Local Dimming Algorithm For LED Edge-type Backlights In LCDs

With wide applications in TV, mobile devices, surveillance, airborne and aviation equipment, liquid crystal displays (LCDs) occupy the dominant position of flat-panel display devices. But LCDs can’t emit lights itself, backlight modules are necessary. In traditional LCDs, the backlight modules usually work under the condition of emitting max luminance, which may cause power waste and lower contrast ratio. To solve the shortcomings of low energy efficiency and contrast of traditional LCDs, researchers begin to study the dynamic dimming technology, which the backlight luminance can dynamically changed with display contents. The dynamic dimming technology can improve display effect by reducing backlight luminance and light leakage. According to backlight module and display module in LCDs, the dynamic dimming algorithm consists of two parts:backlight level dimming and pixel compensation algorithm. However, most of nowadays dynamic dimming algorithms can’t balance the lower power consumption and high display effect.To solve the complex calculation, low power-saving and high overflow distortion rate of exist edge-type dimming algorithm, this paper proposes a dynamic dimming algorithm of high power-saving and low overflow rate. Firstly, it converts the original objective image luminance to subjective perception luminance of human eyes based on human visual characteristics. The LED dimming and pixels level are calculated by this, which could greatly improve power-saving ratio and dimming effect. Secondly, a backlight allocation model based on optimization theory is built for four-side backlight module. It can further enhance power-saving ratio by satisfying backlight requirements with lowest LED luminance. The theoretical feasibility of algorithm is verified by software simulation. The prototype is developed and experimental tests are carried out. Both the simulation results and practical test results show that the proposed edge-type local dimming algorithm can improve energy efficiency and maintain dimming effect effectively.