Weighted roll-off scheme to remove block artifacts for low power local dimming liquid crystal displays

• Novel roll-off algorithms are introduced for ideal and real local dimming backlights.
• Block artifact reduction scheme is evaluated by simulation and measurement.
• A new weighted roll-off algorithm achieves better image quality at the same power consumption.

A roll-off algorithm has been incorporated into adaptive dimming LCDs to enhance the details of high gray levels. However, because a roll-off algorithm generates block artifacts in local dimming LCDs with 1-D or 2-D local blocks, we introduced a new roll-off algorithm for block artifact reduction in 2011 based on an ideal backlight without any light spreads. Whereas, this paper demonstrates a weighted roll-off local dimming scheme for low power LCD applications which eliminates block artifacts at a real backlight with light spreads. Both simulation and experimental results represent that a proposed weighted algorithm alleviates color difference values as well as block artifacts without any increases in power consumption. The measured backlight power consumption in a weighted roll-off 1-D dimming LCD of 5 local blocks is 27.60 W over 24 test images, on the average, compared to 62.45 W of a constant backlight.