Patent ID: 8633950

Claim:
An image display device displaying a picture using a picture signal from an external device as an input value and using an output value obtained by correcting or converting the input value by a gamma curve, wherein the input value is a gray level x of the image signal (where x is an integer satisfying 0≦x≦2 n −1; where n is a number of bits), and the output value is a luminance relative value Y(x) standardized so that a luminance is 1 at a maximum gray level x max (=2 n −1); the gray level x and the luminance relative value Y(x) have a relationship determined in a one-on-one manner; and there are at least one or more gray levels x i satisfying: 0< R ( x i ,x i +1)< R ( x i −1 ,x i ) (Equation 3) between a gray level 0 and the maximum gray level x max when defining gradients R(x i −1, x i ) and R(x i , x i +1) according to: R ⁡ ( x i - 1 , x i ) = Y ⁡ ( x i ) - Y ⁡ ( x i - 1 ) x i - ( x i - 1 ) = Y ⁡ ( x i ) - Y ⁡ ( x i - 1 ) ⁢ ⁢ ⁢ and ( Equation ⁢ ⁢ 1 ) R ⁡ ( x i , x i + 1 ) = Y ⁡ ( x i + 1 ) - Y ⁡ ( x i ) ( x i + 1 ) - x i = Y ⁡ ( x i + 1 ) - Y ⁡ ( x i ) ; ( Equation ⁢ ⁢ 2 ) the image display device has a gamma curve adjusted to have one or more gray levels x j satisfying: 0 <R ( x j ,x j −1)< R ( x j +1, x j ) (Equation 6) between the gray level x j and the maximum gray level x max when defining gradients R(x j −1, x j ) and R(x j , x j +1) according to: R ⁡ ( x j - 1 , x j ) = Y ⁡ ( x j ) - Y ⁡ ( x j - 1 ) x j - ( x j - 1 ) = Y ⁡ ( x j ) - Y ⁡ ( x j - 1 ) ( Equation ⁢ ⁢ 4 ) ⁢ and R ⁡ ( x j , x j + 1 ) = Y ⁡ ( x j + 1 ) - Y ⁡ ( x j ) ( x j + 1 ) - x j = Y ⁡ ( x j + 1 ) - Y ⁡ ( x j ) ; ( Equation ⁢ ⁢ 5 ) and a gamma curve obtained by connecting coordinates of points denoted by the gray level x and the luminance relative value Y(x) in a range of 0≦x≦2 n −1 is crossed with a reference gamma curve Y org expressed by: Y org ⁡ ( x ) = ( x 2 n - 1 ) 2.2 ( Equation ⁢ ⁢ 7 ) at least one or more points except for (0, Y org (0)) and (2 n −1, Y org (2 n −1)), wherein the gray level x is an integer, and wherein a point at which the gamma curve and the reference gamma curve Y org cross is taken as a crossover point C p , and a gray level x p of a coordinate of the crossover point C p is positioned between the gray level x i and the gray level x j .