Patent ID: 8223318

Claim:
An illumination optical apparatus that illuminates a surface to be illuminated, comprising: an optical integrator arranged in an optical path of the illumination optical apparatus and including a plurality of wavefront division regions; a polarization changing member arranged in a beam path of the illumination optical apparatus and which changes a polarization state of at least one beam out of a beam incident to a first region in the plurality of wavefront division regions of the optical integrator and a beam incident to a second region in the plurality of wavefront division regions of the optical integrator; and a field stop arranged at or near a position optically conjugate with the surface to be illuminated and operated in a first mode or a second mode, wherein the field stop passes a first beam which passed through the first region in the plurality of wavefront division regions and shades a second beam which passed through the second region in the plurality of wavefront division regions in the first mode, and the field stop passes the second beam and shades the first beam in the second mode.