Patent Publication Number: US-10762859-B2

Title: Display device and display method

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority under 35 U.S.C. § 119 from Japanese Patent Application No. 2017-097955, filed on May 17, 2017, and Japanese Patent Application No. 2017-097954, filed on May 17, 2017, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     The present disclosure relates to a display device and display method which can prevent an occurrence of disclination when displaying an image. 
     Examples of a display device may include a liquid crystal device having a display pixel unit in which a plurality of pixels are arranged in horizontal and vertical directions. The liquid display device can perform gradation display of an image by driving liquid crystal based on gradation data of each pixel. An example of the liquid crystal display device is described in Japanese Unexamined Patent Application Publication No. 2014-2232. 
     SUMMARY 
     Recently, liquid crystal display devices have been improved in resolution so as to be referred to as 4K liquid crystal display devices in which the number of pixels in the horizontal direction is 4,096 or 3,840, and the number of pixels in the vertical direction is 2,400 or 2,160. The improvement in resolution tends to reduce a pixel pitch. The reduction of the pixel pitch may easily cause disclination. 
     The disclination is caused by a potential difference between adjacent pixels, and thus orients liquid crystal molecules in a direction different from a desired direction. The disclination serves as a factor that degrades the quality of a display image. In a liquid crystal display device using a vertical alignment liquid crystal, the vertical alignment property is degraded when a pretilt angle is increased. Thus, a black level may be raised to lower the contrast of the displayed image. Therefore, by decreasing the pretilt angle, it is possible to increase the contrast. However, when the pretilt angle is excessively decreased, disclination may easily occur. 
     A first aspect of one or more embodiments provides a display device including: a display pixel unit in which a plurality of pixels are arranged in a horizontal direction and a vertical direction; and a signal processing unit configured to determine a correction value corresponding to a target pixel based on differences between gradation data of the target pixel and gradation data of peripheral pixels disposed in the horizontal direction, the vertical direction, and an oblique direction with respect to the target pixel, respectively, among the plurality of pixels, increase or decrease a pixel value of the target pixel based on the correction value, and thus correct the gradation data of the target pixel to reduce the differences. 
     A second aspect of one or more embodiments provides a display method including: determining a correction value corresponding to a target pixel, based on differences between gradation data of the target pixel and gradation data of peripheral pixels disposed in a horizontal direction, a vertical direction, and an oblique direction with respect to the target pixel, respectively, among a plurality of pixels arranged in the horizontal direction and the vertical direction; and increasing or decreasing a pixel value of the target pixel based on the correction value, and thus correcting the gradation data of the target pixel to reduce the differences. 
     A third aspect of one or more embodiments provides a display device including: a display pixel unit having a plurality of pixels arranged therein; and a signal processing unit configured to determine a correction value corresponding to a target pixel based on a difference between gradation data of the target pixel and gradation data of a first peripheral pixel adjacent to the target pixel and a second peripheral pixel adjacent to the first peripheral pixel among the plurality of pixels, increase or decrease a pixel value of the target pixel based on the correction value, and thus correct the gradation data of the target pixel to reduce the difference. 
     A fourth aspect of one or more embodiments provides a display method including: determining a correction value corresponding to a target pixel, based on a difference between gradation data of the target pixel and gradation data of a first peripheral pixel adjacent to the target pixel and a second peripheral pixel adjacent to the first peripheral pixel among a plurality of pixels; and increasing or decreasing a pixel value of the target pixel based on the correction value, and thus correcting the gradation data of the target pixel to reduce the difference. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a configuration diagram illustrating display devices according to first to fourth embodiments. 
         FIG. 2  schematically illustrates a part of a display pixel unit. 
         FIG. 3  illustrates an example of gradation data of pixels in video data. 
         FIG. 4  illustrates an example in which the gradation data of the pixels are corrected. 
         FIG. 5  illustrates an example in which the gradation data of the pixels are corrected. 
         FIG. 6  illustrates an example in which the gradation data of the pixels are corrected. 
         FIG. 7  illustrates an example of gradation data of pixels in video data. 
         FIG. 8  illustrates an example in which the gradation data of the pixels are corrected. 
         FIG. 9  illustrates the relation between correction coefficients and differences in gradation data between peripheral pixels and a target pixel. 
         FIG. 10  illustrates an example in which the gradation data of the pixels are corrected. 
         FIG. 11  illustrates the relation between correction coefficients and differences in gradation data between peripheral pixels and a target pixel. 
         FIG. 12  illustrates an example in which the gradation data of the pixels are corrected. 
         FIG. 13  illustrates the relation between correction coefficients and differences in gradation data between peripheral pixels and a target pixel. 
         FIG. 14  illustrates an example in which the gradation data of the pixels are corrected. 
         FIG. 15  illustrates an example in which the gradation data of the pixels are corrected. 
         FIG. 16  illustrates an example in which the gradation data of the pixels are corrected. 
         FIGS. 17A to 17D  schematically illustrate examples of images which are successively displayed for each frame when gradation correction is not performed. 
         FIGS. 18A to 18D  schematically illustrate examples of images which are successively displayed for each frame when gradation correction is performed based on peripheral pixels disposed in the horizontal direction and the vertical direction with respect to a target pixel. 
         FIGS. 19A to 19D  schematically illustrate examples of images which are successively displayed for each frame when gradation correction is performed based on peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel. 
         FIGS. 20A to 20D  schematically illustrate examples of images which are successively displayed for each frame when gradation correction is not performed. 
         FIGS. 21A to 21D  schematically illustrate examples of images which are successively displayed for each frame when gradation correction is performed based on peripheral pixels disposed in the horizontal direction and the vertical direction with respect to the target pixel. 
         FIGS. 22A to 22D  schematically illustrate examples of images which are successively displayed for each frame when gradation correction is performed based on peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel. 
     
    
    
     DETAILED DESCRIPTION 
     First Embodiment 
     Referring to  FIG. 1 , a display device according to a first embodiment will be described. The display device  11  includes a signal processing unit  21 , a display pixel unit  30 , a horizontal scanning circuit  40 , and a vertical scanning circuit  50 . 
     The signal processing unit  21  may be composed of either hardware (a circuit) or software (a computer program), or may be composed of a combination of hardware and software. 
     The display pixel unit  30  has a plurality (xxy) of pixels  60  arranged in a matrix shape at the respective intersections between a plurality (x) of column data lines D 1  to Dx arranged in the horizontal direction, and a plurality (y) of row scanning lines G 1  to Gy arranged in the vertical direction. That is, the plurality of pixels  60  are arranged in the horizontal direction and the vertical direction in the display pixel unit  30 . The pixels  60  are connected to the respective column data lines D 1  to Dx, and connected to the respective row scanning lines G 1  to Gy. 
     The signal processing unit  21  receives video data VD as a digital signal. The signal processing unit  21  generates gradation corrected video data SVD by performing gradation correction on a pixel basis, based on the video data VD, and outputs the gradation corrected video data SVD to the horizontal scanning circuit  40 . A specific gradation correction method for the video data VD through the signal processing unit  21  will be described later. 
     The horizontal scanning circuit  40  is connected to the pixels  60  of the display pixel unit  30  through the column data lines D. For example, the column data line D 1  is connected to y pixels  60  at the first column of the display pixel unit  30 . The column data line D 2  is connected to y pixels  60  at the second column of the display pixel unit  30 , and the column data line Dx is connected to y pixels  60  of the x-th column of the display pixel unit  30 . 
     The horizontal scanning circuit  40  sequentially receives the gradation corrected video data SVD as gradation signals DL corresponding to x pixels  60  of one row scanning line G for one horizontal scanning period. The gradation signal DL has n-bit gradation data. For example, when n is set to 8, the display pixel unit  30  can display an image at 256 gradations for each of the pixels  60 . 
     The horizontal scanning circuit  40  sequentially shifts the n-bit gradation data in parallel, and outputs the shifted data to the column data lines D 1  to Dx. When the display pixel unit  30  is a 4K-resolution (x=4,096) liquid crystal panel, for example, the horizontal scanning circuit  40  sequentially shifts n-bit gradation data corresponding to 4,096 pixels  60 , respectively, and outputs the shifted data to the column data lines D 1  to Dx, for one horizontal scanning period. 
     The vertical scanning circuit  50  is connected to the pixels  60  of the display pixel unit  30  through the row scanning lines G. For example, the row scanning line G 1  is connected to x pixels  60  at the first row of the display pixel unit  30 , and the row scanning line G 2  is connected to x pixels at the second row of the display pixel unit  30 . The row scanning line Gy is connected to x pixels  60  at the y-th row of the display pixel unit  30 . 
     The vertical scanning circuit  50  sequentially selects the row scanning lines G from the row scanning line G 1  to the row scanning line Gy one by one, on one horizontal scanning period basis. When the column data lines D are selected by the horizontal scanning circuit  40  and the row scanning lines G are selected by the vertical scanning circuit  50 , gradation data corresponding to the pixels  60  selected in the display pixel unit  30  are applied as gradation driving voltages. Accordingly, the pixels  60  display gradations according to the voltage values of the applied gradation driving voltages. The display pixel unit  30  can perform gradation display of an image as all of the pixels  60  display gradations. 
     Referring to  FIGS. 2 to 8 , the gradation correction method for video data VD through the signal processing unit  21  will be described.  FIG. 2  schematically illustrates a part of the display pixel unit  30  of  FIG. 1 . Specifically,  FIG. 2  illustrates the pixels  60  of the (n−2)-th to (n+2)-th rows (n≥3) and the (m−2)-th to (m+2)-th columns (m≥3) in the display pixel unit  30  of  FIG. 1 . 
     In order to distinguish the respective pixels  60  from each other, the pixels  60  of the (m−2)-th to (m+2)-th columns at the (n−2)-th row are set to pixels  60   n −2_m−2,  60   n −2_m−1,  60   n− 2_m,  60   n− 2_m+1, and  60   n −2_m+2. The pixels  60  of the (m−2)-th to (m+2)-th columns at the (n−1)-th row are set to pixels  60   n− 1_m−2,  60   n− 1_m−1,  60   n− 1_m,  60   n− 1_m+1, and  60   n− 1_m+2. 
     The pixels  60  of the (m−2)-th to (m+2)-th columns at the n-th row are set to pixels  60   n _ m− 2,  60   n _ m− 1,  60   n _ m ,  60   n _ m+ 1, and  60   n _ m+ 2. The pixels  60  of the (m−2)-th to (m+2)-th columns at the (n+1)-th row are set to pixels  60   n +1_m−2,  60   n+ 1_m−1,  60   n+ 1_m,  60   n +1_m+1, and  60   n +1_m+2. The pixels  60  of the (m−2)-th to (m+2)-th columns at the (n+2)-th row are set to pixels  60   n+ 2_m−2,  60   n +2_m−1,  60   n +2_m,  60   n +2_m+1, and  60   n +2_m+2. 
     In the video data VD, the gradation data corresponding to the pixels  60   n− 2_m−2,  60   n− 2_m−1,  60   n− 2_m,  60   n− 2_m+1, and  60   n −2_m+2 are set to gradation data gr_n−2_m−2, gr_n−2_m−1, gr_n−2_m, gr_n−2_m+1, and gr_n−2 m+2. The gradation data corresponding to the pixels  60   n− 1_m−2,  60   n− 1_m−1,  60   n− 1_m,  60   n− 1_m+1, and  60   n −1_m+2 are set to gradation data gr_n−1_m−2, gr_n−1_m−1, gr_n−1_m, gr_n−1_m+1, and gr_n−1_m+2. 
     The gradation data corresponding to the pixels  60   n _ m− 2,  60   n _ m− 1,  60   n _ m ,  60   n _ m+ 1, and  60   n _ m+ 2 are set to gradation data gr_n_m−2, gr_n_m−1, gr_n_m, gr_n_m+1, and gr_n_m+2. The gradation data corresponding to the pixels  60   n +1_m−2,  60   n+ 1_m−1,  60   n +1_m,  60   n +1_m+1, and  60   n +1_m+2 are set to gradation data gr_n+1_m−2, gr_n+1_m−1, gr_n+1_m, gr_n+1_m+1, and gr_n+1_m+2. 
     The gradation data corresponding to the pixels  60   n+ 2_m−2,  60   n +2_m−1,  60   n +2_m,  60   n +2_m+1, and  60   n +2_m+2 are set to gradation data gr_n+2_m−2, gr_n+2_m−1, gr_n+2_m, gr_n+2_m+1, and gr_n+2_m+2. 
     The signal processing unit  21  performs a gradation correction process on the gradation data inputted to the respective pixels  60 . Specifically, the signal processing unit  21  calculates a difference between the gradation data of a target pixel and the gradation data of two peripheral pixels disposed in each of a horizontal direction, a vertical direction, and an oblique direction with respect to the target pixel, based on Equation (1). Then, the signal processing unit  21  specifies the maximum value from the calculation results, and sets the maximum value to a correction value CV for the target pixel. 
     
