An optical imaging system for inspection microscopes with which lithography masks can be checked for defects particularly through emulation of high-aperture scanner systems is provided. The imaging system for emulating high-aperture scanner systems includes imaging optics, a detector and an evaluating unit, wherein at least one polarization-active optical element is arranged as desired in the imaging beam path for selection of different polarization components of the imaging beam, an optical element with intensity attenuation function can be introduced in the imaging beam path, images of the mask and/or sample are received by the detector for differently polarized beam components and are conveyed to the evaluating unit for further processing. It is possible to examine lithography masks for defects in spite of increasingly smaller structures and increasingly higher image-side numerical apertures of the imaging systems Realistic images of the stepper systems can be generated by emulating the occurring vector effects.