Yes, it seems like we’re forever coming up with new and better ways to cast photons down the road ahead of us. So which ones are best, which are pointless, and which are only around so you can tell people your car has frickin’ laser beams in its eyes?

But more than that, headlights have become a kind of functional fashion statement — a "look at me" way of telling the world we’ve got the latest and greatest tech under the hood. It should come as no surprise then that the people who specialize in high-tech and high speed (the Germans) have provided us with the majority of headlight advances over the years; Bosch, specifically, has become a name brand in seeing where you’re going.

It’s been a long, dark road since the earliest days of car lighting, when the best you could hope for was a decent gas lamp that wouldn’t blow up when lit. Of course, back then, the weak glow of a flame in a jar was perfectly adequate for travel on dirt horse tracks at trotting speed. Since then, cars have gotten a lot faster, but human reaction time has remained about the same. That’s necessitated a whole new generation of lights to see further down the road and give us time to react to hyperspeed problems.

Incandescent and Halogen

Honestly, Incandescent Lights (aka "sealed beam lights") probably don’t bear mentioning at all unless you’re looking to retrofit a classic car. These bulb types are the very oldest around, and are effectively just heavy-duty versions of the incandescent light bulbs in your house. They use a tungsten filament suspended in a vacuum; electricity passes through the wire, causes it to heat up and glow, and the vacuum in the bulb keeps the wire from instantly oxidizing and breaking.

Fine enough if you've got a classic car and you want to keep the standard lights, but definitely the worst of the bunch out there.

Those old sealed-beam lights worked reasonably well for decades, but they were always hot, inefficient, and cast what we would consider today a weak and sickly yellowish beam into the intermediate distance. Fine enough if you’ve got a classic car and you want to keep the standard lights, but definitely the worst of the bunch out there.

Halogen bulbs are an improvement on the standard incandescent, in that they use halogen gas instead of a vacuum inside the tube. In point of fact, the functional part of a halogen bulb (the filament) is no bigger than that of a sealed beam headlight, but it uses a much smaller gas tube and a smaller volume of gas to contain the heat.

The halogens are actually a group of gases, including flourine, chlorine, bromine and iodide. Halogen lights use a combination of iodide and bromine. These gases keep the filament from thinning and breaking, and reduce blackening on the inside of the bulb. That allows the filament to burn much hotter, and thus produce more light. Halogens typically run around 2,500 degrees, which would be hot enough to melt aluminum if the filament came into direct contact with it.

Halogens are the most common type of bulb in use today, and they work quite well for most applications. They’re cheap, bright, fairly long lasting and dimmable. They’re also small and easy to replace — unlike those huge old sealed beams, with their integrated lenses and reflectors.

On the downside, the light they cast is slightly yellowish in color, so it doesn’t cast as far down the road given the bulb’s brightness and power consumption. That’s actually not a bad thing in the fog, since pure white light will bounce back more of a glare and limit visibility. So halogens might have a slight advantage there. But otherwise, they do leave something to be desired in the vision department.

Still, not a bad choice if all you’re looking for is a cheap bulb that will let you see where you’re going.

HID, aka "Xenon," "Plasma" or "Arc" Headlights

These lights debuted on the BMW 7 Series in 1991, and they’ve been a source of controversy ever since. Unlike halogens and sealed-beam lights, HID bulbs don’t use a filament of any kind. They’re technically what’s known as "metal halide lamps," which are quite popular as grow lights for indoor greenhouses. They’re also related to the street lights in front of your house.

These headlights pass a very high voltage electrical arc in between two contacts. Inside the bulb is a mixture of gases including xenon and argon, and vaporized metals like mercury and metal halides. The electrical arc actually melts the metal vapors, and turns them into plasma. In principle, this is exactly how a TIG welder (aka "plasma torch") works.

If all you care about it seeing everything there is to see as far away as you can see it, xenons will deliver.

That stream of plasma glows with exactly the same shade of blue-white brilliance that you’d normally associate with TIG welders and lightning bolts. A reflector bounces the energy out to the road. Because the light from these lamps is so intense, it offers a lot of versatility in terms of focusing. It can be focused down to a very narrow beam extending way out in front of the car, or broadened to fill the area directly ahead.

