Lexus Headlight System Malfunction? Top Answer Update

Lamp mounted on the front of a vehicle

This article is about the device for vehicles. For the head-worn personal lighting device, see Headlamp (outdoor)

“Headlights” redirects here. For other uses, see Headlamp (disambiguation)

A headlight is a lamp attached to the front of a vehicle to illuminate the road ahead. Headlamps are also often referred to as headlights, but in the strictest sense, headlamp is the term for the device itself and headlamp is the term for the beam of light produced and distributed by the device.

Headlight performance has steadily improved throughout the automobile age, spurred by the wide discrepancy between day and night traffic fatalities: The US National Highway Traffic Safety Administration states that nearly half of all traffic fatalities happen after dark, though only 25% of traffic travels in the dark.[1]

Other vehicles like trains and planes must have headlights. Bicycle headlights are commonly used on bicycles and are required in some jurisdictions. They can be powered by a battery or a small generator such as a bottle or hub dynamo.

History of car headlights[ edit ]

Ford Model T with gas headlights

1917 advertisement for the Corning Conaphore headlight lens shown above

Origins [edit]

The first horseless carriages used carriage lamps, which proved unsuitable for high-speed travel.[2] The earliest lights used candles as the most common type of fuel.[3]

Mechanics [edit]

Gas lights [ edit ]

The earliest searchlights to run on acetylene gas or oil were in the late 1880s. Acetylene gas lamps were popular in the 19th century because the flame is wind and rain resistant. Thick concave mirrors combined with magnifying lenses projected the light from the acetylene flame.[4] A number of automakers offered Prest-O-Lite calcium carbide acetylene inflator cylinders with gas leads for lights as standard equipment on 1904 cars.

Electric headlamp[ edit ]

The first electric headlights were introduced in 1898 on the Columbia Electric Car by the Electric Vehicle Company of Hartford, Connecticut and were optional. Two factors limited the widespread use of electric headlights: the short lifespan of filaments in the harsh automotive environment and the difficulty of making dynamos small enough yet powerful enough to generate sufficient current.

Peerless made electric headlights standard in 1908. A Birmingham, England company called the Pockley Automobile Electric Lighting Syndicate marketed the world’s first electric automobile headlights in 1908 as a complete set consisting of headlamps, parking lights, and taillights powered by an eight-volt battery.[6]

In 1912, Cadillac incorporated its vehicle’s Delco electrical ignition and lighting system, forming the modern vehicle electrical system.

The Guide Lamp Company introduced “dipping” (low beam) headlights in 1915, but the 1917 Cadillac system allowed the light to be lowered with a lever inside the car, rather than requiring the driver to stop and exit. The 1924 Bilux bulb was the first modern unit in which the light for both the low beam (low beam) and high beam (high beam) of a headlamp emanated from a single bulb. A similar design was introduced by Guide Lamp in 1925 called “Duplo”. In 1927 the foot operated dimmer switch or dip switch was introduced and became the standard for much of the century. 1933–1934 Packards featured three-beam headlights with three-filament bulbs. From highest to lowest, the bars were labeled “Interurban Driving”, “Country Driving” and “City Driving”. The 1934 Nash also used a three-beam system, but in this case with bulbs of the traditional two-filament type, and the intermediate beam combined the driver’s side low beam with the passenger’s side high beam to maximize visibility of the roadside while minimizing glare to oncoming traffic. The last vehicles to have a foot-operated dimmer were the 1991 Ford F-Series and E-Series vans [Econoline] automated the selection of high and low beams.

Directional lighting, using a switch and an electromagnetically shifted reflector to illuminate the curb only, was introduced in the rare 1935 Tatra, which was only available for a year. The steering-related lighting was seen on the center-mounted headlight of the 1947 Tucker Torpedo and was later popularized by the Citroën DS. This made it possible to turn the light in the direction of travel when the steering wheel was turned.

The standard 7-inch (178mm) round sealed beam headlight, one per side, was required for all vehicles sold in the United States beginning in the 1940s, effectively freezing usable lighting technology for Americans until the 1970s . In 1957 the law was changed to allow smaller 5.75 inch (146 mm) round sealed beams, two per side of the vehicle, and in 1974 rectangular sealed beams were also allowed.[7]

Two Mercedes-Benz SL: on the right with sealed beam headlights according to US specifications; left with normal headlights for other markets

Great Britain, Australia and some other Commonwealth countries, as well as Japan and Sweden, also made extensive use of 7-inch sealed beams, although they were not mandated as in the United States. This headlight format was not widely accepted in continental Europe, where interchangeable bulbs and variations in headlight size and shape were useful to car design.

The technology has advanced in the rest of the world.[7][8] In 1962, a European consortium of bulb and headlight manufacturers introduced the first halogen bulb for vehicle headlights, the H1. Shortly thereafter, headlights with the new light source were introduced in Europe. These were effectively banned in the United States, where standard-size sealed headlights were mandatory and intensity regulations were low. US legislators have been under pressure to act on both lighting efficiency and vehicle aerodynamics/fuel savings.[8] The peak high beam intensity, which was limited to 140,000 candelas per side of the car in Europe, was limited to 37,500 candelas per side of the car in the United States until 1978, when the limit was raised to 75,000. [11][12] Increasing the high beam intensity to take advantage of the higher homologation could not be achieved without switching to halogen technology,[11] so sealed beam headlamps with internal halogen bulbs became available for use on 1979 models in the US. [11][12] Since 2010, sealed-halogen emitters have dominated the sealed-beam market, which has declined sharply since headlights with replaceable bulbs were approved in 1983.[8]

High Intensity Discharge (HID) systems appeared in the early 1990s, first in the BMW 7 Series.[13][14] The 1996 Lincoln Mark VIII was an early American effort at HIDs and was the only car with DC HIDs.

Design and style[edit]

In addition to the technical, performance and regulatory compliance aspects of headlamps, the various ways in which they are constructed and arranged on a motor vehicle must be considered. Headlights have been round for many years because that is the natural shape of a parabolic reflector. Using principles of reflection, the simple symmetrical circular reflective surface projects light and helps focus the beam.[15]

Headlamp design outside the United States, before 1983 [ edit ]

European (top) and US (bottom) headlight configurations on a Citroën DS

In Europe there was no requirement for headlights to be of a standardized size or shape, and lamps could be constructed to any shape or size as long as the lamps met the technical and performance requirements of applicable European safety standards. Rectangular headlights were first used in 1960, developed by Hella for the German Ford Taunus P3 and by Cibié for the Citroën Ami 6. They were banned in the US, where round lamps were mandatory until 1975.[7] Another early headlamp design concept involved traditional round lamps recessed into the body of the car with aerodynamic glass covers, such as those on the 1961 Jaguar E-Type and the pre-1967 VW Beetle.[16]

Headlight design in the United States, 1940–1983[ edit ]

US standard 7 inch headlight combining low and high beam with turn signals on the bottom of a 1949 Nash 600

Rectangular sealed beam headlights with bottom turn signals on a 1979 AMC Concord

Headlight design in the US changed very little from 1940 to 1983. [7] [16]

In 1940, a consortium of state motor vehicle administrators standardized a system of two round 7-inch (178 mm) sealed-beam headlamps for all vehicles—the only system permitted for 17 years. This requirement eliminated tarnished reflector problems by sealing them along with the bulbs.[17] It also made aiming headlight beams easier and eliminated non-standard bulbs and bulbs.

The Tucker 48 included a distinctive “cyclopean eye” feature: a third center-mounted headlight that connected to the car’s steering mechanism. It only came on when the steering was moved more than ten degrees off center and the high beams were turned on.[19]

A system of four round lamps instead of two, a high/low beam and a 146 mm (5 + 3⁄4 in) sealed beam high beam on each side of the vehicle was introduced in 1957 at Cadillac, Chrysler, DeSoto. and Nash models in states that allowed the new system.[17] Separate low and high beam lamps eliminated the need for compromises in lens design and filament placement in a single unit.[20] Other cars followed suit as all states legalized the new lamps when the 1958 models were released. The four-lamp system allowed for more design flexibility and improved low and high beam performance. Car designers such as Virgil Exner conducted design studies with the low beam in their traditional outboard position and the high beam stacked vertically on the car’s centerline, but none of these designs reached mass production.

An example arrangement includes stacking two headlights on each side with low beam over high beam. The Nash Ambassador used this arrangement in the 1957 model year.[24] Pontiac used this design beginning with the 1963 model year; American Motors, Ford, Cadillac and Chrysler followed two years later. Also in the 1965 model year, the Buick Riviera had retractable stacked headlights. Various Mercedes models sold in America used this arrangement because their headlights with replaceable bulbs were illegal in the US home market.

In the late 1950s and early 1960s, some Lincoln, Buick, and Chrysler cars had the headlights positioned diagonally with the low beams outboard and above the high beams. British cars such as the Gordon-Keeble, Jensen CV8, Triumph Vitesse and Bentley S3 Continental also used such an arrangement.

In 1968, the newly introduced Federal Motor Vehicle Safety Standard 108 required all vehicles to have either the dual or quad omnidirectional headlight system and prohibited any decorative or protective element in front of an operating headlight. Glass-coated headlights, such as those used on the Jaguar E-Type, pre-1968 VW Beetle, 1965 Chrysler and Imperial, Porsche 356, Citroën DS and Ferrari Daytona, were no longer permitted and vehicles had to be fitted with uncovered headlights the US market. This made it difficult for vehicles with headlamp configurations designed for good aerodynamic performance to achieve it in their US market configurations.

