Optical lens for extremely thin direct-lit backlight
Optical lens and light emitting device designs achieve uniform light distribution without producing a light “hot spot”, with a benefit of reducing the number of light sources needed and overall cost for direct-lit backlight device. The optical lens includes coating portions or structures on the bottom surface thereof, and a backlight device, or other light emitting device, incorporating said lens, to produce a uniform distribution of light at a target surface. The disclosed lens and light emitting device are particularly useful when an extremely wide transfer function of backlight is needed.
1. A light-emitting device, comprising:
a light source configured to emit light in an angular distribution that is substantially symmetric about an optical axis; and
a lens configured to redistribute the light emitted from the light source,
the lens including a concave inner surface that faces the light source,
the lens including a substantially planar surface that is substantially orthogonal to the optical axis and extends radially outward from a periphery of the concave inner surface,
the planar surface including a coated annular region on which a coating is disposed,
the coating configured to absorb at least a portion of the light inside the lens that strikes the coated annular region,
the planar surface further including an uncoated inner annular region between the coated annular region and the concave inner surface,
the planar surface further including an uncoated outer annular region between the coated annular region and an outer periphery of the planar surface,
the lens including an outer surface that faces away from the light source and adjoins the planar surface at the outer periphery of the planar surface,
the outer surface including a cylindrical portion positioned adjacent to the planar surface, such that all locations on the cylindrical portion are substantially equidistant from the optical axis.
2. The light-emitting device of claim 1 , wherein the outer surface includes a recessed portion centered at the optical axis that recesses inwardly toward the concave inner surface.
3. The light-emitting device of claim 1 , wherein the light source includes at least one light emitting diode.
4. The light-emitting device of claim 1 , wherein the concave inner surface is shaped to include, in part, at least one shape selected from an ellipsoid, a sphere, a paraboloid, and a continuous spline curve.
5. The light-emitting device of claim 2 , wherein the outer surface includes a convex portion extending between the cylindrical portion and the recessed portion.
6. The light-emitting device of claim 1 , wherein the lens includes at least one material selected from materials including polymethyl methacrylate, polyethylene terephthalate, polycarbonate, polystyrene, and glass.
7. The light-emitting device of claim 1 , wherein the coating is a black coating configured to absorb all colors of light that strikes the coating.
8. The light-emitting device of claim 1 , wherein the coating is a colored coating configured to reflect light of a first color that strikes the coating and absorb light of other colors that strikes the coating.
9. The light-emitting device of claim 1 , wherein the coating is an ink.
10. The light-emitting device of claim 1 , wherein the coating is a yellow coating configured to absorb bluish light and emit yellow light to produce white light inside the lens.
11. The light-emitting device of claim 1 , further comprising a screen backlight coupled to the light source and the lens.
12. The light-emitting device of claim 1 , wherein the light source includes an array of light emitting devices.
13. The light-emitting device of claim 1 , further comprising a diffuser plate positioned adjacent the outer surface of the optical lens.
14. The light-emitting device of claim 13 , wherein the diffuser plate includes a plurality of plastic sheets.
15. The light-emitting device of claim 1 , further comprising circuitry configured to power the light source.
16. The light-emitting device of claim 13 , wherein the diffuser plate is configured to eliminate bright spots in the light emitted from the light source.
17. The light-emitting device of claim 1 , wherein at least a portion of the planar surface is coated with a coating configured to absorb between about 10% and about 100% of light that strikes the coating.
18. A light-emitting device, comprising:
a light source having an emission surface, the emission surface defining an optical axis that extends substantially orthogonally from a center of the emission surface, the light source configured to emit light in an angular distribution that is substantially radially symmetric about the optical axis; and
a lens configured to:
receive the emitted light from the light source,
increase a uniformity of the emitted light to form redistributed light, and
direct the redistributed light away from the light source in an angular distribution that is radially symmetric about the optical axis,
the lens including a concave inner surface that faces the light source, the concave inner surface being substantially radially symmetric about the optical axis,
the lens including a substantially planar surface that is substantially orthogonal to the optical axis and extends radially outward from a periphery of the concave inner surface,
the planar surface including a coated annular region on which a coating is disposed,
the coating configured to absorb at least a portion of the light inside the lens that strikes the coated annular region,
the planar surface further including an uncoated inner annular region between the coated annular region and the concave inner surface,
the planar surface further including an uncoated outer annular region between the coated annular region and an outer periphery of the planar surface,
the lens including an outer surface that faces away from the light source and adjoins the planar surface at the outer periphery of the planar surface, the outer surface being substantially radially symmetric about the optical axis,
the outer surface including a cylindrical portion positioned adjacent to the planar surface, such that all locations on the cylindrical portion are substantially equidistant from the optical axis.
19. The light-emitting device of claim 18 , further comprising a diffuser plate positioned adjacent the outer surface of the lens.
20. A light-emitting device, comprising:
a lens configured to:
receive emitted light from a light source, the emitted light being substantially radially symmetric about an optical axis,
increase a uniformity of the emitted light to form redistributed light, and
direct the redistributed light away from the light source in an angular distribution that is substantially radially symmetric about the optical axis,
the lens including a concave inner surface configured to face the light source, the concave inner surface being substantially radially symmetric about the optical axis,
the lens including a substantially planar surface that is substantially orthogonal to the optical axis and extends radially outward from a periphery of the concave inner surface,
the planar surface including a coated annular region on which a coating is disposed,
the coating configured to absorb at least a portion of the light inside the lens that strikes the coated annular region,
the planar surface further including an uncoated inner annular region between the coated annular region and the concave inner surface,
the planar surface further including an uncoated outer annular region between the coated annular region and an outer periphery of the planar surface,
the lens including an outer surface configured to face away from the light source, the outer surface adjoining the planar surface at an outer periphery of the planar surface, the outer surface being substantially radially symmetric about the optical axis,
the outer surface including a cylindrical portion positioned adjacent to the planar surface, such that all locations on the cylindrical portion are substantially equidistant from the optical axis.