       
         
           
             
               
                 
                   
                     
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     Here, α (α11 to α18) represents a correction coefficient (first correction coefficient) for a peripheral pixel  60  (first peripheral pixel) close to the target pixel between two pixels, and β (β11 to β18) represents a correction coefficient (second correction coefficient) for a peripheral pixel  60  (second peripheral pixel) far from the target pixel. The correction coefficients α and β are integers equal to or more than 0, respectively. The correction coefficients α and β are expressed through a relational expression of α=k×β (k≥1). That is, a weight equal to or more than that of the peripheral pixel  60  far from the target pixel is applied to the peripheral pixel  60  close to the target pixel. 
     The signal processing unit  21  determines the correction value CV corresponding to the target pixel, based on a difference between the gradation data of the target pixel and the gradation data of the first peripheral pixel adjacent to the target pixel and the second peripheral pixel adjacent to the first peripheral pixel among the plurality of pixels  60 . The signal processing unit  21  increases the pixel value of the target pixel by adding the correction value CV to the gradation data of the target pixel, thereby decreasing the differences. The pixel value is a gradation value, for example. 
     The signal processing unit  21  calculates a difference between a plurality of peripheral pixels respectively disposed in the horizontal direction, the vertical direction, and the oblique direction of the target pixel, specifies the maximum value from the calculation results, and sets the maximum value to the correction value CV. 
     The signal processing unit  21  calculates the differences based on the correction coefficients α11 to α18 and β11 to β18 depending on the directions in which the peripheral pixels are disposed with respect to the target pixel or the distances between the target pixel and the peripheral pixels, specifies the maximum value from the calculation results, and sets the maximum value to the correction value CV for the target pixel. Furthermore, a relation of α11=α12=α13=α14=α15=α16=α=17=α18 and a relation of β11=β12=β13=β14=β15=β16=β17=β18 may be applied. 
     For example, when the pixel  60   n _ m  of the m-th column at the n-th row is set to the target pixel, the signal processing unit  21  calculates a difference between the gradation data of the target pixel and the gradation data of two peripheral pixels disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the pixel  60   n _ m  set to the target pixel, based on Equation (1). Then, the signal processing unit  21  specifies the maximum value MAX from the calculation results, and sets the maximum value MAX to a correction value CV_n_m for the pixel  60   n _ m . In the following descriptions, the horizontal direction may be set to the right direction or the left direction, the vertical direction may be set to the top direction or the bottom direction, and the oblique direction may be set to the top right direction, the bottom right direction, the bottom left direction, or the top left direction, in association with  FIG. 2 . 
     Specifically, the signal processing unit  21  calculates a difference between the gradation data of the pixel  60   n _ m  and the gradation data of the peripheral pixels  60   n− 1_m and  60   n− 2_m disposed in the top direction with respect to the pixel  60   n _ m  set to the target pixel, based on an operation expression of α11×(gr_n−1_m−gr_n_m)+β11×(gr_n−2_m−gr_n_m) in Equation (1). The signal processing unit  21  calculates a difference between the gradation data of the pixel  60   n _ m  and the gradation data of the peripheral pixels  60   n _ m+ 1 and  60   n _ m+ 2 disposed in the right direction with respect to the pixel  60   n _ m , based on an operation expression of α12×(gr_n_m+1−gr_n_m)+β12×(gr_n_m+2−gr_n_m) in Equation (1). 
     The signal processing unit  21  calculates a difference between the gradation data of the pixel  60   n _ m  and the gradation data of the peripheral pixels  60   n +1_m and  60   n+ 2_m disposed in the bottom direction with respect to the pixel  60   n _ m , based on an operation expression of α13×(gr_n+1_m−gr_n_m)+β13×(gr_n+2_m−gr_n_m)} in Equation (1). The signal processing unit  21  calculates a difference between the gradation data of the pixel  60   n _ m  and the gradation data of the peripheral pixels  60   n _ m− 1 and  60   n _ m− 2 disposed in the left direction with respect to the pixel  60   n _ m , based on an operation expression of α14×(gr_n_m−1−gr_n_m)+β14×(gr_n_m−2−gr_n_m) in Equation (1). The signal processing unit  21  calculates a difference between the gradation data of the pixel  60   n _ m  and the gradation data of the peripheral pixels  60   n− 1_m+1 and  60   n −2_m+2 disposed in the top right direction with respect to the pixel  60   n _ m , based on an operation expression of α15×(gr_n−1_m+1−gr_n_m)+β15×(gr_n−2_m+2−gr_n_m) in Equation (1). The signal processing unit  21  calculates a difference between the gradation data of the pixel  60   n _ m  and the gradation data of peripheral pixels  60   n +1_m+1 and  60   n +2_m+2 disposed in the bottom right direction with respect to the pixel  60   n _ m , based on an operation expression of α16×(gr_n+1_m+1−gr_n_m)+β16×(gr_n+2_m+2−gr_n_m) in Equation (1). 
     The signal processing unit  21  calculates a difference between the gradation data of the pixel  60   n _ m  and the gradation data of the peripheral pixels  60   n +1_m−1 and  60   n+ 2_m−2 disposed in the bottom left direction with respect to the pixel  60   n _ m , based on an operation expression of α17×(gr_n+1_m−1−gr_n_m)+β17×(gr_n+2_m−2−gr_n_m) in Equation (1). The signal processing unit  21  calculates a difference between the gradation data of the pixel  60   n _ m  and the gradation data of the peripheral pixels  60   n− 1_m−1 and  60   n− 2_m−2 disposed in the top left direction with respect to the pixel  60   n _ m , based on an operation expression of α18×(gr_n−1_m−1−gr_n_m)+β18×(gr_n−2_m−2−gr_n_m)} in Equation (1). 
     The signal processing unit  21  specifies the maximum value MAX from the calculation results, and sets the maximum value MAX to the correction value CV_n_m for the pixel  60   n _ m . The signal processing unit  21  corrects the gradation data of the pixel  60   n _ m  into gradation data obtained by adding the correction value CV_n_m to the gradation data gr_n_m of the pixel  60   n _ m  in the video data VD. That is, the signal processing unit  21  determines the correction value CV corresponding to the target pixel, based on the difference between the gradation data of the target pixel and the gradation data of two peripheral pixels disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel among the plurality of pixels  60 . The signal processing unit  21  increases the pixel value of the target pixel by adding the correction value CV to the gradation data of the target pixel, thereby decreasing the difference. 
     The signal processing unit  21  determines the correction value CV corresponding to the target pixel, based on the differences between the gradation data of the target pixel and the gradation data of the two peripheral pixels disposed in the right direction with respect to the target pixel, the gradation data of the two peripheral pixels disposed in the left direction with respect to the target pixel, the gradation data of the two peripheral pixels disposed in the top direction with respect to the target pixel, the gradation data of the two peripheral pixels disposed in the bottom direction with respect to the target pixel, the gradation data of the two peripheral pixels disposed in the top right direction with respect to the target pixel, the gradation data of the two peripheral pixels disposed in the bottom right direction with respect to the target pixel, the gradation data of the two peripheral pixels disposed in the bottom left direction with respect to the target pixel, and the gradation data of the two peripheral pixels disposed in the top left direction with respect to the target pixel. The signal processing unit  21  increases the pixel value of the target pixel by adding the correction value CV to the gradation data of the target pixel, thereby decreasing the differences. 
     The signal processing unit  21  performs the same gradation correction process as the pixel  60   n _ m  on the whole pixels  60  of the display pixel unit  30 . The signal processing unit  21  generates the gradation corrected video data SVD by performing the gradation correction process on the whole pixels  60  in the video data VD, and outputs the gradation corrected video data SVD to the horizontal scanning circuit  40 . 
       FIG. 3  illustrates the case in which the gradation data gr of the pixels  60  of the (m−2)-th to m-th columns in the video data VD are 0, and the gradation data gr of the pixels  60  of the (m+1)-th and (m+2)-th columns are 255, in association with  FIG. 2 .  FIG. 3  shows only the gradation data gr of the respective pixels  60  for convenience of understanding of the relation among the gradation data gr of the respective pixels  60 . 
     Hereafter, the case in which the pixel n_m is set to the target pixel, the relation of α11=α12=α13=α14=α15=α16=α=17=α18 and the relation of β11=β12=β13=β14=β15=β16=β17=β18 are established, and the value calculated by α12×(gr_n_m+1−gr_n_m)+β12×(gr_n_m+2−gr_n_m) of Equation (1) becomes the maximum value will be described as follows. 
