Patent ID: 8194094

Claim:
An image display apparatus comprising: (A) an image display panel having a two-dimensional matrix with (P×Q) pixels each including a first sub-pixel for displaying a first elementary color, a second sub-pixel for displaying a second elementary color, a third sub-pixel for displaying a third elementary color and a fourth sub-pixel for displaying a fourth color; and (B) a signal processing section configured to receive a first sub-pixel input signal provided with a signal value of x 1-(p, q) , a second sub-pixel input signal provided with a signal value of x 2-(p, q) and a third sub-pixel input signal provided with a signal value of x 3-(p, q) , and to output a first sub-pixel output signal provided with a signal value of X 1-(p, q) and used for determining the display gradation of said first sub-pixel, a second sub-pixel output signal provided with a signal value of X 2-(p, q) and used for determining the display gradation of said second sub-pixel, a third sub-pixel output signal provided with a signal value of X 3-(p, q) and used for determining the display gradation of said third sub-pixel as well as a fourth sub-pixel output signal provided with a signal value of X 4-(p, q) and used for determining the display gradation of said fourth sub-pixel with regard to a (p, q)th pixel where notations p and q are integers satisfying equations 1≦p≦P and 1≦q≦Q, wherein a maximum lightness value V max (S) expressed as a function of variable saturation S in an HSV color space enlarged by adding said fourth color is stored in said signal processing section, and said signal processing section carries out the following processes of (B-1) finding said saturation S and said lightness value V(S) for each of a plurality of pixels on the basis of the signal values of sub-pixel input signals in said pixels, (B-2) finding an extension coefficient α 0 on the basis of at least one of ratios V max (S)/V(S) found in said pixels, (B-3) finding said output signal value X 4-(p, q) in said (p, q)th pixel on the basis of at least said input signal values x 1-(p, q) , x 2-(p, q) and x 3-(p, q) , and (B-4) finding said output signal value X 1-(p, q) in said (p, q)th pixel on the basis of said input signal value x 1-(p, q) said extension coefficient α 0 and said output signal value X 4-(p, q) , finding said output signal value X 2-(p, q) in said (p, q)th pixel on the basis of said input signal value x 2-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) and finding said output signal value X 3-(p, q) in said (p, q)th pixel on the basis of said input signal value x 3-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) .