Light-emitting diodes: A futuristic twist on headlights
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Back when cars were first developed, they used gas lanterns, or sometimes even candles, to light their way along dark roads. Today’s vehicles need bright headlights so drivers can see and be seen, but these lamps also need to be long-lasting and energy-efficient.
When Ford launches its all-new F-150 later this year, it will be the first production pickup truck to use LED headlights, one of the newest developments in headlight technology. The name is short for light-emitting diodes.
“It is creating light through electronic means,” says Mahendra Dassanayake, senior technical leader for opto-electronics at Ford. “You can customize it to help with vision.”
Incandescent and halogen headlights contain a filament that gets hot enough to emit light. High-intensity discharge (HID) headlights, also called xenon lights, use an electrical arc between two tungsten electrodes to heat up vapour inside the lamp, creating light.
LED lights use semiconductor chips to produce light. On Ford’s lamps, the chips emit blue light, which is filtered through a phosphor material to make it appear white. A unique lens, cut with 16 optical surfaces and 80 facets, magnifies the light and spreads it evenly, so only one LED is required for each lamp.
The semiconductor chips heat up to about 50 degrees Celsius, so they’re used with an integrated heat sink, a channelled holder that dissipates heat. The lens itself doesn’t heat up, unlike halogen or HID headlights, which get hot. In a halogen lamp, the bulb itself gets as hot as 600 degrees Celsius, Dassanayake says.
Because the lamps stay cool, they won’t melt snow that accumulates when driving in winter. Ford is working on special surface coatings that should help to reduce any buildup.
It’s also important for headlamps to use as little power as possible, since the electricity is ultimately generated by the engine, and any power draw decreases fuel economy. The LED lamps are more than 50 to 60 per cent more energy-efficient than halogen lamps, and about 30 per cent more than HID headlamps. “It will improve as time goes on,” Dassanayake says. “This is technology at its basic inception.”
The new lamps are also more robust than other types, which is especially important in a pickup truck. Excessive vibration from off-road bumps or rough roads can shorten the lifespan of the filament in an incandescent or halogen bulb, but isn’t an issue in an LED lamp, which doesn’t use a filament. “I think LED is going to be the future of lighting,” Dassanayake says.
All about LEDs
- LED headlamps are relatively expensive, but they’re expected to last more than five times longer than halogen headlamps.
- LED lights are already used extensively in vehicles, including in taillights and interior lighting.
- The F-150’s headlamps also include a thin LED tube that outlines the lamp for a unique signature appearance.