JP4833669B2 - Imaging apparatus and signal processing method thereof - Google Patents

Description

  The present invention relates to an image pickup apparatus such as a digital camera having an image pickup means for converting an optical signal obtained via an optical system into an image signal and outputting the image signal, and a signal processing method thereof.

  Conventionally, when an imaging device such as a digital camera converts a captured optical signal into an image signal, random noise is generated by amplifying a small amount of light. When the image signal includes a high-brightness signal exceeding the processing capability of the signal processing circuit, the noise of the high-brightness image signal needs to be clipped to keep the signal level within a predetermined range. The average value of the image signal on the high luminance side clipped in this way falls below a desired average value that should be originally obtained, and as a result, a whiteout image is generated.

  Further, for example, an image signal obtained by photographing a subject having a gradation needs to be clipped to 0 because the noise has a minus component on the low luminance side. At this time, the average value of the image signal on the low luminance side is higher than the desired average value.

For example, in the image processing apparatus described in Patent Document 1, when an imaging signal clipped on the high luminance side generates a whiteout image including a flat white image, noise is generated by a noise generation circuit. By adding the imaging signal clipped by the adding circuit and noise, the flat portion of the imaging signal can be eliminated, the visual difference with respect to the image can be reduced, and a natural image without a sense of incongruity can be obtained. it can.
JP 2005-72835 A

  The average value of the image signal clipped by the imaging device is shifted up and down from the desired average value on the low luminance side and the high luminance side, respectively. However, the image processing apparatus of Patent Document 1 cannot avoid the deviation of the average values on the low luminance side and the high luminance side.

  In addition, the red, green, and blue channels of the three primary colors that represent image signals have different amounts of noise, so the amount of deviation of the average value on the low-brightness side and high-brightness side is different, and some color is achromatic. A phenomenon occurs. For example, when the deviation of the average value of the red channel is the largest, the low luminance region of the image indicated by the image signal is displayed with a magenta taste.

  The present invention eliminates the disadvantages of the prior art and effectively corrects image signals clipped on the low-luminance side and high-luminance side to obtain an image without a sense of incongruity and its signal processing method The purpose is to provide.

  In an imaging apparatus including first, second, and third signal processing means for performing signal processing on an image signal on which a noise clip process has been performed on a low-luminance side and a high-luminance side, showing a captured scene image The signal processing means includes an average value deviation correcting means for correcting an image signal for each of a plurality of color channels and correcting an average value deviation caused by a noise clip. The second signal processing means includes a white balance correction means for correcting the red data, the green data, and the blue data by correcting the white balance for each of the three primary colors of the red channel, the green channel, and the blue channel; Linear matrix processing means for performing a matrix operation on red data, green data and blue data using a predetermined color reproduction coefficient, and the linear matrix processing means includes a color reproduction coefficient determination means for determining a predetermined color reproduction coefficient. The color reproduction coefficient determination means determines red data, green data, and blue data after white balance correction, and determines a predetermined color reproduction coefficient according to the determination result. The third signal processing means corrects the white balance for each of the three primary color red channels, green channels, and blue channels, and uses the white balance gain for red, the white balance gain for green, and the white balance gain for blue. White balance correction means for correcting data, green data, and blue data, linear matrix processing means for performing matrix calculation of red data, green data, and blue data after white balance correction using predetermined color reproduction coefficients, and linear Gamma correction means for performing gamma correction on the red data, green data, and blue data after matrix processing using a predetermined gamma function. The gamma correction means includes a red gamma function and a green gamma function as the predetermined gamma function. And a gamma function determining means for determining a blue gamma function. To.

