Mercedes Intelligent Light System

Mercedes Intelligent Light System

New-generation headlamp technology

February 8, 2006 7:20 AM
Filed Under: German, Mercedes-Benz

Press Release

 

Mercedes-Benz unveils the Intelligent Light System, a new generation of adaptive car headlamps which is now entering series production. These adapt to the prevailing driving and weather conditions, thereby significantly enhancing safety. New lighting functions such as country and motorway light modes increase the driver’s range of visibility by up to 50 metres. The Intelligent Light System also includes the active light and cornering light functions, as well as new, enhanced fog lamps which illuminate the road edges and therefore provide even better orientation when visibility is poor.

The new, intelligent headlamps are a continuation of many years of effort by Mercedes-Benz to make driving safer at night. Despite the lower volume of traffic, the risk of a serious accident is twice as high during the hours of darkness as it is during the daytime.

The lighting system incorporates variably controllable headlamps with five different light functions. Mercedes-Benz plans to combine the Intelligent Light System with the bi-xenon headlamps offered as an option in the E-Class, becoming the first manufacturer to provide its customers with the best lighting technology currently available.

In the E-Class Mercedes-Benz has upgraded its bi-xenon low-beam headlamps with their highly effective, asymmetrical light distribution into a new country mode which illuminates the left-hand edge of the road more widely and brightly. The driver’s range of vision is increased by around ten metres, which gives him better orientation in the dark and allows him to respond more rapidly when other road users cross his path.

Far-reaching: new motorway mode with longer range

From a road speed of 90 km/h the new motorway mode is automatically switched on in two stages: in stage one the output of the xenon lamps is increased from 35 to 38 watts, and in stage two the range of the nearside headlamp is increased when a speed of 110 km/h is reached. The result is a uniform cone of light which illuminates the entire road width to a range of up to 120 metres. At the centre of this cone the driver is able to see around 50 metres further than with conventional low beams, which allows him to recognise vehicles, even at very long distances, and adapt his driving style accordingly.

The enhanced fog lamps, which are also part of the new Intelligent Light System, provide better orientation in adverse weather conditions. If visibility becomes less than 50 metres, the vehicle speed falls below 70 km/h and the driver switches on the rear fog lamp, the left bi-xenon headlamp of the E-Class swivels outwards by eight degrees and, at the same time, lowers the cone of light. This illuminates the nearside of the road more efficiently, while the wider beam reduces backglare in fog. The enhanced fog lamps remain switched on up to a speed of 100 km/h.

The active light function, which Mercedes-Benz first offered in the E-Class in spring 2003, has been developed further by the engineers in Sindelfingen. The swivel angle of the headlamps has been increased from 12 to 15 degrees, providing even better illumination on tight bends. With the active light function, which operates at both low beam and main beam, the bi-xenon headlamps automatically follow the steering angle. Road illumination is improved by up to 90 percent when negotiating bends.

The Intelligent Light System also includes the cornering light function, in which one of the two fog lamps is automatically switched on when the driver operates an indicator or turns the steering wheel. As a result, the range of side visibility ahead of the vehicle is increased by around 30 metres. The cornering light function is activated up to a speed of 40 km/h.

Interior: ambient lighting as a safety factor

In addition to the new Intelligent Light System, the Mercedes-Benz E-Class also offers a unique lighting concept in the interior: ambient lighting, which provides effective yet discreet and glare-free illumination of the interior for driving at night. The system incorporates light-emitting diodes (LEDs) in the door handle recesses and footwells, as well as special luminous panels in the roof liner. This means that the sense of spaciousness and the high quality of the interior can also be appreciated by night.

The E-Class is the only car in its market segment to feature such a sophisticated and well-conceived lighting concept for the interior. It not only ensures a particularly pleasant interior lighting mood, but also enhances the driver’s operating and perceptive safety during the hours of darkness. This is because the permanent interior lighting lends better visual support to control processes and allows easier recognition of the switch arrays in the centre console. It also reduces the need for the eyes to adapt to the difference in brightness between the vehicle interior and the road, which means less strain on the eyes and therefore less rapid fatigue.

