Superfast laser camera peers around corners

Jeff Hecht, contributor

http://www.newscientist.com/blogs/onepercent/2012/03/super-fast-laser-camera-peers.html

Looking around corners is easy - if you can put a mirror at the right place and only need to see in two dimensions. But what if you don't have a mirror? The Camera Culture group at the MIT Media Lab have developed a special flash camera for the job that takes 3D images of what's around the bend.
The camera fires very short laser pulses - lasting only 0.05 trillionths of a second - at a flat wall that scatters light toward the object hidden behind a corner, as shown in the video. The object then scatters some of that light back toward the wall, and for two trillionths of a second the high-speed camera collects light hitting the wall.
The trick that makes the special camera work is that it sees only light that makes the round trip in a very narrow slice of time. Changing the interval between the laser flash and the camera snap measures light returned at different times, corresponding to parts of the object at different distances. This allows the system to build up a 3D image of the hidden object. The resolution is limited by the speed of light, which travels about 0.6 millimetres during the two trillionths of a second of each camera frame, and by the fact that light scattered on different paths can return to the camera at the same time.
The system could be valuable to look for hidden objects in hazardous areas, Andreas Velten and colleagues write in Nature Communications. (DOI: 10.1039/ncomms1747)

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