<title>New high-brightness compact LCD projector</title>

Abstract

A new high-brightness compact projector is presented, which uses three 9.4' AMLCD monochrome panels at 640 X 480 pixels. The projector produces a minimum brightness of 900lm (ANSI), with a minimum contrast ratio of 50:1 (ANSI) or 100:1 (full field) using a 575 W, 7 mm arc, metal halide lamp. The corner brightness is typically 60% of the center brightness due primarily to a novel integration method utilizing a rectangular integrator. Choosing large panels for the projector offered several advantages namely, high clear aperture ratio (66%), relaxed arc size requirements and lower energy density on the polarizers. The large LCD panels also introduced significant optical challenges and made a collimated light path impractical. A crossed dichroic `over-under' design was used to produce a compact system. Lower crossed dichroics split the light into red, green and blue primaries, and fold mirrors direct this light from the lower level to the upper level to pass through the panels. The three primary channels are recombined into a single path via a set of large crossed dichroic mirrors. Due to the non-collimated nature of the light path, it was necessary to employ non- linear gradient dichroic mirrors to ensure color uniformity.