Furthermore, a pleasant "visual atmosphere" makes a major contribution to driver-fitness safety because the ambient lighting has a psychologically and biologically stimulating effect on the driver and therefore improves his performance potential.

Outlook: high-performance LEDs for the car headlamps of the future

In the future Mercedes engineers plan to implement the new lighting functions of the Intelligent Light System with the help of LED headlamps. They expect that in a few years’ time, white multi-chip LEDs will be capable of delivering the same output as today’s xenon lamps.

In addition to a lower space requirement and a very long service life, LEDs have further advantages for vehicle lighting. If several LEDs are connected in series to form arrays, each individual LED can be separately controlled to adapt the light distribution to suit the current driving situation in fractions of a second. This will make lighting functions such as motorway mode, the active light function and the cornering light function possible by purely electronic means.

Moreover, the extremely rapid response of LEDs allows an innovative, adaptive main-beam function which Mercedes engineers are currently testing in practical trials. A camera behind the windscreen registers oncoming vehicles and calculates their distance. 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.

LEDs will also be able to perform additional tasks when used as brake lights. Mercedes engineers plan to use these rapid light signals to transfer data as well. Their light impulses can e.g. provide information about the actual braking deceleration of the vehicle ahead. The Brake Assist system can then use this to adapt the brake pressure to suit the individual situation. In this way the technology of the future can help to prevent rear-end collisions.

 

Intelligent Light System: The right light in any driving situation

The Mercedes-Benz E-Class has been a trailblazer in the field of lighting technology for more than ten years: in 1995 the Saloon was one of the first cars to feature the newly-developed xenon headlamps. These were standard equipment for the AVANTGARDE line and made the striking twin-headlamp look even more interesting. In spring 2002 the E-Class was the world’s first car with the active light function, and in just a few months this Mercedes model series will follow up with the next world premiere in lighting technology – the Intelligent Light System.

The system incorporates no less than five different lighting functions which are configured for typical driving and weather conditions and provide the driver with a significantly longer range of visibility. Accordingly the Intelligent Light System makes a further, important contribution to accident prevention and helps to reduce the high risk of accidents when driving at night.

This new, adaptive lighting technology is made possible by a regulation on the part of the UN Economic Commission for Europe (ECE) which will also apply within the European Union from mid-2006. Mercedes-Benz plans to combine the Intelligent Light System with the bi-xenon headlamps offered as an option in the E-Class, becoming the first manufacturer to provide its customers with the best lighting technology currently available.

Four of these five lighting functions are new in the Mercedes-Benz E-Class. The engineers in Sindelfingen have developed and improved the already familiar and well-proven active light function.

Country mode: better illumination of the road edge

Driving on country roads in the dark is set to become even safer thanks to the new country mode. The ECE/EU directive covering "intelligent car headlamps" will enable low headlamp beams to be distributed in such a way that the left edge of the road is illuminated more brightly and widely than before. The driver’s range of vision is increased by around ten metres, which gives him a good view of both sides of the road, improves orientation and allows him to respond more rapidly when other road users cross his path. In E-Class models equipped with the Intelligent Light System, the new country mode will replace the existing low-beam headlamps.

Motorway mode: up to 60 percent better visibility in two stages

From a speed of 90 km/h the Intelligent Light System activates the new motorway mode and provides the driver with a significantly longer range of visibility than conventional low-beam headlamps. The range of visibility is increased by up to 60 percent.

Motorway mode is automatically activated in two stages: from a road speed of 90 km/h the system first increases the output of the bi-xenon lamps from 35 to 38 watts to provide more lighting intensity, which leads to noticeably better illumination of the road surface and edges. From a speed of 110 km/h the range of the nearside headlamp is also increased, producing a uniform cone of light which illuminates the entire road width to a range of up to 120 metres. This means that vehicles or objects in the distance can be recognised across the entire width of the road, and at the centre of this cone of light the driver is able to see around 50 metres further than with conventional low beams.

