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. A method of illumination using a waveguide having (i) an in-coupling region for receiving light and (ii) an out-coupling region for emitting light from the waveguide, the method comprising:
emitting light into the in-coupling region of the waveguide;
converting a wavelength of at least a portion of the light to a different wavelength;
reflecting, from a depression in a surface of the waveguide, a first portion of the light into the waveguide;
transmitting a second portion of the light through the depression;
preventing emission of the second portion of the light from of the waveguide proximate the depression; and
emitting at least some of the first portion of the light and/or at least some of the second portion of the light from the out-coupling region of the waveguide.
2. The method of claim 1 , wherein the light is emitted into the in-coupling region of the waveguide by one or more light-emitting diodes.
3. The method of claim 2 , wherein the depression is disposed above at least one of the light-emitting diodes.
4. The method of claim 2 , wherein the out-coupling region and the one or more light-emitting diodes are disposed at opposite surfaces of the waveguide.
5. The method of claim 2 , further comprising reflecting, from a surface of the waveguide proximate at least one of the light-emitting diodes, light into the waveguide.
6. The method of claim 2 , wherein a thickness of the waveguide is greater than a width of at least one of the light-emitting diodes.
7. The method of claim 6 , wherein the thickness of the waveguide is at least as thick as a sum of the width of at least one of the light-emitting diodes and a thickness of at least one of the light-emitting diodes.
8. The method of claim 2 , wherein the one or more light-emitting diodes comprises at least three light-emitting diodes.
9. The method of claim 2 , wherein the one or more light-emitting diodes comprises at least four light-emitting diodes.
10. The method of claim 1 , wherein emission of the second portion of the light is prevented by at least one of a mirror or an absorber.
11. The method of claim 1 , wherein the wavelength of the at least a portion of the light is converted to a different wavelength by a phosphor.
12. The method of claim 11 , wherein the phosphor is disposed within the in-coupling region of the waveguide.
13. The method of claim 1 , wherein the first portion of the light is reflected into the waveguide by a mirror disposed over and/or at least partially within the depression.
14. The method of claim 1 , wherein at least a portion of the light emitted into the in-coupling region of the waveguide is emitted by a light-emitting diode disposed at least partially within a recessed notch defined by the waveguide.
15. The method of claim 1 , wherein an index-matching material is disposed outside of the waveguide proximate the depression.
16. The method of claim 15 , wherein an index of refraction of the index-matching material is substantially equal to an index of refraction of the waveguide.
17. The method of claim 15 , wherein the index-matching material is adhesive.
18. The method of claim 15 , wherein an index of refraction of the index-matching material is less than an index of refraction of the waveguide.
19. The method of claim 15 , wherein the index-matching material comprises silicone.