Tesla Has Found a Use for Lasers—Cleaning Glass

Elon Musk may not want lidar scanners anywhere near his cars, but at least somebody in his employ believes that lasers can help Tesla cars see the world around them. Not by firing photons and measuring how long they take to return, but by blasting away grime that might block the view of the cameras at the core of the electric automaker’s Autopilot system.

A newly published patent application, for which Tesla filed in May, describes the “pulsed laser cleaning of debris” that tends to gather on car windshields and solar panels, both of which Tesla has an interest in keeping Mary Poppins–level spotless. Letting dirt and bird droppings accumulate on a Solar Glass Roof is likely to hobble its energy output. And along with blocking a human driver’s line of sight, a dirty windshield is a problem for the Autopilot cameras that pick out lane lines, and on which Tesla is relying to someday enable “full self-driving.” According to the patent, Tesla is also interested in using a laser system to knock the mess off the camera lenses themselves.

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While windshield wipers may do the job for most people, Tesla’s patent application notes that the process of scrubbing away grime and letting the glass dry results in “unproductive time,” and that the chemicals in wiper fluid could damage a camera’s electronics. Using a laser to burn off any unwanted muck, the patent argues, would be faster and more likely to keep everything working as intended.

Now, the act of filing for a patent doesn’t indicate Tesla is serious about this idea, or anywhere near putting it into production cars. (Tesla spokespeople did not reply to questions about its intentions.) But the concept here is sound. Carnegie Mellon has produced an award-winning robot that uses lasers to strip the paint off of fighter jets, saving the Air Force from using chemical paint removers. Researchers have considered using lasers to clean stained glass and restore paintings.

The key to any of these efforts is calibrating the power of the laser, so you’ve got the right balance between a (mostly) harmless laser pointer and Auric Goldfinger’s favorite toy. Tesla would need something strong enough to irradiate grime into oblivion, but not so powerful that it messes with the glass underneath or the human on the other side of it. The upside to dealing with glass is that it effectively dilutes the power of a laser, limiting the risk of damage, says Tom Hausken, a senior adviser with the Optical Society, an industry group. As for knowing when and where to direct its beam, Tesla’s patent says it could use image processing techniques to figure out where the dirt is.

But making this kind of system work on a moving car isn’t likely to be practical. Lasers may work well in controlled settings, like laboratories and factories, but they haven’t been developed with automotive standards in mind. Putting one on a car would mean demanding it be able to keep working for a decade or more, over tens of thousands of miles, all while plowing through potholes and suffering through rain, snow, and hail. Power consumption might be an issue, especially on an electric car with a range limited by its battery. So could size. “I’m not sure you could get one powerful enough that’s not huge,” Hausken says.

“In principle it’s possible,” says Tony Hoult, who spent his career in laser applications, including a 20-year stint with IPG Photonics, before retiring last year. “But it’s a long way off in reality.” The real barrier, he says, would be cost. This kind of work would require a laser that fires pulses at an ultrahigh rate. “They are still very expensive,” Hoult says. They’re also power hungry, and inefficient. And for any automaker, everything that makes a car more expensive or less efficient can mean cutting an already slim profit margin.

If these criticisms sound familiar, it could be that you’ve heard Musk explain why he doesn’t want lidar in his vehicles. He believes that old-fashioned cameras, running powerful software, are the key to making a car drive itself. Keeping them clean, though, might require something with a bit more zap.

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