Patent ID: 8207953

Claim:
A backlight apparatus comprising: an illuminating section that radiates illumination light on a back of an optical modulating section which comprises a plurality of image display areas and which displays an image by modulating per image display area the illumination light according to an image signal; and a brightness determining section that determines a light emission brightness value of the illuminating section and renews a light emitting state of the illuminating section based on the determined light emission brightness value, wherein: the illuminating section comprises a plurality of light emitting areas illuminating the plurality of image display areas, respectively; and the brightness determining section (i) applies a first weight for first information based on an input image signal of a first image display area and a second weight, independent from the first weight, for second information based on an input image signal of a second image display area, (ii) is configured to change the first weight and the second weight independently based on the first information and the second information respectively, and (iii) determines a light emission brightness value of a light emitting area illuminating a first image display area, from values acquired from the weights of the first weight and the second weight, and (iv) changes the weights such that the second weight is (a) increased in an environment where brightness of ambient light is lower than a first threshold and (b) decreased in an environment where the brightness of ambient light is higher than a second threshold that is different from the first threshold.