Abstract:
A white balance adjustment method for a display, the method including acquiring spectrum stimulus values of q gray scales of red, green, blue and white of a display panel of a tested display; determining spectrum stimulus value brightness of white and green, and performing interpolation segmenting on brightness of white and green; normalizing brightness of white and green; acquiring an ideal brightness normalized value of white and an ideal brightness normalized value of green; comparing the normalized value for brightness white and the ideal brightness normalized value corresponding to the white and the normalized value for brightness of green and the ideal brightness normalized value corresponding to the green respectively, based on the closest principle, and determining optimal gray scales of white and green; determining a target chromaticity, and changing the gray scales of red and blue, acquiring a RGBW combination which is closest to the target chromaticity.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a display device, more particularly, to a white balance adjustment method for the display device. 
       BACKGROUND OF THE INVENTION 
       [0002]    In a conventional display device, such as a liquid crystal display device, an organic light-emitting diode (OLED) display device etc., all the displayed white field chromaticity coordinates have different levels of errors due to a displaying principle of the display device or a designing error of the display device. 
         [0003]    With regard to the errors of white field chromaticity coordinates in a display device, if a corresponding with balance correction is not performed, color effects displayed among different display devices would have a relatively large difference. So the white balance correction generally needs to be performed in process of manufacturing display devices to make displaying color of each display device uniform. 
         [0004]    The conventional display devices use red (R) sub-pixel, green (G) sub-pixel, blue (B) sub-pixel to display a picture. But in order to increase penetration rate, brightness and energy efficiency and to achieve energy conservation and environment protection, a display device which uses red (R) sub-pixel, green (G) sub-pixel, blue (B) sub-pixel and white (W) sub-pixel to display the picture has already been developed. Here, a white balance adjustment method for a display device based on the three sub-pixels, RGB, cannot be applied to a display device based on the four sub-pixels, RGBW. 
       SUMMARY OF THE INVENTION 
       [0005]    A white balance adjustment method for a display device is provided in order to resolve the above conventional technical problems, which comprising: 1) acquiring RX q , RY q , RZ q  which are spectrum stimulus values of q gray scale of red of a display panel of a tested display device, GX q , GY q , GZ q  which are spectrum stimulus values of q gray scale of green of the display panel of the tested display device, BX q , BY q , BZ q  which are spectrum stimulus values of q gray scale of blue of the display panel of the tested display device, and WX q , WY q , WZ q  which are spectrum stimulus values of q gray scale of white of the display panel of the tested display device, wherein q is a gray level and is an integer, X, Y, Z are spectrum stimulus values of the display panel of the tested display device; 2) determining WY q  which is spectrum stimulus value of q gray scale of white of the display panel of the tested display device as brightness of q gray scale of white; and determining GY q  which is spectrum stimulus value of q gray scale of green of the display panel of the tested display device as brightness of q gray scale of green; 3) dividing WY q  which is brightness of q gray scale of white of the display panel of the tested display device, into i segments between q gray scale and q−1 gray scale by using an interpolation method; and dividing GY q  which is brightness of q gray scale of green of the display panel of the tested display device, into i segments between q gray scale and q−1 gray scale by using the interpolation method, wherein i is an integer that is not less than 2; 4) normalizing values from WY 0  which is brightness of 0 gray scale to brightness of max gray scale WY max  which is brightness of max gray scale, which have been divided, as WN 0  to WN max , on the basis of WY max  which is brightness of max gray scale of white of the display panel of the tested display device and WY 0  which is brightness of 0 gray scale; and normalizing values from GY 0  which is brightness of 0 gray scale to GY max  which is brightness of max gray scale, which have been divided, as GN 0  to GN max , on the basis of GY max  which is brightness of green max gray scale of green of the display panel of the tested display device and GY 0  which is brightness of 0 gray scale, wherein the max gray scale means the maximum gray scale; 5) acquiring WM q  which is an ideal brightness normalized value of q gray scale of white of the display panel of the tested display device; and acquiring GM q  which is an ideal brightness normalized value of q gray scale of green of the display panel of the tested display device; 6) comparing the ideal brightness normalized value WM q  and each of the values from WY 0  which is brightness of 0 gray scale to WY max  which is brightness of max gray scale, which have been divided, determining an optimal gray scale of white of the display panel of the tested display device, which corresponds to q gray scale, based on the closest principle; and comparing the ideal brightness normalized value GM q  and each of the values from GY 0  which is brightness of 0 gray scale to GY max  which is brightness of max gray scale, which have been divided, determining an optimal gray scale of green of the display panel of the tested display device, which corresponds to q gray scale, based on the closest principle; and 7) determining a target chromaticity, changing the red and blue gray scales of the display panel of the tested display device, acquiring different RGBW combinations, measuring chromaticities of the different RGBW combinations, and determining a RGBW combination which is closest to the target chromaticity based on the measured chromaticities of the different RGBW combinations. 
         [0006]    Further, in the step 3), WY q  which is brightness of q gray scale of white of the display panel of the tested display device may be divided between q gray scale and q−1 gray scale into: 
         [0000]    
       