       FIG. 4  shows the gradation data gr of the respective pixels  60  when the correction coefficients α11 to α18 are set to 31 and the correction coefficients β11 to β18 are set to 31, for example, in association with  FIG. 3 . The signal processing unit  21  corrects the gradation data gr of the pixel  60   n _ m  to 62. The signal processing unit  21  corrects the gradation data gr of the pixels  60  of the m-th column to 62 in the same manner as the pixel  60   n _ m . When the pixel  60   n _ m− 1 of the (m−1)-th column at the n-th row is set to the target pixel, the signal processing unit  21  corrects the gradation data gr of the pixel  60   n _ m− 1 to 31. The signal processing unit  21  corrects the gradation data gr of the pixels  60  of the (m−1)-th column to 31 in the same manner as the pixel  60   n _ m− 1. 
     The verification result of the present inventor shows that, when the correction coefficients α11 to α18 are set to 31 and the correction coefficients β11 to β18 are set to 31, the gradations are excessively corrected. Therefore, an occurrence of disclination is prevented, but a reduction in contrast is found. 
       FIG. 5  shows the gradation data gr of the respective pixels  60  when the correction coefficients α11 to α18 are set to 31 and the correction coefficients β11 to β18 are set to 15, for example, in association with  FIG. 3 . The signal processing unit  21  corrects the gradation data gr of the pixel  60   n _ m  to 46. The signal processing unit  21  corrects the gradation data gr of the pixels  60  of the m-th column to 46 in the same manner as the pixel  60   n _ m . When the pixel  60   n _ m− 1 of the (m−1)-th column at the n-th row is set to the target pixel, the signal processing unit  21  corrects the gradation data gr of the pixel  60   n _ m− 1 to 15. The signal processing unit  21  corrects the gradation data gr of the pixels  60  of the (m−1)-th column to 15 in the same manner as the pixel  60   n _ m− 1. 
     The verification result of the present inventor shows that, when the correction coefficients α11 to α18 are set to 31 and the correction coefficients β11 to β18 are set to 15, a reduction in contrast and an occurrence of disclination are prevented. 
       FIG. 6  shows the gradation data gr of the respective pixels  60  when the correction coefficients α11 to α18 are set to 31 and the correction coefficients β11 to β18 are set to 7, for example, in association with  FIG. 3 . The signal processing unit  21  corrects the gradation data gr of the pixel  60   n _ m  to 38. The signal processing unit  21  corrects the gradation data gr of the pixels  60  of the m-th column to 38 in the same manner as the pixel  60   n _ m . When the pixel  60   n _ m− 1 of the (m−1)-th column at the n-th row is set to the target pixel, the signal processing unit  21  corrects the gradation data gr of the pixel  60   n _ m− 1 to 7. The signal processing unit  21  corrects the gradation data gr of the pixels  60  of the (m−1)-th column to 7 in the same manner as the pixel  60   n _ m− 1. 
     The verification result of the present inventor shows that, when the correction coefficients α11 to α18 are set to 31 and the correction coefficients β11 to β18 are set to 7, the gradation correction is insufficiently performed. Therefore, a reduction in contrast is prevented, but an occurrence of disclination cannot be sufficiently prevented. 
     Accordingly, in the relational expression of α=k×β, the coefficient k may be set to about 2. Moreover, the correction coefficients α and β and the coefficient k may be properly determined according to the configuration, the resolution, the pixel pitch and the like of the display pixel unit  30 . 
       FIG. 7  illustrates the case in which the gradation data gr of the pixels  60  in the top left area of  FIG. 7  are 0 and the gradation data gr of the pixels  60  in the bottom right area of  FIG. 7  are 255 in the video data VD, in association with  FIG. 2 .  FIG. 7  shows only the gradation data gr of the respective pixels  60 , for the convenience of understanding the relation among the gradation data gr of the respective pixels  60 . 
     Hereafter, the case in which the pixel n_m is set to the target pixel, the relation of α11=α12=α13=α14=α15=α16=α=17=α18 and the relation of β11=β12=β13=β14=β15=β16=β17=β18 are established, and the value calculated by α16×(gr_n+1_m+1−gr_n_m)+β16×(gr_n+2_m+2−gr_n_m) in Equation (1) becomes the maximum value will be described as follows. 
       FIG. 8  shows the gradation data gr of the respective pixels  60  when the correction coefficients α11 to α18 are set to 31 and the correction coefficients β11 to β18 are set to 15, for example, in association with  FIG. 7 . The signal processing unit  21  corrects the gradation data gr of the pixels  60   n _ m ,  60   n− 2_m+1,  60   n −2_m+2,  60   n −1_m,  60   n− 1_m+1,  60   n _ m− 1,  60   n +1_m−2,  60   n+ 1_m−1, and  60   n +2_m−2 to 46. The signal processing unit  21  corrects the gradation data gr of the pixels  60   n− 2_m−1,  60   n− 2_m,  60   n− 1_m−2,  60   n− 1_m−1, and  60   n _ m− 2 to 15. 
     When gradation correction is performed based on two peripheral pixels disposed in each of the horizontal direction and the vertical direction with respect to the target pixel, that is when gradation correction is not performed in the oblique direction, the gradation data gr of the pixels  60   n− 2_m+1,  60   n −1_m,  60   n _ m− 1, and  60   n +1_m−2 are corrected to 15. 
     On the other hand, when gradation correction is performed based on two peripheral pixels disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, a value obtained by performing an operation on the gradation data of the two peripheral pixels disposed in the oblique direction with respect to the target pixel becomes the maximum value in the image pattern of  FIG. 7 . Therefore, the gradation data gr of the pixels  60   n− 2_m+1,  60   n −1_m,  60   n _ m− 1, and  60   n +1_m−2 are corrected to 46. 
     Furthermore, when gradation correction is performed based on two peripheral pixels disposed in each of the horizontal direction and the vertical direction with respect to the target pixel, the gradation data gr of the pixels  60   n− 2_m,  60   n− 2_m−1,  60   n− 1_m−1,  60   n− 1_m−2, and  60   n _ m− 2 are corrected to 0. 
     On the other hand, when gradation correction is performed based on two peripheral pixels disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, a value obtained by performing an operation on the gradation data of two peripheral pixels disposed in the oblique direction with respect to the target pixel becomes the maximum value in the image pattern of  FIG. 7 . Therefore, the gradation data gr of the pixels  60   n− 2_m,  60   n− 2_m−1,  60   n− 1_m−1,  60   n− 1_m−2, and  60   n _ m− 2 are corrected to 15. 
     Therefore, the display device  11  and the display method according to a first embodiment can perform gradation correction based on the difference between the gradation data of the target pixel and the gradation data of two peripheral pixels disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, such that the difference in gradation data between the target pixel and the peripheral pixels can be reduced for two peripheral pixels, which makes it possible to prevent an occurrence of disclination. 
     Furthermore, since the display device  11  and the display method according to a first embodiment can perform gradation correction based on the difference between the gradation data of the target pixel and the gradation data of two peripheral pixels disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, the display device  11  and the display method can prevent an occurrence of disclination in various image patterns, compared to when gradation correction is performed based on the difference between the gradation data of the target pixel and the gradation data of two peripheral pixels disposed in each of the horizontal direction and the vertical direction. 
     The direction in which disclination easily occurs may differ depending on the design specification of the display device  11  or each of the display devices  11 . The display device  11  and the display method according to a first embodiment perform gradation correction based on the difference between the gradation data of the target pixel and the gradation data of two peripheral pixels disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel. Therefore, the display device  11  and the display method can prevent an occurrence of disclination in various image patterns, even when the direction in which disclination easily occurs differ depending on the design specification of the display device  11  and each of the display devices  11 . 
     Moreover, when the direction in which disclination easily occurs is confirmed in advance, the display device  11  and the display method may perform gradation correction based on a difference between the gradation data of the target pixel and the gradation data of only two peripheral pixels disposed in the direction in which disclination easily occurs, with respect to the target pixel. 
     Second Embodiment 
     As illustrated in  FIG. 1 , a display device  12  according to a second embodiment includes a signal processing unit  22  instead of the signal processing unit  21 , and a display method through the signal processing unit  22 , specifically a gradation correction method for video data VD is different from the display method through the signal processing unit  21 . Therefore, the gradation correction method for video data VD through the signal processing unit  22  will be described. For convenience of description, the same components as those of the display device  11  according to a first embodiment are represented by the same reference numerals. 
     The signal processing unit  22  performs a gradation correction process on gradation data inputted to the respective pixels  60 . Specifically, the signal processing unit  22  calculates a difference between the gradation data of a target pixel and the gradation data of two peripheral pixels disposed in a horizontal direction, a vertical direction, and an oblique direction with respect to the target pixel, based on Equation (2). Then, the signal processing unit  22  specifies the maximum value from the calculation results, and sets the maximum value to a correction value CV for the target pixel. 
     
