Rear projection screen with spatial varying diffusing angle

Abstract

A Fresnel lens of the prior art is split into two Fresnel lenses to allow easier control of the horizontal and vertical viewing angles. In a second embodiment, the Fresnel lens is entirely eliminated. Instead, the diffuser contains elliptical microstructures so that the diffusing cones in orthogonal directions are different, eliminating the need for a Fresnel lens to perform this function. To compensate for the absence of the light collimation provided by the Fresnel lens, a diffuser with spatially varying diffusing angles is used.

1 . A projection screen comprising: 
 a first Fresnel lens configured to diverge light at a first angle;    a second Fresnel lens, coupled to said first Fresnel lens, and configured to diverge light at a second angle; and    a diffuser coupled to said second Fresnel lens.    
   
   
       2 . The screen of  claim 1  wherein said first Fresnel lens is a cylindrical Fresnel phase relief structure derived from a function y(x)=Mod(D(x), mλ) where  
     
       
         
           
             
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                     λϕ 
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       3 . The screen of  claim 1  wherein said second Fresnel lens has a focusing axis rotated 90 degrees from said first Fresnel lens.  
   
   
       4 . The screen of  claim 1  wherein the focal lengths of said Fresnel lenses are not identical.  
   
   
       5 . The screen of  claim 1  wherein the structural depths of said Fresnel lenses are less than 10 μm.  
   
   
       6 . The screen of  claim 1  wherein a diffusing cone from said diffuser has aspect ratio larger than 2:1.  
   
   
       7 . The screen of  claim 1  wherein said diffuser is the only diffusing layer.  
   
   
       8 . The screen of  claim 6  wherein the diffusing cone of said diffuser changes spatially.  
   
   
       9 . A system for constructing a cylindrical Fresnel phase relief structure, comprising: 
 a laser device for producing a laser beam;    a spatial light modulator;    a lens;    a two axis translator; and    a light sensitive recording material mounted on said two axis translator,    wherein said spatial light modulator is configured to produce on said recording material, through said lens and in conjunction with said two axis translator, a phase relief structure derived from a function y(x)=Mod(D(x), mλ) where              D   ⁡     (   x   )       =         x   2       2   ⁢   n   ⁢           ⁢   F       +         λϕ   ⁡     (   x   )         2   ⁢   n   ⁢           ⁢   π       .               
   
   
       10 . The system of  claim 9  wherein said spatial light modulator controls the shape and brightness of a laser spot on the said recording surface.  
   
   
       11 . A system for constructing a diffuser for a projection screen, comprising: 
 a laser device for generating a laser beam:    a rotating diffuser mounted to receive said laser beam;    a first lens mounted to receive a diffused laser beam from said rotating diffuser;    a spatial modulator mounted to receive a modified laser beam from said first lens;    a second lens mounted to receive a spatially modulated laser beam from said spatial modulator;    a two axis translator mounted after said second lens; and    a light sensitive recording material mounted on a two axis translator;    wherein said spatial modulator and said two axis translator are configured to operate to produce a spatial varying diffuser.    
   
   
       12 . The system of  claim 11  wherein said first lens produces a spatial spectrum of said diffuser.  
   
   
       13 . The system of  claim 11  wherein said spatial light modulator controls spectral region of the diffuser.  
   
   
       14 . The system of  claim 11  wherein said second lens images the diffuser to the recording surface.  
   
   
       15 . A system for constructing a diffuser comprising: 
 a laser device producing a laser beam:    a spatial light modulator mounted to receive said laser beam;    a lens mounted to receive a spatially modulated beam from said spatial light modulator;    a two axis translator mounted after said lens; and    a light sensitive recording material mounted on said two axis translator;    wherein said spatial modulator and said two axis translator are configured to operate to produce a spatial varying diffuser.    
   
   
       16 . The system of  claim 15  wherein said lens performs a Fourier transform on the pattern displayed on said spatial light modulator.  
   
   
       17 . The system of  claim 15  wherein the pattern displayed on said spatial light modulator is the Fourier transform of a random phase function.  
   
   
       18 . A projector system comprising: 
 a projector; and    a screen having spatially varying diffusion properties;    such that the angle of light rays projected from said screen increase with an increasing deviation from a center of said screen in at least one direction.    
   
   
       19 . The system of  claim 18  wherein said direction is horizontal.  
   
   
       20 . The system of  claim 18  wherein said screen comprises a plurality of diffusing dots.  
   
   
       21 . A method for constructing a cylindrical Fresnel phase relief structure, comprising: 
 producing a laser beam;    spatially modulating said laser beam to produce a spatially modulated laser beam;    focusing said spatially modulated laser beam on a recording material; and    translating said recording material along two axes;    wherein said spatially modulating and said translating produce on said recording material a phase relief structure derived from a function y(x)=Mod(D(x),mλ) where              D   ⁡     (   x   )       =         x   2       2   ⁢   n   ⁢           ⁢   F       +         λϕ   ⁡     (   x   )         2   ⁢   n   ⁢           ⁢   π       .               
   
   
       22 . A method for constructing a diffuser for a projection screen, comprising: 
 generating a laser beam:    rotating a diffuser to diffuse said laser beam to produce a diffused laser beam;    collimating said diffused laser beam to produce a collimated laser beam;    spatially modulating said collimated laser beam to produce a spatially modulated laser beam;    focusing said spatially modulated laser beam on a recording material; and    translating said recording material along two axes;    wherein said spatially modulating and said translating operate to produce a spatial varying diffuser on said recording material.    
   
   
       23 . A method for constructing a diffuser comprising: 
 providing a collimated laser beam;    spatially modulating said collimated laser beam to produce a spatially modulated laser beam;    focusing said spatially modulated laser beam on a recording material; and    translating said recording material along two axes;    wherein said spatially modulating and said translating operate to produce a spatial varying diffuser.