Method and apparatus for encoding paper with information

• US 20040131225A1
• Filed: 08/14/2003
• Published: 07/08/2004
• Est. Priority Date: 11/10/1999
• Status: Active Grant

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Alattar, Adnan M.
• Granted Patent: US 7,050,201 B2
• Time in Patent Office: Days
• US Class Current: 382/100
• CPC Class Codes: D21F 11/00 Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
• CPC Class Codes: D21F 9/00 Complete machines for making continuous webs of paper
• CPC Class Codes: G03G 21/046 by discriminating a special original, e.g. a bank note
• CPC Class Codes: G06T 1/0021 Image watermarking
• CPC Class Codes: G06T 2201/0052 Embedding of the watermark in the frequency domain

Abstract

Paper is textured with a pattern that yields a known signature signal when transformed to the frequency domain. This signature can be used for various purposes, including determining the angular orientation of the paper when scanned, conveying a plural-bit digital watermark, and for simple document recognition purposes (e.g., photocopiers that refuse to reproduce banknotes). The texturing can be effected during the paper-making process, e.g., by shaping the surface of a de-watering element accordingly.

Claims

1. A paper-making method including:

defining a two-dimensional signal that encodes plural bits of data;

defining a frequency-domain signal;

inverse transforming the frequency-domain signal to yield a pattern in the spatial domain; and

shaping an element of the paper-making apparatus in accordance with said spatial domain pattern; and

shaping the element of a paper-making apparatus in accordance with a pattern corresponding to said signal.

2. The method of claim 1 in which the element is a de-watering element.

3. The method of claim 1 in which the two-dimensional signal defines said pattern in the spatial domain.

4. The method of claim 3 further comprising combining the spatial domain pattern and the signal.

5. The method of claim 1, wherein said shaping steps impart a steganographic pattern on the element.

6. A de-watering element for a paper-making apparatus, characterized in that its surface topology is patterned in accordance with the following method:

defining a two-dimensional signal that encodes plural bits of data;

defining a frequency-domain signal;

inverse transforming the frequency-domain signal to yield a pattern in the spatial domain; and

shaping an element of the paper-making apparatus in accordance with said spatial domain pattern; and

shaping the element of a paper-making apparatus in accordance with a pattern corresponding to said signal.

7. The element of claim 6 in which the frequency-domain signal comprises plural impulses.

8. The element of claim 6 in which the two-dimensional signal defines said pattern in the spatial domain.

9. The element of claim 6, wherein the shaping of the element imparts a steganographic pattern on the element.

10. A method of marking a paper document comprising:

receiving a first signal comprising plural encoded bits of data;

receiving a second signal comprising an orientation component, the orientation component corresponding to a predetermined frequency domain orientation component; and

in a paper document production process, including a step that imparts into a surface topology of the paper document the first signal and the second signal to thereby steganographically mark the paper document.

11. The method of claim 10, wherein the orientation component comprises plural impulses.