FMVSS 108 was amended in 1974 to allow rectangular sealed beam headlights. This allowed manufacturers the flexibility to lower the hoods on new cars.[26] These could be arranged in horizontal arrays or in pairs stacked vertically. As previously with round lamps, the U.S. only allowed two standardized sizes of rectangular sealed beam lamps: A system of two 200 x 142 mm (7.9 x 5.6 in) high/low beam units that complemented the existing 7-inch round Format match, or a system of four 165 x 100 mm (6.5 x 3.9 in) units, two high/low beam and two high beam. corresponding to the existing round format of 5 + 3⁄4 inches (146 mm).

The rectangular headlight design was so common on US-made cars that few models continued to use it until 1979.

International headlight design, 1983–present [ edit ]

In 1983, U.S. headlamp regulations were changed to grant a 1981 petition by Ford Motor Company to allow architectural headlamps with replaceable bulbs, non-standard shape, and aerodynamic lenses that could be made from hard-coated polycarbonate for the first time. This made possible the first US-market car since 1939 with swappable bulb headlights: the 1984 Lincoln Mark VII. These composite headlights were sometimes referred to as “Euro” headlights, as aerodynamic headlights were common in Europe. Although conceptually similar to European headlights of non-standard shape and replaceable bulb construction, these headlights conform more closely to US Federal Motor Vehicle Safety Standard 108 headlight design, construction and performance specifications than to the internationalized European safety standards used outside of North America. Nonetheless, this change in US regulations allowed headlamp design in the US market to approach that in Europe.

Hidden headlights[ edit ]

Hidden headlights were introduced in 1936, [28] on the Cord 810/812. They were mounted in the front fenders, which were smooth until the lights were cranked out by the operator, each with its own small dashboard-mounted crank. They aided aerodynamics when the headlights were not in use and were among the Cord’s signature design features.

Later hidden searchlights require one or more vacuum operated servos and reservoirs with associated piping and linkages, or electric motors, gear trains and linkages to elevate the lamps to a precise position to ensure correct aiming despite ice, snow and age. Some hidden headlight designs, such as those on the Saab Sonett III, used a lever-operated mechanical linkage to position the headlights.

In the 1960s and 1970s many notable sports cars used this feature such as the Chevrolet Corvette (C3), Ferrari Berlinetta Boxer and Lamborghini Countach as it allowed low bonnet lines but raised the lights to the required height but none modern since 2004 Volume-produced car models use hidden headlights because they present difficulties in complying with pedestrian protection regulations that have been added to international car safety regulations regarding protrusions on car bodies to minimize injuries to pedestrians hit by cars.

Some hidden headlights themselves do not move but are hidden when not in use by bezels designed to blend in with the car’s styling. When the lamps are on, the covers swing to the side, usually down or up, for example on the 1992 Jaguar XJ220. The door mechanism can be operated by vacuum pots as on some late 1960s to early 1980s Ford vehicles such as the 1967 Mercury Cougar –1970 or by an electric motor as in various Chrysler products of the mid 1960s to late 1970s such as the 1966–1967 Dodge Charger.

Regulations and requirements[edit]

Modern headlights are electrically operated and are arranged in pairs, one or two on each side of the vehicle’s front. A headlamp system is required to produce a low beam and a high beam, which may be produced by multiple pairs of single beam lamps, or by a pair of dual beam lamps, or a mixture of single beam and dual beam lamps. High beam throws most of its light straight ahead, maximizing visibility but creating too much glare for safe use when there are other vehicles on the road. Since there is no special control of the upward light, high beam also causes fog, rain and snow to be reflected back through the retroreflection of the water droplets. Low beam has tighter control of upward light, directing most of its light down and either to the right (in right-hand traffic countries) or to the left (in left-hand traffic countries) to provide a forward view without excessive glare or flashback enable.

low beam [ edit ]

ECE low beam Asymmetrical illumination of the road with low beam – right-hand traffic shown

Low-beam headlamps (low-beam, low-beam, meeting-beam) provide a light distribution designed for forward and side illumination, with the light directed to the eyes of other road users being limited to control glare. This beam is to be used whenever other vehicles are driving ahead, whether oncoming or overtaking.

The international ECE regulations for incandescent headlamps[29] and for high-intensity discharge headlamps[30] specify a beam with a sharp, asymmetric cut-off that prevents significant amounts of light from being thrown into the eyes of drivers of preceding or oncoming cars. Glare control is less stringent in the North American SAE Radiation Standard contained in FMVSS/CMVSS 108.[31]

high beam [edit]

ECE high beam/high beam Symmetrical high beam illumination of the road

High beam (high beam, high beam, high beam) headlights provide a bright, center-weighted light distribution without special control of the light directed into the eyes of other road users. Therefore, they are only suitable for use alone on the road, as the glare they create blinds other drivers.

International ECE regulations allow high-beam headlamps with higher luminous intensity than permitted by North American regulations.[32]

One-way traffic compatibility[ edit ]

Dagen H conversion from left-hand to right-hand traffic. Opaque sticker blocks lens portion for right-hand dipped beam and bears warning: “Not to be removed before September 3, 1967”. Headlights sold just before the switch from left-hand to right-hand traffic in Sweden. Opaque sticker blocks lens portion for right-hand dipped beam and bears warning: “Not to be removed before September 3, 1967”.

Most low beam headlights are specifically designed for use on only one side of the road. Headlights for use in left-hand traffic countries have low beams that “dip to the left”; The light is distributed downward/left to show the driver the road and upcoming signs without dazzling oncoming traffic. Headlamps for right-hand traffic countries have low beams that “dip to the right” with most of their light directed down/right.

Within Europe it is a legal requirement when driving a vehicle with right-hand traffic headlights in a left-hand traffic country or vice versa for a limited time (e.g. on holiday or in transit) to adjust the headlights incorrectly – side light distribution does not dazzle oncoming drivers. This can be accomplished by methods involving the gluing of opaque decals or prismatic lenses to a specific portion of the lens. Some projection-type headlights can be made to produce a true left or right traffic beam by sliding a lever or other movable element in or on the lamp assembly. Many European-coded tungsten (pre-halogen) headlamps manufactured in France by Cibié, Marchal and Ducellier can be adjusted to produce either a low beam for left-hand or right-hand traffic using a two-position lamp socket.

Because headlights on the wrong side of the road dazzle oncoming drivers and do not adequately illuminate the driver’s path, and blackout strips and self-adhesive prismatic lenses reduce headlight safety performance, some countries require all vehicles to be registered or on a permanent or semi-permanent within the country with headlights to be equipped that are designed for proper traffic handling.[34][35] North American vehicle owners sometimes privately import and install Japanese Market (JDM) headlights in their car in the mistaken belief that beam performance will be better, when in reality such misapplication is quite dangerous and illegal.

adequacy[ edit ]

It has been determined that vehicle headlights at speeds in excess of 60 km/h (40 mph) are unable to illuminate a secured clear space.[38][39][40][41][42] It may be unsafe[38] and illegal in some areas[43][44][45] to drive at a higher speed at night.

Use during the day[edit]

In some countries, motor vehicles are required to be equipped with daytime running lights (DRL) to increase the visibility of vehicles moving during the day. Regional regulations regulate how the DRL function can be provided. In Canada, the DRL function required for vehicles manufactured or imported since 1990 may be provided by the headlamps, the fog lamps, the front turn signals maintained on, or by dedicated daytime running lights.[46] For all new cars sold for the first time in the European Union since February 2011, function-specific daytime running lights that do not include the headlights are required.[47] In addition to the EU and Canada, Albania, Argentina,[48] Bosnia and Herzegovina, Colombia (no longer as of August/2011), Iceland, Israel, Macedonia, Norway, Moldova, Russia, Serbia and Uruguay are among the countries that require DRL. [citation required]

Construction, performance and goal[ edit ]

There are two different light distribution and headlight construction standards in use worldwide: the ECE standard, which is permitted or required in virtually all industrialized countries except the USA, and the SAE standard, which is only required in the USA. Japan used to have bespoke lighting regulations similar to US standards but for the left side of the road. However, Japan now adheres to the ECE standard. The differences between the SAE and ECE headlamp standards are mainly the allowable glare of other drivers when the headlights are on low beam (SAE allows much more glare), the minimum amount of light required to be thrown directly onto the road (SAE requires more) , and the specific locations within the beam where minimum and maximum luminous intensities are specified.

ECE low beams are characterized by a pronounced horizontal “cutoff” line at the top of the bar. Below the line is light and above it is dark. On the opposite side of the light cone from oncoming traffic (right in right-hand drive countries, left in left-hand drive countries), this cutoff pans or ramps up to focus the light on traffic signs and pedestrians. SAE low beam may or may not have a cutoff, and when a cutoff is present, it can be of two different general types: VOL, which is conceptually similar to the ECE beam in that the cutoff is at the top left of the beam and directed slightly below horizontal, or VOR, where the cutoff is at the top right side of the beam and pointed toward the horizon.

Proponents of the two headlamp systems condemn the other as inadequate and unsafe: U.S. proponents of the SAE system claim that ECE low-beam cutoff provides short visibility and insufficient illumination of overhead traffic signs, while international proponents of the ECE system claim that the SAE system creates too much glare.[50] Comparative studies have repeatedly shown that neither SAE nor ECE carriers offer little or no overall safety advantage; The acceptance and rejection of the two systems by different countries is mainly based on which system is already in use.[49][51]

In North America, the design, performance, and installation of all automotive lighting devices are governed by the Federal and Canada Motor Vehicle Safety Standard 108, which contains the SAE technical standards. In other parts of the world, internationalized ECE regulations are in force either by reference or by incorporation into each country’s vehicle regulations.