Enhanced fog lamps

When visibility is impaired by dense fog, drivers quickly lose their orientation because they can no longer recognise familiar guiding features such as road markings and the black-and-white posts at the road edge. The main task of fog lamps is therefore to project a broad beam and distribute it in such a way that the road edges in particular are well illuminated. This enables drivers to follow the course of the road more easily.

The technology of the Intelligent Light System makes it possible to assist the fog lamps with this important task. To this end the left bi-xenon headlamp of the E-Class swivels outwards by eight degrees and, at the same time, lowers the cone of light. This illuminates the nearside of the road more efficiently, improving the driver’s visibility in this area. At the same time this wider light distribution reduces backglare in foggy conditions.

The new lighting function is automatically activated as soon as the rear fog lamp is switched on if the E-Class is not travelling faster than 70 km/h. The enhanced fog lamp function is automatically switched off when the vehicle speed exceeds 100 km/h.

Active light function: well-proven technology improved even further

The active light function, which Mercedes-Benz first made available in the E-Class at the beginning of 2003, improves road illumination on bends by up to 90 percent. In other words, when taking a sweeping bend with a radius of 190 metres, the active light function enables the driver to see 25 metres further than with conventional low-beam headlamps. This represents a considerable improvement in driving safety. The active light function operates with both the low-beam and main-beam functions.

The electronic control unit of the active light function is integrated into the data network of the E-Class, which continuously provides it with current information about the steering angle, yaw rate and vehicle speed. This allows the bi-xenon modules to follow the driver’s steering wheel movements and pivot sideways in fractions of a second whenever the driver enters a bend.

Mercedes-Benz has improved the technology of the active light function even further, and from mid-2006 the headlamps will be able to pivot by up to 15 degrees when negotiating a bend – three degrees more than at present. This means that tight bends will be illuminated even better than before.

Cornering light function: more safety at junctions

The cornering light function celebrated its premiere in the Mercedes-Benz C, CLS and SLK-Class in 2004. From mid-2006 it will be part of the lighting functions of the new Intelligent Light System in the E-Class, improving safety at junctions and on tight bends through the interaction of the bi-xenon headlamps and the fog lamps in the front bumper.

When the main headlamps are switched on, the cornering light function is automatically activated if the driver operates the indicator or turns the steering wheel at a speed below 40 km/h. The low-beam headlamps and fog lamps then illuminate the side area ahead of the vehicle to a range of around 30 metres at an angle of up to 65 degrees.

When cornering, this lighting function therefore makes road areas visible which would remain in the dark with conventional headlamp technology. In addition the cornering light function remains active even when taking bends slowly at speeds up to 40 km/h, allowing the driver to recognise the road contours more easily.

Technology: rotating cylinders in the bi-xenon modules

The two pivoting bi-xenon modules in the headlamp housings of the E-Class are at the heart of the Intelligent Light System. As before, they operate on the principle of the projection-beam headlamp which focuses the beam through an optical lens. The light of the new, adaptive headlamps must however be precisely directed to achieve the different levels of light distribution. In the headlamps of the E-Class this is done by a rotating cylinder powered by an electric motor. The different lighting functions can be configured by precisely calculated and defined cylinder positions – also for left-hand traffic.

 

Ambient interior lighting: Safety and well-being through lighting

Pleasing contours, soft materials and attractive colours – these are the well-known "ingredients" of good interior design. The same applies to cars. Achieving a tasteful composition creates an atmosphere in which the occupants feel comfortable.

More than ever before, light is now also used as an interior design element in automobiles. Designers and engineers are devoting increasing attention to this medium, and using lighting effects to reinforce the formal expression of the interior and provide the occupants with an even more pleasant stay on board. Moreover, the right lighting can also make a contribution to driving safety. For this reason Mercedes-Benz concerns itself with this subject more intensively than other automobile brands.

