having a predetermined size based on the first center pixel of the pixel array based on the analysis information and set the automatic exposure value; A center position detector for detecting a second center pixel in a shading image corresponding to the digital image signal; A table generator configured to generate and store a compensation value for each block classified according to a distance from the second center pixel and corresponding to the automatic exposure value; A pixel position calculator configured to calculate a distance between an arbitrary compensation target pixel and the second center pixel; A compensation curve generator configured to calculate a compensation value corresponding to the compensation target pixel by using a block-specific compensation value corresponding to the distance; And a correction performing unit configured to generate and output correction pixel information by adding analysis information corresponding to the compensation target pixel and the compensation value.

Preferably, the automatic lens shading phenomenon correction device is provided between the sensor unit and a subsequent processing unit, the correction performing unit outputs the correction pixel information to the subsequent processing unit, and the subsequent processing unit outputs the correction pixel information to the display unit. Can be processed to be displayed.

Other objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and the preferred embodiments associated with the accompanying drawings.

Hereinafter, preferred embodiments of a method and apparatus for automatically correcting a lens shading phenomenon of an image sensor according to the present invention will be described in detail with reference to the accompanying drawings. The components to be given the same reference numerals and duplicate description thereof will be omitted.

3 is a diagram schematically illustrating a configuration of an image device according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the image device 100 according to the present invention includes a sensor unit 110, an image processing unit 125, and a display unit 180. Of course, in addition to this may further include a key input unit, a memory, etc., which is not relevant to the gist of the present invention, description thereof will be omitted.

The sensor unit 110 includes a color filter array (CFA) 115 and an A / D converter 120. Of course, the sensor unit 110 may further include a lens (not shown).

The CFA 115 converts the optical object signal input through the lens into an electrical signal and outputs the electrical signal. In this case, the CFA 115 uses a Bayer pattern, which is advantageous in terms of resolution, and an image signal having one color information is output for each pixel. That is, an image signal having only R information is output from a pixel corresponding to the R (red) pattern, and an image signal having only G information is output from a pixel corresponding to the G (green) pattern, and corresponding to a B (blue) pattern. In the pixel, an image signal having only B information is output. The value of each pixel obtained through the CFA 115 of the Bayer pattern is interpolated (interpolation, for example, averaging the values of 2 pixels on the left and right, or 4 pixels on the top, bottom, left, and right sides to infer missing color information). To get complete color information. The interpolation process is performed by the interpolation processor 140.

The A / D converter 120 converts the image signal converted by the CFA 115 into a digital signal and transmits the converted digital signal to the automatic correction processor 130.

The image processing unit 125 may include an automatic correction processor 130, a correction register table 135, an interpolation processor 140, an interpolation memory 145, a color adjuster 150, a gamma converter 155, and a gamma table ( 160, a format conversion unit 165, and a format conversion table 170. In addition, the image processing unit 125 may include a timing generator (not shown) for generating various timing signals from the horizontal synchronization signal Hsync, the vertical synchronization signal Vsync, and the pixel clock PCLK used to drive the CFA 115. Not) may be further included.

The automatic correction processor 130 performs luminance analysis of each image signal, gain and level analysis of each RGB, center pixel detection of the shading image, and automatically corrects the image according to a predetermined method. The original image signal is transmitted to the interpolation processor 140.

Correction through detection of the center pixel of the shading image, gain of each RGB and level analysis is automatically performed through automatic exposure value setting. Gain is related to the RGB intensity in the frame. Since there is a difference in the transmittance of light between the center pixel and the outer pixel, a difference in the RGB intensity may occur, so a gain analysis is required. The level is related to the brightness of each pixel. For example, when the level of every pixel in the frame is 10, the brightness of the entire screen may be 10. As described above, the automatic correction processor 130 according to the present invention has the effect of not degrading the quality of the raw image by correcting the image signal of all the pixels in the frame so as to correspond to the gain and the level value by the automatic exposure value setting. The configuration and function of the automatic correction processor 130 will be described in detail later with reference to FIG. 4.

