| 摘要 |
1439173 Credit cards and the like GAO GES FUR AUTOMATION UND ORGANISATION mbH 3 May 1973 [3 May 1972] 21033/73 Heading B6A [Also in Divisions G4 and C4] A method of securing a paper against forgery and determining its authenticity, comprises providing therein or thereon, either all over or in selected regions, fluorescent materials which fluoresce in the visible, U.V. or I.R. spectral range with characteristic emission spectra when excited, and identifying a radiation peak that occurs within a half-value bandwidth of 1À5Š. The characteristic spectra may be in the form of emission line doublets. The authenticity check is carried out by a spectrophotometer having an excitation energy source and an array of photoelectric cells each responsive to radiation of a respective wavelength. The source may be a gas discharge lamp, a photo-flash, incandescent lamp, X-ray tube, electron ray tube or radioactive substance. The resultant fluorescence is passed through an interference filter, dispersion prism or grating having a 1À5Š half-value bandwidth cut-off. Other fluorescent materials, whose authenticity is not to be checked, may be present on the paper. The signals from the photoelectric cells are subtracted or divided for verification. |
