Low visibility watermark using time decay fluorescence
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United States of America Patent
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Apr 6, 2004
Issued Date -
N/A
app pub date -
Aug 31, 2001
filing date -
May 8, 1995
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
Media is embedded with an out-of-phase digital watermark. A first component of the digital watermark is printed using a first ultraviolet (UV) ink. The first UV ink includes a first fluorescence decay time. The second digital watermark component is inverted with respect to the first component and is printed using a second UV ink. The second ink includes a second fluorescence decay time, which is longer than the first decay time. The embedded media is illuminated with a UV pulse. The watermark is detected after the first emission decay time, but before the second emission decay time. The watermark is fragile under steady-state UV illumination since the inverted watermark component cancels the non-inverted component.
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