The correction register table 135 is generated by the luminance component and is generated based on the value of any one of RGB and the center pixel of the shading image. For example, given the largest number of RGB values, and assuming that the human eye derives most of the luminance data from the green content of the scene, the G value differs from the G value and other component values (ie, R value and B). Value) is calculated and the difference is set to correspond to the automatic exposure value. The correction register table 135 has a value in blocks (for example, 16 pixels, 32 pixels, 64 pixels, etc.) formed according to the distance from the position of the center pixel. As the spacing between blocks is wider, the shading problem becomes inaccurate due to the problem of block value boundary. If you use 16 pixels, you can get accurate shading correction. However, 32 pixels are generally used because many registers must be included. The reason for forming blocks in units of pixels is to omit the division operation when shading compensation because the shift operation is performed. The correction register table 135 shown in FIG. 3 may be a storage area for storing the generated correction register table. Hereinafter, with reference to FIG. 6 will be described in detail.

The interpolation processor 140 generates a pixel signal of RGB for each pixel. When the video signal output from the CFA 115 has a Bayer array, a pixel signal of green (G) or blue (B) cannot be obtained for a pixel corresponding to red (R). Therefore, the interpolation processor 140 may generate a pixel signal of green (G) or blue (B) in the color filter pixel of red (R) by interpolating the signal of the surrounding pixel. To this end, pixel signals of surrounding pixels are temporarily recorded in the interpolation memory 145, and the interpolation processor 140 performs interpolation operations using pixel signals of surrounding pixels temporarily recorded in the interpolation memory 145. To perform.

The color adjuster 150 is a means for adjusting the color tone (for example, bluish blue, etc.), and the gamma converter 155 is a device characteristic for outputting an image to the display unit 180 (for example, LCD, CRT, etc.). It is a means to match (gamma characteristic). The gamma table 160 stores a conversion table for converting into gamma characteristics of the image output device of the display unit 180.

The format converter 165 converts the pixel signal into a format of an image signal suitable for the display unit 180. The format converter 165 converts the pixel signal into a format of a digital component such as NTSC, YUV, or YCbCr and outputs the converted signal. The format conversion table 170 is a table for converting to a display signal format such as NTSC or YUV.

4 is a diagram illustrating a detailed configuration of an automatic correction processor 130 according to an exemplary embodiment of the present invention, and FIG. 5 is a diagram illustrating a method of detecting a center pixel of a shading image according to an exemplary embodiment of the present invention. 6 is a diagram illustrating a method of generating a correction register table 135 according to an exemplary embodiment of the present invention, and FIG. 7 is a diagram illustrating an example of an incorrect correction register table 135 generation.

Referring to FIG. 4, the automatic correction processor 130 may include a pixel value analyzer 200, an automatic exposure value setter 210, a center position detector 220, a table generator 230, a level and gain adjuster 240. , A pixel position calculator 250, a compensation curve generator 260, and a correction performer 270.

The pixel value analyzer 200 analyzes luminance information, gain information, and level information corresponding to each pixel by using a digital image signal received in line units from the sensor unit 110. The pixel value analyzer 200 may analyze the digital image signal in units of lines, analyze the entire frame, or perform sampling analysis on only the center line. The pixel value analyzer 200 according to the present invention analyzes an image signal having a Bayer pattern with respect to each component of RGB, and thus may be analyzed in a state where there is no distortion of the output image. In addition, since the pixel value analyzer 200 according to the present invention analyzes the image signal before the interpolation process, the number of analyzed data may be reduced to 1/3. In addition, it is apparent that the pixel value analyzer 200 may apply other options corresponding to bit information (for example, 10 bits or 8 bits) of the input image signal. The pixel value analyzer 200 may analyze each of the RGB since the input digital image signal is input in an RGB Bayer pattern.

The automatic exposure value setting unit 210 selects an area of a predetermined size (for example, an area of about 200 × 200 pixels) from the center area of the pixel array of the captured image, and the average luminance (brightness) of the selected area is automatically exposed. The automatic exposure value is set so that it is an intermediate value between the upper limit (Up_limit) and the automatic exposure lower limit (Down_limit). The interval between the automatic exposure upper limit and the automatic exposure lower limit is preset, which may be set by the user. This is used to fix the luminance at the center of the pixel array. In addition, the luminance of the non-center part can be adjusted based on the luminance at the fixed center. That is, the automatic exposure value is a target value to be compensated for in the captured image.