While the 1998 S-Class still had individual LEDs to provide discreet points of light on the door handles, in the front footwells and above the centre console, the presentation of the E-Class at the beginning of 2002 marked a change to so-called "ambient interior lighting". This not only includes the indirect illumination of all the major switches and controls, as well as LEDs in the door handle recesses and footwells, but also special luminous panels. These frame the front and rear overhead control units, providing a particularly pleasant lighting mood in the ELEGANCE and AVANTGARDE models, even when on the move. The LED in the interior mirror, which is directed at the centre console, is also part of the ambient lighting scheme.

The diffused light can be dimmed in five stages for the front area, and can be individually adjusted using the keys on the multifunction steering wheel and the central display in the instrument cluster. Passengers in the rear are able to select the brightness of the rear interior lighting by means of two switches in the overhead control unit. In models equipped with the panoramic sliding roof, Mercedes engineers have used the centre division between the areas of glass to accommodate two light panels for the rear.

In this way ambient lighting enhances the interior with a carefully coordinated mixture of diffuse, distributed and localised light when the vehicle is on the move - discreet, dazzle-free and yet effective. This means that the sense of spaciousness and the high quality of the interior can also be appreciated by night.

The E-Class is the only car in its market segment to feature such a sophisticated and well-conceived lighting concept for the interior.

Operation, perception and fitness: light as a safety factor

Around 90 percent of all the important information required to drive a car is taken in by visual means, i.e. via the eyes. This shows how important efficient headlamps are for driving safety. But it also shows how important an intelligently designed interior lighting scheme is. In terms of operating safety, for example: during the hours of darkness the ambient interior lighting in the E-Class provides better visual support for control processes and allows easier recognition of the control switches – especially in the centre console.

Improved perceptive safety is another important benefit: the ambient lighting concept of the E-Class allows the interior lighting to be adjusted to suit the light sources outside the vehicle. Because the interior is discreetly illuminated, there is less need for the eyes to adapt to the difference in brightness between the vehicle interior and the road, which means less strain on the eyes and therefore less rapid fatigue.

And finally a pleasant "visual atmosphere" makes a significant contribution to driver-fitness safety, a development discipline to which Mercedes-Benz attaches particular importance. The aim of driver-fitness safety is to perfect the technology of an automobile to such an extent that it relieves the driver’s workload and maintains or even in some measure improves his driving ability. This enables the driver to pay more attention to the traffic situation and keeps him fit enough to handle critical situations with confidence and control.

Owing to many years of activity in this field, the specialists at DaimlerChrysler Research are aware that in addition to physical fitness, emotional factors such as mood, stress and motivation contribute to driver-fitness safety. These can also be influenced by intelligent lighting design in the interior of a car.

Well-being and alertness: light as a sensory stimulant

From research findings in the field of industrial psychology, automobile developers also know that light not only provides illumination, but can also act as a psychological and biological stimulant to improve driving performance. These findings provide the basis for the interior lighting of the E-Class, although the lighting intensity must out of necessity be much lower than in offices or industrial workshops owing to the special conditions in an automobile. Nonetheless lighting creates the mood, and where light is completely lacking there is a drop in motivation and performance. There is also a biological reason for this: when darkness falls the pineal gland in the human brain releases the sleep hormone melatonin to tell the body that it is night-time. Mercedes-Benz counters this effect with the help of ambient interior lighting, thereby making a contribution to removing a major cause of accidents, namely tiredness.

 

The lighting technology of the future: The multi-talented LED

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.

 

Accident statistics: Night-time accidents particularly serious

Driving is significantly more dangerous when darkness falls than during daylight hours. Although average traffic density falls to around one third in twilight and the hours of darkness, the risk of a fatal accident is twice as great as during the day.

According to the Federal Statistical Office, 27 percent of all serious traffic accidents (involving injuries to people) in Germany in 2004 occurred in twilight and darkness. There were 2431 fatalities, accounting for around 42 percent of all road deaths in that year.