US laws required sealed beam headlamps for all vehicles between 1940 and 1983, and other countries such as Japan, Great Britain and Australia also made extensive use of sealed beams. [When?] In most other countries and in the US since 1984, variable-bulb headlamps have become dominant.

Headlights must be properly aligned.[52] Target regulations vary from country to country and from beam specification to beam specification. In the US, SAE standard headlights are aligned without regard to the mounting height of the headlight. This gives vehicles with high mounted headlights an advantage in visibility, at the cost of increased glare for drivers in lower vehicles. In contrast, the ECE headlight beam angle is linked to the headlight mounting height to give all vehicles approximately the same range of vision and all drivers approximately the same glare.[53]

light color [edit]

White [edit]

Headlights are generally required to produce white light under both ECE and SAE standards. ECE regulation 48 currently stipulates that new vehicles must be equipped with headlamps that emit white light.[9] Different headlamp technologies produce different distinctive types of white light; The white specification is quite large, allowing for a wide range of visible colors from warm white (with a brown-orange-amber tint) to cool white (with a blue-violet tint).

Selective Yellow[ edit ]

Previous ECE regulations also permitted selective yellow light. A 1968 UK research experiment using tungsten (halogen-free) lamps found that visual acuity with selective yellow headlights was about 3% better than with white headlights of the same intensity.[54] A 1976 study in the Netherlands concluded that yellow and white headlights are equivalent in terms of road safety, although yellow light causes less disruptive glare than white light.[55] Researchers note that tungsten incandescent lamps emit only a small amount of the blue light that is blocked by a selective yellow filter,[54] therefore such filtering makes little difference in light output characteristics,[56] and suggest that that headlamps are used. Newer types of sources such as metal halide (HID) lamps can be filtered to emit less visually disturbing light while still having greater light output than halogen lamps.[56]

Selective amber headlights are no longer common, but are allowed in various countries across Europe[vaguely] as well as in non-European regions such as South Korea, Japan[57] and New Zealand[58]. Yellow headlights are permitted in Iceland[59] and vehicle regulations in Monaco still officially require selective amber light from all low[60] and high beam[61] headlights and fog lights, where fitted.[62]

In France, in November 1936, a law passed on the recommendation of the Central Commission for Automobiles and Traffic in General required that selective amber headlights be fitted.[63] The yellow headlight requirement was introduced to reduce driver fatigue from uncomfortable glare.[64] The regulation initially applied to vehicles registered for road traffic from April 1937, but was to be extended to all vehicles from the beginning of 1939 through the retrofitting of older vehicles with selective amber lights. Later stages of implementation were in September 1939 by the outbreak of war. [citation required]

The French yellow light mandate was based on observations made by the French Academy of Sciences in 1934, when the Academy determined that the selective yellow light was less glaring than white light and that the light was less scattered in fog than green or blue light.[ citation needed] Yellow light has been obtained by using yellow glass for the headlight bulb or lens, a yellow coating on a colorless bulb, lens or reflector, or a yellow filter between the bulb and the lens.[65] Filter losses reduced the emitted light intensity by about 18 percent, which may have contributed to the reduced glare.[66]

The mandate was in effect until December 1992,[67] so for many years yellow headlights marked French-registered cars wherever they were seen,[68] although some French drivers are said to have switched to white headlights, despite the requirement for yellow headlights. [69]

The regulation was criticized as a trade barrier in the automotive sector,[70] the French politician Jean-Claude Martinez described it as a protectionist law.[71]

Formal research has found, at best, a small improvement in visual acuity with yellow rather than white headlights,[54][55] and French automaker Peugeot estimated that white headlights produce 20 to 30 percent more light—but without explaining why this estimate was greater than the figure of 15% to 18% measured in formal research – and wanted drivers of their cars to take advantage of additional lighting.[72] In general, country-specific vehicle regulations in Europe were considered a costly annoyance. In a survey published in 1988, automakers gave a range of answers when asked what it cost to deliver a car with yellow headlights to France. General Motors and Lotus said there were no additional costs, Rover said the additional costs were marginal, and Volkswagen said that yellow headlights added 28 German marks to the cost of vehicle production.[73] Addressing the French requirement for amber lights (among other country-specific lighting requirements) has been undertaken as part of efforts towards common technical vehicle standards across the European Community.[67][68] A provision in EU Council Directive 91/663 of December 10, 1991 specified white headlamps for all new vehicle type approvals granted by the EC after January 1, 1993 and specified that EC member states (later EU member states) would no longer be member states from that date to refuse entry to a vehicle that met the lighting standards of the amended document[74] – so France could no longer refuse entry to a vehicle with white headlights. The directive was adopted unanimously by the Council, and thus with the vote of France.[75]

Although no longer required in France, selective amber headlamps remain legal there. The current regulation requires that “every motor vehicle shall be fitted with two or four front lights producing selective amber or white light in the forward direction, providing effective illumination of the roadway in clear conditions at night for 100 metres”.[76]

Optical systems[ edit ]

Lens optics, side view. Light is scattered vertically (shown) and laterally (not shown). A 180mm circular sealed beam lens optic headlamp on a Jaguar E-Type. The grooves and prisms scatter and spread the light collected by the reflector.

Reflector lamps [ edit ]

Lens optics [ edit ]

A light source (filament or arc) is placed at or near the focus of a reflector, which may be parabolic or of non-parabolic complex shape. Fresnel and prismatic optics molded into the headlight lens refract (shift) portions of the light laterally and vertically to provide the required light distribution pattern. Most sealed beam headlights have lens optics.[77]

Reflector optics [ edit ]

From the 1980s, headlight reflectors began to evolve beyond the simple parabola of stamped steel. The 1983 Austin Maestro was the first vehicle to be equipped with Lucas-Carello’s homofocal reflectors, which included parabolic sections of different focal lengths to improve the efficiency of light collection and distribution.[78] CAD technology enabled the development of reflector headlights with non-parabolic, complex-shaped reflectors. These headlights, first marketed by Valeo under their Cibié brand, would revolutionize automotive design.[79]

The US-market 1987 Dodge Monaco/Eagle Premier twins and the European Citroën XM were the first cars with complex-reflector headlamps and faceted optical lenses. General Motors’ Guide Lamp Division in America had experimented with clear-lens complex reflector lamps in the early 1970s and had promising results, [81] but the US-market 1990 Honda Accord was the first to use clear-lens multi-reflector headlamps; these were developed by Stanley in Japan.[82][83]

The optics to distribute the light in the desired pattern are built into the reflector itself, not the lens. Depending on the development tools and techniques used, the reflector can be designed from scratch as a custom shape, or it can start out as a parabola that represents the size and shape of the finished package. In the latter case, the entire surface area is modified to create individual segments with specially calculated, complex contours. The shape of each segment is designed such that their cumulative effect produces the required light distribution pattern.[77]

Modern reflectors are commonly made from compression molded or injection molded plastic, although glass and metal optical reflectors also exist. The reflective surface is vacuum-deposited aluminum with a clear coating to prevent the extremely thin aluminum from oxidizing. When designing and producing headlights with complex reflectors, extremely tight tolerances must be maintained.

Two-beam reflector headlamps [ edit ]

Driving at night is difficult and dangerous due to the glare of oncoming traffic headlights. Headlamps that satisfactorily illuminate the road ahead without causing glare have long been sought. The first solutions were resistor-type dimmer circuits that reduced the intensity of the headlights. This resulted in tilting reflectors and later two-filament lamps with high and low beams.

In a two-filament headlight, there can only be one filament at the exact focal point of the reflector. There are two primary means of creating two distinct beams from a two-filament incandescent lamp in a single reflector.

American system[ edit ]

A filament is located at the focal point of the reflector. The other filament is displaced axially and radially away from the focus. For most 2-filament sealed bars and 9004, 9007 and H13 2-filament replaceable bulbs, the high beam filament is in focus and the low beam filament is out of focus. For use in right-hand traffic countries, the low beam filament is positioned slightly up, forward and to the left of the focal point so that when switched on the beam is widened and shifted slightly down and to the right of the headlight axis. Transverse bulbs like the 9004 can only be used with horizontal filaments, but axial bulbs can be rotated or “clocked” by the headlight designer to optimize the beam pattern or affect the traffic hand of the low beam. The latter is accomplished by clocking the low beam filament in an up-forward-left position to produce a low beam for right-hand traffic, or in an up-forward-right position to produce a low beam for left-hand traffic.

The opposite tactic has also been used with certain sealed beams with two filaments. Placing the low beam filament at the focal point to maximize light collection by the reflector and positioning the high beam filament slightly to the rear-right-down from the focal point. The relative directional shift between the two beams is the same for both techniques – in a country with right-hand traffic, the low beam is slightly down-right and the high beam is slightly up-left, relative to each other – but the lens optics must be adjusted to the chosen filament placements.