The center position detector 220 searches for the center pixel of the shading image from the white image. This is to ensure accurate centering if the center of the shading image is not the center of the pixel array. Also, if the shading image is not centered, the image may be distorted. When the center pixel of the shading image is found, the position of the center pixel is stored in the correction register table 135, and a shading compensation image is generated about the center pixel.

A method of finding the center pixel will be briefly described with reference to the drawing shown in FIG. 5. The center position detector 220 makes the upper limit of the automatic exposure lower than the value of the brightest part of all pixels, and adjusts the upper limit and the automatic exposure lower limit so that the lower limit of the automatic exposure is larger than the value of the darkest part. A circular band of pixels is created where the luminance of the pixel is below the auto-exposure upper limit and above the auto-exposure lower limit, and eight intersections meet the boundary of the circular band and the vertical center line 550 and horizontal center line 560 of the pixel array. Find pixels 510-516, 520-526. Here, the vertical center line 550 and the horizontal center line 560 of the pixel array are predetermined. The intersection of the vertical bisectors of the intersection pixels 514 and 516 that meets the vertical bisector and the horizontal center line 560 of the intersection pixels 510 and 512 among the intersection pixels due to the automatic exposure upper bound It is the center pixel of the image. This is due to the principle that the boundary of the circular band is circular and the segment connecting the intersection pixels 510, 512 or 514, 516 becomes the string of the circle, and thus the vertical bisector of the string passes through the center of the circle. The same applies to the intersection pixels 520 to 526 by the automatic exposure lower limit boundary.

After correcting the center pixel by the above method, the automatic exposure upper limit and the automatic exposure lower limit are readjusted to correspond to the automatic exposure value set by the automatic exposure value setting unit 210. The center pixel of the shading image may be found using the above method, and in addition, the center pixel of the shading image may be found by a person skilled in the art by various methods. If the correction of the center pixel is not done properly, chromatic aberration occurs, which causes different colors to appear around the entire area of the image, and it is difficult to find the right color through color correction.

The table generator 230 may analyze analysis information (for example, gains and level values of RGB, luminance values, etc.) analyzed by the pixel value analyzer 200, and an automatic exposure value set by the automatic exposure value setting unit 210. In addition, the correction register table 135 including the center pixel position and / or the compensation value of the shading image found by the center position detector 220 is generated and stored.

Referring to FIG. 6, the distance between the center pixel and each pixel is divided as a block. The compensation value may be generated to correspond to, for example, a block unit (eg, a specific block start position and a specific block end position). In order to be able to have the automatic exposure value set in blocks A to E, in (a, b) to (e, f) (where (block start position compensation value, block end position compensation value)) in the existing shading curves, respectively, The corresponding compensation values should be further summed up.

In order to generate the compensation value, the number of pixels having a value between an automatic exposure upper limit (Up_limit) and an automatic exposure lower limit (Down_limit) is counted for each block. As the compensation value is increased or decreased, a change in the number of pixels having a value between the automatic exposure upper limit and the automatic exposure lower limit (tuning range) is checked to determine the compensation value when having the largest number of pixels. In FIG. 6, in the case of block A, there was no pixel having a tuning range value at first, but as a compensation value a is added, almost all pixels of block A have a tuning range value. If this process is performed for all blocks of the image, the compensation value is automatically determined for each block. Here, when the automatic exposure value is smaller than the luminance value of the center pixel of the shading image, it is obvious that the compensation value at the center pixel of the shading image may be negative.

After generating the compensation register table, error checking may be performed before storage. Referring to FIG. 6, the shading curve has a parabolic shape based on the center pixel position of the shading image. Therefore, the compensation value also has the form of a parabola. ① Whether the block compensation value is a sharp rise (for example, 100 or more) than the previous block compensation value and ② The block compensation value is smaller than the previous block compensation value. It is checked whether it is lost (for example, when the compensation value d of the block D is smaller than the compensation value c of the block C). If any of the above conditions are not satisfied, there is an error in the calibration table and a new calibration table is generated. Referring to FIG. 7, the compensation value should also have a dotted parabolic shape (a) when the block compensation value corresponds to ① having a sharp rise than the previous block compensation value, and (b) indicates the block compensation value. This is the case that 2 is smaller than the previous block compensation value and each has an error. In this case, a new calibration table is created.

