Coordinated illumination and image signal capture for enhanced signal detection

• US 10,223,560 B2
• Filed: 08/25/2017
• Issued: 03/05/2019
• Est. Priority Date: 07/16/2009
• Status: Active Grant

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Boles, Jacob L., Reed, Alastair M., Lord, John D.
• Primary Examiner(s): Akhavannik, Hadi
• Application Number:
  US15/687,153
• Publication Number:
  US 20180039805A1
• Time in Patent Office: 557 Days
• Field of Search: None
• CPC Class Codes: G06F 16/9554 by using bar codes
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06K 7/12 using a selected wavelength, e.g. to sense red marks and ignore blue marks
• CPC Class Codes: G06K 7/1413 1D bar codes
• CPC Class Codes: G06V 10/141 Control of illumination
• CPC Class Codes: G06V 10/143 Sensing or illuminating at different wavelengths
• CPC Class Codes: G06V 10/147 Details of sensors, e.g. sensor lenses fingerprint or palmprint sensors G06V40/13; vascular sensors G06V40/145; eye sensors G06V40/19
• CPC Class Codes: H04N 1/40056 Circuits for driving or energising particular reading heads or original illumination means H04N1/401, H04N1/407 take precedence
• CPC Class Codes: H04N 1/482 using the same detector device sequentially for different colour components
• CPC Class Codes: H04N 1/484 with sequential colour illumination of the original
• CPC Class Codes: H04N 23/56 provided with illuminating means
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20
• CPC Class Codes: H04N 9/73 Colour balance circuits, e.g. white balance circuits or colour temperature control camera processing pipelines for colour balance H04N23/88

Abstract

Signal detection and recognition employees coordinated illumination and capture of images under to facilitate extraction of a signal of interest. Pulsed illumination of different colors facilitates extraction of signals from color channels, as well as improved signal to noise ratio by combining signals of different color channels. The successive pulsing of different color illumination appears white to the user, yet facilitates signal detection, even for lower cost monochrome sensors, as in barcode scanning and other automatic identification equipment.

Claims

1. A method for watermark signal detection comprising:

obtaining image frames, each captured under different color LED illumination, including at least a first frame captured under a first visible color LED illumination, and a second frame captured under a second, different visible color illumination;

combining the first and second frames to produce a combined frame in which signal to noise ratio of a digital watermark signal encoded in different color channels is increased; and

performing watermark signal detection on the combined frame, wherein the watermark signal detection comprises detection of a synchronization pattern followed by extraction of data from pixels of the combined frame based on detection of the synchronization pattern.

2. The method of claim 1 wherein the first and second frames are captured under pulsed illumination in which two or more different color light sources are selectively illuminated.

3. The method of claim 1 wherein the different color LED illumination comprises pulsing of different color LED light sources in succession at a rate sufficient for the light source illumination to appear white to a user.

4. The method of claim 2 wherein the first and second frames are combined to boost out-phase watermark signals in distinct chrominance channels.

5. The method of claim 3 wherein pulsing comprises selectively turning off light sources while a first light source remains on to capture an image frame under illumination of the first light source.

6. The method of claim 3 wherein the light sources include a white light LED and another LED of a first color, and pulsing comprises selectively turning off the white light LED to capture an image frame under illumination of the first color.

7. A method for watermark signal detection comprising:

obtaining image frames captured under different visible color LED illumination, wherein the different visible color LED illumination comprises pulsing of different color LED light sources in succession at a rate sufficient for the pulsing of illumination to appear white to a user;

from the image frames, separating an image signal corresponding to a channel of illumination corresponding to one of the light sources, and

performing a watermark signal detection on the image signal corresponding to the channel of illumination, wherein the watermark signal detection comprises detection of a synchronization pattern followed by extraction of data from pixels of the image signal corresponding to the channel of illumination based on detection of the synchronization pattern.

8. The method of claim 7 wherein a layer of an object illuminated by IR is captured and the signal detection is performed on a signal conveyed in an IR channel.

9. The method of claim 8 wherein the IR channel is captured with visible color sensor.

10. The method of claim 8 wherein the layer is hidden under a layer of material that is transparent to IR illumination.

11. The method of claim 10 wherein the layer comprises a flat layer hidden under a non- flat layer of a 3D object, and provides a reference signal for determining orientation of the 3D object.

12. The method of claim 11 wherein the flat layer provides an image based code signal conveying variable encoded information.

13. An imaging device comprising:

an illumination source for providing pulsed illumination of different visible color LED illumination;

an image sensor for capturing image frames in coordination with the pulsed illumination, the image frames including at least a first frame captured under a first visible color LED illumination, and a second frame captured under a second, different visible color illumination;

a controller for coordinating the pulsed illumination and corresponding image capture; and

a programmed processor in communication with the image sensor for obtaining the image frames, the programmed processor configured to combine the first and second frames to produce a combined frame in which signal to noise ratio of a digital watermark signal encoded in different color channels is increased, and configured to perform watermark signal detection on the combined frame, wherein the watermark signal detection comprises detection of a synchronization pattern followed by extraction of data from pixels of the combined frame based on detection of the synchronization pattern.

14. The imaging device of claim 13 wherein the first and second frames are captured under pulsed illumination in which two or more different color light sources are selectively illuminated.

15. The imaging device of claim 13 wherein the different visible color LED illumination comprises pulsing of different color LED light sources in succession at a rate sufficient for the light source illumination to appear white to a user.

16. The imaging device of claim 14 wherein the first and second frames are combined to boost out-phase watermark signals in distinct chrominance channels.

17. The imaging device of claim 15 wherein pulsing comprises selectively turning off light sources while a first light source remains on to capture an image frame under illumination of the first light source.

18. The imaging device of claim 15 wherein the light sources include a white light LED and another LED of a first color, and pulsing comprises selectively turning off the white light LED to capture an image frame under illumination of the first color.

19. The imaging device of claim 14 wherein first and second frames are subtracted to produce the combined frame for watermark signal detection, and wherein the first and second frames are added to produce the combined frame for barcode signal detection.

20. The imaging device of claim 19 wherein the programmed processor is configured to perform a weighted subtraction of the first and second frames to produce the combined frame for watermark signal detection and a weighted addition of the first and second frames to produce the combined frame for barcode signal detection.