On the plus side, these bulbs very efficiently produce huge amounts of light in the blue-white spectrum. These longer wavelengths travel farther and scatter less than yellower wavelengths, so offer great potential for vision well down the road, and great definition directly ahead of the car. From a purely functional perspective, as a driver, arc lights are still one of the best things going. Because they have no filament to burn out, arc lights will also usually last a lot longer than halogens.

But there are several downsides. First, these lights take several seconds to strike a spark, warm up and come to full brightness. So they’re slow to come on, and can’t be flashes on and off quickly. And the fact that they do put out huge quantities of highly focused blue-white light makes them more than a little irritating to other drivers. Light in this spectrum kills a person’s night vision faster than any other; so not only will a set of xenons glare oncoming drivers a mile down the road, they’ll literally blind them to anything dimmer. Including the red taillights of vehicles ahead.

As a corollary to that, it’s also worth noting that these bulbs will kill your night vision as well. So, while anything directly in your headlight beams will be bright as day, everything else will wind up pitch black. Using a set of xenons is like looking down a very long, black tube where you can see everything ahead of you perfectly — but only the things directly ahead of you. That could become a serious problem while checking mirrors, blind spots and oncoming intersections, and while navigating parking lots.

So in terms of raw performance, as instruments of pure lighting, it’s hard to beat HID headlights. If all you care about is seeing everything there is to see as far away as you can see it, xenons will deliver. They do seem to do everything that you’d want a headlight to do, perfectly. But that perfection does come with a few nasty side effects for you and everyone else on the road.

LED Lights

LED lights, as many know, work on a scientific principle called "magic." Electricity goes in, light comes out. Nobody knows why. They’re almost as big a mystery as the tides, or magnets. Actually, LEDs work by shooting electrons against positively charged holes in a semiconductor. An electron falling into a hole in a lower energy state releases energy in the form of a photon, which emits from the semiconductor in a process known as "electroluminescence."

See? Magic.

Most cars already use scores of LED lights in dashboards and control indicators — and odds are pretty good you’re reading this on an LED computer screen. So the things are everywhere already, and they have massive potential for car lighting. Sort of for the same reasons they’re used in your computer screen. LEDs are compact, extremely energy efficient, and can turn on and off almost instantly. Just as you might watch a video on your LED-screen computer, manufacturers can use these tiny semiconducters to produce a vast array of patterns, light levels and focuses at nanosecond speed.

Just as you might watch a video on your LED-screen computer, manufacturers can use these tiny semiconducters to produce a vast array of patterns, light levels and focuses at nanosecond speed.

While LEDs themselves run very cool (and thus last practically forever), these headlights as a whole do have heating issues. Because of the high resistance inside the light itself, the base of the emitter chip gets very hot. This means the LED requires some kind of heat sink to keep the diode from melting, and usually a cooling can of some sort. That adds complexity and cost to an already fairly pricey proposition, and adds more heat to an engine bay where heat dissipation is at a premium.

But despite the cooling issues and not-insignificant buy-in cost, LEDs offer some really impressive potential as lighting solutions.

First, they’re tiny, so manufacturers don’t need to build massive headlight buckets to house them. Actually, they don’t need "headlights" at all, since you could just as easily and subtly incorporate LEDs into a car’s bodywork. Granted, that’s not necessarily good news for people who prefer traditional car styling. But, it’s an option, and it does give stylists more flexibility when it comes to head- and taillight shapes, and the positioning of turn signals, reverse lights, parking lights and third brake lights.

The fact that LEDs can be turned on and off so quickly makes them not only ideal for those ancilliary applications, it gives them some potential in terms of active headlights. That is, headlights that can network with radar and laser systems to spotlight pedestrians, focus on problems ahead, or just not blind drivers in oncoming lanes. This kind of instant adaptability makes LEDs one of the go-to solutions for manufacturers looking to up their lighting games without making their cars obnoxious to other drivers.

Finally, speaking of which: LEDs can be made to put out light in any color spectrum. And they’re so energy efficient, they can put out loads of light without relying on blue-white wavelengths to project down the road and back. So they’re just as capable of sending piercing beams of light a mile down the road, without blinding anyone. Including you.

This in itself gives LEDs an almost intangible but important safety edge over HID lights. Now, instead of driving down a black tube, too blind to see what’s on the side of the road, to the side of the car or in your mirrors, you can see everything there is to see. Especially in fog, where the LED’s warmer light spectrum won’t simply glare back in a blinding blue haze.

