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HID headlight product information

The high-intensity discharge (HID) headlight is a recent innovation that uses a gas-discharge globe instead of a incandescent globe. They are smaller than other headlights, and this makes them a popular choice for luxury vehicles. The HID headlight has many advantages over other headlights, such as longer life and smaller size. However, their high glare level, high cost, and mercury content must also be considered.

First introduced in 1991, the HID headlight has steadily gained acceptance for the superior visibility it provide. HID headlights are popular in Europe, where they represent half of all new headlights, but they are not as popular in United States and other countries. There are still concerns about their high glare and whether it contributes to an increase in road accidents. Reducing the glare requires special optics and supports designed to keep the beam pointed towards the road at all times. Using HID globes in headlights that are not designed for them is dangerous, and even illegal in most countries.

The HID headlight uses a fused quartz bulb containing a xenon-mercury gas and two tungsten electrodes. Similar metal vapor lights are commonly used for large areas such as warehouses, sports fields, carparks, and freeways. These are often filled with other gases which have long startup times, but the HID headlight uses xenon which reduces this time to less than a second. To begin the startup process, a high voltage spark between the electrodes ionizes the gas and allows current to flow between the electrodes. As more gas is ionized, the current flow between the electrodes rapidly increases. Since light is released from the plasma created by the ionized gas, this startup process may appear as a dim light followed shortly after by a much brighter light.

The HID headlight lamp has more than double the service life of the halogen lamp, and much more life than other incandescent lamps. The globes used in an HID headlight are smaller for a given light intensity, allowing designers to make smaller and more attractive headlights, and avoid the ugly bug-eye appearance that is so common with other headlights. Their intense bluish-white light provides increased visibility at night, and is more attractive than the yellowish light from incandescent globes. While glare is a problem, it is reduced substantially by using systems that automatically level the beam towards the road, and by using a lens cleaning system to reduce light dispersion.

A major problem with HID headlights is that they cost about three times more than regular headlights. They also require a converter that changes low voltage direct current from the battery to high voltage alternating current. All this extra cost is much more than the fuel savings from their reduced power usage. Another concern is their toxic mercury content and the effect it has on the environment when HID headlights are broken or disposed. While HID headlights produce high levels of UV light internally, it is absorbed by the glass and poses no risk. The globes are entirely different to other headlight globes and  cannot be used in headlights that are not designed for them.

The HID headlight is mainly used on luxury vehicles where appearance is more important that cost. They provide increased visibility and longer life while allowing the headlight to have a smaller and more attractive profile. They require special high voltage equipment to power them, and special mounting to reduce glare. Perhaps the only viable successor is the LED headlights, but it will be several years before these gain any significant market share. Until then, the HID headlight will remain standard equipment on many new vehicles.

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