Pure Light Technology
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Posted 22 August 2007 - 04:03 PM
Since 1992, red LEDs have been used increasingly for high-level brake lights, as well for tail lights and regular brake lights. Audi became the first manufacturer to feature peripheral white LEDs as daytime running lights, first on the Audi A8 W12 in 2004 and then on the Audi S6, Audi R8 and Audi A5/S5 from 2006.
Audi is now premiering the first and only headlight unit in the world to deploy LEDs for all of the front lighting functions. Apart from the daytime running lights, these functions comprise the turn signals and the dipped beam and main beam headlights. Various groups of LEDs, known as arrays, produce the correct light distribution and brightness. Each headlight unit has a total of 54 LED light sources.
The outstanding benefits of LED technology include its low energy consumption (50 watts for the dipped beam headlights, 6 watts for the daytime running lights), a colour that is similar to daylight for enhanced contrast and more pleasant visual perception, the non-wearing design, lower voltage requirements, compact dimensions and the increased freedom of design.
A special permit from the EU has paved the way for incorporating front-lighting LED technology into series production ahead of schedule. This is because the corresponding EU regulation is not expected to come into force before 2008. Audi is a founding member of the working party that was set up in 2003 to bring about speedy approval for advanced and powerful lighting technology.
Innovations in the field of lighting technology are often based on the development of new light sources. Halogen bulbs were followed by xenon headlights, which were subsequently expanded to include cornering and static turning lights. Thanks to the rapid advances being made in LED technology, it will soon be possible to reproduce the same functions with these semiconductor elements too.
Each light unit consists of a housing, a chip or chip array, a circuit board and a heat sink. Electric ventilators ensure effective heat dissipation and also defrost the headlight units.
The LED headlight that will in future be available as an option for the Audi R8 is made up of the following components: LED dipped beam headlights as the primary function. Here, basic light distribution is taken care of by LED arrays, each consisting of four chips, which shine out of free-form reflectors. A further three two-chip LED arrays for light in the region of the light-dark boundary and for the headlight range are located behind the lens. Directly adjacent to this is the main beam headlight comprising one four-chip LED array inside each of the two reflector shells. The 24 white LEDs for the daytime running lights are distinctively positioned along the bottom edge of the headlight unit, giving it a three-dimensional and sophisticated appearance.
The turn signal with its eight yellow high-brightness LEDs is placed on the top edge of the headlight unit pointing towards the single-frame grille, where it combines with the strip of LED daytime running lights to form a frame around the headlight.
LED technology in Audi concept studies:
As long ago as the start of 2003 that Audi first unveiled an operational, slat-shaped LED fog light in its Pikes Peak show car at the Detroit Motor Show. An initial concept for an all-LED headlight was presented in the Audi Nuvolari quattro at the Geneva Motor Show in that same year, and in September the Le Mans quattro turned up on the eve of the Frankfurt Motor Show with LED headlights. The dipped beam light distribution already met the statutory requirements at this point. A fully functional LED headlight with lenses made from aluminium tools was featured on the allroad quattro concept car back in 2005. The Shooting Brake concept car then showcased an LED headlight with a bionic design, whose form resembled a pine cone. This same basic idea has now been transferred to the new series-production solution for the R8. The Audi Q7 V12 TDI (Detroit 2007) has already provided a preview of the next generation.
Audi Technology ABC
LED: light-emitting diode. Semiconductor light source which emits cold light at low voltages of 3 to 4 volts. The revolutionary new LED arrays in the Audi headlight produce a luminous flux of 400 lumen at a current strength of 1 A. Such luminous efficiency is unprecedented for LEDs.
Lumen: the unit of luminous flux. Describes the luminous power emitted by a light source.
Source: Audi AG
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