Waveguide sheet containing in-coupling, propagation, and out-coupling regions
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 one or more optical elements for at least one of in-coupling or out-coupling light, the illumination structure comprising:
a substantially non-fiber waveguide having an index of refraction and comprising:
a discrete in-coupling region for receiving light,
a discrete propagation region for retaining light therein and propagating light from the in-coupling region to an out-coupling region, light being retained within at least a portion of the propagation region via only total internal reflection at a boundary between the waveguide and air or a cladding material having an index of refraction lower than the index of refraction of the waveguide,
a discrete out-coupling region for emitting light, the in-coupling, propagation, and out-coupling regions being spatially distinct, light entering the in-coupling region being substantially retained within the waveguide for emission from the out-coupling region,
wherein light emitted from a surface of the waveguide in the out-coupling region has a predetermined optical profile comprising both (i) substantial uniformity of color profile and (ii) substantial uniformity of intensity.
2. The illumination structure of claim 1 , wherein the propagation region is substantially free of the one or more optical elements.
3. The illumination structure of claim 1 , wherein the one or more optical elements comprises at least one microlens.
4. The illumination structure of claim 1 , wherein the one or more optical elements comprises a plurality of photoluminescent particles.
5. The illumination structure of claim 1 , wherein the color profile comprises white light.
6. The illumination structure of claim 1 , 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.
7. The illumination structure of claim 6 , 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.
8. The illumination structure of claim 1 , wherein the out-coupling region comprises the one or more optical elements.
9. The illumination structure of claim 8 , wherein the one or more optical elements comprises a plurality of hemispheres.
10. The illumination structure of claim 9 , wherein the hemispheres have a concentration that varies across at least one dimension of the out-coupling region.
11. The illumination structure of claim 10 , wherein the concentration of the hemispheres increases with distance from the in-coupling region.
12. The illumination structure of claim 9 , wherein the hemispheres have a dimension that varies across at least one dimension of the out-coupling region.
13. The illumination structure of claim 9 , wherein the out-coupling region comprises a plurality of core structures, at least some of which comprise hemispheres, and wherein at least one of a size, a concentration, or a type of the hemispheres varies among at least two of the core structures.
14. The illumination structure of claim 9 , wherein the in-coupling region comprises a microlens.
15. The illumination structure of claim 1 , further comprising a light emitter disposed proximate the in-coupling region.
16. The illumination structure of claim 1 , further comprising a light emitter disposed within the waveguide.
17. The illumination structure of claim 16 , wherein the light emitter consists essentially of a bare-die light-emitting diode.
18. The illumination structure of claim 1 , further comprising a reflector disposed proximate a surface of the in-coupling region.
19. The illumination structure of claim 1 , wherein the waveguide is substantially planar.
20. The illumination structure of claim 1 , wherein an optical mean free path of light in the propagation region is substantially constant, and an optical mean free path of light in the out-coupling region varies substantially monotonically.
21. The illumination structure of claim 1 , 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.
22. The illumination structure of claim 1 , further comprising a photoluminescent layer disposed on a light-emitting surface of the out-coupling region.
23. The illumination structure of claim 22 , further comprising a light emitter proximate the in-coupling region, the light emitter having substantially no direct line-of-sight to the photoluminescent layer.
24. The illumination structure of claim 22 , further comprising a light emitter proximate the in-coupling region, the light emitter having a direct line-of-sight to the photoluminescent layer.