Display Method and Display Apparatus

Abstract

A display method lets a display beam to propagate in a transparent substrate while internally reflected repeatedly and lets the display beam partly emit out of the transparent substrate every time the display beam is internally reflected, thereby emitting display beams from almost entirety of a surface of the transparent substrate. The display beam is produced holographically. A display apparatus includes a spatial phase modulator that produces a display beam, a transparent substrate in which the display beam is internally reflected repeatedly to propagate in it, and a splitter that lets the display beam partly emit out of the transparent substrate every time the display beam is internally reflected.

What is claimed is: 
     
         1 . A display method comprising:
 letting a display beam to propagate in a transparent substrate while internally reflected repeatedly; and   letting the display beam partly emit out of the transparent substrate every time the display beam is internally reflected, thereby emitting the display beams from almost entirety of a surface of the transparent substrate,   wherein the display beam is produced holographically.   
     
     
         2 . A display apparatus according to  claim 1 , wherein the coherence length of the display beam is shorter than the distance through which the display beam propagates by one internal reflection. 
     
     
         3 . A display apparatus according to  claim 2 , wherein the display beam emitting out of the transparent substrate displays a virtual image at infinity. 
     
     
         4 . A display apparatus comprising:
 a spatial phase modulator that produces a display beam;   a transparent substrate in which the display beam is internally reflected repeatedly to propagate in it; and   a splitter that lets the display beam partly emit out of the transparent substrate every time the display beam is internally reflected.   
     
     
         5 . A display apparatus according to  claim 4 , wherein the spatial phase modulator produces the display beam holographically. 
     
     
         6 . A display apparatus according to  claim 5 , wherein the apparatus uses two transparent substrates. 
     
     
         7 . A display apparatus according to  claim 5 , wherein the spatial phase modulator is arranged in such a way that the condition that zero-order light produced by the spatial phase modulator is transmitted through the transparent substrate and first order-light is totally reflected by the transparent substrate is met. 
     
     
         8 . A display apparatus according to  claim 7 , wherein a convergent beam is made incident on the spatial phase modulator, and the apparatus is provided with a trap that traps the zero order light. 
     
     
         9 . A display apparatus according to  claim 5 , wherein the coherence length of the display beam is shorter than the distance through which the display beam propagates by one internal reflection. 
     
     
         10 . A display apparatus according to  claim 5 , wherein the splitter comprises a diffraction grating. 
     
     
         11 . A display apparatus according to  claim 10 , wherein the diffraction grating comprises a volume hologram. 
     
     
         12 . A display apparatus comprising:
 a spatial phase modulator that produces a display beam holographically;   a first transparent substrate and a second transparent substrate in which the display beam is internally reflected repeatedly to propagate in them;   a splitter that lets the display beam partly enter the second transparent substrate every time the display beam is internally reflected in the first transparent substrate; and   a splitter that lets the display beam partly emit out of the second transparent substrate every time the display beam is internally reflected in the second transparent substrate,   wherein the coherence length of the display beam is shorter than the distance through which the display beam propagates by one internal reflection.   
     
     
         13 . A display apparatus comprising:
 a light source;   a transparent substrate having a first transmitting surface and a second transmitting surface;   a spatial phase modulator arranged between the light source and the second transmitting surface; and   a splitter arranged between the first transmitting surface and the second transmitting surface,   wherein when the transparent substrate is seen from the light source side, the spatial phase modulator and the splitter are arranged side by side.   
     
     
         14 . A display apparatus according to  claim 13 , further comprising another spatial phase modulator arranged in an optical path from the light source to the spatial phase modulator. 
     
     
         15 . A display apparatus according to  claim 13 , wherein the light source is in contact with the first transmitting surface. 
     
     
         16 . A display apparatus according to  claim 13 , further comprising a lens arranged in an optical path from the light source to the spatial phase modulator. 
     
     
         17 . A display method comprising:
 causing a display beam to be reflected;   amplitude-splitting the reflected display beam, thereby producing a beam travelling in the direction same as the travelling direction of the reflected display beam and a beam travelling in a direction different from the travelling direction of the reflected display beam; and   performing the reflecting and the amplitude-splitting repeatedly,   wherein the display beam is a beam produced by diffraction.