Enhancing the output of a polarized light source using birefringent materials

Abstract

A light source may enhance the generation of circularly polarized light of a desired polarization state. The light that is produced by a lamp and initially rejected by a circular polarizer may be subjected to polarization reversal. The polarization reversed light may again impinge on the circular polarizer. A substantial percentage of the previously rejected and then polarization reversed light is passed by the circular polarizer.

What is claimed is:  
     
         1 . A light source comprising: 
 a lamp;    a circular polarizer to pass light in one polarization state; and    a device to reverse the state of polarization of light that is not passed by said circular polarizer, said device including a birefringent material.    
     
     
         2 . The light source of  claim 1  wherein said lamp is a high pressure discharge lamp.  
     
     
         3 . The light source of  claim 1  including a cavity, said material being coated on said cavity.  
     
     
         4 . The light source of  claim 3  including a reflective element that reflects light passed by said linear polarizer towards said circular polarizer.  
     
     
         5 . The light source of  claim 1  wherein the device is a quarter wave plate.  
     
     
         6 . The light source of  claim 5  wherein said reflector is a mirror positioned to reflect light passing through said plate back through said plate to impinge on said circular polarizer.  
     
     
         7 . The light source of  claim 5  wherein said quarter wave plate includes a birefringent coating.  
     
     
         8 . A reflective spatial light modulator comprising: 
 a light source including a lamp, a circular polarizer to pass light in one polarization state, and a device to reverse the polarization state of light that is not passed by said circular polarizer, said device including a birefringent material; and    a modulator to receive the light from said light source.    
     
     
         9 . The modulator of  claim 8  wherein said lamp is a high pressure discharge lamp.  
     
     
         10 . The modulator of  claim 8  wherein said materials acts as a quarter wave plate.  
     
     
         11 . The modulator of  claim 10  including a reflective element that reflects light passed by said material towards said circular polarizer.  
     
     
         12 . The modulator of  claim 11  wherein light rejected by said circular polarizer is linearly polarized, reflected, and then passed again to said circular polarizer.  
     
     
         13 . The modulator of  claim 12  wherein said reflector is a mirror positioned to reflect light passing through said linear polarizer back through said plate to impinge on said circular polarizer.  
     
     
         14 . The modulator of  claim 8  wherein said source includes a cavity coated with said material.  
     
     
         15 . A method comprising: 
 generating light;    passing a first portion of said light in a first circular polarization state and rejecting a second portion of said light in a second circular polarization state; and    reversing the polarization state of said second portion by passing said second portion through a birefringent material.    
     
     
         16 . The method of  claim 15  wherein passing includes causing said light to impinge on a circular polarizer that passes light in a first circular polarization state.  
     
     
         17 . The method of  claim 15  wherein reversing the polarization state of said second portion includes linearly polarizing said second portion.  
     
     
         18 . The method of  claim 15  wherein reversing includes passing the second portion through a quarter wave plate.  
     
     
         19 . The method of  claim 18  wherein reversing includes passing the second portion through a quarter wave plate two times.  
     
     
         20 . The method of  claim 19  including reflecting said second portion having passed through said plate one time in a first direction back through said plate in the opposite direction.  
     
     
         21 . The method of  claim 15  including coating the birefringent material on a surface exposed to said light.