×

Paper secured against forgery and device for checking the authenticity of such papers

  • US 4,146,792 A
  • Filed: 03/06/1978
  • Issued: 03/27/1979
  • Est. Priority Date: 04/30/1973
  • Status: Expired due to Term
First Claim
Patent Images

1. A device for checking the emission spectra in papers secured against forgery by containing, at at least one point, safety features in the form of fluorescent materials of a particular concentration which, in the excited condition, fluoresce, in at least one of the visible, ultraviolet and infrared spectral ranges, in characteristic emission spectra, and in which the fluorescent materials are constituted by rare earth elements embedded in substantially non-fluorescening crystal host lattices, and which, in the selected spectral range, fluoresce, in spectrally very narrow and sharp emission lines, determinable only by a high resolution spectrophotometer, so that the chemical structure of the fluorescent materials can be determined by using high resolution spectrophotometry to detect the wave-lengths at which the maxima very narrow and sharp emission lines are present, and to detect the wavelength at which the minima of the emission lines are present to detect the flanks of the emission lines;

  • said device comprising, in combination, an excitation light source for exciting the fluorescent materials to emit such characteristic emission spectra;

    a dispersion element, in the path of the rays of the emitted characteristic spectra, operable to fan out th characteristic emission spectra of the fluorescent substances;

    a photoelectric receiving unit, on which the fanned-out emission spectra is projected;

    said photoelectric receiving unit including, with respect to each maxima and each minima of the emission lines to be detected, at least one respective photoelectric transducer so geometrically located with respect to the fanned-out emission spectra as to be responsive to the associated emission lines to produce an output corresponding to the detected emission lines; and

    an evaluation unit connected to said photoelectric transducers and operable for comparing the emission values detected by said photoelectric receiving unit with predetermined desired values for checking the authenticity of papers subjected to scanning by the high resolution spectrophotometer constituted by said light source, said dispersion element, said receiving unit and said evaluation unit.

View all claims
  • 0 Assignments
Timeline View
Assignment View
    ×
    ×