Turning Corners Into Cameras: Principles and Methods
We show that walls and other obstructions with edges can be exploited as naturally-occurring "cameras" that reveal the hidden scenes beyond them. In particular, we demonstrate methods for using the subtle spatio-temporal radiance variations that arise on the ground at the base of edges to construct a one-dimensional video of the hidden scene. The resulting technique can be used for a variety of applications in diverse physical settings. From standard RGB video recordings of the variations in intensity, we use edge cameras to recover a 1-D video that reveals the number and trajectories of people moving in an occluded scene. We further show that adjacent vertical edges, such as those that arise in the case of an open doorway, yield a stereo camera from which the 2-D location of hidden, moving objects can be recovered. We demonstrate our technique in a number of indoor and outdoor environments involving varied surfaces and illumination conditions.
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