How an ordinary camera can see around corners
Several teams of researchers have demonstrated devices that could do similar things, but the latest technique is entirely based on an algorithm the team built and requires no special equipment.
Goyal and his collaborators reconstructed images with a different trick. With a digital camera, they took pictures of light reflected off a wall that emanated from the computer screen hiding around the corner.
But they also placed an obstacle — a dark screen or a chair — in between the computer screen and the wall, and that obstacle blocked some of the light from reaching the wall. Counter-intuitively, the obstacle helps to keep the rays of light from getting too scrambled, which then makes it possible for the algorithm to reconstruct the images from information contained in the light particles that reach the camera. The principle is analogous to the one that allows pinhole cameras (and the eyes of certain molluscs) to produce sharp images without a lens: they block most of the light rays, except for those that go through a narrow hole.
Goyal and his collaborators demonstrated that the algorithm could then reconstruct various simple images displayed on the screen, and even an animation.
Fun for all
Because the team’s technique does not require special hardware, once perfected, it would be straightforward to turn it into a consumer product. “It’s completely plausible that this becomes a mobile-phone app,” Goyal says, although he has no plans to do so himself.