Security devices
AssigneeThe Governor and Company of the Bank of England
InventorPeter D. Lee
Life of this patent
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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.
Claims13
A sheet element incorporating an optical authenticating device comprising a thin film dichroic element disposed within the thickness of the sheet element, said thin film dichroic element comprising a stack of thin film layers and having known characteristics of spectral reflectance and transmittance, and wherein the transmissivity of the sheet element varies about the thin film element so that at at least one point where said transmissivity is relatively great said sheet element constitutes a pair of superposed windows between which the thin film element extends so as to be visible though each window, thereby to permit observance of said characteristics of spectral reflectance and transmittance.
A banknote consisting of a rectangular sheet element incorporating an optical authenticating device comprising a thin film element in the form of a strip disposed within the thickness of, and extending across the sheet element, said thin film element comprising a stack of thin film layers and having known characteristics of spectral reflectance and transmittance, and wherein the transmissivity of the sheet element varies along the said strip so that at at least one point where said transmissivity is relatively great the sheet element constitutes a pair of superposed windows between which the thin film element extends so as to be visible through each window, thereby to permit observance of said characteristics of spectral reflectance and transmittance.
Dependencies are inferred from the claim text.