Automotive lighting evolved at a snail's pace through most of the 20th century. But over the past 20 years the technology seems to have advanced at the speed of light. So much so that it has become a source of confusion for many car buyers. In the case of some of the new ultra-bright lighting systems, it has also become a source of irritation among many drivers meeting or being followed by vehicles on which they are fitted.
Here's a look at the progress of automotive lighting through the ages, from kerosene lamps through sealed beams to LED matrix arrays.
KEROSENE & ACETYLENE - More than a century ago, if cars had headlights at all they were probably kerosene lamps with wicks or, on more refined models, pressurized acetylene gas lamps. In many cases they were more decorative than functional. Driving at night would have been a low-speed undertaking for the illumination from those lamps was definitely limited.
TUNGSTEN BULBS - Thomas Edison is credited with the idea of a metal (tungsten) filament positioned between two stiff wires or poles, sealed in a glass container or bulb that is filled with an inert gas, usually argon – a concept still used in many light bulbs today. Electricity applied to those poles heated the tungsten element to about 2,500 degrees Celsius, at which point it emits white or visible light. That light was gathered reflected off a mirror or reflector forward through a lens, which may have been etched to direct the light.
The use of electric headlamps became commonplace after the Delco integrated lighting and generating system was introduced in 1912.
DUAL SEALED BEAMS - Tungsten bulbs inside reflective cases with beam-directing lenses were the norm through the balance of the pre-WWII period. But in 1940, airtight sealed beams were introduced, combining all three elements into a single unit with a parabolic reflector inside the sealed actual lamp. They were quickly adopted and mandated as an industry standard, with two 7-inch-diameter lamps per vehicle, throughout North America. While they dramatically improved and standardized the lighting capability of new vehicles, their use also limited the styling freedom offered by the separate components.
QUAD SEALED BEAMS - Some of that styling freedom returned by the late 1950s, when regulations changed in many jurisdictions to permit the use of four smaller, 5.75-inch-diameter, sealed beams – two for both low and high beam operation and two for high beams only. That changeover began in 1957 and was universal by 1958. There was even greater styling freedom in Europe and many other countries, however, where sealed beams were not mandatory and more aesthetic headlamp lens shapes were allowed.
RECTANGULAR SEALED BEAMS - Under pressure from automakers who craved more stylistic freedom, regulators in North America expanded regulations to permit double or quad rectangular, as well as round, sealed beams in 1974. The quad layout quickly became the norm although whether or not it was more aesthetically pleasing was a matter of taste.
HALOGEN LAMPS - Meanwhile, in Europe the use of halogen bulbs had become widespread. Halogen bulbs still use a tungsten filament, but one enclosed in a smaller quartz-like container more able to withstand their high temperatures than glass. The container is filled with halogen gas which combines with tungsten atoms and deposits them back on the filament. This “recycling” allows the filament to last two to three times longer than tungsten bulbs.
HALOGEN LAMPS - Halogen bulbs emit more blue and less infrared light, giving them a whiter appearance. They also use less electricity and run cooler, allowing the replacement of glass lenses with polycarbonate and other plastics which are lighter, more scratch resistant, less prone to breakage and easier to mold into the intricate shapes desired by designers. In 1983, North American regulators relented on their rules and allowed the use of separate bulbs in headlights on this continent, opening the door for innovative new designs and technologies – although still within well-defined limits.
XENON / HID - HID (High Intensity Discharge) lights first came into prominence as mercury and sodium vapour lamps used for street lights or for outdoor recreation areas where their efficiency and low energy requirements are a major factor. The name Xenon comes from the source of the light, Xenon gas, and the HID for the High Intensity Discharge necessary to ignite the Xenon gases. Xenon lights have no filaments. Instead of passing 12 volts of direct current (DC) electricity through a metal element, causing it to glow, they use 25,000-28,000 volts of alternating current (AC) to ignite a mixture of xenon gas and metallic salts.
PROJECTOR LAMPS - HID bulbs can produce up to three times the light of a traditional halogen bulb of the same size, while using less electricity and lasting several times longer. This brighter, whiter light is then projected unto a reflector which gathers and directs the light like a normal headlight. But the reflector is optically-engineered to not only gather the light, but focus it. Instead of having the lens direct the light, the Xenon light actually projects it in an exact focus – thus the common term projector lamps. Initially used only for high beam units, advances in the projector and reflector technologies have allowed their use in low beam units as well – vehicles equipped with both high and low beam HID lights are said to have Bi-Xenon lighting.
LED HEADLAMPS - The latest development in headlamps is the use of LEDs (Light Emitting Diodes), which continue down the path of less energy, size and weight. In addition to being bright, they are very quick to activate making them great for brake and other warning lights as well. LEDs have no filament, don’t require much energy, don’t get hot and last for a very long time. The light comes from the movement of electrons in a semiconductor material. They emit a large number of photons which are contained in a plastic bulb that concentrates and focuses the light.
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