Color laser engraving and digital watermarking

• US 20050001419A1
• Filed: 12/19/2003
• Published: 01/06/2005
• Est. Priority Date: 03/21/2003
• Status: Active Grant

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Levy, Kenneth L., Jones, Robert, LaBrec, Brian
• Granted Patent: US 7,763,179 B2
• Time in Patent Office: Days
• US Class Current: 281/2
• CPC Class Codes: B41M 5/24 Ablative recording, e.g. by burning marks; Spark recording marking by high energetic means, e.g. by laser otherwise than burning or ablative removal B41M5/26; materials or methods for recording or reproduction by optical means G11B7/00
• CPC Class Codes: B41M 5/34 Multicolour thermography
• CPC Class Codes: B42D 2035/14 Dot or raster patterns
• CPC Class Codes: B42D 2035/24 Colours
• CPC Class Codes: B42D 25/00 Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof printing processes to produce identification or security features B41M3/14
• CPC Class Codes: B42D 25/23 Identity cards
• CPC Class Codes: B42D 25/324 Reliefs
• CPC Class Codes: B42D 25/333 Watermarks
• CPC Class Codes: B42D 25/346 Perforations
• CPC Class Codes: B42D 25/41 using electromagnetic radiation B42D25/435 takes precedence
• CPC Class Codes: B42D 25/435 using electromagnetic radiation, e.g. laser
• CPC Class Codes: G03C 11/02 Marking or applying text

Abstract

A color laser engraving method engraves a document including a surface layer and one or more sub-layers. The sub-layer includes different colors and orientations of ink. A laser provides openings in the surface layer—to expose color ink in the sub-layer—to create color images and/or text. The different orientations of the colored inks include, e.g., circular, linear and overlapped groupings of ink. A sub-layer preferably includes many repeated instances of the grouping. A digital watermark is embedded in a document via transfer of the digital watermark in an embedded image or text, or by pre-embedding the document via altering intensity of colored inks on the original document card stock. A digital watermark can be carried via modulation with a pseudo-random noise sequence.

Claims

1. A method of color laser engraving a document, the document comprising a multi-layer structure including a surface layer and one or more sub-layers, the one or more sub-layers including coloring, said method comprising:

receiving the document; and

selectively providing openings in the surface layer with a laser to expose one or more of the sub-layers, wherein the coloring is perceptible through the openings.

2. The method of claim 1 wherein the coloring comprises a plurality of different colors arranged in a grouping, with the one or more sub-layers comprising repeated instances of the grouping.

3. The method of claim 2 wherein the plurality of different colors comprise cyan, magenta and yellow.

4. The method of claim 3 wherein the plurality of different colors further comprise black.

5. The method of claim 3, wherein the plurality of different colors comprise at least one of ink, pigment and dye.

6. The method of claim 2, wherein the grouping comprises the plurality of different colors arranged in a generally circular grouping.

7. The method of claim 6, wherein the coloring is perceptible through at least three openings per grouping.

8. The method of claim 2 wherein the grouping comprises the plurality of different colors arranged in a linear manner.

9. The method of claim 8, wherein the coloring is perceptible through at least three openings per grouping.

10. The method of claim 2 wherein the grouping comprises an overlapping arrangement of the plurality of different colors.

11. The method of claim 10, wherein the grouping requires only one opening per pixel to achieve a predetermined color.

12. The method of claim 1 wherein the one or more sub-layers comprise at least a first sub-layer and a second sub-layer, with the first sub-layer and the second sub-layer being adjacently arranged, and wherein the first sub-layer comprises a first coloring and the second sub-layer comprises a second, different coloring.

13. The method of claim 12, wherein the second coloring is perceptible through the openings in the surface layer when the openings extend through the first sub-layer.

14. The method of claim 12, wherein the one or more sub-layers further comprise a third sub-layer.

15. The method of claim 14, wherein the first sub-layer, the second sub-layer and the third sub-layer each comprise one of cyan, magenta and yellow.

16. The method of claim 12, wherein selectively providing at least one opening in the surface layer with a laser to expose one or more of the sub-layers exposes at least the first coloring of the first sub-layer and the second coloring of the second sub-layer, and wherein the opening is tapered to expose more of the first coloring relative to the second coloring.

