Light in the dark

07/04/2019 Know-How

A new hybrid LED solves the traditional problems of automotive lighting: It avoids dazzling oncoming traffic while ensuring ideal illumination of the road ahead. The high resolution of over 1000 fully electronically controlled LED pixels allows extremely differentiated, active and, therefore, efficient light distribution.

Every motorist knows the problem: Being dazzled by oncoming and following drivers' headlights at night. This is both annoying and dangerous, as it can take several seconds for the sight of dazzled drivers to clear. Conversely, good illumination is essential for road safety.

Osram Opto Semiconductors has now solved this problem with its hybrid LED Eviyos. It combines two technologies in one component: The light-emitting chip and the control electronics for the 1,024 individual pixels, which ensure ideal illumination of the road. At the same time, the dazzling of oncoming traffic is prevented. In addition to its outstanding illuminating power and compact design, Eviyos is also suitable for use in intelligently controllable headlights due to further benefits, such as its efficiency and scalability. They recognize certain driving situations and react to them automatically. This works through the interaction of a camera and a control unit: The camera captures ambient information and forwards it to the control unit. This processes the information and forwards correspondingly adapted light distribution to the light points in digital form. The technology for the development of Eviyos is based on the findings of the µAFS research project completed in the fall of 2016, which involved various project partners from the industrial sector (including Fraunhofer IZM, Infineon, Hella, and Daimler) under the coordination of Osram Opto Semiconductors. Eviyos generates the desired light distribution fully electronically, i.e. without optomechanical components. The resolution of the system is significantly higher than that of the previous LED matrix headlights. The light distribution can, therefore, be controlled in a highly differentiated manner.

Less extremes, more flexibility

In the past, the situation with conventional driving lights was always as follows: Drivers had dipped and full beam headlights at their disposal. There was no further differentiation. Even if this is sufficient in many cases, the disadvantages are obvious: When two vehicles are approaching each other, there is a risk of dazzling. However, when driving with dipped headlights, only the area directly in front of the vehicle is illuminated. Quite often they are inadequate to provide sufficient illumination. Conventional light therefore only offers these two extremes and the associated limitations.

The increasing illuminating power of LEDs has made it possible to use them in electronically controlled vehicle headlights since around 2013. Even the first LED modules were intended to provide a remedy for the well-known problems of automotive lighting. They already enabled variable light distribution through which certain parts of the light field could be blanked out or otherwise adapted to the driving situation. These solutions delivered great progress, especially in terms of safety but also in terms of driving comfort.

What is the difference between Osram's Eviyos and previous LED matrix solutions for headlights? Basically their resolution. It may sound a little trivial at first, but it is definitely an important aspect: If a current LED headlight works with between eight and less than 100 LEDs, the resolution of the new lighting is about ten times higher. This resolution makes it possible not only to exclude large areas from the light field but also, for example, to mask or dim out the area of the windshield of oncoming traffic - or the face of a pedestrian or cyclist as well as highly reflective traffic road signs. Otherwise the visibility of the surroundings is completely preserved - as if you were driving permanently with high beam headlights. Within just a few milliseconds, individual pixels can be adapted to the new situation - a decisive factor in fast-moving events that are constantly changing. Eviyos not only allows the pixels to be switched on and off individually; moreover, the pixels can be dimmed. For instance, a traffic road sign should not become invisible, it should simply not dazzle the driver. This also enables soft light transitions.

Perfect illumination through image recognition

Needless to say, the right sensors are a prerequisite for correct functioning of the LED in the vehicle headlights. These can be camera systems with appropriate image recognition. The "intelligence" of the system depends primarily on the software users provide for their image recognition and illumination system. Moreover, extended functions are also possible. For example, the light can warn separately of hazardous areas or even project information, such as warnings or direction arrows, onto the road.

For the brightness of Eviyos, Osram currently specifies a luminous flux of at least 3lm per pixel with a current rating of 11mA. This corresponds to roughly 3,000lm per LED - more than twice as much as the luminous efficacy of a halogen headlight. However, according to Osram, an even higher luminous efficacy should be possible. The LED itself measures only 4mm x 4mm, control unit included. The comparatively high contrast of at least 300:1 also contributes to the quality and differentiated illumination. In addition to lower power consumption, the LED system is lighter than xenon headlights and, above all, less susceptible to vibrations - a fact that benefits continuous operation.

If required, Eviyos can be supplemented in the vehicle by further LED solutions - according to customer requirements. They can also be used as components for intelligent lighting systems in other applications. LED matrix headlight systems are currently not yet approved for the USA due to the legal regulations in force there. However, it is hoped that the directives will be revised and adapted to the new technical situations.

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