  Further, in a signal processing method for performing signal processing on an image signal that has been picked up and that has been subjected to noise clip processing on the low luminance side and the high luminance side, the signal processing method includes: And an average value deviation correction step of correcting an average value deviation caused by noise clip processing by correcting each time. Further, the signal processing method includes a white balance correction step for correcting the red data, the green data, and the blue data by correcting the white balance for each of the three primary colors of the red channel, the green channel, and the blue channel, and after the white balance correction. A linear matrix processing step of performing a matrix operation on red data, green data and blue data using a predetermined color reproduction coefficient, and the linear matrix processing step includes a color reproduction coefficient determination step of determining a predetermined color reproduction coefficient The color reproduction coefficient determination step is characterized by determining red data, green data, and blue data after WB correction, and determining a predetermined color reproduction coefficient according to the determination result. Furthermore, the signal processing method WB-corrects the image signal for each of the red, green and blue channels of the three primary colors, and uses the red WB gain, the green WB gain and the blue WB gain for red data and green data. WB correction process for correcting blue and blue data respectively, linear matrix processing process for matrix calculation of red data, green data and blue data after WB correction using a predetermined color reproduction coefficient, and red data after linear matrix processing A gamma correction step for performing gamma correction on the green data and the blue data using a predetermined gamma function, wherein the gamma correction step includes a gamma function for red, a gamma function for green, and a gamma function for blue A signal processing method comprising a gamma function determining step for determining.

  As described above, according to the imaging apparatus of the present invention, the red data, the green data, and the blue data of the image signal are corrected using the LUT or function of the luminance-dependent offset correction or gain correction. It is possible to obtain a high-quality image without a sense of incongruity by correcting the deviation of the average value of the image signal subjected to noise clip processing on the luminance side.

  Further, according to the imaging apparatus of the present invention, the noise clip processing is performed on the low luminance side and the high luminance side by performing a linear matrix operation on the red data, the green data, and the blue data of the image signal using the luminance-dependent color reproduction coefficient. It is possible to correct the deviation of the average value of the image signal subjected to.

  Further, according to the imaging apparatus of the present invention, noise clip processing is performed on the low luminance side and the high luminance side by performing gamma correction on the red data, the green data, and the blue data of the image signal using a luminance-dependent gamma function. The deviation of the average value of the image signals thus obtained can be corrected.

  Next, an embodiment of an imaging apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, the imaging apparatus 10 of the embodiment is controlled by a system control unit 14 by operating an operation unit 12 to capture incident light from an object scene in an optical system 16. The image is picked up by the image pick-up unit 18, and the picked-up image is processed by the pre-processing unit 20 to generate a digital image signal. This digital image signal is signal-processed by the signal processing unit 22, and particularly generated by noise clipping. The average value deviation correction unit 24 corrects the average value deviation. Note that portions not directly related to understanding the present invention are not shown and redundant description is avoided.

  In the present apparatus 10, for example, when the image signal is clipped by the preprocessing unit 20 and the image signal 120 has a negative component noise 122 on the low luminance side as shown in FIG. Are clipped to 0. The image signal after the clip processing is averaged by the signal processing unit 22, and the average values 126, 128 and 130 of each channel are obtained as desired in the low luminance side and the high luminance side as shown in FIG. The values rise and fall from the linear average value 124, respectively.

  In addition, the red, green, and blue channels of the three primary colors that represent image signals have different amounts of noise, so the amount of deviation of the average value on the low-brightness side and high-brightness side is different, and some color is achromatic. A phenomenon occurs. For example, as shown in FIG. 3, when the deviation of the average value 126 of the red channel is the largest and the deviation of the average value 130 of the green channel is the smallest, the low luminance region of the image indicated by the image signal has a magenta taste. Is displayed.

  The operation unit 12 is a manual operation device that inputs an operator's instruction, and supplies an operation signal 102 to the system control unit 14 in accordance with an operator's manual operation state, for example, a stroke operation of a shutter button (not shown). It has the function to do. In the following description, each signal is specified by the reference number of the connecting line in which it appears.

  The system control unit 14 is a control function unit that controls and controls the overall operation of the present apparatus in response to the operation signal 102 supplied from the operation unit 12. For example, a central processing unit (CPU) is connected to the system control unit 14. It may be configured to have.