The highest accident risk occurs on country roads, highways and motorways during the hours of darkness, where there were 142 fatalities in twilight and darkness in Germany in 2004. There were 374 fatalities on motorways in twilight and darkness - 54 more than in daylight.

Accident figures in other countries tell a similar story. In the USA, for example, 18 731 or almost 50 percent of all fatal accidents in 2003 occurred in twilight and darkness.

Accident prevention with new headlamp technology

Accident researchers assume that visual perception problems play a part in every second night-time accident. Accordingly they see improved visibility for the driver and easier recognition of other road users as a way to improve traffic safety during the hours of darkness. The new Intelligent Light System with its situation-related headlamp control will make a major contribution to this.

The majority of collisions in the hours of darkness occur because drivers have lost control of their vehicle – frequently because they are unable to recognise the course of the road in time and adjust their speed accordingly. As a result around 54 percent of these vehicles leave the road, and more than one quarter (26 percent) collide with oncoming traffic.

Modern, situation-related headlamp control technology can also help to improve the safety of pedestrians, for according to German accident statistics, more than two thirds of all fatal accidents involving pedestrians occur in twilight or at night.

 

The history of the headlamp: From the candle lamp to motorway mode

A look at the 120-year history of headlamp technology shows the enormous progress made in this field by automobile engineers. Since the large-scale introduction of the first paraboloid bilux headlamps during the 1950s and 60s, there has been an improvement of more than 85 percent in the efficiency of road illumination. While the bilux low-beam headlamp managed a range of around 100 metres (with a lighting output of 1 lux), drivers have a visibility range of more than 180 metres with today’s bi-xenon headlamps. There have been similar improvements in illumination spread, and in this respect bi-xenon headlamps are three times more efficient than bilux systems.

The history of the headlamp begins with the history of the automobile: at the end of the 19th Century, when Gottlieb Daimler and Karl Benz presented the first motor vehicles to the world. Coaches still set the standard: this meant that lanterns with candles were regarded as technically advanced, even though drivers were literally obliged to feel their way by candlelight during the hours of darkness. The logical response of owners was therefore to leave their motor coaches at home when darkness fell.

Nor did officialdom pay much attention to car headlamps in the early years either. In the kingdom of Prussia, a police regulation dated April 15, 1901 (Section 31) merely stated that: "The lanterns must be lit in darkness and in very foggy conditions."

However, the subject of lights took on a very different importance when the first motor races took place. One case in point was Emil Levassor, the winner of the "Paris-Bordeaux-Paris" race in 1895: "My headlamps were unable to withstand the jarring caused by such rapid progress and came loose. I was obliged to have one of them held by my companion. This lack of light was one of the major factors which so delayed my return."

Carbide lamps: 35 litres of gas per hour

The best way to light up the road ahead remained a matter of personal preference. In addition to candles, drivers used petroleum and acetylene lamps to light their way home. Acetylene headlamps – more commonly known as carbide lamps – were seen as very progressive but consumed up to 35 litres of gas per hour. Manufacturers usually installed the necessary gas generator outside, on the running board – not for safety reasons, but because of the unpleasant smell of carbide.

Even in those early years drivers were confronted with a problem which preoccupies the developers of automobile lighting systems to this day: while headlamps were intended to illuminate the road as far as possible, they must not dazzle other road users. To meet this requirement, the designers of acetylene headlamps came up with an idea as early as 1908 whereby the headlamp could be "dipped" by moving the gas flame away from the focal point by means of a lever-operated cable. Despite such technical refinements there was no future for the acetylene lamp, however; cars were becoming increasingly fast and gas-light was simply too inadequate.

Electric lights: powered by a dynamo

The situation was remedied by battery-powered electric lamps, with which Mercedes models were equipped from 1910. Older models by Daimler and Benz were also retrofitted with electric lights in the form of auxiliary headlamps.

