Method and apparatus for checking documents of value

Details Method and apparatus for checking documents of value Method and apparatus for checking documents of value

2008-09-22

2010-11-09

Porta, David P (Department: 2884)

Radiant energy

Luminophor irradiation

Methods

Reexamination Certificate

active

07829869

ABSTRACT:
The invention relates to a method and an apparatus for recognizing forged documents of value, wherein the documents of value are illuminated with clocked excitation light of a light source. Within the bright phase of the excitation light a first luminescence intensity is detected, within the dark phase a second luminescence intensity. Because of the afterglow of the light pulses there is a residual fluorescence, which distorts the luminescence intensity in the dark phase. By linking the second luminescence intensity with the first luminescence intensity, e.g. by subtracting a scaled first luminescence intensity, a corrected second luminescence intensity is determined, which substantially corresponds to the phosphorescence signal of the document of value.

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Sutherland et al., “Simultaneous measurement of fluorescence and phosphorescence using synchronously gated photon counters,” 1979, Analytical Biochemistry, pp. 158-165. Abstract only.

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