A microlithography projection optical system is disclosed. The system can include a plurality of optical elements arranged to image radiation having a wavelength λ from an object field in an object plane to an image field in an image plane. The plurality of optical elements can have an entrance pupil located more than 2.8 m from the object plane. A path of radiation through the optical system can be characterized by chief rays having an angle of 3° or more with respect to the normal to the object plane. This can allow the use of phase shifting masks as objects to be imaged, in particular for EUV wavelengths.