Patent Publication Number: US-11647305-B2

Title: Solid-state imaging apparatus, signal processing method of solid-state imaging apparatus and electronic device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present disclosure contains subject matter related to Japanese Patent Application JP 2020-215183 filed in the Japan Patent Office on Sep. 26, 2017, the entire contents of which being incorporated herein by reference. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a solid-state imaging apparatus, a signal processing method of the solid-state imaging apparatus and an electronic device, and more particularly to a solid-state imaging apparatus, a signal processing method of the solid-state imaging apparatus and an electronic device that can be used for correcting pixel sensitivities. 
     2. Description of Related Art 
     Complementary metal oxide semiconductor (CMOS) sensors have been provided for practical use as solid-state imaging apparatus (e.g., image sensors). A solid-state imaging apparatus is a photoelectric conversion component that detects light and generates electric charges. 
     A CMOS image sensor generally uses three primary color filters (e.g., red (R), green (G) and blue (B)) or 4-color complementary color filters (e.g., cyan, magenta, yellow and green) to take color images. 
     Generally speaking, in a CMOS image sensor, a pixel is individually equipped with a color filter. The filter includes a red (R) filter that mainly transmits red light, a green (Gr, Gb) filter that mainly transmits green light and a blue (B) filter that mainly transmits blue light. Pixel units containing color filters are arranged squarely to form a pixel group. Multiple pixel groups are arranged in a two-dimensional manner to form a pixel portion (i.e., a pixel array). Such color filter arrangement is widely known as a Bayer pattern. In addition, for example, a microlens is configured to correspond each pixel. Moreover, a CMOS image sensor in which a plurality of pixels with the same color are arranged in a Bayer pattern has also been provided to achieve high sensitivity or high dynamic range (e.g., referring to Patent Documents 1 and 2). 
     Such a CMOS image sensor has been widely used as a part of an electronic device such as a digital camera, a video camera, a surveillance camera, a medical endoscope, a personal computer (PC), a mobile terminal apparatus (e.g., a mobile phone or a mobile device), etc. 
     Especially in recent years, the miniaturization and multi-pixelization of an image sensor mounted on a mobile terminal apparatus (e.g., a mobile phone or a mobile device) have continued to progress. The pixel size has also shrunk to a size of 1 μm and has gradually become the mainstream. In order to maintain the high resolution formed by the multiple pixels, the reduction of pixel pitch leads to a decrease in sensitivity or dynamic range. Generally, multiple adjacent pixels with the same color (e.g., 4 pixels) are arranged. When resolution is required, individual pixel signals are read. When high sensitivity or dynamic rang performance is required, the signals of pixels with the same color are added together for reading. Further, such a CMOS image sensor includes, for example, a plurality of pixels with the same color and adjacent to the pixel unit and sharing a microlens. 
     In a solid-state imaging apparatus (e.g., a CMOS image sensor) that includes a plurality of pixels sharing a microlens, the solid-state imaging apparatus can have distance information in the pixels, and has a phase detection auto focus (PDAF) function. On the other hand, in such a CMOS image sensor, since PDAF pixels are formed in the same color in the pixel array, the sensitivities of these PDAF pixels must be corrected in a normal shooting mode. 
     In order to perform the correction, for example, a correction method using the difference between averages of adjacent pixels with the same color has been provided (e.g., referring to Patent Documents 3 and 4). 
     CITATION LIST 
     Patent Literature 
     Patent Document 1: Japanese Patent Application Publication No. 1999-298800 
     Patent Document 2: Japanese Patent Application No. 5471117 
     Patent Document 3: Japanese Patent Application No. 6369233 
     Patent Document 4: U.S. Pat. No. 9,918,031 B2 
     SUMMARY 
     Problems to be Solved by the Present Disclosure 
     However, according to the correction method using the difference between averages of adjacent pixels with the same color as described in Patent Documents 3 and 4, since the range of pixels to be correction targets is limited to pixels with the same color in the same pixel unit, the correction methods thereof are also limited. Hence, it is difficult to correct uneven sensitivity generated by the color unevenness in a broader range or uneven sensitivity generated by multiple factors. Accordingly, the correction methods described in Patent Documents 3 and 4 using the difference between averages of adjacent pixels with the same color are further explained as follows. 
       FIG.  1    is a diagram showing an example of a pixel group formed as a pixel array of a solid-state imaging apparatus (a CMOS image sensor) as an RGB sensor using a correction method of the difference between averages of adjacent pixels with the same color. 
     The pixel group  1  in  FIG.  1    is formed by a pixel unit PU 1  with Gr pixels, a pixel unit PU 2  with R pixels, a pixel unit PU 3  with B pixels and a pixel unit PU 4  with Gb pixels arranged in a Bayer pattern. The pixel unit PU 1  is arranged with a plurality of adjacent pixels (e.g., 2×2=4) PXGrA, PXGrB, PXGrC and PXGrD with the same color (Gr). In the pixel unit PU 1 , a microlens MCL 1  is configured to correspond to the 4 pixels PXGrA, PXGrB, PXGrC and PXGrD. 
     The pixel unit PU 2  is arranged with a plurality of adjacent pixels (e.g., 2×2=4) PXRA, PXRB, PXRC and PXRD with the same color (R). In the pixel unit PU 2 , a microlens MCL 2  is configured to correspond to the 4 pixels PXRA, PXRB, PXRC and PXRD. The pixel unit PU 3  is arranged with a plurality of adjacent pixels (e.g., 2×2=4) PXBA, PXBB, PXBC and PXBD with the same color (B). In the pixel unit PU 3 , a microlens MCL 3  is configured to correspond to the 4 pixels PXBA, PXBB, PXBC and PXBD. The pixel unit PU 4  is arranged with a plurality of adjacent pixels (e.g., 2×2=4) PXGbA, PXGbB, PXGbC and PXGbD with the same color (Gb). In the pixel unit PU 4 , a microlens MCL 4  is configured to correspond to the 4 pixels PXGbA, PXGbB, PXGbC and PXGbD. 
     For example, when the sensitivity of the pixel PXGrA in the Gr pixel of the pixel group  1  in  FIG.  1    is to be corrected, the sensitivities of the 4 pixels PXGrA, PXGrB, PXGrC and PXGrD of the pixel unit PU 1  are set to Pa to Pd, respectively, and the sensitivities of the 4 pixels PXGbA, PXGbB, PXGbC and PXGbD of the pixel unit PU 4  adjacent to the pixel unit PU 1  in the lower right direction is set to Pe to Ph, respectively. Accordingly, a correction coefficient Sa is given as the ratio of the sensitivity Pa to the average of the sensitivity of the pixel unit according to the following equation.
 
 Sa=Pa /(( Pa+Pb+Pc+Pd )/4)  [Equation 1]
 
