$500 ‘nano-camera’ can operate at the speed of light for collision avoidance for cars and other applications

A $500 “nano-camera” that can operate at the speed of light has been developed by researchers in the MIT Media Lab.

The three-dimensional camera, which was presented last week at Siggraph Asia in Hong Kong, could be used in medical imaging and collision-avoidance detectors for cars, and to improve the accuracy of motion tracking and gesture-recognition devices used in interactive gaming.

The camera is based on “Time of Flight” technology like that used in Microsoft’s recently launched second-generation Kinect device, in which the location of objects is calculated by how long it takes a light signal to reflect off a surface and return to the sensor. However, unlike existing devices based on this technology, the new camera is not fooled by rain, fog, or even translucent objects.

The new device uses an encoding technique commonly used in the telecommunications industry to calculate the distance a signal has traveled.

“We use a new method that allows us to encode information in time,” Raskar says. “So when the data comes back, we can do calculations that are very common in the telecommunications world, to estimate different distances from the single signal.”

The idea is similar to existing techniques that clear blurring in photographs, says Bhandari, a graduate student in the Media Lab. “People with shaky hands tend to take blurry photographs with their cellphones because several shifted versions of the scene smear together,” Bhandari says. “By placing some assumptions on the model — for example that much of this blurring was caused by a jittery hand — the image can be unsmeared to produce a sharper picture.”

The new model, which the team has dubbed nanophotography, unsmears the individual optical paths.

In 2011 Raskar’s group unveiled a trillion-frame-per-second camera capable of capturing a single pulse of light as it travelled through a scene. The camera does this by probing the scene with a femtosecond impulse of light, then uses fast but expensive laboratory-grade optical equipment to take an image each time. However, this “femto-camera” costs around $500,000 to build.

In contrast, the new “nano-camera” probes the scene with a continuous-wave signal that oscillates at nanosecond periods. This allows the team to use inexpensive hardware — off-the-shelf light-emitting diodes (LEDs) can strobe at nanosecond periods, for example — meaning the camera can reach a time resolution within one order of magnitude of femtophotography while costing just $500.

“By solving the multipath problem, essentially just by changing the code, we are able to unmix the light paths and therefore visualize light moving across the scene,” Kadambi says. “So we are able to get similar results to the $500,000 camera, albeit of slightly lower quality, for just $500.”

The basic technology needed for the team’s approach is very similar to that already being shipped in devices such as the new version of Kinect, Davis says. “So it’s going to go from expensive to cheap thanks to video games, and that should shorten the time before people start wondering what it can be used for,” he says. “And by the time that happens, the MIT group will have a whole toolbox of methods available for people to use to realize those dreams.”

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