Substrate-Guided Holographic Diffuser

Abstract

A substrate-guided holographic diffuser has a light-guide section configured to in-couple light and transmit the light within itself via total internal reflection. It can also have a brightness enhancement section that recycles non-diffracted light within the light-guide section. A hologram section that receives light from the light-guide section has a holographic structure defining acceptance conditions and is positioned relative to the internally reflected light such that the internally reflected light meets the acceptance conditions of the holographic structure. The internally reflected light is out-coupled by the holographic structure as a projected image of light scattered from a diffuser.

1 . A substrate-guided holographic diffuser comprising:
 a light-guide plate;   a single holographic diffuser comprising a volumetric type hologram attached to a surface of the light-guide plate;   wherein the hologram comprises an adjusted diffraction efficiency over the surface of the light-guide plate;   wherein the adjusted diffraction efficiency comprises a length-wise diffraction efficiency gradient along the length of the hologram; and   wherein the length-wise diffraction efficiency of hologram was recorded by adjusting an intensity ratio for recording wave fronts while varying a combined intensity of recording light across a photo-material used for recording the hologram.   
     
     
         2 . The holographic diffuser of  claim 1  further comprising a light source. 
     
     
         3 . The holographic diffuser of  claim 2  wherein the light source comprises at least one LED or laser diode. 
     
     
         4 . The holographic diffuser of  claim 2  wherein the light source comprises multiple LEDs or laser diodes. 
     
     
         5 . The holographic diffuser of  claim 1  wherein the wave fronts comprise a collimated wave front and a diffused wave front. 
     
     
         6 . The holographic diffuser of  claim 2  where the light is coherent or not coherent. 
     
     
         7 . The holographic diffuser of  claim 1  wherein the light-guide plate is substantially transparent or entirely transparent. 
     
     
         8 . The holographic diffuser of  claim 1  wherein the hologram is recorded using multiple wavelengths of laser lights for multi-color backlighting. 
     
     
         9 . The holographic diffuser of  claim 2  wherein the light source is coupled to the holographic diffuser by fiber optics. 
     
     
         10 . The holographic diffuser of  claim 8  wherein the multiple wavelengths of laser lights comprise 447 nm (blue), 530 nm (green), and 627 nm (red). 
     
     
         11 . The holographic diffuser of  claim 9  wherein the light-guide plate and the coupling fiber optics comprise the same material. 
     
     
         12 . The holographic diffuser of  claim 2  wherein the light source provides collimated light to the light-guide plate. 
     
     
         13 . The holographic diffuser of  claim 1  wherein the light-guide plate comprises a thickness ranging from 0.3-0.6 mm. 
     
     
         14 . The holographic diffuser of  claim 1  wherein the holographic diffuser is flexible, bendable, or rigid. 
     
     
         15 . The holographic diffuser of  claim 1  wherein the holographic diffuser comprises a thickness of about 20 microns. 
     
     
         16 . The holographic diffuser of  claim 2  wherein the holographic diffuser is positioned on the face of the light-guide plate that faces the light or on the opposite face from the light. 
     
     
         17 . The holographic diffuser of  claim 1  further comprising an anti-reflective coating on a surface of the light-guide plate. 
     
     
         18 . The holographic diffuser of  claim 1  wherein the light-guide plate comprises glass, polycarbonate, acrylic, polyolefin, or mixtures thereof. 
     
     
         19 . The holographic diffuser of  claim 1  wherein the light-guide plate comprises a value of light transmission of about 92-96%. 
     
     
         20 . The holographic diffuser of  claim 1  wherein the light-guide plate comprises a brightness uniformity of at least about 15% across a surface of the holographic diffuser.