Waveguide illumination system

Abstract

An illumination system employing a waveguide. Light received from an edge or an end of a waveguide is propagated in response to transmission and total internal reflection. Light deflecting elements distributed along the propagation path of light continuously change the out-of-plane propagation angle of light rays and cause decoupling of portions of the propagated light from the core of the waveguide at different distances from the light input edge or end. Light escapes from the waveguide into an intermediate layer at low out-of-plane angles and is further redirected by light extraction features out of the system. In one embodiment, the illumination system is configured to emit collimated light. In one embodiment, the illumination system includes shallow surface relief features. In one embodiment, the light deflecting elements include forward-scattering particles distributed throughout the volume of the waveguide. Additional collimating and non-collimating illumination units and methods are also disclosed.

What is claimed is: 
     
         1 . An illumination system, comprising:
 an optical waveguide having at least one major surface and configured to guide light towards at least one predetermined direction along said major surface in response to a total internal reflection;   a plurality of light deflecting elements distributed within said waveguide along said direction and configured to incrementally deflect light rays from said direction in at least one plane perpendicular to said major surface; and   light extracting means optically coupled to said major surface and configured for progressively extracting light from said waveguide in response to light incidence onto said major surface at an angle lower than the angle of a total internal reflection.   
     
     
         2 . An illumination system as recited in  claim 1 , wherein said waveguide has a planar configuration having two opposing broad-area surfaces extending parallel to each other. 
     
     
         3 . An illumination system as recited in  claim 1 , wherein said waveguide has a cylindrical configuration having a longitudinal dimension substantially greater than a transversal dimension. 
     
     
         4 . An illumination system as recited in  claim 1 , wherein said waveguide comprises at least one light input edge or end and further comprises at least one light source optically coupled to said at least one light input edge or end. 
     
     
         5 . An illumination system as recited in  claim 1 , further comprising at least one light emitting diode configured to inject light into said optical waveguide. 
     
     
         6 . An illumination system as recited in  claim 1 , further comprising at least one light source configured for inputting light into an edge or end of said optical waveguide, wherein said light source is selected from the group of elements consisting of light emitting diodes, compact fluorescent lamps, cold-cathode fluorescent lamps, halogen lamps, mercury-vapor lamps, sodium-vapor lamps, metal halide lamps, electroluminescent lamps, and lasers. 
     
     
         7 . An illumination system as recited in  claim 1  further comprising at least one light source and at least one collimating element associated with said at least one light source. 
     
     
         8 . An illumination system as recited in  claim 1 , further comprising a reflective layer adjacent to a major surface of said waveguide. 
     
     
         9 . An illumination system as recited in  claim 1 , wherein said light extracting means comprises an optical element selected from the group of elements consisting of light turning films, light scattering layers or surfaces, screens, image prints, and textured surfaces. 
     
     
         10 . An illumination system as recited in  claim 1 , wherein said light extracting means is configured to direct light generally towards a normal to said major surface. 
     
     
         11 . An illumination system as recited in  claim 1 , further comprising a buffer layer disposed between said optical waveguide and said light extracting means and having a lower refraction index than said optical waveguide. 
     
     
         12 . An illumination system as recited in  claim 1 , wherein each of said light redirecting elements comprises at least one surface relief feature. 
     
     
         13 . An illumination system as recited in  claim 1 , wherein each of said light redirecting elements is selected form the group of surface relief features having a relatively low aspect ratio and consisting of prisms, lenses, prismatic grooves, corrugations, undulations, depressions, indentations, recesses, protrusions, and extensions. 
     
     
         14 . An illumination system as recited in  claim 1 , wherein each of said light redirecting elements comprises a surface facet making a sufficiently low dihedral angle with respect to the prevailing plane of said optical waveguide, said dihedral angle being below a predetermined maximum angle. 
     
     
         15 . An illumination system of  claim 1  in a front light configuration, wherein said waveguide has the form of a planar panel and is made substantially transparent at least along a transversal direction with respect to a prevailing plane of said panel. 
     
     
         16 . An illumination system of  claim 1  in a backlight configuration, wherein said waveguide has the form of a planar panel. 
     
     
         17 . An illumination system of  claim 1  within day lighting device, wherein said system is configured for a generally unimpeded transversal light passage and is further configured to emit artificial light from a broad-area surface. 
     
     
         18 . An illumination system as recited in  claim 1 , wherein said system is configured for emitting at least a substantial part of the emitted light in the form of a collimated beam. 
     
     
         19 . An illumination system, comprising:
 a planar optical waveguide having a first broad-area surface and an opposing second broad-area surface extending generally parallel to said first broad-area surface;   a buffer layer of an optically transmissive material attached to said first surface, said buffer layer having a refractive index lower than the refractive index of said waveguide;   a plurality of light deflecting elements within said waveguide configured to extract light into said buffer layer; and   a light extracting layer attached to said buffer layer and configured to extract light from said buffer layer.   
     
     
         20 . A directional edge-lit lighting fixture, comprising:
 a planar sheet of an optically transmissive material configured to guide light along a predetermined direction in response to optical transmission and a total internal reflection;   at least one strip of light emitting diodes attached to an edge of said sheet; and   means for extracting light from a major surface of said sheet and for collimating the extracted light at least in a plane parallel to said predetermined direction;   whereby said directional edge-lit lighting fixture can emit light within a pre-defined angular range being substantially smaller than 180 degrees in said plane.