Patent ID: 8616746

Claim:
An optical element comprising a plate-like light guiding section for guiding light in which: the light guiding section includes, on a surface of one side thereof, a prism section the cross-sectional shape of which is composed of a plurality of saw teeth placed on polygonal shapes having one common center for reflecting the light entered from the common center and guided by the light guiding section to change traveling directions of the light, wherein the protrusion angle of the saw teeth at positions away from the common center is larger than the protrusion angle of the saw teeth at positions near the common center so that the incident angle at which parallel light guided by the light guiding section enters reflective surfaces of the saw teeth at positions away from the common center is larger than the incident angle at which the parallel light guided by the light guiding section enters reflective surfaces of the saw teeth at positions near the common center, and wherein, the protrusion angle of the saw teeth is changed according to their positions in the polygonal shapes.