Optical imaging system provided with an opto-electronic detection system for determining a deviation between the image plane of the imaging system and a second plane on which an image is to be formed

摘要

An optical imaging system is described which is provided with an opto- electronic detection system for determining a deviation between the image plane of the imaging system and a second plane on which an image is to be formed by the imaging system. After a first reflection on the second plane an auxiliary beam which is obliquely incident on said plane is reflected along itself and mirror-inverted, is subsequently reflected a second time on the second plane, and is finally incident on two detectors. The difference signal of the detectors, which is a measure of the deviation, is unaffected by tilting of the second plane and by local variations in reflectivity of in said plane.