innovation

Camera captures light particles moving through space

Dec. 13, 2011 at 3:19 PM ET

M. Scott Brauer
Dr. Andreas Velten, Postdoctoral Associate, (left) and Dr. Ramesh Raskar pose with equipment in their lab, part of the Media Lab Camera Culture group, at MIT in Cambridge, Massachusetts, USA. Velten and Raskar's group has developed a camera that records at 1 trillion frames per second, which allows, for example, the recording of pulses of light moving through a liquid.

A new imaging system that captures visual data at a rate of one-trillion-frames per second is fast enough to create virtual super-slow-motion videos of light particles traveling and scattering through space.

For reference, light particles — photons — travel about a million times faster than a speeding bullet.

MIT's Media Lab have developed a system

 

In the video above, for example, a burst of laser light is seen traveling through a soda bottle and bouncing off the cap. Other videos show a ripple of laser light move across a table, over and into a tomato, and up a wall.

"What you see in the videos is an average of many pulses," Andreas Velten, a researcher in MIT's Media Lab who is leading the effort, explained to me Tuesday. "If we capture one pulse, we don't get enough information. First of all because it is too faint and second because we only see one line at a time." 

The technique to create the videos relies on what's called a streak camera. The aperture — opening — of this camera is a narrow slit that provides a reasonable field of view in the horizontal direction, but very limited view in the vertical — essentially a line, or row of pixels. 

"It can only see one line, but it gives you a very high frame rate — a trillion-frames-per second," Velten said. This allows the researchers to make a movie of one scan line. Several pulses of light are used to compose each scan line movie to improve image quality, he noted.

Then, a system of mirrors in front of the camera changes the field of view slightly so that a movie of the next line can be made. The process continues for each line of a scene, such as a pulse of light moving through a bottle. Then, the computer uses all this information to create the virtual slow-motion movies.

"So what you are seeing is actually an average of many pulses, but because our camera and laser are synchronized very well, all the pulses look exactly the same," Velten said. "That's basically the trick."

According to the researchers, it takes only a nanosecond — a billionth of a second — for light to scatter through a bottle, but it takes nearly an hour to collect enough data to stitch together a video.

While watching photons move through soda bottles and across tables is visually cool and educational, the technology could be used to study the properties of materials, as well in scientific and medical imaging, even "ultrasound with light," the researchers suggest.

For more on this technology, check out the video below featuring Velten and his adviser, Ramesh Raskar. 

More on high-tech camera technology:

John Roach is a contributing writer for msnbc.com. To learn more about him, check out his website. For more of our Future of Technology series, watch the featured video below.

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