Laser Speckle Photography for Surface Tampering Detection

• US 20160010982A1
• Filed: 07/31/2015
• Published: 01/14/2016
• Est. Priority Date: 11/14/2012
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Shih, YiChang, Davis, Myers Abraham, Durand, Frederic, Freeman, William T., Hasinoff, Samuel Wiliam
• Granted Patent: US 10,288,420 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01B 11/254 Projection of a pattern, viewing through a pattern, e.g. moiré
• CPC Class Codes: G01B 11/303 using photoelectric detection means
• CPC Class Codes: G06F 18/22 Matching criteria, e.g. proximity measures
• CPC Class Codes: G06T 7/70 Determining position or orientation of objects or cameras camera calibration G06T7/80
• CPC Class Codes: H04N 7/18 Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast

Abstract

In one embodiment, a method comprises projecting, from a projector, a diffused on an object. The method further includes capturing, with a first camera in a particular location, a reference image of the object while the diffused is projected on the object. The method further includes capturing, with a second camera positioned in the particular location, a test image of the object while the diffused is projected on the object. The method further includes comparing speckles in the reference image to the test image. The projector, first camera and second camera are removably provided to and positioned in a site of the object.

Claims

1. A method comprising:

projecting, from a projector, coherent illumination on an object;

capturing, with a first camera in a particular location, a reference image of the object while the diffused laser is projected on the object;

capturing, with a second camera positioned in the particular location, a test image of the object while the coherent illumination is projected on the object; and

comparing speckles in the reference image to the test image;

wherein the projector, first camera and second camera are removably provided to and positioned in a site of the object.

2. The method of claim 1, further comprising:

capturing a plurality of reference images of the object;

generating a reference map of the object from the plurality of reference images;

before capturing the test image, positioning the second camera at the particular location by;

(1) taking a temporary picture with the second camera,

(2) repositioning the second camera based on features in the temporary picture and features in the generated reference map, and

(3) repositioning the second camera based on speckle comparison of the temporary image to the reference image; and

aligning the test image with the reference image by computing a similarity map.

3. The method of claim 1, wherein aligning the test image with the reference image further matches patches of the reference image to patches of the test image.

4. The method of claim 1, wherein positioning the second camera to the particular location further includes (4) repeating steps (1)-(3) until the second camera is returned to the particular location.

5. The method of claim 1, wherein the second camera is repositioned by at least one of a robotic device and motor.

6. The method of claim 1, wherein the second camera is repositioned along a coordinate plane, through a three-dimensional coordinate system, or rotated along one or more axes.

7. The method of claim 1, further comprising signaling, based on the comparison, whether the object was changed between capturing the reference image and capturing the test image.

8. The method of claim 1, further comprising outputting an indication of changed areas in the object between the reference image and the test image.

9. The method of claim 1, wherein the first camera and second camera are the same camera, and wherein positioning the same camera is returning the same camera to the particular location subsequently in time.

10. The method of claim 1, wherein comparing speckles in the reference image to the test image includes correlating speckles in the reference image to the test image.

11. A system comprising:

a projector configured to project coherent illumination on an object;

a first camera in a particular location configured to capture a reference image of the object while the coherent illumination is being projected;

a second camera positioned in the particular location and configured to capture a test image of the object; and

a correlation module configured to compare speckles in the reference image to the test image;

wherein the projector, first camera and second camera are removably provided to and positioned in a site of the object.

12. The system of claim 11, wherein at least one of the first camera, the second camera, and a third camera is configured to capture a plurality of reference images of the object;

and further comprising;

a map generation module configured to generate a reference map of the object from the plurality of reference images;

a camera scaffold module configured to, before capturing the test image, position the second camera at the particular location by;

(1) take a temporary picture with the second camera,

(2) reposition the second camera based on features in the temporary picture and features in the generated reference map,

(3) reposition the second camera based on speckle comparison of the temporary image to the reference image,

an image alignment module configured to align the test image with the reference image by computing a similarity map.

13. The system of claim 11, wherein the image alignment module is further configured to matches patches of the reference image to patches of the test image.

14. The system of claim 11, wherein the second camera scaffold module is further configured to (4) repeat steps (1)-(3) until the second camera is returned to the particular location.

15. The system of claim 11, wherein the camera scaffolding module includes at least one of a robotic device and motor configured to reposition the second camera.

16. The system of claim 11, wherein the second camera is repositioned along a coordinate plane, through a three-dimensional coordinate system, or rotated along one or more axes.

17. The system of claim 11, further comprising a signaling module configured to signal, based on the comparison, whether the object was changed between capturing the reference image and capturing the test image.

18. The system of claim 11, further comprising a speckle output module configured to output an indication of changed areas in the object between the reference image and the test image.

19. The system of claim 11, wherein the first camera and second camera are the same camera, and wherein positioning the same camera is returning the same camera to the particular location subsequently in time.

20. The system of claim 11, wherein the correlation module is further configured to correlate speckles in the reference image to the test image;