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

Abstract

LED-based projectors have numerous advantages compared to traditional projectors. They are more compact, they exhibit a larger color gamut and a longer lifetime, the supply voltage is lower and they can even operate on batteries. LEDs can switch rapidly ͑possibility to pulse͒ and they have a high dimming ratio ͑contrast considerations͒. However, they have low optical power per étendue, although this is also improving consistently. With an efficient illumination engine design we can build an LED projector with a moderate light output and with superior properties. We present a relatively compact LED projector with two liquid crystal on silicon ͑LCOS͒ light valves ͑LVs͒. One of these LVs alternately modulates red and blue information, while the other permanently modulates green information to achieve a good color balance. Additionally, we apply some methods to increase the brightness on the screen. Our two-LCOS approach results in a compact, efficient LED projector that produces 171 lm projected D65 flux.