Lights

Basic Description

The most important sources of light in most vehicles are halogen lamps, incandescent bulbs, gas-discharge lamps and light emitting diodes (LEDs).

Incandescent bulbs: The oldest electric light source, incandescent bulbs consist of a wire filament that heats up and glows when current passes through it. The bulb contains a gas that displaces all the oxygen surrounding the filament and prevents it from burning up (at least for some time). Most incandescent bulbs have a filament made of tungsten and employ argon gas. Incandescent bulbs operate at relatively low efficiency compared to competing lighting technologies. There is also a trade-off between efficiency and the expected life of the bulb. For the first 60 years of automotive history, virtually all electric lights in an automobile were incandescent bulbs. Today, incandescent bulbs have been largely replaced by other lighting technologies.

Halogen Lamps:  Halogen lamps generate high levels of luminous power from relatively modest amounts of electrical power compared to incandescent bulbs. Like an incandescent bulb, they have a tungsten filament surrounded by a gas. However, the halogen gas in a halogen lamp allows the tungsten to be heated to much higher temperatures without burning up. The higher temperature causes the filament to emit much more light for a given amount of current passing through it.

Gas-Discharge Lamps: Gas-discharge lamps do not employ a filament. Instead, the light is created by an arc that forms in a gas between two electrodes. The arc is essentially an electric current. As it flows through the gas, light is emitted. The most common gas used in these type of automotive headlamps is xenon. Generally, gas-discharge lamps very efficient. The are also highly reliable and last longer than lamps with filaments. A disadvantage of high-power gas-discharge lamps is that they often require several minutes to reach their full illumination power.

Light Emitting Diodes: LEDs are semiconductor devices that emit light. They do not employ filaments or gas. The response time to actuation is extremely fast in comparison with other light sources. LEDs are widely used in modern automobiles particularly for brake lights, turn signals, interior lighting and display lighting. Arrays of white LEDs have recently been introduced for use as automotive headlights. LEDs are highly efficient, durable and relatively compact.

Manufacturers

Beru, Bosch, GE Lighting, Hella, Mitsubishi Electric, PIAA, Philips, Sylvania

For More Information

[1] Automotive Lighting, Wikipedia.

[2] Light Emitting Diode, Wikipedia.