Halogen headlights use incandescent lamps as a light source. Their light is typically concentrated in a reflector with a vapor-deposited aluminum coating. Halogen lamps consist of a thin tungsten filament inside an airtight glass envelope filled with halogen gas. When voltage is applied, current flows. Due to its Ohm resistance, the filament heats up and radiates light of approx. 2,700 on the Kelvin scale. The inert gas – halogen – protects the filament against oxidation, resulting in higher light output. Halogen lamps achieve very high luminous power because the glass envelope can withstand extremely high temperatures.
Xenon headlights are gas discharge lamps. A concentrated arc of light burns between two tungsten electrodes in a quartz-glass envelope. With a color temperature of approx. 4,200 on the Kelvin scale, it emits a much brighter light, resulting in much better illumination of the road than halogen headlights using incandescent lamps. The energy consumption of xenon headlights is about 20 percent lower, while their life is much longer than that of the previous, commonly used lamps with filaments.
LEDs (light-emitting diodes) are luminescent spotlights. The light is generated by the supply of electrical energy without mechanical action inside the semiconductor crystal. The development of the blue light-emitting diode in 1993 made it possible to generate all colors of light. The application of a small phosphorus plate converts part of the blue light into yellow light, resulting in white as the total color. This enabled the utilization of LEDs in headlights.
Compared to xenon headlights, LED headlights deliver longer visual range, high efficiency and benefits in terms of safety and comfort. Because their color temperature of 5,500 on the Kelvin scale is similar to daylight, they hardly cause eye fatigue, which assists drivers in darkness and adverse weather. In conditions of fog and precipitation, LED headlights reduce glare from reflected light. The low beam roughly requires just 2 times 20 watts, which is significantly less than conventional halogen light. The typical forward voltage of a white LED in the headlight is between 3.0 and 3.5 volts, with possible variations, depending on the type of LED. Light-emitting diodes are maintenance-free and designed for life equaling that of the car.
Matrix LED headlights
Matrix LED headlights produce the high beam with small light-emitting diodes that are concentrated in shared reflectors or lenses, depending on the model. They always optimally illuminate the road without dazzling other road users. As soon as the camera on the windshield detects other vehicles or city limits, the controller partially switches off individual LEDs or dims them in multiple stages, creating several million possible light patterns. The Matrix LED light masks out other vehicles while continuing to fully illuminate the areas between and adjacent to them. Other light-emitting diodes of the Matrix LED headlight assume the function of the maneuvering light that illuminates the lateral area in front of the car when driving in reverse as well as the function of the all-weather light. The latter reduces glare from reflected light in conditions of poor visibility and delivers wider illumination as a fog light with quadrupled range. The dynamic cornering light is generated by shifting the focal point of the light along the curve. The turn signal is predictively activated shortly before the car arrives at an intersection. In addition, Matrix LED headlights include the dynamic flasher and the dynamic lighting scenarios when the driver unlocks or leaves the vehicle.
HD Matrix LED headlights
In 2017, in the A8, Audi introduced HD Matrix LED headlights as an evolution of the Matrix LED headlights. Here, each headlight integrates 2 times 16 small, discretely variable light-emitting diodes for multi-row control of the high beam. They are arranged in two rows inside a shared housing. Thanks to this new configuration and to a low beam that is also variable, the HD Matrix LED headlights illuminate the road with even greater precision and enhanced adjustment to the particular situation.
Audi laser light
Audi laser light refers to the additional high beam that operates in concert with the HD Matrix LED headlights. This laser doubles the range of the high beam. A small laser module in each headlight generates a light cone that extends roughly 600 meters (1,970 ft) as a spotlight. Drivers enjoy greater contrast and tire less quickly. The laser spot, which is active at speeds of 70 km/h (43.5 mph) and above, offers significant visibility and safety advantages. The laser spot is dimmed automatically when the camera mounted on the windshield detects other cars within its range.
Digital Matrix LED headlights with DMD technology
The digital Matrix LED headlight is able to deliver cornering, urban and highway lighting as versions of the low-beam light with maximum precision. It complements the high-beam light by masking out other road users with enhanced accuracy. DMD stands for digital micromirror device, a chip consisting of 1.3 million micromirrors, which is a prerequisite for projections from the headlight. It splits the light into tiny pixels and enables novel functions such as lane light, orientation light and marking light. These innovations assist the driver and enhance traffic safety.
OLED rear lights
OLEDs are organic light-emitting diodes that are less than one millimeter (0.04 in) thin. Their name is derived from the organic semiconductor material of which they are made. Just 3 to 4 volts of electrical potential are enough to cause the thin layers to illuminate. Unlike point light sources such as LEDs, OLEDs are area light sources. As a result, the light achieves an all-new level of homogeneity and can be split into discretely dimmable segments. It requires no optical components such as reflectors and light guides, and makes OLED units efficient and lightweight. OLED rear lights debuted in the Audi TT RS in 2016 featuring a total of 12 segments per lamp. In the Audi A8 in 2017, the number of segments had already increased to 16.
Digital OLED rear lights
Since 2020 Audi has been offering digital OLED rear lights in the Q5 and, for the first time, offers customers a choice of various taillight designs using just one set of hardware. Unlike the OLED rear light in the TT RS, where each lighting function is supplied with energy by a dedicated line, the digital OLED rear lights are connected to the control unit of the on-board electrical system by a bus system. This enables clearly more functions. The technology features a larger number of discretely controllable segments than the OLED rear lamps launched in 2016. The rear light of the Audi Q5 uses three panels, each of which integrates six OLED segments. These can now be activated as desired and with infinite variability of brightness. Communication is created beyond classic signaling functions: in the Q5, Audi, for the first time, has integrated a proximity indication feature for traffic approaching from the rear. The prerequisite for this function is that the car has one of the tow assistance systems – either Adaptive Cruise Control or Active Lane Assist – on board.
Going forward, the digital OLED with more than 60 segments will feature a roughly tenfold number of discretely controllable segments, enabled by higher performance levels of future vehicle electronics and the specifically developed OLED hardware. In addition to personalizing light designs, the digital OLED can be used as an indicating instrument in the rear lighting assembly and hence for car-to-x communication. Subject to government approvals, the drivers of following vehicles could, for instance, receive early warnings of slippery road surfaces or the ends of traffic jams. Thanks to high precision, extremely high contrast and great variability, the rear lights are progressively evolving into displays.
Forward-thinking technology: flexible digital OLED rear lights
Whereas digital OLED rear lights only permit a two-dimensional integration into lamps, new pliable substrates for flexible digital OLED rear lights now enable curvatures to be achieved for the first time. This new freedom creates a three-dimensional light design that enhances the way in which it blends in with the shape of the bodywork. As a result, the area that can be used to personalize the lighting signature, and for communication with the surroundings, will once again become visibly larger. The key features of this technology – perfect homogeneity and high contrast – will be retained, even from various viewing angles.