Illumination apparatus confining light by total internal reflection and methods of forming the same
In various embodiments, an illumination apparatus includes an air gap between a sub-assembly and a waveguide attached thereto at a plurality of discrete attachment points, as well as a bare-die light-emitting diode encapsulated by the waveguide.
1. An illumination device comprising:
a waveguide;
a sub-assembly attached to a first surface of the waveguide only at a plurality of discrete attachment points, an air gap separating the first surface of the waveguide and the sub-assembly between the plurality of discrete attachment points;
a light-emitting diode (LED) disposed over the sub-assembly and at least partially disposed within the waveguide, light emitted by the LED being in-coupled into the waveguide; and
a reflector disposed over at least a portion of a second surface of the waveguide to confine light within the waveguide.
2. The illumination device of claim 1 , wherein at least one of the discrete attachment points comprises a substantially rigid joining element for facilitating alignment of the waveguide with the sub-assembly.
3. The illumination device of claim 1 , further comprising, disposed over the LED, an in-coupling element for in-coupling light emitted by the LED into the waveguide.
4. The illumination device of claim 3 , wherein the in-coupling element comprises at least one of a reflector, a prism, or one or more scattering elements.
5. The illumination device of claim 1 , wherein the LED comprises a bare-die LED.
6. The illumination device of claim 1 , wherein the LED consists essentially of a bare-die LED.
7. The illumination device of claim 1 , further comprising a phosphor for converting a light emitted by the LED to light having a different wavelength.
8. The illumination device of claim 1 , wherein the second surface is opposite the first surface.
9. The illumination device of claim 1 , wherein the waveguide defines a recess in the first surface, and the LED is at least partially disposed within the recess.
10. The illumination device of claim 9 , further comprising at least one index-matching material filling at least a portion of the recess.
11. The illumination device of claim 10 , wherein a free surface of at least one said index-matching material in the recess is spaced away from the sub-assembly, thereby defining a second air gap between the sub-assembly and the free surface.
12. The illumination device of claim 11 , wherein the free surface of the at least one index-matching material is substantially parallel to the first surface of the waveguide.
13. The illumination device of claim 1 , wherein the sub-assembly comprises a metal-core printed circuit board.
14. The illumination device of claim 1 , wherein the waveguide comprises, opposite the first surface, an emission surface for emitting light in-coupled into the waveguide.
15. The illumination device of claim 14 , wherein the first surface and the emission surface are substantially planar.
16. The illumination device of claim 14 , wherein the waveguide comprises (i) an in-coupling region in which light emitted by the LED is in-coupled into the waveguide, and (ii) an out-coupling region, discrete from the in-coupling region, from which light is out-coupled through the emission surface.
17. The illumination device of claim 16 , wherein the out-coupling region is laterally spaced away from the LED.
18. The illumination device of claim 1 , wherein the waveguide comprises, adjoining and not parallel to the first surface, an emission surface for emitting light in-coupled into the waveguide.
19. The illumination device of claim 18 , wherein the first surface is substantially perpendicular to the emission surface.
20. The illumination device of claim 1 , wherein an air gap is disposed between the second surface of the waveguide and the reflector.