Bilinear weighting and threshold scheme for low-power two-dimensional local dimming liquid crystal displays without block artifacts

Abstract. A two-dimensional (2-D) weighted roll-off local dimming algorithm that eliminates any visible block artifacts caused by the spatial mismatch between a discontinuous panel image and a continuous backlight is described. The proposed scheme enhances the high gray details by means of a roll-off scheme and removes the block artifacts with bilinear weighting of a pixel-compensated panel image. In addition, the threshold scheme is used to resolve overcompensation problems that lead to visible artifacts around the boundaries of dark local blocks. The image quality and the power consumption are evaluated for 40 test images through both simulation and measurement. Compared to 15.56 and 1.45 of a 2-D roll-off method, the maximum and average color difference values of a proposed scheme are reduced to 7.76 and 0.72 in the simulation. For a prototype 40-in. light emitting diode TV, the average power saving over 40 test images is measured as 60.96%.