Xenon lamps for automotive lighting
Bright and energy-efficient, long-lived and extremely attractive: xenon light sources – also known as high-intensity discharge (HID) lamps – revolutionised headlighting in the early 1990s. Today, one in three new vehicles on the road are fitted with xenon light.
Xenon lamps offer major advantages:
- they deliver twice as much light as conventional halogen lamps and consume a third less energy;
- the light they produce is similar to daylight and thus makes for better visual conditions;
- they provide optimal roadway illumination;
- they score points for an extremely long life: as a general rule, they need to be replaced only once during a vehicle's life.
Xenon light offers significant gains in terms of safety. Product safety tester TÜV Rheinland found in a study that over 50% of serious accidents on country roads and more than 30% on motorways could be avoided if all vehicles in Germany were fitted with xenon light. Even more safety is offered by the new generation of bi-xenon headlights. As the heart of an adaptive bending light system, they permit the range of the headlight's low beam to be almost doubled, even on bends.
Arc instead of filament
Unlike halogen lamps, xenon lamps do not have a filament; they light up when an arc is created between two electrodes. Light is generated by a controlled gas discharge, which occurs in a small quartz tube filled with xenon gas, metal salts and other substances. On ignition, the ionised xenon gas produces an electrical arc and the metal salts evaporate and form a plasma. The plasma begins to glow – and gives off more than twice as much light as a conventional halogen lamp.
The lamp system has four components:
- the lamp
- an igniter
- an electronic ballast, which regulates the required alternating voltage of around 85 V, or 45 V for operating the new mercury-free lamps, and
- a connection cable
To avoid troublesome glare, the European standard ECE R98 requires that xenon lamps should be fitted with
- an automatic headlight levelling system and
- a washer system to prevent light scatter due to external soiling.