  In this embodiment, the system control unit 14 generates control signals 104, 106, 108, and 110 in response to the operation signal 102, and supplies them to the optical system 16, the imaging unit 18, the preprocessing unit 20, and the signal processing unit 22, respectively. And control. The system control unit 14 may generate a control signal indicating a timing signal or a drive signal based on a basic clock (system clock) generated by an oscillator (not shown).

  The optical system 16 includes a lens, an aperture adjustment mechanism, a shutter mechanism, a zoom mechanism, an automatic focus adjustment mechanism, and an automatic exposure adjustment mechanism, although a specific configuration is not illustrated, and may include an infrared cut filter and an optical low-pass filter. Good. The optical system 16 is a light incident mechanism that operates in accordance with the control signal 104 supplied from the system control unit 14 and captures a desired object scene image and enters the imaging unit 18.

  Although a specific configuration is not illustrated, the imaging unit 18 includes an imaging surface that forms one screen of a captured image, and displays an object scene image formed on the imaging surface via the optical system 16 as a system control unit. 14 has a function of performing photoelectric conversion to an analog image signal 112 in accordance with a control signal 106 from 14. The imaging unit 18 of the present embodiment may be an image sensor such as a charge coupled device or a metal oxide semiconductor.

  The imaging surface of the imaging unit 18 is formed by arranging a plurality of photosensitive units in the row and column directions, for example, may be arranged in a square matrix at a certain pitch in the row direction and the column direction, Alternatively, every other position may be shifted in the row direction and the column direction. Each photosensitive portion is formed to include an optical sensor such as a photodiode that photoelectrically converts received incident light to obtain a signal charge corresponding to the amount of incident light. Each photosensitive portion is formed with a color filter of any of the three primary colors red, green, and blue, and a red photosensitive portion, a green photosensitive portion, and a blue photosensitive portion are formed, respectively.

  The red photosensitive portion, the green photosensitive portion, and the blue photosensitive portion respectively obtain red data, green data, and blue data that indicate signal charges corresponding to the amount of incident light by photoelectric conversion. An analog image signal 112 including data, green data and blue data is generated.

  The pre-processing unit 20 is controlled by the control signal 108 from the system control unit 14, performs analog signal processing on the analog image signal 112 by a circuit such as a correlated double sampling circuit and a gain control amplifier, and further performs analog / digital ( An analog / digital (A / D) converter quantizes the signal level of the analog image signal 112 with a predetermined quantization level, converts it into a digital image signal 114, and outputs it.

  In addition, the preprocessing unit 20 of this embodiment processes the analog image signal 112 for each of red data, green data, and blue data, and generates a digital image signal 114 that includes red data, green data, and blue data, respectively. .

  The signal processing unit 22 performs digital signal processing on the digital image signal 114 supplied from the preprocessing unit 20 in accordance with the control signal 110 supplied from the system control unit 14, and although not shown, A digital image signal is stored in a memory. The signal processing unit 22 performs digital signal processing such as offset correction, white balance (WB) correction, synchronization processing, linear matrix processing, gamma conversion (correction) and YC conversion on the digital image signal 114, for example. It's okay.

  In the present embodiment, the signal processing unit 22 corrects the digital image signal 114 by the average value deviation correction unit 24, and corrects the average value deviation caused by the noise clip. The correction unit 24 may be installed in front of each digital signal processing in the signal processing unit 22 to correct the average value deviation in the digital image signal 114 after the A / D conversion of the preprocessing unit 20.

  As shown in FIG. 4, the average value deviation correction unit 24 includes a red data correction unit 30, a green data correction unit 32, and a blue data correction unit 34, and the red data 140 and the green data 142 in the digital image signal 114, respectively. And the average value deviation of the blue data 144 is corrected. These correction units 30, 32, and 34 have, for example, a look-up table (LUT) for luminance-dependent offset correction, and a red LUT, green data corresponding to red data, green data, and blue data, respectively. And a blue LUT. For example, the red data correction unit 30 corrects the red data 140 by applying a red LUT.

