ILLUMINATION SYSTEM FOR A MICROLITHOGRAPHY PROJECTION EXPOSURE APPARATUS AND PROJECTION EXPOSURE

摘要

An optical system (250) for altering radiation passing through from an entrance surface (261) to an exit surface (263) of the optical system is assigned a feedback device for feeding back the radiation led through the optical system in a first passage from the exit surface (263) to the entrance surface (261) of the optical system. The feedback device is set up such that the radiation altered by the optical system in a first passage passes through the optical system a second time in the same passage direction. The optical system may be incorporated in an illumination system for a microlithography projection exposure apparatus.