Power savings and enhancement of gray‐scale capability of LCD TVs with an adaptive dimming technique

Abstract

The luminance of a backlight unit for an LCD TV is adaptively and locally dimmed along with the input video signal in order to reduce the power consumption and also to improve the picture quality. By adopting the zero-dimensional (0D), 1D, and 2D adaptive dimming techniques, a sample movie having 8.0% post-gamma average picture levels (APL) could be displayed using 83%, 71%, and 50% of the original backlight power, respectively. For an adoption of the 2D dimming, an LED backlight is preferable. The adaptive-dimming technique also allows the differential aging characteristics between the LED components and temperature dependence of color and luminance to be overcome. From simulations of a reduction in power consumption, it was found that 40 × 40 pixels is a unit of the local dimming, 30 frames for the sampling period, 24 dimming steps, and an equalsignal-step method for determining the dimming factor have been found to be appropriate. The grayscale capability of low-luminance images can also be improved by dimming the backlight luminance and expanding the input signal. By using an LCD TV having an 8-bit capability, an 11-bit-equivalent gray-scale expression was experimentally proven.

A laser current control algorithm to avoid color distortion in laser projection displays

“…A fixed working current is needed to achieve stable primary light ratio and image quality performance. One of the important advantages of solid‐state light sources, such as laser and LED, compared with traditional gaseous light sources is that their luminous can be adjusted in real time, so that ultra‐high dynamic contrast and energy saving can be achieved . However, when dynamically dimming the display light source, problems such as brightness saturation and color shift are often encountered.…”

Cooperative local dimming for accurate backlight brightness matching

“…The leakage of light occurs as the liquid crystal cannot block all of the light coming from the backlight. The work in [2] suggested two-dimensional adaptive dimming that improves dynamic contrast in such a circumstance. Yeo et al [3] proposed an algorithm for local dimming that boosts luminance for bright (highluminance) areas in a dark picture to compensate for the lack of light in those areas.…”

“…Simulation results: The performance of the proposed CLD method is compared with that of the conventional method in [2] that considers only a single segment in performing local dimming. The backlight used in the simulations has 192 segments (16 rows × 12 columns) that are individually dimmed.…”

Low power active dimming liquid crystal display with high resolution backlight

“…These algorithms include a backlight dimming block to calculate the dimmed luminance of a backlight for lowering power consumption and a pixel compensation block to increase the transmittance of a panel for maintaining image quality [1]. The backlight dimming levels are, in general, determined using the middle value between average and maximum grey values of an input image data, which is the tradeoff between low power consumption and high image quality.…”

“…In addition, the roll-off schemes are in use for pixel compensation for better image details in the high grey region [2,3]. To ameliorate the power reduction ratio further without any quality degradation, it is adopted to step up the resolution of a backlight such as 1-D and 2-D dimming schemes [1] despite the increase in system costs. Analysis on block artefacts: The roll-off algorithms integrated with high resolution backlights can cause block artefacts.…”