Patent ID: 8827532

Claim:
A lightguide comprising: a lightguiding layer comprising a first major surface, an opposing second major surface, and a side surface, the lightguiding layer receiving light from the side surface, the received light propagating within the lightguiding layer by total internal reflection from at least the first major surface; a structured surface facing the first major surface of the lightguiding layer and comprising: a first plurality of first optical structures, each first optical structure extracting light from the lightguiding layer by frustrating total internal reflection at the first major surface of the lightguiding layer; a second plurality of second optical structures, each second optical structure not frustrating total internal reflection at the first major surface of the lightguiding layer; and an optical coupling layer, each first optical structure frustrating total internal reflection at the first major surface by being optically coupled to the lightguiding layer by the optical coupling layer, each second optical structure not frustrating total internal reflection at the first major surface by not being optically coupled to the lightguiding layer by the optical coupling layer.