Fiberoptic face plate stop for digital micromirror device projection

Abstract

A digital micromirror device projection system employs an array of digitally operable micromirrors that are individually and selectively tiltable between ON and OFF positions. The array of mirrors is illuminated by a high intensity light source, and light reflected from those mirrors selectively driven to the ON tilted position is reflected to a projection lens for projection onto a screen. Concomitantly, light reflected from those of the mirrors in the OFF position are blocked by a system stop. The system stop is formed by a wedge-shaped bundle of optical fibers positioned immediately adjacent the mirror array. The fiber axes are all mutually parallel and are perpendicular to the mutually parallel planes of those of the mirrors that are tilted to the ON position so that the illuminating light is incident upon the mirrors in a perpendicular relationship and is retroreflected back through the optical fibers to the projection lens of the system. The optical fibers have a very small numerical aperture and act as a system stop to block light from those mirrors that are in OFF position. Light from the illuminating source passing through the fiberoptic face plate and impinging upon the OFF position mirrors is reflected back at an angle to the axes of the fibers that is not within the acceptance angle of the fibers.