Thursday, November 21, 2013
Different Sizes of Headlights
Automobile headlights have gotten progressively smaller, brighter, and more focused on the road. In early cars headlights were mounted in big, hulking, self-contained units to the front of the grille. As vehicles got more sophisticated headlights were integrated into the body, though they remained self-contained units. In modern vehicles the headlamp is usually a shell which houses replaceable light bulbs.
The First Headlamps
The earliest cars used gas or oil and acetylene-powered headlights mounted to the hood, which were about as big as a basketball and externally powered. Drivers had to get out of the car to turn them on. They had to be frequently repaired or replaced, especially if operated in rainy weather. Electric headlamps finally came into use in 1912. They were still bulky and externally powered, but held up better in inclement weather.
Electric Headlights
As electric headlamps became powered by the cars electrical system, they got smaller and more frequently integrated into the body of the car. They were about the size of a grapefruit or smaller. Mounted at the far, outside corners of the hood, the brighter, smaller electric lights could be focused lower to provide a wide sweep of the road ahead while creating less glare in the eyes of on-coming drivers.
Halogen Headlights
Halogen headlights came of age in the mid-60s. Using a tungsten filament they produce a much brighter light than the older electric lights and last much longer. Because of the improved brightness, they allowed an explosion in headlight shapes and sizes. In the 70s and 80s rectangular-shaped headlights about the size of a checkbook were popular. They were made possible by the superior brightness of halogen lights. They remained self-contained units that plugged into the headlight frame on the car.
High Intensity Discharge
Halogen lamps remain the most common form of car headlight. In modern cars, though, the lamp casing is part of the car. Only the bulbs are replaced. Most manufacturers also offer high-intensity discharge, or HID bulbs. HID lamps use no filament at all. They use an inert gas, usually xenon, that glows brilliantly when a high-voltage arc is present. These lamps can produce twice the brightness of halogen, use less energy, and can appear in different colors. The bluish-white headlights on some high-end cars is produced through HID lamps. Some manufacturers now make bluish halogen bulbs to imitate HIDs, but the halogens do not produce as bright or clear a light.
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