Two liquid crystal on silicon panel projector with efficient light-emitting diode illumination engine

Abstract

LED-based projectors have numerous advantages compared to traditionalprojectors. They are more compact, they exhibit a larger color gamut anda longer lifetime, the supply voltage is lower and they can even operateon batteries. LEDs can switch rapidly (possibility to pulse) and theyhave a high dimming ratio (contrast considerations). However, they havelow optical power per etendue, although this is also improvingconsistently. With an efficient illumination engine design we can buildan LED projector with a moderate light output and with superiorproperties. We present a relatively compact LED projector with twoliquid crystal on silicon (LCOS) light valves (LVs). One of these LVsalternately modulates red and blue information, while the otherpermanently modulates green information to achieve a good color balance.Additionally, we apply some methods to increase the brightness on thescreen. Our two-LCOS approach results in a compact, efficient LEDprojector that produces 171 Im projected D65 flux. (c) 2007 Society ofPhoto-Optical Instrumentation Engineers.