Two LCOS full color projector with efficient LED illumination engine

LED-based projectors have numerous advantages compared to traditional projectors. They are more compact, exhibit a larger color gamut and a longer lifetime, the supply voltage is lower and they can operate on batteries. However their light output is limited by the low optical power per étendue of the LEDs, although this is also improving constantly. With an efficient illumination engine design we can build an LED projector with a moderate light output and with superior properties. We present a compact LED projector with two ‘Liquid Crystal On Silicon’ (LCOS) panels. One of these panels is alternately modulating red and blue information while the other permanently modulates the green information to achieve the D65 white point. This architecture is first simulated using ray-tracing software. After testing the several parts of this architecture experimentally, we have 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, within a system étendue lower than 20 mmsr. In spite of semi color sequential working, the color breakup and crosstalk are negligible.