       
         
           
             
               
                 
                   
                     
                       CV 
                       — 
                     
                     ⁢ 
                     
                       n 
                       — 
                     
                     ⁢ 
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                     ⁡ 
                     
                       ( 
                       
                         
                           
                             
                               
                                 
                                   
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                   ) 
                 
               
             
           
         
       
     
     Here, α (α21 to α28) represents a correction coefficient (first correction coefficient) for a peripheral pixel  60  (first peripheral pixel) close to the target pixel between two pixels, and β (β21 to β28) represents a correction coefficient (second correction coefficient) for a peripheral pixel  60  (second peripheral pixel) far from the target pixel. The correction coefficients α and β are variables equal to or more than 0, respectively. The correction coefficients α and β are expressed as a relational expression of α=k×β (k≥1). That is, a weight equal to or more than that of the peripheral pixel  60  far from the target pixel is applied to the peripheral pixel  60  close to the target pixel. 
     The signal processing unit  22  determines a correction value CV corresponding to the target pixel, based on a difference between the gradation data of the target pixel and the gradation data of the first peripheral pixel adjacent to the target pixel and the second peripheral pixel adjacent to the first peripheral pixel among the plurality of pixels  60 . The signal processing unit  22  increases the pixel value of the target pixel by adding the correction value CV to the gradation data of the target pixel, thereby decreasing the difference. The pixel value is a gradation value, for example. 
     The signal processing unit  22  calculates a difference in a plurality of peripheral pixels disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, specifies the maximum value from the calculation results, and sets the maximum value to the correction value CV. 
     The signal processing unit  22  calculates the difference based on the correction coefficients α21 to α28 and β21 to β28 depending on the direction in which the peripheral pixels are disposed with respect to the target pixel or the distances between the target pixel and the peripheral pixels, specifies the maximum value from the calculation results, and sets the maximum value to the correction value CV for the target pixel. Furthermore, a relation of α21=α22=α23=α24=α25=α26=α=27=α28 and a relation of β21=β22=β23=024=β25=β26=β27=β28 may be set. 
     For example, when the pixel  60   n _ m  of the m-th column at the n-th row is set to the target pixel, the signal processing unit  22  calculates a difference between the gradation data of the pixel  60   n _ m  and the gradation data of two peripheral pixels disposed in each of the horizontal direction, the vertical direction and the oblique direction with respect to the pixel  60   n _ m  set to the target pixel, based on Equation (2). The signal processing unit  22  specifies the maximum value MAX from the calculation results, and sets the maximum value MAX to a correction value CV_n_m for the pixel  60   n _ m . In the following descriptions, the horizontal direction may be set to the right direction or the left direction, the vertical direction may be set to the top direction or the bottom direction, and the oblique direction may be set to the top right direction, the bottom right direction, the bottom left direction, or the top left direction. 
     Specifically, the signal processing unit  22  calculates a difference between the gradation data of the pixel  60   n _ m  and the gradation data of the peripheral pixels  60   n− 1_m and  60   n− 2_m disposed in the top direction with respect to the pixel  60   n _ m  set to the target pixel, based on an operation expression of α21×(gr_n−1_m−gr_n_m)+β21×(gr_n−2_m−gr_n_m)} in Equation (2). The signal processing unit  22  calculates a difference between the gradation data of the pixel  60   n _ m  and the gradation data of the peripheral pixels  60   n _ m+ 1 and  60   n _ m+ 2 disposed in the right direction with respect to the pixel  60   n _ m , based on an operation expression of {α22×(gr_n_m+1−gr_n_m)+β22×(gr_n_m+2−gr_n_m)} in Equation (2). 
     The signal processing unit  22  calculates a difference between the gradation data of the pixel  60   n _ m  and the gradation data of the peripheral pixels  60   n+ 1_m and  60   n+ 2_m disposed in the bottom direction with respect to the pixel  60   n _ m , based on an operation expression of α23×(gr_n+1_m−gr_n_m)+β23×(gr_n+2_m−gr_n_m) in Equation (2). The signal processing unit  22  calculates a difference between the gradation data of the pixel  60   n _ m  and the gradation data of the peripheral pixels  60   n _ m− 1 and  60   n _ m− 2 disposed in the left direction with respect to the pixel  60   n _ m , based on an operation expression of α24×(gr_n_m−1−gr_n_m)+β24×(gr_n_m−2−gr_n_m) in Equation (2). 
     The signal processing unit  22  calculates a difference between the gradation data of the pixel  60   n _ m  and the gradation data of the peripheral pixels  60   n− 1_m+1 and  60   n −2_m+2 disposed in the top right direction with respect to the pixel  60   n _ m , based on an operation expression of α25×(gr_n−1_m+1−gr_n_m)+β25×(gr_n−2_m+2−gr_n_m) in Equation (2). The signal processing unit  22  calculates a difference between the gradation data of the pixel  60   n _ m  and the gradation data of the peripheral pixels  60   n +1_m+1 and  60   n +2_m+2 disposed in the bottom right direction with respect to the pixel  60   n _ m , based on an operation expression of α26×(gr_n+1_m+1−gr_n_m)+β26×(gr_n+2_m+2−gr_n_m) in Equation (2). 
     The signal processing unit  22  calculates a difference between the gradation data of the pixel  60   n _ m  and the gradation data of the peripheral pixels  60   n+ 1_m−1 and  60   n+ 2_m−2 disposed in the bottom left direction with respect to the pixel  60   n _ m , based on an operation expression of α27×(gr_n+1_m−1−gr_n_m)+β27×(gr_n+2_m−2−gr_n_m) in Equation (2). The signal processing unit  22  calculates a difference between the gradation data of the pixel  60   n _ m  and the gradation data of the peripheral pixels  60   n− 1_m−1 and  60   n− 2_m−2 disposed in the top left direction with respect to the pixel  60   n _ m , based on an operation expression of α28×(gr_n−1_m−1−gr_n_m)+β28×(gr_n−2_m−2−gr_n_m) in Equation (2). 
     The signal processing unit  22  specifies the maximum value MAX from the calculation results, and sets the maximum value MAX to a correction value CV_n_m for the pixel  60   n _ m . The signal processing unit  22  corrects the gradation data of the pixel  60   n _ m  into gradation data obtained by adding the correction value CV_n_m to the gradation data gr_n_m of the pixel  60   n _ m  in the video data VD. That is, the signal processing unit  22  determines the correction value CV corresponding to the target pixel, based on the difference between the gradation data of the target pixel and the gradation data of two peripheral pixels disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel among the plurality of pixels  60 . The signal processing unit  22  increases the pixel value of the target pixel by adding the correction value CV to the gradation data of the target pixel, thereby decreasing the difference. 
     The signal processing unit  22  determines the correction value CV corresponding to the target pixel, based on the differences between the gradation data of the target pixel and the gradation data of the two peripheral pixels disposed in the right direction with respect to the target pixel, the gradation data of the two peripheral pixels disposed in the left direction with respect to the target pixel, the gradation data of the two peripheral pixels disposed in the top direction with respect to the target pixel, the gradation data of the two peripheral pixels disposed in the bottom direction with respect to the target pixel, the gradation data of the two peripheral pixels disposed in the top right direction with respect to the target pixel, the gradation data of the two peripheral pixels disposed in the bottom right direction with respect to the target pixel, the gradation data of the two peripheral pixels disposed in the bottom left direction with respect to the target pixel, and the gradation data of the two peripheral pixels disposed in the top left direction with respect to the target pixel. The signal processing unit  22  increases the pixel value of the target pixel by adding the correction value CV to the gradation data of the target pixel, thereby decreasing the differences. 
     The signal processing unit  22  performs the same gradation correction process as the pixel  60   n _ m  on the whole pixels  60  of the display pixel unit  30 . The signal processing unit  22  generates gradation corrected video data SVD by performing the gradation correction process on the whole pixels  60  in the video data VD, and outputs the gradation corrected video data SVD to the horizontal scanning circuit  40 . 
     The signal processing unit  22  sets the correction coefficients α and β based on the differences in gradation data between the peripheral pixels and the target pixel. For example, the signal processing unit  22  sets the correction coefficients α (α21 to α28) and the correction coefficients β (β21 to β28), based on a lookup table in which the differences in gradation data between the peripheral pixels and the target pixel are associated with the correction coefficients α (α21 to α28) and the correction coefficients β (β21 to β28). The lookup table may be stored in the signal processing unit  22 , or stored in any memory unit except the signal processing unit  22 . 
     Specifically, the signal processing unit  22  sets the correction coefficient α21 based on a gradation data difference (gr_n−1_m−gr_n_m) between the peripheral pixel  60   n− 1_m and the target pixel  60   n _ m . The signal processing unit  22  sets the correction coefficient α22 based on a gradation data difference (gr_n_m+1−gr_n_m) between the peripheral pixel  60   n _ m+ 1 and the target pixel  60   n _ m . The signal processing unit  22  sets the correction coefficient α23 based on a gradation data difference (gr_n+1_m−gr_n_m) between the peripheral pixel  60   n +1_m and the target pixel  60   n _ m . The signal processing unit  22  sets the correction coefficient α24 based on a gradation data difference (gr_n_m−1−gr_n_m) between the peripheral pixel  60   n _ m− 1 and the target pixel  60   n _ m.    
     The signal processing unit  22  sets the correction coefficient α25 based on a gradation data difference (gr_n−1_m+1 gr_n_m) between the peripheral pixel  60   n −1_m+1 and the target pixel  60   n _ m . The signal processing unit  22  sets the correction coefficient α26 based on a gradation data difference (gr_n+1_m+1−gr_n_m) between the peripheral pixel  60   n +1_m+1 and the target pixel  60   n _ m . The signal processing unit  22  sets the correction coefficient α27 based on a gradation data difference (gr_n+1_m−1−gr_n_m) between the peripheral pixel  60   n+ 1_m−1 and the target pixel  60   n _ m . The signal processing unit  22  sets the correction coefficient α28 based on a gradation data difference (gr_n−1_m−1−gr_n_m) between the peripheral pixel  60   n− 1_m−1 and the target pixel  60   n _ m.    