         
           
             
               WY 
               
                 q 
                 - 
                 1 
               
             
             , 
             
               
                 ( 
                 
                   
                     
                       
                         WY 
                         q 
                       
                       - 
                       
                         WY 
                         
                           q 
                           - 
                           1 
                         
                       
                     
                     i 
                   
                   + 
                   
                     WY 
                     
                       q 
                       - 
                       1 
                     
                   
                 
                 ) 
               
               
                 q 
                 - 
                 1 
                 + 
                 
                   ( 
                   
                     1 
                     / 
                     i 
                   
                   ) 
                 
               
             
             , 
             
                 
             
              
             
               
                 ( 
                 
                   
                     2 
                      
                     
                       
                         
                           WY 
                           q 
                         
                         - 
                         
                           WY 
                           
                             q 
                             - 
                             1 
                           
                         
                       
                       i 
                     
                   
                   + 
                   
                     WY 
                     
                       q 
                       - 
                       1 
                     
                   
                 
                 ) 
               
               
                 q 
                 - 
                 1 
                 + 
                 
                   ( 
                   
                     2 
                     / 
                     i 
                   
                   ) 
                 
               
             
             , 
             
               
 
             
              
             
               
                 ( 
                 
                   
                     3 
                      
                     
                       
                         
                           WY 
                           q 
                         
                         - 
                         
                           WY 
                           
                             q 
                             - 
                             1 
                           
                         
                       
                       i 
                     
                   
                   + 
                   
                     WY 
                     
                       q 
                       - 
                       1 
                     
                   
                 
                 ) 
               
               
                 q 
                 - 
                 1 
                 + 
                 
                   ( 
                   
                     3 
                     / 
                     i 
                   
                   ) 
                 
               
             
             , 
             … 
              
             
                 
             
             , 
             
               
                 WY 
                 q 
               
               . 
             
           
         
       
     
         [0007]    Further, in the step 3), GY q  which is brightness of q gray scale of green (G) of the display panel of the tested display device may be divided between q gray scale and q−1 gray scale into: 
         [0000]    
       
         
           
             
               GY 
               
                 q 
                 - 
                 1 
               
             
             , 
             
               
                 ( 
                 
                   
                     
                       
                         GY 
                         q 
                       
                       - 
                       
                         GY 
                         
                           q 
                           - 
                           1 
                         
                       
                     
                     i 
                   
                   + 
                   
                     GY 
                     
                       q 
                       - 
                       1 
                     
                   
                 
                 ) 
               
               
                 q 
                 - 
                 1 
                 + 
                 
                   ( 
                   
                     1 
                     / 
                     i 
                   
                   ) 
                 
               
             
             , 
             
               
 
             
              
             
               
                 ( 
                 
                   
                     2 
                      
                     
                       
                         
                           GY 
                           q 
                         
                         - 
                         
                           GY 
                           
                             q 
                             - 
                             1 
                           
                         
                       
                       i 
                     
                   
                   + 
                   
                     GY 
                     
                       q 
                       - 
                       1 
                     
                   
                 
                 ) 
               
               
                 q 
                 - 
                 1 
                 + 
                 
                   ( 
                   
                     2 
                     / 
                     i 
                   
                   ) 
                 
