Light guide for surface light source device and surface light source device

摘要

A high quality surface light source in which various kinds of unevenness in luminance due to use of small number of spot-like primary light sources for reducing power consumption is eliminated, and a light guide for use therein. The planar light guide (4) guides light emitted from a plurality of spot-like primary light sources (2) and has an incoming end face (41) of lights emitted from the primary light source (2) and an outgoing face (43) of guided light. A high light diffusion region (431) extends substantially along the direction of directivity of light entering the light guide (4) in a plane extending along the outgoing face (43), in the vicinity of the incoming end face of at least one of the outgoing face (43) and its rear surface (44) on the opposite side. The high light diffusion region (431) has a mean inclination angle larger than that of an adjacent region (434).