     The signal processing unit  22  sets the correction coefficient β21 based on a gradation data difference (gr_n−2_m−gr_n_m) between the peripheral pixel  60   n− 2_m and the target pixel  60   n _ m . The signal processing unit  22  sets the correction coefficient β22 based on a gradation data difference (gr_n_m+2−gr_n_m) between the peripheral pixel  60   n _ m+ 2 and the target pixel  60   n _ m . The signal processing unit  22  sets the correction coefficient β23 based on a gradation data difference (gr_n+2_m−gr_n_m) between the peripheral pixel  60   n+ 2_m and the target pixel  60   n _ m . The signal processing unit  22  sets the correction coefficient β24 based on a gradation data difference (gr_n_m−2−gr_n_m) between the peripheral pixel  60   n _ m− 2 and the target pixel  60   n _ m.    
     The signal processing unit  22  sets the correction coefficient β25 based on a gradation data difference (gr_n−2_m+2−gr_n_m) between the peripheral pixel  60   n −2_m+2 and the target pixel  60   n _ m . The signal processing unit  22  sets the correction coefficient β26 based on a gradation data difference (gr_n+2_m+2−gr_n_m) between the peripheral pixel  60   n+ 2_m+2 and the target pixel  60   n _ m . The signal processing unit  22  sets the correction coefficient β27 based on a gradation data difference (gr_n+2_m−2−gr_n_m) between the peripheral pixel  60   n+ 2_m−2 and the target pixel  60   n _ m . The signal processing unit  22  sets the correction coefficient β28 based on a gradation data difference (gr_n−2_m−2−gr_n_m) between the peripheral pixel  60   n− 2_m−2 and the target pixel  60   n _ m.    
       FIG. 9  illustrates the relation between the correction coefficients α and β and the gradation data differences between the peripheral pixels and the target pixel, as a first example. In the first example, the correction coefficients α and β have a relation of α=β. Thus, when the differences in gradation data between the peripheral pixels and the target pixel are 255, the correction coefficients α and β become 47 (α=β=47). 
     As illustrated in  FIG. 3 , when the gradation data gr of the pixels  60  of the (m−2)-th to m-th columns in the video data VD are 0 and the gradation data gr of the pixels  60  of the (m+1)-th and (m+2)-th columns are 255, the signal processing unit  22  sets the correction coefficients α21 to α28 and β21 to β28 to 47 (α21 to α28=β21 to (328=47), based on a lookup table in which the differences in gradation data between the peripheral pixels and the target pixel and the correction coefficients α21 to α28 and β21 to β28 are associated as illustrated in the graph of  FIG. 9 . 
     When the pixel  60   n _ m  is set to the target pixel, the signal processing unit  22  calculates the gradation data of the peripheral pixels  60   n _ m+ 1 and  60   n _ m+ 2 disposed in the right direction with respect to the pixel  60   n _ m , based on an operation expression of α22×(gr_n_m+1−gr_n_m)+β22×(gr_n_m+2−gr_n_m) in Equation (2). 
       FIG. 10  shows the gradation data gr of the respective pixels  60 , in association with  FIG. 3 . The signal processing unit  22  corrects the gradation data gr_n_m of the pixel  60   n _ m  to 94. The signal processing unit  22  corrects the gradation data gr of the pixels  60  of the m-th column to 94 in the same manner as the pixel  60   n _ m . When the pixel  60   n _ m− 1 is set to the target pixel, the signal processing unit  22  corrects the gradation data gr of the pixel  60   n _ m− 1 to 47. The signal processing unit  22  corrects the gradation data gr of the pixels  60  of the (m−1)-th column to 47 in the same manner as the pixel  60   n _ m− 1. 
       FIG. 11  illustrates the relation between the correction coefficients α and β and the differences in gradation data between the peripheral pixels and the target pixel, as a second example. In the second example, the correction coefficients α and β become 63 and 31 (α=63 and β=31), when the differences in gradation data between the peripheral pixels and the target pixel are 255. That is, in the relational expression of α=k×β, the coefficient k is set to about 2. 
     As illustrated in  FIG. 3 , when the gradation data gr of the pixels  60  of the (m−2)-th to m-th columns in the video data VD are 0 and the gradation data gr of the pixels  60  of the (m+1)-th and (m+2)-th columns are 255, the signal processing unit  22  sets the correction coefficients α21 to α28 to 63 and sets the correction coefficients and β21 to β28 to 31, based on a lookup table in which the differences in gradation data between the peripheral pixels and the target pixel and the correction coefficients α21 to α28 and β21 to β28 are associated as illustrated in the graph of  FIG. 11 . 
     When the pixel  60   n _ m  is set to the target pixel, the signal processing unit  22  calculates the gradation data of the peripheral pixels  60   n _ m+ 1 and  60   n _ m+ 2 disposed in the right direction with respect to the pixel  60   n _ m , based on an operation expression of α22×(gr_n_m+1−gr_n_m)+β22×(gr_n_m+2−gr_n_m) in Equation (2). 
       FIG. 12  shows the gradation data gr of the respective pixels  60 , in association with  FIG. 3 . The signal processing unit  22  corrects the gradation data gr_n_m of the pixel  60   n _ m  to 94. The signal processing unit  22  corrects the gradation data gr of the pixels  60  of the m-th column to 94 in the same manner as the pixel  60   n _ m . When the pixel  60   n _ m− 1 is set to the target pixel, the signal processing unit  22  corrects the gradation data gr_n_m−1 of the pixel  60   n _ m− 1 to 31. The signal processing unit  22  corrects the gradation data gr of the pixels  60  of the (m−1)-th column to 31 in the same manner as the pixel  60   n _ m− 1. 
       FIG. 13  illustrates the relation between the correction coefficients α and β and the differences in gradation data between the peripheral pixels and the target pixel, as a third example. In the third example, the correction coefficients α and β become 63 and 31 (α=63 and β=31) when the differences in gradation data between the peripheral pixels and the target pixel are 255. That is, in the relational expression α=k×β, the coefficient k is set to about 2. 
     As illustrated in  FIG. 3 , when the gradation data gr of the pixels  60  of the (m−2)-th to m-th columns in the video data VD are 0 and the gradation data gr of the pixels  60  of the (m+1)-th and (m+2)-th columns are 255, the signal processing unit  22  sets the correction coefficients α21 to α28 to 63 and sets the correction coefficients β21 to β28 to 31, based on a lookup table in which the differences in gradation data between the peripheral pixels and the target pixel and the correction coefficients α21 to α28 and β21 to β28 are associated as illustrated in the graph of  FIG. 13 . 
     When the pixel  60   n _ m  is set to the target pixel, the signal processing unit  22  calculates the gradation data of the peripheral pixels  60   n _ m+ 1 and  60   n _ m+ 2 disposed in the right direction with respect to the pixel  60   n _ m , based on an operation expression of {α22×(gr_n_m+1−gr_n_m)+β22×(gr_n_m+2−gr_n_m)} in Equation (2). 
       FIG. 14  shows the gradation data gr of the respective pixels  60 , in association with  FIG. 3 . The signal processing unit  22  corrects the gradation data gr_n_m of the pixel  60   n _ m  to 94. The signal processing unit  22  corrects the gradation data gr of the pixels  60  of the m-th column to 94 in the same manner as the pixel  60   n _ m . When the pixel  60   n _ m− 1 is set to the target pixel, the signal processing unit  22  corrects the gradation data gr_n_m−1 of the pixel  60   n _ m− 1 to 31. The signal processing unit  22  corrects the gradation data gr of the pixels  60  of the (m−1)-th column to 31 in the same manner as the pixel  60   n _ m− 1. 
     The lookup table is not limited to the first to third examples, but may be appropriately determined according to the configuration, resolution, or pixel pitch of the display pixel unit  30  in order to prevent a reduction in contrast and an occurrence of disclination. 
     Therefore, the display device  12  and the display method according to a second embodiment can perform gradation correction based on the difference between the gradation data of the target pixel and the gradation data of two peripheral pixels disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, such that the difference in gradation data between the target pixel and the peripheral pixels can be reduced with respect to two peripheral pixels, which makes it possible to prevent an occurrence of disclination. 
     Furthermore, since the display device  12  and the display method according to a second embodiment can perform gradation correction based on the difference between the gradation data of the target pixel and the gradation data of two peripheral pixels disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, the display device  12  and the display method can prevent an occurrence of disclination in various image patterns, compared to when gradation correction is performed based on a difference between the gradation data of the target pixel and the gradation data of two peripheral pixels disposed in each of the horizontal direction and the vertical direction. 
     The direction in which disclination easily occurs may differ depending on the design specification of the display device  12  or each of display devices  12 . The display device  12  and the display method according to a second embodiment perform gradation correction based on the difference between the gradation data of the target pixel and the gradation data of two peripheral pixels disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel. Therefore, the display device  12  and the display method can prevent an occurrence of disclination in various image patterns, even when the direction in which disclination easily occurs is different depending on the design specification of the display device  12  and each of display devices  12 . 
     Moreover, when the direction in which disclination easily occurs is confirmed in advance, the display device  12  and the display method may perform gradation correction based on a difference between the gradation data of the target pixel and the gradation data of only two peripheral pixels disposed in the direction in which disclination is likely to occur, with respect to the target pixel. 
     Third Embodiment 
     As illustrated in  FIG. 1 , a display device  13  according to a third embodiment includes a signal processing unit  23  instead of the signal processing unit  21 , and a display method through the signal processing unit  23  or specifically a gradation correction method for video data VD is different from that of the signal processing unit  21 . Therefore, the gradation correction method for video data VD through the signal processing unit  23  will be described. For convenience of the description, the same components as those of the display device  11  according to a first embodiment are represented by the same reference numerals. 
     The signal processing unit  23  performs a gradation correction process on gradation data inputted to the respective pixels  60 . Specifically, the signal processing unit  23  calculates a difference between gradation data of the target pixel and the gradation data of a peripheral pixel disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, based on Equation (3). Then, the signal processing unit  23  specifies the maximum value from the calculation results, and sets the maximum value to a correction value CV for the target pixel. 
     
