Light deflector and light source device

Abstract

A planar light source device has a primary light source (), a light guide () having a light incident surface () on which light emitted from the primary light source () is incident and a light emitting surface () for emitting light guided in the light guide, and a light deflector () opposed to the light emitting surface of the light guide. The light deflector () has a light input surface () to which light is inputted and a light output surface () which is disposed on the opposite side of the light input surface and outputs the inputted light. Elongated prisms each having two prism faces are arranged in parallel to each other on the light input surface (). At least one of the two prism faces is a non-single planar surface. The vertex split angle α of one of the prism faces is 2 to 25 degrees, and the vertex split angle β of the other prism face is 33 to 40 degrees. The difference (|α−β|) between the vertex split angle α and the vertex split angle β is 8 to 35 degrees. As a result, the output light distribution is controlled and narrowed. Thus, a light source device having an improved ratio of utilization of the amount of light from the primary light source, a simplified structure, and an improved image definition is produced.