Archive for the ‘Headlights’ Category

Audi A8 super high-tech headlights

Tuesday, January 21st, 2014

Highly effective: new turn signal light in the Audi A8

-Indicator LEDs light up sequentially in the turning direction
-Advanced turn signal light is a component of the Audi Matrix LED headlight

In the new Audi A8, the turn signal light consists of lighting elements that illuminate in a defined sequence; this makes it easier for others to perceive the driver’s turning intentions, even under difficult conditions.

In the new Audi A8, the turn signal lights will now indicate the turning direction in an innovative way, which has the potential to significantly enhance traffic safety. That is because the lights provide a visual signal that can be clearly and quickly perceived, even at long distances and in poor visibility.

Each of the enhanced headlights contains18 light-emitting diodes arranged in a strip that is subdivided into seven blocks. Each tail light contains 24 LEDs in eight segments, which are used to dynamically indicate the turning direction. During flashing, the blocks are sequentially activated at 20 millisecond intervals, from the inside outwards in the desired turning direction. After 150 milliseconds, all segments are bright; for another 250 milliseconds they illuminate with full intensity. Afterwards, the turn signals go dark before repeating the lighting sequence.

Considering their capabilities, the Audi Matrix LED headlights can be regarded as a cutting-edge innovation. In each headlight, 25 light-emitting diodes generate a highly variable high-beam light. When the on-board camera detects other vehicles ahead, the Audi Matrix LED headlights mask the relevant sections of the high-beam by dimming or shutting off individual diodes. Very bright illumination is preserved in the remaining zones.

The Audi Matrix LED headlights also feature navigation-based cornering lights and, in cooperation with the night vision assistant, a marker light that warns the driver of pedestrians in the dark and which also alerts the pedestrians.

Audi will be presenting the upgraded A8 in September at the IAA International Motor Show in Frankfurt.

Source: Auto Blog

Intel Developing Headlights?

Friday, January 17th, 2014

When computer hardware companies start getting involved with the development of automotive technologies, you can be sure some futuristic stuff is about to go down. How does invisible rain sound to you? Intel, along with Carnegie Mellon University, has come up with an idea for a new headlight system that can make rain seem to disappear from the driver’s direct line of sight.

According to CNET, the headlight uses a camera housed within the headlight assembly to detect rain (and presumably snow or hail) as it falls, and then it uses a processor to anticipate the path of the rain. Finally, the actual light is created by a projector, which uses the information supplied by the processor to block out the pixels where the rain is expected to be. This technology, as you can see in the image above, should help improve visibility since there will be less light reflected back at the driver by raindrops.

For now, the only way you can see this rain-cancelling technology is in a demonstration in the video report posted below, but Intel thinks that it could make its way into production within the next 10 years.

Audi promises production laser headlights

Friday, January 17th, 2014

udi is showing off new laser headlight technology this week at the 2014 Consumer Electronics Show on its Audi Sport Quattro Laserlight Concept, and most intriguingly, the automaker has plans to use the long-range lighting on production vehicles. Audi CEO Rupert Stadler tells Automotive News that this type of headlights will be used on a future production vehicle, although he did not specify any timeframe.

On the concept vehicle, the headlights employ LED low beams, while the high beams use the laserlight technology. Audi says that these lights are not only very small (“a few microns in diameter”) they are also able to light the road for almost a third of a mile (1,640 feet), with three times the brightness of an LED highbeam, yet with pinpoint control. These lights have already been confirmed for use in motorsports on the 2014 Audi R18 e-tron Quattro LMP1 racecar, and the tech will eventually trickle down to road-going cars.

In addition to how long this trickle down will take, it’s doubtful we’ll see these lights in the US anytime soon. Audi is still working with the US Department of Transportation for approval of its LED Matrix Beam headlights, which are already sold in other markets, and the negotiations appear to be taking quite a bit of time. Automotive News also notes that the laser headlights earmarked as options on the 2015 BMW i8 will not be offered in the US, either.

NHTSA upgrades Corvette headlight investigation

Thursday, January 16th, 2014

It’s looking more and more likely that we’ll be seeing a recall of certain sixth-generation Corvettes, as the National Highway Traffic Safety Administration has upgraded its initial investigation to an engineering analysis, the final stage before the Feds can request a full-on recall. The problems, which we first reported on back in May, had to do with headlights that would randomly cut out for some 2005 to 2007 Chevrolet Corvette models. NHTSA has received 95 complaints from owners of random headlight failures, while The Detroit News states that there have also been four reports from owners of 2008 Vettes.