               
             
             , 
             
               
 
             
              
             
               
                 ( 
                 
                   
                     3 
                      
                     
                       
                         
                           GY 
                           q 
                         
                         - 
                         
                           GY 
                           
                             q 
                             - 
                             1 
                           
                         
                       
                       i 
                     
                   
                   + 
                   
                     GY 
                     
                       q 
                       - 
                       1 
                     
                   
                 
                 ) 
               
               
                 q 
                 - 
                 1 
                 + 
                 
                   ( 
                   
                     3 
                     / 
                     i 
                   
                   ) 
                 
               
             
             , 
             … 
              
             
                 
             
             , 
             
               
                 GY 
                 q 
               
               . 
             
           
         
       
     
         [0008]    Further, in the step 4), the values from WY 0 , brightness of 0 gray scale to WY max , brightness of max gray scale, which have been divided, may be normalized as WN 0  to WN max  on the basis of WY max  which is brightness of max gray scale of white of the display panel of the tested display device and WY 0  which is brightness of 0 gray scale in accordance with the following formula, 
         [0000]        WN   t =( WY   t   −WY   0 )/( WY   max   −WY   0 ), 
         [0009]    wherein the range of the value t is 0˜max and t=(m−1)/i, where m is a positive integer. 
         [0010]    Further, in the step 4), the values from GY 0 , brightness of 0 gray scale to GY max , brightness of max gray scale, which have been divided, may be normalized as GN 0  to GN max  on the basis of GY max  which is brightness of max gray scale of white of the display panel of the tested display device and GY 0  which is brightness of 0 gray scale in accordance with the following formula, 
         [0000]        GN   t =( GY   t   −GY   0 )/( GY   max   −GY   0 ), 
         [0011]    wherein the range of the value t is 0˜max and t=(m−1)/i, where m is a positive integer. 
         [0012]    Further, in the step 5), WM q  which is the ideal brightness normalized value of q gray scale of white of the display panel of the tested display device may be acquired in accordance with the following formula; 
         [0000]        WM   q =( q /max) E , 
         [0013]    wherein E is a gamma value that ranges between 2.0 to 2.4. 
         [0014]    Further, in the step 5), GM q  which is the ideal brightness normalizing value of q gray scale of green of the display panel of the tested display device may be acquired in accordance with the following formula; 
         [0000]        GM   q =( q /max) E , 
         [0015]    wherein E is a gamma value that ranges between 2.0 to 2.4. 
         [0016]    The white balance adjustment method for the display device according to the present invention can make the panel of the display device get a standard gamma value and a chromatic value. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The above and other aspects, features and advantages of embodiments of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings in which: 
           [0018]      FIG. 1  is a flowchart illustrating a white balance adjustment method for a display device according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0019]    The embodiment of the present invention will now be described more fully hereinafter with reference to the accompanying drawings. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to explain the principle and actual application of the present invention, so that those skilled in the art will appreciate various embodiments of the present invention and various modifications adapted to certain expected applications. 
         [0020]      FIG. 1  is a flowchart illustrating a white balance adjustment method for a display device according to an embodiment of the present invention. 
         [0021]    Referring to  FIG. 1 , in step  101 , RX q , RY q , RZ q  which are spectrum stimulus values of q gray scale of red (R) of the display panel of the tested display device, GX q , GY q , GZ q  which are spectrum stimulus values of q gray scale of green (G) of the display panel of the tested display device, BX q , BY q , BZ q  which are spectrum stimulus values of q gray scale of blue (B) of the display panel of the tested display device, and WX q , WY q , WZ q  which are spectrum stimulus values of q gray scale of white (W) of the display panel of the tested display device may be acquired, wherein q is gray level and is an integer, X, Y, Z are spectrum stimulus values of the display panel of the tested display device. 
         [0022]    In step  102 , WY q  which is spectrum stimulus value of q gray scale of white (W) of the display panel of the tested display device may be determined as brightness of q gray scale of white (W); GY q  which is spectrum stimulus value of q gray scale of green (G) of the display panel of the tested display device may be determined as brightness of q gray scale of green (G). 
         [0023]    In step  103 , WY q  which is brightness of q gray scale of white (W) of the display panel of the tested display device, may be divided into i segments between q gray scale and q−1 gray scale by using an interpolation method, that is, dividing WY q  which is brightness of q gray scale of white (W) of the display panel of the tested display device between q gray scale and q−1 gray scale as: 
         [0000]    
       
