Light Sources

Some 50% of drivers feel stressed when driving in poor lighting conditions.[1] The better the road ahead is illuminated, the less stressful they are: good lighting is the best night vision aid. HELLA Group has been setting lighting milestones ever since the very first automobiles were invented. It is consistently highly innovative in the way it approaches the development of lighting products and systems. Although our focus is primarily on enhancing driver comfort and safety, the fact that our lighting products are also attractive in appearance means that car manufacturers can come up with specific vehicle designs and fulfil their strategies. Find out more about our range of lighting and individual products.

^[1] Frost & Sullivan

Halogen Headlamps

Halogen light sources have been used as vehicle lights and as reflector and projection systems for all important automotive lighting functions since the 1960s. Halogen bulbs last longer and are more efficient than conventional filament bulbs. Each halogen bulb contains a tungsten filament, like a regular light bulb, but the gas inside is a special halogen mixture. This mixture combines with the tungsten atoms as they evaporate from the glowing filament, which it then deposits back on to the filament (not the inside of the bulb itself). This results in optimal light emission. The temperature of the filament inside a halogen bulb is higher, which means that more light is emitted. In addition to halogen reflective systems, vehicles use headlamps with a bi-halogen projection system. These types of headlamps can produce both full beam and dipped beam using a single projection module. The beam is mechanically switched by means of a shutter. When in the higher position, the shutter forms the cut-off line for the dipped beam. Moving the shutter to the lower position switches on the full beam.

Xenon Headlamps

Xenon headlamps help to save lives. If all cars driving on German roads were to use xenon headlamps, the number of accidents that happen at night would be more or less halved and the number of fatalities in these accidents would be reduced by 18%.[1] Despite the considerable advantages of xenon headlamps, more than half of Germans lack information on this type of headlamp, and almost the same proportion cannot name a single benefit of xenon headlamps. This figure contrasts starkly to the high level of satisfaction among people who own vehicles fitted with this type of system (96%).[2] Xenon headlamps produce light by discharging gas. The high voltage required to ignite the xenon gas (20,000 V) is generated by an electronic ballast.

In bi-xenon headlamps, the full beam and dipped beam are produced by a single projection module, with the transition between dipped and full beam provided by a mechanical shutter located in the headlamp. As this light retains its colour and intensity, the human eye perceives the resulting illumination as unchanged. A halogen dipped beam is brighter than a xenon dipped beam and illuminates the road better. The range is even higher in full beam lighting and the edges of the road are illuminated much more clearly. The automatic or dynamic xenon headlamp positioning system always ensures the correct beam alignment, depending on the load, braking process and acceleration of the vehicle. Inductive or magneto-resistive axle sensors measure the vehicle’s load status, while the headlamps are repositioned using servomotors. In a dynamic headlamp positioning system, the vehicle speed is processed using the speedometer signal. As a result, the headlamps can rapidly adapt to braking and acceleration processes. The complete xenon system also includes a power wash system that keeps the headlamp cover glass clean at all times, ensuring that the xenon beam is directed on to the road so that oncoming drivers do not have to contend with too much glare. In 2003, dynamic cornering lighting was introduced to give drivers a better and wider field of vision. This system works by rotating the light modules according to the steering wheel angle. The next phase in the development of advanced headlamp systems was the introduction of the adaptive frontlighting system (AFS) in 2005. Based on the VarioX module, the distribution of light from the headlamp is adapted to the specific situation, depending on the vehicle speed and steering wheel angle. In 2009, there was another breakthrough: for the first time ever, the headlamp system was linked to a camera sensor, and this combined unit was able to use data collected from the vehicle’s surroundings together with data from the vehicle itself. When the adaptive cut-off line (aCOL) is generated in this way, the headlamps’ light cone is controlled so that it always ends in front of other vehicles. Today’s state-of-the-art non-glare full-beam systems can even automatically mask out parts of the road where lighting could be a nuisance to other drivers.

^[1] TÜV study

^[2] PULS study, 2008

LED Headlamps

A groundbreaking innovation in automotive lighting, LED headlamps stand at the pinnacle of the rapid development in this area of lighting, which can be traced to the first ever LED automotive lighting component from the early 1990s: the central high-mounted brake light.

LED headlamps can currently only be found in high-end vehicles because LED lamps are very complex and still quite expensive compared to conventional technologies. The public debate on CO₂ emissions in the political, business and technology sectors is one of the main drivers for the introduction of energy-efficient lighting systems in mass-produced vehicles. LED headlamps could potentially become very popular among drivers not only because they are environmentally friendly, but also because they increase driver comfort with their daylight-like colour. LEDs also provide a wide range of design options and help car manufacturers to create a unique brand-specific style. The lighting functions of LED headlamps are based on a semiconductor that is electronically stimulated to produce light. The light is distributed in such a way that light coming from the different modules is superimposed to form a certain pattern. LED headlamps are designed specifically to distribute light through free-form lenses so that the light distributed by different sources creates the desired effect. To achieve this, however, it is essential that the individual elements of the lens to be fitted with a good heat management system. Since only about 10% of electrical power is converted to the actual light output, the LED chip must be extremely efficient at dissipating unused energy and releasing it into the environment. Until now, all available LED-only headlamps have been limited to basic lighting functions (dipped beam and full beam). However, the dynamic developments seen in adaptive lighting functions are sure to be reflected in LED headlamps as well in the future. Hella Group was already hinting at the range of possibilities when it introduced the first AFS LED headlamps. Developments in this area will continue along similar lines to ensure that future LED headlamps provide the same range of functions as xenon headlamps do today. Another trend we are seeing in LED headlamp development is a shift towards optimised energy consumption. However, this “EcoLED” system does not only excel solely in this respect: it also has the advantage of optimal costs. Compared to today’s halogen headlamps, the EcoLED system will feature superior light output and processing.

