US Patent 7477458 Illumination optical system

An illumination optical system for illuminating an object with light from a light source device comprises a plurality of optical surfaces. At least one of the optical surfaces is formed as a roughened surface and is arranged in a position other than closest to the object. Assuming that a total quantity of light emitted to the object by the illumination optical system is L, and a total quantity of light is L0 emitted by a reference optical system in which all the roughened surfaces of the illumination optical system are replaced with polished surfaces, the illumination optical system satisfies the following condition:0.70≦X≦0.95,where X=L/L0.