         
           
             
               WY 
               
                 q 
                 - 
                 1 
               
             
             , 
             
               
                 ( 
                 
                   
                     
                       
                         WY 
                         q 
                       
                       - 
                       
                         WY 
                         
                           q 
                           - 
                           1 
                         
                       
                     
                     i 
                   
                   + 
                   
                     WY 
                     
                       q 
                       - 
                       1 
                     
                   
                 
                 ) 
               
               
                 q 
                 - 
                 1 
                 + 
                 
                   ( 
                   
                     1 
                     / 
                     i 
                   
                   ) 
                 
               
             
             , 
             
               
 
             
              
             
               
                 ( 
                 
                   
                     2 
                      
                     
                       
                         
                           WY 
                           q 
                         
                         - 
                         
                           WY 
                           
                             q 
                             - 
                             1 
                           
                         
                       
                       i 
                     
                   
                   + 
                   
                     WY 
                     
                       q 
                       - 
                       1 
                     
                   
                 
                 ) 
               
               
                 q 
                 - 
                 1 
                 + 
                 
                   ( 
                   
                     2 
                     / 
                     i 
                   
                   ) 
                 
               
             
             , 
             
               
 
             
              
             
               
                 ( 
                 
                   
                     3 
                      
                     
                       
                         
                           WY 
                           q 
                         
                         - 
                         
                           WY 
                           
                             q 
                             - 
                             1 
                           
                         
                       
                       i 
                     
                   
                   + 
                   
                     WY 
                     
                       q 
                       - 
                       1 
                     
                   
                 
                 ) 
               
               
                 q 
                 - 
                 1 
                 + 
                 
                   ( 
                   
                     3 
                     / 
                     i 
                   
                   ) 
                 
               
             
             , 
             … 
              
             
                 
             
             , 
             
               
                 WY 
                 q 
               
               ; 
             
           
         
       
     
         [0000]    GY q  which is brightness of q gray scale of green (G) of the display panel of the tested display device, may be divided into i segments between q gray scale and q−1 gray scale by using the interpolation method, that is, dividing GY q  which is brightness of q gray scale of green (G) of the display panel of the tested display device between q gray scale and q−1 gray scale as: 
         [0000]    
       
         
           
             
               GY 
               
                 q 
                 - 
                 1 
               
             
             , 
             
               
                 ( 
                 
                   
                     
                       
                         GY 
                         q 
                       
                       - 
                       
                         GY 
                         
                           q 
                           - 
                           1 
                         
                       
                     
                     i 
                   
                   + 
                   
                     GY 
                     
                       q 
                       - 
                       1 
                     
                   
                 
                 ) 
               
               
                 q 
                 - 
                 1 
                 + 
                 
                   ( 
                   
                     1 
                     / 
                     i 
                   
                   ) 
                 
               
             
             , 
             
               
 
             
              
             
               
                 ( 
                 
                   
                     2 
                      
                     
                       
                         
                           GY 
                           q 
                         
                         - 
                         
                           GY 
                           
                             q 
                             - 
                             1 
                           
                         
                       
                       i 
                     
                   
                   + 
                   
                     GY 
                     
                       q 
                       - 
                       1 
                     
                   
                 
                 ) 
               
               
                 q 
                 - 
                 1 
                 + 
                 
                   ( 
                   
                     2 
                     / 
                     i 
                   
                   ) 
                 
               
             
             , 
             
               
 
             
              
             
               
                 ( 
                 
                   
                     3 
                      
                     
                       
                         
                           GY 
                           q 
                         
                         - 
                         
                           GY 
                           
                             q 
                             - 
                             1 
                           
                         
                       
                       i 
                     
                   
                   + 
                   
                     GY 
                     
                       q 
                       - 
                       1 
                     
                   
                 
                 ) 
               
               
                 q 
                 - 
                 1 
                 + 
                 
                   ( 
                   
                     3 
                     / 
                     i 
                   
                   ) 
                 
               
             
             , 
             … 
              
             
                 
             
             , 
             
               
                 GY 
                 q 
               
               . 
             
