US Patent 7808732 Light source apparatus

A conventional light source apparatus that combines incident light from a plurality of light sources by using prism sheets has the problem that the beam aspect ratio of incident light is undesirably changed so that exiting light has an extremely elliptical beam profile. The present invention provides a light source apparatus emitting light of circular beam profile having the same beam aspect ratio as that of incident light. The apparatus includes a plurality of light sources K and a plurality of prism sheets PS1 and PS2 each having a plurality of fine prisms on one surface thereof. The other surface of each prism sheet is a plane surface. The prism sheets are arranged in first and second stages as first and second beam profile transforming units such that their respective prism rows extend perpendicular to each other. The light sources are disposed at the entrance surface side of the first beam profile transforming unit at a predetermined angle thereto.