     As such, in the conventional correction method, the sensitivity is corrected by using the average of sensitivities of pixels with the same color in the same pixel unit. For example, when the sensitivities are uneven due to uneven localized sensitivities and other factors that extend to a broader range, the sensitivities Pe to Ph of adjacent Gb pixels PXGbA, PXGbB, PXGbC and PXGbD in  FIG.  1    cannot be used as references for correction, for example. Consequently, the conventional correction method sometimes has insufficient sensitivity correction. For example, in order to correct the sensitivity, only the sensitivity of the pixel of the pixel unit is referred to, so that it is difficult to correct defects over a plurality of pixel units or pixel groups, such as strips. 
     In addition, as described above, in order to achieve miniaturization and thinning, camera modules of mobile terminal apparatus (e.g., mobile phones or mobile devices) need to be reduced in height. In order to respond to this demand, the angle of light incident on the periphery of the angle of view of the mounted image sensor tends to increase. If it is not possible to efficiently guide the obliquely incident light in the peripheral part of the angle of view to the photoelectric conversion region (photodiode), the sensitivity difference between the peripheral part of the angle of view and the central part of the angle of view becomes large, which is called shading. Deterioration of pixel characteristics may occur. However, in the conventional correction method, it is not possible to separately correct the sensitivity decrease due to monotonous shading that occurs toward the end of the lens and the variation of individual pixels, so accurate sensitivity correction is difficult. 
     The present disclosure provides a solid-state imaging apparatus, a signal processing method of the solid-state imaging apparatus and an electronic device which are capable of correcting uneven sensitivity generated by multiple factors in a broad area such that higher-precision image quality can be achieved. The present disclosure provides a solid-state imaging apparatus, a signal processing method of the solid-state imaging apparatus and an electronic device which are capable of correcting uneven sensitivity generated by multiple factors in a broad area, and can achieve higher-precision image quality, thereby more accurately correcting uneven sensitivity in a localized area. 
     Solutions to Solve Problems 
     According to a first embodiment of the present disclosure, a solid-state imaging apparatus includes: a pixel portion having a plurality of pixel units in which each of the pixel units includes a plurality of pixels of same color for performing photoelectric conversion; and a correction circuit that corrects a pixel sensitivity of the pixel units to be a correction target with reference to an obtained correction coefficient, wherein the correction circuit weighs a sensitivity value corresponding to a pixel signal of each of the pixels related to the correction in the pixel unit to be the correction target and the sensitivity value corresponding to a pixel signal of each of the pixels related to the correction in at least one of the pixel units adjacent to the pixel unit to be the correction target by weighting coefficients, and then obtains a weighted average of weighted sensitivities so as to obtain the correction coefficient. 
     According to a second embodiment of the present disclosure, a signal processing method of a solid-state imaging apparatus is provided. The solid-state imaging apparatus includes: a pixel portion having a plurality of pixel units in which each of the pixel units includes a plurality of pixels of same color for performing photoelectric conversion; and a correction circuit that corrects a pixel sensitivity of the pixel units to be a correction target with reference to an obtained correction coefficient, wherein the correction circuit weighs a sensitivity value corresponding to a pixel signal of each of the pixel related to the correction in the pixel unit to be the correction target and a sensitivity value corresponding to a pixel signal of each of the pixels related to the correction in at least one of the pixel units adjacent to the pixel unit to be the correction target by weighting coefficients, and then obtains a weighted average of weighted sensitivity values so as to obtain the correction coefficient. 
     According to a third embodiment of the present disclosure, an electronic device includes: a solid-state imaging apparatus; and an optical system configured for imaging an object in the solid-state imaging apparatus, wherein the solid-state imaging apparatus comprises: a pixel portion having a plurality of pixel units in which each of the pixel units includes a plurality of pixels of same color for performing photoelectric conversion; and a correction circuit that corrects a pixel sensitivity of the pixel units to be a correction target with reference to an obtained correction coefficient, wherein the correction circuit weighs a sensitivity value corresponding to a pixel signal of each of the pixels related to the correction in the pixel unit to be the correction target and a sensitivity value corresponding to a pixel signal of each of the pixels related to the correction in at least one of the pixel units adjacent to the pixel unit to be the correction target by weighting coefficients, and then obtains a weighted average of weighted sensitivities so as to obtain the correction coefficient. 
     Effects of the Present Disclosure 
     The present disclosure can correct uneven sensitivities generated by multiple factors in a broad area, and can achieve higher-precision image quality. In addition, the present disclosure can correct uneven sensitivities generated by various factors in a broad area, and can achieve higher-precision image quality, thereby more accurately correcting uneven sensitivities in a localized area. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a diagram showing an example of a pixel group formed in a pixel array of a solid-state imaging apparatus (a CMOS image sensor) as an RGB sensor adopting a correction method of the difference between averages of adjacent pixels with the same color. 
         FIG.  2    is a block diagram showing a structure example of the solid-state imaging apparatus according to a first embodiment of the present disclosure. 
         FIG.  3    is a diagram showing a formation example of a pixel array in a pixel portion according to the first embodiment of the present disclosure. 
         FIG.  4    is a diagram showing an example of pixel groups forming a pixel array according to the first embodiment of the present disclosure. 
         FIG.  5    is a circuit diagram showing an example of a pixel unit in which 4 pixels of a pixel group of a solid-state imaging apparatus share a floating diffusion according to the first embodiment of the present disclosure. 
         FIG.  6    is a diagram showing an example of a correction-related region on a pixel array including a correction target pixel unit for which the correction circuit according to the first embodiment of the present disclosure acquires a correction coefficient and an adjacent pixel unit adjacent to the correction target pixel unit. 
         FIG.  7    is a diagram for explaining a first specific example of a processing for obtaining a correction coefficient according to the first embodiment of the present disclosure. 
         FIG.  8    is a diagram for explaining a second specific example of a processing for obtaining a correction coefficient according to the first embodiment of the present disclosure. 
         FIG.  9    is a diagram for explaining a third specific example of a processing for obtaining correction coefficients according to the first embodiment of the present disclosure. 
         FIG.  10    is a diagram for explaining a processing for obtaining correction coefficients according to a second embodiment of the present disclosure. 
         FIG.  11    is a diagram for explaining a first specific example of a processing for obtaining a correction coefficient according to a third embodiment of the present disclosure. 
         FIG.  12    is a diagram for explaining a second specific example of a processing for obtaining a correction coefficient according to the third embodiment of the present disclosure. 
         FIG.  13    is a diagram for explaining a third specific example of a processing for obtaining a correction coefficient according to the third embodiment of the present disclosure. 
         FIG.  14 A  to  FIG.  14 C  are diagrams for explaining a processing for obtaining correction coefficients according to a fourth embodiment of the present disclosure. 
         FIG.  15 A  to  FIG.  15 C  are diagrams for explaining a processing for obtaining correction coefficients according to a fifth embodiment of the present disclosure. 
         FIG.  16 A  and  FIG.  16 B  are diagrams for explaining a processing for obtaining correction coefficients according to a sixth embodiment of the present disclosure. 
         FIG.  17    is a diagram for explaining a processing for obtaining correction coefficients according to a seventh embodiment of the present disclosure. 
         FIG.  18    is a diagram for explaining a processing for obtaining correction coefficients according to an eighth embodiment of the present disclosure. 
         FIG.  19    a diagram for explaining a processing for obtaining correction coefficients according to a ninth embodiment of the present disclosure. 
         FIG.  20    is a diagram showing a structure example of an electronic device to which the solid-state imaging apparatus is applied according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The embodiments of the present disclosure are related to the drawings for description hereinafter. 
     First Embodiment 
       FIG.  2    is a block diagram showing a structure example of a solid-state imaging apparatus according to a first embodiment of the present disclosure. According to the embodiment, the solid-state imaging apparatus is constituted by, for example, a CMOS image sensor. 
     As shown in  FIG.  2   , the solid-state imaging apparatus  10  mainly has a pixel portion  20  including a pixel array, a vertical scanning circuit (a row scanning circuit)  30 , a reading circuit (a column reading circuit)  40 , a horizontal scanning circuit (a column scanning circuit)  50 , a timing control circuit  60  and a signal processing circuit  70 . 
     In the first embodiment, as described in detail later, the solid-state imaging apparatus  10  is having a plurality of pixel units (PUs) in the pixel portion  20 . The PU contains a plurality of pixels with the same color (PX) performing photoelectric conversion, and the signal processing circuit  70  has a correction circuit  710 . The correction circuit  710  corrects the sensitivity of the pixel PX of the PU to be the correction target and that is correlated with an obtained correction coefficient μ. 
     In the first embodiment, the correction circuit  710  weighs a sensitivity corresponding to a pixel signal of each pixel PX related to correction in the PU to be the correction target and a sensitivity corresponding to a pixel signal of each pixel related to correction in at least one same color PU adjacent to the PU to be the correction target by a weighting coefficient Wi. Accordingly, the correction coefficient μ is obtained by a weighted average of the weighted sensitivities obtained by weighting. In the first embodiment, the correction circuit  710  weighs a sensitivity corresponding to a pixel signal of each pixel PX related to correction in the PU to be the correction target and a sensitivity corresponding to a pixel signal of each pixel related to correction in at least one same color pixel unit PU adjacent to the PU to be the correction target by a weighting coefficient Wi. Consequently, the correction coefficient μ is obtained (calculated) by dividing a sum of the weighted sensitivities by a total number of pixels related to correction. 
     As such, the solid-state imaging apparatus  10  in the first embodiment is configured to be able to correct uneven sensitivities caused by multiple factors in a broad area, thereby achieving the higher-precision image quality. 
     Therefore, after describing the specific structures, arrangement, etc. of the pixel units including a plurality of pixels with the same color (in this example, 4 pixels with the same color) in the pixel portion  20  of the solid-state imaging apparatus  10  and the outline of the composition and function of each part, a method of correcting a pixel sensitivity will be described in detail later. 
     (Structure of the Pixel Array  200 , the Pixel Group PXG and the Pixel Unit PU of the Pixel Portion  20 ) 
       FIG.  3    is a diagram showing a formation example of a pixel array in a pixel portion according to the first embodiment of the present disclosure.  FIG.  4    is a diagram showing an example of pixel groups forming a pixel array according to the first embodiment of the present disclosure. 
     In the pixel portion  20 , a plurality of pixels PX including photodiodes (photoelectric conversion units) and a pixel amplifier are arranged in a two-dimensional matrix to form a pixel array  200 . 
     The pixel PX is basically composed of photodiodes and a plurality of pixel transistors. The pixel transistors include, for example, a transfer transistor, a reset transistor, a source follower transistor with an amplification function and a select transistor. However, in the first embodiment, as shown in  FIG.  4   , a 4-pixel sharing structure in which 4 pixels with the same color in a pixel unit share a floating diffusion FD is adopted. Specifically, as described in detail later, the 4 pixels share the floating diffusion FD 11 , the reset transistor RST 11 -Tr, the source follower transistor SF 11 -Tr and the select transistor SEL 11 -Tr. In addition, for example, when correcting the sensitivity of an arbitrary pixel, the shared floating diffusion FD is used as an addition unit for the pixel signals read from the plurality of pixels of the same pixel unit PU to be referred to at the time of correction to produce an additive effect. 
     As described later, the pixel array  200  in the first embodiment forms adjacent plural pixels (4 pixels in the first embodiment) with the same color as m×m (m is an integer of two or more). In the first embodiment, a 2×2 square arrangement forms a pixel unit PU. Additionally, a pixel group PXG is formed by 4 adjacent pixel units PU, and a plurality of pixel groups PXG are arranged in a matrix. In the example in  FIG.  3   , in order to simplify the drawing, a pixel array  200  in which 9 pixel groups PXG 11 , PXG 12 , PXG 13 , PXG 21 , PXG 22 , PXG 23 , PXG 31 , PXG 32  and PXG 33  are arranged in a 3×3 matrix is shown. 
     (Structure of the Pixel Group PXG and the Pixel Unit PU) 
     As shown in  FIGS.  3  and  4   , the pixel group PXG 11  is formed by a pixel unit PU 111  with Gr pixels, a pixel unit PU 112  with R pixels, a pixel unit PU 113  with B pixels and a pixel unit PU 114  with Gb pixels arranged in a Bayer pattern. The pixel group PXG  12  is formed by the pixel unit PU 121  with Gr pixels, the pixel unit PU  122  with R pixels, the pixel unit PU  123  with B pixels and the pixel unit PU  124  with Gb pixels arranged in a Bayer pattern. The pixel group PXG  13  is formed by the pixel unit PU  131  with Gr pixels, the pixel unit PU  132  with R pixels, the pixel unit PU  133  with B pixels and the pixel unit PU  134  with Gb pixels arranged in a Bayer pattern. 
     The pixel group PGX 21  is formed by the pixel unit PU 211  with Gr pixels, the pixel unit PU 212  with R pixels, the pixel unit PU 213  with B pixels and the pixel unit PU 214  with Gb pixels arranged in a Bayer pattern. The pixel group PGX 22  is formed by the pixel unit PU 221  with Gr pixels, the pixel unit PU 222  with R pixels, the pixel unit PU 223  with B pixels and the pixel unit PU 224  with Gb pixels arranged in a Bayer pattern. The pixel group PGX 23  is formed by the pixel unit PU 231  with Gr pixels, the pixel unit PU 232  with R pixels, the pixel unit PU 233  with B pixels and the pixel unit PU 234  with Gb pixels arranged in a Bayer pattern. 
     The pixel group PGX 31  is formed by the pixel unit PU 311  with Gr pixels, the pixel unit PU 312  with R pixels, the pixel unit PU 313  with B pixels and the pixel unit PU 314  with Gb pixels arranged in a Bayer pattern. The pixel group PGX 32  is formed by the pixel unit PU 321  with Gr pixels, the pixel unit PU 322  with R pixels, the pixel unit PU 323  with B pixels and the pixel unit PU 324  with Gb pixels arranged in a Bayer pattern. The pixel group PGX 33  is formed by the pixel unit PU 331  with Gr pixels, the pixel unit PU 332  with R pixels, the pixel unit PU 333  with B pixels and the pixel unit PU 334  with Gb pixels arranged in a Bayer pattern. 
     As a result, the pixel groups PXG 11 , PXG 12 , PXG 13 , PXG 21 , PXG 22 , PXG 23 , PXG 31 , PXG 32  and PXG 33  have the same structure and are arranged in a matrix in a repetitive manner. The pixel units constituting a pixel group also have the same structure as a pixel group. Therefore, the pixel units PU 111 , PU 112 , PU 113  and PU 114  forming the pixel group PXG 11  are described here as a representative example. 
     The pixel unit PU 111  is configured with a plurality of adjacent 4 pixels PXGr-A, PXGr-B, PXGr-C and PXGr-D with the same color (Gr), for example, 2×2 pixels. In the pixel unit PU 111 , a microlens MCL 111  is configured to correspond to 4 pixels PXGr-A, PXGr-B, PXGr-C and PXGr-D. 
     The pixel unit PU 112  is configured with a plurality of adjacent 4 pixels PXR-A, PXR-B, PXR-C and PXR-D with the same color (R), for example, 2×2 pixels. In the pixel unit PU 112 , a microlens MCL 111  is configured to correspond to 4 pixels PXR-A, PXR-B, PXR-C and PXR-D. 
     The pixel unit PU 113  is configured with a plurality of adjacent 4 pixels PXB-A, PXB-B, PXB-C and PXB-D with the same color (B), for example, 2×2 pixels. In the pixel unit PU 113 , a microlens MCL 113  is configured to correspond to 4 pixels PXB-A, PXB-B, PXB-C and PXB-D. 
     The pixel unit PU 114  is configured with a plurality of adjacent 4 pixels PXGb-A, PXGb-B, PXGb-C and PXGb-D with the same color (Gb), for example, 2×2 pixels. In the pixel unit PU 114 , a microlens MCL 114  is configured corresponding to 4 pixels PXGb-A, PXGb-B, PXGb-C and PXGb-D. 
     The other pixel groups PXG 12 , PXG 13 , PXG 21 , PXG 22 , PXG 23 , PXG 31 , PXG 32  and PXG 33  also have the same structure as the above-mentioned pixel group PXG 11 . 
     Moreover, as described in detail later, in the first embodiment, the correction circuit  710  weighs a sensitivity corresponding to a pixel signal of each pixel PX related to correction in the PU to be the correction target and a sensitivity corresponding to a pixel signal of each pixel related to correction in at least one same color PU adjacent to the PU to be the correction target by a weighting coefficient Wi. Accordingly, the correction coefficient μ is obtained by a weighted average of the weighted sensitivities obtained by weighting. As described in detail later, the correction coefficient μ is obtained by dividing the weighted sensitivities by a total number of pixels related to correction. In addition, in association with the pixel array of  FIG.  3   , a description is given of a plurality of examples of at least one same color (Gr or Gb) pixel unit (PU) adjacent to the pixel unit (PU) of the Gr or Gb pixels that is the correction target. 
