Two LCOS full color projector with efficient LED illumination engine

LED-based projectors have numerous advantages compared to traditional projectors, but their light output is limited by the limited brightness of the LEDs. With an efficient illumination engine design we can build an LED projector with a moderate light output and with superior properties. In this paper we present a compact LED projector with two 'Liquid Crystal On Silicon' panels and four LEDs (R, 2 x G, B). We use two panels instead of the classical three panels and will still have the same performance and moreover a reduced volume and cost. The illumination system consists of a custom made monolithic component (GTLP) that is combining many functions. We have also integrated some methods to increase the brightness of the LEDs by pulsing them. Additional methods, such as using an extra PBS to combine both color channels, are implemented to increase the contrast. After investigating the promising simulation results (119 lm D65 light with very high contrast and uniformity), we built a demonstrator setup. Our demonstrator produces a moderate light output (37.3 lm) on screen with a sufficient contrast ratio and a very good uniformity. In spite of semi color sequential working, the color breakup and crosstalk are negligible. The difference in performance and possible improvements will be discussed in the paper. (C) 2009 Elsevier B.V. All rights reserved.