Coordinated illumination and image signal capture for enhanced signal detection

• US 9,749,607 B2
• Filed: 08/09/2013
• Issued: 08/29/2017
• 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:
  US13/964,014
• Publication Number:
  US 20130329006A1
• Time in Patent Office: 1,481 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 23/20 for generating image signals from infrared radiation only
• CPC Class Codes: H04N 23/56 provided with illuminating means
• CPC Class Codes: H04N 23/88 for colour balance, e.g. white-balance circuits or colour temperature control
• 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 image signal detection comprising:

obtaining image signals captured under different wavelength illumination, a first image signal captured under illumination of a light source of a first color, and a second image captured under illumination of a light source of a second color;

combining the first and second image signals to increase signal to noise ratio of a signal of interest within the image signals to form a combined signal, the signal of interest comprising a two dimensional signal comprising a first signal modulation of the first color and a second signal modulation of the second color, and wherein the combining comprises adding or subtracting pixels at corresponding locations in the first and second images; and

performing signal detection on the combined image signal, the signal detection detecting the two dimensional signal from the combined image signal.

2. The method of claim 1 wherein the image signals 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 wavelength illumination comprises pulsing of different color 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 images captured under different color light sources are combined to boost out-of-phase signals in distinct chrominance channels the first color comprising a first chrominance channel and the second color comprising a second chrominance channel.

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 image signal detection comprising:

obtaining image signals captured under different wavelength illumination, wherein the different wavelength illumination comprises pulsing of different color light sources in succession at a rate sufficient for light source illumination from the different color light sources to appear white to a user;

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

performing signal detection on the image signal corresponding to the channel of illumination.

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 a 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 wavelength illumination;

an image sensor for capturing image signals in coordination with the pulsed illumination;

a controller for coordinating the pulsed illumination and corresponding image capture comprises pulsing of different color light sources in succession at a rate sufficient for light source illumination from the different color light sources to appear white to a user; and

a signal detector in communication with the image sensor for obtaining image signals captured under different wavelength illumination, the signal detector configured to obtain an image signal corresponding to a channel of illumination corresponding to one of the color light sources, and configured to perform signal detection on the image signal corresponding to the channel of illumination.

14. The imaging device of claim 13 wherein the controller and signal detector are integrated.

15. The imaging device of claim 14 wherein the signal detector is implemented in instructions executing on one or more processors.

16. An imaging device comprising:

an illumination source for providing pulsed illumination of different wavelength illumination;

an image sensor for capturing image signals in coordination with the pulsed illumination;

a controller in communication with the illumination source and the image sensor to coordinate the pulsed illumination from the illumination source and image capture by the image sensor of image signals captured under different wavelength illumination, a first image signal captured under illumination of a light source of a first color, and a second image captured under illumination of a light source of a second color;

a processor configured with instructions to combine the first and second image signals to increase signal to noise ratio of a signal of interest within a combination of the first and second image signals, the signal of interest comprising a two dimensional signal comprising a first signal modulation of the first color and a second signal modulation of the second color, wherein the processor is configured with instructions to add or subtract pixels at spatially aligned locations in the first and second images to increase the two dimensional signal in the combination, and the processor is further configured with instructions to detect the two dimensional signal from the combination.

17. The imaging device of claim 16 wherein the image signals are captured under pulsed illumination in which two or more different color light sources are selectively illuminated.

18. The imaging device of claim 16 wherein the different wavelength illumination comprises pulsing of different color light sources in succession at a rate sufficient for the light source illumination to appear white to a user.

19. The imaging device of claim 17 wherein images captured under different color light sources are combined to boost out-of-phase signals in distinct chrominance channels, the first color comprising a first chrominance channel and the second color comprising a second chrominance channel.

20. The imaging device of claim 18 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.

21. The imaging device of claim 18 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.