The level and gain adjusting unit 240 corrects the shading phenomenon by finely adjusting the gain and level with respect to the RGB of each block. The level and gain adjusting unit 240 may adjust the gain not only to the decimal point level but also to adjust the level in the positive direction and the negative direction (see FIG. 10). The level and gain adjustment method will be briefly described with reference to FIG.

The correction table is generated using the G component, which is one of the three components of the Bayer type, and thus is not optimized for the remaining R and B components. In other words, the RGB intensity is generally inconsistent in the shading image. However, although the RGB intensity is generally 1110 at the position of the center pixel, the RGB intensity may be inconsistent 1120 even at the position of the center pixel according to the characteristics of the lens. In this case, the level and gain adjusting unit 240 may adjust through gain compensation when the center value of the pixel array center for each component of RGB is the same and the values of the surrounding pixels are different (1110), and the center value of the center of the pixel array. In the case where the values of and adjacent pixels are different from each other (1120), the level and gain may be adjusted by compensation.

The compensation method is similar to the method of generating the correction table in the table generator 230. First, the R component and the B component are divided by blocks, and the number of pixels included in the level tuning range is counted so that the level in the block including the center pixel can approximate the level of the G component. Thereafter, by increasing or decreasing the level compensation value, the number of pixels included in the level tuning range is counted to set the level compensation value when the largest number of pixels is the level compensation value of the corresponding block. Thereafter, the level compensation value is set for each block in the same manner. The gain of the R component and the B component is adjusted, and the gain compensation value is set in the same manner as the method of setting the level compensation value based on the gain of the G component.

The pixel position calculator 250 calculates a distance between the center pixel and each pixel of the shading image found by the center position detector 220. For example, the automatic correction processor 130 counts image signals coming in the horizontal and vertical directions (which may be performed by the pixel value analyzer 200 or a separate counting means, for example). Indicates the position of the corresponding pixel. Using this, the pixel position calculator 250 may calculate a distance between each pixel and the center pixel, and the distance between each pixel and the center pixel is divided as a block (see FIG. 6).

In addition, the counted number is generated in the table generator 230 and the compensation value, the level and the gain compensation unit 240 generated in the correction register table 135 and stored in the correction register table 135 and the level compensation Let each pixel be associated with a value.

The compensation curve generator 260 extracts a compensation value stored in the compensation register table 135 to be linked to the counted number and calculates a compensation value for any particular pixel. The value of the correction register table 135 is set to correspond to the unit block (eg, 16 pixels, 32 pixels, 64 pixels) of the pixel array, and the compensation values within the unit block are two table values (eg, blocks). The compensation value of the start position and the compensation value of the block end position). This will be described in detail later with reference to FIGS. 8 to 9.

The correction performing unit 270 generates correction pixel information by adding the analysis information analyzed by the pixel value analyzer 200 and the compensation value calculated by the compensation curve generator 260 for each pixel, and generates the generated correction pixel. The information is transmitted to the interpolation processor 140. That is, the corrected image from which the shading phenomenon is removed is transmitted to the interpolation processor 140.

8 is a flowchart illustrating a method for automatically correcting a lens shading phenomenon according to an exemplary embodiment of the present invention, and FIG. 9 is a diagram illustrating a method of calculating a compensation value in an arbitrary block according to an exemplary embodiment of the present invention. 10 is a view showing a level and gain adjustment method according to an embodiment of the present invention, Figure 11 is a view showing in detail a level and gain adjustment method according to an embodiment of the present invention, Figure 12 2 is a view showing a method for setting to have a smoothed transmittance according to an embodiment of the present invention.

Referring to FIG. 8, in operation 810, the pixel value analyzer 200 receives a digital image signal corresponding to a white image obtained by photographing only a white region from the sensor unit 110. The digital image signal corresponding to the white image input through step 810 has a shading image characteristic that becomes darker from the center of the imaging surface to the edge according to the geometrical characteristics of the lens. Analysis information is generated by analyzing luminance values, gain values, and level values for each pixel.

