
LED headlamp study: luminous flux equal to xenon
Hella is developing complete headlamps using LED technology as a study provides
information about possible series application from 2008.
Article of 10.03.2005
Lippstadt / Germany, March 2005.The light and electronics
specialist Hella, in cooperation with Volkswagen, has developed an LED headlamp
which achieves low beam, high beam, direction indicator and daytime running
light functions using cutting-edge LED technology only. The LED headlamp is
a study using the VW Golf 5 as an example. It is to provide information about
the performance ability of such systems and also offers the possibility of experiencing
technical challenges in operation in the vehicle. A series solution is expected
for the year 2008.
For the lighting functions, Hella uses both standard LEDs and LED assemblies
especially designed for automotive applications. The light is directed onto
the road with the aid of different optical systems. The most striking part of
the headlamp is formed by seven pentagonal plastic lenses arranged in a honeycomb
pattern. There is a shovel-shaped free-form reflector positioned next to these
which produces the low beam together with four segments of the honeycomb. For
the high beam, the other three segments of the honeycomb are also used. During
the day, all seven segments of the honeycomb form the daytime running light.
There are six standard LEDs arranged in a row beneath the shovel-shaped free-form
reflector for the direction indicator function.
Light emitting diodes as a light source open up completely new possibilities
for headlamp shapes and arrangements. This is made possible by the modular design
as well as the large selection of different optical elements.
From the styling point of view, headlamps for future vehicle generations can
be given a completely new look. The development of white LEDs in particular
is creating application possibilities that would have been inconceivable only
a few years ago. Alongside design aspects, the main reason for the development
of this new headlamp technology is the reduced need for maintenance . The aim
is to develop a headlamp which functions perfectly for the life of the vehicle.
Already, the LED headlamp prototype achieves a level of around 1,000 lumens
luminous flux in the low beam, and has thus reached the level of a xenon headlamp.
The luminous flux necessary for good high beam light cannot yet be attained
on account of the lower luminance of LEDs. Hella's lighting specialists are
convinced, however, that this will soon be achieved in the course of the further
development of LEDs. The technical challenges that need to be solved by then
involve thermal management in particular, as well as the development of new
production processes and optical elements to accompany the LED technology.
In the USA headlamps with LEDs for main lighting functions are already approved
according to the SAE standards valid there. In Europe or rather within the area
of validity of ECE regulations, approval can be expected by 2008. Signalling
functions in headlamps (direction indicator, position light and daytime running
light) using LEDs are already approved in both the ECE and SAE regulated regions.
As early as in 2003, Hella achieved the world's first series application of
white LEDs as a combined position and daytime running light in the headlamp
of the Audi A8 W12. In the rear signal lamp sector, the company has successfully
been using LEDs as light sources for more than ten years now, in high-mounted
stop lamps, for example, or for tail light, stop light and direction indicator
functions in combination rear lamps, such as in the case of the Volkswagen Golf
Plus.
Hella has also been using LEDs for single-function lamps and combination rear
lamps in the aftermarket and commercial vehicle sectors for quite some time.
Thanks to their long service life, low power consumption and compact design,
LEDs have already become standard for position and side marker functions. These
properties also make LEDs particularly suitable for the current trend towards
daytime running light applications.
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