A microlithographic projection exposure apparatus includes an optical surface, which may be formed by a plurality of micro-mirrors, and a measurement device which is configured to measure a parameter related to the optical surface at a plurality of locations. The measurement device includes an illumination unit with a plurality of illumination members, each having a light exit facet. An optical imaging system establishes an imaging relationship between an object plane in which at least two light exit facets are arranged, and an image plane which at least substantially coincides with the optical surface. A detector unit measures the property of measuring light after it has interacted with the optical surface, and an evaluation unit determines the surface related parameter for each of the locations on the basis of the properties determined by the detector unit.