An optical imaging system for imaging at least two planes of a light beam spaced apart in the beam direction, in particular of a laser light beam, onto a common target site, for example a detector, has at least one optically imaging element arranged in the beam path of the light beam. The at least one optically imaging element is a collecting primary mirror, and arranged downstream of the primary mirror are at least two secondary mirrors that can be brought alternately into the beam path, the secondary mirrors being designed such that one secondary mirror permits imaging of one plane, and the other secondary mirror permits imaging of the other plane of the light beam onto the target site in each case.