European system[ edit ]

The traditional European method of achieving both low and high beam from a single bulb involves two filaments running along the axis of the reflector. The high beam filament is at the focal point, while the low beam filament is about 1 cm in front of the focal point and 3 mm above the axis. Below the low-beam filament is a cup-shaped shield (referred to as the “Graves shield”) spanning a 165° arc. When the filament is illuminated, this shield casts a shadow on the corresponding lower portion of the reflector and blocks downward rays of light that would otherwise strike the reflector and be thrown over the horizon. The bulb is rotated (or “clocked”) within the fixture to position the Graves shield so light can strike a 15° wedge of the lower half of the reflector. This generates the upsweep or upstep characteristic of the ECE low beam distribution. The rotational position of the bulb within the reflector depends on the type of light pattern to be produced and the traffic direction of the market for which the headlamp is intended.

This system was used first with the 1954 Bilux/Duplo R2 tungsten bulb and later with the 1971 halogen H4 bulb. In 1992 US regulations were changed to allow the use of H4 bulbs, renamed HB2 and 9003 and slightly different manufacturing tolerances are prescribed. These are physically and electrically interchangeable with H4 bulbs.[84] Similar optical techniques are used, but with different reflector or lens optics to produce a US beam pattern rather than a European one.

Each system has its advantages and disadvantages. The American system historically allowed a greater total amount of light within the low beam because the entire reflector and lens area is used, but at the same time the American system traditionally offered much less control over upward light causing glare, and for this reason was used outside the US largely rejected. In addition, the American system makes it difficult to produce significantly different low beam and high beam distributions. The high beam is usually a rough copy of the low beam, slightly shifted up and to the left. The European system traditionally produced low beams with less total light, as only 60% of the reflector surface is used to produce the low beam. However, low beam focus and glare limitation are easier to achieve. Also, the bottom 40% of the reflector and lens are reserved for high beam shaping, making it easier to optimize low beam and high beam.

Developments in the 1990s and 2000s[edit]

Complex reflector technology combined with new lamp designs such as H13 allows the creation of European style low and high beam patterns without the use of a Graves Shield, while the 1992 US approval of the H4 lamp used traditional European 60% / 40% optical area split for low beam and high beam common in the US. Therefore, there is no longer necessarily a difference in the active optical surface and the light content of the total beam between US and ECE beams. Dual-beam HID headlights using reflector technology were made using adaptations of both technologies.

Projector lamps (polyellipsoidal) [ edit ]

In this system, a filament is located at a focal point of an ellipsoidal reflector and has a condenser lens at the front of the lamp. In the image plane, between the reflector and the lens, there is an aperture whose projection onto the upper edge of this aperture forms the low-beam limit. The shape of the shadow edge and its exact position in the optical system determine the shape and sharpness of the interface.[77] The shade can be lowered by a solenoid operated pivot to provide a low beam and removed from the light path for the high beam. Such optics are known as BiXenon or BiHalogen projectors. If the cut-off visor is fixed in the light path, separate high beam lamps are required. The condenser lens may have light Fresnel rings or other surface treatments to reduce focus. Modern condenser lenses contain optical features specifically designed to direct some light upward toward retroreflective street sign locations.

Hella introduced ellipsoidal optics for acetylene headlights in 1911, but this optical technology was not used for decades after the electrification of vehicle lighting. The first modern polyellipsoidal (projector) automotive lamp was the Super-Lite, an auxiliary lamp manufactured in a joint venture between Chrysler Corporation and Sylvania and installed as an option in 1969 and 1970 full-size Dodge automobiles. It used an 85 watt transverse filament tungsten-halogen bulb and was intended as a center beam to extend the range of the low beam during turnpike cruising when low beam alone was insufficient but high beam would create excessive glare.

Projector headlights appeared on the 1981 Audi Quartz, a concept car designed by Pininfarina for the Geneva Motor Show.[86] Developed more or less simultaneously in Germany by Hella and Bosch and in France by Cibié, the projector’s low beam enabled precise beam focusing and a much smaller diameter optical package, albeit much deeper, for any given beam power. The 1986 BMW 7 Series (E32) was the first production car to use polyellipsoidal low beam headlights. The main disadvantage of this type of headlamp is the need to accommodate the physical depth of the assembly, which can extend well back into the engine compartment.

Light sources [ edit ]

Tungsten[ edit ]

The first electric headlight light source was the tungsten filament, which worked in a vacuum or inert gas atmosphere within the headlight bulb or sealed beam. Compared to newer technology light sources, tungsten filaments emit small amounts of light in relation to the power they consume. In addition, during normal operation of such lamps, tungsten boils off the surface of the filament and condenses on the bulb glass, blackening it. This reduces the light output of the filament and blocks some of the light that would pass through an unblackened bulb glass, although blackening was less of an issue with sealed beam units. their large internal surface area minimized the thickness of the tungsten agglomerate. For these reasons, simple tungsten filaments are all but obsolete in automotive headlight service.

Tungsten-Halogen (also called “Quartz-Halogen”, “Quartz-Iodine”, “Iodine Cycle” etc.) technology increases the effective luminous efficacy of a tungsten filament: When operated at a higher filament temperature resulting in more lumen output per watt input, a tungsten halogen lamp has a much longer brightness life than similar filaments that operate without the halogen regeneration cycle. With the same luminosity, the halogen cycle lamps also have a longer service life. Light sources for halogen headlamps developed in Europe are generally configured to provide more light for the same power consumption than their lower wattage pure tungsten counterparts. In contrast, many US-based designs are configured to reduce or minimize power consumption while maintaining light output above minimum legal requirements; Some US tungsten-halogen headlamp light sources produce less initial light than their non-halogen counterparts. A low theoretical fuel economy benefit and reduced vehicle construction costs through lower wire and switch ratings were the claimed benefits when American industry first chose to implement tungsten-halogen technology. There was an improvement in visibility with US halogen high beams, which for the first time were allowed to produce 150,000 candelas (cd) per vehicle, double the non-halogen limit of 75,000 cd but still well below the international European limit of 225,000 cd. After interchangeable halogen lamps were allowed in US headlamps in 1983, US lamp development focused on long lamp life and low power consumption, while European designs continued to prioritize optical precision and maximum performance.[90]

The H1 lamp was the first halogen-halogen headlamp light source. It was introduced in 1962 by a consortium of European bulb and headlamp manufacturers. This bulb has a single axial filament that draws 55 watts at 12.0 volts and produces 1550 lumens ±15% when operating at 13.2 volts. H2 (55W @ 12.0V, 1820lm @ 13.2V) followed in 1964 and the Filament H3 (55W @ 12.0V, 1450lm ± 15%) in 1966. H1 is still commonly used in low beam , high beam and additional fog and high beams are used, as well as H3. The H2 is no longer a current type as it requires a complicated lamp socket interface to the lamp, has a short lifespan and is difficult to handle. For these reasons, H2 was withdrawn from ECE Regulation 37 for use in new lamp designs (although H2 filament lamps are still manufactured for replacement purposes in existing lamps), but H1 and H3 remain current and both of these lamps have been legalized in the States im Year 1993.[92][93] Newer single filament bulb designs include H7 (55W @ 12.0V, 1500lm ±10% @ 13.2V), H8 (35W @ 12.0V, 800lm ±15% @ 13.2V) , H9 (65 W at 12.0 V, 2100 lm ±10% at 13.2 V) and H11 (55 W at 12.0 V, 1350 lm ±10% at 13.2 V).[94] 24 volt versions of many bulb types are available for use in trucks, buses and other commercial and military vehicles.

H7 bulb

The first dual-filament halogen lamp that produced both low and high beam, the H4 (60/55 W at 12 V, 1650/1000 lm ±15 % at 13.2 V),[94] was launched in 1971[ 13] and quickly became the dominant headlight lamp worldwide, except in the United States, where the H4 is still not legal for automotive use. In 1989, the Americans created their own standard for an incandescent bulb called the HB2: almost identical to the H4, except with tighter constraints on filament geometry and positional variance [95][96] and power consumption and light output expressed at the US test voltage of 12.8 v.[97]

The first US halogen headlight bulb, introduced in 1983, was the HB1/9004. It’s a 12.8-volt, dual-filament, transverse design that produces 700 lumens on low beam and 1200 lumens on high beam. The 9004 is rated for 65 watts (high beam) and 45 watts (low beam) at 12.8 volts. Other halogen lamps approved in the US are HB3 (65W, 12.8V), HB4 (55W, 12.8V), and HB5 (65/55 watt, 12.8V).[98] All European designed and internationally approved bulbs except H4 are currently approved for use in headlamps that meet US requirements.

Halogen infrared reflection (HIR) [ edit ]

A further development of the tungsten-halogen bulb has a dichroic coating that transmits visible light and reflects infrared radiation. The glass in such a flask can be spherical or tubular. The reflected infrared radiation hits the filament, which is located in the center of the glass envelope, and heats the filament more than can be achieved by resistance heating alone. The overheated filament emits more light without increasing power consumption.[99]

High Intensity Discharge (HID) [ edit ]

HID projector low beam headlights illuminated on a Lincoln MKS

High-intensity discharge (HID) lamps produce light using an arc rather than a filament. The high intensity of the arc comes from metal salts that are vaporized in the arc chamber. These lamps have higher efficiency than tungsten lamps. Due to the greater amounts of light available from HID bulbs compared to halogen bulbs, HID headlights that produce a specific beam pattern can be made smaller than halogen headlights that produce a comparable beam pattern. Alternatively, the larger size can be retained, in which case the HID headlight can produce a more robust beam pattern. [original research?]

