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;
a discrete light source for emitting output light; 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 is disposed within the waveguide and there is substantially no direct line of sight between the discrete light source and the phosphor material.
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 waveguide is shaped to prevent line-of-sight travel of light between the discrete light source and the phosphor material.
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 waveguide comprises a discrete in-coupling region for receiving the output light and a discrete out-coupling region for emitting the light, the waveguide retaining light propagating therein and directing light to the out-coupling region for output.
9. The illumination structure of claim 8 , wherein a surface of the out-coupling region is substantially planar.
10. The illumination structure of claim 9 , wherein the phosphor material is disposed proximate the surface of the out-coupling region.
11. The illumination structure of claim 8 , wherein the phosphor material comprises a plurality of photoluminescent particles disposed within the out-coupling region.
12. The illumination structure of claim 1 , wherein a concentration of the photoluminescent particles is graded along a length of the out-coupling region.
13. The illumination structure of claim 8 , wherein the waveguide comprises, disposed between the in-coupling region and the out-coupling region, a propagation region substantially free of scattering particles.
14. The illumination structure of claim 13 , wherein the propagation region is shaped to block the direct line of sight between the discrete light source and the phosphor material.
15. 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.
16. The illumination structure of claim 1 , wherein the mixed light is substantially white.
17. A method of producing substantially white light, the method comprising:
providing an illumination structure, the illumination structure comprising:
a waveguide,
means, disposed within the waveguide, for emitting output light, and
means for converting light to a different wavelength,
wherein there is no direct line of sight between the emitting means and the converting means; and
emitting output light from the emitting means,
wherein the converting means converts a portion of the output light to a different wavelength, the converted light mixes with unconverted output light to form the substantially white light, and the substantially white light is emitted from a surface of the waveguide.
18. The method of claim 17 , wherein the converting means is disposed within the waveguide.
19. The method of claim 17 , wherein the surface of the waveguide is substantially planar.
20. The method of claim 17 , wherein an operating temperature of the emitting means exceeds an operating temperature of the converting means by at least approximately 30° C.
21. The method of claim 17 , further comprising means, disposed within the waveguide, for out-coupling the light to be emitted from the surface of the waveguide.
22. The method of claim 21 , wherein output light is out-coupled by the out-coupling means before being converted by the converting means.
23. The illumination structure of claim 8 , wherein the out-coupling region comprises therein a plurality of optical elements for out-coupling light.
24. The illumination structure of claim 23 , wherein the optical elements comprise at least one of microlenses, hemispheres, or diffusive dots.