This form of vehicle lighting was not without its problems, however. Electrical power was needed to produce light, and the battery was only able to provide this for a short time. Accordingly, electric headlamps only achieved a breakthrough when dynamos were introduced to generate the necessary power.

In 1913 the electrical company Bosch took a logical approach to this aspect and launched the "Bosch Light". This was a complete system which saved customers the trouble of purchasing the headlamp, dynamo and regulator as separate components. Nonetheless there was still a debate whether this modern, electrical solution was superior to the old-style headlamp. The manual "The Modern Automobile", which was regarded as the standard reference work in 1914 Germany, advised a dual strategy where lights were concerned: "Two lamps fed by either petroleum or electricity are essential on the mudguards. These small lamps are quite adequate in city traffic to comply with police regulations, large headlamps would only be a hindrance in city traffic as they dazzle both horses and people. Electric lamps with a switch on the mudguard are effective; there are 4 and 8-volt versions which are connected to one or two batteries. These lamps are not adequate for country journeys at night, however. It is advisable to mount two headlamps on the front of the frame, to the right and left of the radiator, and these are best powered by electricity or compressed acetylene gas carried in steel flasks."

Electric and petroleum/acetylene powered headlamps co-existed until after the First World War. It was not until the 1920s that electrical power proved victorious in automobile engineering – and not only for headlamps.

Low-beam headlamps: practical problems

The pleasure of driving at night was still dampened by an old problem, namely dazzle from oncoming vehicles. There was no lack of attempts to remedy this situation by experimenting with resistors or mounting headlamps in such a way that their beam could be physically dipped, though this system proved unsuitable on wet roads because of strong reflections. Separate pairs of lamps for low and main beam proved more useful.

Numerous lighting regulations issued by local government bodies added to the confusion concerning the best headlamp system. In 1921 the German Ministry of Transport made an attempt to solve the problem at a stroke: permanent low-beam headlamps, which were the norm in the USA, were to become compulsory in Germany. It soon became clear that quite different conditions prevailed in the United States: traffic density and therefore the lighting level in the cities was much greater, and even the major highways of America were lit.

The bilux bulb: the all-in-one solution

In 1924 the lamp specialist Osram finally came up with the solution: the twin-filament bulb which combined low and main beam in one reflector. This generated two beams of different strengths and angles, lighting up the darkness as the so-called bilux lamp. All the famous Mercedes models of the 1930s, such as the SSK, 500 K or the Type 770 "Grand Mercedes", found their way with bilux headlamps after dark.

In 1957 there was another advance in lighting technology: in the legendary 300 SL Roadster, Mercedes-Benz became the first manufacturer to combine low beam, main beam, sidelights and parking lights in a single headlamp unit.

Asymmetric beams: more light for the right-hand edge of the road

In the same year a further novelty provided grounds for lively discussion, namely the asymmetrical low-beam headlamp. Until 1956 a horizontal division between light and dark was prescribed for low beam headlamps in Europe. However this proved to be less than practical because pedestrians or cyclists on the extreme right-hand edge of the road were often overlooked. For this reason engineers developed a new form of asymmetrical light distribution with a light/dark division biased to the right. In 1957 this low-beam lighting was officially sanctioned by the government.

Halogen technology: double the output

Just a few years later there was talk of yet another "new quality of lighting performance". The all-conquering halogen lamp had arrived. As an obvious advantage this retained its high lighting performance throughout its operating life. While vaporised metal from the filament collected on the glass and eventually blackened it in a conventional bulb, the halogen gas filling ensured that vaporised metal would be deposited on the filament again.

Not only did the glass bulb of the halogen lamp remain clear at all times, it was also possible to heat the filament more strongly and thereby obtain better lighting performance. Halogen lamps produce almost twice as much light as conventional bulbs. In 1962 the H1 halogen bulb celebrated its commercial debut in the auxiliary headlamps made by the lighting specialist Hella. Three years later this technology was also introduced in main headlamps: from 1965 a dual-focus reflector system with two H1 bulbs for low and main beam began to compete with the previous bilux lamps.

