Monochrome imaging of digital watermarks in white light
First Claim
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1. A method for detecting a watermark, comprising:
- illuminating an item with white ambient light emitted by a blue light emitting diode (LED) coated with phosphor, the item including a watermark that is encoded in a color space;
emitting the white ambient light from the blue LED coated with phosphor, wherein the blue LED is located in a device holding the blue LED in a manner such that the item is illuminated; and
detecting the watermark in the item with a monochrome imager based on contrast in at least a blue-yellow spectrum of the white ambient light emitted by the blue LED coated with phosphor.
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Abstract
A monochrome imager used in such systems as a scanner can detect watermarks that have been encoded in the color space or chrominance. Such watermarks are called chroma watermarks and are considered more reliable than the traditional classic watermarks, which are encoded based on luminance. The monochrome imager detects the chroma watermark, which has been illuminated with ambient white light from a blue light emitting diode (LED) coated with phosphor.
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Citations
17 Claims
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1. A method for detecting a watermark, comprising:
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illuminating an item with white ambient light emitted by a blue light emitting diode (LED) coated with phosphor, the item including a watermark that is encoded in a color space; emitting the white ambient light from the blue LED coated with phosphor, wherein the blue LED is located in a device holding the blue LED in a manner such that the item is illuminated; and detecting the watermark in the item with a monochrome imager based on contrast in at least a blue-yellow spectrum of the white ambient light emitted by the blue LED coated with phosphor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A scanning device for detecting a chroma watermark, the scanning device comprising:
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a blue light emitting diode (LED) coated with phosphor configured to emit white light to illuminate an object having a chroma watermark encoded in a color space; and a monochrome imager configured to detect the chroma watermark based on a contrast in at least a blue-yellow spectrum of the white light emitted by the blue LED coated with phosphor. - View Dependent Claims (13, 14, 15, 16, 17)
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Specification