Speed of Light Lingers in Face of New Camera

SLOW DOWN M.I.T.'s camera captures light particles seemingly in motion by using repeated exposures, creating a “movie” of a nanosecond-long event.

More than 70 years ago, the M.I.T. electrical engineer Harold (Doc) Edgerton began using strobe lights to create remarkable photographs: a bullet stopped in flight as it pierced an apple, the coronet created by the splash of a drop of milk.

Now scientists at M.I.T.’s Media Lab are using an ultrafast imaging system to capture light itself as it passes through liquids and objects, in effect snapping a picture in less than two-trillionths of a second.

The project began as a whimsical effort to literally see around corners — by capturing reflected light and then computing the paths of the returning light, thereby building images coming from rooms that would otherwise not be directly visible.

“When I said I wanted to build a camera that looks around corners, my colleagues said, ‘Pick something that is more safe for your tenure,’ ” said Ramesh Raskar, an associate professor of media arts and sciences at the Media Lab. “Now I have tenure, so I can say this is not so crazy.”

Dr. Raskar enlisted colleagues from the chemistry department to modify a “streak tube,” a supersensitive piece of laboratory equipment that scans and captures light. Streak tubes are generally used to intensify streams of photons into streams of electrons. They are fast enough to record the progress of packets of laser light fired repeatedly into a bottle filled with a cloudy fluid.