The Camera That Can See Around Walls

A new device uses laser pulses to create 3-D images of areas beyond its line of sight

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Science fiction writer Arthur C. Clarke once famously wrote, “Any sufficiently advanced technology is indistinguishable from magic.” While we’ve recently covered a number of incredible technologies that seem to prove Clarke’s point—progress on the way to an invisibility cloak and a sound gun that can silence the human voice, among others—a new camera developed by scientists at the Massachusetts Institute of Technology is a picture-perfect example.

The camera, called CORNAR and developed by Ramesh Raskar and Andreas Velten of the M.I.T. Media Lab, makes innovative use of lasers to see around a solid impediment—in the experiments, a wall—and reveal an object on the other side.

As explained in the video above, CORNAR uses a new form of photography, called “femto-photography,” to “see” through solid objects. Although it might sound like pure magic, the technique actually relies on a super-quick laser pulse—50 femtoseconds long, or 50 quadrillionths of a second—to construct a 3-D model of a hidden area behind a wall or corner.

The concept is similar to a natural phenomenon: the way bats use echolocation to “see” in the dark. With bats, ultrasonic pulses are emitted to produce echoes, and the brain registers the time it takes for the echoes to return back to produce mental images of the surroundings.

The camera uses a super-quick laser blast in much the same way. The laser pulse bounces off a wall, then into an area obscured from view. Some of the laser’s photons enter this area and then bounce back, eventually returning to the camera. Because of the incredibly short duration of the laser pulse, the camera can precisely calculate how long it would take the light to travel through the scene if it were empty. It then compares this with the actual laser “echoes”—the photons that return to the camera after hitting the figure within the hidden area, taking fractions of a second longer—to reconstruct the detailed 3-D model of the obscured room.

The research team proposes a range of future applications for the technology. Rescue teams could use it to locate hidden survivors in a collapsed or burning building, or cars could be equipped to automatically locate vehicles on the other side of a blind corner. Minuscule endoscopic medical cameras could even use the technology to see around tight corners in the heart, lungs or colon during various procedures.

Right now, all of these applications are purely theoretical, because the experimental setup is bulky, expensive and fragile. But the researchers note that research is currently being done on femtosecond lasers and light detectors that would simplify the device and enable it to be moved out of the lab more easily. Additionally, the process currently takes about 10 minutes, but they hope to reduce it to as little as 10 seconds.

The possibilities for this type of technology are, quite frankly, hard to picture. Someday, like magic, your smartphone could be equipped with a camera that can take pictures of places you can’t even see.

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