| CPC G02B 6/0065 (2013.01) [G02B 6/0016 (2013.01); G02B 6/0035 (2013.01); G02B 6/0073 (2013.01); G02B 6/0096 (2013.01); F21V 7/0091 (2013.01); F21V 2200/20 (2015.01); G02B 6/0015 (2013.01); G02B 6/0023 (2013.01); G02B 6/0025 (2013.01); G02B 6/0028 (2013.01); G02B 6/0031 (2013.01); G02B 6/0068 (2013.01); G02B 6/0075 (2013.01); G02B 6/0076 (2013.01); G02B 6/0095 (2013.01); G09F 13/049 (2021.05); G09F 13/18 (2013.01)] | 40 Claims |

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1. A method of making a light guide illumination system, comprising:
providing an optically transmissive sheet having a first broad-area surface substantially coextensive with a first side of the optically transmissive sheet, a second broad-area surface substantially coextensive with a second side of the optically transmissive sheet and extending parallel to the first broad-area surface, a first edge, an opposing second edge, a light coupling area located at or near the first edge, and a two-dimensional light extraction area located on at least one of the first and second broad-area surfaces and at a distance from the first edge, wherein the two-dimensional light extraction area comprises a plurality of light extraction features formed in or on one of the first and second broad-area surfaces with a variable density and configured for extracting light from the optically transmissive sheet, and wherein the optically transmissive sheet is configured to propagate light from the light coupling area towards the two-dimensional light extraction area using optical transmission and total internal reflection from both the first and second broad-area surfaces;
providing an LED strip comprising a strip of heat-conducting printed circuit and a linear array of electrically interconnected side-emitting LED packages mounted to a major surface of the strip of heat-conducting printed circuit such that a plane of a light emitting aperture of each of the electrically interconnected side-emitting LED packages is oriented perpendicular to the major surface;
providing a broad-area reflector;
positioning the broad-area reflector at the second broad-area surface parallel to the optically transmissive sheet;
aligning the LED strip parallel to the first edge; and
positioning the LED strip at or near the first edge such that the major surface extends generally parallel to the first and second broad-area surfaces and at least a substantial portion of the major surface is disposed in a space between the first and second edges,
wherein a density of the light extraction features within the two-dimensional light extraction area increases with a distance from the light coupling area.
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