Automotive HID can be referred to as “xenon headlights” when in fact they are metal halide lamps containing xenon gas. The xenon gas allows the lamps to produce minimally sufficient light immediately upon start-up and shortens the run-up time. The use of argon, as commonly used in streetlights and other stationary metal halide lamp applications, results in lamps taking several minutes to reach full output.

The light from HID headlights can have a noticeable blue cast compared to headlights with tungsten filament.

Retrofit [ edit ]

When a halogen headlamp is retrofitted with an HID bulb, the light distribution and output are changed.[100] In the United States, vehicle lighting that does not comply with FMVSS 108 is not legal for use on the road.[100] With the changed light distribution, glare is created and the type approval or registration of the headlamp becomes invalid, making the headlamp no longer road legal in some areas.[101] In the US, suppliers, importers, and sellers who offer non-compliant kits face civil penalties. As of October 2004, NHTSA had investigated 24 suppliers and all resulted in sales terminations or recalls.[102]

In Europe and the many non-European countries that apply ECE regulations, even HID headlights designed as such must be equipped with lens cleaning and automatic self-leveling systems, except on motorcycles.[101] These systems are typically absent from vehicles not originally equipped with HID lights.

history [edit]

In 1992 the first production low beam HID headlights were manufactured by Hella and Bosch from 1992 for optional availability in the BMW 7 Series. This first system used a built-in, non-replaceable bulb with no UV-blocking glass shield or touch-sensitive electrical safety switch, designated D1[103]—a designation that would be reused years later for an entirely different type of lamp. The AC ballast is about the size of a brick. 1996 was the first American attempt at HID headlamps on the 1996-1998 Lincoln Mark VIII, which used reflector headlamps with an unmasked Sylvania integral ignition lamp and was designated the Type 9500. This was the only system to run on DC power, as reliability was inferior to AC systems. [citation needed] The Type 9500 system was not used on any other model and was discontinued after Sylvania was acquired by Osram in 1997. [citation needed] All HID headlights worldwide currently use the standardized air-conditioning-powered bulbs and ballasts. In 1999, the world’s first HID headlights for low and high beam were introduced in the Mercedes-Benz CL-Class.[104]

operation [edit]

HID headlight bulbs do not operate on low voltage DC, so they require a ballast with either an internal or external ignitor. The ignitor is integrated into the bulb on D1 and D3 systems and is either a separate unit or part of the ballast on D2 and D4 systems. The ballast controls the current to the bulb. Ignition and ballast operation takes place in three stages:

Ignition: Similar to a spark plug, a high-voltage pulse creates an arc that ionizes the xenon gas and creates a conductive channel between the tungsten electrodes. Electrical resistance is reduced within the channel and current flows between the electrodes. Initial phase: The incandescent lamp is operated with a controlled overload. Since the arc is operated at high power, the temperature in the capsule rises quickly. The metal salts evaporate, the arc is intensified and spectrally completed. The resistance between the electrodes also decreases; the electronic ballast registers this and automatically switches to continuous operation. Continuous operation: All metal salts are in the vapor phase, the arc has its stable form and the luminous efficiency has reached its nominal value. The ballast now delivers a stable electrical output so that the arc does not flicker. The stable operating voltage is 85 volts AC in D1 and D2 systems, 42 volts AC in D3 and D4 systems. The frequency of the square-wave alternating current is typically 400 hertz or more.

Example headlight display

The command is often located near the steering wheel, and a special indicator is displayed on the dashboard.

Types of pears [ edit ]

HID headlamps produce between 2,800 and 3,500 lumens from between 35 and 38 watts of electrical power, while halogen bulbs produce between 700 and 2,100 lumens from between 40 and 72 watts at 12.8V.

Current production lamp categories are D1S, D1R, D2S, D2R, D3S, D3R, D4S and D4R. The D stands for Discharge, the number is the type designation. The last letter describes the outer shield. The arc in an HID headlight bulb produces significant short-wavelength ultraviolet (UV) light, but none of this escapes the bulb because of a UV-absorbing tempered glass shield built around the bulb’s arc tube. This is important to prevent deterioration of UV-sensitive components and materials in headlamps, such as headlights. B. polycarbonate lenses and reflector hard coatings to prevent. “S” lamps – D1S, D2S, D3S and D4S – have a simple glass shield and are used primarily in projection optics. “R” bulbs – D1R, D2R, D3R and D4R – are designed for use in reflector headlamp optics. They have an opaque mask that obscures certain areas of the shield, making it easier to optically generate the cutoff near the peak of a low beam distribution. Automotive HID bulbs, despite being shielded, emit significant light in the near UV range.

color [edit]

The correlated color temperature of factory-installed HID automotive headlights ranges from 4200K, while tungsten-halogen lamps range from 3000K to 3550K. The power spectral distribution (SPD) of an HID automotive headlight is discontinuous and peaky, while the SPD of an incandescent lamp, like that of the sun, is a continuous curve. In addition, the Color Rendering Index (CRI) of Tungsten Halogen fixtures (98) is much closer to standardized sunlight (100) than that of HID fixtures (~75). Studies have not shown a significant safety effect of this level of CRI variation in headlights.[107][108][109][110]

Benefits [edit]

Increased security[edit]

HID automotive bulbs offer around 3000 lumens and 90 Mcd/m2 compared to 1400 lumens and 30 Mcd/m2 [disputed – discuss] offered by halogen bulbs. In a headlight optic designed for use with an HID bulb, it produces more usable light. Studies have shown that drivers with good HID headlights react faster and more accurately to road obstacles than with halogen headlights.[111] Therefore, good HID headlights contribute to driving safety.[112] The opposite argument is that glare from HID headlights can affect road safety by interfering with other drivers’ vision.

Effectiveness and output[ edit ]

Luminous efficacy is the measure of how much light is produced and how much energy is used. HID lamps are more efficient than halogen lamps. The most powerful halogen lamps H9 and HIR1 generate 2100 to 2530 lumens from around 70 watts at 13.2 volts. A D2S HID lamp produces 3200 lumens from approximately 42 watts under stable operation.[94] The reduced power consumption means lower fuel consumption and therefore lower CO2 emissions per vehicle equipped with HID lighting (1.3g/km assuming 30% of the engine runtime is spent with the lights on).

longevity [edit]

The average lifespan of an HID lamp is 2000 hours compared to 450 to 1000 hours for a halogen lamp.[113]

Disadvantages [edit]

Glare [ edit ]

Fahrzeuge, die mit HID-Scheinwerfern ausgestattet sind (außer Motorräder), müssen gemäß ECE-Regelung 48 auch mit Scheinwerferglas-Reinigungssystemen und automatischer Leuchtweitenregulierung ausgestattet sein. Beide Maßnahmen sollen die starke Blendung anderer Verkehrsteilnehmer durch leistungsstarke Scheinwerfer reduzieren. In Nordamerika gilt ECE R48 nicht, und Linsenreiniger und Strahlnivellierer sind zwar erlaubt, aber nicht erforderlich.[114] HID-Scheinwerfer sind in den USA deutlich weniger verbreitet, wo sie zu erheblichen Blendbeschwerden geführt haben.[115] Wissenschaftliche Untersuchungen zur Blendung durch Scheinwerfer haben gezeigt, dass das Licht von HID-Scheinwerfern bei jeder gegebenen Intensitätsstufe um 40 % greller ist als das Licht von Wolfram-Halogen-Scheinwerfern.[116]

Quecksilbergehalt [ bearbeiten ]

HID-Scheinwerferlampentypen D1R, D1S, D2R, D2S und 9500 enthalten das giftige Schwermetall Quecksilber. Die Entsorgung von quecksilberhaltigen Fahrzeugteilen wird weltweit zunehmend reglementiert, beispielsweise durch die US-amerikanischen EPA-Vorschriften. Neuere HID-Lampendesigns D3R, D3S, D4R und D4S, die seit 2004 in Produktion sind, enthalten kein Quecksilber, sind jedoch weder elektrisch noch physikalisch mit Scheinwerfern kompatibel, die für frühere Lampentypen entwickelt wurden.

Kosten [Bearbeiten]

HID-Scheinwerfer sind deutlich teurer in der Herstellung, Installation, Anschaffung und Reparatur. Die zusätzlichen Kosten der HID-Lampen können die Kraftstoffkosteneinsparungen durch ihren reduzierten Stromverbrauch übersteigen, obwohl ein Teil dieses Kostennachteils durch die längere Lebensdauer der HID-Lampe im Vergleich zu Halogenlampen ausgeglichen wird.

LED [Bearbeiten]

LED-Scheinwerfer innen

Zeitachse [ bearbeiten ]

Automobilscheinwerferanwendungen mit Leuchtdioden (LEDs) werden seit 2004 entwickelt.[119][120]

2006 wurden die ersten serienmäßigen LED-Abblendlichter werkseitig im Lexus LS 600h / LS 600h L verbaut. Die Fernlicht- und Blinkerfunktionen nutzten Glühlampen. Die Stirnlampe wurde von Koito geliefert.

2007 wurden die ersten Scheinwerfer mit allen Funktionen von LEDs, geliefert von AL-Automotive Lighting, am Sportwagen V10 Audi R8 (außer in Nordamerika) eingeführt.[121]

2009 wurden Hella-Scheinwerfer des Cadillac Escalade Platinum 2009 die ersten Voll-LED-Scheinwerfer für den nordamerikanischen Markt.

Im Jahr 2010 wurden die ersten Voll-LED-Scheinwerfer mit adaptivem Fernlicht und dem von Mercedes als „Intelligent Light System“ bezeichneten 2011er Mercedes CLS eingeführt.

