CAMBRIDGE, MASS.: Researchers at MIT’s Media Lab have built a virtual slow-motion camera that can capture images at 1 trillion frames per second--fast enough to capture the movement of light. The team used the system to record light from a titanium sapphire laser traveling through a one-liter soda bottle and bouncing off the cap.
The system uses an array of 500 sensors, each triggered at a trillionth of a second delay, Andreas Velton, one of the system’s developers said. It employs a “streak camera,” with a narrow slit for an aperture. The photons that make up light enter through the aperture and pass through an electric field that deflects them perpendicular to the slit. Because of the variations in the electrical field, late-arriving photons are deflected more. (See “Visualising Photons in Motion at a Trillion Frames Per Second.”)
The system is a spinoff of another project involving a camera that can see around corners. That camera works by bouncing light off a reflective surface and measuring the time it takes different photons to return. While both systems use ultrashort bursts of laser light and streak cameras, the arrangement of their other optical components and their reconstruction algorithms are tailored to their disparate tasks, MIT said.
The camera is intended for applications in chemistry, but it has its drawbacks, MIT said. To create the video of light passing through the plastic bottle, the shot had to be performed multiple times to produce a two-dimensional image. Precisely positioning and synching the camera with the pulse of light each time requires complex optics and control. Plus, the streak camera and the pulse laser alone cost $250,000.
~ Deborah D. McAdams
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