Projection System for Passive Display
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
A wide angle, high aperture projection system for a small reflective passive display of the electrochromic or liquid crystal type includes off-axis illumination via a light deflector, such as a mirror or prism, occupying half the aperture of the projection lens arrangement. The projection lenses consist of a rear group of positive power, near the passive display cell, and a remote front group of negative power. The light deflector is located between the two groups of lenses at the pupil of the rear group in a telecentric arrangement. Light valves, and other systems which are used to project large images onto diffusing surfaces, require projection optics which combine relatively high aperture with relatively large field angles. High aperture lenses, working, for example, at f/1.