Abstract text

An illumination optical system is one for illuminating a surface to be illuminated with light from a light source, which has a distribution forming optical system including an optical integrator and forming a pupil intensity distribution on an illumination pupil located behind the optical integrator, and an optical attenuator arranged on a predetermined surface in an optical path behind the optical integrator and having an attenuation characteristic of varying an attenuation rate depending upon an angle of incidence to the predetermined surface.