           
         
       
     
         [0024]    In step  104 , on the basis of WY max  which is brightness of max (q=max) gray scale (that is, the maximum gray scale) of white (W) of the display panel of the tested display device and WY 0  which is brightness of 0 (q=0) gray scale (that is, the minimum gray scale), the values from WY 0 , brightness of 0 gray scale to WY max , brightness of max gray scale, which have been divided, may be normalized as WN 0  to WN max  (that is, both of the number of gray scales which have been divided and that of brightness which correspond to its gray scales are i×max); on the basis of GY max  which is brightness of max gray scale (that is, the maximum gray scale) of green (G) of the display panel of the tested display device and GY 0  which is brightness of 0 gray scale, the values from GY 0 , brightness of 0 gray scale to GY max , brightness of max gray scale, which have been divided, may be normalized as GN 0  to GN max  (that is, both of the number of gray scales which have been divided and that of brightness which correspond to its gray scales are i×max). 
         [0025]    In step  105 , WM q  which is the ideal brightness normalized value of q gray scale of white (W) of the display panel of the tested display device may be acquired; GM q  which is the ideal brightness normalized value of q gray scale of green (G) of the display panel of the tested display device may be acquired. 
         [0026]    In step  106 , WM q , the ideal brightness normalized value and each of WN 0  to WN max  may be compared, and the optimal gray scale of white (W) of the display panel of the tested display device, which corresponds to q gray scale, may be determined, based on the closest principle; GM q  and each of GN 0  to GN max  may be compared, and the optimal gray scale of green (G) of the display panel of the tested display device, which corresponds to q gray scale, may be determined, based on the closest principle. 
         [0027]    In step  107 , the target chromaticity is determined, the gray scales of red (R) and blue (B) of the display panel of the tested display device are changed and different RGBW combinations are acquired so as to determine a RGBW combination which is closest to the target chromaticity. 
         [0028]    The following is a detailed description for the above each steps assumes that the number of gray scales is 256 (namely, max=255). 
         [0029]    In step  101 , by using, for example, a color analyzer or a charge coupled device (CCD) and so on, RX q , RY q , RZ q  which are spectrum stimulus values of red (R) q gray scale of the display panel of the tested display device, GX q , GY q , GZ q  which are spectrum stimulus values of green (G) q gray scale of the display panel of the tested display device, BX q , BY q , BZ q  which are spectrum stimulus values of blue (B) q gray scale of the display panel of the tested display device, and WX q , WY q , WZ q  which are spectrum stimulus values of white (W) q gray scale of the display panel of the tested display device, may be acquired, wherein q is gray level and is an integer an range of which is 0 to 255, X, Y, Z are spectrum stimulus values of the display panel of the tested display device. 
         [0030]    In step  102 , WY q  which is spectrum stimulus value of q gray scale of white (W) of the display panel of the tested display device, may be determined as brightness of q gray scale of white (W); GY q  which is spectrum stimulus value of q gray scale of green (G) of the display panel of the tested display device, may be determined as brightness of q gray scale of green (G). 
         [0031]    In step  103 , WY q  which is brightness of q gray scale of white (W) of the display panel of the tested display device, may be divided into i segments between q gray scale and q−1 gray scale by using the interpolation method; GY q  which is brightness of q gray scale of green (G) of the display panel of the tested display device, may be divided into i segments between q gray scale and q−1 gray scale by using the interpolation method. In this embodiment, i may be taken as 8. It should be understood that i may be taken as a random integer that is not less than 2. As such, WY q  which is brightness of q gray scale of white (W) of the display panel of the tested display device between q gray scale and q−1 gray scale, may be divided as: 
         [0000]    
       
         
           
             
               WY 
               
                 q 
                 - 
                 1 
               
             
             , 
             
               
                 ( 
                 
                   
                     
