Scientists at M.I.T's Media lab have created a camera that can capture the speed of light, taking a photo in less than two-trillionths of a second. Using multiple cameras, sensors, a pulse light source and mirrors, the researchers create slow motion movies of light moving through objects and liquids. They call the technique femto-photography. "We have built a virtual slow motion camera where we can see photons, or light particles through space," said Associate Professor Ramesh Raskar in an video interview. "Photons travel about a million times photons travel a million times faster than bullets. So our camera can see photons, or bullets of light traveling through space."
The project started as an effort to build a camera that looks around corners, Raskar told The New York Times's John Markoff. What began as an attempt to capture and compute the path of the reflected light, turned into this femto-photography.The M.I.T Media Lab explains how it works:
A laser pulse that lasts less than one trillionth of a second is used as a flash and the light returning from the scene is collected by a camera at a rate equivalent to roughly 1 trillion frames per second. However, due to very short exposure times (roughly one trillionth of a second) and a narrow field of view of the camera, the video is captured over several minutes by repeated and periodic sampling.
Capturing particles at these speeds with "sufficient brightness" would be impossible with a direct recording of light, explain the researchers in their abstract. The technique therefore employs a complex contraption that uses cameras and mirrors to build these slow motion movies tracking the lights movement across a scene, as the following demonstration shows.
The final product accurately depicts the way the light looked as it passed across or through various objects. Here we have another video of the technique, which captures laser pulses at 1 trillion frames per second, as light passes across a tomato.
Beyond looking cool, Raskar and his colleagues believe the imaging could prove useful in the medical profession and also in commercial photography, in which photographers are always trying to get just the right lighting. It also has every day implications, Raskar explained to Markoff. "Imagine if you have this in your phone about 10 years from now," he said. "You will be able to go to your supermarket and tell if your fruit is ripe."