ILLUMINATION SYSTEM FOR A MICROLITHOGRAPHIC PROJECTION ILLUMINATION INSTALLATION

摘要

The invention relates to an illumination system (1) for a microlithographic projection illumination installation. Said illumination system is configured to illuminate an illumination field with an illumination radiation having a defined degree of coherency sigma , said degree of coherency being adjustable within a coherency degree range that reaches the range of very low coherency degrees substantially below sigma =0.2. The illumination system comprises a first optical system (30) for producing a defined light distribution in an entry plane of a light mixing device and a light mixing device (12) for homogenizing the incident radiation. The first optical system and the light mixing device can be adjusted between a plurality of configurations that correspond to different coherency degree ranges. The coherency degree ranges overlap and are calculated in such a manner that the resulting total coherency degree range is larger than the individual coherency degree ranges.