A polygon scanner (10) for detecting objects (24) in a monitored zone (22) is provided having a light transmitter (12); having a light receiver (30); having an evaluation unit (32); and having a rotatable mirror unit (20) for a periodic deflection of the light beam (16) that has a plurality of mirror facets (34) in order thus to scan an angular section multiple times per rotation of the mirror unit (20) by a respective mirror facet (34), wherein at least some of the mirror facets (34) have a different curvature from one another. In this respect, at least one of the mirror facets (34) is configured as a free-form surface whose curvature is adapted to the angle of incidence of the transmitted light beam (16) on the mirror facet (34) that varies during the rotation of the mirror unit (20).