  In this embodiment, the red data correction unit 30, the green data correction unit 32, and the blue data correction unit 34 use the luminance-dependent offset correction LUT 160, so that an output signal corresponding to the input signal level is obtained as shown in FIG. A level is output, and an output signal level of 0 is obtained for input signal levels from 0 to a predetermined low-brightness clip level 162. The correction units 30, 32, and 34 gradually increase from 0 with respect to the input signal level from the clip level 162 to the predetermined low-brightness match level 164, and the same as the input signal level from the match level 164. An output signal level that becomes a level is obtained. The correction units 30, 32, and 34 gradually increase from the input signal level to the input signal level from the predetermined high-brightness matching level 166 to the predetermined high-brightness clip level 168. Thus, an output signal level from the clip level 168 to a predetermined maximum signal level 170 is obtained.

  For example, the luminance-dependent offset correction LUT 160 may indicate an output offset corresponding to the input signal level as shown in FIG. 6, and by subtracting the corresponding output offset from a predetermined input signal level, the luminance offset offset correction LUT 160 is changed to that shown in FIG. The output signal level shown is obtained.

  In this luminance-dependent offset correction LUT 160, the output offset indicates an output offset equivalent to the corresponding input signal level with respect to the input signal level from 0 to a predetermined low luminance clip level 162. To an input signal level up to a predetermined low-brightness matching level 164, the output offset gradually decreases to indicate 0 from the matching level 164.

  Further, in this LUT 160, the output offset gradually decreases from 0 with respect to the input signal level from the predetermined high-intensity matching level 166 to the predetermined high-intensity clip level 168. , Corresponding input signal level—denotes a value obtained at a predetermined maximum signal level 170.

  Further, the red data correction unit 30, the green data correction unit 32, and the blue data correction unit 34 are functions that can obtain the same output signal level as the LUT 160 for luminance-dependent offset correction shown in FIG. The average value deviation of the red data 140, the green data 142, and the blue data 144 may be corrected using a red function, a green function, and a blue function, respectively.

  Further, the average value deviation correction unit 24 may be configured to include only one correction unit that corrects data by using a LUT or a function of luminance dependent offset correction. As shown in FIG. 3, the average values 126, 128, and 130 of the noise clipped red data, green data, and blue data are floated in the low luminance region and sunk in the high luminance region. The mean value 126 floats and sinks compared to the mean values 128 and 130 for the green and blue data. In this case, if the average value deviation correction unit 24 includes only one red data correction unit 30, not only the red data 140 but also the average value deviation of the green data 142 and the blue data 144 can be corrected.

  On the other hand, the red data correction unit 30, the green data correction unit 32, and the blue data correction unit 34 may have luminance dependent gain correction LUTs as a red LUT, a green LUT, and a blue LUT, respectively. Also in this case, the average value deviation correction unit 24 includes only one correction unit that corrects data using a luminance-dependent gain correction LUT or function, and includes, for example, only one red data correction unit 30. May be.

  As shown in FIG. 7, the luminance-dependent gain correction LUT 180 indicates an output gain corresponding to an input signal level. By multiplying an output gain corresponding to a predetermined input signal level, the LUT 180 shown in FIG. An output signal level indicative of the linear average value 124 is obtained.

  In this luminance-dependent gain correction LUT 180, the output gain gradually increases from 0 to 1 with respect to the input signal level from 0 to a predetermined low luminance clip level 182, and the predetermined high luminance clip level. For input signal levels from 184 to a predetermined maximum limit value 186, the output gain gradually increases from 1 to a predetermined maximum gain 188.

