Patent ID: 8174679

Claim:
An illumination optical system which illuminates a surface to be illuminated with light from a light source, the illumination optical system comprising: a plurality of illumination systems configured to form predetermined illumination regions with the light from the light source; an optical system having reflecting surfaces, which are configured to reflect the light beams from said illumination systems, respectively for said plurality of illumination systems; and a light-shielding unit configured to shield a certain light component in a composite illumination region formed by the light from said optical system to shape a shape of the composite illumination region, wherein the light beams from said plurality of illumination systems are reflected by said reflecting surfaces, illuminate different positions on an opening of said light-shielding unit, and one continuous composite illumination region is formed by connecting the respective illumination regions, and wherein the surface to be illuminated is illuminated with the light beam which has passed through said light-shielding unit.