Patent ID: 8913227

Claim:
An illumination optical system which illuminates an illumination target surface with light from a light source, comprising: a distribution forming optical system having an optical integrator which has a plurality of optical surfaces, the plurality of optical surfaces being arrayed two-dimensionally on a plane intersecting with an optical path of the illumination optical system, the distribution forming optical system distributing a beam having passed through the optical integrator onto an illumination pupil of the illumination optical system; a condenser optical system arranged on an optical path of the beam traveling from the optical integrator to the illumination target surface, the condenser optical system superposing a plurality of beams from the plurality of optical surfaces on the illumination target surface: and a correction member arranged on a section of the optical path of the beam between the illumination pupil and the illumination target surface, the correction member changing an emission direction of the beam according to an incidence position of the beam.