Light Pipe with Directional Side-Light Extraction
A light pipe with directional side-light extraction comprises a light pipe and light-extraction structure applied to the light pipe over only a part of the cross-sectional perimeter of the light pipe and over an active section of the length of the light pipe in which directional side lighting is desired. The light-extraction structure comprises any of (i) material, other than a light-carrying portion of the light pipe or any fluoropolymer cladding on the light-carrying portion, including light-scattering material, (ii) surfaces treated to have light-scattering properties, and (iii) material with a reflective property. The foregoing light pipe eliminates the need for using a reflector, as with fluorescent lamps, by extracting the light only in the desired direction, towards a target area to be illuminated. Other embodiments of the invention promote uniformity in side light emission from a light pipe.
1 . A light pipe with directional side-light extraction, comprising:
a) a core;
b) light-extraction means applied to the core over only a part of the cross-sectional perimeter of the core and over an active section in which directional side lighting is desired; and
c)
2 . The light pipe of claim 1 , wherein the active section comprises a fraction of the length of the light pipe.
3 . The light pipe of claim 1 , wherein the light pipe has a substantially circular cross section.
4 . The light pipe of claim 1 , wherein the lumen output as between inlet and outlet portions of the active section is within plus or minus 10 percent of the average value of each other.
5 . (canceled)
6 . The light pipe of claim 1 , wherein the light-extraction means is in the form of a single strip that varies in width over the active section of the light pipe
7 . The light pipe of claim 1 , wherein the light-extraction means is a strip that varies in thickness over the active section of the light pipe.
8 . The light pipe of claim 1 , wherein the light-extraction means is a single strip of material containing light-scattering additives whose density varies over the active section of the light pipe.
9 . The light pipe of claim 1 , wherein the light-extraction means comprises a plurality of separate shaped pieces arranged along the active section of the light pipe
10 . The light pipe of claim 9 , wherein the pieces are sized, composed and arranged in such a manner as to achieve a substantially uniform distribution of light from the side of the light pipe.
11 . The light pipe of claim 10 , wherein the pieces are arranged in a non-uniform manner.
12 . The light pipe of claim 10 , wherein the sizes of the pieces vary along the active section of the light pipe.
13 . The light pipe of claim 1 , wherein:
a) the core comprises a polymer core; and
b) the light-extraction means is formed from etching of the surface of the polymer core.
14 . The light pipe of claim 1 , wherein:
a) the core comprises a polymer core and a fluoropolymer cladding; and
b) the light-extraction means comprises a material inserted between the core and the cladding.
15 . The light pipe of claim 14 , wherein the material inserted between the core and the cladding comprises a light-scattering coating.
16 . The light pipe of claim 14 , wherein:
a) the core comprises an acrylic polymer; and
b) the material inserted between the core and the cladding comprises an organic-solvent based paint.
17 . The light pipe of claim 16 , wherein the paint is applied in discrete areas along the light pipe, with the discrete areas being spaced along the light pipe with a higher density the further the distance along the light pipe from an input light source.
18 . The light pipe of claim 1 , wherein:
a) the core comprises a polymer core which is free of a fluoropolymer cladding in the active section of the light pipe; and
b) the light-extraction means is formed from etching of the surface of the polymer core or a coating on the core.
19 . The light pipe of claim 18 , wherein the polymer core comprises an acrylic polymer.
20 . The light pipe of claim 1 , wherein a substantial section of the light pipe is free of light-extraction means so as to act as a conveyance of light between a light source and a section of the light pipe with light-extraction means.
21 . The light pipe of claim 1 , wherein:
a) the core comprise a polymer core; and
b) the light-extraction means comprises reflective material.
22 . The light pipe of claim 21 , wherein the light pipe comprises a fluoropolymer cladding over the core.
23 . The light pipe of claim 21 , wherein the light pipe is free of a fluoropolymer cladding over the core.