Patent ID: 7270463

Claim:
An area light source device comprising: an L-shaped light source; a wedge-shaped light guide having an incidence surface, on which emission light from the light source is incident, and an emission surface from which incident light that is incident from the incidence surface is emitted; an optical sheet that is disposed on the emission surface; and a reflector that surrounds the light source, has an opening facing the incidence surface, and reflects the emission light from the light source toward the light guide, wherein the opening of the reflector has a shape corresponding to shapes of two mutually neighboring incidence surfaces of the wedge-shaped light guide, the incidence surface of the light guide includes a first incidence surface with a substantially uniform width, and a second incidence surface that neighbors the first incidence surface and has a width decreasing from one end to the other end thereof, and the opening of the reflector includes a first opening portion that corresponds to the first incidence surface and has a substantially uniform opening width, and a second opening portion that corresponds to the second incidence surface and has an opening width gradually decreasing from one end toward the other end thereof.