     For example, when it is necessary to correct the sensitivity (or color difference signal level) of any one of the 4 Gb pixels of the pixel unit PU 114  of the pixel group PXG 11 , the 4 Gb pixels of the pixel unit PU 114  are adjacent to the pixel units with the same color as that of the pixel unit PU 114  to be the correction target, that is, the pixel unit PU 111  on the upper left side, the pixel unit PU 121  on the upper right side, the pixel unit PU 211  on the lower left side and the pixel unit PU 221  on the lower right side are relative to the pixel unit PU 114  to be the correction target. Basically, the correction refers to the read value of each pixel PX (the sensitivity corresponding to the pixel signal) of the pixel unit PU 114  containing the pixels that are the correction targets, and also refers to the read value of each pixel (the sensitivity corresponding to the pixel signal) of at least one of the pixel units PU 111 , PU 121 , PU 211  and PU 221 . 
     When it is necessary to correct the sensitivity (or color difference signal level) of any one of the 4 Gb pixels of the pixel unit PU 124  of the pixel group PXG 12 , the 4 Gb pixels of the pixel unit PU 124  are adjacent to the pixel units with the same color as that of the pixel unit PU 124  to be the correction target, that is, the pixel unit PU 121  on the upper left side, the pixel unit PU 131  on the upper right side, the pixel unit PU 221  on the lower left side and the pixel unit PU 231  on the lower right side are relative to the pixel unit PU 124  to be the correction target. Basically, the correction refers to the read value of each pixel PX (the sensitivity corresponding to the pixel signal) of the pixel unit PU 214  containing the pixels that are the correction targets, and also refers to the read value of each pixel (the sensitivity corresponding to the pixel signal) of at least one of the pixel units PU 121 , PU 131 , PU 231  and PU 231 . 
     When it is necessary to correct the sensitivity (or color difference signal level) of any one of the 4 Gr pixels of the pixel unit PU 221  of the pixel group PXG 22 , the 4 Gr pixels of the pixel unit PU 221  are adjacent to the pixel units with the same color as that of the pixel unit PU 221  to be the correction target, that is, the pixel unit PU 114  on the upper left side, the pixel unit PU 124  on the upper right side, the pixel unit PU 214  on the lower left side and the pixel unit PU 224  on the lower right side are relative to the pixel unit PU 221  to be the correction target. Basically, the correction refers to the read value of each pixel PX (the sensitivity corresponding to the pixel signal) of the pixel unit PU 221  containing the pixel that is the correction target, and also refers to the read value of each pixel (the sensitivity corresponding to the pixel signal) of at least one of the pixel units PU 114 , PU 124 , PU 214  and PU 224 . 
     When it is necessary to correct the sensitivity (or color difference signal level) of any one of the 4 Gr pixels of the pixel unit PU 231  of the pixel group PXG 23 , the 4 Gb pixels of the pixel unit PU 231  are adjacent to the pixel units with the same color as that of the pixel unit PU 231  to be the correction target, that is, the pixel unit PU 124  on the upper left side, the pixel unit PU 134  on the upper right side, the pixel unit PU 224  on the lower left side and the pixel unit PU 234  on the lower right side are relative to the pixel unit PU 221  to be the correction target. Basically, the correction refers to the read value of each pixel PX (the sensitivity corresponding to the pixel signal) of the pixel unit PU 231  containing the pixels that are the correction targets, and also refers to the read value of each pixel (the sensitivity corresponding to the pixel signal) of at least one of the pixel units PU 124 , PU 134 , PU 224  and PU 234 . 
     When it is necessary to correct the sensitivity (or color difference signal level) of any one of the 4 Gb pixels of the pixel unit PU 214  of the pixel group PXG 21 , the 4 Gb pixels of the pixel unit PU 214  are adjacent to the pixel units with the same color as that of the pixel unit PU 214  to be the correction target, that is, the pixel unit PU 211  on the upper left side, the pixel unit PU 221  on the upper right side, the pixel unit PU 311  on the lower left side and the pixel unit PU 321  on the lower right side are relative to the pixel unit PU 214  to be the correction target. Basically, the correction refers to the read value of each pixel PX (the sensitivity corresponding to the pixel signal) of the pixel unit PU 214  containing the pixels that are the correction targets, and also refers to the read value of each pixel (the sensitivity corresponding to the pixel signal) of at least one of the pixel units PU 211 , PU 221 , PU 311  and PU 321 . 
     When it is necessary to correct the sensitivity (or color difference signal level) of any one of the 4 Gb pixels of the pixel unit PU 224  of the pixel group PXG 22 , the 4 Gb pixels of the pixel unit PU 224  are adjacent to the pixel units with the same color as that of the pixel unit PU 224  to be the correction target, that is, the pixel unit PU 221  on the upper left side, the pixel unit PU 231  on the upper right side, the pixel unit PU 321  on the lower left side and the pixel unit PU 331  on the lower right side are relative to the pixel unit PU 224  to be the correction target. Basically, the correction refers to the read value of each pixel PX (the sensitivity corresponding to the pixel signal) of the pixel unit PU 224  containing the pixels that are the correction targets, and also refers to the read value of each pixel (the sensitivity corresponding to the pixel signal) of at least one of the pixel units PU 221 , PU 231 , PU 321  and PU 331 . 
     When it is necessary to correct the sensitivity (or color difference signal level) of any one of the 4 Gr pixels of the pixel unit PU 321  of the pixel group PXG 32 , the 4 Gb pixels of the pixel unit PU 321  are adjacent to the pixel units with the same color as that of the pixel unit PU 321  to be the correction target, that is, the pixel unit PU 214  on the upper left side, the pixel unit PU 224  on the upper right side, the pixel unit PU 314  on the lower left side and the pixel unit PU 324  on the lower right side are relative to the pixel unit PU 321  to be the correction target. Basically, the correction refers to the read value of each pixel PX (the sensitivity corresponding to the pixel signal) of the pixel unit PU 321  containing the pixels that are the correction targets, and also refers to the read value of each pixel (the sensitivity corresponding to the pixel signal) of at least one of the pixel units PU 214 , PU 224 , PU 314  and PU 324 . 
     When it is necessary to correct the sensitivity (or color difference signal level) of any one of the 4 Gr pixels of the pixel unit PU 331  of the pixel group PXG 33 , the 4 Gb pixels of the pixel unit PU 331  are adjacent to the pixel units with the same color as that of the pixel unit PU 331  to be the correction target, that is, the pixel unit PU 224  on the upper left side, the pixel unit PU 234  on the upper right side, the pixel unit PU 324  on the lower left side and the pixel unit PU 334  on the lower right side are relative to the pixel unit PU 331  to be the correction target. Basically, the correction refers to the read value of each pixel PX (the sensitivity corresponding to the pixel signal) of the pixel unit PU 321  containing the pixels that are the correction targets, and also refers to the read value of each pixel (the sensitivity corresponding to the pixel signal) of at least one of the pixel units PU 324 , PU 234 , PU 324  and PU 334 . 
     As described above, in the first embodiment, as shown in  FIG.  4   , a 4-pixel sharing structure in which 4 pixels with the same color in a pixel unit share a floating diffusion FD is adopted. Hence, a structure example in which 4 pixels with the same color in a pixel unit share a floating diffusion FD is described as follows. 
     (Structure Example of Sharing 4 Pixels of the Pixel Unit) 
       FIG.  5    is a circuit diagram showing an example of a pixel unit in which 4 pixels of a pixel group of a solid-state imaging apparatus share a floating diffusion according to the first embodiment of the present disclosure. 
     In the pixel portion  20  of  FIG.  5   , the pixel unit PU of the pixel group PXG consists of 4 pixels (color pixels in the embodiment, G pixels herein), that is, a first color pixel PX 11 , a second color pixel PX 12 , a third color pixel PX 21  and a fourth color pixel PX 22  are arranged in a 2×2 square. 
     The first color pixel PX 11  is composed of a photodiode PD 11  formed by a first photoelectric conversion region and a transfer transistor TG 11 -Tr. 
     The second color pixel PX 12  is composed of a photodiode PD 12  formed by the second photoelectric conversion region and a transfer transistor TG 12 -Tr. 
     The third color pixel PX 13  is composed of a photodiode PD 21  formed by the third photoelectric conversion region and a transfer transistor TG 21 -Tr. 
     The fourth color pixel PX 22  is composed of a photodiode PD 22  and a transfer transistor TG 22 -Tr. 
     In addition, the pixel group PXG formed by the pixel units PU includes 4 color pixels PX 11 , PX 12 , PX 21  and PX 22  sharing the floating diffusion FD 11 , a reset transistor RST 11 -Tr, a source follower transistor SF 11 -Tr and a select transistor SEL 11 -Tr. 
     In the 4-pixel sharing structure, for example, the first color pixel PX 11 , the second color pixel PX 12 , the third color pixel PX 21  and the fourth color pixel PX 22  are formed in the same color to form G (Gr, Gb (green)) pixels. For example, the photodiode PD 11  of the first color pixel PX 11  functions as a first green (G) photoelectric conversion unit. The photodiode PD 12  of the second color pixel PX 12  functions as a second green (G) photoelectric conversion unit. The photodiode PD 21  of the third color pixel PX 21  functions as a third green (G) photoelectric conversion unit. The photodiode PD 22  of the fourth color pixel PX 22  functions as a fourth green (G) photoelectric conversion unit. 
     For the photodiodes PD 11 , PD 12 , PD 21  and PD 22 , for example, embedded photodiodes (PPD) are used. Since there are surface levels caused by defects such as dangling bonds on the surface of the substrate on which the photodiodes PD 11 , PD 12 , PD 21  and PD 22  are formed, a lot of charges (dark current) are generated due to thermal energy such that correct signals cannot be read. In an embedded photodiode (PPD), by embedding the charge storage part of the photodiode PD in the substrate, it is possible to reduce dark current mixed into a signal. 
     The photodiodes PD 11 , PD 12 , PD 21  and PD 22  generate and accumulate signal charges (electrons herein) corresponding to the amount of incident light. In the following, description are made on the case where the signal charges are electrons and each transistor is an n-type transistor. However, if the signal charges are holes, each transistor is a p-type transistor. 
     The transfer transistor TG 11 -Tr is connected between the photodiode PD 11  and the floating diffusion FD 11 , and the “on” state is controlled by the control signal TG 11 . Since the transfer transistor TG 11 -Tr is under the control of the reading control system, the control signal TG 11  makes the transfer transistor TG 11 -Tr in the “on” state during the predetermined high level (H) such that the photodiode PD 11  undergoes photoelectric conversion and the accumulated charges (electrons) are transferred to the floating diffusion FD 11 . 
     The transfer transistor TG 12 -Tr is connected between the photodiode PD 12  and the floating diffusion FD 11 , and the “on” state is controlled by the control signal TG 12 . Since the transfer transistor TG 12 -Tr is under the control of the reading control system, the control signal TG 12  makes the transfer transistor TG 12 -Tr in the “on” state during the predetermined high level (H) such that the photodiode PD 12  undergoes photoelectric conversion and the accumulated charges (electrons) are transferred to the floating diffusion FD 11 . 
     The transfer transistor TG 21 -Tr is connected between the photodiode PD 21  and the floating diffusion FD 11 , and the “on” state is controlled by the control signal TG 21 . Since the transfer transistor TG 21 -Tr is under the control of the reading control system, the control signal TG 21  makes the transfer transistor TG 21 -Tr in the “on” state during the predetermined high level (H) such that the photodiode PD 21  undergoes photoelectric conversion and the accumulated charges (electrons) are transferred to the floating diffusion FD 11 . 
     The transfer transistor TG 22 -Tr is connected between the photodiode PD 22  and the floating diffusion FD 11 , and the “on” state is controlled by the control signal TG 22 . Since the transfer transistor TG 22 -Tr is under the control of the reading control system, the control signal TG 22  makes the transfer transistor TG 22 -Tr in the “on” state during the predetermined high level (H) such that the photodiode PD 22  undergoes photoelectric conversion and the accumulated charges (electrons) are transferred to the floating diffusion FD 11 . 
     As shown in  FIG.  5   , the reset transistor RST 11 -Tr is connected between the power line VDD (or power supply potential) and the floating diffusion FD 11 , and the “on” state is controlled by the control signal RST 11 . Since the reset transistor RST 11 -Tr is under the control of the reading control system, the control signal RST 11  makes the reset transistor RST 11 -Tr in the “on” state during the high level H and the floating diffusion FD 11  is reset to the potential of the power line VDD (or VRst). 
     The source follower transistor SF 11 -Tr and the select transistor SEL 11 -Tr are connected in series between the power line VDD and the vertical signal line LSGN. The gate of the source follower transistor SF 11 -Tr is connected to the floating diffusion FD 11 , and the “on” state of the select transistor SEL 11 -Tr is controlled by the control signal SEL 11 . The control signal SEL 11  makes the select transistor SEL 11 -Tr in the “on” state during the high level H. Hence, the source follower transistor SF 11 -Tr converts the charges of the floating diffusion FD 11  into a voltage signal by means of the gain of the charge amount (potential) such that the column output read voltage (signal) VSL (PXLOUT) is outputted to the vertical signal line LSGN. 
     In such configuration, when the transfer transistor TG 11 -Tr of the pixel PX 11 , the transfer transistor TG 12 -Tr of the pixel PX 12 , the transfer transistor TG 21 -Tr of the pixel PX 21  and the transfer transistor TG 22 -Tr of the pixel PX 22  are individually turned on and off, the photodiodes PD 11 , PD 12 , PD 21  and PD 22  undergo photoelectric conversion, and the accumulated charges are sequentially transferred to the common floating diffusion FD 11 , the pixel signal VSL of the pixel unit is sent to the vertical signal line LSGN, and inputted to the column reading circuit  40 . In the embodiment, the camera mode is called a pixel independent mode. 
     On the other hand, when the transfer transistor TG 11 -Tr of the pixel PX 11 , the transfer transistor TG 12 -Tr of the pixel PX 12 , the transfer transistor TG 21 -Tr of the pixel PX 21  and the transfer transistor TG 22 -Tr of the pixel PX 22  are turned on and off at the same time (or the transfer transistors TG 12 -Tr, TG 21 -Tr and TG 22 -Tr are individually turned on and off), the photodiodes PD 11 , PD 12 , PD 21  and PD 22  undergo photoelectric conversion, and the accumulated charges are simultaneously transferred to the common floating diffusion FD 11  such that the floating diffusion FD 11  functions as an addition unit. At this time, a sum signal obtained by summing a plurality of pixel signals of 2, 3 or 4 pixels in the pixel unit is sent to the vertical signal line LSGN, and inputted to the column reading circuit  40 . In the embodiment, the imaging mode is called a pixel addition operation mode. 
     The vertical scanning circuit  30  drives the pixels in the shutter row and the reading row through row scanning control lines according to the control of the timing control circuit  60 . In addition, the vertical scanning circuit  30  outputs the row select signal for the row address of the read row for reading the signal and the shutter row for resetting the charges accumulated in the photodiode PD according to the address signal. 
     In a normal pixel reading operating, shutter scanning is performed by driving of the vertical scanning circuit  30  of the reading control system, and then reading scanning is performed. 
     The reading circuit  40  may also be configured to include a plurality of column signal processing circuits (not shown) corresponding to the column outputs of the pixel portions  20 , and perform column parallel processing by the plurality of column signal processing circuits. 
     The reading circuit  40  may include a correlated double sampling (CDS) circuit or an analog-digital converter (ADC), an amplifier (AMP) and a sample hole (S/H) circuit. 
     The horizontal scanning circuit  50  scans the signals processed by a plurality of column signal processing circuits such as the ADC of the reading circuit  40 , transmits the signals in a horizontal direction, and outputs the signals to the signal processing circuit  70 . 
     The timing control circuit  60  generates timing signals required for signal processing such as the pixel portion  20 , the vertical scanning circuit  30 , the reading circuit  40  and the horizontal scanning circuit  50 . 
     The signal processing circuit  70  may also have the function of generating a two-dimensional image through predetermined signal processing. The signal processing circuit  70  at least includes a correction circuit  710  and memory  720 , performs sensitivity difference correction processing such as correcting the sensitivity difference of each pixel, and outputs the processed pixel signal to the subsequent image signal processor (ISP). Additionally, the correction circuit  710  may be disposed inside a CMOS image sensor chip, and may also be disposed outside thereof. 
     The correction circuit  710  has a function of performing sensitivity difference correction procession for correcting the sensitivity difference of each pixel based on the weighting coefficient Wi stored in the memory  720 , for example. The correction circuit  710  executes (calculates) a required correction coefficient μ when performing sensitivity difference correction processing, and the correction coefficient stored in the memory  720  is processed. 
     The memory  720  stores the correction coefficient μ processed and obtained by the correction circuit  710 , and supplies it to the correction circuit  710  as necessary. 
     The following is for the correction processing of the correction circuit  710 . The correction coefficient acquisition processing that calculates and acquires the correction coefficient μ applied to the sensitivity difference correction processing is the core, and are described in relation to specific examples. 
     (Correction Coefficient Acquisition Processing of the Correction Circuit  710 ) In the first embodiment, the correction circuit  710  corrects sensitivities of the pixels of the pixel unit PU to be the correction target in a manner related to the correction coefficient μ obtained (calculated) by Equation 2. 
                     μ   =         ∑     i   =   1     n     ⁢     Wi   ×   Pi       n       ⁢     
     ⁢         ∑     i   =   1     n     ⁢   Wi     =   1             [     Equation   ⁢           ⁢   2     ]               
wherein μ is a correction coefficient,
         Wi is a weighting factor (a constant),   Pi is a sensitivity of each pixel, and   n is a total number of pixels related to correction.       

