Anticounterfeiting method and device utilizing holograms and pse

Details Anticounterfeiting method and device utilizing holograms and pse Anticounterfeiting method and device utilizing holograms and pse

1990-08-24

1995-03-07

Gregory, Bernarr E.

Cryptography

By modifying optical image

380 6, 380 9, 380 23, 380 59, 283 17, 283 73, 283 86, 283 93, G09C 500

Patent

active

053965590

ABSTRACT:
A security device for use on identification cards, monetary documents, and the like using a reference pattern and a message pattern each having the appearance of a random pattern of dots. The reference pattern is a dense pattern of randomly positioned dots, and the message pattern is a modulated version of the reference pattern in which the dots of the reference pattern are slightly repositioned by an amount depending on the grey value or color value of a message image at each dot location. The message image is decrypted and becomes visible with a range of grey values when it is viewed through a film transparency of the reference pattern. The dot pattern may be printed, embossed or recorded as a photograph or a hologram. Decryption of the message image may be accomplished by viewing through a contact mask, superposition of images of the message pattern and reference pattern, by viewing the message pattern through a mask positioned at a real image of the reference pattern, or like means.

REFERENCES:
patent: 3772200 (1973-11-01), Livesay
patent: 3829661 (1974-08-01), Silverman et al.
patent: 3894756 (1975-07-01), Ward
patent: 3914877 (1975-10-01), Hines
patent: 4126373 (1978-11-01), Moraw
patent: 4269473 (1981-05-01), Flothmann et al.
patent: 4400616 (1983-08-01), Chevillat et al.
patent: 4586711 (1986-05-01), Winters et al.

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