MONOCHROME IMAGING OF DIGITAL WATERMARKS IN WHITE LIGHT

• US 20170308987A1
• Filed: 04/24/2017
• Published: 10/26/2017
• Est. Priority Date: 04/22/2016
• Status: Active Grant

• Current Assignee: Datalogic USA, Inc.
• Original Assignee: Datalogic USA, Inc.
• Inventors: OLMSTEAD, BRYAN
• Granted Patent: US 10,453,162 B2
• Time in Patent Office: Days
• CPC Class Codes: G06T 1/0028 Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 2201/0065 Extraction of an embedded watermark; Reliable detection
• CPC Class Codes: H04N 1/02845 using an elongated light source, e.g. tubular lamp, LED array
• CPC Class Codes: H04N 1/32309 in colour image data
• CPC Class Codes: H04N 2201/0081 Image reader H04N2201/0091 - H04N2201/0094 take precedence

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.

Claims

1-3. -3. (canceled)

4. A system for detecting a watermark, comprising:

a monochrome imager that illuminates an item with white light produced by a blue light emitting diode (LED) containing a phosphor coating, the item including a watermark, wherein the white light produced by the blue LED containing the phosphor coating provides contrast such that the watermark is detectable by the monochrome imager.

5. The system of claim 4, wherein the monochrome imager detects contrast in a blue-yellow color spectrum based on the illumination of the watermark with the white light produced by the blue LED containing the phosphor coating.

6. The system of claim 5, wherein the contrast is detected by the monochrome imager based on chrominance of the watermark as illuminated.

7. The system of claim 6, wherein the monochrome imager decodes data of the watermark that is encoded in at least one of a red-green channel or blue-yellow channel.

8. The system of claim 4 wherein the blue LED containing the phosphor coating of the monochrome imager produces white light having a cool chromaticity.

9. The system of claim 8, wherein the monochrome imager detects contrast in at least a blue-yellow channel of the white light based on the illumination of the watermark with the white light having a cool chromaticity produced by the blue LED containing the phosphor coating.

10. The system of claim 4, wherein the blue LED containing the phosphor coating of the monochrome imager produces white light having a warm chromaticity.

11. The system of claim 10, wherein the monochrome imager detects contrast in at least a red-green channel of the white light based on the illumination of the watermark with the white light having a warm chromaticity produced by the blue LED containing the phosphor coating.

12. 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.

13. The method of claim 12, wherein detecting the watermark in the item with a monochrome imager based on contrast in at least the blue-yellow spectrum of the white ambient light emitted by the blue LED coated with phosphor further comprises:

measuring signal strength in at least one of a red signal, a green signal, a blue signal, and a yellow signal.

14. The method of claim 13, wherein a difference measured between signal strength of a blue signal relative to a yellow signal is used to detect contrast in at least the blue-yellow spectrum.

15. The method of claim 12, further comprising:

when the watermark that is encoded in the color space is detected via the monochrome imager, decoding the watermark.

16. The method of claim 12, further comprising:

when contrast in at least the blue-yellow spectrum of the white ambient light is not detectable, detecting the watermark in the item with the monochrome imager based on contrast in a red-green spectrum of the white ambient light emitted by the blue LED coated with phosphor.

17. A scanning device for detecting a chroma watermark, the scanning device comprising:

a monochrome imager comprising a blue light emitting diode (LED) coated with phosphor, wherein the blue LED coated with phosphor emits white light to illuminate an object having a chroma watermark, the chroma watermark to be detected by the monochrome imager.

18. The scanning device of claim 17, wherein the monochrome imager detects contrast in a blue-yellow spectrum of the white light emitted by the blue LED coated with phosphor.

19. The scanning device of claim 18, wherein the monochrome imager detects contrast by measuring relative signal strength between a blue signal and a yellow signal.

20. The scanning device of claim 17, wherein the monochrome imager detects contrast in a red-green spectrum of the white light emitted by the blue LED coated with phosphor.

21. The scanning device of claim 20, wherein the monochrome imager detects contrast by measuring relative signal strength between a red signal and a green signal.

22. The scanning device of claim 17, wherein when the chroma watermark is detected by the monochrome imager, the scanning device decodes the watermark.

23. The scanning device of claim 17, wherein the chroma watermark that is encoded in at least one of a red-green channel or blue-yellow channel.