Light deflection element and light source apparatus using the same

摘要

A surface light source apparatus includes a primary light source ( 1 ), an optical guide ( 3 ) for guiding light emitted from the primary light source and having a light incoming surface ( 31 ) and a light outgoing surface ( 32 ), a light deflection element ( 4 ) arranged adjacent to the light outgoing surface of the optical guide and having a light incoming surface ( 41 ) and a light outgoing surface ( 42 ), and a light diffusion element ( 6 ) arranged adjacent to the light outgoing surface of the light deflection element. The light incoming surface ( 41 ) of the light deflection element has a plurality of prism strings arranged substantially parallel to each other and each having two prism surfaces. At least one of the prism surfaces of these prism strings has a prism surface consisting of at least two planes having different inclination angles. As the plane approaches the light going surface, the inclination becomes larger. The difference between the inclination angle of the plane nearest to the light outgoing surface and that of the plane farthest from the light outgoing surface is 15 degrees or below.