The breakthrough only came with the twin-filament halogen bulb known as the H4, however. This featured two filaments, the upper filament being shielded to prove the low-beam function. The first main headlamps were equipped with the H4 twin-filament bulb in 1971, foremost among them the Mercedes-Benz 350 SL.

Projection-beam headlamps: light from a lens

But it was not only lighting technology that experienced further development, for there were also great changes in the shape of headlamps and reflectors. At the beginning of the 1960s the first rectangular headlamps began to light up the roads, and in 1983 the projection-beam headlamp signalled more decisive progress. This throws light onto the road surface using the principle of a slide projector, achieving a much higher light output from a smaller surface area. The decisive difference is that the reflector is not a parabolic mirror, but an ellipsoid with three movement axes. This generates a cone of light with a specific focal point very close to the reflector. The conventional lens has been replaced by a convergent lens with an area of a just a few square centimetres, which concentrates the beam of light.

Car designers were excited about this new headlamp technology. Suddenly they were able to design compact, extremely flat headlamps with a heavily inclined lens. Nonetheless these projection-beam headlamps produced a clear light/dark division, uniform light distribution and significantly reduced backglare in fog, rain and snow.

Variable focus technology: computer-designed reflectors

Another automotive highlight occurred in 1995: the Mercedes-Benz E-Class with its striking twin-headlamp look. This not only marked a new styling approach by the Stuttgart brand, but also featured the latest lighting technology. The twin-headlamp design separated the low and main-beam functions, allowing the headlamp reflectors to be optimally configured for their respective tasks.

Modern computer technology enables the high-performance reflectors to be configured for the maximum light yield and optimal light distribution. The computer divides the surface of the reflector into thousands of tiny mirror segments, which it moves around and reshapes until they are in the best possible position. This makes it possible to assign a separate mini-reflector to every point of light striking the road surface. Since the individual, computer-defined reflector segments cannot be defined mathematically, these high-tech systems are referred to as "variable-focus reflectors".

Thanks to variable-focus technology, the usable beam of light by which brightness is measured was far superior to that achieved by conventional headlamps. This was also due to the use of powerful H7 bulbs in place of the previous H4 versions. The dual function of H4 bulbs (low and main beam) required a compromise when using the reflector surface: light for the low beam is only directed at the upper half of the paraboloid reflectors and then reflected. Things are different in the case of modern H7 bulbs: these give off all-round light and the low-beam function is provided by the variable-focus reflector, which is therefore put to full use. As a result the low beam headlamp has a longer range and illuminates the road more uniformly.

Xenon: light from gas

While variable-focus reflectors and H7 bulbs undoubtedly equip modern automobiles very well for night-time driving, even better illumination was provided by an invention which Mercedes-Benz first presented in its F 100 research vehicle in 1991: xenon headlamps with gas discharge lamps. The light source in these quartz glass lamps consists of xenon gas and traces of various metallic salts. By generating a brief impulse of up to 28 000 volts, an electronic ballast creates a plasma arc between the lamp electrodes. This is stabilised at around 85 volts and replaces the filament used in conventional bulbs.

This innovative "gas light", which entered series production in the E-Class in 1995, has very obvious advantages. Most importantly, with a power consumption of only 35 watts the xenon lamp produces twice as much light as a conventional halogen bulb consuming 55 watts. The result is far superior and brighter illumination of the road surface and verges.

Headlamp range control: precise lighting adjustment in any situation

The high efficiency of xenon headlamps requires very precise adjustment, otherwise there is a risk of dazzling oncoming traffic. To counter this effectively, Mercedes engineers developed a sensor-based headlamp range control system which is able to compensate body movements within fractions of a second. Yaw sensors on the axles not only register any downward motion at the rear end when the boot is full, but also dynamic body movements e.g. when braking, then modify the reflector settings.

This dynamic headlamp range control system was one of the numerous technical innovations which first entered series production in the E-Class of 1995. Today it is a standard feature in any Mercedes passenger car equipped with bi-xenon headlamps.