Im Jahr 2013 wurden die ersten digital gesteuerten blendfreien Voll-LED-Adaptivscheinwerfer “Matrix LED” von Audi im modellgepflegten A8 mit 25 einzelnen LED-Segmenten eingeführt.[123] Das System dimmt das Licht, das direkt auf entgegenkommende und vorausfahrende Fahrzeuge scheinen würde, wirft aber weiterhin sein volles Licht auf die Zonen zwischen und neben ihnen. Das funktioniert, weil das LED-Fernlicht in viele einzelne Leuchtdioden aufgeteilt ist. Fernlicht-LEDs in beiden Scheinwerfern sind in einer Matrix angeordnet und passen sich in Millisekunden vollelektronisch an die Umgebung an. Sie werden von einer Steuereinheit individuell ein- und ausgeschaltet oder gedimmt. Zusätzlich fungieren die Scheinwerfer auch als Kurvenlicht. Anhand prädiktiver Streckendaten der MMI Navigation plus wird der Fokus des Lichtkegels in Richtung Kurve verschoben, noch bevor der Fahrer am Lenkrad dreht. Im Jahr 2014: Mercedes-Benz führte 2014 bei der überarbeiteten CLS-Klasse eine ähnliche Technologie namens Multibeam LED mit 24 einzelnen Segmenten ein.

Ab 2010 lieferten LED-Scheinwerfer, wie sie für den Toyota Prius erhältlich sind, eine Leistung zwischen Halogen- und HID-Scheinwerfern,[125] mit einem etwas geringeren Stromverbrauch des Systems als bei anderen Scheinwerfern, längerer Lebensdauer und flexibleren Gestaltungsmöglichkeiten.[126][127]. ] Mit der Weiterentwicklung der LED-Technologie wurde vorhergesagt, dass sich die Leistung von LED-Scheinwerfern verbessern wird, um sich der von HID-Scheinwerfern anzunähern, sie zu erreichen und vielleicht eines Tages zu übertreffen.[128] Das geschah Mitte 2013, als die Mercedes S-Klasse mit LED-Scheinwerfern ausgestattet wurde, die eine höhere Leistung als vergleichbare HID-Setups lieferten.[129]

Kalte Linsen [ bearbeiten ]

Vor LEDs strahlten alle in Scheinwerfern verwendeten Lichtquellen (Wolfram, Halogen, HID) Infrarotenergie aus, die angesammelten Schnee und Eis von einer Scheinwerferlinse auftauen und eine weitere Ansammlung verhindern kann. LEDs nicht. Einige LED-Scheinwerfer leiten Wärme vom Kühlkörper auf der Rückseite der LEDs zur Innenseite der Frontlinse, um sie aufzuwärmen, während bei anderen keine Vorkehrungen zum Auftauen der Linse getroffen werden.

Lasers [ edit ]

Eine Laserlampe verwendet Spiegel, um einen Laser auf einen Leuchtstoff zu richten, der dann ein Licht emittiert. Laserlampen verbrauchen halb so viel Strom wie LED-Lampen. Sie wurden von Audi erstmals für den Einsatz als Scheinwerfer bei den 24 Stunden von Le Mans entwickelt.[130]

2014 wurde der BMW i8 als erstes Serienautomobil mit einem auf dieser Technologie basierenden Zusatzfernlicht verkauft.[131] Der limitierte Audi R8 LMX verwendet Laser für seine Spotlight-Funktion, die eine Beleuchtung für Hochgeschwindigkeitsfahrten bei schlechten Lichtverhältnissen bietet. Der Rolls-Royce Phantom VIII verwendet Laserscheinwerfer mit einer Fernlichtreichweite von über 600 Metern.[132]

Automatische Scheinwerfer [ bearbeiten ]

Automatische Systeme zum Aktivieren der Scheinwerfer sind seit Mitte der 1950er Jahre erhältlich, ursprünglich nur bei amerikanischen Luxusmodellen wie Cadillac, Lincoln und Imperial.[133] Grundlegende Implementierungen schalten die Scheinwerfer in der Dämmerung ein und im Morgengrauen aus. Moderne Implementierungen verwenden Sensoren, um die Menge an Außenlicht zu erfassen. UN R48 schreibt seit dem 30. Juli 2016 den Einbau von automatischen Scheinwerfern vor. Mit einem ausgestatteten und betriebenen Tagfahrlicht sollte sich das Abblendlicht automatisch einschalten, wenn das Auto in Umgebungsbedingungen mit weniger als 1.000 Lux fährt, z. B. in einem Tunnel und in dunkle Umgebungen. Während in solchen Situationen ein Tagfahrlicht den entgegenkommenden Fahrzeugführer besser blenden würde, was wiederum das Sehvermögen des entgegenkommenden Fahrzeugführers beeinflussen würde, so dass durch automatisches Umschalten des Tagfahrlichts auf das Abblendlicht das inhärente Sicherheitsmängel behoben und Sicherheitsnutzen gewährleistet werden.

Strahlzielsteuerung [ bearbeiten ]

Leuchtweitenregulierung [ bearbeiten ]

headlight range adjustment

Der Citroën 2CV von 1948 wurde in Frankreich mit einem manuellen Scheinwerfer-Nivellierungssystem eingeführt, das vom Fahrer mit einem Knopf über ein mechanisches Gestänge gesteuert wurde. Dadurch konnte der Fahrer die vertikale Ausrichtung der Scheinwerfer anpassen, um die Passagier- und Frachtlast im Fahrzeug auszugleichen. 1954 führte Cibié ein automatisches Scheinwerfer-Nivellierungssystem ein, das mit dem Aufhängungssystem des Fahrzeugs verbunden ist, um die Scheinwerfer unabhängig von der Fahrzeuglast ohne Eingriff des Fahrers korrekt ausgerichtet zu halten. Das erste Fahrzeug, das so ausgestattet war, war der Panhard Dyna Z. Ab den 1970er Jahren forderten Deutschland und einige andere europäische Länder ferngesteuerte Leuchtweitenregulierungssysteme, die es dem Fahrer ermöglichen, die Ausrichtung der Lampen mittels eines Armaturenbrett-Steuerhebels oder zu senken Knopf, wenn das Heck des Fahrzeugs mit Passagieren oder Fracht beladen ist, was dazu führen würde, dass der Ausrichtungswinkel der Lampen erhöht und Blendung erzeugt wird. Solche Systeme verwenden typischerweise Schrittmotoren am Scheinwerfer und einen Drehschalter am mit “0”, “1”, “2”, “3” markierten Strich für unterschiedliche Strahlhöhen, wobei “0” die “normale” (und höchste) Position ist wenn das Auto leicht beladen ist.

Die internationalisierte ECE-Regelung 48, die in den meisten Teilen der Welt außerhalb Nordamerikas in Kraft ist, legt derzeit einen begrenzten Bereich fest, innerhalb dessen die vertikale Ausrichtung der Scheinwerfer unter verschiedenen Fahrzeuglastbedingungen beibehalten werden muss; Wenn das Fahrzeug nicht mit einer adaptiven Aufhängung ausgestattet ist, die ausreicht, um die Scheinwerfer unabhängig von der Beladung korrekt ausgerichtet zu halten, ist ein Scheinwerfer-Nivellierungssystem erforderlich.[9] Die Verordnung sieht eine Verschärfung dieser Blendschutzmaßnahme vor, wenn das Fahrzeug über Scheinwerfer mit Abblendlichtquelle(n) verfügt, die mehr als 2.000 Lumen erzeugen – beispielsweise Xenon-Glühlampen und bestimmte Hochleistungshalogenlampen. Solche Fahrzeuge müssen mit Scheinwerfer-Selbstnivellierungssystemen ausgestattet sein, die den Neigungsgrad des Fahrzeugs aufgrund der Ladung und der Straßenneigung erfassen und die vertikale Ausrichtung der Scheinwerfer automatisch anpassen, um den Strahl korrekt ausgerichtet zu halten, ohne dass der Fahrer etwas unternehmen muss.[9 ]

Leveling systems are not required by the North American regulations. A 2007 study, however, suggests automatic levelers on all headlamps, not just those with high-power light sources, would give drivers substantial safety benefits of better seeing and less glare.[134]

Directional headlamps [ edit ]

Directional (steering) headlamp (middle) on a 1928 Willys-Knight 70A Touring

Directional (steering) headlamps on a Citroën DS – the driver can see clearly through curves.

These provide improved lighting for cornering. Some automobiles have their headlamps connected to the steering mechanism so the lights will follow the movement of the front wheels. Czechoslovak Tatra was an early implementer of such a technique, producing in the 1930s a vehicle with a central directional headlamp. The American 1948 Tucker Sedan was likewise equipped with a third central headlamp connected mechanically to the steering system.

The 1967 French Citroën DS and 1970 Citroën SM were equipped[135] with an elaborate dynamic headlamp positioning system that adjusted the inboard headlamps’ horizontal and vertical position in response to inputs from the vehicle’s steering and suspension systems.

