SYSTEM AND METHOD FOR MIXING AND GUIDING LIGHT EMITTED FROM LIGHT EMITTING DIODES TO A LIGHT PIPE FOR EMISSION IN A LINEAR CONFIGURATION
A linear light module having an optical coupling element and a light pipe is described. The optical coupling element receives light emitted by multiple light emitting diodes (LEDs) having different emission wavelengths and couples the light efficiently to a linear light pipe. The light from the LEDs is efficiently mixed by the optical coupling element and the light pipe to produce a linear light output that is uniform in color and intensity. Diffusers can be used with the optical coupling element and light pipe at various locations to further enhance the uniformity of the emitted light.
1 . An optical element comprising:
a light transmissible body;
an input surface of the light transmissible body configured to receive light emitted by a plurality of light emitting elements;
a plurality of intermediate surfaces of the light transmissible body configured to couple the input surface to an output surface of the light transmissible body,
wherein the plurality of intermediate surfaces are configured to reflect a substantial amount of the received light through total internal reflection (TIR) within the light transmissible body to exit the light transmissible body through an output surface opposite the input surface, and
further wherein light exiting the output surface meets an exit angle criteria such that the exiting light is within a predefined range of exit angles with respect to a normal to the output surface;
the output surface of the light transmissible body is configured to meet a predefined aperture criteria.
2 . The optical element of claim 1 , wherein the optical element is symmetric along two axes, wherein the two axes are perpendicular to a direction normal to the output surface.
3 . The optical element of claim 1 , wherein one or more of the plurality of intermediate surfaces have a substantially paraboloid curvature.
4 . The optical element of claim 1 , wherein the light emitting elements are light emitting diodes, and further wherein the input surface includes one or more concave inward cavities.
5 . The optical element of claim 4 , wherein the one or more concave inward cavities each receive a single light emitting diode, and further wherein a coupling material is used between the light emitting diodes and the one or more cavities.
6 . The optical element of claim 4 , wherein the one or more concave inward cavities each receive a plurality of light emitting diodes, and further wherein a coupling material is used between the light emitting diodes and the one or more cavities.
7 . The optical element of claim 1 , further comprising a plurality of reflective surfaces positioned adjacent to the plurality of intermediate surfaces to reflect light that exits the light transmissible body through at least one of the plurality of intermediate surfaces back into the light transmissible body, wherein an air gap is between the plurality of reflective surfaces and the plurality of intermediate surfaces.
8 . The optical element of claim 1 , wherein the predefined range of exit angles is specified so that the exiting light is substantially totally internally reflected within a light guide directly coupled to the output surface until the light is emitted along an emission surface of the light guide substantially perpendicular to the output surface of the optical element.
9 . The optical element of claim 8 , wherein the light guide extends substantially perpendicular to the output surface and has a substantially rectangular solid shape.
10 . The optical element of claim 8 , wherein the light guide extends substantially perpendicular to the output surface and has a bottom surface opposite the emission surface that is tapered toward the output surface.
11 . The optical element of claim 8 , wherein the light guide extends substantially perpendicular to the output surface and has a bottom surface opposite the emission surface that is a step surface that rises toward the output surface.
12 . The optical element of claim 8 , wherein a scattering element is positioned beneath at least a portion of a bottom surface of the light guide opposite the emission surface, wherein an air gap is between the scattering element and the bottom surface.
13 . The optical element of claim 1 , wherein a light extraction element is coupled to at least one of the intermediate surfaces to cause light to fail to meet a TIR condition and to exit from the optical element at the light extraction element.
14 . A light guide comprising:
a light transmissible body;
an input surface of the light transmissible body configured to receive light from an optical coupling element configured to couple light from a plurality of light emitting elements, wherein a substantial amount of the received light is within a range of angles that is totally internally reflected upon striking an inner surface of the light transmissible body;
an emission surface of the light transmissible body configured to emit light that strikes the emission surface and does not meet a total internal reflection (TIR) condition, wherein the emission surface has a linear configuration, is substantially perpendicular to the input surface, and is cantilevered over the optical coupling element;
a plurality of side surfaces of the light transmissible body configured to reflect light within the light transmissible body by TIR if the light meets the TIR condition;
a plurality of reflective surfaces adjacent to at least some of the plurality of side surfaces, separated by an air gap from the at least some of the plurality of side surfaces, and configured to reflect light that exits the at least some of the plurality of side surfaces.
15 . The light guide of claim 14 , wherein a bottom surface opposite the emission surface has an undulating curvature to scatter the received light.
16 . The light guide of claim 14 , wherein one or more scattering elements are positioned adjacent to at least a portion of a bottom surface of the light guide opposite the emission surface, and wherein an air gap is between the one or more scattering elements and the bottom surface.
17 . The light guide of claim 16 , wherein the one or more scattering elements comprise a brightness enhancement film.
18 . The light guide of claim 17 , wherein the one or more scattering elements are angled at two or more orientations.
19 . The light guide of claim 16 , wherein the one or more scattering elements are a diffusive material covering the entire bottom surface.
20 . The light guide of claim 16 , wherein the one or more scattering elements are a diffusive material covering at least a portion of the bottom surface in a uniform pattern.
21 . The light guide of claim 16 , wherein the one or more scattering elements are a diffusive material covering at least a portion of the bottom surface in a non-uniform pattern.
22 . The light guide of claim 16 , wherein the bottom surface is substantially parallel to the emission surface.
23 . The light guide of claim 16 , wherein the bottom surface is tapered toward the emission surface.
24 . The light guide of claim 16 , wherein the bottom surface is a step surface that rises toward the output surface.
25 . The light guide of claim 14 , wherein a bottom surface opposite the emission surface curves upward.
26 . The light guide of claim 25 , wherein the bottom surface has saw-tooth features.
27 . The light guide of claim 26 , wherein the saw-tooth features vary in amplitude.
28 . The light guide of claim 27 , wherein an amplitude of each of the saw-tooth features decreases monotonically from a close end of the emission surface near the optical coupling element to a far end of the emission surface.
29 . The light guide of claim 14 , further comprising a diffuser between the input surface of the light transmissible body and the optical coupling element.
30 . The light guide of claim 14 , wherein a bridge portion of the light transmissible body cantilevered over the optical coupling element is separated from the optical coupling element by an air gap, and the light guide further comprises a light extraction element coupled to a top surface of the optical coupling element closest to the bridge portion of the light transmissible body.
31 . The light guide of claim 14 , wherein the plurality of light emitting elements comprise a plurality of light emitting diodes (LEDs) arranged in an array, wherein the plurality of LEDs are selected to emit a plurality of colors to collectively generate a particular correlated color temperature (CCT), and further wherein a relative placement of LEDs within the array is based on a position of each of the plurality of colors on a CIE (International Commission on Illumination) color diagram.
32 . The light guide of claim 31 , wherein the array comprises rows of pairs of LEDs, and further wherein each pair of LED is selected to comprise a first LED located across a Planckian curve on the CIE color diagram from a second LED.
33 . A lighting system comprised of two light guides of claim 14 , wherein the emission surface of the two light guides are aligned to form a straight composite emission surface, and further wherein the optical coupling element of each light guide is positioned near the ends of the light system.
34 . The lighting system of claim 33 , further comprising an output reflector, wherein the output of the emission surface is reflected from the output reflector.
35 . The lighting system of claim 33 , further comprising an output diffuser, wherein the output of the emission surface is transmitted through the output diffuser.