                       
                         WY 
                         q 
                       
                       - 
                       
                         WY 
                         
                           q 
                           - 
                           1 
                         
                       
                     
                     8 
                   
                   + 
                   
                     WY 
                     
                       q 
                       - 
                       1 
                     
                   
                 
                 ) 
               
               
                 q 
                 - 
                 1 
                 + 
                 
                   ( 
                   
                     1 
                     / 
                     8 
                   
                   ) 
                 
               
             
             , 
             
               
 
             
              
             
               
                 ( 
                 
                   
                     2 
                      
                     
                       
                         
                           WY 
                           q 
                         
                         - 
                         
                           WY 
                           
                             q 
                             - 
                             1 
                           
                         
                       
                       8 
                     
                   
                   + 
                   
                     WY 
                     
                       q 
                       - 
                       1 
                     
                   
                 
                 ) 
               
               
                 q 
                 - 
                 1 
                 + 
                 
                   ( 
                   
                     2 
                     / 
                     8 
                   
                   ) 
                 
               
             
             , 
             
               
 
             
              
             
               
                 ( 
                 
                   
                     3 
                      
                     
                       
                         
                           WY 
                           q 
                         
                         - 
                         
                           WY 
                           
                             q 
                             - 
                             1 
                           
                         
                       
                       8 
                     
                   
                   + 
                   
                     WY 
                     
                       q 
                       - 
                       1 
                     
                   
                 
                 ) 
               
               
                 q 
                 - 
                 1 
                 + 
                 
                   ( 
                   
                     3 
                     / 
                     8 
                   
                   ) 
                 
               
             
             , 
             … 
              
             
                 
             
             , 
             
               
                 WY 
                 q 
               
               . 
             
           
         
       
     
         [0000]    GY q  which is brightness of q gray scale of green (G) of the display panel of the tested display device between q gray scale and q−1 gray scale, may be divided as: 
         [0000]    
       
         
           
             
               GY 
               
                 q 
                 - 
                 1 
               
             
             , 
             
               
                 ( 
                 
                   
                     
                       
                         GY 
                         q 
                       
                       - 
                       
                         GY 
                         
                           q 
                           - 
                           1 
                         
                       
                     
                     8 
                   
                   + 
                   
                     GY 
                     
                       q 
                       - 
                       1 
                     
                   
                 
                 ) 
               
               
                 q 
                 - 
                 1 
                 + 
                 
                   ( 
                   
                     1 
                     / 
                     8 
                   
                   ) 
                 
               
             
             , 
             
               
 
             
              
             
               
                 ( 
                 
                   
                     2 
                      
                     
                       
                         
                           GY 
                           q 
                         
                         - 
                         
                           GY 
                           
                             q 
                             - 
                             1 
                           
                         
                       
                       8 
                     
                   
                   + 
                   
                     GY 
                     
                       q 
                       - 
                       1 
                     
                   
                 
                 ) 
               
               
                 q 
                 - 
                 1 
                 + 
                 
                   ( 
                   
                     2 
                     / 
                     8 
                   
                   ) 
                 
               
             
             , 
             
               
 
             
              
             
               
                 ( 
                 
                   
                     3 
                      
                     
                       
                         
                           GY 
                           q 
                         
                         - 
                         
                           GY 
                           
                             q 
                             - 
                             1 
                           
                         
                       
                       8 
                     
                   
                   + 
                   
                     GY 
                     
                       q 
                       - 
                       1 
                     
                   
                 
                 ) 
               
               
                 q 
                 - 
                 1 
                 + 
                 
                   ( 
                   
                     3 
                     / 
                     8 
                   
                   ) 
                 
               
             
             , 
             … 
              
             
                 
             
             , 
             
               
                 GY 
                 q 
               
               . 
             
           
         
       
     
         [0032]    In step  104 , in accordance with the following formula (1), on the basis of WY 255  which is brightness of 255 (q=255) gray scale (that is, the maximum gray scale) of white (W) of the display panel of the tested display device and WY 0  which is brightness of 0 (q=0) gray scale (that is, the minimum gray scale), the values from WY 0 , brightness of 0 gray scale to WY 255 , brightness of 255 gray scale, which have been divided, may be normalized as WN 0  to WN 255  (that is, both of the number of gray scales which have been divided and that of brightness which correspond to its gray scales are 2041), 
         [0000]        WN   t =( WY   t   −WY   0 )/( WY   255   −WY   0 )  (1).
 