     The correction circuit  710  weighs a sensitivity Pn corresponding to a pixel signal of each pixel related to correction in the pixel unit PU to be the correction target and a sensitivity Pn corresponding to a pixel signal of each pixel related to correction in at least one pixel unit PU adjacent to the pixel unit PU to be the correction target by a weighting coefficient Wi. Consequently, the correction coefficient μ is obtained by a weighted average of the weighted sensitivities obtained by weighting. 
     In the first embodiment, the correction coefficient μ is calculated by dividing a sum of the weighted sensitivities by a total number of pixels related to correction. That is, the correction circuit  710  weighs a sensitivity Pn corresponding to a pixel signal of each pixel PX related to correction in the PU to be the correction target and a sensitivity corresponding to a pixel signal of each pixel related to correction in at least one same color pixel unit PU adjacent to the PU to be the correction target by a weighting coefficient Wi. Consequently, the correction coefficient μ is obtained (calculated) by dividing a sum of the weighted sensitivities by a total number of pixels related to correction. In addition, in the first embodiment, as described later, the correction circuit  710  divides a sum of the sensitivities Pn obtained by a weighted average by the number of pixels of the pixel units related to correction, not by the total number n of pixels related to correction to obtain a correction coefficient μ. 
       FIG.  6    is a diagram showing that a correction circuit obtains a correction coefficient of a corrected pixel unit and including an example of corrected related areas adjacent to the corrected pixel unit on the pixel array according to the first embodiment of the present disclosure. 
     Here, for example, the pixel unit PU 114  of the pixel group PXG 11  shown in  FIG.  3    is a correction target pixel unit CTPU. 1, 2, 3 or 4 pixel units are selected from the pixel unit PU 111  on the upper left side, the pixel unit PU 121  on the upper right side, the pixel unit PU 211  on the lower left side and the pixel unit PU 221  on the lower right side are relative to the pixel unit PU 114  to be the correction target, and used as adjacent pixel units AJPU 1  to AJPU 4 . In addition, the sensitivities of the read values of 4 pixels of the correction target pixel unit CTPU is represented by P1, P2, P3 and P4. The sensitivities of the 4-pixel adjacent pixel unit AJPU 1  is represented by P5, P6, P7 and P8. The sensitivities of the 4-pixel adjacent pixel unit AJPU 2  is represented by P9, P10, P11 and P12. The sensitivities of the 4-pixel adjacent pixel unit AJPU 3  is represented by P13, P14, P15 and P16. The sensitivities of the 4-pixel adjacent pixel unit AJPU 4  is represented by P17, P18, P19 and P20. Moreover, the 9 pixel units of 3×3 shown in  FIG.  6    are used to define a correction related area CRA. 
     Herein, three specific examples of the correction coefficient acquisition processing in the first embodiment are described as follows. 
     (First Specific Example of the Correction Coefficient Acquisition Processing in the First Embodiment) 
       FIG.  7    is a diagram showing a first specific example of obtaining a correction coefficient according to the first embodiment of the present disclosure. In addition, Equation 2-1 shows an example of substituting the first weighting coefficient CTW1 and the second weighting coefficient AJW1 into specific numerical values as the weighting coefficient of the above-mentioned Equation 2. 
     
