US 6,718,046 · Granted 2004-04-06
Low visibility watermark using time decay fluorescence
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.
Patent details
- Publication number
- US 6,718,046
- Filing date
- 2001-08-31
- Grant date
- 2004-04-06
- Assignee
- Digimarc Corporation
- Inventor(s)
- REED ALASTAIR M., BERKLEY, JR. LOU H.
- CPC class
- G06K7/1417
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