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Cooley On Cars
Car Tech 101: Shine a light on headlight technologyBrian Cooley reveals the technology of headlights, from where they've been to where they're going.
-First, a sad little history lesson. The United States has always been dead last in new headlight technology, not 'cause we're stupid but because how our regulations have been. U.S. vehicle regulations forever didn't allow designers to use new light sources, new ways of shaping the light, didn't even allow them to use covered fared-in headlights long after Asian and European manufacturers were allowed to do so. We've always been in the dark ages here. What we had were these, sealed beam headlights; basically glorified flashlight bulbs, if you ask me. You either had a pair of 7's or 4, 5's and that was it. Things have changed. Okay. First off, HID or high-intensity discharge, this is kind of a general term for lights that use as a source of illumination, an arc instead of a burning filament, the way sealed beam headlights did. Frankly, those old sealed beams aren't a whole lot different than burning a candle. More specifically, HIDs are usually xenon headlights. That means they have a xenon gas-filled capsule which the gas is being excited by a couple of nodes, electrical nodes, passing very high voltage across a gap. You'll see a sticker off under the hood showing you a high-voltage warning. Bi-xenon simply means that xenon arc technology is used for both low and high beams. LED is the newest headlight tech in production, though only on a few cars still. LEDs offer strong though not the highest light output, but combine that with the lowest power consumption and the greatest flexibility in design. You can style them into almost any surface on a car. But LED light output is quite sensitive to swings in temperature. That's a problem on the road. So, this helps make them complicated to engineer and part of why LED headlights remain pricey. They're $1600 extra on an Audi A8, for example. Laser headlights were coming if you believe BMW. I'm pleased to report this will not be like mounting a couple of huge laser cat toys on the front of your car. Instead, the lasers actually point back at a set of tiny mirrors on the housing that then reflect that laser light out on the road. The benefits here are incredible precision and flexibility of brightness and beam shape, and reportedly, even lower power consumption than LED. And yes, like the lasers at a 70's rock concert, these can project shapes in the air, like a warning triangle near your car when it's disabled. The first big change in beam shaping happened in the 80's with lenses. Old sealed beams used faceted lenses on the front to shape the beam. New technologies began to rely on a faceted reflector behind the bulb. You can spot the difference right away by a clear lens on the front that basically just keeps dirt and water out. Headlight leveling became common soon after and it can be done either automatically or via a simple manual system with a spin wheel. Either way, it's meant to compensate for vehicle loading that tends to cast the headlights up into the sky. Adaptive or steerable front headlights maintain direction of the light where your steering wheel is pointed. This goes back to early [unk] and even the Tucker, though with limited success until modern technology got rid of the motors and linkages they used to use and dropped in more reliable modern actuators about 10 years ago. Another beam-shaping tech you can easily spot is a projector lens, very prominent on a lot of Acura cars, for example. This plays as a convex eyeball-looking lens in front of the light source to throw the light aided by a mechanical shield between the lens and the ball that moves up and down to change the cutoff between high and low-beam. And Audi is about to roll out matrix-beam headlights that would use addressable LED arrays to send high-beam light all over the road all the time except making carve outs in the beam when it detects oncoming traffic. So, no more separate low and high-beam at all. Europeans will get this $3000-option first; Americans may have to wait a while because of a decades-old law that says headlights in this country must have high and low-beam modes. And generally, there's a big discussion on the car business now about defaulting all cars to high-beam and using low-beam as the conditional mode instead of vice-versa, the way it is today. Okay. Bottom line. Now, I assume [unk] of car tech these days, headlight technology is becoming more and more the domain of the carmaker and less something you're gonna graft on later using after-market parts. One notable exception, though, are high-intensity discharge xenon kits. There are a ton of those out there you might try retrofitting to your car. Be careful on the install. They generate some wicked voltage. But in terms of things like steerable headlights, LED headlights, laser headlights, obviously, you're not gonna install those on your existing car. You're gonna get them on a car when you buy it.