By on July 6, 2012

The problem with driving at night in the raining or snowing conditions is that your headlights work too well. They light up the rain and snow as much as they illuminate the road ahead, sometimes more so. In a novel approach using cameras, computers and DLP projectors to replace conventional headlight bulbs, researchers at Carnegie Mellon University have developed a “smart” headlight system that essentially shines light between the rain drops.

It turns out that less really can be more, at least in terms of night driving. By selectively reducing the amount of light projected, by not shining light on the computer predicted path of the rain drops or snow flakes as they enter the critical 3-5 meter space in front of the driver, there is significantly reduced glare.

Theoretically in a perfect system with minimal latency, illuminating 100% of rain drops would come at a cost of only a 2% reduction in total light projected. Precipitation is only a small fraction of the total visual field. So far in lab tests with real water drops falling at normal precipitation levels and slow (30KPH) travel speeds, they can reduce the visibility of rain almost 70% at a cost of only 5% loss of light. The system is less efficient with snowflakes, because they are larger and move more slowly, so there’s about about 15% loss of light, but it can still keep from illuminating more than 60% of the snow. At higher speeds it’s less efficient but lead researcher Srinivasa Narasimhan says that continued development for highway speed use is worthwhile, while stressing that the current system cannot account for wind, turbulence and that it needs to be more compact. Though the researchers stress the data capture and processing parts of the system, it couldn’t work without a DLP projector, one of our age’s unappreciated wonders. The microminiature mirror array in a DLP device can be precisely controlled as to where it shines light.

Ronnie Schreiber edits Cars In Depth, a realistic perspective on cars & car culture and the original 3D car site. If you found this post worthwhile, you can dig deeper at Cars In Depth. If the 3D thing freaks you out, don’t worry, all the photo and video players in use at the site have mono options. Thanks for reading– RJS

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12 Comments on “Carnegie Mellon Researchers Invent Smart Headlights That “See Through” Rain, Snow...”


  • avatar
    Advance_92

    That’s a neat idea but I can’t imagine how to collect the data needed to constantly adjust the headlights against different speeds, gusts and so on. And to crown it all it won’t help much unless people change their wiper blades more than once every two years and know how to set the HVAC to keep the windows clear.

  • avatar

    Science, is there anything it can’t do?

  • avatar
    burgersandbeer

    How close are they to actually mounting this in a vehicle?

    It sounds like a great development, though probably not cheap. I’m also interested in how a micro-miniature mirror array would hold up in an automotive application. Maybe DLP has many more uses than I realize, but the first thing that comes to mind when I hear that acronym is TVs – a far less physically demanding environment.

    Some people complain of headaches when viewing a DLP-based TV; I wonder if that will be a problem here as well.

    • 0 avatar
      Luke42

      This is a lab experiment using a cart full of expensive equipment andconstantly attended to by an engineering graduate student.

      It’s nowhere near ready to be on an actual vehicle, unless you have room for a laptop, a projector, a bunch of sensors/cameras and said graduate student during your commute.

      But its still very cool, and could be developed into a real product. But, for that to happen, there’s probably a lot of lab work that needs to be done – and then some company needs to pick up the idea and make a real mass-produced product backed by a real business.

      None of this is insurmountable. Doing the handoff to the commercial folks is a process that universities give a lot of thought to (though sometimes f)for the wrong reasons), and real tech leaps this divide all of the time.

  • avatar
    jberger

    DLP is incredibly robust as a platform, it’s essentially a solid state platform with current tech.
    I have a 1.3 million mirror demo chip on my desk, the entire package (die, mirrors, glass, etc.) is about the size of a large stamp. This demo chip is about 5 years old, the newer sets are much smaller, they can build them into cell phones now.

    http://www.techradar.com/news/phone-and-communications/mobile-phones/hands-on-samsung-galaxy-beam-review-1067408

    There would be no rainbow effect because this system would not need any spinning color wheel.

    Combine it with a LED Lamp and they could shrink the packaging down to a very small unit on the projection side. HID’s are not cheap, so the LED/DLP side of the package would probably be cheaper than HID. Matching light output will be the short term issue.

    The cameras and computers are probably the biggest cost input and with the micro platforms available today, this is probably near term tech if the manufacturers decide it’s worthy.

  • avatar
    Landcrusher

    2% of the visual field? We don’t call that rain here, that’s humidity. :) We mostly draw the line at pain. If it hurts, it’s rain. If not, it’s just sprinkling.

    The real question is whether it will really be worth the complication. Lose a headlight and you will get pulled over. How much faster do you need to drive in the rain to make up for each traffic stop?

  • avatar
    texan01

    I thought they solved it years ago?

    the ’86 Pontiac 6000-STE that I owned had bright yellow foglights from the factory. These coupled with the white headlights were awesome for actually illuminating the road in conditions that the regular headlights couldn’t.

  • avatar
    danwat1234

    Well for now I think i’ll stick with my plug and play 55watt 4500K HID kit. Very bright, works pretty well in the rain with halogen reflectors. Only cost $70 with a lifetime warranty.


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