It sounds like something out of a James Bond movie, or Dr. Evil demanding "sharks with frickin' laser beams attached to their heads," but BMW is actually developing lasers for use in headlights. The company sees lasers as the next step after LED headlights.
BMW says the key advantage to lasers are their efficiency. Where LEDs generate 100 lumens per watt, lasers generate 170 lumens per watt. When used in an electric car, laser headlights would draw less energy from the battery.
To make lasers safe for use in headlights, BMW filters the lights through a fluorescent phosphor material. That step changes the color from blue to white and lessens any harmful effects to that of standard LED headlights.
The use of laser headlights also has implications for car design. Each laser diode is only 10 microns in width, substantially smaller than the 1-millimeter-square LEDs used in car headlights today. BMW said in its announcement that its designers have no plans to reduce the surface area of the headlights on its cars, because that is an important styling cue.
But the tiny size of the lasers open up a lot of possibilities. Instead of a large, round piece of glass, a laser headlight could shine through the cross pieces of the car's grille, and so remain hidden when not in use. The traditional dual-headlight configuration would also no longer be necessary, as a row of laser diodes could peek out from the front edge of the hood.
As laser light is a coherent beam, it can be precisely shaped, and also changed at will. Instead of a separate high-beam lamp, lasers can be computer controlled to form a low-beam or high-beam pattern.
BMW mentions a few existing active headlight technologies, such as adaptive headlights, which use the steering-wheel position to illuminate corners, and its High Beam Assistant, which senses oncoming cars and changes the light pattern so as not to blind other drivers. Laser headlights could easily be programmed to handle these features.
Although BMW's laser headlights are still a few years out, the company is developing them for its i8 hybrid.