Light-Emitting Devices Providing Asymmetrical Propagation of Light

Abstract

A variety of light-emitting devices for general illumination utilizing solid state light sources (e.g., light emitting diodes) are disclosed. In general, the devices include a scattering element in combination with an extractor element. The scattering element, which may include elastic and/or inelastic scattering centers, is spaced apart from the light source element. Opposite sides of the scattering element have asymmetric optical interfaces, there being a larger refractive index mismatch at the interface facing the light emitting element than the interface between the scattering element and the extractor element. Such a structure favors forward scattering of light from the scattering element. In other words, the system favors scattering out of the scattering element into the extractor element over backscattering light towards the light source element. The extractor element, in turn, is sized and shaped to reduce reflection of light exiting the light-emitting device at the devices interface with the ambient environment.

1 . (canceled) 
     
     
         2 . A light-emitting device, comprising:
 a light-emitting element configured to provide light with a first intensity distribution;   a first optical element spaced apart from the light-emitting element, the first optical element comprising scattering centers configured to scatter light received by the first optical element from the light-emitting element;   a second optical element formed from a transparent material having a refractive index n2, the second optical element being in contact with the first optical element, there being an optical interface between the first and second optical elements at the place of contact, the second optical element having an exit surface, the second optical element being arranged to receive light from the first optical element through the optical interface and emit output light from the light-emitting device to an environment through the exit surface; and   a medium adjacent a surface of the first optical element, the medium having a refractive index n0 smaller than n2,   wherein light rays from the optical interface impinge directly on the exit surface at an incident angle relative to normal incidence that is less than a critical angle for total internal reflection, and   a combination of the first intensity distribution, a shape of the optical interface, a shape of the exit surface, and an arrangement of the optical interface relative to the exit surface is selected to provide a second intensity distribution to the output light emitted from the light-emitting device different from the first intensity distribution.   
     
     
         3 . The light-emitting device of  claim 2 , wherein the shape of the optical interface is a non-planar shape. 
     
     
         4 . The light emitting device of  claim 3 , wherein the non-planar shape is a non-spherical shape. 
     
     
         5 . The light-emitting device of  claim 3 , wherein the first optical element defines an enclosure into which light from the light-emitting element is emitted, wherein the enclosure is shaped such that at least some light from the light emitting element propagates through the enclosure directly to the first optical element. 
     
     
         6 . The light emitting device of  claim 5 , wherein every light ray from the optical interface impinges directly on the exit surface at an incident angle relative to normal incidence that is less than a critical angle for total internal reflection. 
     
     
         7 . The light-emitting device of  claim 5 , wherein the first optical element has an ellipsoidal shape. 
     
     
         8 . The light-emitting device of  claim 7 , wherein the ellipsoidal shape is prolate or oblate. 
     
     
         9 . The light-emitting device of  claim 8 , wherein the ellipsoidal shape is triaxial. 
     
     
         10 . The light-emitting device of  claim 5 , wherein the enclosure has an opening configured to receive the light-emitting element. 
     
     
         11 . The light-emitting device of  claim 10 , further comprising a reflector arranged within the opening, the reflector having a reflective surface facing the enclosure. 
     
     
         12 . The light-emitting device of  claim 3 , further comprising a reflector having a reflective surface, the reflective surface and a surface of the first optical element together defining an enclosure into which all light from the light-emitting element is emitted. 
     
     
         13 . The light-emitting device of  claim 12 , wherein the reflective surface is planar. 
     
     
         14 . The light-emitting device of  claim 12 , wherein the reflective surface is concave with respect to the enclosure. 
     
     
         15 . The light-emitting device of  claim 12 , wherein the surface of the first optical element includes concave portions with respect to the enclosure. 
     
     
         16 . The light-emitting device of  claim 12 , wherein the reflective surface comprises specular reflective portions. 
     
     
         17 . The light-emitting device of  claim 12 , wherein the reflective surface comprises diffuse reflective portions. 
     
     
         18 . The light-emitting device of  claim 12 , wherein the reflective surface is configured to direct light from the light-emitting element toward the first optical element. 
     
     
         19 . The light-emitting device of  claim 5 , wherein the medium is a gas. 
     
     
         20 . The light-emitting device of  claim 19 , wherein the gas is air. 
     
     
         21 . The light-emitting device of  claim 5 , wherein the first and second optical elements each have a corresponding axis of symmetry and the axis of the first optical element is collinear with the axis of the second optical element. 
     
     
         22 . The light-emitting device of  claim 5 , wherein the first optical element has a uniform thickness. 
     
     
         23 . The light-emitting device of  claim 5 , wherein the first optical element comprises a material having a first refractive index n1 equal to n2. 
     
     
         24 . The light-emitting device of  claim 22 , wherein n0=1. 
     
     
         25 . The light-emitting device of  claim 5 , wherein the light-emitting element is configured to emit blue light or ultraviolet light. 
     
     
         26 . The light-emitting device of  claim 5 , further comprising multiple additional light-emitting elements including a red light emitting element and a blue light-emitting element. 
     
     
         27 . The light-emitting device of  claim 5 , wherein the scattering centers comprise inelastic scattering centers configured to convert at least some light received from the light-emitting element to converted light having a longer wavelength than the light emitted from the light-emitting element. 
     
     
         28 . The light-emitting device of  claim 27 , wherein the converted light is yellow light. 
     
     
         29 . The light-emitting device of  claim 27 , wherein the inelastic scattering centers comprise a quantum dot phosphor. 
     
     
         30 . The light-emitting device of  claim 27 , wherein the scattering centers comprise elastic scattering centers.