Slim waveguide coupling apparatus and method
In various embodiments, an illumination structure includes a discrete light source disposed proximate a bottom surface of a waveguide and below a depression in a top surface thereof. A top mirror may be disposed above the discrete light source to convert modes of light emitted from the discrete light source into trapped modes, thereby increasing the coupling efficiency of the illumination structure.
1. An illumination device comprising:
a waveguide having (i) top and bottom opposed surfaces, (ii) an in-coupling region for receiving light, (iii) an out-coupling region for emitting light from the waveguide, (iv) a depression defined in the top surface thereof, and (v) a recess defined in the bottom surface thereof;
one or more discrete light sources disposed at least partially within the recess and positioned to emit light into the in-coupling region;
an index-matching material disposed around the one or more discrete light sources within the recess; and
a reflector disposed over the depression.
2. The illumination device of claim 1 , wherein the reflector comprises at least one of a flat mirror, a specular mirror, a diffusive reflector, a Fresnel reflector, or a diffractive optical element.
3. The illumination device of claim 1 , wherein the depression is empty.
4. The illumination device of claim 1 , wherein the waveguide comprises a side surface spanning the top and bottom surfaces, the side surface being reflective to light emitted by the one or more discrete light sources.
5. The illumination device of claim 1 , wherein the depression is positioned directly above the recess.
6. The illumination device of claim 1 , wherein the out-coupling region comprises a portion of the top surface of the waveguide.
7. The illumination device of claim 6 , wherein the portion of the top surface of the waveguide in the out-coupling region is substantially planar.
8. The illumination device of claim 1 , further comprising a phosphor for converting light emitted by at least one of the one or more discrete light sources to light of a different wavelength.
9. The illumination device of claim 1 , wherein an index of refraction of the index-matching material is substantially equal to an index of refraction of the waveguide.
10. The illumination device of claim 1 , wherein the index-matching material is adhesive.
11. The illumination device of claim 1 , wherein an index of refraction of the index-matching material is less than an index of refraction of the waveguide.
12. The illumination device of claim 1 , wherein the index-matching material comprises silicone.
13. The illumination device of claim 1 , wherein the one or more discrete light sources comprises at least three discrete light sources.
14. The illumination device of claim 1 , wherein the one or more discrete light sources comprises at least four discrete light sources.
15. The illumination device of claim 1 , wherein (i) the one or more discrete light sources comprises a plurality of discrete light sources, and (ii) at least two of the discrete light sources emit light of substantially the same wavelength.
16. The illumination device of claim 1 , wherein (i) the one or more discrete light sources comprises a plurality of discrete light sources, and (ii) at least two of the discrete light sources emit light of different wavelengths.
17. The illumination device of claim 1 , wherein a thickness of the waveguide spanning the top and bottom surfaces is greater than a width of at least one said discrete light source.
18. The illumination device of claim 17 , wherein the thickness of the waveguide is at least as thick as a sum of the width of at least one said discrete light source and a thickness of at least one said discrete light source.
19. The illumination device of claim 1 , wherein at least a portion of the bottom surface of the waveguide comprises a reflective coating thereon.