For the first time in a production car, LEDs are being used as low- and high-beam headlamps, in addition to daytime running lights. The LED headlamps in the new Audi A8 are electronically controlled as well, allowing individual LEDs to be lit as needed, for example to illuminate peripherally during cornering. The LEDs (from Osram Opto Semiconductors) handle special lighting functions such as all-weather lighting.
Typical light levels achieved for each LED chip (with up to five chips in the headlamp) are 160 lm at 700 mA. Depending on the variant and operating current, values between 125 lm and 1100 lm are achievable. With its scalable brightness, the headlamp is used for all headlamp functions, including as fog lamps and daytime running lights. The operating life of the LEDs is at least as long as that of the vehicle, making lamp replacements unnecessary.
"LEDs have left the niche market of limited edition and luxury vehicles and have arrived successfully in volume production," says Peter Knittl, LED automotive director at OSRAM Opto Semiconductors. "As they already meet all the requirements of modern automobile lighting and are setting new standards in many respects, LEDs are perfectly suited to mass market use."
According to Osram, the headlamp LEDs fitted in the A8 produce a light with a color temperature similar to daylight, which enhances perceptions of contrast and is less tiring. (Ordinary high-intensity-discharge car headlamps provide a light that is brighter than that of the older incandescent headlamps, but can have a bluish cast that wears on the driver after awhile.)
The future of vehicle lighting
Because of LED technology, headlamps are evolving from a mechanical component to an electronic module, the operation of which is linked to the vehicle's electronic system, says Osram. For a glare-free full beam, for example, data from the navigation system and information from a light-based driver-assistance system are combined, allowing the lighting system to intelligently illuminate only the required parts of the road when cornering or in oncoming traffic. LED arrays play an important role here--depending on the lighting function, individual LED pixels can be switched on or off, enabling light to adjust precisely to various conditions.