Laser Speckle Photography for Surface Tampering Detection

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.  

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.  

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  

Publications

"Laser Speckle Photography for Surface Tampering Detection." In Proceedings of the 25th IEEE Conference on Computer Vision and Pattern Recognition, 33–40. IEEE, 2012.