METHOD AND APPARATUS FOR DETECTING SUPERIMPOSED SHEETS IN A TRANSPORT PATH

摘要

P Superimposed sheets are detected in a paper transport path (22, 24) by using these sheets as an acoustic interference filter. An ultrasound energy beam of appropriate frequency, emitted by an emitter transducer (12) in an inclined orientation with respect to the transport path, will suffer a much greater attenuation than that calculated on the basis of attenuation of a single sheet, due to the destructive combination of wave fronts reflected by the surfaces facing superimposed sheets.Application to the automatic reading of documents. / P