Replay optics for holographic displays

Abstract

A holographic display comprises a spatial light modulator, SLM, arranged to display a set of tiled holographic images, and illuminating means for illuminating a surface of the SLM. Replay means are provided for focusing light reflected from the SLM surface to present a three dimensional image. The illuminating means comprises a light source appearing substantially at a DC spot position of the replay means.

1 . A holographic display comprising: 
 a spatial light modulator, SLM, arranged to display a set of tiled holographic images;    illuminating means for illuminating a surface of the SLM; and    replay means for focusing light reflected from the SLM surface to present a three dimensional image,    characterised in that the illuminating means comprises a light source appearing substantially at a DC spot position of the replay means.    
     
     
         2 . A display according to  claim 1 , wherein the SLM is an optically addressed spatial light modulator, OASLM, and is located in front of optical components arranged to illuminate a rear surface of the OASLM with light corresponding to said holographic images.  
     
     
         3 . A display according to  claim 2 , wherein said optical components comprise an electrically addressed spatial light modulator, EASLM, which is arranged to display each of said holographic images in sequence and replicating optics for directing light from the EASLM to the OASLM.  
     
     
         4 . A display according to  claim 1 , wherein the SLM is an EASLM.  
     
     
         5 . A display according to  claim 1 , wherein said light source comprises a mirror, and the illuminating means further comprises a laser or other light generating means arranged to direct light onto the mirror.  
     
     
         6 . A display according to  claim 1 , wherein said illuminating means is arranged to cause an aberrated point source to appear at the DC spot, the aberration being such that it negates aberrations in the replay optics.  
     
     
         7 . A display according to  claim 6 , wherein the illuminating means comprises aberrating optics in front of the light generating means.  
     
     
         8 . A holographic display comprising: 
 a spatial light modulator, SLM, arranged to display one or more holographic images;    replay means for focusing light reflected from the SLM surface to present a three dimensional image;    a light source for illuminating a surface of the SLM and arranged to cause an aberrated point source to appear substantially at a DC spot position of the replay means so as to compensate for aberrations in the replay optics.    
     
     
         9 . A method of illuminating a surface of a spatial light modulator (SLM) forming part of a holographic display, the method comprising: 
 directing light from a point source appearing to be located at a DC spot position of replay optics, into the replay optics, and aberrating the light to compensate for aberrations in the replay optics.