  In addition, the red data correction unit 30, the green data correction unit 32, and the blue data correction unit 34 use the same output gain as that of the LUT 180 for luminance-dependent gain correction shown in FIG. The average value deviation of the red data 140, the green data 142, and the blue data 144 may be corrected using the function, the green function, and the blue function, respectively.

  Further, the average value deviation correction unit 24 has a multidimensional LUT for luminance-dependent offset correction or gain correction, and corrects each of the red data 140, the green data 142, and the blue data 144 by applying the multidimensional LUT. May be. As described above, when correcting red data, green data, and blue data of the three primary colors, the multidimensional LUT may be three-dimensional.

  The average value deviation correction unit 24 may be installed after YC conversion of the red data 140, the green data 142, and the blue data 144 in the signal processing unit 22, and includes a luminance channel (Y) and a color difference channel (Cr, Cb). Make corrections every time. For example, the average value deviation correction unit 24 using a multidimensional LUT corrects each of the luminance data and the color difference data by applying the multidimensional LUT. As described above, when correcting data represented by luminance and color difference, the multi-dimensional LUT may be one-dimensional to correct only luminance data, and may correct the luminance data to 0, that is, close to black.

As another example, as shown in FIG. 8, the signal processing unit 22 of the apparatus 10
In accordance with the red data 210, green data 212, and blue data 214 after the WB correction by the WB correction unit 202, the color reproduction coefficient determination unit 206 determines the color reproduction coefficient 240 used in the linear matrix processing unit 204.

  The linear matrix processing unit 204 of the present embodiment may be installed behind the WB correction unit 202 and may include a color reproduction coefficient determination unit 206. The linear matrix processing unit 204 inputs red data 220, green data 222, and blue data 224 after WB correction.

  The linear matrix processing unit 204 performs a matrix operation on the red data 220, the green data 222, and the blue data 224 using a predetermined color reproduction coefficient 240 such as a linear matrix coefficient of a 3 × 3 matrix, for example, to improve color reproducibility. Red data 230, green data 232, and blue data 234 are generated.

  The color reproduction coefficient determination unit 206 of the present embodiment determines the red data 220, the green data 222, and the blue data 224 using a predetermined threshold, and determines a predetermined color reproduction coefficient 240 according to the determination result.

  In this determination, the color reproduction coefficient determination unit 206 determines that, for example, the red data 220, the green data 222, and the blue data 224 are less than a predetermined threshold value, or the red data 220, the green data 222, and the blue data 224 have low luminance. When gray is indicated, an existing color reproduction coefficient 240 having luminance as shown in the following formula (1) is selected, and in other cases, a normal color reproduction coefficient 240 as shown in the following formula (2) is selected. Select and confirm.

  The linear matrix processing unit 204 corrects magenta gray image data to an achromatic color by matrix calculation of the red data 220, green data 222, and blue data 224 using the existing color reproduction coefficient 240 of luminance. can do.

  In the present embodiment, the WB correction unit 202 is a digital image signal 114, for example, for red data 210, green data 212, and blue data 214 after offset correction, respectively, for red WB gain and green data. The red data 220, the green data 222, and the blue data 224 may be generated by multiplying the WB gain and the blue WB gain.

As another example, as shown in FIG.
In accordance with the red WB gain 320, the green WB gain 322, and the blue WB gain 324 of the WB correction unit 202, the gamma function determination unit 304 determines the gamma function 330 used in the gamma correction unit 302.

  The gamma correction unit 302 of the present embodiment may be installed behind the linear matrix processing unit 204 and may include a gamma function determination unit 304. The gamma correction unit 302 inputs red data 230, green data 232, and blue data 234 after linear matrix processing.

  The gamma correction unit 302 performs gamma correction on the red data 230, the green data 232, and the blue data 234 using a predetermined gamma function 330 to generate red data 310, green data 312, and blue data 314.

  The gamma function determination unit 304 according to the present exemplary embodiment uses a red gamma function, a green gamma function, and a blue gamma function 330 as predetermined gamma functions 330 according to the red WB gain 320, the green WB gain 322, and the blue WB gain 324. Each gamma function is determined.

