Skip to Content

Smart Headlights See through Rain and Snow

Software could make it easier to see in difficult driving conditions.

A prototype headlight system can detect raindrops or snow streaks and “dis-illuminate” them, thereby increasing visibility on the road ahead.

The system uses a digital projector to illuminate raindrops for several milliseconds while a camera mounted on the side of the projector captures each raindrop’s location; software predicts where those raindrops will fall within the driver’s field of view. Light rays from the headlight that would normally hit the raindrop are automatically switched off, reducing glare and leaving only the beams of light which travel uninterrupted in between the falling drops.

The system’s operating range is three to four meters in front of the projector—the “critical range” at which glare is most distracting, according to tests conducted using a Toyota Prius.

The system was developed by Carnegie Mellon computer science professor Srinivasa Narasimhan, along with several others. Narasimhan presented his findings in a talk at Microsoft Research and at Research@Intel 2012.

The researchers simulated different car speeds and rainfall intensity in the laboratory by varying the speed at which simulated rain streaks—using actual water propagated in front of the projector—shot past the screen. The system could reliably make rain streaks invisible at low speeds and still increase visibility at higher speeds by dimming some of the rain.

In severe thunderstorm rain, the accuracy is 70 percent at 30 kilometers per hour and 15 to 20 percent at 100 kilometers an hour; that’s how much of the rain is removed from view. Because water in a heavy rain is only 2 to 3 percent of the air volume, the rain can be filtered by dimming the headlights by just a few percent.

Substituting the hardware for a bigger and better camera would improve the system but increase its size and cost. However, making the system fast enough to reduce even more rain glare at highway speeds is important, because that’s where there’s greater risk for a catastrophic crash, says Narasimhan. He believes the experiments to date show that the idea is feasible, but notes that it will be necessary to account for the effects of car movement before the system can be used in the real world.

Kent Larson, who leads the CityCar project at MIT’s Media Lab, says the headlight system is another advance toward making vehicles more autonomous. “Eventually it won’t matter whether you have your vision obscured,” he says, because the car will be doing the driving on its own.

Keep Reading

Most Popular

wet market selling fish
wet market selling fish

This scientist now believes covid started in Wuhan’s wet market. Here’s why.

How a veteran virologist found fresh evidence to back up the theory that covid jumped from animals to humans in a notorious Chinese market—rather than emerged from a lab leak.

light and shadow on floor
light and shadow on floor

How Facebook and Google fund global misinformation

The tech giants are paying millions of dollars to the operators of clickbait pages, bankrolling the deterioration of information ecosystems around the world.

masked travellers at Heathrow airport
masked travellers at Heathrow airport

We still don’t know enough about the omicron variant to panic

The variant has caused alarm and immediate border shutdowns—but we still don't know how it will respond to vaccines.

This new startup has built a record-breaking 256-qubit quantum computer

QuEra Computing, launched by physicists at Harvard and MIT, is trying a different quantum approach to tackle impossibly hard computational tasks.

Stay connected

Illustration by Rose WongIllustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at customer-service@technologyreview.com with a list of newsletters you’d like to receive.