LIGHT CONFINEMENT USING DIFFUSERS
An illumination structure includes a waveguide, a discrete light source embedded within the waveguide, and a mode-conversion reflector. The mode-conversion reflector converts at least some unconfined modes from the light source into confined modes that propagate fully within the waveguide.
1 . An illumination structure comprising:
a waveguide;
a discrete light source embedded therein; and
a mode-conversion reflector for converting at least some unconfined modes from the light source into confined modes that propagate fully within the waveguide.
2 . The structure of claim 1 wherein the mode-conversion reflector is a diffuser.
3 . The structure of claim 1 wherein the discrete light source is a top-emitting LED.
4 . The structure of claim 1 wherein the waveguide comprises in-coupling, concentration, propagation, and out-coupling regions.
5 . The structure of claim 1 wherein the mode-conversion reflector is disposed on a surface of the waveguide opposite an emission region of the light source.
6 . The structure of claim 1 wherein about 75% of light emitted by the light source is retained within the waveguide.
7 . The structure of claim 5 further comprising a second mode-conversion reflector surrounding the light source.
8 . The structure of claim 7 wherein about 85% of light emitted by the light source is retained within the waveguide.
9 . The structure of claim 7 wherein the emission region has an area smaller than an area of the of the first mode-conversion reflector, and the area of the first mode-conversion reflector is smaller than an area of the second mode-conversion reflector.
10 . The structure of claim 1 the waveguide has an entrance aperture and the light source has an emitting area, the entrance aperture and the emitting area being approximately equal in size.
11 . The structure of claim 10 wherein the entrance aperture is surrounded by mode-conversion reflectors.
12 . An illumination structure comprising:
a waveguide having an entrance aperture;
a discrete light source having an emission area substantially conforming to the entrance aperture; and
one or more mode-conversion reflectors surrounding the entrance aperture.
13 . The structure of claim 12 wherein (i) the waveguide has a refractive index and (ii) the light source is attached to the waveguide by means of an adhesive having a refractive index substantially matching the refractive index of the waveguide.
14 . The structure of claim 12 wherein the emission area of the light source is attached to the entrance aperture of the waveguide through an anti-reflective coating.
15 . An illumination structure comprising:
a waveguide having an entrance aperture;
one or more mode-conversion reflectors surrounding the entrance aperture;
a discrete light source; and
an optical element for focusing light from the light source onto the entrance aperture.
16 . The structure of claim 15 wherein the optical element is a refractive lens.
17 . The structure of claim 15 wherein the optical element is a diffractive lens.
18 . The structure of claim 15 wherein the optical element is integral with the light source, the light source emitting light within a narrow light-distribution angle.
19 . The structure of claim 15 further comprising a mode-conversion reflector for converting at least some unconfined modes from the light source into confined modes that propagate fully within the waveguide, the mode-conversion reflector being disposed on a surface of the waveguide opposite an emission region of the light source.