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How Laser Headlights Work | Hackaday

When thinking about the further march of automotive technology, headlights are usually not the first thing that comes to mind. Engines, fuel efficiency and switching to electricity are more ahead of us. However, this does not mean that there are not thousands of engineers around the world who work to improve the state of the art in automotive lighting every day.

Sealed headlights have given way to a more modern design as regulations have been loosened as bulbs have shifted from ordinary halogens to xenon HIDs and more recently LEDs. Now on the stage is a new technology with lasers!

Laser headlights ?!

BWM’s prototype laser headlights are being tested.

The first image recalled with the phrase “laser headlights” is that of laser beams firing from the front of the car. Obviously, the coherent rays of monochromatic light would make low lighting outside a very specific place at a considerable distance. Fortunately, laser headlights don’t work that way at all.

Instead, the laser headlamps consist of one or more solid-state laser diodes mounted in the headlamp. These blue lasers emit yellow phosphorus, similar to that used in white LEDs. This produces a powerful, vibrant white light that can then be repelled by reflectors and off-road headlights. Laser headlights built in this way have several advantages. They are more energy efficient than LEDs that emit the same amount of light, while also being more efficient than space.

BWM’s futuristic i8 was one of the first vehicles to be supplied with laser headlight technology.

Laser headlights are still emerging technology, which so far appears in only a few BMWs, Audi and other selected vehicles. BMW technology has been developed in partnership with OSRAM lighting specialists. In practice, a simple LED low beam lamp is used, and the laser is used to create an incredibly bright and focused spot used for high beams. This can provide lighting 600 meters in front of the car, twice as much as conventional LED high beams. The lights use Indian gallium nitride diode lasers, which were originally used in projectors with power levels above 1 watt. One of the challenges in implementing such technology in the automotive environment is the need for it to operate at extreme temperatures. While research lasers and laser pointers can be used mainly at typical room temperatures, car headlights should be able to withstand anything from 40 degrees below zero to 50 degrees C. Fortunately, the high efficiency of the laser means that there is no huge heat output from its to complicate matters further. Other engineering challenges include adapting the optics package to the rough and low-vibration environment found in automotive applications. It is also important to ensure, as with any such device, that the end user cannot be exposed to harmful laser radiation in the event of an accident or malfunction.

Destruction of the laser headlight

Marketing image showing the construction of a spare LED / laser headlight. We would take the laser power with a grain – it is difficult to imagine a 10 W laser that shines directly on some small LEDs without melting a hole through the board for a short time.

A reserve market with delightfully innovative designs also emerged. Combined laser / LED headlights are easily available on Alibaba, designed as a drop in the replacement of projector lamps on existing vehicles. They often use a low-beam LED and a long-beam combined LED / laser, where the laser diode fires directly at the phosphor LED to excite it further instead of using its own. These devices are often also available with fan cooling to keep the laser and LEDs below their maximum operating temperature. Such developments are exciting, although it is important to pay attention to the operation of unknown headlights for spare parts. Many “upgrades” of LED spare headlights fail when it comes to real results and there is no reason to believe that hybrid LED / laser designs will be different. We would like to submit a selection of these parts complete IIHS testing protocol, but this unfortunately exceeds the scope (and budget!) of this article.

However, [mikeselectricstuff] has laid hands on both BMW and spare parts, knocking them all down in his workshop to see what makes them curl. The differences are many when exposed on the bench. The AliExpress part is relatively simple, connected no differently than a regular headlight. Interestingly, however, the long-beam laser circuit operates continuously in these parts. To prevent the other road users from being blinded, a shutter is closed to block the light moving away from the solenoid when the driver switches on the high beam switch.

When the spare part is just outside the left field, BMW’s design is something else entirely. Modern headlights are connected to multiple connectors and over 30 wires, with much of the driver’s electronics living in an external controller. Much of this is to drive the various LEDs and stepper motors to turn the headlights when driving. However, laser mounting has its own complexities. Inside are built-in dual light sensors to monitor the laser beam and a special metal blocking arm is located just in front of the diode, presumably to stop the laser light from leaving the headlight in case the phosphor coating burns out. It is really wild to look inside the headlight of a modern luxury car and see how far we have come from the old days of simple sealed beams.

Costs versus productivity

Despite the available efficiency, the technology remains expensive. After all, high-power laser diodes are not cheap. However, as technology flows to lower-end models, we will probably see how economies of scale change for the better. In fact, if national authorities start demanding higher quality headlights as a standard, we could see that laser headlights are becoming the norm, not an expensive luxury. The technology can of course also be applied to home and commercial lighting – although we suspect that the potential gains are limited enough that LED lighting will remain the norm for some time.

The high light output of the laser headlights in a compact package allows engineers more freedom in designing the front end of a car.

As of now, much of the appeal of the new technology has to do with the benefits of packaging, which allow automotive designers more freedom around the headlight area. Such concerns are a less important factor when it comes to lighting fixtures in the home or office, or even in lower-end cars. Nevertheless, this is an exciting new application for lasers and one that we will certainly see in the future.

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