IMAGING OPTICAL SYSTEM AND PROJECTION EXPOSURE INSTALLATION FOR MICROLITHOGRAPHY WITH AN IMAGING OPTICAL SYSTEM OF THIS TYPE

摘要

An imaging optical system (7) has a plurality of mirrors (Ml to M6), which via a beam path for imaging light (3) image an object field (4) in an object plane (5) into an image field (8) in an image plane (9). The imaging optical system (7) has an exit pupil obscuration. At least one of the mirrors (Ml to M4) has no opening for passage of the imaging light (3). The fourth last mirror (M3) in the beam path is concave. Result is an imaging optical system having improved imaging properties without compromise in throughput.