In operation 815, the automatic exposure value setting unit 210 measures an average brightness of a region having a predetermined size centering on the center pixel of the pixel array using a digital image signal input in line units. In operation 820, the automatic exposure value setting unit 210 sets the average brightness as the automatic exposure value. The automatic exposure upper limit and the automatic exposure lower limit are determined so that the automatic exposure value is an intermediate value of the tuning range (the interval between the automatic exposure upper limit and the automatic exposure lower limit) of the preset interval.

In operation 825, the center position detector 220 detects a center pixel corresponding to the center position of the shading image by using the digital image signal input in line units.

In step 830, the table generator 230 compensates for each pixel or block by using the analysis information, the automatic exposure value, the center pixel of the shading image, the distance between the center pixel and each pixel (which may be divided into blocks). Create a value. The compensation value and / or analysis information, the automatic exposure value, the center pixel of the shading image, the distance between the center pixel and each pixel (or the distance from the center pixel to each block) are stored in the correction register table 135.

In step 835, the level and gain adjustment unit 240 finely adjusts the gain and level for the RGB of each block. The compensation value stored in the correction register table 135 is generated using the G component, and thus is not optimized for the remaining R and B components. The adjustment method is similar to the method of generating the correction table in the table generator 230. First, the R component and the B component are divided by blocks, and the number of pixels included in the level tuning range is counted so that the level in the block including the center pixel can approximate the level of the G component. Thereafter, by increasing or decreasing the level compensation value, the number of pixels included in the level tuning range is counted to set the level compensation value when the largest number of pixels is the level compensation value of the corresponding block. Thereafter, the level compensation value is set for each block in the same manner. The gain of the R component and the B component is adjusted, and the gain compensation value is set in the same manner as the method of setting the level compensation value based on the gain of the G component.

In operation 840, the pixel position calculator 250 calculates a distance between the center pixel and each pixel of the shading image using the counted number representing each pixel position.

In operation 845, the compensation curve generator 260 performs an arbitrary table value (for example, the compensation value of the block start position and the block end in the block in which the corresponding pixel is located) in the stored compensation register table 135 to be interlocked with the counted number. The compensation value of the position) is extracted to calculate a compensation value corresponding to the pixel. Here, the compensation value may include a gain compensation value and a level compensation value. As shown in FIG. 9, when the pixel to be corrected currently is included in the block C, the compensation curve generator 260 performs a table value (ie, a compensation value a) of the start position of the block C and a table value of the end position (ie , The compensation value b) is extracted from the correction register table 135. The linear equations are generated by connecting the extracted two compensation values in a straight line, and then the first equation value corresponding to the distance of the corresponding pixel is determined as the compensation value.

In operation 850, the correction performing unit 270 generates correction pixel information by adding the analysis information in operation 810 and the compensation value in operation 845, and proceeds to operation 855 to transfer the generated correction pixel information to the interpolation processor 140. do.

Although not shown in FIG. 8, it is apparent that steps 845 to 850 may be repeatedly performed for all pixels included in the frame.

As described above, the automatic correction processor 130 according to the present invention may generate an image in which a shading phenomenon is corrected by automatically finely adjusting gain and level for each RGB. The automatic correction processor 130 may not only adjust the gain to the decimal point level but also adjust the level in the positive direction and the negative direction (see FIG. 10). The level and gain adjustment method will be briefly described with reference to FIG. RGB intensities are generally inconsistent throughout the shading image. However, although the RGB intensity is generally 1110 at the position of the center pixel, the RGB intensity may be inconsistent 1120 even at the position of the center pixel according to the characteristics of the lens. In this case, the automatic correction processing unit 130 according to the present invention may adjust the gain through the compensation of the center when the center value of the pixel array center for each component of RGB is the same and the value of the surrounding pixels is different (1110). In the case where the center value of and the neighboring pixel values are different from each other (1120), the level and gain compensation may be performed.

As such, the user may use the correction image having the smoothed transmittance through gain adjustment for adjusting the slope of the compensation curve and level adjustment for adjusting the level of the compensation curve (see FIG. 12).

As described above, the method and apparatus for automatically correcting the lens shading phenomenon in the image sensor according to the present invention can prevent the degradation of the raw image.