Add in the LED’s instant adaptability, and you’ve got an almost perfect lighting solution that will probably last the life of the car. Seems like the system of the future, right? Maybe.

But futures have a way of getting here quicker than we expect.

Laser Headlights

I know what you’re thinking: First, Doctor Evil jokes. Second, that BMW and Audi have simply mounted a set of laser cannons to the front of the car, and pointed them down the road. Yes and no.

With their LED systems in production for only a couple years, the Germans are already teaming up to deliver the next big thing in lighting. Laser headlights don’t work by just shooting a high-intensity laser beam down the road; which as anyone who’s ever been nailed in the retina by a delinquent with a laser pointer knows, wouldn’t exactly be the most socially responsible thing. But there’s a way to harness the power of laser light without frying eyeballs.

These kinds of laser lights can to everything an LED can do, but produce {1,000 times} the light using half or two-thirds of the energy of an LED.

This system uses a triad of blue laser beams directed into a small chamber containing yellow phosphorus gas. You’ll recognize this stuff as the substance from which we get the word "phosphorescent," or "glow in the dark." Technically, that’s a misnomer, since phosporus itself glows with "chemiluminescence," or light as the direct result of a current chemical reaction. It doesn’t store light and release it later. The yellow phosphorus in question here is technically impure white phosphorus — which is commonly used in the military for tracer rounds and incendiary bombs. It’s related to the red phosphorus used in match heads, which provides that white flash when you strike the match.

What happens inside of the laser light’s phosphorus chamber isn’t unlike the bright, white flash of a match head or tracer round. Only difference being, the reaction is sustained by the lasers, and captured inside the tiny phosphorus lens chamber.

Technically, then, you’re not actually seeing the light of the lasers; you’re looking at the glowing phosphorus, which gets its energy from the lasers. Kind of takes the thunder out of the thing, doesn’t it?

Laser lights only have two settings "Off" and "Searing brightness of the sun."

But hold onto your hammer, Thor — there is some mighty lightning in this bottle. These kinds of laser lights can to everything an LED can do, but produce 1,000 times the light using half or two-thirds of the energy of an LED. So, even as small as LEDs can be, a laser headlight can be infinitesimally smaller. With these headlights, you could conceivably fit a full-on, high-beam headlight twice as powerful as an LED setup into a hole the size of a pin-head. The single largest component of the system would be the lens used to focus the light — to almost 2,000 feet away.

These lights burn in the 6,500 Kelvin range, or about the same as LEDs and natural daylight. So there’s no wavelength issue insofar as headlights are concerned. They can flash on and off as quick as LEDs, and are just as adaptable in terms of dynamic lighting. However, there’s no expectation they’ll replace LEDs in ancillary applications like turn signals and brake lights.

In fact, they might not replace them at all. LED lights aren’t exactly cheap, but they’re practically bargain basement compared to the 10 grand you’ll spend on a BMW setup. That’s right, $10,000 — for headlights. And as of right now, BMW’s only planning to offer them as options for brights. Laser lights only have two settings "Off" and "Searing brightness of the sun." So right now, they can only work in tandem with more traditional lighting systems.

Aside from an astronomical cost for what are essentially just upgraded brights, laser lights create much more heat than LEDs, require even more cooling, and also...cost 10 thousand freaking dollars!

Still, though, you can’t deny the performance upgrade. If you’re willing to pay for it.

Summary

As it looks right now, LEDs seem to offer the best of all worlds. They’re brighter than halogens, longer lasting and far less obnoxious than xenons, a fraction the price of laser beams, and more versatile than all of them. Over the long run, unless laser lights come down in price ridiculously, it looks like LEDs will wind up taking over the lighting industry. Yes, they are more expensive than regular headlights — even accounting for the fact you’ll probably never have to replace them, they are a more expensive option than traditional bulbs. That’s great for the used-car market, since the original buyer will eat the cost — but nobody gets that used car unless someone’s willing to eat the depreciation first.

At a guess, I’d say lasers will maintain a place in the niche market of super-upscale cars, which is doing swimmingly right now. Later, though...they may wind up rich boys’ toys, along the lines of carbon brakes and titanium shift knobs. LEDs offer such a strong compromise in terms of price, performance and versatility, it’s unlikely we’ll want or need anything better for many years to come. Maybe ever.

But, no matter where we wind up in terms of lighting...at least it beats ye olde gas lamps.