SBIR-STTR Award

backlights for portable color LCD matrix displays are extremely ineppicient: 96% of the battery power is wasted on the backlight system . A high efficlency backlight system is proposed based on the use of micro-optical imaging of rgb phosphor triads onto the LCD RGB pixel rows so that the 67% loss in the LCD filter system is avoided. In addition a special collimator is proposed that concentrates the emission into the acceptance cone of the LCD display. Use of high efficiency RGB phosphor (95% conversion efficiency) coupled with the collimation optics should result in a 12x increase in efpiclency over existing LCD color backlights. This development could have major impact on commercial portable computer terminals particularly with color displays in which case the time between battery re-charge could be greatly increased or the size and weight of the battery reduced.

There is a need for a low cost, high efficiency backlight for color LCD display to replace the existing inefficient 20 watt backlight. In Phase I study, a new high efficiency color backlight system was investigated utilizing ultra-violet excitation of RGB phosphor color stripes behind RGB modulator rows in the LCD which were coupled with concentrating optics. Experimental results showed a factor of 12x increase in efficiency over the present backlight system. Because of this order of magnitude improved efficiency, a portable, light weight color LCD display would become feasible. The Phase I study wasconcentrated on developing and testing various components required for a power efficient display. Specifically, a high efficiency uv distribution system was designed and tested, and the result showed the efficiency to be 47.5%. The goal of the Phase II is to incorporate the high efficiency features developed in Phase I into an operational color STN-LCD display as a retrofit into the existing functional color portable display. The high contrast backlighted color LCD display will have a total power consumption of less than 2 watts and overall thickness of less than 12mm. Anticipated

Benefits:
the successful development of this high efficiency color backlight will have immediate commercial applications in existing color LCD notebook computers where "windows" software requires full color for efficient use. Similar techniques can be applied to light large area LCD displays for use in HDTV systems. In addition, the system will be useful for color LCD displays for avionic use in which power consumption is a problem.