Liquid crystal display device and backlight control method

摘要

In a liquid crystal device, an in-region gradation value detection section detects gradation levels of input video signals on every sub-region, removing gradation levels of pixels within a predetermined upper range (m%) from the brightest gradation level in the sub-region to detect the maximum in-region gradation level Pa. A boundary gradation value detecting section removes gradation levels for pixels within a predetermined upper range (n%) from the brightest gradation level for pixel groups belonging to the region boundary portion in the sub-region to detect the maximum boundary gradation level Pb. A backlight control value deciding section selects higher one of the level Pa and the level Pb as the maximum gradation level Pc in the sub-region, and decides a backlight control value K based on the ratio between the level Pc and the upper limit value Pmax of the gradation level.