Security devices

Details Security devices Security devices

1977-09-23

1980-02-05

Abercrombie, Willie G.

Printed matter

Calendar

283 9R, 283 58, B42D 1500

Patent

active

041869435

ABSTRACT:
A sheet element, such as a banknote or other document of intrinsic value, incorporating an optical authenticating device comprising a thin film element, preferably in the form of a strip, or thread disposed within the thickness of the sheet element and having known characteristics of spectral reflectance and transmittance, and wherein in the region of a least part of the thin film element the sheet element is formed with a pair of superposed windows between which the thin film element extends so as to be visible through each window.

REFERENCES:
patent: 3245697 (1966-04-01), Nugent
patent: 3414998 (1968-12-01), Berger
patent: 3919447 (1975-11-01), Kilmer, Jr. et al.
Optica Acta, 1973, vol. 20, No. 12, 925,937, "Optical Interference Coatings for Inhibiting Counterfeiting", by J. A. Dobrowolski et al-May 4, 1973.

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