       
         
           
             
               
                 
                   
                     
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     At this time, all to α18 of Equation (3) correspond to α11 to α18 of Equation (1). That is, Equation (3) corresponds to when β11 to β18 in Equation (1) are set to 0. For example, when the pixel  60   n _ m  of the m-th column at the n-th row is set to the target pixel, the signal processing unit  23  calculates differences between the gradation data of the target pixel and the gradation data of peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the pixel  60   n _ m  set to the target pixel, based on Equation (3). The signal processing unit  23  specifies the maximum value MAX from the calculation results, and sets the maximum value MAX to a correction value CV_n_m for the pixel  60   n _ m.    
     The signal processing unit  23  calculates the differences between the peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, respectively, specifies the maximum value from the calculation results, and sets the maximum value to the correction value CV. 
     The signal processing unit  23  calculates the differences based on the correction coefficients α11 to α18 depending on the directions in which the peripheral pixels are disposed with respect to the target pixel or the distances between the target pixel and the peripheral pixels, specifies the maximum value from the calculation results, and sets the maximum value to the correction value CV for the target pixel. In the following descriptions, the horizontal direction may be set to the right direction or the left direction, the vertical direction may be set to the top direction or the bottom direction, and the oblique direction may be set to the top right direction, the bottom right direction, the bottom left direction or the top left direction. 
     Specifically, the signal processing unit  23  calculates a difference between the gradation data of the target pixel and the gradation data of the peripheral pixel  60   n− 1_m disposed in the top direction with respect to the pixel  60   n _ m  set to the target pixel, based on an operation expression of α11×(gr_n−1_m−gr_n_m) in Equation (3). The signal processing unit  23  calculates a difference between the gradation data of the target pixel and the gradation data of the peripheral pixel  60   n _ m+ 1 disposed in the right direction with respect to the pixel  60   n _ m , based on an operation expression of α12×(gr_n_m+1−gr_n_m) in Equation (3). 
     The signal processing unit  23  calculates a difference between the gradation data of the target pixel and the gradation data of the peripheral pixel  60   n +1_m disposed in the bottom direction with respect to the pixel  60   n _ m , based on an operation expression of α13×(gr_n+1_m−gr_n_m) in Equation (3). The signal processing unit  23  calculates a difference between the gradation data of the target pixel and the gradation data of the peripheral pixel  60   n _ m− 1 disposed in the left direction with respect to the pixel  60   n _ m , based on an operation expression α14×(gr_n_m−1−gr_n_m) in Equation (3). 
     The signal processing unit  23  calculates a difference between the gradation data of the target pixel and the gradation data of the peripheral pixel  60   n− 1_m+1 disposed in the top right direction with respect to the pixel  60   n _ m , based on an operation expression of α15×(gr_n−1_m+1−gr_n_m) in Equation (3). The signal processing unit  23  calculates a difference between the gradation data of the target pixel and the gradation data of the peripheral pixel  60   n +1_m+1 disposed in the bottom right direction with respect to the pixel  60   n _ m , based on an operation expression of {α16×(gr_n+1_m+1−gr_n_m)} in Equation (3). 
     The signal processing unit  23  calculates a difference between the gradation data of the target pixel and the gradation data of the peripheral pixel  60   n +1_m−1 disposed in the bottom left direction with respect to the pixel  60   n _ m , based on an operation expression of α17×(gr_n+1_m−1−gr_n_m) in Equation (3). The signal processing unit  23  calculates a difference between the gradation data of the target pixel and the gradation data of the peripheral pixel  60   n− 1_m−1 disposed in the top left direction with respect to the pixel  60   n _ m , based on an operation expression of α18×(gr_n−1_m−1−gr_n_m) in Equation (3). 
     The signal processing unit  23  specifies the maximum value MAX from the calculation results, and sets the maximum value MAX to a correction value CV_n_m for the pixel  60   n _ m . The signal processing unit  23  corrects the gradation data of the pixel  60   n _ m  into gradation data obtained by adding the correction value CV_n_m to the gradation data gr_n_m of the pixel  60   n _ m  in the video data VD. That is, the signal processing unit  23  determines the correction value CV corresponding to the target pixel, based on the differences between the gradation data of the target pixel and the gradation data of the peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, respectively, among the plurality of pixels  60 . The signal processing unit  23  increases the pixel value of the target pixel by adding the correction value CV to the gradation data of the target pixel, thereby decreasing the differences. The pixel value is a gradation value, for example. 
     The signal processing unit  23  determines the correction value CV corresponding to the target pixel, based on the differences between the gradation data of the target pixel and the gradation data of the peripheral pixel disposed in the right direction with respect to the target pixel, the gradation data of the peripheral pixel disposed in the left direction with respect to the target pixel, the gradation data of the peripheral pixel disposed in the top direction with respect to the target pixel, the gradation data of the peripheral pixel disposed in the bottom direction with respect to the target pixel, the gradation data of the peripheral pixel disposed in the top right direction with respect to the target pixel, the gradation data of the peripheral pixel disposed in the bottom right direction with respect to the target pixel, the gradation data of the peripheral pixel disposed in the bottom left direction with respect to the target pixel, and the gradation data of the peripheral pixel disposed in the top left direction with respect to the target pixel, respectively. The signal processing unit  23  increases the pixel value of the target pixel by adding the correction value CV to the gradation data of the target pixel, thereby decreasing the differences. 
     The signal processing unit  23  performs the same gradation correction process as the pixel  60   n _ m  on the whole pixels  60  of the display pixel unit  30 . The signal processing unit  23  generates gradation corrected video data SVD by performing a gradation correction process on the whole pixels  60  in the video data VD, and outputs the gradation corrected video data SVD to the horizontal scanning circuit  40 . 
     When gradation correction is performed based on differences in gradation data between the target pixel and peripheral pixels disposed in the horizontal direction and the vertical direction with respect to the target pixel, that is when gradation correction is not performed based on differences in gradation data between the target pixel and peripheral pixels disposed in the oblique direction, the signal processing unit  23  corrects the gradation data of the pixels  60   n −2_m+2,  60   n −1_m+1,  60   n  m,  60   n +1_m−1, and  60   n+ 2_m−2 to 31, as illustrated in  FIG. 15 . 
     On the other hand, when gradation correction is performed based on the differences in gradation data between the target pixel and the peripheral pixels disposed in the horizontal direction, the vertical direction and the oblique direction with respect to the target pixel, the differences between the gradation data of the target pixel and the gradation data of the peripheral pixels disposed in the oblique direction with respect to the target pixel becomes the maximum value in the image pattern of  FIG. 7 . 
     Therefore, as illustrated in  FIG. 16 , the signal processing unit  23  corrects the gradation data gr of the pixels  60   n− 2_m+2,  60   n −1_m+1,  60   n _ m ,  60   n +1_m−1,  60   n+ 2_m−2,  60   n− 2_m+1,  60   n −1_m,  60   n _ m− 1, and  60   n +1_m−2 to 31. 
     Accordingly, the display device  13  and the display method according to a third embodiment can perform gradation correction based on the differences between the gradation data of the target pixel and the gradation data of the peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, and thus reduce the differences in the gradation data between the target pixel and the peripheral pixels, which makes it possible to prevent an occurrence of disclination. 
     Furthermore, since the display device  13  and the display method according to a third embodiment can perform gradation correction based on the differences between the gradation data of the target pixel and the gradation data of the peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, the display device  13 , and the display method can prevent an occurrence of disclination in various image patterns, compared to when gradation correction is performed based on the differences between the gradation data of the target pixel and the gradation data of the peripheral pixels disposed in the horizontal direction and the vertical direction. 
       FIGS. 17A to 17D  illustrate the pixels  60  of the (n−2)-th to (n+1)-th rows and the (m−2)-th to (m+6)-th columns of the display pixel unit  30  of  FIG. 1 .  FIGS. 17A to 17D  schematically illustrate an example of images which are successively displayed for each frame when gradation correction is not performed.  FIG. 17A  illustrates a display image of a first frame,  FIG. 17B  illustrates a display image of a second frame,  FIG. 17C  illustrates a display image of a third frame, and  FIG. 17D  illustrates a display image of a fourth frame. 
       FIG. 17A  illustrates that the pixels  60  of the (m−2)-th and (m−1)-th columns in the video data VD are displayed in white (for example, gr=0), and the pixels  60  of the m-th to (m+6)-th columns are displayed in black (for example, gr=255). In the image pattern illustrated in  FIG. 17A , the pixels  60  in the boundary portion between the (m−1)-th and m-th columns have a large potential difference. Therefore, when gradation correction is not performed, disclination may occur around the boundary portion of the pixels  60  of the (m−1)-th column. 
       FIG. 17B  illustrates that the boundary portion between white display and black display is shifted to the right by one column from the state of  FIG. 17A .  FIG. 17C  illustrates that the boundary portion between white display and black display is further shifted to the right by one column from the state of  FIG. 17B .  FIG. 17D  illustrates that the boundary portion between white display and black display is further shifted to the right by one column from the state of  FIG. 17C . 
     As illustrated in  FIGS. 17A to 17D , if gradation correction is not performed, disclination occurs around the boundary portion between white display and black display whenever the boundary portion between white display and black display is shifted to the right by one column. Since the disclination does not immediately disappear, tailing occurs to degrade the quality of the display image. 
       FIGS. 18A to 18D  schematically illustrate an example of images which are successively displayed for each frame when gradation correction is performed based on the peripheral pixels disposed in the horizontal direction and the vertical direction with respect to the target pixel.  FIGS. 18A to 18D  correspond to  FIGS. 17A to 17D . 
     As illustrated in  FIGS. 18A to 18D , the gradation correction is performed based on the peripheral pixels disposed in the horizontal direction and the vertical direction with respect to the target pixel, in order to reduce differences in gradation data between the target pixel and the peripheral pixels. Therefore, in the image patterns illustrated in  FIGS. 18A to 18D , an occurrence of disclination can be prevented. 
       FIGS. 19A to 19D  schematically illustrate an example of images that are successively displayed for each frame when gradation correction is performed based on the peripheral pixels disposed in the horizontal direction, the vertical direction and the oblique direction with respect to the target pixel.  FIGS. 19A to 19D  correspond to  FIGS. 17A to 17D  and  FIGS. 18A to 18D . 
     As illustrated in  FIGS. 19A to 19D , the gradation correction is performed based on the peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, in order to reduce differences in gradation data between the target pixel and the peripheral pixels. Therefore, in the image patterns illustrated in  FIGS. 19A to 19D , an occurrence of disclination can be prevented. 
       FIGS. 20A to 20D  illustrate the pixels  60  of the (n−2)-th to (n+1)-th rows and the (m−2)-th to (m+6)-th columns of the display pixel unit  30  of  FIG. 1 .  FIGS. 20A to 20D  schematically illustrate an example of images which are successively displayed for each frame when gradation correction is not performed.  FIG. 20A  illustrates a display image of a first frame,  FIG. 20B  illustrates a display image of a second frame,  FIG. 20C  illustrates a display image of a third frame, and  FIG. 20D  illustrates a display image of a fourth frame.  FIGS. 20A to 20D  illustrate image patterns different from those of  FIGS. 17A to 17D . 
       FIG. 20A  illustrates that the pixels  60  of the (n−2)-th to (n+1)-th rows at the (m−2)-th to (m−1)-th columns, the pixels  60  of the (n−1)-th to (n+1)-th rows at the m-th column, the pixels  60  of the n-th and (n+1)-th rows at the (m+1)-th column, and the pixels  60  of the (n+1)-th row at the (m+2)-th column in the video data VD are displayed in white, and the other pixels  60  are displayed in black. In the image pattern illustrated in  FIG. 20A , the pixels  60  in the boundary portion between the pixels  60  displayed in white and the pixels  60  displayed in black have a large potential difference therebetween. Therefore, when gradation correction is not performed, disclination may occur around the boundary portion. 
       FIG. 20B  illustrates that the boundary portion between white display and black display is shifted to the right by one column from the state of  FIG. 20A .  FIG. 20C  illustrates that the boundary portion between white display and black display is further shifted to the right by one column from the state of  FIG. 20B .  FIG. 20D  illustrates that the boundary portion between white display and black display is further shifted to the right by one column from the state of  FIG. 20C . 
     As illustrated in  FIGS. 20A to 20D , if gradation correction is not performed, disclination occurs around the boundary portion between white display and black display whenever the boundary portion between white display and black display is shifted to the right by one column. Since the disclination does not immediately disappear, tailing occurs to degrade the quality of the display image. 
       FIGS. 21A to 21D  schematically illustrate an example of images which are successively displayed for each frame when gradation correction is performed based on the peripheral pixels disposed in the horizontal direction and the vertical direction with respect to the target pixel.  FIGS. 21A to 21D  correspond to  FIGS. 20A to 20D . 
     As illustrated in  FIGS. 21A to 21D , when gradation correction is performed based on the peripheral pixels disposed in the horizontal direction and the vertical direction with respect to the target pixel, an occurrence of disclination can be reduced, compared to when gradation correction is not performed. However, an occurrence of disclination cannot be sufficiently prevented, due to the influence of the peripheral pixels disposed in the oblique direction with respect to the target pixel. 
       FIGS. 22A to 22D  schematically illustrate an example of images that are successively displayed for each frame when gradation correction is performed based on peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel.  FIGS. 22A to 22D  correspond to  FIGS. 20A to 20D  and  FIGS. 21A to 21D . 
     As illustrated in  FIGS. 22A to 22D , the gradation correction can be performed based on the peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, in order to reduce the differences in gradation data between the target pixel and the peripheral pixels disposed in the oblique direction with respect to the target pixel. Therefore, in the image patterns illustrated in  FIGS. 22A to 22D , an occurrence of disclination can be prevented. 
     The direction in which disclination easily occurs may differ depending on the design specification of the display device  13  or each of display devices  13 . The display device  13  and the display method according to a third embodiment perform gradation correction based on the peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel. Therefore, the display device  13  and the display method can prevent an occurrence of disclination in various image patterns, even when the direction in which disclination easily occurs is different depending on the design specification of the display device  13  and each of display devices  13 . 
     When the direction in which disclination easily occurs is confirmed in advance, the display device  13  and the display method may perform gradation correction based on only peripheral pixels adjacent to the target pixel in the direction that disclination easily occurs. 
     Fourth Embodiment 
     As illustrated in  FIG. 1 , a display device  14  according to a fourth embodiment includes a signal processing unit  24  instead of the signal processing unit  22 , and a display method through the signal processing unit  24  or specifically a gradation correction method for video data VD is different from the display method through the signal processing unit  22 . Therefore, the gradation correction method for video data VD through the signal processing unit  24  will be described. For convenience of the description, the same components as those of the display device  12  according to a second embodiment are represented by the same reference numerals. 
     The signal processing unit  24  performs a gradation correction process on gradation data inputted to the respective pixels  60 . Specifically, the signal processing unit  24  calculates gradation data of peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to a target pixel, based on Equation (4). Then, the signal processing unit  24  specifies the maximum value from the calculation results, and sets the maximum value to a correction value CV for the target pixel. 
     