The issue, which affects 103,374 cars, is believed to be caused by a fuse block in the engine bay. Located in a high-heat area, it can short out when exposed to increased temperatures, leading to the headlight failure. It’s not entirely clear if the issues extend to the Corvette’s Z06 and ZR1 variants.

General Motors is cooperating with NHTSA throughout the investigation, a spokesperson told The News.

News Source: The Detroit News, Auto Blog

Dangerous Problems of Dim Headlights

Saturday, January 9th, 2010

This is an article I found on CSB3’s website at that discusses dim headlights.

by Ukee Washington

Is being on the road hard on the eyes? Hard to see what’s in front of you? CBS 3 Anchor Ukee Washington reports, maybe you’ve got a dangerous problem, dim headlights.

Before you even notice it, a clear headlight can become a foggy one.

“People are driving and you can only can see about ten-percent of the light capacity,” said Florida auto restorer Mike Patrick.

And the less you can see, the more likely you will have an accident.

It’s a potentially dangerous problem across the country — including in Philadelphia.

Mechanic Tom Flora showed us headlights at his repair shop in Center City. You can see how much more clear one looks than the other. And it doesn’t take much to cause the problem.

“This is a sealed unit,” said Flora. “Any time you get a crack in it that allows it to get moisture in it, the heat of the lens will cloud the lens over immediately.”

Another way it can fade — the sun. Most headlights today are plastic, not glass, and over years they can yellow. That’s what happened to Gene Borger’s 1988 Volvo. “I could barely see at night when I was driving,” said Borger.

And it can happen to any make and model.

The Alliance for Automobile Manufacturers told CBS 3, replacing a fogged headlight is “routine maintenance,” even if it costs $300 to $1000 a piece.

“I don’t anybody’s budget has $300 to put a headlight in today,” said Flora.

So are today’s headlights defective products? Florida attorney Ralph Patino is considering suing auto and headlight manufacturers. “In order to replace one of these headlights, it’s very, very expensive, and the manufacturers know it,” said Patino.

Florida auto restorer Patrick said, “I believe it’s getting worse because, I hate to say it, but I think a lot of the auto manufacturers are finding ways to cut costs to build their cars, keep more money in their pockets.”

His company markets a product to make a headlight brighter — far less than a replacement.

So how bright does your headlight have to be? It varies by state. Keep an eye on your headlights, so they can keep an eye out for you.

(© MMVI, CBS Broadcasting Inc. All Rights Reserved.)

Headlight Care

Saturday, January 9th, 2010

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.[12]

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.

The reflector, made out of vapourised 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.

Headlamp. (2010, January 9). In Wikipedia, The Free Encyclopedia. Retrieved 19:23, January 9, 2010, from

Headlight Lens Cleaners

Saturday, January 9th, 2010

Dirt buildup on headlamp lenses increases glare to other road users, even at levels too low to reduce seeing performance significantly for the driver. Therefore, headlamp lens cleaners are required by ECE Regulation 48 on vehicles equipped with low-beam headlamps using light sources that have a reference luminous flux of 2,000 lumens or more. This includes all HID headlamps and some high-power halogen units. Some cars have lens cleaners fitted as standard or available as optional equipment even where the headlamp specifications and/or prevailing technical regulations do not require them. North America, for example, does not use ECE 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 wiper blade or brush conceptually similar to those used on the windshield of the car, or a fixed or pop-up high-pressure sprayer which cleans the lenses with a spray of windshield washer fluid.

Headlamp. (2010, January 9). In Wikipedia, The Free Encyclopedia. Retrieved 19:23, January 9, 2010, from

Dynamic Headlight Beam Control

Saturday, January 9th, 2010

Headlamp levelling control

The 1948 Citroen 2CV was launched in France with a manual headlamp levelling system, controlled by the driver with knob through a mechanical rod linkage. In 1954, Cibié introduced an automatic headlamp levelling system linked to the vehicle’s suspension system to keep the headlamps correctly aimed regardless of vehicle load. The first vehicle to be so equipped was the Panhard Dyna Z. Beginning in the 1970s, Germany and some other European countries began requiring remote-control headlamp levelling systems that permit the driver to lower the lamps’ aim by means of a dashboard control lever or knob if the rear of the vehicle is weighted down with passengers or cargo, which would tend to raise the lamps’ aim angle and create glare. Such systems typically use stepper motors at the headlamp and a rotary switch on the dash marked “0″, “1″, “2″, “3″ for different beam heights, “0″ being the “normal” (and highest) position for when the car is lightly loaded. Internationalised ECE Regulation 48, in force in most of the world outside North America, currently requires such systems on all vehicles. The regulation stipulates a more stringent version of this antiglare measure for vehicles equipped with headlamp bulbs producing more than 2,000 lumens, such as xenon headlamps; such vehicles must be equipped with headlamp self-levelling systems that sense the vehicle’s degree of squat due to cargo load and road inclination, and automatically adjust the headlamps’ vertical aim to keep the beam correctly oriented without any action required by the driver.