  According to each WB gain in the WB correction unit 202, it is possible to predict almost uniquely how much the noise clip causes the average value of each channel. The gamma function determination unit 304 determines whether or not a luminance-dependent gamma function is necessary according to the prediction result. When a luminance-dependent gamma function is required, the gamma function determining unit 304 adjusts the original gamma function 340 to reduce the correction amount in the low luminance region, for example, as shown in FIG. It is possible to generate a luminance-dependent gamma function 342 that corrects the coloring phenomenon due to the noise clip. Further, the gamma function determination unit 304 may generate the luminance-dependent gamma function 342 not only in the low luminance region but also in the high luminance region.

  The gamma function determining unit 304 may calculate, for example, a red gamma function, a green gamma function, and a blue gamma function based on the red WB gain 320, the green WB gain 322, and the blue WB gain 324, The red gamma function corresponding to the red WB gain 320, green WB gain 322 and blue WB gain 324, green A gamma function for blue and a gamma function for blue may be selected.

  On the other hand, when a luminance-dependent gamma function is required, the gamma function determination unit 304 generates a luminance-dependent gamma function 344 by flare correcting the low luminance region of the original gamma function 340, for example, as shown in FIG. May be. The gamma function determination unit 304 may generate the luminance-dependent gamma function 344 not only in the low luminance region but also in the high luminance region.

  The gamma correction unit 302 performs gamma correction on the red data 230, the green data 232, and the blue data 234 using the gamma function for red, the gamma function for green, and the gamma function for blue as the luminance-dependent gamma function 342 or 344. The red data 310, the green data 312 and the blue data 314 can be generated by correcting the deviation of the average value caused by the noise clip.

  Further, the signal processing unit 22 of the imaging device 10 of the present invention corrects the deviation of the average value of the low luminance side and the high luminance side of the image signal, that is, the average value deviation correction unit 24 and the color reproduction coefficient determination unit 206. The respective methods in the linear matrix processing unit 204 to be used and the gamma correction unit 302 to use the gamma function determination unit 304 may be applied to other image processing apparatuses and software.

It is a block diagram which shows one Example of the imaging device which concerns on this invention. 2 is a graph illustrating clip processing on a low luminance side of an image signal captured by the imaging apparatus of the embodiment illustrated in FIG. 1. 2 is a graph conceptually showing an average value after clip processing of an image signal taken by the imaging apparatus of the embodiment shown in FIG. 1. It is a block diagram which shows the average value deviation correction | amendment part in the imaging device of the Example shown in FIG. 5 is a graph conceptually showing the relationship between input and output image data in the average value deviation correction unit shown in FIG. 4. 5 is a graph conceptually showing a LUT for luminance-dependent offset correction used in the average value deviation correction unit shown in FIG. 4. 5 is a graph conceptually showing a LUT for luminance dependent gain correction used in the average value deviation correction unit shown in FIG. 4. It is a block diagram which shows the other Example of the signal processing part in the imaging device which concerns on this invention. It is a block diagram which shows the other Example of the signal processing part in the imaging device which concerns on this invention. It is the graph which showed notionally the gain function used with the gain function determination part shown in FIG. It is the graph which showed notionally the gain function used with the gain function determination part shown in FIG.

