Diffractive lighting devices with 3-dimensional appearance

Abstract

Extended area lighting devices include a light guide and diffractive surface features on a major surface of the light guide. The diffractive surface features provide low distortion for viewing objects through the light guide. Light from discrete light source(s) is injected into the light guide, and the diffractive surface features interact with the injected light to couple guided-mode light out of the light guide. The out-coupled light produces one or more bands whose apparent shape changes with viewing position. The bands may be bright bands that correspond to the discrete light sources, or dark bands associated with an optional non-uniform reflective structure extending along a side surface of the light guide. Multiple bands may form a pattern that changes with viewing position, the pattern of bands having a 3-dimensional appearance for at least some viewing positions. The lighting devices can be used as luminaires for general lighting or decorative lighting.

1 . A luminaire, comprising:
 a light guide having a first major surface and at least one side surface, the first major surface having diffractive surface features adapted to couple light out of the light guide;   a first light source disposed to inject light into the light guide;   a non-uniform reflective structure extending along the at least one side surface, the non-uniform reflective structure providing a first reflectivity along a major portion of the at least one side surface and a second reflectivity, different from the first reflectivity, at a localized region of the at least one side surface;   wherein at least some of the diffractive surface features are non-straight in plan view, and the light source, the diffractive surface features, and the reflective structure are tailored to produce a band that intersects the non-straight diffractive surface features.   
     
     
         2 . The luminaire of  claim 1 , wherein the first reflectivity is at least 50% for visible light, and the second reflectivity is less than the first reflectivity, such that the band is a dark band. 
     
     
         3 . The luminaire of  claim 2 , wherein the non-uniform reflective structure comprises a reflective material disposed on the major portion of the at least one side surface, the reflective material being absent from the localized region of the at least one side surface. 
     
     
         4 . The luminaire of  claim 1 , wherein the non-uniform reflective structure comprises a metal holder, and the second reflectivity at the localized region corresponds to a non-illuminated second light source carried by the metal holder. 
     
     
         5 . The luminaire of  claim 4 , wherein, in plan view, the light guide has a non-polygonal shape and the at least one side surface is curved and extends around a complete perimeter of the light guide. 
     
     
         6 . The luminaire of  claim 1 , wherein the localized region is one of a plurality of localized regions that are spaced-apart from each other and that have reflectivities less than the first reflectivity, and wherein the band is one of a plurality of dark bands corresponding to the plurality of localized regions, each of the dark bands intersecting the non-straight diffractive surface features. 
     
     
         7 . The luminaire of  claim 6 , wherein the plurality of dark bands forms a pattern that changes as a function of an observer's viewing position relative to the luminaire, the pattern of dark bands having a 3-dimensional appearance for at least some of the viewing positions.