Lighting systems

One of the first lighting assistance systems was the dynamic cornering light, introduced in 2003. In this system, the light modules rotate according to the steering wheel angle. This almost doubles the field of vision in a bend.

The dynamic cornering light function has evolved into the adaptive frontlighting system (AFS). This system relies not only on the steering wheel angle, but also on the vehicle speed, as input data to illuminate the road. Based on this internal information, different types of light distribution (including urban lighting, ex-urban lighting, adverse weather lighting, and motorway lighting) are created via a cylinder in the VarioX module.

The next step in development is the creation of the “adaptive cut-off line” (aCOL). This function also draws on data from the vehicle’s surroundings to create the appropriate light distribution. The camera detects the surrounding traffic and senses the vehicles ahead, and then, within milliseconds, the stepper motor turns the VarioX cylinder to the required position, i.e. the light cone ends right before it reaches the oncoming traffic or the vehicle ahead.

The non-glare full beam function allows drivers to drive with the full beam on at all times. If the camera detects another vehicle in the vicinity, the distribution of light from the full beam is adjusted to mask off that particular area.

Although LEDs today are mainly used to illuminate large areas, in the future they will also serve exactly the opposite function. Targeted spotlights will allow for the specific illumination of certain types of objects, such as children playing at the roadside. This will let drivers spot potential risks much earlier and react more quickly.

Adaptive Frontlighting System (AFS)

The dipped beam is just the grouping together of all the sub-distributions of light. As such, an adaptive frontlighting system has been developed to provide the best possible illumination of the road, based on the vehicle’s speed and the steering wheel angle. This requires the VarioX projection module with a rotating cylinder placed between the light source and the lens. This cylinder typically has varying contours and can also rotate around its own longitudinal axis. A stepper motor can turn the cylinder to the required position in milliseconds.

Urban lighting, activated at speeds below 55 km/h, features a horizontal cut-off line to minimise the glare for other road users. The wide light distribution also makes it easier for drivers to spot pedestrians at the roadside.
Ex-urban lighting, activated at speeds between 55 and 100 km/h, has light distribution similar to conventional dipped-beam lighting. The VarioX module generates an asymmetrical light pattern to minimise glare for oncoming drivers. The cut-off line is set slightly higher to improve the illumination of the left edge of the road, thus providing greater overall coverage.
Motorway lighting is activated at speeds above 100 km/h. The light distribution range is designed for wide curve radii at high speeds.
AFS motorway lighting works like a conventional full beam, but requires no driver intervention to prevent oncoming drivers from being dazzled.
The adaptive frontlighting system also has dynamic bend lighting. Depending on the steering wheel angle, the headlamps can rotate up to 15° to provide optimal bend illumination.
“Adverse weather lighting” disperses the light more broadly to improve visibility in rain, fog, and snow. This feature also reduces long-range illumination to minimise the reflective glare affecting the driver’s own vehicle.

Adaptive Cut-off Line

An extended version of the AFS system with static light distribution is the combination of this system with a camera and image processing functions.

The first step in this direction is the creation of an adaptive cut-off line (aCOL):
A windscreen camera detects oncoming vehicles and vehicles ahead and the system adjusts the headlamps so that the light cone ends right before it reaches the other vehicles. This enables the range of the dipped beam to be increased from about 65 to 200 metres (the 3-lux line). If there is no traffic ahead, the system switches to full beam, ensuring that the driver has optimal visibility at all times. The system also records vertical angle information to gauge the topography of the road and ensure that the lighting is deployed even in hilly terrain. The potential headlamp lighting range is based on a feature that checks the level of glare from other road users. This system prevents unwanted glare and ensures maximum dipped-beam distribution.

Vertical Cut-off Line

Full beam is designed to give the driver the best possible visibility without exposing other road users to excessive glare. However, this is not always entirely possible, especially at high speeds or on winding roads. In fact, many drivers keep their full beam off, worried about dazzling oncoming traffic if they are unable to dip their beam in time.

Drivers with glare-free full beam can keep these lights on all the time as their glare is minimal and does cause discomfort to other drivers.
This type of system features a front camera, high-performance software and intelligent lighting technology that automatically masks out the distribution of full-beam lighting in parts of the road where the light could disturb other drivers. The system significantly increases the use of full beam at night.
If the camera detects road users who are at risk of glare, the area around them is automatically masked out. The masked-out sector can dynamically copy a road user’s movements. The area directly in front of the vehicle is illuminated at all times with a standard light distribution pattern comparable to existing dipped-beam lighting. The brightness of the variable zone above the cut-off line can be adjusted locally. One way to ensure non-glare full beam is to install special casing on the VarioX® projection module’s rotating cylinder. Based on the VarioX® module’s image processing functions and intelligent settings, critical areas of oncoming vehicles that could be dazzled are simply removed from the full-beam distribution, but the remaining full-beam field remains intact for the driver’s convenience. This offers much greater visibility compared to standard systems.