       
         
           
             
               
                 
                   μ 
                   = 
                   
                     
                       
                         
                           ∑ 
                           
                             i 
                             = 
                             1 
                           
                           4 
                         
                         ⁢ 
                         
                           0.15 
                           × 
                           Pi 
                         
                       
                       + 
                       
                         
                           ∑ 
                           
                             i 
                             = 
                             5 
                           
                           20 
                         
                         ⁢ 
                         
                           0.025 
                           × 
                           Pi 
                         
                       
                     
                     20 
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                     ⁢ 
                     
                       - 
                     
                     ⁢ 
                     1 
                   
                   ] 
                 
               
             
           
         
       
     
     In the first specific example, the pixel unit PU 114  is equivalent to the correction target pixel unit CTPU, and uses the pixel unit PU 111  on the upper left side, the pixel unit PU 121  on the upper right side, the pixel unit PU 211  on the lower left side and the pixel unit PU 221  on the lower right side are relative to the pixel unit PU 114  to be the correction target as adjacent pixel units AJPU 1  to AJPU 4 . 
     The correction refers to the read value of each pixel PX (sensitivities P1 to P4 corresponding to the pixel signals) of the correction target pixel unit CTPU, which contains the correction target pixels, and also refers to the read value of each pixel of the adjacent pixel unit AJPU 1  (sensitivities P5 to P8 corresponding to the pixel signals), the read value of each pixel of the adjacent pixel unit AJPU 2  (sensitivities P9 to P12 corresponding to the pixel signals), the read value of each pixel of the adjacent pixel unit AJPU 3  (sensitivities P13 to P16 corresponding to the pixel signals) and the read value of each pixel of the adjacent pixel unit AJPU 4  (sensitivities P17 to P20 corresponding to the pixel signals). 
     Further, as shown in Equation 2-1, as for the weighting coefficient W, the first weighting coefficient CTW1 of the pixels of the correction target pixel unit CTPU (PU 114 ) is set to “0.15,” and the second weighting coefficient AJW1 of the pixels adjacent to the pixel units AJPU 1  to AJPU 4  is set to “0.025.” Such setting values satisfy the above-mentioned condition CTW&gt;AJW. Additionally, “0.15” of the first weighting coefficient CTW1 is set to correspond to the sensitivities P1 to P4 of the 4 pixels of the correction target pixel unit CTPU, and “0.025” of the second weighting coefficient AJW1 is set to correspond to the 16 pixels of the adjacent pixel units AJPU 1  to AJPU 4 . As a result, the sum of the weighting coefficients W becomes (0.15×4+0.025×16)=1, which satisfies the condition of Equation 2. Besides, in this example, the total number n of pixels that are the correction targets becomes “20.” 
     As such, in the first specific example, the correction circuit  710  obtains (calculates) the correction coefficient μ used to correct the sensitivity P1 of the correction target pixel at the upper left of the correction target pixel unit CTPU, and obtains the sensitivities P1 to P4 for the four G pixels arranged in the correction target pixel unit CTPU which is the same as the correction target pixel (G pixel) and multiplied by the first weighting coefficient CTW1 (0.15) such that the first sum of the sensitivities is obtained by weighting. At the same time, the correction circuit  710  obtains the sensitivities P5 to P20 for the sixteen G pixels of the adjacent pixel units AJPU 1  to AJPU 4  arranged diagonally above the correction target pixel unit CTPU and multiplied by the second weighting coefficient AJW1 (0.025) such that the second sum of the sensitivities is obtained by weighting. Moreover, the first sum of and the second sum of the weighted sensitivities are added to obtain a weighted total sensitivity, and the weighted total sensitivity is divided by the total number n(=20) of pixels related to correction to obtain a desired correction coefficient μt. 
     Accordingly, the pixel array  200  adjacent to the pixel unit containing a plurality of pixels with the same color like G pixels does not use a simple average, but uses not only the correction target pixel unit CTPU, but also the weighted average of the adjacent pixel units AJPUs adjacent to the correction target pixel unit CTPU. For example, it is possible to correct the uneven sensitivity generated by multiple factors under a microlens, thereby achieving the higher-precision image quality. 
     Besides, in the first embodiment, each weighting coefficient Wi is specified by a constant, and the sum thereof become a constant. In the example, the weighting coefficients are set such that the sum of the weighting coefficients Wi becomes 1. That is, the more adjacent pixel units related to correction are (i.e., the more the pixels related to correction are), the smaller the second weighting coefficient AJW1 is. The less adjacent pixel units related to corrections are (i.e., the less the pixels related to correction are), the larger the second weighting coefficient AJW2 is. 
     As a result, it is less affected by the number of adjacent pixel units (the number of pixels related to correction) related to correction, and it is possible to stably obtain a highly accurate correction coefficient μ with less unevenness regardless of the sampling area. 
     (Second Specific Example of the Correction Coefficient Acquisition Processing in the First Embodiment) 
       FIG.  8    is a diagram showing a second specific example of obtaining a correction coefficient according to the first embodiment of the present disclosure. In addition, Equation 2-2 shows an example of substituting the first weighting coefficient CTW1 and the second weighting coefficient AJW1 into specific numerical values as the weighting coefficient of the above-mentioned Equation 2. 
     
       
         
           
             
               
                 
                   μ 
                   = 
                   
                     
                       
                         
                           ∑ 
                           
                             i 
                             = 
                             1 
                           
                           4 
                         
                         ⁢ 
                         
                           0.15 
                           × 
                           Pi 
                         
                       
                       + 
                       
                         
                           ∑ 
                           
                             i 
                             = 
                             5 
                           
                           8 
                         
                         ⁢ 
                         
                           0.01 
                           × 
                           Pi 
                         
                       
                     
                     8 
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                     ⁢ 
                     
                       - 
                     
                     ⁢ 
                     2 
                   
                   ] 
                 
               
             
           
         
       
     
     In the second specific example, the pixel unit PU 114  is equivalent to the correction target pixel unit CTPU, and uses the pixel unit PU 111  on the upper left side with respect to the correction target pixel unit CTPU as an adjacent pixel unit AJPU 1  with the same color. In addition, in the example, 1, 2, 3 or 4 pixel units are selected from the pixel unit PU 111  on the upper left side, the pixel unit PU 121  on the upper right side, the pixel unit PU 211  on the lower left side and the pixel unit PU 221  on the lower right side are relative to the pixel unit PU 114  to be the correction target, and used as adjacent pixel units AJPU 1  to AJPU 4 . 
     The correction refers to the read value of each pixel PX (sensitivities P1 to P4 corresponding to the pixel signals) of the correction target pixel unit CTPU, which contains the correction target pixels, and also refers to the read value of each pixel of the adjacent pixel unit AJPU 1  (sensitivities P5 to P8 corresponding to the pixel signals). 
     Further, as shown in Equation 2-2, as for the weighting coefficient W, the first weighting coefficient CTW1 of the pixels of the correction target pixel unit CTPU (PU 114 ) is set to “0.15”, and the second weighting coefficient AJW1 of the pixels adjacent to the pixel unit AJPU 1  is set to “0.1.” Such setting value satisfies the above-mentioned condition CTW&gt;AJW. Additionally, “0.15” of the first weighting coefficient CTW1 is set to correspond to the sensitivities P1 to P4 of the 4 pixels of the correction target pixel unit CTPU, and “0.1” of the second weighting coefficient AJW1 is set to correspond to the 4 pixels of the adjacent pixel unit AJPU 1 . As a result, the sum of the weighting coefficients W becomes (0.15×4+0.1×4)=1, which satisfies the condition of Equation 2. Besides, in this example, the total number n of pixels that are the correction targets becomes “8.” 
     As such, in the second specific example, the correction circuit  710  obtains (calculates) the correction coefficient μ used to correct the sensitivity P1 of the correction target pixel at the upper left of the correction target pixel unit CTPU, and obtains the sensitivities P1 to P4 for the four G pixels arranged in the correction target pixel unit CTPU which is the same as the correction target pixel (G pixel) and multiplied by the first weighting coefficient CTW1 (0.15) such that the first sum of the sensitivities is obtained by weighting. At the same time, the correction circuit  710  obtains the sensitivities P5 to P8 for the four G pixels of the adjacent pixel unit AJPU 1  arranged diagonally above the correction target pixel unit CTPU and multiplied by the second weighting coefficient AJW1 (0.1) such that the second sum of the sensitivities is obtained by weighting. Moreover, the first sum of and the second sum of the weighted sensitivities are added to obtain a weighted total sensitivity, and the weighted total sensitivity is divided by the total number n(=8) of pixels related to correction to obtain a desired correction coefficient μ. 
     Accordingly, the pixel array  200  adjacent to the pixel unit containing a plurality of pixels with the same color like G pixels does not use a simple average, but uses not only the correction target pixel unit CTPU, but also the weighted average of the adjacent pixel units AJPUs adjacent to the correction target pixel unit CTPU. For example, it is possible to correct the uneven sensitivity generated by multiple factors under a microlens, thereby achieving the higher-precision image quality. 
     (Third Specific Example of the Correction Coefficient Acquisition Processing in the First Embodiment) 
       FIG.  9    is a diagram showing a third specific example of obtaining correction coefficients according to the first embodiment of the present disclosure. 
     In the third specific example, the correction circuit  710  may use different numbers of adjacent pixel units AJPU for correction according to the arrangement areas of pixels in the pixel portion  20 . In the example, the first arrangement area AR 1  and the second arrangement area AR 2  are adopted as arrangement areas of pixels. The first arrangement area AR 1  includes the central area ACTR of the pixel portion  20 , and the second arrangement area AR 2  includes the peripheral area AEDG of the pixel portion  20 . 
     The correction circuit  710  may use fewer adjacent pixel units AJPUs in the first arrangement area AR 1 , and then divide a sum of the weighted sensitivities according to Equation 2-2 by the first total number of pixels related to correction (8 in the example of  FIG.  9   ) to calculate the correction coefficient μ. The correction circuit  710  increases the number of adjacent pixel units AJPUs used in the second arrangement area AR 2  to improve accuracy, and then divide a sum of the weighted sensitivities according to Equation 2-1 by the first total number of pixels related to correction (20 in the example of  FIG.  9   ) to calculate the correction coefficient μ. 
     According to the correction method, it is easy to change the corrected sampling area or correction coefficient according to arrangement positions of the pixels in the pixel portion  20 . For example, in  FIG.  9   , in the central area ACTR of the pixel portion  20  of the image sensor, the correction coefficient μ for correcting the sensitivity is obtained by Equation 2-2. Besides, for example, Equation 2-1 can also be used in the chip peripheral area AEDG where the incidence of oblique light is more and the influence of shading is greater such that a wider range of adjacent pixels can be corrected. 
     To sum up, in the first embodiment, the correction circuit  710  weighs a sensitivity Pn corresponding to a pixel signal of each pixel PX related to correction in the PU to be the correction target and a sensitivity Pn corresponding to a pixel signal of each pixel related to correction in at least one same color PU adjacent to the PU to be the correction target by a weighting coefficient Wi. Accordingly, the correction coefficient μ is calculated by dividing a sum of the weighted sensitivities by a total number of pixels related to correction. 
     Therefore, the first embodiment has the advantages of being able to correct uneven sensitivity generated by multiple factors in a broad area and to achieve the higher-precision image quality. 
     In addition, according to the first embodiment, the correction circuit  710  can use different numbers of adjacent pixel units AJPUs for correction based on the arrangement areas of pixels in the pixel portion  20 . Hence, the first embodiment can individually correct uneven sensitivity generated by multiple factors in a broad area with the best correction method, and can achieve the higher-precision image quality, thereby being able to correct uneven sensitivity in a local area with high accuracy. 
     Second Embodiment 
       FIG.  10    is a diagram showing that a correction coefficient is obtained according to a second embodiment of the present disclosure. In addition, Equation 2-3 shows an example of substituting the first weighting coefficient CTW1 and the second weighting coefficient AJW1 into specific numerical values as the weighting coefficient of the above-mentioned Equation 2. 
     
