MIT researchers have created a new imaging system that can acquire visual data at an effective rate of one trillion exposures per second—fast enough to produce a slow-motion video of a burst of light traveling the length of a plastic bottle. “There’s nothing in the universe that looks fast to this camera,” says Media Lab postdoc Andreas Velten, one of the system’s developers.
The system relies on a technology called a streak camera, whose aperture is a narrow slit. Particles of light—photons—enter the camera through the slit and are converted into electrons, which pass through an electric field that deflects them in a direction perpendicular to the slit. As a burst of light travels through a plastic bottle, some of its photons exit the bottle all along the way; the camera captures where those photons exit. Because the electric field is changing very rapidly, it deflects the electrons corresponding to late-arriving photons more than it does those corresponding to early-arriving ones. The camera can thus determine the time of arrival of photons passing through a one-dimensional slice of space.
To produce their super-slow-mo videos, Velten, Media Lab associate professor Ramesh Raskar, and chemistry professor Moungi Bawendi must perform the same experiment—such as passing a light pulse through a bottle—over and over, continually repositioning the streak camera to acquire a new one-dimensional sample of the scene. It takes only a nanosecond—a billionth of a second—for light to scatter through a bottle, but it takes about an hour to collect all the data necessary to build up a two-dimensional image for the final video. For that reason, Raskar calls the new system “the world’s slowest fastest camera.”
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