For a confocal scanning microscope (1) an optical zoom system (41) with linear scanning is provided, which not only makes a zoom function possible, in that a variable magnification of an image is possible, but rather which additionally produces a pupil image in the illuminating beam path (IB) [BS] and thereby makes a variable image length possible (distance between the original pupil (En.P) [EP] and the imaged/reproduced pupil (Ex.P) [AP]) so that axially varying objective pupil positions can thereby be compensated.