a device and a method for detecting and distinguishing between shelf - forming supports in cassettes and disk - shaped objects deposited thereon are provided for increasing accuracy in the determination of the position of shelves and objects as well as reliability of detection in distinguishing between cassette types without a disruptive influence being exerted on the objects by the inserted protective supports . the objects and different types of supports for the objects which are distinguished through an offset arrangement in the measurement plane pass through measurement beam bundles with their end sides , wherein each of the measurement beam bundles is situated in the region of only one type of support . the extension of the end sides of the supports in the measurement plane is completely detected by the measurement beam bundle . the device is used for the fabrication of integrated circuits .