Explanation of symbols

10 Imaging device
12 Operation unit
14 System controller
16 optics
18 Imaging unit
20 Pre-processing section
22 Signal processor
24 Average value deviation correction section

Claims (15)

In an imaging apparatus including a signal processing means for performing signal processing on an image signal that has been picked up by a noise clip process on a low-luminance side and a high-luminance side, showing a captured scene image
It said signal processing means providing a lookup table or a function of the brightness-dependent offset correction or gain correction for each of a plurality of color channels, by using the look-up table or function the image signal for each of the plurality of color channels An image pickup apparatus comprising: an average value deviation correcting unit that corrects and corrects an average value deviation caused by the noise clip process.   The imaging apparatus according to claim 1, wherein the average value deviation correcting unit corrects the image signal for each of three primary colors of a red channel, a green channel, and a blue channel.   The imaging apparatus according to claim 1, wherein the average value deviation correction unit corrects the image signal for each luminance channel and color difference channel. The imaging apparatus according to claim 2, wherein the average deviation correcting means, as a look-up table of the luminance-dependent offset correction or gain correction, look-up tables for red corresponding to the red channel, green channel and blue channel, An image pickup apparatus that corrects red data, green data, and blue data in the image signal using a green lookup table and a blue lookup table, respectively.   5. The imaging device according to claim 4, wherein the average value deviation correction unit has a predetermined low luminance as the red lookup table, the green lookup table, and the blue lookup table for luminance dependent offset correction. For input image data up to the clip level, output image data indicating 0 is output, and for input image data from a predetermined high-intensity clip level, output indicating a predetermined maximum limit is output. An imaging apparatus using a look-up table for outputting image data. The imaging apparatus according to claim 2, wherein the average deviation correcting means, as a function of the offset correction or gain correction of the brightness-dependent, red function corresponding to the red channel, green channel and blue channel, green functions and An image pickup apparatus that corrects red data, green data, and blue data in the image signal by using a blue function. 7. The imaging apparatus according to claim 6 , wherein the average value deviation correction unit is configured to input an input up to a predetermined low luminance clip level as the red function, the green function, and the blue function for luminance dependent offset correction. A function for outputting output image data indicating 0 for image data, and outputting output image data indicating a predetermined maximum limit for image data input from a predetermined high-intensity clip level An imaging device characterized by using the above. In a signal processing method for performing signal processing on an image signal obtained by performing noise clip processing on a low-luminance side and a high-luminance side, showing a captured scene image,
The signal processing method includes providing a lookup table or a function of the brightness-dependent offset correction or gain correction for each of a plurality of color channels, by using the look-up table or function the image signal for each of the plurality of color channels A signal processing method comprising an average value deviation correction step of correcting and correcting an average value deviation caused by the noise clip process. 9. The signal processing method according to claim 8 , wherein the average value deviation correction step corrects the image signal for each of the three primary color red channels, green channels, and blue channels. 9. The signal processing method according to claim 8 , wherein the average value deviation correction step corrects the image signal for each luminance channel and color difference channel. The signal processing method according to claim 9, wherein the average deviation correcting step, as a look-up table of the luminance-dependent offset correction or gain correction, the red channel, the look-up table for red corresponding to the green and blue channels A signal processing method for correcting red data, green data, and blue data in the image signal using a green lookup table and a blue lookup table, respectively. 12. The signal processing method according to claim 11 , wherein the average value deviation correction step includes a predetermined low luminance as the red lookup table, the green lookup table, and the blue lookup table for luminance dependent offset correction. The output image data indicating 0 is output for the input image data up to the clip level, and the output indicating the predetermined maximum limit is output for the input image data from the predetermined high-intensity clip level. A signal processing method using a look-up table for outputting the image data. The signal processing method according to claim 9, wherein the average deviation correcting step, as a function of the offset correction or gain correction of the brightness-dependent, the red channel, red function corresponding to the green and blue channels, the function for green And a blue function, respectively, to correct red data, green data, and blue data in the image signal. 14. The signal processing method according to claim 13 , wherein the average value deviation correction step includes inputting up to a predetermined low luminance clip level as the red function, the green function, and the blue function for luminance dependent offset correction. Output image data indicating 0 is output, and output image data indicating a predetermined maximum limit is output for input image data from a predetermined high-intensity clip level. A signal processing method using a function. 9. The signal processing method according to claim 8 , wherein the average value deviation correction step is performed by software to which the average value deviation correction step is applied.