Display with variably transmissive element

Abstract

A display includes an image source for generating light and a lensing system. The lensing system defines an optical path from an input to an output, receiving the generated light at the input and transmitting light at the output. The lensing system includes a variably transmissive element which maintains contrast between the transmitted light and an ambient light.

What is claimed is:  
     
         1 . A display apparatus, comprising: 
 an image source for generating light;    a lensing system defining an optical path from an input to an output, the lensing system receiving the generated light at the input and transmitting light at the output, the lensing system comprising a variably transmissive element which maintains contrast between the transmitted light and an ambient light.    
     
     
         2 . A display apparatus according to  claim 1 , in which the variably transmissive element comprises a photochromic material which alters transmissiveness of the variably transmissive element as a function of the ambient light.  
     
     
         3 . A display system comprising: 
 an image generator responsive to an image signal to generate image light;    a variably transmissive element which changes transmissiveness as a function of ambient light to attenuate light passing through the variable transmissive element, wherein light including the image light and the attenated light is presented for viewing.    
     
     
         4 . A display system according to  claim 3 , in which the variably transmissive element is a passively variable transmissive element light which changes transmissiveness as a function of ambient light.  
     
     
         5 . A display system according to  claim 3 , in which the optical element is an actively variable transmissive element light which receives a control signal to actively vary the transmissiveness of the optical element.  
     
     
         6 . A display system according to  claim 5 , further comprising a photosensor responsive to the ambient light, the photosensor generating the control signal.  
     
     
         7 . A display system according to  claim 3 , in which the variably transmissive element comprises a liquid crystal device.  
     
     
         8 . A method of display, comprising: 
 generating image light in response to an image signal;    receiving the image light at a lensing system, the lensing system including a variably transmissive element;    varying transmissiveness of the variably transmissive element as a function of ambient light received at the variably transmissive element to maintain contrast between the image light and the ambient light.    
     
     
         9 . A method of display according to  claim 8 , in which said variably transmissive lement comprises photochromic material and said varying comprises: 
 passively varying transmissiveness of the variably transmissive element as a function of the ambient light.    
     
     
         10 . A method of display according to  claim 8 , further comprising: 
 sensing ambient light with a photosensor, wherein the variably transmissive element is actively variable in response to the sensed ambient light.