LED There Be Light

The history of mankind has always also been the story of light. Technology and culture have developed wherever people have succeeded in controlling and managing light. Now, with the introduction of light-emitting diodes (LEDs) and digital light control systems into our everyday lives today, lighting has also finally become intelligent.

LEDs have been around for quite a while, appearing, for example, in the red numeric displays of pocket calculators from the 1970s. In fact, LEDs are now to be found everywhere in our daily lives, without most of us really noticing it – they are used for the background lighting of cell phone displays, television sets, and computer screens, as well as for transmitting the signals of remote controls, displaying the letters and images in highway signal bridges, and serving as pixels in the huge screens used for public viewing. LEDs are also ubiquitous in today’s motor vehicles, where between 200 and 600 of the devices are used for everything from taillights and turn signals to the innumerable small signal lamps in a car’s interior and in the dashboard displays. What’s more, LEDs are now also found in the latest headlights.

LIGHTING DESIGN

LEDs also provide substantial benefits in this area. Competing automakers offer partial solutions, but Daimler has stayed true to its principle of building on previous successes without sacrificing comfort and safety. “We developed our LED headlights so that they could immediately offer all the benefits that our customers enjoy with the previous xenon technology,” says Uwe Kostanzer, Head of Light System Development at Daimler, in describing the task that he and his colleagues faced. The system’s development was completed in just 26 months, including the time needed to create the design. The new dynamic LED headlight, which will make its market debut this year in a new model Mercedes-Benz coupé, is celebrating its world premiere as a new kind of interactive system that promises to further improve safety.

The headlight contains all the features that are found in the familiar Intelligent Light System: the country mode, which provides superior illumination of the driver’s side of the lane, compared to what conventional low-beam headlights offer; the highway mode, which illuminates the full width of the lane and increases visibility by 50 meters at speeds over 90 km/h; the expanded fog light function, which directs more light to the sides of the lane; the active light function, which adjusts the headlights to follow the steering movements, extending visibility by 35 meters; and, lastly, the active cornering light function, which provides additional illumination for the indicated driving direction.

Dynamic full-LED headlights from Mercedes-Benz

The light specialists at Mercedes-Benz have also succeeded in linking the LED technology with Adaptive Highbeam Assist, which uses a windshield-mounted camera to continuously and automatically brighten and dim the headlights; this increases and reduces the range of the high beams in relation to the distance to a preceding or oncoming vehicle. What makes LEDs particularly attractive for automotive engineers is that they will make it possible to use electronics and software in place of many of the movable mechanisms found in today’s systems. The cornering light function, which still needs servomotors to move the headlights in response to the driver’s steering movements, is a good example of this. In the future, the xenon lamps will be replaced by LED arrays featuring a matrix of more than 80 high-performance light-emitting diodes, each of which will point in a different direction and be individually controllable. The individual diodes will then only have to be dimmed or turned off and on in order to achieve all the required light effects.

Lastly, LEDs will also enable the automotive engineers to reduce energy consumption, because the new headlights will only consume about 30 watts compared to around 130 watts today. And the engineers at Mercedes-Benz have developed an LED daytime driving lamp that only consumes four watts, compared to the current 38 watts. Kostanzer believes the new LED headlights are just the beginning. “The current LED headlight contains 353 individual parts, which means it is considerably more complex than its xenon counterpart,” he explains. “It has to become more efficient and less complex, and that’s why our goal is to simplify the system and increase its degree of integration.”

THINKING LIGHT YEARS AHEAD

The LED headlight is therefore destined to undergo a process of rapid development and change. At the same time, the development engineers have to make sure there is a certain amount of continuity. “We have to think far ahead with our designs,” says Kostanzer. “That’s because the LEDs we are now installing in cars probably won’t exist anymore five years from now. Despite that, we will have to continue to provide spare parts for today’s vehicles. That’s a completely different situation compared to today’s incandescent lamp, which we have used for more than 40 years.”

What makes LEDs special is that they are semiconductor products – a kind of “chip” with a structure and mode of production far more similar to that of memory chips and computer processors than to that of conventional light sources like incandescent lamps, fluorescent tubes, and other types of discharge lamps. The only thing LEDs have in common with conventional lamps is that they glow. LEDs also are becoming steadily brighter, and high-performance versions can now even replace their conventional rivals in demanding roles.

LEDs also offer other advantages: They can be dimmed and switched on and off very quickly, and their light is directional from the very start. Depending on the semiconductor material used, the chip creates light of different colors across a broad range of the spectrum, without requiring a filter. It can even shine in the ultraviolet range. Examples of this include the small UV lamps that dentists use to harden composite resin fillings. LEDs are also appealing because of their small size. A “big” chip measures only one square millimeter without its transparent plastic housing, which protects the lamp and often serves as a lens as well. And last but not least, the LED has a much longer service life than most of its competitors, lasting about 50,000 hours on average, with the duration depending on the temperature, application, and the intensity of the current.