A method for measuring the degree of contamination of bank notes or the like

摘要

1422563 Photo-electric measuring appartus GAO GES FUR AUTOMATION UND ORGANISATION mbH 20 March 1973 [21 March 1972] 13372/73 Heading G1A Dirt accumulation on an article, e.g. a bank-note is measured by a scanning device arranged to scan at least one margin of the article, scanning signals from the device being fed in parallel to at least two threshold circuits 13À1-13À3, the outputs of the circuits being applied to an integrator 15, and the output of the integrator being fed to a further threshold circuit 16. As shown, a bank-note 7 is moved relative to a scanning device which comprises a light scource 1 and a photo-electric cell 6 which receives light reflected from the bank-note via a lens 3 and two diaphragms 4, 5. The output of the cell 6 is amplified at 10 and has its D.C. component eliminated by a device 11 to which is applied a compensating D.C. signal representative of the mean brightness of the bank-note. This D.C. signal is derived from a device 12 during the first part of the scan. The outputs of the threshold circuits are weighted by devices 14À1-14À3 which include resistors. The threshold devices have different levels, the weighting factors being proportional to the levels.