From its humble origins, the headlight has evolved from what was considered an accessory of the 1900s to a necessity safety feature (half of all deadly accidents occur at night). Since its first generation, headlights have traveled a long way from a simple flame to a high-tech laser.
The first vehicle headlamps were officially introduced during the 1880s and were based on acetylene and oil, similar to the old gas lamps. Originally developed for mining purposes, Carbide lamps were produced by dripping water on calcium carbide to produce acetylene gas, which was then burned for a light. These headlights or ‘headlamps’ required regular cleaning because they produced caustic lime, a toxic substance. Its construction was made up of a lantern with a reflecting mirror which sent an unfocused scattered forward light. With a poor range and the absence of a lens protector, a strong gust or splash of water easily extinguished the ‘weather resistant’ acetylene. During cold weather, the water would freeze which would inhibit the gas generation process. Up until 1912, acetylene headlamps were used on the majority of manufactured vehicles. Although they were often praised for their resistance to currents of air and tough weather conditions such as snow and rain, they were soon replaced by electric lamps.
The first electric headlight was debuted in 1898 with the Columbia from the Electric Vehicle Company, but it wasn’t until four years later in 1904, that the Pockley Automobile Electric Lighting Syndicate offered lights powered by an eight volt battery. In 1912, Cadillac introduced their Delco electrical ignition and lighting systems and paved the way of vehicle electrical systems which is similar to what we see today. Guide Lamp Company was the first company to introduce the low beam headlights in 1915 but, since most systems required drivers to step out of the car and turn on the lights manually, Cadillac developed its own assembly activated by an interior-mounted lever controlling the exterior lights. But even so, the first modern light bulb, incorporating both the low and the high beams, saw daylight in 1924, being followed by a foot-operated dimmer switch invented three years later. Although electric headlights were a step in the right direction, the first ones required more power than they produced. As a result, car manufacturers lost interest and decided not to invest in them.
Sealed Beam Headlights
The next innovation in headlights occurred around 1939, with the development of the sealed beam style headlight. It was manufactured with a metal reflector, a soldered-in bulb, and glass lens fastened permanently together due to patent restrictions. This standardized round sealed beam headlight provided a more focused light with the help of the tungsten filament sealed inside a glass/reflector lens. Per the Federal Motor Vehicle Safety Standard 108, all vehicles sold in the U.S. were required to have two 7” in diameter round sealed beam head lights per vehicle, which limited the design of automotive designers. In 1957, the U.S. law began to allow for four sealed beam headlights, each being 5 ¾” in diameter. Two served as a high beam setting while the other two would serve as a low beam. (As a side note, hidden headlamps first appeared in 1936 on the Cord 810).
Up until the introduction of the composite headlights, burned out lights meant the whole unit needed to be replaced. With an all-in-one-place system, the headlights at times would limit the visibility due to a dark residue on the inside of the glass left from a boiling filament. To regain full visibility, that meant replacing the whole all-in-one headlight which was costly and frequent. In 1983, the Federal Motor Vehicle Safety Standard 108 was amended to allow composite headlight assemblies to include replacement bulbs, a nonstandard shape, and aerodynamic lenses. Since this amendment, headlights for the first time ever were manufactured from plastic. Since composite headlight units made it possible to replace the bulb instead of the whole unit, the replaceable halogen bulb became the preferred light source for headlights until the introduction of the HID headlight.
The halogen sealed beam headlight didn’t make its debut until 1962, where it became mandatory in Europe. European car manufactures essentially took the sealed beam design and enhanced the light output by inserting halogen gas into the unit so it would react with the tungsten filament. This design provided a brighter light source to illuminate the roads ahead. The U.S. automotive market didn’t take to this newly improved technology until 1978. The typical life of these headlights was 450-1,000 hrs.
Xenon (HID) Headlights
The next evolution of headlights came with the development of high-intensity discharge systems (HID), also known as xenon headlights. The first model to implement these brighter lights was the 1991 BMW 7 Series. Five years later, they appeared on the 1996 Lincoln Mark VIII. Xenon headlights are a combination of metal halide lamps filled with Xenon gas. They use a ballast and an ignitor which controls the current sent to the bulb. The ignitor comes as a stand-alone element in D2 and D4 systems and as bulb-integrated elements in D1 and D3 assemblies. This helps produce adequate light levels immediately when starting up a vehicle and full brightness shortly thereafter. Compared to halogen lights, HID headlights (Xenon) offer improved nighttime visibility, lamp life (2,000 hrs.), lumens, high intensity beam patterns, color temperature, and durability. Since the lighting units could be smaller without impacting the light emitted, automotive designers were able to design headlights more creatively.
There are, however, a few disadvantages to high-intensity discharge lights. First, they produce considerably more glare than the other types of headlamps. Secondly, all systems have to be equipped with headlamp lens cleaning systems and automatic beam leveling control, with both measures especially aimed at reducing the amount of glare produced by these lamps. Last but not least, xenon is way more expensive than any of the other types of lights. This is why it is found on the more expensive models, like the Challenger SRT.
The LED headlight that we know today made its appearance in the 2004 Audi A8, primarily as a daytime running head light when the vehicle was in motion. They are widely used in today’s markets since they produce a massive amount of light without requiring a whole lot of energy. LED headlights reign supreme in efficiency since they produce substantially lower levels of heat than the previous generations of headlights. Since the diodes are relatively small, they can be manipulated into a range of different headlight shapes, the most unique at the time being the 2007 Audi R8 which used LEDs in every section of its headlight cluster.
Even though it sounds like something out of a James Bond film, laser headlights are the newest form of automotive lighting technology. The first production car to feature this state-of-the-art technology is BMW’s i8. Three diodes shoot blue laser beams into a prism, which focuses the three beams into one. The single beam is then passed through a phosphorous lens that transforms the blue light into a white light. The beam then hits a reflector and is directed onto the road. Astonishingly, these lasers are an impressive 30 percent more efficient than LEDs and can illuminate nearly double the viewing distance, to around 6,500 feet. That’s around 18 football fields of lit up road! Even though these are impressive numbers, lasers are only being used as high beams because they aren’t quite as focused as LEDs.
Supplementing the new technology in headlights are such safety enhancers as daytime running lights, Advanced Front-Lighting System (uses steering angle and a number of sensors, to anticipate road curves and adjust the lighting directions before entering them) and light sensors (automatically turns on the headlamps, when needed, without driver assistance).