Bi-xenon: one lamp for main and low beam

The next breakthrough in the field of headlamp technology celebrated its world premiere in a Mercedes-Benz: in 1999 the CL-Class Coupés were the world’s first cars with bi-xenon headlamps. Bi-xenon means that headlamps with gas discharge lamps not only provide the low beam function, but are also mainly responsible for the main beam function.

When switching to low beam, a shield is moved across the main beam light and partially obscures it. The previous reflectors are replaced by a projection system in which the light is concentrated by a lens and directly projected onto the road without reflection.

Active light function: a headlamp that pivots to the side

Some years later this innovative bi-xenon technology formed the basis for the new active light function, which entered series production at Mercedes-Benz in spring 2003. Integrating this into the data network of the E-Class made it possible for the headlamps to follow the steering movements of the driver and immediately pivot sideways as the driver enters a bend. The result is an improvement of up to 90 percent in road illumination: while the area illuminated by low-beam headlamps is usually 30 metres when entering a bend with a radius of 190 metres, the new headlamp technology extends this by a further 25 metres. Since the light distribution corresponds to the steering angle, the driver is able to recognise the course of the road at an early stage and adjust his driving accordingly.

The active light function operates in both low beam and main beam mode, and continuously adapts itself to the vehicle speed. When developing this technology Mercedes-Benz deliberately opted for a dynamic system, for in comparison with a static, selectable cornering light it also offers a significant improvement in safety on country roads and when negotiating sweeping bends.

Only a few months after taking the active light function into series production, Mercedes-Benz presented the next innovation in lighting technology in spring 2004: a cornering light function which considerably increases safety at junctions and when entering side roads, as well as when taking bends slowly.

Intelligent Light System: light for any driving situation

From 2006 Mercedes-Benz is combining the active light and cornering light functions with three new lighting functions to create a unique package: the Intelligent Light System. The E-Class is the world’s first automobile to be equipped with this technology. Its intelligent headlamps adapt to the prevailing driving or weather conditions, ensuring that the driver has better visibility and preventing accidents. In addition to the active light and cornering light functions, the system incorporates a newly developed country mode, a long-range motorway mode and enhanced fog lamps for improved orientation when visibility is poor.

Chronology: milestones in lighting technology

1895
Candle and petroleum lamps

1908
Electric headlamps powered by battery

1913
"Bosch Light" as a complete system with headlamps, a dynamo and regulator

1915
Two differently inclined headlamps can be used to produce low and main beam

1924
Bilux bulb for low and main beam from a single reflector

1957
Low beam, main beam, sidelight, parking light and indicator housed in one unit, for example in the Mercedes-Benz 300 SL Roadster, and the first headlamps with asymmetrical light distribution

1961
Rectangular headlamps

1962
The first halogen bulbs appear in auxiliary headlamps

1965
Dual-focus reflector system with two H1 bulbs for low and main beam

1971
Lamps with H4 twin-filament bulbs and H4 main headlamps

1974
First electric headlamp range control system for convenient headlamp adjustment from the cockpit

1983
Invention of the projection-beam headlamp

1986
Premiere of the poly-ellipsoid headlamp

1988
Development of variable focus technology for headlamp reflectors

1990
Headlamp range control becomes a legal requirement

1991
Premiere of xenon headlamps with gas discharge lamps in the Mercedes F 100 research vehicle

1992
First-generation xenon headlamps enter series production

1993
Headlamps with plastic lenses in series production for the first time

1995
Xenon headlamps with dynamic headlamp range control in the Mercedes-Benz E-Class

1999
Premiere of bi-xenon technology with additional halogen main-beam spotlamps in the Mercedes-Benz CL-Class

2002
Presentation of the active light function in the Mercedes-Benz E-Class (in series production from 2003)

2004
Premiere of the cornering light function in the C-, CLS- and SLK-Class

2006
Presentation and world premiere of the Intelligent Light System in the E-Class