Directional headlamps

1928 Willys-Knight 70A Touring. Notice the directional headlight in the middle.

Directional (steering) headlamps on a Citroën DS—the driver can see his way 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. Czech Tatra and 1920s Cadillacs were 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[44] with an elaborate dynamic headlamp positioning system that adjusted the headlamps’ horizontal and vertical positioning in response to inputs from the vehicle’s steering and suspension systems, though US regulations required this system to be removed from those models when sold in the USA.

Advanced front-lighting system (AFS)

There has been a recent 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 organisation, composed primarily of European automakers, lighting companies and regulators began working to develop design and performance specifications for what is known as advanced front-lighting systems, commonly AFS.[45] Manufacturers such as Toyota,[46] Škoda[47] and Vauxhall/Opel[48] 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.[49] The most advanced AFS systems use GPS signals to anticipate changes in road curvature, rather than simply reacting to them.[50]

Automatic beam switching

Main article: Automatic headlight dimmer

Even when the high beam is warranted by prevailing conditions, drivers generally do not use them.[51] 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. Early systems like Cadillac’s Autronic Eye appeared in 1952 with an electric eye atop the dashboard (later behind the radiator grill) which was supposed to switch between low and high beam in response to oncoming traffic. These systems could not accurately discern headlamps from non-vehicular light sources such as streetlights, they did not switch to low beam when the driver approached a vehicle from behind, and they spuriously switched to low beam in response to road sign reflections of the vehicle’s own headlamps. 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.

Intelligent Light System

Intelligent Light System is a headlamp beam control system introduced in 2006 which offers five different bi-xenon light functions,[52] each of which is suited to typical driving or weather conditions:

  • Country mode
  • Motorway mode
  • Enhanced fog lamps
  • Active light function
  • Cornering light function

Adaptive Highbeam

Main article: Adaptive Highbeam Assist

Adaptive Highbeam Assist is the newest headlamp technology, introduced in spring 2009 in the new generation Mercedes-Benz E-Class. It is based on camera mounted behind the windshield and automatically and continuously adapts the headlamp range to the distance of vehicles ahead or which are oncoming.

The same technology is also present in the BMW 7 series. BMW’s version of this technology, developed in cooperation with Mobileye, uses swiveling headlights that always point in the direction the vehicle is steering so therefore the road ahead is better illuminated and obstacles become visible sooner

Headlamp. (2010, January 9). In Wikipedia, The Free Encyclopedia. Retrieved 19:23, January 9, 2010, from

Headlight Sources

Saturday, January 9th, 2010

Tungsten light sources

The first electric headlamp light source was the tungsten filament, operating in a vacuum or inert-gas atmosphere inside the headlamp bulb or sealed beam. Compared to newer-technology light sources, tungsten filaments give off small amounts of light relative to the power they consume. Also, 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, though blackening was less of a problem in sealed beam units; their large interior surface area minimised the thickness of the tungsten accumulation. For these reasons, plain tungsten filaments are all but obsolete in automotive headlamp service.

Tungsten-halogen light sources

Halogen technology (also “quartz-halogen”, “quartz-iodine”, “iodine”, “iode”) makes tungsten filaments more efficacious producers of light — more lumens out per watt in — and Europeans chose to use this extra efficacy to provide drivers with more light than was available from nonhalogen filaments at the same power consumption. Unlike the European approach which emphasised increased light output, most U.S. low beam halogens were low current versions of their nonhalogen counterparts, producing the same amount of light with less power. A slight theoretical fuel economy benefit and reduced vehicle construction cost through reduced wire and switch ratings were the claimed benefits. There was an improvement in seeing distance with U.S. halogen high beams, which were permitted for the first time to produce 150,000 candelas (cd) per vehicle, double the nonhalogen limit of 75,000 cd but still well shy of the international European limit of 225,000 cd. After replaceable halogen bulbs were permitted in U.S. headlamps in 1983, development of U.S. bulbs continued to favour long bulb life and low power consumption, while European designs continued to prioritise optical precision and maximum output.

