MIT researchers have developed an imaging system so fast that it captures the speed of light.
It allows them to string together shots taken less than two-trillionths of a second apart to create videos of light passing through liquids and objects.
The imaging system could someday have applications in medical imaging (such as in ultrasounds with light that show how light scatters one-dimensionally throughout the body), in industrial imaging (so as to see how light scatters in order to find defects in materials), or even in consumer photography to create the kinds of lighting effects created in professional studios.
How it works
The researchers, led by Dr. Ramesh Raskar, an associate professor of media arts and sciences at the MIT Media Lab, altered a piece of lab equipment typically used by chemists called a streak tube. As reported by the New York Times,
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.
Streak tubes are used to measure incidents that happen in ultra-short timeframes, but they normally offer their measurements in the form of data, not images.
The modified streak tube "camera" developed by Dr. Raskar takes videos of only one dimension of space (i.e. across a line), so the researchers have to take hundreds of thousands of shots at slightly different angles in order to create a two-dimensional video, such as the one below. This also means that they can only create videos of events that can be repeated over and over again.
The system is so fast it can be used to create a slow-motion video showing a burst of light as it travels up the length of a one-liter bottle, hits the cap and reflects back to the bottom of the bottle. “There’s nothing in the universe that looks fast to this camera," says Andreas Velten, another developer of this system, which cost $250,000.
While nothing may look fast to this camera, the data collection process looks slow to 21st-century humans: It takes an hour to gather all the images necessary for one video.
Watch Dr. Raskar and Velten explain how the imaging system works:
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photo: One of the things that distinguishes the researchers' new system from earlier high-speed imaging systems is that it can capture light 'scattering' below the surfaces of solid objects, such as the tomato depicted here. (MIT)