Polarization recovery system for projection displays

Abstract

A waveguide polarization recovery system both polarizes the input light energy for use with an LCD imager and converts the polarity of unusable light energy to add to the illumination of the LCD imager. The compact polarization recovery waveguide system generally includes: (1) an input waveguide that provides non-polarized light energy into the system; (2) an output waveguide that receives polarized light energy from the system; (3) a polarized beam splitter that received the light energy from the input waveguide and transmits light energy of a first polarization type and reflects light energy of a second polarization type, and (4) a wave plate that modifies the polarization of either the transmitted or reflected light energy. The polarization recovery system also generally includes one or more mirrors that are positioned as need to direct the transmitted and the reflected light energy to the output waveguide. The input and output waveguides may be shaped as needed by the projection system. For example, either one or both of the input and output waveguides may be tapered as needed to produce a desired image. In the waveguide polarization recovery system, the input and output waveguides are configured to have either an either a substantially parallel or a substantially perpendicular orientation. In another embodiment, the waveguide polarization recovery system further includes has one or more “gaps” of optically clear material positioned between the optical components to encourage the occurrence to total internal reflection that minimizes the loss of the optical energy by the system.

1 . A light engine for a projection display system comprising: 
 a beam splitter for splitting light from a source into two or more light components;    a light guide comprising:    at least a source branch for guiding light from said source to said beam splitter; and    at least first and second component branches for guiding said light components away from said beam splitter;    each of said source branch and said first and second component branches consisting of at least one straight light guide section of rectangular cross-section and at least one light coupling element.    
     
     
         2 . The lighting apparatus of  claim 1 , further comprising a recombiner for recombining said two or more light components.  
     
     
         3 . The apparatus of  claim 2 , further comprising an output lens for directing said recombined light components out of said lighting apparatus.  
     
     
         4 . A projection display system, comprising: 
 a light engine for a projection display system comprising:    a beam splitter for splitting light from a source into two or more light components;    a light guide comprising:    at least source branch for guiding light from said source to said beam splitter; and    at lest first and second component branches for guiding said light components away from said beam splitter;    each of said source branch and said first and second component branches consisting of at least one straight light guide section of rectangular cross-section and at least one light coupling element;    at least one light modulator panel for modulating light in accordance with a display signal; and    a projection lens for projecting the modulated light onto a display screen.    
     
     
         5 . The projection display system of  claim 4  in which a polarizer and polarizing beam splitter (PBS) are provided between the light engine and the light modulating panel, the PBS having a surface for transmitting light of a first polarization state transverse to the first polarization state.