Planar white illumination apparatus
In one aspect, an illumination structure includes a substantially non-fiber waveguide, which itself includes a discrete in-coupling region for receiving light, a discrete propagation region for propagating light, and a discrete out-coupling region for emitting light.
1. An illumination structure comprising:
a waveguide having an output surface for the emission of light therethrough;
a discrete light source for emitting output light embedded in the waveguide; and
a phosphor material for converting some of the output light to a different wavelength, the converted light mixing with unconverted output light to form mixed light spectrally different from both the output light and the converted light,
wherein the discrete light source and the phosphor material are arranged in a geometry that prevents light reflecting from the phosphor material from propagating directly back to the discrete light source and being absorbed thereby.
2. The illumination structure of claim 1 , wherein the phosphor material is also disposed within the waveguide.
3. The illumination structure of claim 1 , wherein the discrete light source is embedded in the waveguide proximate an input surface opposite the output surface.
4. The illumination structure of claim 1 , wherein the discrete light source and the phosphor material are arranged in a geometry that prevents line-of-sight travel of light between the discrete light source and the phosphor material.
5. The illumination structure of claim 1 , wherein the output light comprises at least one of blue light or ultraviolet light.
6. The illumination structure of claim 1 , wherein the phosphor material is disposed sufficiently remotely from the discrete light source so as to be substantially unaffected by heat emitted by the discrete light source.
7. The illumination structure of claim 1 , wherein the discrete light source comprises a substantially unpackaged light-emitting diode die.
8. The illumination structure of claim 1 , wherein the output surface is substantially planar.
9. The illumination structure of claim 1 , wherein the phosphor material is disposed proximate the output surface.
10. The illumination structure of claim 1 , wherein the waveguide comprises:
a discrete in-coupling region for receiving the output light; and
for emitting the light, a discrete out-coupling region comprising the output surface, the waveguide retaining light propagating therein and directing light to the out-coupling region for output.
11. The illumination structure of claim 10 , wherein the phosphor material comprises a plurality of photoluminescent particles disposed within the out-coupling region.
12. The illumination structure of claim 11 , wherein a concentration of the photoluminescent particles is graded along a length of the out-coupling region.
13. The illumination structure of claim 10 , wherein the out-coupling region comprises therein one or more optical elements for out-coupling light.
14. The illumination structure of claim 13 , wherein the one or more optical elements comprise at least one microlens, at least one hemisphere, or at least one diffusive dot.
15. The illumination structure of claim 10 , wherein the waveguide comprises, disposed between the in-coupling region and the out-coupling region, a discrete propagation region substantially free of an optical element for scattering light.
16. The illumination structure of claim 15 , wherein the propagation region is shaped to block the direct line of sight between the discrete light source and the phosphor material.
17. The illumination structure of claim 15 , wherein an optical mean free path of light in the in-coupling region is different from an optical mean free path of light in the propagation region.
18. The illumination structure of claim 15 , wherein the optical mean free path of light in the in-coupling region is less than the optical mean free path of light in the propagation region.
19. The illumination structure of claim 15 , wherein the in-coupling region receives light entering in a first direction, the propagation region propagates light in a second direction perpendicular to the first direction, and the out-coupling region emits light in a third direction perpendicular to the second direction.
20. The illumination structure of claim 10 , further comprising a reflector proximate a surface of the out-coupling region.
21. The illumination structure of claim 10 , wherein the in-coupling region comprises at least one element for increasing a uniformity of distribution of light emitted toward the out-coupling region.
22. The illumination structure of claim 1 , wherein a quantum efficiency of the phosphor material is stable only up to a temperature of approximately 50° C.
23. The illumination structure of claim 1 , wherein the mixed light is substantially white.
24. The illumination structure of claim 1 , wherein the waveguide is rigid.