Method of making light guide illumination systems with enhanced light coupling

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;
• providing a heat conductive substrate comprising a strip of printed circuit and a linear array of electrically interconnected side-emitting LED packages mounted to a major surface of the strip of 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;
• and
• positioning the heat conductive substrate at or near the first edge such that the strip of printed circuit is aligned parallel to the first edge, the light emitting aperture of each of the electrically interconnected side-emitting LED packages is facing the first edge, the major surface extends generally parallel to the first and second broad-area surfaces, and at least a substantial portion of the heat conductive substrate is located in a space between the first and second edges,
• 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.