Illuminating optical apparatus, exposure apparatus and device manufacturing method

摘要

An illumination optical apparatus is able to quickly perform switching of illumination conditions between illumination in a first region and illumination in a second region. The illumination optical apparatus of the present invention to illuminate an illumination target surface on the basis of light from a light source comprises: a path switching member arranged in an optical path between the light source and the illumination target surface and switching an optical path of an exiting beam between a first optical path and a second optical path; a path combining member combining the first optical path and the second optical path; a first pupil distribution forming member arranged in the first optical path and forming a predetermined light intensity distribution on an illumination pupil; and a second pupil distribution forming member arranged in the second optical path and forming a predetermined light intensity distribution on the illumination pupil.