Monday, February 06, 2012

LEDs lead way to bright future

Audi leads the way in LED headlamp use.

At the dawn of the automotive age, many vehicles used acetylene to light the road ahead. Since those dimly lit days, the headlamp has evolved to produce the sort of illumination demanded today.

The first real step forward arrived in the form of the halogen headlight. It produced much more light than the previous incandescent bulb while consuming considerably less power. Then, in the early 1990s, came the xenon headlight. It, too, produced a much cleaner light while consuming even less power. Heading toward the electric era, the consumption of power is going to become an ever more important part of the headlight’s contribution to driving range.

Any reduction in power consumption, however, must not come at the expense of the illumination a headlamp provides. The importance of adequate lighting is found in the U.S. National Highway Traffic Safety Administration’s (NHTSA) numbers — almost 50% of all traffic-related fatalities occur at night, yet just 25% of a motorist’s driving time is in darkness.

For now, the future is the LED or light-emitting diode. The diode itself measures about one square millimetre, which is not much larger than a grain of sand. The reason for this tiny speck’s growing popularity is that it uses electrical energy to generate more white light than any conventional light source, and it does so very efficiently. Regular bulbs produce waste heat in the process of generating light — the LED converts power to light with little heat buildup. The irony here is that the lack of heat means that the lamp itself must be heated to clear away the slushy buildup winter driving brings.

In terms of efficiency, the current-generation LED headlamps are four times more energy efficient than halogen headlights. As with the computer chip, each year brings a vast improvement in overall efficiency. The prediction is that, by 2018, LEDs will be about eight times more efficient than halogen bulbs. The importance of efficiency comes home to roost when you look at the numbers. Cumulatively, Audis sold in 2008 equipped with LED daytime running lights have cut fuel consumption by about 10 million litres a year. Imagine the potential if all cars were to adopt LED-based lighting.
Of course, the fact that LEDs offer an extremely long service life and react faster than traditional bulbs adds to their allure. In a critical situation, an LED lights instantly, whereas it takes a regular bulb around 0.2 seconds to warm up and glow brightly. That seems insignificant on the surface. However, at 100 kilometres an hour, a car is travelling at 27.78 metres per second. That 0.2-second lag time translates into 5.56 metres of driving distance. Now, that is a considerable margin and the difference between an almighty bang and a distant miss.

The true potential of the LED, however, is only just being scratched. Down the road, adding intelligence to the manner in which the headlamp works will make it adaptive and pay big dividends. In this regard, Audi is leading the way. The all-LED headlight system, for example, uses a small video camera in the base of the rear-view mirror and the navigation system to tailor the light pattern according to the driving conditions.
For example, when the GPS tells the headlamp an intersection is nearing, it shifts from the focused light beam that has been illuminating the road ahead to a wider light pattern that lights up the side streets. This significantly enhances visibility and, ultimately, safety.

Future-generation LEDs will be capable of reacting to weather conditions, vehicle speed, the distance between vehicles and potentially dangerous situations. The use of a matrix of LED provides optimal illumination and the ability to switch off segments of the light beam according to the need. A forward-looking camera monitors the road. Its input, along with the information from the GPS, will determine how the lights function. From a practical perspective, killing key sections of the beam prevents the light from blinding oncoming motorists as well as a driver ahead — no more glare from the rear-view mirror!

Using a night vision camera to detect a pedestrian’s heat profile allows the matrix to flash a beam of light toward the person at the side of the road. This not only draws the driver’s eye to a potential hazard, it also warns the pedestrian of the approaching car. It’s heady stuff.

A little further out is the use of laser lighting. BMW is showcasing its take on laser lights in its i8 hybrid, which is set to debut in 2014. It uses a green laser beam that is fired into a box containing phosphorous. What emerges is a brilliant white light that consumes less power than an LED. Conversely, red laser light is very effective in foggy conditions.

Unlike a regular light source, which is blocked or reflected by fog, the laser serves to illuminate the fog itself, which warns the car behind. Better yet, the red light being emitted is only visible in fog, which means it is not a distraction on a clear day.

At this point, cost is the biggest hurdle to the universal adoption of LEDs. However, with mass consumption comes affordability. Today, entry-level cars such as the Kia Rio5 use LEDs as daytime running lights. The future is, indeed, bright.


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