Color combining optical system and image projection apparatus

Abstract

A color combining optical system is disclosed, with which light of a plurality of colors can be combined while reducing the loss of light due to fluctuations in the incidence angle on a polarization color combining film. The color combining optical system, which combines a first color light and a second color light, includes a polarization color combining film made of a multilayer film. The polarization color combining film combines a first polarization component of the first color light and a second polarization component of the second color light, which has a polarization direction substantially perpendicular to the first polarization component, with an efficiency of 90% or more in a predetermined incidence angle range.

1 . A color combining optical system, which combines a first color light and a second color light, comprising: 
 a polarization color combining film made of a multilayer film;    wherein the polarization color combining film combines a first polarization component of the first color light and a second polarization component of the second color light, which has a polarization direction substantially perpendicular to the first polarization component, with an efficiency of 90% or more in a predetermined incidence angle range.    
   
   
       2 . The color combining optical system according to  claim 1 , 
 wherein the predetermined incidence angle range is a range of a reference incidence angle ±5° with respect to the polarization color combining film.    
   
   
       3 . The color combining optical system according to  claim 1 , 
 wherein the color combining optical system combines the first color light and the second color light, respectively coming from a first and a second image forming element forming an original image, and guides the combined light to a projection optical system;    wherein the color combining optical system further comprises a first and a second analyzing member; and    wherein the first color light is guided via the first analyzing member and the polarization color combining film to the projection optical system, and the second color light is guided via the second analyzing member and the polarization color combining film to the projection optical system.    
   
   
       4 . The color combining optical system according to  claim 1 , 
 wherein the first color light is light of a green wavelength range and the second color light is light of a red and blue wavelength range.    
   
   
       5 . The color combining optical system according to  claim 1 , 
 wherein the color combining optical system combines the first color light and the second color light, respectively coming from a first and a second image forming element forming an original image, with a third color light from a third image forming element forming an original image, and guides the combined light to a projection optical system;    wherein the color combining optical system further comprises a first and a second analyzing member; and    wherein the first color light is guided via the first analyzing member and the polarization color combining film to the projection optical system, and the second color light and the third color light is guided via the second analyzing member and the polarization color combining film to the projection optical system.    
   
   
       6 . The color combining optical system according to  claim 5 , 
 wherein the second analyzing member is a polarization beam splitter; and    wherein a color-selective wave plate is provided between the polarization beam splitter and the polarization color combining film.    
   
   
       7 . The color combining optical system according to  claim 5 , 
 wherein the first analyzing member comprises a first polarization beam splitter and a first polarizing plate, and the second analyzing member comprises a second polarization beam splitter;    wherein a color-selective wave plate is provided between the second polarization beam splitter and the polarization color combining film, and a second polarizing plate is provided between the color-selective wave plate and the polarization color combining film.    
   
   
       8 . The color combining optical system according to  claim 7 , 
 wherein the first polarization beam splitter and the second polarization beam splitter are comprised of polarization splitting films which have the same characteristics.    
   
   
       9 . The color combining optical system according to  claim 5 , 
 wherein the first color light is light of a first wavelength region of 50° to 570 nm, the second color light is light of a second wavelength region of 430 to 480 nm, and the third color light is light of a third wavelength region of 590 to 650 nm.    
   
   
       10 . The color combining optical system according to  claim 9 , 
 wherein, when an incidence angle of the light incident on the polarization color combining film is 45°±5°, then a transmittance of the polarization color combining film in the first wavelength region is 90% or more and a reflectance of the polarization color combining film in the second wavelength region and the third wavelength region is 90% or more.    
   
   
       11 - 13 . (canceled)  
   
   
       14 . The color combining optical system according to  claim 9 , 
 wherein, when the incidence angle of the light incident on the polarization color combining film is 45°±5°, then a reflectance of the polarization color combining film in the first wavelength region is 90% or more and a transmittance of the polarization color combining film in the second wavelength region and the third wavelength region is 90% or more.    
   
   
       15 - 17 . (canceled)  
   
   
       18 . An image projection apparatus, comprising: 
 a light source;    a color separating optical system which separates light from the light source into at least a first color light and a second color light;    at least two image forming elements;    a color combining optical system according to  claim 1 , which combines the first color light and the second color light from the image forming elements; and    a projection optical system which projects light combined by the color combining optical system.    
   
   
       19 . The image projection apparatus according to  claim 18 , 
 wherein the image forming elements are reflective image forming elements.