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"Light Rain" -- The Discovery Files

The Discovery Files
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Researchers at Carnegie Mellon University's Robotics Institute have invented a "smart" headlight system that can improve visibility by constantly redirecting light to shine between particles of precipitation.

Credit: NSF/Karson Productions

Audio Transcript:

(Sound effect: thunder, rain) Rain, rain--go away.

I'm Bob Karson with the discovery files--new advances in science and engineering from the National Science Foundation.

(Sound effect: car-int wiper, driving in heavy rain) You've been there, driving through a heavy rain or snow storm at night, lo beam, hi beam, nothing seems to improve visibility. But the "smart headlight" being developed by Carnegie Mellon University may change that.

The team started with the real problem: The same light you need for visibility is reflected right back at you by raindrops or snow. But what if headlights could "see" and predict the track of raindrops or snow and flicker off different parts of the headlight for a fraction of a second? Not enough for your eye to notice, but enough to "un-light" the drops in their predicted positions?

To humans, rain looks like long streaks that seem to fill the air. But a high-speed camera sees rain as discrete drops with plenty of space between drops to distribute light. The researchers showed in the lab that the system could detect raindrops, predict their movement, and adjust the light projector in 13 milliseconds--fast enough to eliminate almost 80 percent of visible rain at low speeds.

The system makes a torrential downpour appear as a drizzle while losing only 6% of the light from the headlamp, all without being noticed by the human eye.

Kind of gives new meaning to the term, "light rain."

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