Sparse modulation for robust signaling and synchronization

Patent metadata

Field	Value
Publication number	US-9635378-B2
Application number	US-201514725399-A
Country	US
Kind code	B2
Filing date	May 29, 2015
Priority date	Mar 20, 2015
Publication date	Apr 25, 2017
Grant date	Apr 25, 2017

Abstract

Sparse signal modulation schemes encode a data channel on a host image in a manner that is robust, flexible to achieve perceptual quality constraints, and provides improved data capacity. The host image is printed by any of a variety of means to apply the image, with sparse signal, to an object. After image capture of the object, a decoder processes the captured image to detect and extract data modulated into the sparse signal. The sparse signal may incorporate implicit or explicit synchronization components, which are either formed from the data signal or are complementary to it.

First claim

We claim:

1. A method for inserting a sparse, variable data carrying signal into a digital image, the method comprising:
providing a first signal component, the first signal component facilitating a synchronization function of the sparse, variable data carrying signal, and comprising first signal component values at coordinates within a two-dimensional block;
providing a second signal component, the second signal component being modulated to carry a variable data signal, and comprising second signal component values at coordinates within the two-dimensional block;
combining the first signal component and the second signal component to produce the sparse, variable data carrying signal by setting sparse elements at coordinates within the two-dimensional block where the first signal component values and the second signal component values provide compatible modulation of the digital image; and
inserting the sparse, variable data carrying signal into at least a first digital image layer or a first digital image channel of the digital image.

2. The method of claim 1 wherein the compatible modulation comprises a consistent direction of modulation of an optical property at a coordinate within the two-dimensional block.

3. The method of claim 1 wherein the compatible modulation comprises modulation at a coordinate in which both a value of the first signal component and a value of the second signal component fall within a common range bounded by at least one threshold.

4. The method of claim 3 wherein the compatible modulation comprises modulation at a coordinate in which both the value of the first signal component and the value of the second signal component are quantized to a common quantization value.

5. The method of claim 1 in which the first signal component and second signal component are provided in or converted to a binary form, and wherein the compatible modulation is determined by applying a logical AND operation between binary values of the first signal component and the second signal component at a coordinate, and the compatible modulation corresponds to coordinates where the binary values of the first signal component and the second signal component agree.

6. The method of claim 5 wherein at least one of the first signal component or the second signal component is converted to a binary form by applying a threshold.

7. The method of claim 1 wherein at least one of the first signal component or the second signal component is a multi-valued signal, and is converted to a sparse signal component by applying at least a first threshold, and the combining comprises setting sparse elements at coordinates where the sparse signal component and a value of either of the first signal component or the second signal component are consistent.

8. The method of claim 7 wherein the first signal component is a multi-valued signal component.

9. The method of claim 8 wherein the multi-valued signal component represents a synchronization template formed by a set of peaks in a transform domain.

10. A method for inserting a sparse, variable data carrying signal into an image, the method comprising:
providing a first orthogonal signal component, the first orthogonal signal component comprising first signal component values at coordinates within a two-dimensional area;
providing a second orthogonal signal component, the second orthogonal signal component being modulated to carry a variable data carrying signal, and comprising second signal component values at coordinates within the two-dimensional area;
combining the first orthogonal signal component and the second orthogonal signal component to produce the sparse, variable data carrying signal by selecting a subset of the first signal component values and the second signal component values, the selected subset of the first signal component values and the second signal component values comprising less signal component values than the second signal component values; and
inserting the sparse, variable data carrying signal into at least a first image layer or first image channel of the image.

11. The method of claim 10 including quantizing the first orthogonal signal component and the second orthogonal signal component to produce first and second sparse signal components, and merging the first and second sparse signal components.

12. The method of claim 11 wherein the quantizing comprises applying at least a first threshold to remove signal from the first orthogonal signal component or the second orthogonal signal component.

13. The method of claim 10 including combining the first orthogonal signal component and the second orthogonal signal component, and quantizing the combined first orthogonal signal component and the second orthogonal signal component to produce the sparse, variable data carrying signal.

14. The method of claim 10 wherein the first orthogonal signal component being formed to facilitate synchronization of the sparse, variable data carrying signal.

15. A method for inserting a sparse, variable data carrying signal into an image, the method comprising:
providing a sparse pattern of elements at coordinates within a two-dimensional area;
providing a signal component, the signal component being modulated to carry a variable data signal;
generating the sparse, variable data carrying signal by distributing the signal component within the two-dimensional area based on the location of the sparse pattern of elements; and
inserting the sparse, variable data carrying signal into at least a first image layer or a first image channel of the image.

16. The method of claim 15 wherein the signal component is converted to a sparse, variable data carrying signal by removing signal elements of the signal component at coordinates where the signal component does not coincide with coordinates of the sparse pattern of elements.

17. The method of claim 15 wherein the two-dimensional area comprises a two-dimensional block, and wherein the signal component is repeated in two-dimensional blocks within the image, and different sparse patterns are used to distribute the signal component in plural of two-dimensional blocks.

18. A system for inserting a sparse, variable data carrying signal into a digital image, said system comprising:
memory for storing data representing the digital image; and
one or more processors programmed for:
providing a first signal component, the first signal component facilitating a synchronization function of the sparse, variable data carrying signal, and comprising first signal component values at coordinates within a two-dimensional area;
providing a second signal component, the second signal component being modulated to carry a variable data signal, and comprising second signal component values at coordinates within the two-dimensional area;
combining the first signal component and the second signal component to produce the sparse, variable data carrying signal by setting sparse elements at coordinates within the two-dimensional area where the first signal component values and the second signal component values provide compatible modulation of the digital image; and
inserting the sparse, variable data carrying signal into at least a first digital image layer or a first digital image channel of the digital image.

19. The system of claim 18 wherein the compatible modulation comprises a consistent direction of modulation of an optical property at a coordinate within the two-dimensional block.

20. The system of claim 18 wherein the compatible modulation

Assignees

• Digimarc Corp

Inventors

• Holub Vojtech
• Haaga Donald
• Sharma Ravi K

Classifications

• H04N1/32224

  Replacing pixels of an image with other pixels from the same image, e.g. texture block coding · CPC title

• H04N1/32229 Primary

  with selective or adaptive application of the additional information, e.g. in selected regions of the image (H04N1/32213 takes precedence) · CPC title

• G06T2201/0061

  Embedding of the watermark in each block of the image, e.g. segmented watermarking · CPC title

• H04N19/124

  Quantisation · CPC title

• H04N1/32261

  in binary data (H04N1/32256 takes precedence) · CPC title