       
         
           
             
               
                 
                   μ 
                   = 
                   
                     
                       
                         
                           
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   1 
                                 
                                 4 
                               
                               ⁢ 
                               
                                 0.011 
                                 × 
                                 Pi 
                               
                             
                             + 
                           
                         
                       
                       
                         
                           
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   5 
                                 
                                 9 
                               
                               ⁢ 
                               
                                 0.056 
                                 × 
                                 Pi 
                               
                             
                             + 
                             
                               
                                 ∑ 
                                 
                                   i 
                                   = 
                                   10 
                                 
                                 18 
                               
                               ⁢ 
                               
                                 0.0531 
                                 × 
                                 Pi 
                               
                             
                           
                         
                       
                     
                     18 
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                     ⁢ 
                     
                       - 
                     
                     ⁢ 
                     3 
                   
                   ] 
                 
               
             
           
         
       
     
     The differences between the second and the first embodiment are described as follows. In the first embodiment, each pixel unit PU is composed of 4 pixels (G) with the same color of 2×2, a microlens MCL is configured to correspond to all 4 pixels of each pixel unit PU. 
     In contrast, in the second embodiment, each pixel unit PU is composed of 9 pixels with the same color (G) of 3×3, and a microlens MCL is configured to correspond to the 4 pixels G1 to G4 at the upper left of the correction target pixel unit CTPU to have a PDAF function. Besides, each microlens MCL is configured to correspond to each pixel of the remaining pixels G5 to G9 of the correction target pixel unit CTPU, the pixels G10 to G45 of the adjacent pixel units AJPU 1  to AJPU 4  and the B pixels adjacent to the left and right of the CTPU and the R pixels adjacent to the top and bottom of the CTPU. 
     Moreover, in the second embodiment, the correction target pixel unit CTPU is divided into a first area AR 11  where the correction target pixels G1 to G4 are configured and a second area where the remaining pixels G5 to G9 are configured. The first weighting coefficient CTW1 is set for the first area AR 11 , and the second weighting coefficient AJW2 is set for the second area AR 12  to obtain a sum of the weighted sensitivities in each area. Subsequently, the correction coefficient μ is obtained by dividing a sum of the weighted sensitivities of the adjacent pixel unit AJPU  1  by the total number n of pixels related to correction. 
     Further, as shown in Equation 2-3, as for the weighting coefficient W, the first weighting coefficient CTW1 of the pixels of the first area AR 11  of the correction target pixel unit CTPU (PU 114 ) is set to “0.111,” the second weighting coefficient AJW2 of the pixels of the second area AR 12  is set to “0.056,” and the second weighting coefficient AJW1 of the pixels of the adjacent pixel unit AJPU 1  is set to “0.0531.” Such setting values satisfy the above-mentioned condition CTW&gt;AJW2&gt;AJW1. Additionally, “0.111” of the first weighting coefficient CTW1 is set to correspond to the sensitivities P1 to P4 of the 4 pixels G1 to G4 of the correction target pixel unit CTPU, “0.056” of the second weighting coefficient AJW2 is set to correspond to the 5 pixels G5 to G9 of the correction target pixel unit CTPU, and “0.0531” of the second weighting coefficient AJW1 is set to correspond to the 9 pixels G10 to G18 of the adjacent pixel unit AJPU 1 . As a result, the sum of the weighting coefficients W becomes (0.111×4+0.056×5+0.0531 x 9)=1, which satisfies the condition of Equation 2. Besides, in the example, the total number n of pixels that are the correction targets becomes “18.” 
     To sum up, in the second embodiment, in the pixel arrangement adjacent to 3×3 pixels with the same color, in order to correct the sensitivities of the pixels G1 to G4 with the same microlens in the correction target pixel unit CTPU located in the center, the pixels G5 to G9 located in the same pixel unit CTPU are multiplied by the coefficient μ of the adjacent pixel unit AJPU for weighting to correct the sensitivities. In other words, in the embodiment, the first weighting coefficient CTW1 of the target area configured with the pixels that are the correction targets is set to a maximum value, and the second weighting coefficient AJW used in other pixel arrangement areas is set to a value that meets the arrangement condition of the target area. 
     As such, by weighting and summing the influence of the distance or structure from the correction target pixel on sensitivity, it is possible to perform a more precise sensitivity correction than a simple sum of the average values. 
     Third Embodiment 
     Equation 3 (shown below) is a calculation for obtaining the correction coefficient in the correction coefficient acquisition processing of the third embodiment of the present disclosure. 
                   μ   =         ∑     i   =   1     n     ⁢     Wi   ×   Pi           ∑     i   =   1     n     ⁢   Wi               [     Equation   ⁢           ⁢   3     ]               
wherein μ is a correction coefficient,
         Wi is a weighting factor (a constant), and   Pi is a sensitivity of each pixel.       

     The differences between the correction coefficient of the third embodiment and the correction coefficient of the first embodiment are described as follows. 
     In the correction coefficient acquisition processing of the first embodiment, the correction circuit  710  weighs a sensitivity Pn corresponding to a pixel signal of each pixel related to correction in the pixel unit PU to be the correction target and a sensitivity Pn corresponding to a pixel signal of each pixel related to correction in at least one same color pixel unit PU adjacent to the pixel unit PU to be the correction target by a weighting coefficient Wi. Accordingly, the correction coefficient μ is calculated by dividing a sum of the weighted sensitivities by a total number n of pixels related to correction. 
     In contrast, in the correction coefficient acquisition processing of the third embodiment, the correction circuit  710  weighs a sensitivity Pn corresponding to a pixel signal of each pixel PX related to correction in the PU to be the correction target and a sensitivity Pn corresponding to a pixel signal of each pixel related to correction in at least one same color pixel unit PU adjacent to the PU to be the correction target by a weighting coefficient Wi. Consequently, the correction coefficient μ is calculated by dividing a sum of the weighted sensitivities by a sum of the weighting coefficients of the pixel units related to correction. 
     Here, three specific examples of the correction coefficient acquisition processing in the third embodiment are described as follows. 
     (First Specific Example of the Correction Coefficient Acquisition Processing in the Third Embodiment) 
       FIG.  11    is a diagram showing a first specific example of obtaining a correction coefficient according to the third embodiment of the present disclosure. In addition, Equation 3-1 shows an example of substituting the first weighting coefficient CTW1 and the second weighting coefficient AJW1 into specific numerical values as the weighting coefficient of the above-mentioned Equation 3. 
     
       
         
           
             
               
                 
                   μ 
                   = 
                   
                     
                       
                         
                           
                             ∑ 
                             
                               i 
                               = 
                               1 
                             
                             4 
                           
                           ⁢ 
                           
                             5 
                             × 
                             Pi 
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               i 
                               = 
                               5 
                             
                             20 
                           
                           ⁢ 
                           
                             3 
                             × 
                             Pi 
                           
                         
                       
                       
                         
                           
                             ∑ 
                             
                               i 
                               = 
                               1 
                             
                             4 
                           
                           ⁢ 
                           5 
                         
                         + 
                         
                           
                             ∑ 
                             
                               i 
                               = 
                               5 
                             
                             20 
                           
                           ⁢ 
                           3 
                         
                       
                     
                     = 
                     
                       
                         
                           5 
                           ⁢ 
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               4 
                             
                             ⁢ 
                             Pi 
                           
                         
                         + 
                         
                           3 
                           ⁢ 
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 5 
                               
                               20 
                             
                             ⁢ 
                             Pi 
                           
                         
                       
                       68 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     3 
                     ⁢ 
                     
                       - 
                     
                     ⁢ 
                     1 
                   
                   ] 
                 
               
             
           
         
       
     
