Laser speckle photography for surface tampering detection
Laser speckle photography for surface tampering detection
复制标题
用于表面篡改检测的激光散斑摄影
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
W. Freeman
中科院分区：
文献类型：
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作者：
Yichang Shih;A. Davis;Samuel W. Hasinoff;F. Durand;W. Freeman
通常期望检测表面是否已经被触摸，即使当对该表面所做的改变太细微而无法在一对之前和之后的图像中看到时。为了应对这一挑战，我们引入了一种结合计算摄影和激光散斑成像的新成像技术。在不需要受控实验室条件的情况下，我们的方法能够检测到在常规照片中无法区分的表面变化。它还是移动的，并且在与表面接触时不需要在场，这使得它非常适合无法持续监测感兴趣表面的应用。我们的方法利用了这样一个事实，即微小的表面变形会导致反射相干光的相位变化，从而改变激光照明下可见的散斑图案。我们在激光下拍摄表面的前后图像，并通过将这些图像中的散斑图案相关联来检测细微的接触。我们解决的一个关键挑战是散斑成像对相机的位置非常敏感，因此移除和重新引入相机需要高精度的视点对准。为此，我们使用的组合的计算重拍和相关分析的散斑图案作为相机平移的函数。我们的技术提供了一种可靠的方法，可以在以前仅在实验室条件下才能检测到的水平上检测细微的表面接触。有了我们的系统，这些细微的表面变化的检测现在可以带到野外。
It is often desirable to detect whether a surface has been touched, even when the changes made to that surface are too subtle to see in a pair of before and after images. To address this challenge, we introduce a new imaging technique that combines computational photography and laser speckle imaging. Without requiring controlled laboratory conditions, our method is able to detect surface changes that would be indistinguishable in regular photographs. It is also mobile and does not need to be present at the time of contact with the surface, making it well suited for applications where the surface of interest cannot be constantly monitored. Our approach takes advantage of the fact that tiny surface deformations cause phase changes in reflected coherent light which alter the speckle pattern visible under laser illumination. We take before and after images of the surface under laser light and can detect subtle contact by correlating the speckle patterns in these images. A key challenge we address is that speckle imaging is very sensitive to the location of the camera, so removing and reintroducing the camera requires high-accuracy viewpoint alignment. To this end, we use a combination of computational rephotography and correlation analysis of the speckle pattern as a function of camera translation. Our technique provides a reliable way of detecting subtle surface contact at a level that was previously only possible under laboratory conditions. With our system, the detection of these subtle surface changes can now be brought into the wild.