Patent ID: 7726214

Claim:
Method for the contactless detection of flat objects, such as papers in sheet form with respect to a single sheet, a missing sheet and multiple sheets of said flat objects, said flat objects being placed in a beam path of at least one transmitter (T) and an associated receiver (R) of a sensor device, wherein a radiation transmitted between said at least one transmitter (T) and said receiver (R) is received by said receiver (R) in the form of a measuring signal (U M ), said measuring signal (U M ) is supplied to a following evaluation for generating a corresponding detection signal, wherein a characteristic of an input voltage (U E , U M ) of said measuring signal (U M ) is formed, wherein at least one correction characteristic (KK) is provided for evaluation, said correction characteristic (KK) transforms said characteristic of the input voltage (U E , U M ) of said measuring signal (U M ) from said receiver (R) as a function of a weight per unit area of said flat objects to a target characteristic (ZK), wherein for said papers in sheet form an approximately linear characteristic approaching an ideal single sheet characteristic with a gradient of approximately “0” is obtained as said target characteristic between an output voltage (U A , U Z ) at an output of the evaluation and said weight per unit area, in order to generate said corresponding detection signal, and wherein said sensor device is operated in a switchable manner, in pulsed operation, or continuous operation.