Counterfeit document detection apparatus

DETAILED DESCRIPTION In accordance with one aspect of the present invention, a document counting and batching apparatus is provided with a control system governed by a programmable microprocessor.
The microprocessor is connected to a multi-channel analog-to-digital (A/D) converter which samples the analog signals from optical and magnetic document sensing devices.
As each document is processed, the microprocessor accumulates a plurality of sample values from the sensors via the A/D converter.
The accumulated sample values are compared with programmable thresholds and/or limit values in order to verify each document as it is transported through the apparatus.
The threshold and limit values used to verify the magnetic properties of the documents are each selected by the user or easily reprogrammed for verification of different types of documents.
Such reprogramming may, for example, be facilitated by replacement of a nonvolatile memory containing verification parameters and a control program executed by the microprocessor.
According to another aspect of the invention, the document counting apparatus incorporates a magnetic document verification system for documents having a magnetic property and the system incorporates features for reducing the influence of noise.
The magnetic document verification system employs a magnetic read head for producing an induced electrical signal in response to the passage of a document having a magnetic property by the head.
The magnetic head is rigidly mounted to a document guide plate.
In one embodiment of the invention, a magnet for enhancing the magnetic property of the documents is also rigidly mounted in a fixed relationship to the magnetic read head to form a unitary mechanical linkage with the read head.
As documents are transported along the guide plate, a path constricting roller positioned above the read head causes the documents to pass adjacent the magnetic read head at a uniform proximity thereto.
A signal conditioning circuit processes the induced electrical signal from the read head to provide a conditioned signal having a low noise content