The first halogen bulb for vehicle use, the H1, was introduced in 1962 by a consortium of European bulb and headlamp makers. This bulb has a single axial filament that consumes 55 watts at 12.0 volts, and produces 1550 lumens ±15% when operated at 13.2 V. H2 (55 W @ 12.0 V, 1820 lm @ 13.2 V) followed in 1964, and the transverse-filament H3 (55 W @ 12.0 V, 1450 lm ±15%) in 1966. H1 still sees wide use in low beams, high beams and auxiliary foglamp and driving lamps, as does H3. The H2 does not see wide use any more because it requires an intricate bulb holder interface to the lamp, has a short life and is difficult to handle. For those reasons, H2 was withdrawn from ECE Regulation 37 for use in new lamp designs (though H2 bulbs are still manufactured for replacement purposes in existing lamps). The use of H1 and H3 bulbs was legalised in the United States in 1997. More recent single filament bulb designs include the H7 (55 W @ 12.0 V, 1500 lm ±10% @ 13.2 V), H8 (35 W @ 12.0 V, 800 lm ±15% @ 13.2 V), H9 (65 W @ 12.0 V, 2100 lm ±10% @ 13.2 V), and H11 (55 W @ 12.0 V, 1350 lm ±10% @ 13.2 V). 24-volt versions of many bulb types are available for use in trucks, buses, and other commercial and military vehicles.

The first dual-filament halogen bulb (to produce a low and a high beam with only one bulb), the H4, was released in 1971. The U.S. prohibited halogen headlamps until 1978, when halogen sealed beams were released. To this day, the H4 is still not legal for automotive use in the United States. Instead, the Americans created their own very similar standard (HB2/9003). The primary differences are that the HB2 sets more strict requirements on filament positioning, and that the HB2 are required to meet the lower maximum output standards set forth by the United States government.

The first U.S. halogen headlamp bulb, introduced in 1983, was the 9004/HB1. It is a 12.8-volt, transverse dual-filament 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 U.S. approved halogen bulbs include the 9005/HB3 (65 W, 12.8 V), 9006/HB4 (55 W, 12.8 V), and 9007/HB5 (65/55 watts, 12.8 V).

Halogen infrared reflective light sources (HIR)

A further development of the tungsten-halogen bulb has a dichroic coating that passes visible light and reflects infrared radiation. The glass in such a bulb is spherical, rather than tubular. The reflected infrared radiation strikes the filament located at the centre of the sphere, heating the filament to a degree greater than occurs by passing an electric current through the filament. The filament thus superheated emits more light, without an increase in power consumption or a decrease in lifespan.

HID (xenon) light sources

Xenon projector low beam headlamp illuminated on a Lincoln MKS.

HID stands for high-intensity discharge, a technical term for the electric arc that produces the light. The high intensity of the arc comes from metallic salts that are vapourised within the arc chamber. These lamps are formally known as gas-discharge burners, and produce more light for a given level of power consumption than ordinary tungsten and tungsten-halogen bulbs. Because of the increased amounts of light available from HID burners relative to halogen bulbs, HID headlamps producing a given beam pattern can be made smaller than halogen headlamps producing a comparable beam pattern. Alternatively, the larger size can be retained, in which case the xenon headlamp can produce a more robust beam pattern.

Automotive HID lamps are commonly called ‘xenon headlamps’, though they are actually metal halide lamps that contain xenon gas. The xenon gas allows the lamps to produce minimally adequate light immediately upon powerup, and accelerates the lamps’ run-up time. If argon were used instead, as is commonly done in street lights and other stationary metal halide lamp applications, it would take several minutes for the lamps to reach their full output. The light from HID headlamps has a distinct bluish tint when compared with tungsten-filament headlamps. [21]


Xenon headlamps were introduced in 1991 as an option on the BMW 7-series. This first system used an unshielded, non-replaceable burner designated D1 — a designation that would be recycled years later for a wholly different type of burner. The AC ballast was about the size of a building brick. The first American-made effort at HID headlamps was on the 1996-98 Lincoln Mark VIII, which used reflector headlamps with an unmasked, integral-ignitor burner made by Sylvania and designated Type 9500. This was the only system to operate on DC; reliability proved inferior to the AC systems. The Type 9500 system was not used on any other models, and was discontinued after Osram’s takeover of Sylvania. All HID headlamps worldwide presently use the standardised AC-operated bulbs and ballasts.

