  In this paper, a method is proposed for finding a pixel transformation
function that maximizes backlight dimming while maintaining a pre-specified
image distortion level for a liquid crystal display. This is achieved by
finding a pixel transformation function, which maps the original image
histogram to a new histogram with lower dynamic range. Next the contrast of the
transformed image is enhanced so as to compensate for brightness loss that
would arise from backlight dimming. The proposed approach relies on an accurate
definition of the image distortion which takes into account both the pixel
value differences and a model of the human visual system and is amenable to
highly efficient hardware realization. Experimental results show that the
histogram equalization for backlight scaling method results in about 45% power
saving with an effective distortion rate of 5% and 65% power saving for a 20%
distortion rate. This is significantly higher power savings compared to
previously reported backlight dimming approaches.
