Collimating illumination systems employing a waveguide

Abstract

An illumination system employing an elongated waveguide having a non-round transversal cross-section and having at least a portion of its surface shaped in the form of a linear collimating element. The waveguide further employs at least one array of light extracting features distributed along a longitudinal axis of the waveguide and disposed in the focal area of the respective linear collimating element. Each light extracting feature has an active aperture which is substantially less than the light receiving aperture of the linear collimating element and is configured to redirect light propagating in the waveguide generally towards a normal direction with respect to the longitudinal axis of the waveguide. Light rays redirected by the light extracting features are further collimated by the linear collimating element and exit from the waveguide in the form of a directional beam.

What is claimed is: 
     
       1. A collimating illumination system, comprising:
 a planar optical waveguide defined by a first major surface and an opposing second major surface extending parallel to said first major surface, said waveguide is configured for guiding light along a general propagation direction in response to optical transmission and a total internal reflection from at least one of said first and second major surfaces;   a plurality of linear collimating elements formed in said first major surface and aligned parallel to said general propagation direction; and   a plurality of light extraction elements arranged into a parallel array of linear strips, each of said strips extending parallel to said linear collimating elements and disposed near or at a focal area of at least one of said linear collimating elements;   wherein each of said strips of said light extraction elements is configured to receive light propagating within said planar optical waveguide along said general propagation direction and redirect at least a substantial portion of the received light toward said linear collimating elements and out of said waveguide;   wherein said waveguide is a lens array having a thickness T   
       
         
           
             
               
                 T 
                 = 
                 
                   nR 
                   
                     n 
                     - 
                     1 
                   
                 
               
               , 
             
           
         
       
       defined from the following expression: where R is a radius of curvature of lenses forming said lens array and n is the index of refraction of a material of said lens array. 
     
     
       2. A collimating illumination system as recited in  claim 1 , wherein said planar optical waveguide further comprises a cladding layer. 
     
     
       3. A collimating illumination system as recited in  claim 1 , further comprising a light source attached to a terminal end of said planar optical waveguide. 
     
     
       4. A collimating illumination system as recited in  claim 1 , wherein one of the terminal ends of said waveguide is mirrored. 
     
     
       5. A collimating illumination system as recited in  claim 1 , wherein said light extraction elements are disposed in a plurality of discrete locations within each of said strips, said locations being separated by spacing areas. 
     
     
       6. A collimating illumination system as recited in  claim 1 , wherein said light extraction elements are disposed in a plurality of discrete locations within each of said strips, said locations being separated by spacing areas of a variable width. 
     
     
       7. A collimating illumination system as recited in  claim 1 , wherein each of said light extraction elements comprises a cut or notch formed in a surface of said waveguide transversely to said general propagation direction. 
     
     
       8. A collimating illumination system as recited in  claim 1 , wherein each of said light extraction elements comprises at least one reflective surface inclined at an angle with respect to said general propagation direction. 
     
     
       9. A collimating illumination system as recited in  claim 1 , wherein each of said light extraction elements comprises at least one surface relief feature selected from the group of elements consisting of cavities, holes, extensions, bulges, prisms, prismatic grooves, pyramids, cones, conical cavities, pyramidal cavities, funnel-shaped cavities, surface texture, reflective surfaces, refractive surfaces, diffraction gratings, holograms, and light scattering elements. 
     
     
       10. A collimating illumination system as recited in  claim 1 , wherein each of said linear collimating elements is configured to intercept at least a substantial part of light rays extracted by one or more said light extraction elements and collimate said light rays at least in a plane perpendicular to said general propagation direction. 
     
     
       11. A collimating illumination system as recited in  claim 1 , wherein each of said linear collimating elements comprises a surface relief feature shaped in the form of an elongated structure having a transversal cross-section of a light-focusing or light-collimating optical element. 
     
     
       12. A collimating illumination system as recited in  claim 1 , wherein each of said linear collimating elements is selected from the group of optical elements consisting of imaging lenses, nonimaging lenses, spherical lenses, aspherical lenses, lens arrays, Fresnel lenses, TIR lenses, gradient index lenses, diffraction lenses, mirrors, Fresnel mirrors, spherical mirrors, parabolic mirrors, mirror arrays, and trough mirrors. 
     
     
       13. A collimating illumination system as recited in  claim 1 , wherein each of said linear collimating elements comprises a surface relief feature configured to reflect light rays by means of a total internal reflection when said rays propagate within said waveguide within a predefined angular range from a longitudinal axial direction of said linear collimating elements. 
     
