Tech Focus. From xenon to LED, we take a look at how and why lighting has improved so much in recent times. We’ve seen plenty of new innovations in the car world over the last decade but advances in lighting technology have recently reached new peaks… Words: Simon Holmes. Photography: BMW.
In recent years, technology seems to have taken a strong hold of cars as we know them. Advances have come thick and fast and they have filtered down into every aspect from engines and drivetrains to driver aids and, of course, driver safety. But safety can start with the obvious basics and it doesn’t come any more obvious than lighting. Increased visibility at night, and during the day, is hugely important for both the driver and other road users yet real improvements to lighting have been slow to come over the years. Electric headlights appeared on cars around 1900 but the first real advance came in the 1960s with the introduction of brighter halogen bulbs. Aside from projector headlights and elliptical lenses to focus the beams better it took another 30 years before another major advance occurred with the introduction of xenon headlights in the 1990s.
As a premium car manufacturer, BMW has long been at the forefront of all technological advances and lighting is no exception. It introduced the first HID headlights and then the iconic ‘angel eye’ running lights. Recently, however, there seems to have been a flurry of breakthroughs. We’ve seen brighter, more efficient and more complex LED and bi-xenon lights and soon there will be even be laser derived headlights. But how do they work, what are the differences and which are best? Here we will focus on the current and popular offerings from BMW with a look at what’s around the corner, too…
The first real breakthrough since halogen bulbs was the introduction of High Intensity Discharge (HID) lighting, which is better known in the BMW world as xenon lighting. Xenon is, in fact, the name of one of the noble gases that is housed inside the HID pressurised bulb. It’s these gases that replace the usual filament found in a conventional bulb and the light is produced when a high-voltage current passes through the electrode at each end of the bulb. The gases help create and maintain this light.
Xenon lights a produce a much brighter and more intense light. They also consume far less energy when they are working, although getting them up to operating temperature does require an initial surge of energy. Once working, they offer around 2.5 times the light for half the energy consumption of a halogen bulb and also have double the life span.
However, there are downsides and complications. For a start, the light it produces is very strong so it has to be carefully controlled to avoid dazzling other road users. The beam itself is therefore more focused to improve accuracy and it is controlled electronically to vary the height when required. Also, although the bulbs themselves last longer, there is inevitably more to go wrong with the rest of the system and it can be expensive as the bulbs, igniters and resistors used to maintain the high current can all fail over time. They also take a little while to warm up to their operating temperatures and although it’s only a few seconds it means they don’t make ideal high beam headlights where instant light is needed. But that’s where bixenon headlights come in.
After HID light sources were introduced the obvious progression was an LED headlight. These were introduced onto the market around ten years ago. The Light Emitting Diode (LED) produces its light through the complex phenomenon of electroluminescence. The light itself isn’t actually any brighter than a xenon light can produce but it’s still far superior to a halogen bulb. However, there are many other plus points to LED technology.
For a start, LEDs consume a very low level of energy, making them much more efficient and they can react instantly, which is ideal when response time is key, such as for brake light or high beam applications. They also have a much greater life span than normal bulb and when an LED does begin to fail it won’t stop working overnight like other bulbs. Instead it will decrease in intensity over time. The other major benefit is that an LED bulb is much smaller than a xenon or halogen bulb. This means the light can be more focused. On top of that, it also allows more sophisticated and complex shapes to be formed, which looks more stylish.
When used in low power applications, such as brake lights or running lights, LEDs don’t create a lot of heat either but when used in higher power applications, such as headlights, they do require some form of cooling or heat sinking. This is their downfall as this makes the design and production more complicated and therefore expensive in these applications.
To get around the issue of the initial delayed response from xenon lights, early headlight designs featured a secondary conventional filament bulb to provide the high beam. But to maintain a brighter, xenon-produced light for both dipped and high beam BMW soon introduced its bi-xenon headlight. This meant that a single xenon light source did the job of both beams by simply placing a mechanical reflecting screen in the path of light beam to divert it from low to high when required. A simple yet effective solution.
Improved, better-controlled and more accurate lighting has also allowed for many other potential benefits. This is how clever options such as Adaptive Headlights, which are able to actively move and reposition the beams to avoid dazzling other road users, have been introduced. The headlight beam on modern BMWs is also automatically readjusted to counterbalance extra weight in the car or even move in unison with the steering angle to enable improved vision round corenrs. And due to improved energy efficiency daytime running lights have also become standard on many models to improve visibility at all times. These may be small advances but they all help in improving overall safety.
BMW has already developed a pioneering new innovation with its Laserlight system that will soon be available as an option on the i8 model. As the name suggests, laser technology has been carefully harnessed to create a far more intense and powerful light than ever before and it is cutting edge stuff. It works by using three blue lasers located within the headlight cluster and their beams are directed at a series of very small mirrors. These mirrors then reflect and focus the beam’s energy into a lens containing yellow, fluorescent phosphorous gas. When exposed to the blue laser beam it reacts to create a very clear, bright white light. This is then reflected back again to diffuse the light before it shines out through the cluster.
Its abilities are staggering, offering a light up to a 1000 times brighter than a conventional bulb and with twice the range at 600 metres. It’s also 30 per cent more energy efficient than even LED lighting, and the diodes themselves are ten times smaller, enabling the reflector to be just 3cm in diameter. This means the clusters can be much smaller whilst being more powerful, offering more flexibility with extravagant and stylish designs. However, the complexity makes this technology expensive as it also requires auto-dimming technology. A cooling system is also imperative as the system creates much more heat. At present, Laserlight technology is only available for high beam lighting but this will no doubt filter down to dipped lights in time.