Patent ID: 8854604

Claim:
A projection exposure apparatus configured to image an object in a first object plane into a first image plane, comprising: an optical surface; and a measurement device configured to measure a parameter related to the optical surface at a plurality of locations on the optical surface, the measurement device comprising an illumination unit, the illumination unit comprising: a plurality of illumination members, each illumination member having a light exit facet configured to emit measuring light during use; and an optical imaging system configured to establish an imaging relationship between a second object plane and a second image plane, at least two light exit facets being arranged in the second object plane, and the second image plane at least substantially coinciding with the optical surface so that, during use of the measurement device, a plurality of measuring light spots are produced on the optical surface, the plurality of lights spots being images of the at least two light exit facets, wherein the second object plane is different from the first object plane, the second image plane is different from the first image plane, and the projection exposure apparatus is a microlithographic projection exposure apparatus configured so that, during use of the microlithographic projection exposure apparatus, a mask is the object in the first object plane.