Optics: measuring and testing – Document pattern analysis or verification
Patent
1982-01-25
1985-08-27
McGraw, Vincent P.
Optics: measuring and testing
Document pattern analysis or verification
283 85, 356354, G06K 710
Patent
active
045375046
ABSTRACT:
A security blank is formed with a light-redirecting spatial structure including a deterministic component establishing at least one authenticating feature, and a stochastic component superimposed on the deterministic component, and sufficiently obscuring the deterministic component so as largely to frustrate recognition of the function of the authenticating feature by intensity measurement of light reflected therefrom. Recognition of the function of the authenticating feature is made possible by a method and an apparatus measuring the degree of coherence of two narrow bundles of light rays obtained from light reflected from the spatial structure upon its illumination by light of a selected wavelength.
REFERENCES:
patent: 4119361 (1978-10-01), Greenaway
patent: 4129382 (1978-12-01), Greenaway
patent: 4250393 (1981-02-01), Greenaway
"Inverse Problems and Coherence" Ferwerda et al., International U.R.S.I.--Symposium 1980 on Electromagnetic Waves, Munich, Aug. 26-29, 1980, pp. 315C/1 and 315C/2.
"Meaurement of Second-Order Coherence in a Light Beam Using a Microscope & a Grating" Carter, Applied Optics, vol. 16, #3, Mar. 1977, pp. 558-563.
Baltes Heinrich P.
Glass Andrew S.
Jauch Karl
LGZ Landis & Gyr Zug AG
Marmorek Ernest F.
McGraw Vincent P.
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