Patent ID: 6023365
Filing Date: 2000-02-08
Classification: G02B,G03H,H04N

Abstract:
A apparatus for coupling an illumination light to a digital micro-mirror device (DMD) and for preserving a wavefront property of a useful illumination light, wherein said DMD has a plurality of micro-mirrors, and each micro-mirror is adjustable between a first position and a second position, and said useful illumination light is a reflection of said illumination light by at least one of said micro-mirrors in said first position, comprising:a) a first prism comprising a first side surface, a second side surface and a third surface;b) a second prism comprising a fourth side surface, a fifth side surface and a sixth side surface, wherein said fourth side surface is substantially adjacent to said second side surface;c) an angularly selective film, positioned between said second side surface and said fourth side surface, having a predetermined thickness and a profile index of refraction;wherein:said illumination light enters said first side surface, is reflected by said angularly selective film at said second surface at a first angle, exits said third side surface, is incident on said micro-mirrors, andsaid useful illumination light enters said third side surface at a substantially normal angle, passes said first prism, exits said second side surface, passes said angularly selective film at a second angle, enters said fourth side surface, passes said fifth side surface at a substantially normal angle.