Patent ID: 6874902

Claim:
A light source device comprising: a primary light source; a light guide having a light incident face on which light emitted from said primary light source is incident, guiding the incident light, and having a light emission face from which the incident light is emitted; and a light deflecting device disposed so as to be adjacent to the light emission face of said light guide, wherein said light deflecting device has a light incident surface disposed so as to face the light emission face of said light guide and a light emission surface at an opposite side to the light incident surface, plural elongated prisms arranged in parallel to one another are formed on the light incident surface of said light deflecting device, each of the elongated prisms has two prism faces, and at least a prism face of each of said elongated prisms at a far side from said primary light source is designed to have a convex surface shape set to such a condition that a ratio (r/P) of a radius of curvature r of the convex-surface-shaped prism face to an arrangement pitch P of said elongated prisms is equal to 7 to 30.