Apparatus for detecting tape on sheets

摘要

Apparatus is disclosed for detecting the presence of shiny tape on a printed note, for example a banknote. An optical fibre fishtail array supplies visible light from a source (A) to a lengthwise strip of the banknote. A first array of photodetectors (D) detects light specularly reflected from a plurality of adjacent regions of the said strip, while a second array (B) arranged parallel to the first array (D) detects light reflected diffusely from corresponding ones of the said regions. An analyzing circuit receives signals from the photodetectors and indicates when the ratio of specularly reflected light from an illuminated element of the banknote to diffusely reflected light from the same element exceeds a predetermined value.