De La Rue Systems Ltd.

Paul D Lacey

Victor B Chapman

Apparatus for detecting the presence of an ink on a substrate comprises a number of LEDs (1) for irradiating the substrate (2) with radiation at at least two different wavelengths, at least one of the wavelengths being chosen to correspond to an absorption or relectance wavelength of the ink to be detected. A sequence generator (5) modulates the radiation at each wavelength in a respective, different manner. A radiation sensor (3) senses radiation emitted by the substrate (2). A correlator (7,8) correlates samples of the sensed radiation from the radiation sensor (3) with signals each of which is modulated by a respective one of the modulations applied to the radiation, to generate correlation signals. A monitor (9) monitors the correlation signals in order to detect the presence of the said ink.

Method and apparatus for detecting inks

A monitoring system, particularly for use with document sorting apparatus, comprises a sensor assembly including a sensor for sensing a respective characteristic of an article and for generating a corresponding first output signal, and a detector controller for applying at least one of a predetermined set of algorithms to the first output signal from the sensor, in conjunction with data supplied to the detector controller, to generate one or more second output signals. A detector processor common to each of the sensor assemblies supplies the data and algorithm selection information to the detector controllers to control which of the set of algorithms is applied by the detector controller and to generate in response to the or each second output signal and reference data a third output signal representative of the characteristic of the article being monitored.

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Hampshire, United Kingdom

Paul D Lacey