       
         
           
             
               
                 
                   
                     
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     The correction coefficients α21 to α28 of Equation (4) correspond to the correction coefficients α21 to α28 of Equation (2). That is, Equation (4) corresponds to when the correction coefficients β21 to β28 are zero in Equation (2). For example, when the pixel  60   n _ m  of the m-th column at the n-th row is set to the target pixel, the signal processing unit  24  calculates the gradation data of peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the pixel  60   n _ m  set to the target pixel, based on Equation (4). The signal processing unit  24  specifies the maximum value MAX from the calculation results, and sets the maximum value MAX to a correction value CV_n_m in the pixel  60   n  m. 
     The signal processing unit  24  calculates differences between the peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, specifies the maximum value from the calculation results, and sets the maximum value to the correction value CV. 
     The signal processing unit  24  calculates the differences based on the correction coefficients α21 to α28 depending on the directions in which the peripheral pixels are disposed with respect to the target pixel or the distances between the target pixel and the peripheral pixels, specifies the maximum value from the calculation results, and sets the maximum value to the correction value CV for the target pixel. In the following descriptions, the horizontal direction may be set to the right direction or the left direction, the vertical direction may be set to the top direction or the bottom direction, and the oblique direction may be set to the top right direction, the bottom right direction, the bottom left direction, or the top left direction. 
     Specifically, the signal processing unit  24  calculates the gradation data of the peripheral pixel  60   n −1_m disposed in the top direction with respect to the pixel  60   n _ m  set to the target pixel, based on an operation expression of α21×(gr_n−1_m−gr_n_m) in Equation (4). The signal processing unit  24  calculates the gradation data of the peripheral pixel  60   n _ m+ 1 disposed in the right direction with respect to the pixel  60   n _ m , based on an operation expression of α22×(gr_n−1_m+1−gr_n_m) in Equation (4). 
     The signal processing unit  24  calculates the gradation data of the peripheral pixel  60   n +1_m disposed in the bottom direction with respect to the pixel  60   n _ m , based on an operation expression of α23×(gr_n+1_m−gr_n_m) in Equation (4). The signal processing unit  24  calculates the gradation data of the peripheral pixel  60   n _ m− 1 disposed in the left direction with respect to the pixel  60   n _ m , based on an operation expression of α24×(gr_n_m−1−gr_n_m) in Equation (4). 
     The signal processing unit  24  calculates the gradation data of the peripheral pixel  60   n− 1_m+1 disposed in the top right direction with respect to the pixel  60   n _ m , based on an operation expression of α25×(gr_n−1_m+1−gr_n_m) in Equation (4). The signal processing unit  24  calculates the gradation data of the peripheral pixel  60   n +1_m+1 disposed in the bottom right direction with respect to the pixel  60   n _ m , based on an operation expression of α26×(gr_n+1_m+1−gr_n_m) in Equation (4). 
     The signal processing unit  24  calculates the gradation data of the peripheral pixel  60   n +1_m−1 disposed in the bottom left direction with respect to the pixel  60   n _ m , based on an operation expression of α27×(gr_n+1_m−1−gr_n_m) in Equation (4). The signal processing unit  24  calculates the gradation data of the peripheral pixel  60   n −1_m−1 disposed in the top left direction with respect to the pixel  60   n _ m , based on an operation expression of α28×(gr_n−1_m−1−gr_n_m) in Equation (4). The method for setting the correction coefficients α21 to α28 may be performed in the same manner as the method for setting the correction coefficients α21 to α28 according to a second embodiment. 
     The signal processing unit  24  specifies the maximum value MAX from the calculation results, and sets the maximum value MAX to a correction value CV_n_m for the pixel  60   n _ m . The signal processing unit  24  corrects the gradation data of the pixel  60   n _ m  to gradation data obtained by adding the correction value CV_n_m to the gradation data gr_n_m of the pixel  60   n _ m  in the video data VD. That is, the signal processing unit  24  determines the correction value CV corresponding to the target pixel, based on the gradation data of the peripheral pixels disposed in the horizontal direction, the vertical direction and the oblique direction with respect to the target pixel, respectively, among the plurality of pixels  60 . The signal processing unit  24  increases the pixel value of the target pixel by adding the correction value CV to the gradation data of the target pixel, thereby decreasing the differences in gradation data between the target pixel and the peripheral pixels. The pixel value is a gradation value, for example. 
     The signal processing unit  24  determines the correction value CV corresponding to the target pixel, based on the gradation data of the peripheral pixel disposed in the right direction, the gradation data of the peripheral pixel disposed in the left direction, the gradation data of the peripheral pixel disposed in the top direction, the gradation data of the peripheral pixel disposed in the bottom direction, the gradation data of the peripheral pixel disposed in the top right direction, the gradation data of the peripheral pixel disposed in the bottom right direction, the gradation data of the peripheral pixel disposed in the bottom left direction, and the gradation data of the peripheral pixel disposed in the top left direction, with respect to the target pixel. The signal processing unit  24  increases the pixel value of the target pixel by adding the correction value CV to the gradation data of the target pixel, thereby decreasing the differences. 
     The signal processing unit  24  performs the same gradation correction process as the pixel  60   n _ m  on the whole pixels  60  of the display pixel unit  30 . The signal processing unit  24  generates gradation corrected video data SVD by performing a gradation correction process on the whole pixels  60  in the video data VD, and outputs the gradation corrected video data SVD to the horizontal scanning circuit  40 . 
     Therefore, the display device  14  and the display method according to a fourth embodiment can perform gradation correction based on the peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, and thus reduce the differences in gradation data between the target pixel and the peripheral pixels. Thus, the display device  14  and the display method can prevent an occurrence of disclination. 
     Furthermore, since the display device  14  and the display method according to a fourth embodiment can perform gradation correction based on the peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, the display device  14  and the display method can prevent an occurrence of disclination in various image patterns, compared to when gradation correction is performed based on the peripheral pixels disposed in the horizontal direction and the vertical direction. 
     In the display device  14  and the display method according to a fourth embodiment, the same display images as the display images illustrated in  FIGS. 17A to 17D ,  FIGS. 18A to 18D ,  FIGS. 19A to 19D ,  FIGS. 20A to 20D ,  FIGS. 21A to 21D , and  FIGS. 22A to 22D  are confirmed. 
     The direction in which disclination easily occurs may differ depending on the design specification of the display device  14  or each of display devices  14 . The display device  14  and the display method according to a fourth embodiment perform gradation correction based on the peripheral pixels disposed in the horizontal direction, the vertical direction and the oblique direction with respect to the target pixel. Therefore, the display device  14  and the display method can prevent an occurrence of disclination in various image patterns, even when the direction in which disclination easily occurs is different depending on the design specification of the display device  14  and each of display devices  14 . 
     When the direction in which disclination easily occurs is confirmed in advance, the display device  14  and the display method may perform gradation correction based on only peripheral pixels adjacent to the target pixel in the direction that disclination easily occurs. 
     The present invention is not limited to the above-described one or more embodiments, but can be modified in various manners without departing the scope of the present invention. 
     In the display devices  11  and  12  and the display methods according to first and second embodiments, the signal processing units  21  and  22  calculate the gradation data of two peripheral pixels disposed in each of the horizontal direction, the vertical direction and the oblique direction with respect to the target pixel, specify the maximum value MAX from the calculation results, and set the maximum value MAX to the correction value CV for the target pixel. In the display devices  11  and  12  and the display methods according to first and second embodiments, the signal processing units  21  and  22  may calculate gradation data of three or more peripheral pixels, specify the maximum value MAX from the calculation results, and set the maximum value MAX to the correction value CV for the target pixel. 
     The signal processing units  21  and  22  may determine the correction value CV from the top three large values among the calculation results, values equal to or more than a predetermined value among the calculation results, or the sum or average of the calculation results. When the pixel  60   n _ m  is set to the target pixel, the signal processing units  21  and  22  may set one or more of the pixels  60   n− 2_m−1,  60   n− 2_m+1,  60   n −1_m−2,  60   n− 1_m+2,  60   n +1_m−2,  60   n +1_m+2,  60   n +2_m−1, and  60   n +2_m+1, which were not set to the calculation targets in first and second embodiments, to peripheral pixels in order to determine the correction value CV. 
     The display devices  11  to  14  and the display methods according to first to fourth embodiments may calculate the differences between the gradation data of the target pixel and the gradation data of the peripheral pixels by subtracting the gradation data of the target pixel from the gradation data of the peripheral pixels as expressed in Equations (1) to (4). However, the display devices  11  to  14  and the display methods according to first to fourth embodiments may calculate the differences between the gradation data of the target pixel and the gradation data of the peripheral pixels by subtracting the gradation data of the peripheral pixels from the gradation data of the target pixel, specify the maximum value from the calculation results, and set the maximum value to the correction value CV for the target pixel. 
     Specifically, in the display device  11  and the display method according to a first embodiment, the signal processing unit  21  calculates a difference between the gradation data of the target pixel and the gradation data of two peripheral pixels disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, based on Equation (5). Then, the signal processing unit  21  specifies the maximum value from the calculation results, and sets the maximum value to the correction value CV for the target pixel. 
     