At that time US regulations required this system to be removed from those models sold in the U.S.[136][failed verification]

The D series cars equipped with the system used cables connecting the long-range headlamps to a lever on the steering relay while the inner long-range headlamps on the SM used a sealed hydraulic system using a glycerin-based fluid instead of mechanical cables.[citation needed] Both these systems were of the same design as their respective cars’ headlamp leveling systems. The cables of the D system tended to rust in the cable sheaths while the SM system gradually leaked fluid, causing the long-range lamps to turn inward, looking “cross-eyed.” A manual adjustment was provided but once it was to the end of its travel the system required refilling with fluid or replacement of the tubes and dashpots.[citation needed]

Citroën SM non-US market vehicles were equipped with heating of the headlamp cover glasses, this heat supplied by ducts carrying warm air from the radiator exhaust to the space between the headlamp lenses and the cover glasses.[citation needed] This provided demisting/defogging of the entire interior of the cover glasses, keeping the glass clear of mist/fog over the entire surface. The glasses have thin stripes on their surfaces that are heated by the headlight beams; however, the ducted warm air provides demisting when the headlamps are not turned on. The glasses’ stripes on both D and SM cars appear similar to rear windshield glass electric defogger heating strips, but they are passive, not electrified.[citation needed]

Advanced front-lighting system (AFS) [ edit ]

Beginning in the 2000s, there was a resurgence in interest in the idea of moving or optimizing the headlight beam in response not only to vehicular steering and suspension dynamics, but also to ambient weather and visibility conditions, vehicle speed, and road curvature and contour. A task force under the EUREKA organization, composed primarily of European automakers, lighting companies and regulators began working to develop design and performance specifications for what is known as Adaptive Front-Lighting Systems, commonly AFS.[137] Manufacturers such as BMW, Toyota,[138] Škoda,[139] and Vauxhall/Opel[140] have released vehicles equipped with AFS since 2003.

Rather than the mechanical linkages employed in earlier directional-headlamp systems, AFS relies on electronic sensors, transducers, and actuators. Other AFS techniques include special auxiliary optical systems within a vehicle’s headlamp housings. These auxiliary systems may be switched on and off as the vehicle and operating conditions call for light or darkness at the angles covered by the beam the auxiliary optics produce. A typical system measures steering angle and vehicle speed to swivel the headlamps.[141] The most advanced AFS systems use GPS signals to anticipate changes in road curvature, rather than simply reacting to them.

Automatic beam switching [ edit ]

Even when conditions would warrant the use of high-beam headlamps, drivers often do not use them.[142] There have long been efforts, particularly in America, to devise an effective automatic beam selection system to relieve the driver of the need to select and activate the correct beam as traffic, weather, and road conditions change. General Motors introduced the first automatic headlight dimmer called the ‘Autronic Eye’ in 1952 on their Cadillac, Buick, and Oldsmobile models; the feature was offered in other GM vehicles starting in 1953.[143][144] The system’s phototube and associated circuitry were housed in a gunsight-like tube atop the dashboard. An amplifier module was located in the engine compartment that controlled the headlight relay using signals from the dashboard-mounted tube unit.

This pioneering setup gave way in 1958 to a system called ‘GuideMatic’ in reference to GM’s Guide lighting division. The GuideMatic had a more compact dashtop housing and a control knob that allowed the driver to adjust the system’s sensitivity threshold to determine when the headlamps would be dipped from high to low beam in response to an oncoming vehicle. By the early 1970s, this option was withdrawn from all GM models except Cadillac, on which GuideMatic was available through 1988. The photosensor for this system used an amber lens, and the adoption of retro-reflective yellow road signs, such as for oncoming curves, caused them to dim prematurely – possibly leading to their discontinuation.[citation needed]

Ford- and Chrysler-built vehicles were also available with the GM-made dimmers from the 1950s through the 1980s.[citation needed] A system called ‘AutoDim’ was offered on several Lincoln models starting in the mid-1950s, and eventually the Ford Thunderbird and some Mercury models[vague] offered it as well.[citation needed] Premium Chrysler and Imperial models offered a system called Automatic Beam Control throughout the 1960s and early 1970s.[citation needed]

Rabinow dimmer [ edit ]

Though the systems based on photoresistors evolved, growing more compact and moving from the dashboard to a less conspicuous location behind the radiator grill, they were still unable to reliably discern headlamps from non-vehicular light sources such as streetlights. They also did not dip to low beam when the driver approached a vehicle from behind, and they would spuriously dip to low beam in response to road sign reflections of the vehicle’s own high beam headlamps. American inventor Jacob Rabinow devised and refined a scanning automatic dimmer system impervious to streetlights and reflections,[145] but no automaker purchased the rights, and the problematic photoresistor type remained on the market through the late 1980s.[146]

Bone-Midland lamps [ edit ]

In 1956, the inventor Even P. Bone developed a system where a vane in front of each headlight moved automatically and caused a shadow in front of the approaching vehicle, allowing for high beam use without glare for the approaching driver. The system, called “Bone-Midland Lamps,” was never taken up by any car manufacturer.[147]

Camera-based dimmer [ edit ]

Present systems based on imaging CMOS cameras can detect and respond appropriately to leading and oncoming vehicles while disregarding streetlights, road signs, and other spurious signals. Camera-based beam selection was first released in 2005 on the Jeep Grand Cherokee and has since then been incorporated into comprehensive driver assistance systems by automakers worldwide. The headlights will dim when a bright reflection bounces off of a street sign.

Intelligent Light System [ edit ]

Intelligent Light System on A-Class

Intelligent Light System is a headlamp beam control system introduced in 2006 on the Mercedes-Benz E-Class (W211)[148] which offers five different bi-xenon light functions,[149] each of which is suited to typical driving or weather conditions:

Country mode

Motorway mode

Enhanced fog lamps

Active light function (Advanced front-lighting system (AFS))

Cornering light function

Adaptive highbeam [ edit ]

Adaptive Highbeam Assist is Mercedes-Benz’ marketing name for a headlight control strategy that continuously automatically tailors the headlamp range so the beam just reaches other vehicles ahead, thus always ensuring maximum possible seeing range without glaring other road users.[150] It was first launched in the Mercedes E-class in 2009.[149] It provides a continuous range of beam reach from a low-aimed low beam to a high-aimed high beam, rather than the traditional binary choice between low and high beams.

The range of the beam can vary between 65 and 300 meters, depending on traffic conditions. In traffic, the low beam cutoff position is adjusted vertically to maximise seeing range while keeping glare out of leading and oncoming drivers’ eyes. When no traffic is close enough for glare to be a problem, the system provides full high beam. Headlamps are adjusted every 40 milliseconds by a camera on the inside of the front windscreen which can determine distance to other vehicles.[151] The S-Class, CLS-Class and C-Class also offer this technology. In the CLS, the adaptive high beam is realised with LED headlamps – the first vehicle producing all adaptive light functions with LEDs. Since 2010 some Audi models with Xenon headlamps are offering a similar system: adaptive light with variable headlight range control.[152]

In Japan, the Toyota Crown, Toyota Crown Majesta, Nissan Fuga and Nissan Cima offer the technology on top level models.

Until Feb 2022, this technology had been illegal in the US, as FMVSS 108 specifically stated that headlamps must have dedicated high and low beams to be deemed road-legal. An infrastructure bill enacted in November 2021 included language that directs the National Highway Traffic Safety Administration to amend FMVSS 108 to allow the use of this technology, and set a two-year deadline for implementing this change.[153][154] In Feb 2022, the NHTSA amended FMVSS 108 allowing adaptive headlights for use in the US.[155]

Glare-free high beam and pixel light [ edit ]

A glare-free high beam is a camera-driven dynamic lighting control strategy that selectively shades spots and slices out of the high beam pattern to protect other road users from glare, while continuously providing the driver with maximum seeing range.[156] The area surrounding other road users is constantly illuminated at high beam intensity, but without the glare that would typically result from using uncontrolled high beams in traffic.[157] This constantly changing beam pattern requires complex sensors, microprocessors, and actuators because the vehicles which must be shadowed out of the beam are constantly moving. The dynamic shadowing can be achieved with movable shadow masks shifted within the light path inside the headlamp. Or, the effect can be achieved by selectively darkening addressable LED emitters or reflector elements, a technique known as pixel light.[158]

The first mechanically controlled (non-LED), glare-free high beam was Volkswagen’s “Dynamic Light Assist” package,[159] which was introduced in 2010 on the Volkswagen Touareg,[160] Phaeton,[161] and Passat. In 2012, the facelifted Lexus LS (XF40) introduced an identical bi-xenon system: “Adaptive High-beam System”.

The first mechanically controlled LED glare-free headlamps were introduced in 2012 on BMW 7 Series: “Selective Beam” (anti-dazzle high-beam assistant). In 2013 Mercedes-Benz introduced the same LED system: “Adaptive Highbeam Assist Plus”.

The first digitally controlled LED glare-free headlamps were introduced in 2013 on Audi A8. See LED section.

Care [ edit ]

Headlamp systems require periodic maintenance. Sealed beam headlamps are modular; when the filament burns out, the entire sealed beam is replaced. Most vehicles in North America made since the late 1980s use headlamp lens-reflector assemblies that are considered a part of the car, and just the bulb is replaced when it fails. Manufacturers vary the means by which the bulb is accessed and replaced. Headlamp aim must be properly checked and adjusted frequently, for misaimed lamps are dangerous and ineffective.[53]

Over time, the headlamp lens can deteriorate. It can become pitted due to abrasion of road sand and pebbles and can crack, admitting water into the headlamp. “Plastic” (polycarbonate) lenses can become cloudy and discoloured. This is due to oxidation of the painted-on lens hardcoat by ultraviolet light from the sun and the headlamp bulbs. If it is minor, it can be polished out using a reputable brand of a car polish that is intended for restoring the shine to chalked paint. In more advanced stages, the deterioration extends through the actual plastic material, rendering the headlamp useless and necessitating complete replacement. Sanding or aggressively polishing the lenses, or plastic headlight restoration, can buy some time, but doing so removes the protective coating from the lens, which when so stripped will deteriorate faster and more severely. Kits for a quality repair are available that allow the lens to be polished with progressively finer abrasives, and then be sprayed with an aerosol of ultra violet resistant clear coating.