Burner and ballast operation

HID headlamp bulbs do not run on low-voltage DC current, so they require a ballast with either an internal or external ignitor. The ignitor is integrated into the bulb in D1 and D3 systems, and is either a separate unit or integral with the electronic ballast in D2 and D4 systems. The ballast controls the current to the bulb. The ignition and ballast operation proceeds in three stages:

  1. Ignition: a high voltage pulse is used to produce a spark — in a manner similar to a spark plug – which ionises the Xenon gas, creating a conducting tunnel between the tungsten electrodes. In this tunnel, the electrical resistance is reduced and current flows between the electrodes.
  2. Initial phase: the bulb is driven with controlled overload. Because the arc is operated at high power, the temperature in the capsule rises quickly. The metallic salts vapourise, and the arc is intensified and made spectrally more complete. The resistance between the electrodes also falls; the electronic ballast control gear registers this and automatically switches to continuous operation.
  3. Continuous operation: all metal salts are in the vapour phase, the arc has attained its stable shape, and the luminous efficacy has attained its nominal value. The ballast now supplies stable electrical power so the arc will not flicker.

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 higher.

Burner types

HID headlamp burners produce between 2,800 and 3,500 lumens from between 35 and 38 watts of electrical power, while halogen filament headlamp bulbs produce between 700 and 2,100 lumens from between 40 and 72 watts at 12.8 V.[22][23][24]

Current-production burner categories are D1S, D1R, D2S, D2R, D3S, D3R, D4S, and D4R. The D stands for discharge, and the number is the type designator. The final letter describes the outer shield. The arc within an HID headlamp bulb generates considerable short-wave ultraviolet (UV) light, but none of it escapes the bulb, for a UV-absorbing hard glass shield is incorporated around the bulb’s arc tube. This is important to prevent degradation of UV-sensitive components and materials in headlamps, such as polycarbonate lenses and reflector hardcoats. “S” burners — D1S, D2S, D3S, and D4S — have a plain glass shield and are primarily used in projector-type optics. “R” burners — D1R, D2R, D3R, and D4R — are designed for use in reflector-type headlamp optics. They have an opaque mask covering specific portions of the shield, which facilitates the optical creation of the light/dark boundary (cutoff) near the top of a low-beam light distribution. Automotive HID burners do emit considerable near-UV light, despite the shield.


The correlated colour temperature of HID headlamp bulbs, at between 4100K and 4400K, is often described in marketing literature as being closer to the 6500K of sunlight compared with tungsten-halogen bulbs at 3000K to 3550K. Nevertheless, HID headlamps’ light output is not similar to daylight. The spectral power distribution (SPD) of an automotive HID headlamp is discontinuous, while the SPD of a filament lamp, like that of the sun, is a continuous curve. Moreover, the colour rendering index (CRI) of tungsten-halogen headlamps (≥0.98) is much closer than that of HID headlamps (~0.75) to standardised sunlight (1.00). Studies have shown no significant safety effect of this degree of CRI variation in headlighting.[25][26][27][28]


Increased safety

The HID headlamp light sources (bulbs) offer substantially greater luminance and luminous flux than halogen bulbs — about 3000 lumens and 90 mcd/m2 versus 1400 lumens and 30 mcd/m2. If the higher-output HID light source is used in a well-engineered headlamp optic, the driver gets more usable light. Studies have demonstrated drivers react faster and more accurately to roadway obstacles with good HID headlamps rather than halogen ones.[29] Hence, good HID headlamps contribute to driving safety.[30] The contrary argument is that HID headlamps can negatively impact the vision of oncoming traffic due to their high intensity and “flashing” effect due to the rapid transition between low and high illumination in the field of illumination, thus increasing the risk of a head-on collision between the HID-enabled vehicle and a blinded oncoming driver.

Efficacy and output

HID burners give higher efficacy (produce more light from less power) than halogen bulbs. The highest-intensity halogen headlamp bulbs, H9 and HIR1, produce 2100 to 2530 lumens from approximately 70 watts at 13.2 volts. A D2S HID burner produces 3200 lumens from approximately 42 watts during stable operation.[22] The reduced power consumption means less fuel consumption, with resultant less CO2 emission per vehicle fitted with HID lighting (1.3 g/km assuming that 30% of engine running time is with the lights on).


The average service life of an HID lamp is 2000 hours, compared to between 450 and 1000 hours for a halogen lamp.[31]


Blind oncoming traffic

Due to their high intensity and unsual colour temperature, they can blind or enrage oncoming drivers, thus decreasing road safety and increasing the risk of head-on collisions.