       
         
           
             
               
                 
                   
                     
                       CV 
                       — 
                     
                     ⁢ 
                     
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                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
     For example, when the pixel  60   n _ m  of the m-th column at the n-th row is set to the target pixel, the signal processing unit  21  calculates the difference between the gradation data of the target pixel and the gradation data of two peripheral pixels disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the pixel  60   n _ m  set to the target pixel, based on Equation (5). The signal processing unit  21  specifies the maximum value MAX from the calculation results, and sets the maximum value MAX to a correction value CV_n_m for the pixel  60   n  m. 
     The signal processing unit  21  determines the correction value CV corresponding to the target pixel, based on a difference between the gradation data of the target pixel and the gradation data of a first peripheral pixel adjacent to the target pixel and a second peripheral pixel adjacent to the first peripheral pixel, among the plurality of pixels  60 . The signal processing unit  21  decreases the pixel value of the target pixel by subtracting the correction value CV from the gradation data of the target pixel, thereby decreasing the difference. The pixel value is a gradation value, for example. 
     That is, the signal processing unit  21  determines the correction value CV corresponding to the target pixel based on the difference between the gradation data of the target pixel and the gradation data of the two peripheral pixels disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, among the plurality of pixels  60 . Then, the signal processing unit  21  reduces the pixel value of the target pixel by subtracting the correction value CV from the gradation data of the target pixel, thereby decreasing the difference. 
     In the display device  12  and the display method according to a second embodiment, the signal processing unit  22  calculates the difference between the gradation data of the target pixel and the gradation data of two peripheral pixels disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, based on Equation (6). Then, the signal processing unit  22  specifies the maximum value from the calculation results, and sets the maximum value to the correction value CV for the target pixel. 
     
       
         
           
             
               
                 
                   
                     
                       CV 
                       — 
                     
                     ⁢ 
                     
                       n 
                       — 
                     
                     ⁢ 
                     m 
                   
                   = 
                   
                     MAX 
                     ⁡ 
                     
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                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   6 
                   ) 
                 
               
             
           
         
       
     
     For example, when the pixel  60   n _ m  of the m-th column at the n-th row is set to the target pixel, the signal processing unit  22  calculates a difference between the gradation data of the pixel  60   n _ m  and the gradation data of two peripheral pixels disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the pixel  60   n _ m  set to the target pixel, based on Equation (6). The signal processing unit  22  specifies the maximum value MAX from the calculation results, and sets the maximum value MAX to a correction value CV_n_m for the pixel  60   n _ m.    
     The signal processing unit  22  determines the correction value CV corresponding to the target pixel, based on a difference between the gradation data of the target pixel and the gradation data of a first peripheral pixel adjacent to the target pixel and a second peripheral pixel adjacent to the first peripheral pixel, among the plurality of pixels  60 . The signal processing unit  22  reduces the pixel value of the target pixel by subtracting the correction value CV from the gradation data of the target pixel, thereby decreasing the difference. The pixel value is a gradation value, for example. 
     That is, the signal processing unit  21  determines the correction value CV corresponding to the target pixel based on the difference between the gradation data of the target pixel and the gradation data of the two peripheral pixels disposed in each of the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, among the plurality of pixels  60 . Then, the signal processing unit  21  reduces the pixel value of the target pixel by subtracting the correction value CV from the gradation data of the target pixel, thereby decreasing the difference. 
     In the display device  13  and the display method according to a third embodiment, the signal processing unit  23  calculates the differences between the gradation data of the target pixel and the gradation data of the peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, based on Equation (7). Then, the signal processing unit  23  specifies the maximum value from the calculation results, and sets the maximum value to the correction value CV for the target pixel. 
     
       
         
           
             
               
                 
                   
                     
                       CV 
                       — 
                     
                     ⁢ 
                     
                       n 
                       — 
                     
                     ⁢ 
                     m 
                   
                   = 
                   
                     MAX 
                     ⁡ 
                     
                       ( 
                       
                         
                           
                             
                               
                                 
                                   α 
                                   ⁢ 
                                   
                                       
                                   
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                                   11 
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                                 17 
                                 × 
                                 
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                               18 
                               × 
                               
                                 ( 
                                 
                                   
                                     
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                                 ) 
                               
                             
                           
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   7 
                   ) 
                 
               
             
           
         
       
     
     For example, when the pixel  60   n _ m  of the m-th column at the n-th row is set to the target pixel, the signal processing unit  23  calculates the differences between the gradation data of the pixel  60   n _ m  and the gradation data of the peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the pixel  60   n _ m  set to the target pixel, based on Equation (7). The signal processing unit  23  specifies the maximum value MAX from the calculation results, and sets the maximum value MAX to the correction value CV_n_m for the pixel  60   n _ m.    
     The signal processing unit  23  determines the correction value CV corresponding to the target pixel based on the differences between the gradation data of the target pixel and the gradation data of the peripheral pixels adjacent to the target pixel, among the plurality of pixels  60 . The signal processing unit  23  reduces the pixel value of the target pixel by subtracting the correction value CV from the gradation data of the target pixel, thereby decreasing the differences. The pixel value is a gradation value, for example. 
     That is, the signal processing unit  23  determines the correction value CV corresponding to the target pixel based on the differences between the gradation data of the target pixel and the gradation data of the peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, among the plurality of pixels  60 . Then, the signal processing unit  23  reduces the pixel value of the target pixel by subtracting the correction value CV from the gradation data of the target pixel, thereby decreasing the differences. 
     In the display device  14  and the display device according to a fourth embodiment, the signal processing unit  24  calculates the gradation data of the peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, based on Equation (8). Then, the signal processing unit  24  specifies the maximum value from the calculation results, and sets the maximum value to the correction value CV for the target pixel. 
     
       
         
           
             
               
                 
                   
                     
                       CV 
                       — 
                     
                     ⁢ 
                     
                       n 
                       — 
                     
                     ⁢ 
                     m 
                   
                   = 
                   
                     MAX 
                     ⁡ 
                     
                       ( 
                       
                         
                           
                             
                               
                                 
                                   α 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   21 
                                   × 
                                   
                                     ( 
                                     
                                       
                                         
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                                           — 
                                         
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                                   × 
                                   
                                     ( 
                                     
                                       
                                         
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                                 α 
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                                 ⁢ 
                                 25 
                                 × 
                                 
                                   ( 
                                   
                                     
                                       
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                                         — 
                                       
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                                         n 
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                                     + 
                                     1 
                                   
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                               , 
                             
                           
                         
                         
                           
                             
                               
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                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 26 
                                 × 
                                 
                                   ( 
                                   
                                     
                                       
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                                         — 
                                       
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                                     + 
                                     
                                       
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                                         — 
                                       
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                                     + 
                                     1 
                                   
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                               , 
                             
                           
                         
                         
                           
                             
                               
                                 α 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 27 
                                 × 
                                 
                                   ( 
                                   
                                     
                                       
                                         gr 
                                         — 
                                       
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                                         n 
                                         — 
                                       
                                       ⁢ 
                                       m 
                                     
                                     - 
                                     
                                       
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                                         — 
                                       
                                       ⁢ 
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                                     + 
                                     
                                       
                                         1 
                                         — 
                                       
                                       ⁢ 
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                                     - 
                                     1 
                                   
                                   ) 
                                 
                               
                               , 
                             
                           
                         
                         
                           
                             
                               α 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               28 
                               × 
                               
                                 ( 
                                 
                                   
                                     
                                       gr 
                                       — 
                                     
                                     ⁢ 
                                     
                                       n 
                                       — 
                                     
                                     ⁢ 
                                     m 
                                   
                                   - 
                                   
                                     
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                                       — 
                                     
                                     ⁢ 
                                     n 
                                   
                                   - 
                                   
                                     
                                       1 
                                       — 
                                     
                                     ⁢ 
                                     m 
                                   
                                   - 
                                   1 
                                 
                                 ) 
                               
                             
                           
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   8 
                   ) 
                 
               
             
           
         
       
     
     For example, when the pixel  60   n _ m  of the m-th column at the n-th row is set to the target pixel, the signal processing unit  24  calculates the differences between the gradation data of the pixel  60   n _ m  and the gradation data of the peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the pixel  60   n _ m  set to the target pixel, respectively, based on Equation (8). The signal processing unit  24  specifies the maximum value MAX from the calculation results, and sets the maximum value MAX to the correction value CV_n_m for the pixel  60   n _ m.    
     The signal processing unit  24  determines the correction value CV corresponding to the target pixel based on the differences between the gradation data of the target pixel and the gradation data of the peripheral pixels adjacent to the target pixel, among the plurality of pixels  60 . The signal processing unit  24  reduces the pixel value of the target pixel by subtracting the correction value CV from the gradation data of the target pixel, thereby decreasing the differences. The pixel value is a gradation value, for example. 
     That is, the signal processing unit  24  determines the correction value CV corresponding to the target pixel based on the differences between the gradation data of the target pixel and the gradation data of the peripheral pixels disposed in the horizontal direction, the vertical direction, and the oblique direction with respect to the target pixel, respectively, among the plurality of pixels  60 . Then, the signal processing unit  24  reduces the pixel value of the target pixel by subtracting the correction value CV from the gradation data of the target pixel, thereby decreasing the differences. 
     In the display devices  11  to  14  and the display methods according to first to fourth embodiments, the analog driving method has been exemplified. However, a digital driving method based on a sub-frame scheme may be applied.