     
       14. A collimating illumination system as recited in  claim 1 , wherein each of said linear collimating elements comprises at least two opposing reflective walls each disposed at a slanted angle with respect to a longitudinal axis of the collimating element and having a planar shape. 
     
     
       15. A collimating illumination system as recited in  claim 1 , wherein each of said linear collimating elements comprises at least two opposing reflective walls each disposed at a slanted angle with respect to a longitudinal axis of the collimating element and having a curved shape. 
     
     
       16. A collimating illumination system as recited in  claim 1 , wherein each of said linear collimating elements comprises a lenticular refractive lens. 
     
     
       17. An illumination system, comprising:
 a planar optical waveguide formed from an optically transmissive dielectric material and having a first major surface, an opposing second major surface extending parallel to said first major surface, a first edge configured for light input, and an opposing second edge extending parallel to the first edge;   a plurality of linear cylindrical lenses formed in said first major surface and oriented perpendicular to said first and second edges;   a light source comprising a plurality of light emitting diodes (LEDs) which are positioned proximate to said first edge and optically coupled to said planar optical waveguide;   a reflective surface approximately coextensive with the planar optical waveguide and facing said second major surface; and   a two-dimensional pattern of light extraction elements formed in or on said second major surface,   wherein each of said plurality of linear cylindrical lenses is configured to reflect light using a total internal reflection, wherein an area of each of said light extraction elements is less than an area of each of said plurality of linear cylindrical lenses, wherein a spacing distance between individual ones of said light extraction elements within said two-dimensional pattern generally decreases with a distance from the first edge, wherein each of said plurality of linear cylindrical lenses has a curved surface portion with an arcuate cross-sectional profile, and wherein a thickness of said planar optical waveguide is greater than EFL+R, where EFL is an effective focal length of the respective linear cylindrical lens and R is a radius of curvature of the arcuate cross-sectional profile.   
     
     
       18. An illumination system as recited in claim 17, wherein each of said light extraction elements is formed by a generally round cavity having curved walls and configured to reflectively redirect a first portion of light toward said linear cylindrical lenses and out of said planar optical waveguide and transmit a second portion of the light towards said reflective surface. 
     
     
       19. An illumination system as recited in claim 17, wherein each of said light extraction elements is formed by a generally round textured area of a reflective paint applied to said second major surface and comprises a two-dimensional pattern of light deflecting surface relief structures distributed over said generally round textured area. 
     
     
       20. An illumination system as recited in claim 17, wherein the light source is attached to a terminal end of the planar optical waveguide using an adhesive material. 
     
     
       21. An illumination system as recited in claim 17, wherein the thickness of said planar optical waveguide is at least three times said radius of curvature R. 
     
     
       22. An illumination system as recited in claim 17, wherein the thickness of said planar optical waveguide is at least three times said radius of curvature R, wherein a first one of said light extraction elements is positioned on an optical axis of an individual one of said plurality of linear lenses, and wherein a second one of said light extraction elements is positioned with a slight offset from the optical axis. 
     
     
       23. An illumination system as recited in claim 17, wherein the thickness of said planar optical waveguide is at least three times said radius of curvature R, wherein a first plurality of said light extraction elements is centered with respect to an optical axis of a first one of said plurality of linear cylindrical lenses, wherein a second plurality of said light extraction elements is centered with respect to an optical axis of a second one of said plurality of linear cylindrical lenses, and wherein a third plurality of said light extraction elements is centered with respect to an optical axis of a third one of said plurality of linear cylindrical lenses. 
     
     
       24. An illumination system as recited in claim 17, wherein at least one of the plurality of linear cylindrical lenses is flanked by planar portions of said first major surface that are parallel to said second major surface. 
     
     
       25. An illumination system, comprising:
 an array of linear cylindrical lenses disposed side by side and extending along generally straight lines that are parallel to one other, each of the linear cylindrical lenses having a curved surface portion with an arcuate cross-sectional profile which is configured to reflect light using a total internal reflection;   a plurality of light emitting diodes (LEDs) positioned proximate to terminal edges of the linear cylindrical lenses and optically coupled to the array; and   a plurality of light extraction elements distributed over an area of and optically coupled to the array,   wherein a thickness of the array is greater than EFL+R, where EFL is an effective focal length of the respective linear cylindrical lens and R is a radius of curvature of the arcuate cross-sectional profile.