Optical feedback system with integrated color sensor on LCD

TFT LCDs have the largest market share of all digital flat panel displays. A three color RGB LED LCD backlighting system is very attractive considering wide color gamut, tunable white point, high dimming ratio, long lifetime and environmental compatibility. But the high intensity LED has thermal and time-based dependencies. Color and white luminance levels are not stable over a wide range of temperature due to inherent long-term aging characteristics. In order to minimize color point and brightness differences over time, optical feedback control is a key technology for any LED backlighting system. In this paper, we present the feasibility of an optical color sensing feedback system for an LED backlight by integrating the amorphous silicon color sensor onto the LCD panel. To improve the photoconductivity degradation of amorphous silicon, a new LASER immersion treatment has been applied. The integrated color sensor optical feedback controlled LED backlighting system improved the color variation to less than 0.008 Δu′v′ (CIE1976) compared with 0.025 for an open loop system over the temperature range of 42–76 °C.