Car xenon lights have been around for 25 years. We’re shedding some light on both myths and technology.
The request was understandable – please more light at the front of the car but please no higher energy consumption. Got it. Clever experts therefore thought in the late 80s that whatever can be bright on the sun could also be bright on a car. No problem, at least none that couldn’t be solved. Big halls and public squares had long been illuminated by gas discharge lamps. So the newly designed lamps for cars no longer housed conventional filaments but a small quantity of the inert gas xenon. If you apply a high voltage, the gas changes to plasma. A little bit like on the sun. If you want a bit more detail, a lot of electrons break away from the then positively charged remaining atoms, moving about independently from them. That’s what we perceive as bright light in this case.
The temperature of xenon lights in the early series was pretty close to that of normal daylight at approximately 5000 Kelvin. Despite the smaller construction of headlights and up to 50% higher luminous efficacy, they don’t require more energy, but the roads are illuminated much better and further. In 1991, the BMW 7 Series was the first production vehicle for which optional xenon headlights were offered. As early as 1997, more than 50% of flagship cars from BMW, Porsche, Mercedes-Benz and Audi were ordered with xenon lights. From 1999, the Mercedes C215 could be ordered with bi-xenon for the first time. So now high beam also worked with gas discharge lamps. Old vehicles couldn’t just be upgraded to xenon headlights through plug & play because the new lamps require their own high voltage source to ignite the gas. So the whole lamp system always needed to be changed, and the costs for that were (and still are) quite significant.
Sounds great. And it is. Nevertheless, in the beginning other drivers would complain quite often that the “new” lights were dazzling them, adding that they were quite blue and not at all pleasant. This could be proven wrong in theory; xenon light isn’t bluer than daylight and the new headlights absolutely complied with the regulations when it came to illuminating the road.
So there’s a bit of psychology behind it, which could now be explained. The emission surface in many xenon headlights is smaller than in normal halogen headlights, which makes them look brighter at the same light output. The bluish light grabs our attention more than yellowish light, so this change in color also explains why it seems brighter than usual. This effect disappears little by little though because more and more vehicles are equipped with xenon lamps. And last but not least, blue light is more strongly dispersed by the lens in our eye than yellow or white light, which means that scattered light creates a shroud on the iris, leading the eye to believe that there’s glare. It’s all about perception.
I haven’t heard anyone complain about the “awful blue lights” for a long time. You see, it’s not so bad. Those of you who have xenon lamps in their cars can still improve them of course. Have a look here. And for those who don’t, well, Osram has other solutions to enhance your performance. May your vision remain unshrouded.