         [0033]    Here, the range of the value t is 0˜255 and t=(m−1)/8, where m is a positive integer. 
         [0034]    In accordance with the following formula (2), on the basis of GY 255  which is brightness of 255 (q=255) gray scale (that is, the maximum gray scale) of green (G) of the display panel of the tested display device and GY 0  which is brightness of 0 (q=0) gray scale, the values from GY 0 , brightness of 0 gray scale to GY 255 , brightness of 255 gray scale, which have been divided, may be normalized as GN 0  to GN 255  (that is, both of the numbers of gray scales which have been divided and that of brightness which correspond to its gray scales are 2041), 
         [0000]        GN   t =( GY   t   −GY   0 )/( GY   255   −GY   0 )  (2).
 
         [0035]    Here, the range of the value t is 0˜255 and t=(m−1)/8, where m is a positive integer. 
         [0036]    In step  105 , in accordance with the following formula (3), WM q  which is the ideal brightness normalized value of q gray scale of white (W) of the display panel of the tested display device, may be acquired, 
         [0000]        WM   q =( q/ 255) E   (3).
 
         [0037]    Here, q is an integer and the range of the value q is 0˜255. E is a gamma value, generally ranging between 2.0 to 2.4, and it is preferably 2.2. 
         [0038]    In accordance with the following formula (4), GM q  which is the ideal brightness normalized value of q gray scale of green (G) of the display panel of the tested display device, may be acquired, 
         [0000]        GM   q =( q/ 255) E   (4).
 
         [0039]    Here, q is integer and the range of the value q is 0˜255. E is a gamma value, generally ranging between 2.0 to 2.4, and it has preferably 2.2. 
         [0040]    In step  106 , the ideal brightness normalized value WM 0  to the ideal brightness normalized value WM 255  and each of the values from WY 0 , brightness of 0 gray scale to WY 255 , brightness of 255 gray scale, which have been divided, may be compared, and the optimal gray scale of white (W) of the display panel of the tested display device, may be determined, based on the closest principle. For example, the differences between each value of WN 0  to WN 255  and WM q  may be acquired and the t gray scale corresponding to the minimum absolute value of the difference WN t  may be determined as the optimal gray scale of white (W) of the display panel of the tested display device, which corresponds to q gray scale. For instance, the difference between WN 111.625  and WM 112  is minimum, namely, 111.625 gray scale is determined as the optimal gray scale of white (W) of the display panel of the tested display device, which corresponds to 112 gray scale. 
         [0041]    The ideal brightness normalized value GM 0  to the ideal brightness normalized value GM 255  and each of the values from GY 0 , brightness of 0 gray scale to GY 255 , brightness of 255 gray scale, which have been divided, may be compared, and the optimal gray scale of green (G) of the display panel of the tested display device, may be determined, based on the closest principle. For example, the differences between each value of GN 0  to GN 255  and GM q  may be acquired and the t gray scale corresponding to the minimum absolute value of the difference GN t  may be determined as the optimal gray scale of green (G) of the display panel of the tested display device, which corresponds to q gray scale. For instance, the difference between GN 211.625  and WM 212  is minimum, namely, 211.625 gray scale is determined as the optimal gray scale of green (G) of the display panel of the tested display device, which corresponds to 212 gray scale. 
         [0042]    In step  107 , the target chromaticity (for instance: x=0.28, y=0.29) may be determined, the gray scales of red (R) and blue (B) of the display panel of the tested display device may be changed, different RGBW combinations may be acquired, and the chromaticities of the different RGBW combinations may be obtained by a measurement. Then the RGBW combination which is closest to the target chromaticity can be determined according to the measured chromaticities of the different RGBW combinations. 
         [0043]    While the present invention has been shown and described with reference to the specific embodiment, those skilled in the art will appreciate that various changes in form and details can be made therein without departing from the spirit and scope of the present invention as defined by the appended claims and their equivalents.