Vehicles equipped with HID headlamps are required by ECE regulation 48 also to be equipped with headlamp lens cleaning systems and automatic beam levelling control. Both of these measures are intended to reduce the tendency for high-output headlamps to cause high levels of glare to other road users. In North America, ECE R48 does not apply and while lens cleaners and beam levellers are permitted, they are not required;[32] HID headlamps are markedly less prevalent in the US, where they have produced significant glare complaints.[33] Scientific study of headlamp glare has shown that for any given intensity level, the light from HID headlamps is 40% more glaring than the light from tungsten-halogen headlamps.[34]

Mercury content

HID headlamp bulb types D1R, D1S, D2R, D2S and 9500 contain the toxic heavy metal mercury. The disposal of mercury-containing vehicle parts is increasingly regulated throughout the world, for example under US EPA regulations. Newer HID bulb designs D3R, D3S, D4R, and D4S which are in production since 2004 contain no mercury,[35][36] but are not electrically or physically compatible with headlamps designed for previous bulb types.

Lack of backward-compatibility

The arc light source in an HID headlamp is fundamentally different in size, shape, orientation, and luminosity distribution compared to the filament light source used in tungsten-halogen headlamps. For that reason, HID-specific optics are used to collect and distribute the light. HID burners cannot effectively or safely be installed in optics designed to take filament bulbs; doing so results in improperly-focused beam patterns and excessive glare, and is therefore illegal in almost all countries.[37]


HID headlamps are significantly more costly to produce, install, purchase, and repair. The extra cost of the HID lights may exceed the fuel cost savings through their reduced power consumption, though some of this cost disadvantage is offset by the longer lifespan of the HID burner relative to halogen bulbs.

LED light sources

The first series-production LED headlamps on the Lexus LS 600h

Automotive headlamp applications using light-emitting diodes (LEDs) have been undergoing very active development since 2004.[38][39] The first series-production LED headlamps were factory-installed on the Lexus LS 600h / LS 600h L starting with the 2008 models. Low beam, front position light and sidemarker functions are performed by LEDs; high beam and turn signal functions use filament bulbs. The headlamp is supplied by Koito. Full-LED headlamps supplied by AL-Automotive Lighting were fitted on the 2008 V10 Audi R8 sports car except in North America. The Hella headlamps on the 2009 Cadillac Escalade Platinum became the first U.S. market all-LED headlamps. Present designs give performance between halogen and HID headlamps,[40] with system power consumption slightly lower than other headlamps, longer lifespans and more flexible design possibilities.[41][42] As LED technology continues to evolve, the performance of LED headlamps is predicted to improve to approach, meet, and perhaps one day surpass that of HID headlamps.[43]

The limiting factors with LED headlamps presently include high system expense, regulatory delays and uncertainty, and logistical issues created by LED operating characteristics. LEDs are commonly considered to be low-heat devices due to the public’s familiarity with small, low-output LEDs used for electronic control panels and other applications requiring only modest amounts of light. However, LEDs actually produce a significant amount of heat per unit of light output. Rather than being emitted together with the light as is the case with conventional light sources, an LED’s heat is produced at the rear of the emitters. The cumulative heat of numerous high-output LEDs operating for prolonged periods poses thermal-management challenges for plastic headlamp housings.

Prolonged operation above the maximum junction temperature will permanently degrade the LEDs and ultimately shorten the device’s life. The need to keep LED junction temperatures low at high power levels always requires additional thermal management measures such as heatsinks and exhaust fans which are typically quite expensive[citation needed].

Additional facets of the thermal issues with LED headlamps reveal themselves in cold ambient temperatures. Not only must heat be removed from the rear of the headlamp so that the housing does not deform or melt, but heat must in addition be effectively applied to thaw snow and ice from the front lenses, which are not heated by the comparatively small amount of infrared radiation emitted forward with the light from LEDs[citation needed].

LEDs are increasingly being adopted for signal functions such as parking lamps, brake lamps and turn signals as well as daytime running lamps, as in those applications they offer significant advantages over filament bulbs with fewer engineering challenges than headlamps pose.

Headlamp. (2010, January 9). In Wikipedia, The Free Encyclopedia. Retrieved 19:23, January 9, 2010, from

Headlight Optical systems

Friday, January 8th, 2010

Reflector lamps

Lens optics

Lens optics, side view. Light is dispersed vertically (shown) and laterally (not shown).

A 7 in. round sealed-beam headlamp with lens optics on a Jaguar E-type. The flutes and prisms spread and distribute the light collected by the reflector.

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 prism optics moulded into the headlamp lens then shift parts of the light laterally and vertically to provide the required light distribution pattern. The lens may use both refraction and TIR to achieve the desired results. Most sealed-beam headlamps have lens optics.[13]

Reflector optics

Reflector optics, side view

A reflector-optic headlamp on a Jeep Liberty. The clear front cover lens serves only a protective function.

