Light separation device, blazed grating device, diffraction grating device, and illumination optical system

Abstract

A thin and light optical device satisfactorily separates light components having different properties. A blazed grating is formed on a surface of a flat-plate-shaped transparent substrate, and a separation coating that reflects or transmits incident light according to the properties of the incident light is provided on the blazed grating. The thus obtained optical device offers a function of separating light into reflected light and transmitted light, and also has a function of diffracting or refracting the thus separated light. As the separation coating, a polarization separation film, dichroic film, angle separation film, or chiral nematic liquid crystal layer is used to separate linearly polarized light components having different polarization planes, light components having different wavelengths, light components incident at different angles of incidence, or circularly polarized light components having different rotation directions.

1 - 34 . (canceled)  
     
     
         35 . A blazed grating device comprising: 
 a plate-shaped transparent substrate having a blazed grating formed on a surface thereof; and    a separation coating formed on the blazed grating of the transparent substrate so as to reflect or transmit incident light according to properties of the incident light.    
     
     
         36 . A blazed grating device as claimed in  claim 35 , further comprising: 
 a plate-shaped transparent member kept in intimate contact with the blazed grating of the transparent substrate with the separation coating sandwiched in between.    
     
     
         37 . A blazed grating device as claimed in  claim 36 , further comprising: 
 a blazed grating formed on a surface of the transparent member that faces away from the transparent substrate;    a separation coating formed on the blazed grating of the transparent member so as to reflect or transmit incident light according to properties of the incident light; and    a plate-shaped transparent member kept in intimate contact with the blazed grating of the transparent member with the separation coating sandwiched in between.    
     
     
         38 . A blazed grating device as claimed in  claim 35 , 
 wherein the separation coating reflects or transmits the incident light according to how the incident light is polarized.    
     
     
         39 . A blazed grating device as claimed in  claim 35 , 
 wherein the separation coating reflects or transmits the incident light according to a wavelength of the incident light.    
     
     
         40 . A blazed grating device as claimed in  claim 35 , 
 wherein the separation coating reflects or transmits the incident light according to an angle of incidence of the incident light.    
     
     
         41 . A diffraction grating device comprising: 
 a plate-shaped transparent substrate having a diffraction grating formed on a surface thereof;    a separation coating formed on the diffraction grating of the transparent substrate so as to reflect or transmit incident light according to how the incident light is polarized; and    a plate-shaped transparent member kept in intimate contact with the diffraction grating of the transparent substrate with the separation coating sandwiched in between.    
     
     
         42 . A diffraction grating device as claimed in  claim 41 , 
 wherein light reflected from the separation coating is totally reflected inside the transparent substrate and is thereby directed to an end surface of the transparent substrate.    
     
     
         43 . An illumination optical system comprising: 
 a diffraction grating device comprising: 
 a plate-shaped transparent substrate having a diffraction grating formed on a surface thereof; and  
 a separation coating formed on the diffraction grating of the transparent substrate so as to reflect or transmit incident light according to properties of the incident light,  
   wherein the illumination optical system uses the diffraction grating device both to direct light to an object to be illuminated so as to illuminate the object and to direct light reflected from the object out of the illumination optical system by letting this light pass through the diffraction grating.    
     
     
         44 . An illumination optical system as claimed in  claim 43 , 
 wherein the diffraction grating device further comprises: 
 a plate-shaped transparent member kept in intimate contact with the diffraction grating of the transparent substrate with the separation coating sandwiched in between.  
   
     
     
         45 . An illumination optical system as claimed in  claim 43 , 
 wherein the separation coating reflects or transmits the incident light according to an angle of incidence of the incident light.    
     
     
         46 . An illumination optical system as claimed in  claim 43 , 
 wherein the separation coating is a chiral nematic liquid crystal layer that reflects one and transmits another of two circularly polarized light components having different rotation directions.