Polarization conversion system

Abstract

A reflector, light source, phase retarder, and linear polarizer configured to increase a single-polarization output beam by converting wrong-polarization light into correct-polarization light. The linear polarizer reflects the wrong-polarization light and transmits the correct-polarization light. The phase retarder converts the wrong-polarization light into correct-polarization light, which is then transmitted by the linear polarizer.

What is claimed is:  
     
         1 . An apparatus comprising: 
 a reflector;    a light source for producing light of a first polarization and light of a second polarization;    a linear polarizer which substantially passes light of the first polarization and substantially reflects light of the second polarization; and    a phase retarder disposed between the reflector and the linear polarizer.    
     
     
         2 . The apparatus of  claim 1  wherein the phase retarder comprises a quarter-wave phase retarder.  
     
     
         3 . The apparatus of  claim 1  wherein the light source is disposed between the reflector and the phase retarder.  
     
     
         4 . The apparatus of  claim 1  wherein the linear polarizer comprises an optical substrate with a micro-structured wire grid type polarizer surface.  
     
     
         5 . The apparatus of  claim 4  wherein the linear polarizer further comprises airflow gaps for cooling the linear polarizer.  
     
     
         6 . The apparatus of  claim 1  wherein the reflector comprises a substantially parabolic mirror, and wherein the light source is disposed substantially at a focus of the parabolic mirror.  
     
     
         7 . The apparatus of  claim 6  wherein the linear polarizer comprises a substantially planar structure.  
     
     
         8 . The apparatus of  claim 6  wherein the linear polarizer and the phase retarder are suitably sized to collect light emitted from the reflector.  
     
     
         9 . The apparatus of  claim 1  wherein the light source is disposed between the phase retarder and the linear polarizer.  
     
     
         10 . The apparatus of  claim 9  wherein the phase retarder is mechanically coupled to the reflector and has substantially a same shape as the reflector.  
     
     
         11 . The apparatus of  claim 10  wherein the phase retarder and the reflector are substantially parabolic.  
     
     
         12 . The apparatus of  claim 9  wherein the light source comprises a substantially spherical light cavity having a reflective inner surface, and having a first window and a second window through the reflective inner surface, the first and second windows being disposed at substantially opposite sides of the light cavity.  
     
     
         13 . The apparatus of  claim 12  wherein the phase retarder and the reflector are disposed substantially in an optical path with the first window, and the linear polarizer is disposed substantially in an optical path with the second window.  
     
     
         14 . The apparatus of  claim 13  wherein the phase retarder, the reflector, and the linear polarizer are of substantially planar shape.  
     
     
         15 . The apparatus of  claim 9  wherein the light source comprises: 
 an RF-driven plasma light source having a bulb, and having a reflective coating surrounding the bulb and the phase retarder.  
 
     
     
         16 . An apparatus comprising: 
 a curved reflector having a concave reflective surface;    a quarter-wave phase retarder in an optical path with the curved reflective surface; and    a linear polarizer in the optical path.    
     
     
         17 . The apparatus of  claim 16  further comprising: 
 a light source in the optical path.  
 
     
     
         18 . The apparatus of  claim 16  wherein the curved reflector has a substantially parabolic shape.  
     
     
         19 . The apparatus of  claim 16  wherein the curved reflector has a substantially semi-parabolic shape.  
     
     
         20 . The apparatus of  claim 18  wherein the quarter-wave phase retarder and the linear polarizer are of substantially planar shape.  
     
     
         21 . The apparatus of  claim 20  further comprising: 
 a light source in the optical path and having a substantially spherical shape, a reflective interior, and two windows of reduced reflectivity, one of the windows positioned to transmit light to the quarter-wave phase retarder and the reflector, and the other of the windows positioned to transmit light to the linear polarizer.  
 
     
     
         22 . The apparatus of  claim 18  wherein the quarter-wave phase retarder has the substantially parabolic shape and the linear polarizer has a substantially planar shape.  
     
     
         23 . A system comprising: 
 linear polarizer means for transmitting light of a first polarization and for reflecting light of a second polarization;    phase retarder means for altering polarization of the light of the second polarization reflected from the linear polarizer means; and    reflector means for reflecting the altered polarization light from the phase retarder means back to the linear polarizer means.    
     
     
         24 . The system of  claim 23  wherein the reflector means is disposed so as to reflect the altered polarization light back through the phase retarder means, and wherein the phase retarder means is further for re-altering polarization of the light from the reflector.  
     
     
         25 . The system of  claim 24  wherein the phase retarder means is for altering the polarization of the light from the linear polarizer by one quarter phase and the light from the reflector by one quarter phase, to impart a one half phase alteration in polarization to light passing through it twice in the course of bouncing between the linear polarizer and the reflector.  
     
     
         26 . The system of  claim 23  further comprising means for providing the light of the first and second polarizations.  
     
     
         27 . The system of  claim 26  wherein the means for providing the light is disposed between the phase retarder means and the reflector means.  
     
     
         28 . The system of  claim 26  wherein the means for providing the light is disposed between the phase retarder means and the linear polarizer means.  
     
     
         29 . The system of  claim 23  wherein the reflector means comprises a substantially parabolic reflector.  
     
     
         30 . The system of  claim 23  wherein the reflector means comprises a substantially planar reflector.  
     
     
         31 . The system of  claim 23  further comprising a substantially spherical light source with a reflective inner surface.  
     
     
         32 . A method comprising: 
 transmitting first correct-polarization light through a linear polarizer;    reflecting wrong-polarization light from the linear polarizer;    correcting polarization of the wrong-polarization light to make it second correct-polarization light; and    transmitting the second correct-polarization light through the linear polarizer.    
     
     
         33 . The method of  claim 32  further comprising: 
 reflecting by a reflector light that has been reflected from the linear polarizer.  
 
     
     
         34 . The method of  claim 32  wherein the correcting comprises: 
 first altering polarization of the wrong-polarization light;  
 reflecting the altered-wrong-polarization light; and  
 second altering polarization of the altered-wrong-polarization light to make it the second correct-polarization light.  
 
     
     
         35 . The method of  claim 34  wherein the first and second altering each comprises: 
 passing its respective wrong-polarization light through a quarter-wave phase retarder.  
 
     
     
         36 . The method of  claim 35  further comprising: 
 generating the first correct-polarization light and the wrong-polarization light.