Method and apparatus for analyzing a group of photolithographic masks

The invention relates to a method for analyzing a group of at least two masks for photolithography, wherein each of the masks comprises a substructure of a total structure, which is to be introduced in a layer of the wafer in the lithographic process, and the total structure is introduced in the layer of the wafer by introducing the substructures in sequence. In this method, a first aerial image of a first one of the at least two masks is recorded, digitized and stored in a data structure. Then, a second aerial image of a second one of the at least two masks is recorded, digitized and stored in a data structure. A combination image is generated from the data of the first and second aerial images, which combination image is represented and/or evaluated.