Optical system for miniature personal displays using reflective light valves

Abstract

An illumination system and display are disclosed that include a light for providing light, a polarizing beam splitter (PBS) having a first surface that receives the light from the backlight. The PBS passes a first polarization of the received light to a curved mirror located at a second PBS face, which second PBS face is opposite the first PBS face. The curvature of the mirror provides the optical power necessary for proper imaging, while limiting the reflecting area of the mirror provides an aperture stop that determines the numerical aperture of the optical system. The display also includes a quarter wave plate and a spatial light modulator (SLM). The quarter wave plate is located between the PBS and mirror and changes the first polarization of light, directed from the PBS to the mirror, to a second polarization which is reflected from the mirror back to the PBS. The SLM receives this second polarization of light after reflection thereof by the PBS, and selectively rotates the second polarization of light to form an image forming light having the first polarization, which is reflected back to the PBS. Through an exit face, the PBS provides the rotated image forming light to a viewer. Between the viewer and the PBS exit surface, an imaging lens system is provided that includes at least one folding mirror.

Having thus described our invention, what we claim as new, and desire to secure by Letters Patent is:  
     
         1 . An illumination system for a display comprising: 
 a light source for providing a light;    a polarizing beam splitter for splitting said light into first and second polarizations; and    a reflective device for reflecting light received from said polarizing beam splitter back to said polarizing beam splitter.    
     
     
         2 . The illumination system of  claim 1 , wherein said reflective device is an aperture stop that determines a numerical aperture of the illumination system.  
     
     
         3 . The illumination system of  claim 2 , wherein said reflective device reflects light within said numerical aperture back to said polarizing beam splitter, and rejects light falling outside said numerical aperture onto a light absorbing substrate.  
     
     
         4 . The illumination system of  claim 1 , wherein a reflective surface of said reflective device provides an aperture stop.  
     
     
         5 . The illumination system of  claim 1 , wherein said reflective device is a mirror.  
     
     
         6 . The illumination system of  claim 1 , wherein said reflective device is curved to provide a predetermined optical power.  
     
     
         7 . The illumination system of  claim 1  further comprising a spatial light modulator for rotating a polarization of said light reflected back to said polarizing beam splitter from said reflective device, and reflecting said rotated light back to said polarizing beam splitter.  
     
     
         8 . The illumination system of  claim 1  further comprising a quarter wave plate located between said polarizing beam splitter and said reflective device.  
     
     
         9 . The illumination system of  claim 1  further comprising a lens located between said light source and said polarizing beam splitter, said lens directing said light from said light source to said polarizing beam splitter.  
     
     
         10 . The illumination system of  claim 1  further comprising a collimating film located between said light source and said polarizing beam splitter, wherein said collimating film collimates said light from said light source.  
     
     
         11 . The illumination system of  claim 1  further comprising a polarizing plate located between said light source and said polarizing beam splitter, wherein said polarizing plate provides polarization control of said light from said light source.  
     
     
         12 . The illumination system of  claim 7  further comprising a lens located between said polarizing beam splitter and said spatial light modulator, wherein said lens provides said light to said spatial light modulator in a substantially normal direction to said spatial light modulator.  
     
     
         13 . The illumination system of  claim 7  further comprising a polarizing plate disposed on an exit surface of said polarizing beam splitter, said exit surface being opposite a polarizing beam splitter surface facing said spatial light modulator.  
     
     
         14 . The illumination system of  claim 7  further comprising an imaging lens system located between a viewer and an exit surface of said polarizing beam splitter, said exit surface being opposite a polarizing beam splitter surface facing said light modulator.  
     
     
         15 . The illumination system of  claim 14 , wherein said imaging lens system includes at least one folding mirror.  
     
     
         16 . A display for projecting an image comprising: 
 a backlight source for providing a light;    a polarizing beam splitter having a first surface that receives the light from the backlight source, said polarizing beam splitter passing a first polarization and reflecting a second polarization of the received light;    a reflector that receives said first polarization of light from said polarizing beam splitter and reflects it back to the polarizing beam splitter;    a quarter wave plate disposed between said polarizing beam splitter and said reflector, said quarter wave plate changing said first polarization of light from said polarizing beam splitter to said second polarization of light received by said polarizing beam splitter from said reflector;    a spatial light modulator that receives from said polarizing beam splitter said second polarization of light received by said polarizing beam splitter from said reflector, said spatial light modulator selectively rotating said received second polarization of light to form an image forming light of said first polarization, and reflecting said image forming light toward a viewer through said polarizing beam splitter.    
     
     
         17 . The display of  claim 16 , wherein said reflector is an aperture stop that determines a numerical aperture of the illumination system.  
     
     
         18 . The display of  claim 17 , wherein said reflector reflects light within said numerical aperture back to said polarizing beam splitter, and reflects light falling outside said numerical aperture to a light absorbing substrate.  
     
     
         19 . The display of  claim 16 , wherein a reflective surface of said reflector provides an aperture stop.  
     
     
         20 . The display of  claim 16 , wherein said reflector is curved to provide a predetermined optical power.  
     
     
         21 . The display of  claim 16  further comprising a lens located between said backlight source and said polarizing beam splitter, said lens directing said light from said backlight source to said polarizing beam splitter.  
     
     
         22 . The display of  claim 16  further comprising a collimating film located between said backlight source and said polarizing beam splitter, wherein said collimating film collimates said light from said backlight source.  
     
     
         23 . The display of  claim 16  further comprising a polarizing plate located between said backlight source and said polarizing beam splitter, wherein said polarizing plate provides polarization control of said light from said backlight source.  
     
     
         24 . The display of  claim 16  further comprising a lens located between said polarizing beam splitter and said spatial light modulator, wherein said lens provides said light to said spatial light modulator in a substantially normal direction to said spatial light modulator.  
     
     
         25 . The display of  claim 16  further comprising a polarizing plate disposed on an exit surface of said polarizing beam splitter, said exit surface being opposite a polarizing beam splitter surface facing said spatial light modulator.  
     
     
         26 . The display of  claim 16  further comprising an imaging lens system located between the viewer and an exit surface of said polarizing beam splitter, said exit surface being opposite a polarizing beam splitter surface facing said light modulator.  
     
     
         27 . The illumination system of  claim 26 , wherein said imaging lens system includes at least one folding mirror.