Document with an optical diffraction safety element
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United States of America Patent
Stats
-
Jan 15, 1991
Grant Date -
N/A
app pub date -
Feb 15, 1989
filing date -
Mar 3, 1988
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A document with an embossed macroscopic structure and acting through optical diffraction is disclosed. The structure, which serves as a security element comprises a plurality of surface portions with predetermined relief structures having spatial frequencies of over 10 lines/mm. Each surface portion is different from directly adjoining surface portions and at least some of the surface portions have a maximum dimension of less than 0.3 mm. To the naked eye, the pattern of surface portions on the document appears as a mesh of dots and lines. However, to an examiner with a magnifying device, the dots and lines appear as numbers, characters or other graphic features.
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