Measurement of the tilt angle of tiltable mirrors with a measuring light assembly

The present invention relates to a monitoring device for determining the orientation of tiltable mirrors (9) in a mirror arrangement with a plurality of tiltable about at least one axis mirrors, at least one measuring light source (100) having at least one measuring light optical system (101) and a measurement light detection means (102, 103) are provided for the measuring light having a detection plane, wherein the measuring light source illuminates at least one respective groups of mirrors, preferably each mirror with the measuring light optical system with a characteristic lighting, wherein the characteristic illumination of each group or each mirror by the monitoring at the mirror in the detection plane measurement light detecting means is mapped, and wherein the measurement light detecting means is so prepared that the orientation of the tiltable mirror from the position of the light reflected by each mirror of the measuring light intensity in the detection plane e is rmittelt and overlapping intensities are separated by a plurality of mirrors using the charakterischen illumination in the detection plane. In addition, the invention relates to an illumination system for a projection exposure system for microlithography with a facet mirror arrangement (7) of a plurality of tiltable mirrors (9) which are arranged in a field or pupil plane of the illumination system, and a measuring light assembly comprising a measuring light source (100) has, from the measurement light independently from and transverse to the work light Beleuchtungssytems can be directed onto the facet mirror assembly in the field or pupil plane, wherein the measuring light arrangement, a measuring light optical system (101) for illumination of the facet mirror arrangement and a measuring light detection means (102, 103), wherein the measuring light optical system (101) and the measurement light detecting means (102, 103) are so constructed and arranged that the measurement light detecting means is at least partially disposed in an auxiliary pupil plane of the measuring light assembly so that the measurement light detecting means by di Intensity distribution e facet mirror arrangement produced is detectable.