US Patent 7999916 Microlithographic projection exposure apparatus

A microlithographic projection exposure apparatus is disclosed. The apparatus can have an illumination system for generating projection light, an absorption filter which has a varying absorption coefficient distribution, and a mask which is illuminated by the projection light. The mask can contain regions that differ from one another by the orientation of structures contained in them and whose transmissivity depends on the polarization state of the incident projection light. The absorption coefficient distribution of the absorption filter is determined so as to compensate at least partially for the dependence of the transmissivity of the region on the polarization state of the incident projection light.