Patent ID: 7131735

Claim:
A light source device comprising: a light source array that emits light, the light source array having a plurality of light sources arranged in two directions in a plane; and a light guide including a first face; a second face; and at least two pair of flat, parallel reflecting side wall surfaces together forming a prismatic shape, the light guide being adapted to direct the light entering through the first face to a second face so as to output the light from the second face; the first face and the second face of the light guide being substantially a same size, and wherein said light guide is constructed to satisfy the formula L≧P/(tan θ), where L represents a length between the first face and the second face of the light guide, P represents an interval between the light sources which are adjacent to each other, and θ represents an angle with the optical axis at a position in which the intensity of light radiated by the light sources is half the intensity of light in the intensity distribution along the optical axis.