17. The method of claim 16, wherein the tapered opening provides a human perceptible bull'"'"'s-eye effect.

18. The method of claim 2 wherein the coloring is subtly varied across the one or more sub-layers so as to embed a machine-readable plural-bit payload, and wherein the plural-bit payload on the document becomes machine-readable only after laser engraving of at least the surface layer.

19. The method of claim 18, wherein the subtle variations are in the form of subtle changes in at least one of coloring, localized intensity of the coloring and localized color contrast variations of the coloring.

20. The method of claim 18 wherein the plural-bit payload comprises a modulated pseudorandom noise sequence.

21. The method of claim 18 wherein the coloring comprises a plurality of colors, and wherein the colors comprise at least one of ink, dye and pigment.

22. The method of claim 18, wherein the machine-readable payload is embedded when the coloring is placed on the document.

23. The method of claim 1, wherein the laser comprises a multi-nozzle laser.

24. The method of claim 23, where each of the nozzles comprises an optical fiber.

25. The method of claim 1, wherein the laser comprises a diffraction grating.

26. The method of claim 1, wherein the laser is restricted so as to move only in a parallel manner relative to a surface of the document and in distance segments that correspond to sub-pixel and pixel sizes in the one or more sub-layers, and wherein a location of the laser is used to choose an appropriate color channel, and a power of the laser at the location corresponds to intensity of a color channel.

27. The method of claim 1, wherein the laser is restricted so as to move only in a parallel manner relative to a surface of the document and in distance segments that correspond to sub-pixel and pixel sizes in the sub-layer, and wherein a location of the laser is used to choose an appropriate color channel, and a number of openings created for each pixel is used to represent intensity of a color channel.

28. The method of claim 12 wherein the laser is moved in directions both parallel and perpendicular to a surface of the document, the laser being movable in distance segments parallel to the document surface that correspond to sub-pixel and pixel sizes in the one or more sub-layers and distance segments perpendicular to the document surface that correspond to a thickness of the one or more sub-layers, and wherein an appropriate color is selected based upon a distance from the surface of the document and a portion of the laser, and intensity of a color channel is used to select power sent to the laser.

29. The method of claim 12 wherein the laser is only moved in directions parallel to a surface of the document, with a color being selected based upon laser power, and intensity of the color is used to select a number of openings the laser opens for each pixel.

30. A method of marking a document which is to receive laser engraving, said method comprising:

providing one or more sub-layers, the one or more sub-layers to include coloration;

providing variations in the coloration in terms of at least one of color intensity and color contrast, the variations conveying a machine-readable plural-bit message; and

arranging a surface layer over the one or more sub-layers, wherein the surface layer obscures the plural-bit message until laser engraving of at least a portion of the surface layer, after which the plural-bit message is machine-readable with optical scanning of the document.

31. The method of claim 30 wherein the plural-bit payload comprises a modulated pseudorandom noise sequence.

32. The method of claim 30, further comprising laser engraving the document, wherein the plural-bit message becomes machine-readable with analysis of optical scan data representing a document area that received the laser engraving.

33. The method of claim 32, wherein a laser used for laser engraving comprises a multi-nozzle laser.

34. The method of claim 33, where each of the nozzles comprises an optical fiber.

35. The method of claim 32, wherein a laser used for laser engraving comprises a diffraction grating.

36. The method of claim 30, wherein the machine-readable plural-bit message comprises a digital watermark component.

37. An identification document comprising:

a sub-layer including a plurality of inks arranged in a grouping, wherein the sub-layer comprises repeated instances of the grouping; and

a surface layer adjacently arranged with the sub-layer, wherein the surface layer obscures at least a majority of the repeated instances of the grouping; and

wherein the identification document further comprises a plurality of openings in the surface layer, wherein at least some portions of some of the repeated instances of the grouping are perceptible through the plurality of openings to convey an image or text.

38. The identification document of claim 37, wherein a plural-bit machine-readable code is detectable through the openings.

39. The identification document of claim 37, wherein the openings result from laser engraving.

40. A method of providing a color image or pattern on media, the document comprising a multi-layer structure including a surface layer and one or more sub-layers, the one or more sub-layers including coloring, said method comprising:

receiving the document; and

selectively providing openings in the surface layer to expose one or more of the sub-layers, wherein the coloring is perceptible through the openings to provide the color image or pattern.

41. The method of claim 40, wherein the openings are provided through chemical processing.

42. The method of claim 40, wherein the openings are washed open after a curing process.