Patent ID: 7748274

Claim:
A document inspection system comprising: a transport system for transporting documents along a transport path through an inspection station; at least one ultrasonic inspection apparatus at the inspection station, the apparatus including ultrasonic transmitting and receiving transducers arranged on opposite sides of the transport path, a processing system for monitoring ultrasonic signals received by the receiving transducer(s), and an ultrasonic absorbing material provided around the transducers and facing the transport path for absorbing ultrasound reflected by a document; and a document guide apparatus, including a pair of document guides on either side of the transport path, one associated with the transmitting transducer(s) and the other associated with the receiving transducer(s), each document guide including one or more rails extending parallel with the transport path, each rail having a lower coefficient of friction than the absorbing material, and extending partially over the absorbing material so as to prevent documents contacting the absorbing material in use while leaving the absorbing material exposed to the transport path at least adjacent the transducers.