Laser Speckle Photography for Surface Tampering Detection

Technology #15585

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 The technology detects subtle surface changes that cannot be seen in traditional photography. Top left: the proposed prototype combines an SLR with a consumer pico laser projector. (a),(b) Images of a wall illuminated by the laser projector. The granular pattern (bottom left), called speckle, is caused by interference patterns of reflected coherent light. Between (a) and (b), the wall was touched gently. The speckle similarity map computed in (c) reveals where the wall was touched. (d)–(f): Without the laser projector, the before and after images (d) and (e) reveal no difference, as shown in the similarity map (f)
Categories
Inventors
Professor Fredo Durand
Department of EECS, MIT
External Link (people.csail.mit.edu)
Professor William Freeman
Department of EECS, MIT
External Link (billf.mit.edu)
Myers Davis
CSAIL, MIT
Samuel Hasinoff
CSAIL, MIT
Yichang Shih
CSAIL, MIT
Managed By
Daniel Dardani
MIT Technology Licensing Officer
Patent Protection

Laser speckle photography for surface tampering detection

US Patent 9,131,118

Laser Speckle Photography for Surface Tampering Detection

US Patent Pending 2014-0132761
Publications
Laser speckle photography for surface tampering detection
25th IEEE Conference on Computer Vision and Pattern Recognition, 2012 IEEE Conference , pp. 33-40

Applications

The Inventors have developed a laser illumination technique to detect surface changes in physical objects. This technology can be used in security and law enforcement scenarios to determine whether physical objects have been tampered with.  

Problem Addressed

Object tampering is of concern for many industries across a wide range of applications. It is often desirable to determine if an object has been tampered with. However, the changes made are frequently too subtle to be perceived with the naked eye or by comparing before and after photos. To address this, the Inventors introduce a new imaging technique that combines computational photography and laser speckle imaging to detect surface changes that are indistinguishable in regular photographs.

Technology

Laser illumination generates precise speckle patterns on a surface depending on the phase of the light wavefront. These laser speckle images encode phase information, depending on the constructive and destructive interferences of waves reflected at different points of the surface. This tampering detection technology leverages the fact that even small surface disturbances will affect travel distance and thus cause phase changes in reflected light, altering the speckle pattern visible under laser illumination. The Inventors take before and after images of the surface under laser light and can detect subtle contact by correlating the speckle patterns in these images. Because speckle imaging is highly sensitive to camera location and viewpoint alignment, the Inventors use a combination of computational rephotography and correlation analysis of the speckle pattern as a function of camera translation to provide a robust and reliable method to detect subtle surface contact.

Advantages

  • Mobile technology does not need to be present at the time of contact with the surface; ideal for situations where the surface of interest cannot be constantly monitored.