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See Inside Scientific American Volume 307, Issue 4

Smart Headlights Can See through Rain, Sleet and Snow

Novel headlights illuminate the road, even in bad weather



Thomas Fuchs

Drive through pounding rain or a snowstorm at night, and you will notice that your headlights illuminate the drops or flakes more than they shed light on the road ahead. New “smart” headlights may reduce this hazard by shining light into the spaces between the precipitation.

The headlight is actually an array of bulbs, and the key to its success is that even a sheet of heavy rain is mostly empty space. The system was designed by Carnegie Mellon University's Srinivasa Narasimhan and his colleagues at institutions including Texas Instruments and France's MINES ParisTech. It uses a digital camera to track the motion of individual raindrops or snowflakes and applies a computer algorithm to predict where each bit of precipitation will be a few milliseconds later. It then deactivates bulbs that would otherwise illuminate the drops or flakes in their predicted positions.

The camera captures an image every eight milliseconds and adjusts the bulbs in the headlamp within 13 milliseconds. Narasimhan claims it reduces the visibility of rain four meters away by about 70 percent when a car is moving at 30 kilometers per hour, and he plans to test the system in cars traveling at least 95 kilometers per hour. The researchers are developing quicker ways of transferring information from the camera to the headlight, but it will likely be another two or three years before his smart system is ready for the road.

This article was originally published with the title "Seeing in the Rain."

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