In addition, the present invention can automatically compensate for the overall illuminance of the image sensor, the color distortion by the respective color filters of RGB, and the size reduction of the signal with respect to the pixel position.

In addition, the present invention can maintain the original color as much as possible through automatic compensation of each RGB considering the characteristics of each color filter, automatic gain and level according to the light transmittance difference according to the position. .

In addition, the present invention can automatically correct the position of the center pixel of the shading image.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art to which the present invention pertains without departing from the spirit and scope of the present invention as set forth in the claims below It will be appreciated that modifications and variations can be made.

Claims (21)

In the lens shading phenomenon automatic correction method in the image sensor, (a) generating analysis information corresponding to each pixel by using a digital image signal sequentially received from a sensor unit corresponding to each pixel; (b) measuring an average brightness of an area having a predetermined size with respect to the first center pixel of the pixel array based on the analysis information and setting an automatic exposure value; (c) detecting a second center pixel in a shading image corresponding to the digital video signal; (d) generating and storing block-specific compensation values classified according to distances from the second center pixel and corresponding to the automatic exposure value; (e) calculating a distance between any compensation target pixel and the second center pixel; calculating a compensation value corresponding to the compensation target pixel by using a block-specific compensation value corresponding to the distance; And and (g) generating correction pixel information by adding analysis information corresponding to the compensation target pixel and the compensation value. The method of claim 1, Step (e) to (g) is a method for automatically correcting the lens shading phenomenon in the image sensor is performed sequentially for each of the sequentially received pixels. The method of claim 1, wherein step (c) Setting an automatic exposure upper limit and an automatic exposure lower limit having a predetermined interval to have the automatic exposure value as an intermediate value; Adjusting the automatic exposure upper limit and the automatic exposure lower limit to detect intersection pixels between the automatic exposure upper limit and the automatic exposure lower limit and the horizontal center line and the vertical center line passing through the first center pixel; And And detecting the second center pixel using the intersection pixels. The method of claim 3, wherein step (d) (d-1) dividing blocks according to the distance from the second center pixel; And (d-2) changing the compensation value for each block and counting the number of pixels having a value equal to or less than the upper limit of the automatic exposure and higher than the lower limit of the automatic exposure among pixels included in the block to which the changed block-based compensation value is applied; And (d-3) storing a compensation value for each block when the count value is the largest; A method for automatically correcting a lens shading phenomenon in an image sensor which repeatedly performs the steps (d-1) to (d-3) for the entire image area photographed. The method according to any one of claims 1, 3 or 4, The analysis information includes any one of luminance information, level information, gain information, and a combination thereof, and the compensation value for each block corresponds to the luminance compensation value, level compensation value, gain compensation value, and the like according to the analysis information. A method for automatically correcting a lens shading phenomenon in an image sensor including any one of these combinations. The method of claim 5, wherein the compensation value for each block is two compensation values generated by using the difference between the analysis information of each block start position and the block end position and the automatic exposure value. . The method of claim 6, wherein step (f) Selecting a block corresponding to the distance; Extracting two compensation values corresponding to the selected block; Generating a linear equation that passes the extracted two compensation values and has the distance as a variable; And And calculating a compensation value corresponding to the distance by using the linear equation. The method of claim 1, wherein the digital image signal is a Bayer pattern image signal. The method of claim 8, wherein the compensation value for each block is generated based on a luminance component based on the green (G) pixel. The method of claim 1, wherein step (d) Checking an error of the generated compensation value for each block; And And automatically generating a compensation value for each block if there is an error and storing the compensation value for each block if there is no error. The method of claim 10, wherein the checking of the error of the generated block-by-block compensation value comprises: And determining that there is an error when the compensation value of the block having a short distance from the second center pixel is less than or equal to the compensation value of the far block or there is a sudden change in the compensation value. An image processor of an image device for automatically correcting a lens shading phenomenon in an image sensor, wherein the image device includes a sensor unit, the image processor, and a display unit, The sensor unit generates analysis information corresponding to a digital image signal sequentially input corresponding to each pixel, measures an average brightness of a region having a predetermined size centering on the first center pixel of the pixel array, and sets the automatic exposure value. Detect a second center pixel in a shading image corresponding to the digital image signal, generate and store a block-specific compensation value according to the distance from the second