Patent ID: 8373644

Claim:
A backlight luminance control apparatus comprising: a luminance control unit for individually controlling luminance in each of a plurality of areas constituting a planar backlight, which illuminates a video display panel for displaying a video image based on a video signal, according to gradation values of the video image displayed in an area of said video display panel illuminated by each area; a frequency distribution obtaining unit for obtaining a frequency distribution of gradation values of pixels constituting a video image, based on a video signal; a dark pixel amount calculating unit for calculating, from the frequency distribution obtained by said frequency distribution obtaining unit a dark pixel amount indicating an amount of pixels whose gradation values are equal to or less than a predetermined first reference value; a lower limit calculating unit for calculating a lower limit of luminance in the areas to a value which decreases monotonously according to the dark pixel amount; an adjusting unit for adjusting the luminance in an area where the luminance according to the gradation values of the video image is less than the lower limit among a plurality of areas of said backlight to the lower limit; an average calculating unit for calculating an average value of the gradation values from the frequency distribution; and a unit for correcting the lower limit by multiplying the lower limit calculated by said lower limit calculating unit by a coefficient which increases monotonously according to the average value calculated by said average calculating unit.