Starting in the 1980s, headlamp reflectors began to evolve beyond the simple stamped steel parabola. The 1983 Austin Maestro the first vehicle equipped with Lucas-Carello’s homofocal reflectors, which comprised parabolic sections of different focal length to improve the efficiency of light collection and distribution.[14] CAD technology allowed the development of reflector headlamps with nonparabolic, complex-shape reflectors. First commercialised by Valeo under their Cibié brand, these headlamps would revolutionise automobile design.[15]

The 1987 U.S.-market Dodge Monaco/Eagle Premier twins and European Citroën XM were the first cars with complex-reflector headlamps[16] with faceted optic lenses. General Motors‘ Guide Lamp division in America had experimented with clear-lens complex-reflector lamps in the early 1970s and achieved promising results,[17] but the U.S.-market 1990 Honda Accord was first with clear-lens multi-reflector headlamps; these were developed by Stanley in Japan.[18] The optics to distribute the light in the desired pattern are designed into the reflector itself, rather than into the lens. Depending on the development tools and techniques in use, the reflector may be engineered from the start as a bespoke shape, or it may start as a parabola standing in for the size and shape of the completed package. In the latter case, the entire surface area is modified so as to produce individual segments of specifically calculated, complex contours. The shape of each segment is designed such that their cumulative effect produces the required light distribution pattern.[13]

Modern reflectors are commonly made of compression-moulded or injection molded plastic, though glass and metal optic reflectors also exist. The reflective surface is vapour deposited aluminum with a clear overcoating to prevent the extremely thin aluminum from oxidizing. Extremely tight tolerances must be maintained in the design and production of complex-reflector headlamps.

Dual-beam reflector headlamps

Night driving is difficult and dangerous due to the blinding glare of headlights from oncoming traffic. Headlamps that satisfactorily illuminate the road ahead without causing glare have long been sought. The first solutions involved resistance-type dimming circuits, which decreased the intensity of the headlamps. This yielded to tilting reflectors, and later to dual-filament bulbs with a high and a low beam.

In a two-filament headlamp, there can only be one filament exactly at the focal point of the reflector. There are two primary means of producing two different beams from a two-filament bulb in a single reflector.

American system

One filament is located at the focal point of the reflector. The other filament is shifted axially and radially away from the focal point. In most 2-filament sealed beams and in 2-filament replaceable bulbs type 9004, 9007 and H13, the high beam filament is at the focal point and the low beam filament is off focus. For use in right-traffic countries, the low beam filament is positioned slightly upward, forward and leftward of the focal point, so that when it is energised, the light beam is widened and shifted slightly downward and rightward of the headlamp’s axis. Transverse-filament bulbs such as 9004 can only be used with the filaments horizontal, but axial-filament bulbs can be rotated or “clocked” by the headlamp designer so as to optimise the beam pattern or to effect the traffic-handedness of the low beam. The latter is accomplished by clocking the low-beam filament in an upward-forward-leftward position to produce a right-traffic low beam, or in an upward-forward-rightward position to produce a left-traffic low beam.

The opposite tactic has also been employed in certain 2-filament sealed beams. Placing the low beam filament at the focal point to maximise light collection by the reflector, and positioning the high beam filament slightly rearward-rightward-downward of the focal point. The relative directional shift between the two beams is the same with either technique—in a right-traffic country, the low beam is slightly downward-rightward and the high beam is slightly upward-leftward, relative to one another—but the lens optics must be matched to the filament placements selected.

European system

The traditional European method of achieving low and high beam from a single bulb involves two filaments along the axis of the reflector. The high beam filament is on the focal point, while the low beam filament is approximately 1 cm forward of the focal point and 3 mm above the axis. Below the low beam filament is a cup-shaped shield (called a “Graves Shield“) spanning an arc of 165°. When the low beam filament is illuminated, this shield casts a shadow on the corresponding lower area of the reflector, blocking downward light rays that would otherwise strike the reflector and be cast above the horizon. The bulb is rotated (or “clocked”) within the headlamp to position the Graves Shield so as to allow light to strike a 15° wedge of the lower half of the reflector. This is used to create the upsweep or upstep characteristic of ECE low beam light distributions. The bulb’s rotative position within the reflector depends on the type of beam pattern to be produced and the traffic directionality of the market for which the headlamp is intended.

