Polarization beam splitter and method of producing the same

Abstract

Disclosed is a polarization beam splitter and a method of producing the same, in which the polarization beam splitter has superior polarization separation efficiency and has small angle dependence. A transparent base material having a polarization separation film, comprising a dielectric multilayered film, is cemented at the cemented surface of the beam splitter, to provide an array-like plane type polarization beam splitter, wherein an incidence angle θg of light upon the polarization separation film is selected to satisfy a relation θg>45 deg.

1 . A polarization beam splitter having an array-like planar shape, comprising: 
 a transparent base material having a polarization separation film, made of a dielectric multilayered film, cemented at a cemented surface between arrays, wherein an incidence angle θg of a principal direction from which light is incident upon the polarization separation film satisfies a relation θg>45 deg. and wherein an angle formed by a normal to a light incidence surface of said polarization beam splitter and an optical axis of the light incidence angle of said polarization beam splitter is not less than 0 deg. and not more than 20 deg.    
     
     
         2 . A polarization beam splitter according to  claim 1 , wherein a polarization separation cemented surface provided by a dielectric multilayered film of an incidence angle θg>45 deg. and a cemented surface provided by an S-polarization reflection film having the same incidence angle with the polarization separation cemented surface, are combined into a pair, and wherein a plurality of such pairs are used and combined into the array-like planar structure.  
     
     
         3 . A polarization beam splitter according to  claim 1 , wherein the angle θg is in a range of 45 deg.<θg<60 deg.  
     
     
         4 . A polarization beam splitter according to  claim 1 , wherein the angle θg is in a range of 49 deg.<θg<56 deg.  
     
     
         5 . (Canceled)  
     
     
         6 . A polarization beam splitter according to  claim 1 , wherein the polarization separation film comprises alternate layers of TiO 2  as a high refractive index material and SiO 2  as a low refractive index material, and wherein said base material has a refractive index of about 1.52.  
     
     
         7 . A polarization beam splitter according to  claim 1 , wherein said polarization separation film comprises alternate layers of high and low refractive index materials, of a number not greater than fourteen.  
     
     
         8 . A polarization beam splitter according to  claim 1 , wherein said polarization separation film comprises alternate layers of high and low refractive index materials, of a number not greater than eleven.  
     
     
         9 . A polarization converting element for transforming non-polarized light into linearly polarized light, comprising: 
 a polarization beam splitter as recited in  claim 1;  and    a waveplate for registering a polarization direction of one of two polarized lights, being separated by said polarization separation film of said polarization beam splitter, with a polarization direction of the other polarized light.    
     
     
         10 . A polarization converting element according to  claim 9 , wherein said waveplate is a half waveplate.  
     
     
         11 . An image display unit, comprising: 
 an illumination optical system for illuminating an image display element with light from a light source; and    a projection optical system for projecting light from the image display element onto a projection surface onto which the light is to be projected,    wherein said illumination optical system includes a polarization converting element as recited in  claim 9 .    
     
     
         12 - 14 . (Canceled)  
     
     
         15 . A method of producing a polarization beam splitter of array-like planar type, comprising the steps of: 
 providing a transparent base material having a polarization separation film, comprising a dielectric multilayered film, cemented at a cemented surface, wherein an incidence angle θg of light upon the polarization separation film is set to satisfy a relation θg>45 deg., and wherein an angle formed by a normal to a light incidence surface of said polarization beam splitter and an optical axis of the light incidence angle of said polarization beam splitter is not less than 0 deg. and not more than 20 deg.;    combining into a pair a polarization separation cemented surface provided by a dielectric multilayered film of an incidence angle θg>45 deg. and a cemented surface provided by an S-polarization reflection film having the same incidence angle with the polarization separation cemented surface; and    combining a plurality of such pairs into an array-like planar structure.    
     
     
         16 . A method according to  claim 15 , wherein the angle θg is in a range of 45 deg.<θg<60 deg.  
     
     
         17 . (Canceled)  
     
     
         18 . A method according to  claim 15 , wherein the polarization separation film comprises alternate layers of TiO 2  as a high refractive index material and SiO 2  as a low refractive index material, and wherein a base material has a refractive index of about 1.52.