Abstract: A method and a means for checking genuineness of paper money are based upon detection of the characteristic difference in the printing process for genuine bank notes and counterfeit bills produced with a color copying machine. The detection is conducted in narrow wavelength bands respectively in typical red and blue color ranges, and simultaneously in particular directions, with reflected and scattered light. Detection of intensity in a correspondingly narrow band near the maximum sensitivity range of the eye, i.e. in the green range, and in another direction, is also conducted for reference purposes. Preferably the measurement is made in a particularly selected point where the contents of blue and red in the print of the genuine bank note is at an extremum, i.e. high or low.

Abstract: An optical coin detector uses the spatial and/or temporal periodic modulation imparted to incident light which is reflected from the coin due to the combined effect of the stamping on the coin and its motion past a detection area. Detection of modulated, reflected light takes part from the end edge of the coin or from one of its side surfaces, and is effected by using one light sensitive detector with an adapted line screen pattern arranged in front of the detector, or by using a detector array.