Abstract: In a moiré method for measuring the distortion of an optical imaging system in which and object grid having a two-dimensional object pattern is arranged in an object plane of the imaging system and an image grid having a two-dimensional image pattern is arranged in an image plane of the imaging system, these patterns are configured in the form of, for example cross-hatched patterns or checker board patterns, are adapted to suit one another such that a two-dimensional moiré fringe pattern that may be detected by a two-dimensional, spatially resolving, detection device is created when the object grid is imaged onto the image grid using the imaging system. Distortion components of the imaging system may be simultaneously determined along two differently oriented, in particular, two mutually orthogonal, image directions from a two-dimensional moiré fringe pattern.