ILLUMINATION SYSTEM FOR A MICROLITHOGRAPHIC PROJECTION EXPOSURE APPARATUS

摘要

An illumination system for a microlithographic pro­jection exposure apparatus has a light source (14) emit­ting linearly polarized light that has a fixed polariza­tion direction (PDi). A polarization rotation unit (PRU, PRU', PRU '') is provided that is configured to rotate the polarization direction on demand by a rotational angle a ? 0⁰. This makes it possible to adapt the polarization direction to different masks (M) with minimal losses of the light intensity.