Patent ID: 7712386

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, and 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 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 the evaluation of the measuring signal takes place by means of a correction characteristic in amplitude evaluation form, and wherein a measuring signal phase undergoes a phase evaluation and that by linking both evaluations the detection signal is generated for single, missing and multiple sheets of said flat objects such as papers.