Efficient collimation of light with optical wedge

Abstract

Embodiments of optical collimators are disclosed. For example, one disclosed embodiment comprises an optical waveguide having a first end, a second end opposing the first end, a viewing surface extending at least partially between the first end and the second end, and a back surface opposing the viewing surface. The viewing surface comprises a first critical angle of internal reflection, and the back surface is configured to be reflective at the first critical angle of internal reflection. Further, an end reflector is disposed at the second end of the optical waveguide, and includes a faceted lens structure to cause a majority of the viewing surface to be uniformly illuminated when uniform light is injected into the first end and also to cause a majority of the injected light to exit the viewing surface.

1 . An optical collimator comprising:
 an optical waveguide having
 a first end comprising a first light interface; 
 a second end opposite the first end; 
 a viewing surface comprising a second light interface extending at least partially between the first end and the second end and having a first critical angle of internal reflection with respect to a normal of the viewing surface; 
 a back surface opposing the viewing surface, the back surface being configured to be reflective to internally incident light at the first critical angle of internal reflection; and 
 an end reflector arranged at the second end of the optical waveguide, wherein the end reflector comprises a faceted lens structure comprising a plurality of facets angled to cause a majority of the viewing surface to be uniformly illuminated when uniform light is injected into a first end and also to cause a majority of the injected light to exit the viewing surface. 
   
     
     
         2 . The optical collimator of  claim 1 , wherein the first end of the optical waveguide is a thin end and the second end of the optical waveguide is a thick end. 
     
     
         3 . The optical collimator of  claim 1 , wherein the end reflector is spherically curved. 
     
     
         4 . The optical collimator of  claim 1 , wherein the plurality of facets of the faceted lens structure of the end reflector includes a plurality of facets facing the viewing surface and a plurality of facets facing the back surface, each facet facing the viewing surface being positioned adjacent to a facet facing the back surface. 
     
     
         5 . The optical collimator of  claim 4 , wherein each facet facing the viewing surface forms an angle relative to a normal of a surface of the end reflector of three-eighths of a difference between 90 degrees and the first critical angle. 
     
     
         6 . The optical collimator of  claim 4 , wherein each facet facing the back surface forms an angle relative to a normal of a surface of the end reflector equal to three-eighths of a difference between 90 degrees and the first critical angle. 
     
     
         7 . The optical collimator of  claim 4 , wherein each facet facing the viewing surface has a height of less than 500 microns and each facet facing the back surface has a height of less than 500 microns. 
     
     
         8 . The optical collimator of  claim 1 , wherein the back surface includes a second critical angle of internal reflection with respect to a normal of the reflective back surface, wherein the second critical angle of reflection is less than the first critical angle of reflection. 
     
     
         9 . The optical collimator of  claim 1 , wherein the viewing surface of the optical waveguide includes a cladding. 
     
     
         10 . The optical collimator of  claim 1 , wherein the back surface of the optical waveguide includes a cladding. 
     
     
         11 . The optical collimator of  claim 1 , wherein the back surface includes a mirror. 
     
     
         12 . The optical collimator of  claim 1 , wherein the optical waveguide further comprises a first reflective side and a second reflective side, the first reflective side opposite the second reflective side, each reflective side extending from the first end to the second end and from the viewing surface to the back surface. 
     
     
         13 . An optical collimator comprising:
 an optical wedge having
 a thin end comprising a first light interface; 
 a thick end opposite the thin end; 
 a viewing surface comprising a second light interface extending at least partially between the thin end and the thick end and having a first critical angle of internal reflection with respect to a normal of the viewing surface; 
 a back surface opposing the viewing surface and having a second critical angle of internal reflection with respect to a normal of the back surface, wherein the second critical angle of reflection is less than the first critical angle of reflection; and 
 an end reflector arranged at the thick end of the optical wedge, wherein the end reflector comprises a faceted lens structure comprising a plurality of facets arranged at an angle relative to a surface of the thick end, the plurality of facets alternating between facets facing the viewing surface and facets facing the back surface, and the facets having an angle relative to a normal of a surface of the end reflector of three-eighths of a difference of ninety degrees and the first critical angle. 
   
     
     
         14 . The optical collimator of  claim 13 , wherein the end reflector is spherically curved. 
     
     
         15 . The optical collimator of  claim 13 , wherein the end reflector of the optical wedge is cylindrically curved. 
     
     
         16 . The optical collimator of  claim 13 , wherein each facet facing the viewing surface includes a height of less than 500 microns and each facet facing the back surface includes a height of less than 500 microns. 
     
     
         17 . The optical collimator of  claim 13 , wherein the optical wedge further comprises a first reflective side and a second reflective side, the first reflective side opposite the second reflective side, each reflective side extending from the thin end to the thick end and from the viewing surface to the back surface. 
     
     
         18 . A method of collimating light via an optical waveguide, the optical waveguide comprising a first end, a second end opposite the first end and comprising an end reflector, a viewing surface extending between the first end and the second end, and a back surface opposing the viewing surface, the method comprising:
 injecting light into the first end of the optical waveguide;   delivering the light to the end reflector via total internal reflection;   internally reflecting the light off of the end reflector;   emitting a first portion of light from the viewing surface at a critical angle of reflection;   internally reflecting a second portion of light from the back surface at an angle equal to the critical angle of reflection, and then emitting the second portion of light from the viewing surface after internally reflecting the second portion of light from the back surface.   
     
     
         19 . The method of  claim 18 , wherein reflecting light off the end reflector comprises reflecting light from a first set of facets and a second set of facets, wherein each facet of the first set of facets comprises a normal that points at least partially toward the viewing surface, and wherein each facet of the second set of facets comprises a normal that points at least partially toward the back surface. 
     
     
         20 . The method of  claim 19 , wherein each of the first set of facets has an angle of three-eighths of a difference between 90 degrees and the critical angle of reflection and each of the second set of facets has an angle of three-eighths of the difference between 90 degrees and the critical angle of reflection.