Patent ID: 9293096
Filing Date: 2016-03-22
CPC Classification: G09G

Claim Text:
1. An image display device comprising: a display panel having a plurality of pixels, each pixel comprising three basic color subpixels to display three primary colors for obtaining white display by additive mixture of colors and one white subpixel to display a white color; a four color gray level signal generating unit, to generate four color gray level signals corresponding to said three basic color subpixels and one white subpixel from an inputted three color gray level signal corresponding to three primary colors; and a driving unit to supply a corresponding subpixel gray level signal to each of said three basic color subpixels and one white subpixel when said four color gray level signals are inputted from said four color gray level signal generating unit, wherein said four color gray level signal generating unit comprises: a gamma converting unit to perform gamma conversion on said three color gray level signal to convert three color gray level values into three color luminance values; a maximum and minimum luminance value calculating unit to calculate a maximum luminance value and minimum luminance value from among said three color luminance values inputted from the gamma converting unit; a first four color luminance value calculating unit to calculate first four color luminance values consisting essentially of first three color luminance values corresponding to said three basic color subpixels and a first white color luminance value corresponding to said one white subpixel, wherein said first three color luminance values are calculated based on a full white ratio set in advance, the inputted three color luminance values and said minimum luminance value, the full white ratio being defined as a ratio of one full white display luminance produced by only said white subpixel to another full white display luminance produced by said three basic color subpixels, whereas said first white color luminance value is calculated based on said minimum luminance value; a correction coefficient calculating unit to calculate a correction coefficient being used to correct the first four color luminance values each to make the value be a specified upper limit or less based on a maximum value of said first four color luminance values and said maximum luminance value; a second four color luminance value calculating unit to calculate second four color luminance values based on said first four color luminance values and said correction coefficient, the second four color luminance values consisting essentially of second three color luminance values and a second white color luminance value; and a reverse gamma converting unit to perform reverse gamma conversion on said second four color luminance values to generate said four color gray level signals, wherein said correction coefficient calculating unit is configured, when said maximum luminance value is greater than 0, to calculate said correction coefficient by dividing said maximum value of said first four color luminance values by said maximum luminance value and, when said maximum luminance value is 0, to set said correction coefficient as 1, and wherein said first four color luminance value calculating unit calculates said first four color luminance values according to the following Equations: where L=full white ratio, M