center pixel and corresponding to the automatic exposure value, and optionally Calculating a distance between the pixel to be compensated and the second center pixel, calculating a compensation value corresponding to the pixel to be compensated by using a block-by-block compensation value corresponding to the distance, and analyzing information corresponding to the pixel to be compensated An automatic correction processor for generating correction pixel information by adding the compensation value and the compensation value; And And a subsequent processing unit for processing the correction pixel information to be displayed on the display unit. The method of claim 12, Further comprising an interpolation processing unit for performing an interpolation process using the correction pixel information, And the subsequent processor automatically corrects lens shading in an image sensor that receives the interpolated corrected pixel information. The method of claim 12, wherein the second center pixel is The automatic exposure upper limit and the automatic exposure lower limit detected by adjusting the automatic exposure upper limit and the automatic exposure lower limit set to have the automatic exposure value as the intermediate value at a predetermined interval with the horizontal center line and the vertical center line passing through the first center pixel. An image processor that automatically corrects lens shading in an image sensor detected using intersection pixels. 15. The method of claim 14, wherein the compensation value for each block is A block is divided according to the distance from the second center pixel, the compensation value for each block is changed, and a value less than or equal to the upper limit of the automatic exposure and more than the lower limit of the automatic exposure among pixels included in the block to which the changed block-specific compensation value is applied. An image processor for automatically correcting the lens shading phenomenon in the image sensor is determined by counting the number of pixels having a number, and storing the block-by-block compensation value when the count value is the largest. The method according to any one of claims 12, 14 or 15, The analysis information includes any one of luminance information, level information, gain information, and combinations thereof, and the compensation value for each block corresponds to the luminance information, a level compensation value, a gain compensation value, and a combination thereof. An image processor that automatically corrects lens shading in an image sensor comprising any of the following. In the lens shading phenomenon automatic correction device for automatically correcting the lens shading phenomenon in the image sensor, A pixel value analyzer configured to generate analysis information corresponding to each pixel by using the digital image signal sequentially input from a sensor unit which photographs a subject to generate a digital image signal; An automatic exposure value setting unit configured to measure an average brightness of an area having a predetermined size with respect to the first center pixel of the pixel array based on the analysis information and set an automatic exposure value; A center position detector for detecting a second center pixel in a shading image corresponding to the digital image signal; A table generator configured to generate and store a compensation value for each block classified according to a distance from the second center pixel and corresponding to the automatic exposure value; A pixel position calculator configured to calculate a distance between an arbitrary compensation target pixel and the second center pixel; A compensation curve generator configured to calculate a compensation value corresponding to the compensation target pixel by using a block-specific compensation value corresponding to the distance; And And a correction performing unit configured to generate and output correction pixel information by adding analysis information corresponding to the compensation target pixel and the compensation value. The method of claim 17, The automatic lens shading phenomenon correction device may be provided between the sensor unit and a subsequent processing unit. The correction performing unit may output the correction pixel information to the subsequent processing unit, and the subsequent processing unit may display the corrected pixel information through the display unit. So that the lens shading phenomenon automatic correction device to process. The method of claim 17, wherein the center position detector The auto exposure upper limit and the auto exposure lower limit having a predetermined interval are set to have the auto exposure value as an intermediate value, and the auto exposure upper limit and the auto exposure lower limit are adjusted to adjust the auto exposure upper limit and the auto exposure lower limit and the first center. And an intersection pixel between the horizontal center line and the vertical center line passing through the pixel, and detecting the second center pixel using the intersection pixels. The method of claim 19, wherein the table generating unit A block is divided according to the distance from the second center pixel, the compensation value for each block is changed, and a value less than or equal to the upper limit of the automatic exposure and more than the lower limit of the automatic exposure among pixels included in the block to which the changed block-specific compensation value is applied. A lens shading phenomenon automatic correction device for counting the number of pixels having a number, and for each block stores the compensation value for each block when the count value is the largest. The method according to any one of claims 17, 19 or 20, The analysis information includes any one of luminance information, level information, gain information, and combinations thereof, and the compensation value for each block corresponds to the luminance information, a level compensation value, a gain compensation value, and a combination thereof. Automatic lens shading phenomenon correction device comprising any one of.

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