This system was first used with the tungsten incandescent Bilux/Duplo R2 bulb of 1954, and later with the halogen H4 bulb of 1971. In 1992, U.S. regulations were amended to permit the use of H4 bulbs redesignated HB2 and 9003, and with slightly different production tolerances stipulated. These are physically and electrically interchangeable with H4 bulbs.[19] Similar optical techniques are used, but with different reflector and/or lens optics to create a US beam pattern rather than a European one.

Each system has its advantages and disadvantages. The American system historically permitted a greater overall amount of light within the low beam, since the entire reflector and lens area is used, but at the same time, the American system has traditionally offered much less control over upward light that causes glare, and for that reason has been largely rejected outside the US. In addition, the American system makes it difficult to create markedly different low and high beam light distributions. The high beam is usually a rough copy of the low beam, shifted slightly upward and leftward. The European system traditionally produced low beams containing less overall light, because only 60% of the reflector’s surface area is used to create the low beam. However, low beam focus and glare control are easier to achieve. In addition, the lower 40% of the reflector and lens are reserved for high beam formation, which facilitates the optimisation of both low and high beams.

Recent developments

Complex-reflector technology in combination with new bulb designs such as H13 is enabling the creation of European-type low and high beam patterns without the use of a Graves Shield, while the 1992 US approval of the H4 bulb has made traditionally European 60% / 40% optical area divisions for low and high beam common in the US. Therefore, the difference in active optical area and overall beam light content no longer necessarily exists between US and ECE beams. Dual-beam HID headlamps employing reflector technology have been made using adaptations of both techniques.

Projector (polyellipsoidal) lamps

Projector optics, side view

Projector headlamps on an Acura RL

In this system a filament is located at one focus of an ellipsoidal reflector and has a condenser lens at the front of the lamp. A shade is located at the image plane, between the reflector and lens, and the projection of the top edge of this shade provides the low-beam cutoff. The shape of the shade edge, and its exact position in the optical system, determines the shape and sharpness of the cutoff.[13] The shade may have a solenoid actuated pivot to provide both low and high beam — the shade is removed from the light path to create high beam, and placed in the light path to create low beam, and such optics are known as BiXenon or BiHalogen projectors, depending on the light source used. If there is no such arrangement, the cutoff shade is fixed in the light path, in which case separate high-beam lamps are required. The condenser lens may have slight fresnel rings or other surface treatments to reduce cutoff sharpness. Recent condenser lenses incorporate optical features specifically designed to direct some light upward towards the locations of retroreflective overhead road signs.

Hella introduced ellipsoidal optics for acetylene headlamps in 1911, but following the electrification of vehicle lighting, this optical technique wasn’t used for many decades. The first modern polyellipsoidal (projector) automotive lamp was the Super-Lite, an auxiliary headlamp produced in a joint venture between Chrysler Corporation and Sylvania and optionally installed in 1969 and 1970 full-size Dodge automobiles. It used an 85 watt transverse-filament tungsten-halogen bulb and was intended as a mid-beam, to extend the reach of the low beams during turnpike travel when low beams alone were inadequate but high beams would produce excessive glare.[20]

Projector main headlamps first appeared in 1981 on the Audi Quartz, the Quattro-based concept car designed by Pininfarina for Geneva Auto Salon.[citation needed] Developed more or less simultaneously in Germany by Hella and Bosch and in France by Cibié, the projector low beam permitted accurate beam focus and a much smaller-diameter optical package, though a much deeper one, for any given beam output. The version of the 1986 BMW 7 Series sold outside North America was the first volume-production auto to use polyellipsoidal low beam headlamps.

Headlamps using projector optics cause much worse dazzle to oncoming traffic than those using reflectors for the same light output. Dazzle from the headlights of a distant oncoming vehicle is caused by the extreme contrast between the intense spot of light and the darkness of the background. Projector optics emit the light through a much smaller area than reflector optics do; therefore, for the same total light output, the light spot of a projector headlamp is much more intense and more dazzling than the larger, dimmer light spot of a reflector lamp.

It is sometimes argued that the more tightly controlled beam pattern of projector optics reduces dazzle. In fact the beam pattern is irrelevant, since unless the headlamps are misaligned, an oncoming vehicle is sufficiently far off the beam axis as to be completely outside the beam in both reflector and projector cases. The dazzle is caused by the off-axis emission arising from such factors as scattering from optical imperfections in the lamp surface, and is worse where the more concentrated output of projector optics causes that emission to be more intense.

Headlamp. (2010, January 6). In Wikipedia, The Free Encyclopedia. Retrieved 21:49, January 7, 2010, from