Importance

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Abstract

An arrangement for the detection of disk-shaped objects in a cassette preferably for detecting the presence and the position of semiconductor wafers in a cassette is disclosed. Reliable detection of disk-shaped objects in cassettes is provided regardless of their orientation or any discontinuity in their edge region. This is done by an arrangement by detecting light reflected at the edges of the objects in that it has at least two linearly elongated rows of light sources which are arranged parallel to a family of planes predetermined by the cassette shelves and objects and which lie in a surface parallel to the edge areas to be detected. Further, an objective is arranged between the parallel linear light sources and by which a plurality of shelves is imaged simultaneously on the sensor unit. There can be read out of the array of sensor elements at least portions of an edge area of the objects which is elongated transversely to such an extent that, when imaged in the sensor plane, an irregularity present in the edge area of the object is always less than the read out portions of the elongated edge area.

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First Claim