     In the first specific example, the pixel unit PU 114  is equivalent to the correction target pixel unit CTPU, and uses the pixel unit PU 111  on the upper left side, the pixel unit PU 121  on the upper right side, the pixel unit PU 211  on the lower left side and the pixel unit PU 221  on the lower right side that are relative to the correction target pixel unit CTPU as adjacent pixel units AJPU 1  to AJPU 4 . 
     The correction refers to the read value of each pixel PX (sensitivities P1 to P4 corresponding to the pixel signals) of the correction target pixel unit CTPU, which contains the correction target pixels, and also refers to the read value of each pixel of the adjacent pixel units AJPU 1  to AJPU 4  (sensitivities P5 to P8, P9 to P12, P13 to P16 and P17 to P20 corresponding to the pixel signals). 
     Moreover, as shown in Equation 3-1, as for the weighting coefficient W, the first weighting coefficient CTW1 of the pixels of the correction target pixel unit CTPU (PU 114 ) is set to “5,” and the second weighting coefficient AJW1 of the pixels adjacent to the pixel units AJPU 1  to AJPU 4  is set to “3.” Such setting values satisfy the above-mentioned condition CTW&gt;AJW. Additionally, “5” of the first weighting coefficient CTW1 is set to correspond to the sensitivities P1 to P4 of the 4 pixels of the correction target pixel unit CTPU, and “3” of the second weighting coefficient AJW1 is set to correspond to the 16 pixels of the adjacent pixel units AJPU 1  to AJPU 4 . As a result, in the example, the sum of the weighting coefficients of the pixel units related to the correction target becomes “68.” 
     As such, in the first specific example, the correction circuit  710  obtains (calculates) the correction coefficient μ used to correct the sensitivity P1 of the correction target pixel at the upper left of the correction target pixel unit CTPU, and obtains the sensitivities P1 to P4 for the four G pixels arranged in the correction target pixel unit CTPU which is the same as the correction target pixel (G pixel) and multiplied by the first weighting coefficient CTW1 (5) such that the first sum of the sensitivities is obtained by weighting. At the same time, the correction circuit  710  obtains the sensitivities P5 to P20 for the sixteen G pixels of the adjacent pixel units AJPU 1  to AJPU 4  arranged diagonally above the correction target pixel unit CTPU and multiplied by the second weighting coefficient AJW1 (3) such that the second sum of the sensitivities is obtained by weighting. Moreover, the first sum of and the second sum of the weighted sensitivities are added to obtain a weighted total sensitivity, and the weighted total sensitivity is divided by the sum n(=68) of the weighting coefficients of the pixels related to correction to obtain a desired correction coefficient μ. 
     Accordingly, the pixel array  200  adjacent to the pixel unit containing a plurality of pixels with the same color like G pixels does not use a simple average, but uses not only the correction target pixel unit CTPU, but also the weighted average of the adjacent pixel units AJPUs adjacent to the correction target pixel unit CTPU. For example, it is possible to correct the uneven sensitivity generated by multiple factors under a microlens, thereby achieving the higher-precision image quality. 
     (Second Specific Example of the Correction Coefficient Acquisition Processing in the Third Embodiment) 
       FIG.  12    is a diagram showing a second specific example of obtaining a correction coefficient according to the third embodiment of the present disclosure. Additionally, Equation 3-2 shows an example of substituting the first weighting coefficient CTW1 and the second weighting coefficient AJW1 into specific numerical values as the weighting coefficient of the above-mentioned Equation 3. 
     
       
         
           
             
               
                 
                   μ 
                   = 
                   
                     
                       
                         
                           
                             ∑ 
                             
                               i 
                               = 
                               1 
                             
                             4 
                           
                           ⁢ 
                           
                             3 
                             × 
                             Pi 
                           
                         
                         + 
                         
                           
                             ∑ 
                             
                               i 
                               = 
                               5 
                             
                             8 
                           
                           ⁢ 
                           
                             2 
                             × 
                             Pi 
                           
                         
                       
                       
                         
                           
                             ∑ 
                             
                               i 
                               = 
                               1 
                             
                             4 
                           
                           ⁢ 
                           3 
                         
                         + 
                         
                           
                             ∑ 
                             
                               i 
                               = 
                               5 
                             
                             8 
                           
                           ⁢ 
                           2 
                         
                       
                     
                     = 
                     
                       
                         
                           3 
                           ⁢ 
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 1 
                               
                               4 
                             
                             ⁢ 
                             Pi 
                           
                         
                         + 
                         
                           2 
                           ⁢ 
                           
                             
                               ∑ 
                               
                                 i 
                                 = 
                                 5 
                               
                               8 
                             
                             ⁢ 
                             Pi 
                           
                         
                       
                       20 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     3 
                     ⁢ 
                     
                       - 
                     
                     ⁢ 
                     2 
                   
                   ] 
                 
               
             
           
         
       
     
     In the second specific example, the pixel unit PU 114  is equivalent to the correction target pixel unit CTPU, and uses the pixel unit PU 111  on the upper left side with respect to the correction target pixel unit CTPU as an adjacent pixel unit AJPU 1  with the same color. In addition, in the example, 1, 2 or 3 pixel units are selected from the pixel unit PU 111  on the upper left side, the pixel unit PU 121  on the upper right side, the pixel unit PU 211  on the lower left side and the pixel unit PU 221  on the lower right side are relative to the pixel unit PU 114  to be the correction target, and used as adjacent pixel units AJPU 1  to AJPU 4 . 
     The correction refers to the read value of each pixel PX (sensitivities P1 to P4 corresponding to the pixel signals) of the correction target pixel unit CTPU, which contains the correction target pixels, and also refers to the read value of each pixel of the adjacent pixel unit AJPU 1  (sensitivities P5 to P8 corresponding to the pixel signals). 
     Moreover, as shown in Equation 3-2, as for the weighting coefficient W, the first weighting coefficient CTW1 of the pixels of the correction target pixel unit CTPU (PU 114 ) is set to “3”, and the second weighting coefficient AJW1 of the pixels adjacent to the pixel unit AJPU 1  is set to “2.” Such setting value satisfies the above-mentioned condition CTW&gt;AJW. Additionally, “3” of the first weighting coefficient CTW1 is set to correspond to the sensitivities P1 to P4 of the 4 pixels of the correction target pixel unit CTPU, and “2” of the second weighting coefficient AJW1 is set to correspond to the 4 pixels of the adjacent pixel unit AJPU 1 . Besides, in this example, the sum n of the weighting coefficients of the pixels related to the correction target becomes “20.” 
     Hence, in the second specific example, the correction circuit  710  obtains (calculates) the correction coefficient μ used to correct the sensitivity P1 of the correction target pixel at the upper left of the correction target pixel unit CTPU, and obtains the sensitivities P1 to P4 for the four G pixels arranged in the correction target pixel unit CTPU which is the same as the correction target pixel (G pixel) and multiplied by the first weighting coefficient CTW1 (3) such that the first sum of the sensitivities is obtained by weighting. At the same time, the correction circuit  710  obtains the sensitivities P5 to P8 for the four G pixels of the adjacent pixel unit AJPU 1  arranged diagonally above the correction target pixel unit CTPU and multiplied by the second weighting coefficient AJW1 (2) such that the second sum of the sensitivities is obtained by weighting. Moreover, the first sum and the second sum of the weighted sensitivities are added to obtain a weighted total sensitivity, and the weighted total sensitivity is divided by the sum n(=20) of the weighting coefficients of the pixels related to correction to obtain a desired correction coefficient μ. 
     As such, the pixel array  200  adjacent to the pixel unit containing a plurality of pixels with the same color like G pixels does not use a simple average, but uses not only the correction target pixel unit CTPU, but also the weighted average of the adjacent pixel units AJPUs adjacent to the correction target pixel unit CTPU. For example, it is possible to correct the uneven sensitivity generated by multiple factors under a microlens, thereby achieving the higher-precision image quality. 
     (Third Specific Example of the Correction Coefficient Acquisition Processing in the Third Embodiment) 
       FIG.  13    is a diagram showing a third specific example of obtaining a correction coefficient according to the third embodiment of the present disclosure. 
     In the third specific example, the correction circuit  710  may use different numbers of adjacent pixel units AJPU for correction according to the arrangement areas of pixels in the pixel portion  20 . In the example, the first arrangement area AR 21  and the second arrangement area AR 22  are adopted as arrangement areas of pixels. The first arrangement area AR 21  includes the central area ACTR of the pixel portion  20 , and the second arrangement area AR 22  includes the peripheral area AEDG of the pixel portion  20 . 
     The correction circuit  710  may use fewer adjacent pixel units AJPUs in the first arrangement area AR 1 , and then divide a sum of the weighted sensitivities according to Equation 3-2 by the first total number of the weighting coefficients of the pixels related to correction (20 in the example of  FIG.  13   ) to calculate the correction coefficient μ. The correction circuit  710  increases the number of adjacent pixel units AJPUs used in the second arrangement area AR 2  to improve accuracy, and then divide a sum of the weighted sensitivities according to Equation 3-1 by the first total number of the weighting coefficients of the pixels related to correction (68 in the example of  FIG.  13   ) to calculate the correction coefficient μ. 
     According to the correction method, it is easy to change the corrected sampling area or correction coefficient according to arrangement positions of the pixels in the pixel portion  20 . For example, in  FIG.  13   , in the central area ACTR of the pixel portion  20  of the image sensor, the correction coefficient μ for correcting the sensitivity is obtained by Equation 3-2. Besides, for example, Equation 3-1 can also be used in the chip peripheral area AEDG where the incidence of oblique light is more and the influence of shading is greater such that a wider range of adjacent pixels can be corrected. 
     To sum up, in the first embodiment, the correction circuit  710  weighs a sensitivity Pn corresponding to a pixel signal of each pixel PX related to correction in the PU to be the correction target and a sensitivity Pn corresponding to a pixel signal of each pixel related to correction in at least one same color PU adjacent to the PU to be the correction target by a weighting coefficient Wi. Accordingly, the correction coefficient μ is calculated by dividing a sum of the weighted sensitivities by a total number n of the weighting coefficients of the pixels related to correction. 
     Therefore, the third embodiment has the advantages of being able to correct uneven sensitivity generated by multiple factors in a broad area and to achieve the higher-precision image quality. 
     In addition, according to the third embodiment, the correction circuit  710  can use different numbers of adjacent pixel units AJPUs for correction based on the arrangement areas of pixels in the pixel portion  20 . Thus, the third embodiment can individually correct uneven sensitivity generated by multiple factors in a broad area with the best correction method, and can achieve the higher-precision image quality, thereby being able to correct uneven sensitivity in a localized area with high accuracy. 
     Fourth Embodiment 
     Equation 4 (shown below) is a calculation for obtaining the correction coefficient in the fourth embodiment of the present disclosure. 
                   μ   =         ∑     i   =   1     n     ⁢       f     (   i   )       ×   Pi       n             [     Equation   ⁢           ⁢   4     ]               
wherein μ is a weighted average,
         f(i) is a weighting factor (a function),   Pi is a sensitivity of each pixel, and   n is a total number of pixels related to correction.       

