Patent ID: 8421740
Filing Date: 2013-04-16
Classification: G09G

Abstract:
1. A liquid crystal display device, comprising: a liquid crystal panel configured to display an image from image signals; a backlight device disposed on the back side of the liquid crystal panel, and divided into a plurality of regions, the backlight device comprising light sources in each of the regions, wherein the light sources are positioned to emit light onto the liquid crystal panel; a histogram detector configured to detect an image signal gradation distribution for each region and to produce a histogram therefrom; an image gain calculator configured to calculate a gain from the detected gradation distribution of the histogram detector, and to control light emission from each light source in each region of the backlight device, and a light emission luminance calculator configured to control the light emission luminance of each light source based on a maximum luminance of the light sources and based on an inverse number of the gain calculated in the image gain calculator further comprising a maximum gradation detector configured to detect a first maximum gradation of the image signal displayed on each of the backlight device regions within one frame period, at predetermined intervals, wherein the histogram detector detects at least one of a plurality of pixel ratios from the histogram of the image signal gradation distribution, the plurality of pixel ratios includes a pixel ratio lower than a first predetermined gradation and a pixel ratio higher than a second predetermined gradation and wherein pixel ratio is calculated by dividing numbers of pixels that have a certain gradation in one region by total numbers of pixels in that region, and wherein the image gain calculator determines if a value of pixel ratio lower than the first predetermined gradation is more than or equal to a first threshold value, when the value of pixel ratio lower than the first predetermined gradation is more than or equal to the first threshold value, the gain is set to a predetermined value based on the value of pixel ratio lower than the first predetermined gradation, and when the value of pixel ratio lower than the first predetermined gradation is less than the first threshold value, the gain is set to a value calculated by dividing a second maximum gradation of the image signal graduation distribution by the first maximum gradation, wherein the second maximum gradation is determined by the number of bits of the image signal.