Face-lit waveguide illumination systems
A face-lit waveguide illumination system employing a planar slab or plate of an optically transmissive material. A light source is optically coupled a linear optical element which is attached to a face of the waveguide and is configured to inject light at an angle permitting for light propagation by means of a total internal reflection. Light is propagated through the waveguide towards a predetermined direction in response to optical transmission and total internal reflection. Light extraction features located along the prevailing path of light propagation extract light from the waveguide and emit such light towards a surface perpendicular. In one embodiment, the planar waveguide includes a window pane which provides light transport from one location, where light is injected through the face of the pane, to another location where light is extracted. Additional embodiments of the face-lit waveguide illumination system are also disclosed.
1. A face-lit waveguide illumination system, comprising:
a portion of a light transmitting planar waveguide;
an elongated optical element attached to a major broad-area surface of said planar waveguide, said elongated optical element having a longer dimension that is much greater than the shorter dimensions and further having a first optically transparent surface facing said planar waveguide and an opposing second optically transparent surface facing away from said planar waveguide;
a plurality of light sources distributed along said longer dimension and optically coupled to said elongated optical element; and
one or more light extracting features configured for extracting light from said planar waveguide;
wherein said second optically transparent surface is configured for reflecting light by means of a total internal reflection, wherein said elongated optical element is configured for injecting light emitted by said light source into said planar waveguide at an angle permitting for propagating substantially all of the injected light in said planar waveguide by means of a total internal reflection; and wherein a transversal width of the optical contact area of said elongated optical element with said major broad-area surface is approximately equal to or less than 2d/√{square root over (n 2 −1)}, where d is the thickness of said planar waveguide and n is the refractive index of the medium of said planar waveguide.
2. An illumination system as recited in claim 1 , wherein each of said light sources comprises a light emitting diode.
3. An illumination system as recited in claim 1 , wherein said elongated optical element comprises an elongated collimating optical element extending parallel to said longer dimension and configured to collimate a light beam emitted by one or more of said light sources at least in a plane perpendicular to said longer dimension.
4. An illumination system as recited in claim 1 , wherein said elongated optical element comprises at least one mirrored face.
5. An illumination system as recited in claim 1 , wherein said elongated optical element is configured to guide light in response to optical transmission and a total internal reflection and couple substantially all of the light received onto a light input surface into said planar waveguide.
6. An illumination system as recited in claim 1 , wherein said elongated optical element comprises a block of an optically transparent material having the shape of a linear prism or wedge.
7. An illumination system as recited in claim 1 , wherein said elongated optical element is tapered in a plane perpendicular to said longer dimension.
8. An illumination system as recited in claim 1 , wherein said elongated optical element has at least one reflective surface having a curvilinear surface profile in a transversal cross-section.
9. An illumination system as recited in claim 1 , wherein said elongated optical element is formed by an optically transmissive film selected from the group of light turning films consisting of microstructured prismatic films, diffractive films, holographic films, and films with internal light redirecting structures.
10. An illumination system as recited in claim 1 , wherein a light input surface of said elongated optical element comprises an array of linear microprisms distributed over an area of said major broad-area surface.
11. An illumination system as recited in claim 1 , wherein a transversal width of said elongated optical element is less than two times the thickness of said planar waveguide.
12. An illumination system as recited in claim 1 , comprising an opaque light-blocking element configured for blocking stray light escaping from said elongated optical element and/or said planar waveguide in a light coupling area.
13. A face-lit waveguide illumination system, comprising:
a portion of a light transmitting planar waveguide;
a highly elongated optical element longitudinally extending between a first terminal end and a second terminal end and attached to a major broad-area surface of said planar waveguide at a distant location from edges defining said planar waveguide, said highly elongated optical element having a longer dimension that is much greater than the shorter dimensions and further having a first optically transparent surface facing said planar waveguide and an opposing second optically transparent surface facing away from said planar waveguide, said second optically transparent surface is configured for reflecting light by means of a total internal reflection;
at least one light source optically coupled to said first terminal end of the highly elongated optical element; and
one or more light extracting features configured for extracting light from said planar waveguide;
wherein said highly elongated optical element is configured for injecting light emitted by said light source into said planar waveguide at an angle permitting for propagating substantially all of the injected light in said planar waveguide by means of a total internal reflection; and wherein a transversal width of the optical contact area of said highly elongated optical element with said major broad-area surface is approximately equal to or less than 2d/√{square root over (n 2 −1)}, where d is the thickness of said planar waveguide and n is the refractive index of the medium of said planar waveguide.
14. An illumination system as recited in claim 13 , wherein said highly elongated optical element is tapered towards said second terminal end.
15. An illumination system as recited in claim 13 , wherein said highly elongated optical element has the shape of a rod or highly elongated bar.
16. An illumination system as recited in claim 13 , wherein said highly elongated optical element is configured to guide light along said longer dimension by means of a total internal reflection.