Press Release
The lighting technology of the future: The multi-talented LED
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LED headlamps as powerful as xenon lamps in the future
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Many advantages such as a long service life and variable light distribution
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Adaptive main-beam control depending on the distance of oncoming traffic
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LED brake lights for data transfer to vehicles behind
When the engineers at the Mercedes-Benz Technology Center think about the headlamps of the future, their ideas and concepts primarily tend to focus on three letters of the alphabet: LED.
The future is assured for Light Emitting Diodes, which were discovered in 1907 and put to commercial use for the first time in 1967. Their efficiency is constantly increasing, and in a few years time they will also be candidates as light sources for main and low-beam headlamps. The performance of LEDs has almost doubled in the period between 2004 and 2006, and by 2008 specialists expect their lighting output to be three times the level achieved in 2004.
Development work by automobile specialists focuses primarily on white multi-chip LEDs. It is expected that by 2009/2010 these will have the same output as today’s xenon lamps.
Light-emitting diodes are based on crystalline semiconductors which directly convert electrical power into light. Gallium arsenide and gallium phosphite were the compounds which ushered in the era of the so-called luminescent diodes during the 1960s. Nowadays other crystalline compounds are also used, and the materials are primarily chosen to influence the colour of the light emitted by the LED.
LED headlamps are of interest to automobile engineers and designers for several reasons: they occupy far less space than conventional bulbs and therefore open up completely new possibilities for the front-end design of future passenger cars. Unlike conventional light sources LEDs only project their light forwards, enabling the installed depth of the headlamp unit to be reduced. LEDs are also insensitive to knocks and impact, and emit a pleasantly coloured light similar to daylight.
Electrical and electronics engineers favour LED headlamps because they require far less energy than conventional bulbs by virtue of their high efficiency. For the same light output, the high-powered LEDs of the future are expected to have only half the power requirement of today’s halogen headlamps. Moreover, the operating life of LEDs is at least 10 000 hours - as long as that of the car itself.
LED arrays: variable light control by non-mechanical means
Lighting arrays create completely new possibilities. These consist of several high-performance LEDs on a circuit board, each of which can be individually activated to control the distribution of light according to the situation. This means that all conceivable lighting functions can be realised purely by electronic means - from dynamic headlamp range control to fog lamps. In future, LEDs will also be able to provide the motorway mode, active light or cornering light functions merely by activating individual diodes. Moving parts such as those currently used for the active light function will no longer be needed.
Main-beam control: continuous dipping for oncoming traffic
In addition, the very rapid response of LEDs allows a new form of adaptive main-beam control which Mercedes engineers are currently testing on the roads. A camera behind the windscreen registers oncoming vehicles and calculates their distance using a computer. An electronic control unit uses this information to dip the main beam as required. In this way technology resolves the conflict of aims between prevention of dazzle and the best possible range of visibility. This dynamically adaptive main-beam control prevents oncoming traffic from being dazzled, while ensuring the maximum light yield in any driving situation.
Night view assist: even more effective with LEDs in future
Mercedes engineers expect further benefits from innovative infra-red LEDs, which are also under development at present. These could improve the effectiveness of night view assist even further, for example. This driver support system, which celebrated its world premiere in the new S-Class just a few months ago, is based on an infra-red camera on the windscreen. The wavelengths of LEDs emitting infra-red light can be even more sensitively adapted to the camera than the infra-red lamps used at present. This means that the range of visibility provided by the night view assist of tomorrow will increase by up to 50 percent. The wavelength of the infra-red LEDs can also be modulated, which means that vehicles fitted with night view assist will not dazzle each other when their paths cross.
Brake lights: LED signals for car-to-car communication
LEDs have already been in use as tail and brake lights on Mercedes passenger cars for many years. They make a significant contribution to accident prevention in this role, as LED brake lights reach their maximum brightness around 150 milliseconds faster than conventional bulbs. In practice this small gain in time represents a major safety benefit: during tests in the driving simulator in Berlin operated by the DaimlerChrysler Research department, Mercedes specialists found that the braking distance from a speed of 130 km/h is reduced by around 15 metres if drivers are warned of imminent danger by LED brake lights, enabling them to react more rapidly.
In the future LED brake lights could perform additional tasks which go well beyond their primary lighting function. Mercedes engineers plan to use these rapid light impulses to transmit data at the same time. For example, the light impulses could transmit information about the actual braking deceleration of a vehicle ahead. A sensor in the car behind could receive these data and transfer them to the Brake Assist system, which would then adjust the brake pressure to suit the situation.
Initial tests with this innovative car-to-car communication have shown how rapid and efficient LED brake lights can be: data transfer by light makes it possible to transmit eight megabytes per second over a distance of up to 130 metres. Accordingly LED technology will open up new ways to prevent rear-end collisions.
