Security hologram with covert messaging
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United States of America Patent
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Apr 21, 1998
Grant Date -
N/A
app pub date -
Apr 23, 1996
filing date -
Apr 23, 1996
priority date (Note) -
Expired
status (Latency Note)
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Abstract
A security device includes a holographic image observable in ambient light and through which a covert image is observable in a focussed beam of bright light, such as a flash light. The holographic image is coated with a metal layer of low optical density, while the covert image is produced by a metal layer of high optical density disposed away from an observer relative to the holographic image. The covert image may itself be amplified by positioning the high optical density layer on a layer of micro prisms.
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