Patent ID: 8233013
Filing Date: 2012-07-31
Classification: G09G

Abstract:
1. A transmissive-type liquid crystal display device, comprising: a liquid crystal panel having pixels each divided into four subpixels red (R), green (G), blue (B), and white (W); a white-color active backlight by which a luminance of light that is to be emitted is controllable; a color-saturation reducing section that carries out a process of reducing color saturation on pixel data that is high in luminance and in color saturation, among pixel data contained in a first RGB input signal which is an input image, so that the first RGB input signal is converted into a second RGB input signal; an output signal generating section that generates, from the second RGB input signal, a transmissivity signal of each of the subpixels R, G, B, W of each pixel of the liquid crystal panel, and calculates a backlight value in the active backlight; a liquid crystal panel controlling section that controls and drives the liquid crystal panel on the basis of the transmissivity signal generated in the output signal generating section; and a backlight controlling section that controls, on the basis of the backlight value calculated in the output signal generating section, the luminance of light that is to be emitted from the backlight; wherein the color-saturation reducing section extracts, from the pixel data contained in the first RGB input signal which is the input image, pixel that is high in luminance and in color saturation, in accordance with process (A) below, and carries out, in accordance with process (B) below, a process of reducing the color saturation on the pixel data thus extracted: (A) calculating an upper limit MAXw of the backlight by and extracting, as the pixel data that is high in luminance and in color saturation, target pixel data that satisfies where: WR is a white-color luminance ratio (this is a ratio P2/P1 of a display luminance P2 in a case in which a transmissivity of each of the subpixels RGB is 0% and a transmissivity of the subpixel W is x %, with respect to a display luminance P1 in a case in which the transmissivity of each of the subpixels RGB is x % and the transmissivity of the subpixel W is 0%); MAX is the upper limit of the backlight value in a case in which the process of reducing color saturation is not carried out; Bl Ratio is a backlight value determination ratio having a range of 1/(1+WR)≦Bl Ratio≦1.0; Ri, Gi, Bi are RGB values of the target pixel in the first RGB input signal, wherein i is an integer between 1 and Np; Np is the number of pixels in the input image; max (A, B, . . . ) is a maximum value of A, B, . . . ; and min (A, B, . . . ) is a minimum value of A, B, . . . ; and (B) obtaining, on the basis of the pixel data thus extracted,  pixel data after the process of reducing color saturation, where: Rsi, Gsi, Bsi are RGB values of the target pixel in the second RGB input signal after the process of reducing color saturation; Yi is a luminance of the target pixel; and