     The differences between the correction coefficient of the fourth embodiment and the correction coefficients of the first, second and third embodiments are described as follows. 
     In the correction coefficient acquisition processing of the fourth embodiment, the aforementioned weighting coefficient Wi is generated by a function f(i). In the fourth embodiment, the function f(i) includes a function showing a theoretical value based on the microlens shading. 
     Here, a specific example of the correction coefficient acquisition processing in the fourth embodiment is described as follows. 
     (Specific Example of the Correction Coefficient Acquisition Processing in the Fourth Embodiment) 
     Specifically,  FIG.  14 A  shows a pixel unit arrangement of a pixel group,  FIG.  14 B  shows a brightness value distribution of a correction target pixel unit CTPU on a line x-x of  FIG.  14 A , and  FIG.  14 C  is a schematic diagram showing a situation of correcting shading in a way related to the function f(i). 
     In the fourth embodiment, each pixel unit PU is composed of 16 pixels with the same color (G) of 4×4. Besides, each microlens MCL  21  is configured to correspond to the correction target pixel unit CTPU and the four 16 pixels G1 to G16 of the adjacent pixel units AJPU 1  to AJPU  4  to have a PDAF function. 
     In the fourth embodiment, the function f(i) corrects the shading generated by the microlens MCL 21  of the pixels G1 to G16 relative to the correction target pixel unit CTPU. In addition, the function f(i) is used as a standby function. In the example, the sensitivities of the adjacent pixel units AJPU 1  to AJPU 4  are also used, and the distance from each of the correction target pixels is also added, that is, the coefficient corresponds to the degree of influence. Besides, in the example, the total number n of pixels that are the correction targets becomes “16.” 
     According to the fourth embodiment, it is also possible to more accurately correct the poor sensitivity generated by the unevenness of the shape of the microlens MCL  21  itself. As a result, the fourth embodiment can correct various uneven sensitivities by using the function as a standby function. 
     Fifth Embodiment 
     Equation 5 (shown below) is a calculation for obtaining the correction coefficient in the correction coefficient acquisition processing of the fifth embodiment of the present disclosure. 
                   μ   =         ∑     i   =   1     n     ⁢       f     (   i   )       ×     w     (   i   )       ×   Pi       n             [     Equation   ⁢           ⁢   5     ]               
wherein μ is a correction coefficient,
         w(i) is a weighting factor (a constant),   Pi is a sensitivity of each pixel,   n is a total number of pixels related to correction, and   f(i) is a weighting factor (a function).       

     The differences between the correction coefficient of the fifth embodiment and the correction coefficients of the fourth embodiment are described as follows. 
     In the correction coefficient acquisition processing of the fifth embodiment, when the weighted sensitivity is obtained by the weighting of the weighting coefficient, the correction coefficient μ is obtained by a weighted average after being associated with the function of the theoretical value of the state that meets the pixel arrangement conditions. That is, in the fifth embodiment, the so-called function of the theoretical value that meets the pixel arrangement conditions is equivalent to the function f(i) that shows the theoretical value of the shading based on the aforementioned microlens MCL 21 , and the function f(i) is multiplied by the correction coefficient determined by the distance from the correction target pixel such that the shading generated by the microlens MCL 21  is corrected. 
     Here, a specific example of the correction coefficient acquisition processing in the fifth embodiment is described as follows. 
     (Specific Example of the Correction Coefficient Acquisition Processing in the Fifth Embodiment) 
       FIG.  15 A  to  FIG.  15 C  are diagrams showing the correction coefficient acquisition processing according to the fifth embodiment of the present disclosure. Specifically,  FIG.  15 A  shows a pixel unit arrangement of a pixel group,  FIG.  15 B  shows a brightness value distribution of a correction target pixel unit CTPU on a line x-x of  FIG.  15 A , and  FIG.  15 C  is a schematic diagram showing a situation of correcting shading in a way related to the function f(i). 
     In the fifth embodiment, similar to the fourth embodiment, each pixel unit PU is composed of 16 pixels with the same color (G) of 4×4. Besides, each microlens MCL  21  is configured to correspond to the correction target pixel unit CTPU and the four 16 pixels G1 to G16 of the adjacent pixel units AJPU 1  to AJPU  4  to have a PDAF function. 
     In the fifth embodiment, a microlens MCL  21  is configured to correspond to the correction target pixel unit CTPU, and four microlens MCL 21  are also configured to correspond the four 16 pixels G1 to G16 of the adjacent pixel units AJPU 1  to AJPU  4 , respectively. If the uneven sensitivity of each pixel is required to be corrected, the fifth embodiment not only obtains an average of the sensitivities of 16 pixels in the same 4×4 pixel units, but also corrects the shading generated by the microlens to obtain a weighted average, thereby more accurately correcting the uneven sensitivity of each pixel. In the example, the sensitivities of the adjacent pixel units AJPU  1  to AJPU 4  are also used, and the distance from each of the correction target pixels is also added, that is, the coefficient corresponds to the degree of influence. Besides, in the example, the total number n of pixels that are the correction targets becomes “80.” 
     According to the fifth embodiment, it is also possible to more accurately correct the poor sensitivity generated by the unevenness of the shape of the microlens MCL  21  itself. As a result, the fifth embodiment can correct various uneven sensitivities by using the function as a standby function. 
     Sixth Embodiment 
       FIG.  16 A  and  FIG.  16 B  are diagrams showing the correction coefficient acquisition processing according to the sixth embodiment of the present disclosure. 
     The differences between the sixth embodiment and the first embodiment are described as follows. 
     In the first embodiment, each pixel unit PU is composed of 4 pixels (G) with the same color of 2×2, a microlens MCL is configured to correspond to all 4 pixels of each pixel unit PU. 
     In contrast, in the sixth embodiment, as shown in  FIG.  16 A , each pixel unit PU is composed of 9 pixels with the same color (G) of 3×3, and a microlens MCL 31  is configured to correspond to the 2 pixels G4 and G5 of the correction target pixel unit CTPU to have a PDAF function. Alternatively, as shown in  FIG.  16 B , each pixel unit PU is composed of 9 pixels with the same color (G) of 3×3, and a metal shield MSL 31  is configured to correspond to the 2 pixels G4 and G5 of the correction target pixel unit CTPU to have a PDAF function. Since the sixth embodiment can include locality in the sensitivities of pixels with the PDAF function in a pixel unit, the sensitivities of the correction target pixel unit CTPU can be corrected based on a function of a weighted average of the pixels of the correction target pixel unit CTPU or the pixels of the adjacent pixel units AJPU with the same color or weighted sensitivities of surrounding pixels of the correction target pixel unit CTPU. 
     Seventh Embodiment 
       FIG.  17    is a diagram showing the correction coefficient acquisition processing according to the seventh embodiment of the present disclosure. 
     The differences between the seventh embodiment and the first embodiment are described as follows. In the first embodiment, each pixel unit PU is composed of 4 pixels (G) with the same color of 2×2, a microlens MCL is configured to correspond to all 4 pixels of each pixel unit PU. 
     In contrast, in the seventh embodiment, as shown in  FIG.  17   , each pixel unit PU is composed of 9 pixels with the same color (G) of 3×3, and a black and white pixel or a near infrared (NIR) pixel is configured to correspond to each of the 2 pixels G4 and G5 of the correction target pixel unit CTPU. Consequently, the pixel unit of the correction target pixel unit CTPU contains different colors. 
     Since the seventh embodiment can include locality in the sensitivities of black and white pixels or NIR pixels in a pixel unit, the sensitivities of the correction target pixel unit CTPU can be corrected based on a function of a weighted average of the pixels of the correction target pixel unit CTPU or the pixels of the adjacent pixel units AJPU with the same color or weighted sensitivities of surrounding pixels of the correction target pixel unit CTPU. 
     Eighth Embodiment 
     Equation 6 (shown below) is a calculation for obtaining the correction coefficient in the correction coefficient acquisition processing of the eighth embodiment of the present disclosure. 
                     μ     i   /   2       =             x     i   /   2                     x       i   /   2     -   1       +     x     i   /   2         2           ⁢           n   -     odd   ⁢           ⁢   number                 n   -     even   ⁢           ⁢   number                       [     Equation   ⁢           ⁢   6     ]               
wherein μ i/2  is a middle value, and
         x is a sensitivity of each pixel.       

       FIG.  18    is a diagram showing that a correction coefficient is obtained according to an eighth embodiment of the present disclosure. 
     The differences between the eighth embodiment and the first, second, third, fourth, fifth, sixth and seventh embodiments are described as follows. In the eighth embodiment, the correction coefficient acquisition processing is to obtain a middle value of the same pixel unit or other adjacent pixel units as a correction coefficient for the sensitivities of the pixels, instead of the weighted average. 
     The eight embodiment can correct the uneven sensitivities in a broad area that is difficult to correct in the prior art by using a middle value of adjacent pixels with the same color. 
     Ninth Embodiment 
     Equation 7 (shown below) is a calculation for obtaining the correction coefficient in the correction coefficient acquisition processing of the ninth embodiment of the present disclosure. 
                     M   o     =     l   +         f     +   1           f     -   1       +     f     +   1           ×   h               [     Equation   ⁢           ⁢   7     ]               
wherein Mo is a mode value,
         l is a lower point of a class containing the mode value Mo,   f +1  is the number of degrees between the following classes,   f −1  is the number of degrees between the preceding classes, and   h is a width between classes.       

     In Equation 7, Mo represent a mode value, l represents a lower point of a class containing the mode value Mo, f +1  represents the number of degrees between the following classes, f −1  represents the number of degrees between the preceding classes, and h represents a width between classes. 
       FIG.  19    a diagram showing that a correction coefficient is obtained according to a ninth embodiment of the present disclosure. 
     The differences between the ninth embodiment and the first, second, third, fourth, fifth, sixth and seventh embodiments are described as follows. In the ninth embodiment, the correction coefficient acquisition processing is to obtain a mode value of the same pixel unit or other adjacent pixel units as a correction coefficient for the sensitivities of the pixels, instead of the weighted average. 
     The ninth embodiment can correct the uneven sensitivities in a broad area that is difficult to correct in the prior art by using a middle value of adjacent pixels with the same color. 
     The solid-state imaging apparatus  10  described above can be used as a camera apparatus that is applied to electronic devices such as digital cameras, camcorders, mobile terminal apparatus, surveillance cameras and medical endoscope cameras. 
       FIG.  20    is a diagram showing a structure example of an electronic device to which the solid-state imaging apparatus is applied according to the present disclosure. 
     As shown in  FIG.  20   , the electronic device  800  has a CMOS image sensor  810  to which the solid-state imaging apparatus  10  of the present disclosure can be applied. In addition, the electronic device  800  has an optical system (a lens, etc.)  820  that guides incident light to the pixel area of the CMOS image sensor  810  (imaging of an image). The electronic device  800  has a signal processing circuit (PRC)  830  for processing the output signal of the CMOS image sensor  810 . 
     The signal processing circuit  830  performs predetermined signal processing on the output signal of the CMOS image sensor  810 . The image signals processed by the signal processing circuit  830  are displayed as animations on a monitor composed of a liquid crystal display, etc. Additionally, the image signals can also be directly recorded in various recording media such as a memory card. 
     In summary, the present disclosure can provide a high-performance, small-sized and low-cost camera system by mounting the aforementioned solid-state imaging apparatus  10  as the CMOS image sensor  810 . Besides, the present disclosure can realize electronic device such as surveillance cameras, medical endoscope cameras, etc., which are used in applications where the installation requirements of the camera have restrictions on the installation size, the number of cables that can be connected, the cable length and the installation height.