Holographic Waveguide Display with Light Control Layer

Abstract

Waveguides and waveguide displays having a layer for blocking non-image light (i.e. haze) that could otherwise reduce contrast and degrade color gamut and uniformity, while providing high transmission to external light are provided. Many waveguides and displays incorporate at least one light control layer applied to at least one external surface of said waveguide and overlapping at least a portion of said at least one grating, to divert or block scattered light from said set of gratings that might otherwise enter said eyebox.

What is claimed is: 
     
         1 . A waveguide display comprising:
 a waveguide supporting at least one grating;   a source of data modulated light;   a set of gratings configured to:
 direct said data modulated light into a total internal reflection path in said waveguide; and 
 provide beam expansion and extraction of data modulated light from said waveguide into an eyebox; and 
   at least one light control layer applied to at least one external surface of said waveguide and overlapping at least a portion of said at least one grating, wherein said light control layer is operative to divert or block scattered light from said set of gratings that might otherwise enter said eyebox.   
     
     
         2 . The apparatus of  claim 1 , wherein said set of gratings comprises at least one fold grating and at least one output grating, said fold grating directing said modulated light to said output grating and providing a first beam expansion, said output grating directing said modulated light out of said waveguide towards said eye box with beam expansion orthogonal to said first beam expansion. 
     
     
         3 . The apparatus of  claim 1 , wherein said set of gratings comprises an input coupler comprising at least one of a prism or a grating. 
     
     
         4 . The apparatus of  claim 1 , wherein said light control layer has at least one region having reflection characteristics dependent on at least one property of light incident on said region selected from the group of spectral bandwidth, incidence angle range, and polarization state. 
     
     
         5 . The apparatus of  claim 4 , wherein said light control layer region overlaps a fold grating. 
     
     
         6 . The apparatus of  claim 4 , said light control layer region overlaps an output grating. 
     
     
         7 . The apparatus of  claim 4 , wherein said light control layer has a reflection characteristic that varies spatially across said at least one region. 
     
     
         8 . The apparatus of  claim 1  wherein said at least one light control layer comprises at least one layer comprising at least one selected from the group of a narrow band interference filter, a dichroic filter, a reflection hologram, a micro louvre film, a birefringent film, a reflective polarizer, a polarization selective film, a film containing microparticles, a transparent substrate and an air space. 
     
     
         9 . The apparatus of  claim 1 , wherein said data modulated light is provided by one of a broadband light source, a laser emitter, a LED emitter or a module comprising one or more selected from the group of red, green and blue laser or LED emitters. 
     
     
         10 . The apparatus of  claim 1 , wherein said source of data modulated light comprises: a microdisplay for displaying image pixels and collimation optics and a lens for projecting the image displayed on said microdisplay panel such that each image pixel on said microdisplay is converted into a unique angular direction within said waveguide. 
     
     
         11 . The apparatus of  claim 1 , wherein said source of data modulated light is a laser projector comprising a beam scanning mechanism and a light modulator. 
     
     
         12 . The apparatus of  claim 1 , wherein at least one of said set of gratings is characterized by at least one of spatially varying pitch, rolled k-vectors, multiplexed gratings, and dual interaction gratings. 
     
     
         13 . The apparatus of  claim 1 , wherein at least one of said set of gratings is selected from the group of a switchable Bragg grating recorded in a holographic photopolymer a HPDLC material or a uniform modulation holographic liquid crystal polymer material and a surface relief grating. 
     
     
         14 . The apparatus of  claim 1 , wherein said set of gratings comprises:
 an input coupler;   an output coupler comprising multiplexed first and second gratings;   a first fold grating for directing light in a first spectral band along a first path from said input coupler to said output coupler and providing a first beam expansion; and   a second fold grating for directing light in a second spectral band along a second path from said input coupler to said output coupler and providing a first beam expansion, wherein:   said first multiplexed grating configured to direct said first spectral band out of said waveguide in a first direction with beam expansion orthogonal to said first beam expansion;   said second multiplexed grating configured to direct said second spectral band out of said waveguide in said first direction with beam expansion orthogonal to said first beam expansion;   said at least one light control layer comprises a first region having high reflectivity in at least one portion of said first spectral band and overlapping said first fold grating; and   said at least one light control layer further comprising a second region having high reflectivity in at least one portion of said second spectral band and overlapping said second fold grating.   
     
     
         15 . The apparatus of  claim 14 , wherein said first spectral band extends from blue to green and said first region has high reflectivity for blue and green light with spectral bandwidths substantially narrower than said first spectral band, wherein said second spectral band extends from green to red and said second region has high reflectivity for green and red light with spectral bandwidths substantially narrower than said second spectral band. 
     
     
         16 . The apparatus of  claim 14 , wherein said input coupler comprises at least one of a prism and a grating. 
     
     
         17 . The apparatus of  claim 14 , wherein said first and second fold grating and said multiplexed grating are formed in a single layer. 
     
     
         18 . The apparatus of  claim 17 , wherein said input coupler is a grating formed in said single layer. 
     
     
         19 . The apparatus of  claim 14 , wherein said at least one light control layer is formed by a stack of layers each containing a region providing reflection in spectral bandwidth substantially narrower than said first spectral band or said second band. 
     
     
         20 . The apparatus of  claim 14 , wherein said source of data modulated light is a laser projector and said light is provided by red, green, and blue laser emitters.