De La Rue Systems Ltd.

Victor B Chapman

Michael Potter

Barry J Curl

Paul D Lacey

Apparatus for sensing the condition of a document

Luminescent security features in or on documents are detected using a detector comprising a fibre optic light guide arranged to transmit an interrogation beam originating from a source onto a document to be tested; and a housing in which a photo-diode array is mounted to receive luminescence emitted from the document. The photo-diode array is connected to electronic circuitry for discriminating between luminescence due to a security feature and other luminescence emitted by the document and for determining that a security feature has been detected.

Detecting luminescent security features

Apparatus is disclosed for scanning a banknote (33). A lengthwise strip of the banknote (33) is illuminated with white light, and the banknote is moved parallel to its width. Light reflected from all regions of the lengthwise strip is conveyed through an optical fibre fishtail array to a single photodetector, or to a spectroscope and then to several photodetectors for color scanning. The waveform produced by the or each photodetector is then characteristic of the surface of the banknote, and is used in an analyzing circuit for banknote pattern recognition, or to sense the condition of the banknote with regard to its age or degree of soiling. The analyzing circuit includes means for compressing or expanding the length of the waveform to give it a standard length for subsequent comparison with one or more stored characteristic waveforms in a memory (16). The apparatus also determines the mean level of intensity of the waveform in an integrator (9), and includes a circuit (24 to 28) for obtaining the standard deviation of selected points of the waveform from the mean value, a low standard deviation indicating a badly soiled or worn banknote.

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Hants, United Kingdom

Victor B Chapman