Until fairly recently, xenon headlamps were considered the brightest among all the different types of car headlights in the market. The trademark bluish-white light of xenon headlamps can cut through darkness like a knife, and they are held in extremely high regard among car enthusiasts, often being retailed at ridiculously high prices.
However, things seem to be changing. Hella North America, a company specializing in various types, has developed a new type of car headlamps which utilize LED (light-emitting diode) technology to provide illumination. This has been made possible due to the economically feasible development of pure white LEDs, a very recent innovation of electronic lighting technology.
In the past, LEDs have seen a great deal of use in smaller-scale illumination devices, such as reading lamps and flashlights. The main strengths of LEDs are their low energy consumption, long operational lifetimes and amazing brightness. However, before Hella North America's bold venture into this field, it had not been expected that they can be used in car headlamps as well. And Hella has managed to stun the world nonetheless with the results of their research – the LEDs they are using in their latest series of car headlamps possess a luminous flux equivalent to that of conventional xenon lamps, while requiring substantially less energy.
Hella's research on LED technology for car headlamps first started in 2008, in collaboration with Volkswagen, a renowned automobile manufacturer. So far, LED versions of all types of car lamps, including high beams, low beams, daytime running lights as well as direction indicators, have been successfully manufactured.
The technology behind LED car headlamps runs much deeper than simply substituting the conventional bulbs with LED alternatives. Due to the greatly different nature of LEDs as sources of illumination, the light needs to be focused specifically on the road, for which various optical systems need to be used. This is mostly achieved using a structure of seven pentagon-shaped plastic lenses, which are arranged in the form of a honeycomb, and a spade-like freeform reflector placed next to the lens module. The low beams are produced using four sections of the lens module in conjunction with the reflector, while the other three sections are responsible for the high beams.
In case of directional indicators, three pairs of standard LEDs (located away from the lens module, below the reflector) work in conjunction with the freeform reflector.
The greatest advantage of using LEDs as headlamps is their modular nature and their phenomenal durability. LEDs last almost miraculously wrong, rarely malfunctioning, and can easily be swapped out in the event of failure. All in all, they require very little maintenance. Also, each optical element used in the headlamps can also be easily replaced with similar or superior alternatives.
The early prototype designs for LED headlamps could easily produce a luminous flux level of approximately 1,000 lumens for low beams, which puts it on par with most xenon headlamps available on the market. Due to the fact that individual LEDs have lower luminance, creating powerful high beams were somewhat more of a challenge. Several augmentations needed to be made to the headlamp structure in order to accommodate for and overcome this shortcoming.
Another problem which is faced with LED car headlamps is the immense amount of heat they produce when operating at high levels. In order to overcome this, development and installation of special cooling systems was required along with the lamp modules themselves. If left unchecked, the heat would not be properly dissipated and may cause permanent damage to the LEDs themselves.
In early 2009, the Audi R8 V10 became the world's first car to utilize LEDs in all its lamps. Promising up to four times more energy efficiency than conventional lighting systems, LED car headlamps promise to be the future of automobile lighting.