Projection illumination system

摘要

A projection illumination system with a plurality of optical components (29, 32) includes an interferometer arrangement (37) whose components are arranged outside a projection beam path (17) of the projection illumination system. Measurement radiation of the interferometer arrangement strikes a surface (35) of the optical component (29) to be measured under a large angle of incidence (α). Actuators (83, 87) of the projection illumination system can be actuated as a function of a measurement radiation intensity distribution detected using the interferometer arrangement in order to change imaging characteristics of the projection illumination system and to keep them stable in particular also with respect to drifting.