A method for measuring an angularly resolved intensity distribution in a reticle plane (24) of a projection exposure apparatus (10). The apparatus includes an illumination system (16), irradiating a reticle (22) arranged in the reticle plane (24) and having a first pupil plane (20). All planes of the projection exposure apparatus which are conjugate thereto are further pupil planes, and the reticle plane (24) and all planes which are conjugate thereto are field planes. The method includes: arranging a spatially resolving detection module (44) in the region of one of the field planes (24, 30) such that the detection module is at a smaller distance from this field plane than from the closest pupil plane (20), radiating electromagnetic radiation (21) onto an optical module (42) from the illumination system, and determining an angularly resolved intensity distribution of the radiation from a signal recorded by the detection module.