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An Inside Look at Vehicle Lighting

An Inside Look at Vehicle Lighting

By Jeff Youngs, February 24, 2012
headlightsThomas Edison is credited with inventing the world's first light bulb in 1879-six years before KarlBenz invented the world's first practical automobile (the term"practical" meaning that it was truly a viable alternative to a horse).While the technology behind the light bulb and the automobile is very different, these two significant inventions would drive each other's development over the next century.

The first light bulbs were very fragile-completely useless in early automobiles that bounced harshly over unimproved roads. In fact, the first cars used lamps burning acetylene or oil as they were resistant to vibration, wind and rain. Advancements in bulb design, such as flexible filaments (a metal spring in which electricity is passed through) and dynamos (the predecessor to today's alternator), made the electric headlamp much more commonplace just after the turn of the century.

Over the next fifty years, the so-called incandescent bulbs (in this design electricity is passed through a thin tungsten metal filament)became the standard of automotive lighting. They were used for headlamps, and miniaturized for brake lights, turn signals and side markers. Incandescent bulbs were used to light the cabin, and project illumination on the instrument panel. Things started to change in the early 1960s with the invention of the halogen bulb. While the halogen bulb operates in the same manner as its tungsten predecessor (an electrically-charged white-hot filament produces light), the gas inside the bulb is halogen. The halogen gas allows the filament to burn hotter(putting out more light) with a service life that is more than double that of a tungsten bulb. In addition, the projected light is much whiter in color-making them excellent headlight replacements.

By the late 1980s, nearly every vehicle on the road was utilizing halogen technology for its headlight bulbs. For the most part, all other vehicle illumination including cabin lights, brake lights, turn signals and side markers were still using traditional, tungsten-based incandescent lighting. (It is interesting to note that Chryslerexperimented with electroluminescent lighting-a special material emits light when electricity is passed through it-in the 1960s.)

Lexus LSA completely different way of producing light-with semiconductor-based light-emitting diodes, orLEDs-hit the automotive scene shortly thereafter. The small LED bulbs first appeared on dashboards, built into the electronics as indicator lights. Since LEDs didn't use a filament for illumination, there were no components prone to break or wear out-ideal for instrument clusters.The LED bulb promised an extraordinary long life, it ran cool, and used very little electricity. As an added benefit, they could be engineered in countless different colors. Within a decade, the technology had advanced to the point that LED bulbs could be used to project light on the instruments (not just backlit) and eventually illuminate the cabin.

Headlight design also took a leap forward with the discovery of high-intensity discharge (HID) light technology. The HID bulb is another type of illumination that forgoes the damage-prone filament and replaces it with high-pressure gas-xenon in this case. Electricity is used to heat the gas white-hot, producing plenty of bluish-white light.While HID lamps are not compact in size (they cannot be used within the cabin), they use very little electricity once they are started-thus explaining their popularity on efficient hybrid and electric vehicles.The first widespread application of HID headlights was in 1991 when BMWintroduced them on the flagship 7 Series sedan. While the light output is superior, the technology remains much more expensive than halogen headlamps, so HID illumination is still reserved for specialty or high-end vehicles.

Not to be left in the dark, engineers have worked diligently on automotive LED technology. Late-model cars, in all price ranges, now use inexpensive LED illumination for the cabin (some even allow the colors to be customized), blinkers, side, and brake lights. With decades of development behind it, the LED bulb was eventually engineered to work as an automotive headlight. In 2008, Lexusintroduced LED headlight technology on its flagship LS sedan.

Vehicle lighting has come a long way from the crude oil lamp that was standard just over one century ago. While HID and LED technologies are enjoying widespread use today, even more advanced technology-such as organic light-emitting diodes (OLED) and polymer-based diodes(PLEDS)-will find their way into the automobile in the near future. No matter how you look at it, the future of vehicle lighting looks very bright.

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