Printed matter – Maps
Patent
1982-06-11
1984-11-27
Arnold, Bruce Y.
Printed matter
Maps
283 91, 283902, 3501622, 35016221, G02B 518
Patent
active
044847971
ABSTRACT:
A variable index-of-refraction optical medium of certain minimum thickness and periodicity with respect to the wavelength of incident light--if it meets certain specified constraints with respect to (1) relative indices-of-refraction of both its internal structure and that of its surroundings and (2) relative values of incident wavelength to periodicity and the relative indices-of-refraction--operates to produce both angularly-dependent subtractive-color filter reflection spectra and subtractive-color filter transmission spectra in accordance with its physical parameters. Such filters are suitable for use as authenticating devices for sheet-material authenticated items.
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Knop Karl H.
Morf Rudolf H.
Arnold Bruce Y.
Haas George E.
Propp William
RCA Corporation
Seligsohn George J.
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