The reflector, made out of vaporized aluminum deposited in an extremely thin layer on a metal, glass, or plastic substrate, can become dirty, oxidised, or burnt, and lose its specularity. This can happen if water enters the headlamp, if bulbs of higher than specified wattage are installed, or simply with age and use. Reflectors thus degraded, if they cannot be cleaned, must be replaced.

Lens cleaners [ edit ]

Headlamp washers in action on a Skoda Yeti

Dirt buildup on headlamp lenses increases glare to other road users, even at levels too low to reduce seeing performance significantly for the driver.[citation needed] Therefore, headlamp lens cleaners are required by UN Regulation 48 on vehicles equipped with low-beam headlamps using light sources that have a reference luminous flux of 2,000 lumens or more.[9] This includes all HID headlamps and some high-power halogen units. Some cars have lens cleaners fitted even where the regulations do not require them. North America, for example, does not use UN regulations, and FMVSS 108 does not require lens cleaners on any headlamps, though they are permitted.

Lens cleaning systems come in two main varieties: a small motor-driven rubber wiper or brush conceptually similar to windshield wipers, or a fixed or telescopic high-pressure sprayer which cleans the lenses with a spray of windshield washer fluid. Most recent lens cleaning systems are of the spray type because UN regulations do not permit mechanical cleaning systems (wipers) to be used with plastic-lens headlamps,[9] and most recent headlamps have plastic lenses. Some cars with retractable headlamps, such as the original Mazda MX-5, have a squeegee at the front of the lamp recess which automatically wipes the lenses as they are raised or lowered, although it does not provide washer fluid.[citation needed]

See also[edit]

References[ edit ]

Xenon.

Conventional halogen lighting technology is largely exhausted in terms of light properties. Xenon lights bring a significant improvement in this area. Xenon headlights make driving at night easier thanks to the spectrum of the xenon light that is similar to daylight and thus offer a high level of safety. Xenon headlights are characterized by their long range and perfect lateral spread. Other advantages include low energy consumption and the life of the bulbs over the entire life of the vehicle. The light source is a so-called gas discharge lamp. A flashover between two electrodes in the xenon gas atmosphere in the lamp bulb results in an ionized gas tube through which electric current flows. This causes the gas mixture to glow in the form of an arc. Sophisticated electronics are required to operate these lamps in order to generate the high ignition voltage of between 18,000 and 30,000 volts in order to ensure continuous operation with an output of just 35 watts or automatic re-ignition. Xenon headlights provide significantly more light than halogen headlights and make driving at night, especially in poor weather conditions, safer and less tiring for the driver’s eyes.

cornering light.

The bi-xenon headlights with dynamic cornering light illuminate curves or the turning area up to 90% better. From a speed of approx. 15 km/h, the headlight cones follow the steering angle of the vehicle steering wheel with the help of small servomotors in the headlight units. The maximum swivel angle of the dynamic cornering light is 15 degrees. The steering movement of the headlight units is controlled, among other things, via the signals from the steering angle sensor. The improved visibility means that obstacles are recognized earlier and the driver gains additional reaction time. This significantly reduces the risk of accidents.

Parking sensors front and rear.

Park Distance Control is a parking aid that warns of the distance to obstacles at the front and rear. A repeated warning signal tells the driver how far the vehicle is from the obstacle. As the gap decreases, the frequency of the acoustic signal increases. It starts signaling when the vehicle is 1.60 meters away from the obstacle. When there is only 20 centimeters left to move, the warning tone becomes permanent. The system works with up to 12 ultrasonic sensors mounted in the front and rear bumpers. The sensors send and receive pulses in the 40,000 Hz range. When a pulse hits an obstacle, it is reflected. The sensor picks up the echo. The evaluation electronics use the time delay between the pulse and the echo to calculate the distance between the obstacle and the vehicle. To adapt to special traffic situations, such as stop-and-go traffic, the parking distance control can be switched off at the front. The rear ParkPilot is switched on automatically when reverse gear is engaged.

8 air bags.

Airbags, together with the seat belts, reduce the risk of serious head and chest injuries in collisions of a certain severity. If the crash sensors register an impact that exceeds the value required to trigger the airbags, the airbag controller ignites the gas generator. This inflates the airbags in the steering wheel and dashboard in front of the passenger within 30 to 40 milliseconds. When inflated, these airbags cushion the head and upper body and distribute the resulting loads over as large an area as possible. Only 120 milliseconds later, the gas escapes and the airbag bursts. Reducing head and neck movement helps reduce the risk of injury. A further development of the conventional system with two-stage deployment of the front airbags can be found, for example, in the Volkswagen Phaeton. The precisely defined deployment of the airbags in two stages, depending on the severity of the impact, is intended to reduce the stress on the driver and front passenger in the event of an accident. However, optimal protection can only be achieved if the occupants are properly belted, because the airbags and the belt tensioners together form a finely tuned safety system. In addition to the front airbags, side airbags and a head airbag system are also available.

ABS/ESP.

The anti-lock braking system prevents the wheels from locking when braking hard or when braking on a slippery road surface and ensures that the driver can still steer the vehicle. When the wheels lock, they can no longer transfer cornering forces, so the driver loses control of the vehicle. To prevent this, the ABS control unit uses wheel speed sensors to monitor the speed of all wheels on the vehicle. If a wheel threatens to lock, a solenoid valve in the central control unit of the anti-lock braking system reduces the brake pressure on the wheel in question until it turns freely again. The pressure is then increased again up to the bridging threshold. The vehicle remains stable and controllable. With the latest anti-lock braking systems, as installed in all Volkswagen models, this process is repeated several times per second. The driver recognizes the use of the anti-lock braking system from the slight pulsing of the brake pedal. Within the effective range of the anti-lock braking system, the vehicle can be steered without any problems, even when braking hard, and enables the driver to avoid collisions with any obstacles on the road. The Touareg’s “Offroad” ABS function is a special algorithm programmed in the ABS control unit, which is only automatically activated when driving in extreme terrain (vehicle has to drive at less than 5 km/h in the middle differential lock, for example). With off-road ABS, the wheels can briefly lock before the system reduces braking pressure. As a result, a small wedge of material from the ground (e.g. gravel or sand) can build up in front of the wheels, which then increases the braking effect. The Touareg remains steerable at all times, the braking distance is significantly shorter.

rain sensors.

The Volkswagen rain sensor automatically regulates the wiping intervals of the windscreen wipers according to the intensity of the rain. The sensor is housed in the base of the interior mirror. It consists of several infrared light-emitting diodes (LEDs) and a central photodiode. The light emitted by the LEDs is reflected by the windshield onto the photo sensor. The more water droplets there are on the windshield, the less light the sensor receives. This information is passed on to an electronic control unit, which adjusts the wiping intervals of the windscreen wipers accordingly. The sensitivity of the sensor can also be adjusted individually using a selector switch. The rain sensor is designed in such a way that small defects, dirt and aging of the windscreen do not impair its function. The advantages of the rain sensor are comfort and safety. The driver can fully concentrate on the road without having to worry about setting the wiper interval. This is a major plus in terms of safety, especially when visibility is suddenly impaired when overtaking a truck on a wet road.

Automatic headlamps.

The automatic headlight range control ensures optimal headlight adjustment and illumination of the road. The headlight range control ensures a constant headlight range regardless of the load in the vehicle and thus prevents oncoming traffic from being dazzled. The control function automatically adjusts the angle of inclination of the headlights to the current vehicle load. There are two different types of automatic headlamp leveling systems: static and dynamic systems. While the static systems can compensate for the additional weight of the passengers and their luggage, dynamic systems also correct the headlight setting when moving off, accelerating and braking. In static systems, the control unit processes the signals from the electronic speedometer and the ABS control unit, as well as the received inclination sensor signals. This allows the system to determine whether the vehicle is stationary or driving at a constant speed. The dynamic headlight range control from Volkswagen ensures correct headlight adjustment in all driving situations. The control unit is also able to distinguish the change in the speed signals produced by the vehicle’s acceleration and braking. Processing these additional signals requires a much more powerful control unit. The motorized actuator also adjusts at a higher speed, so that the headlight range can be adjusted in a few fractions of a second. Automatic headlight range control is required by law for vehicles with xenon headlights.

Anti-theft alarm with interior surveillance.

To protect against theft, more and more vehicles are being equipped with systems that are prepared and deactivated via a coded radio remote control and sound an alarm in the event of unauthorized access via contacts on the doors, engine compartment and luggage inside the vehicle or by ultrasonic motion sensors or power consumers in the vehicle interior. The ultrasound system also detects attempted vehicle entry through a broken window.

Audi adaptive cornering light

Adaptive light that allows the driver to foresee at night by illuminating corners and bends depending on the situation and intelligently swiveling in the headlights.

Headlights that adapt to your drive. See ahead in the dark by illuminating corners and curves more effectively. Adaptive light describes two technologies: cornering light, which shines around curves or corners, and dynamic cornering light, which rotates the headlights relative to the steering wheel. Both provide the driver with better visibility and ultimately a safer ride.