Editing Headlamp (section)

== Light sources ==
{{Main|List of automotive light bulb types}}

=== Tungsten ===
The first electric headlamp light source was the [[tungsten]] [[Electrical filament|filament]], operating in a [[vacuum]] or inert-gas atmosphere inside the headlamp [[Incandescent light bulb|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 the 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 minimized the thickness of the tungsten accumulation. For these reasons, plain tungsten filaments are all but obsolete in automotive headlamp service.

=== Tungsten-halogen ===
[[Halogen lamp|Tungsten-halogen]] technology (also called "quartz-halogen", "quartz-iodine", "iodine cycle", etc.) increases the effective luminous [[efficacy]] of a [[tungsten]] filament: when operating at a higher filament temperature which results in more [[lumen (unit)|lumens]] output per watt input, a tungsten-halogen lamp has a much longer brightness lifetime than similar filaments operating without the halogen regeneration cycle. At equal luminosity, the halogen-cycle bulbs also have longer lifetimes. European-designed halogen headlamp light sources are generally configured to provide more light at the same power consumption as their lower-output plain tungsten counterparts. By contrast, many US-based designs are configured to reduce or minimize the power consumption while keeping light output above the legal minimum requirements; some US tungsten-halogen headlamp light sources produce less initial light than their non-halogen counterparts.<ref name="Dayton1">{{cite web |url=http://www.regulations.gov/search/Regs/contentStreamer?objectId=09000064802d582a&disposition=attachment&contentType=pdf |archive-url=https://web.archive.org/web/20210308151704/https://www.regulations.gov/search/Regs/contentStreamer?objectId=09000064802d582a&disposition=attachment&contentType=pdf |url-status=dead |archive-date=8 March 2021 |title=Dayton, David: Comments regarding NHTSA docket 8885, p. 5 |access-date=2010-12-29 }}</ref> A slight theoretical fuel economy benefit and reduced vehicle construction cost through lower wire and switch ratings were the claimed benefits when American industry first chose how to implement tungsten-halogen technology. There was an improvement in seeing distance with US halogen high beams, which were permitted for the first time to produce 150,000 [[candela]] (cd) per vehicle, double the non-halogen limit of 75,000&nbsp;cd but still well shy of the international European limit of 225,000&nbsp;cd. After replaceable halogen bulbs were permitted in US headlamps in 1983, the development of US bulbs continued to favor long bulb life and low power consumption, while European designs continued to prioritise optical precision and maximum output.<ref name=Dayton1/>

The [[H1 lamp]] was the first tungsten-halogen headlamp light source. It was introduced in 1962 by a consortium of European bulb and headlamp makers. This bulb has a single [[axis of rotation|axial]] filament that consumes 55 watts at 12.0 [[volt]]s, and produces 1550 lumens ±15% when operated at 13.2&nbsp;V. H2 (55&nbsp;W @ 12.0&nbsp;V, 1820&nbsp;lm @ 13.2&nbsp;V) followed in 1964, and the transverse-filament H3 (55&nbsp;W @ 12.0&nbsp;V, 1450&nbsp;lm ±15%) in 1966. H1 still sees wide use in low beams, high beams and auxiliary [[fog lamp|fog]] and [[driving lamp]]s, as does H3. The H2 is no longer a current type, since 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<ref>{{cite web|url=https://groups.google.com/group/rec.autos.driving/msg/de2d7f2f888fb298?hl=en& |title=Driving lights-was Re: headlight laws was re improving lightoutput - rec.autos.driving &#124; Google Groups |date=2003-12-06 |access-date=2012-01-31}}</ref> from [[World Forum for Harmonization of Vehicle Regulations|ECE Regulation 37]] for use in new lamp designs (though H2 bulbs are still manufactured for replacement purposes in existing lamps), but H1 and H3 remain current and these two bulbs were legalised in the United States in 1993.<ref name="NHTSA_8885">{{Cite web|url=https://www.regulations.gov/|title=Regulations.gov|website=www.regulations.gov}}</ref> More recent single-filament bulb designs include the H7 (55&nbsp;W @ 12.0&nbsp;V, 1500&nbsp;lm ±10% @ 13.2&nbsp;V), H8 (35&nbsp;W @ 12.0&nbsp;V, 800&nbsp;lm ±15% @ 13.2&nbsp;V), H9 (65&nbsp;W @ 12.0&nbsp;V, 2100&nbsp;lm ±10% @ 13.2&nbsp;V), and H11 (55&nbsp;W @ 12.0&nbsp;V, 1350&nbsp;lm ±10% @ 13.2&nbsp;V).<ref name=R37/> 24-volt versions of many bulb types are available for use in trucks, buses, and other commercial and military vehicles.
[[File:H4 IMG 1269.JPG|thumb|H4 bulb ([[Metre|cm]])]]
[[File:H7 IMG 1246.JPG|thumb|H7 bulb]]
The first dual-filament halogen bulb to produce both a low and a high beam, the H4 (60/55&nbsp;W @ 12&nbsp;V, 1650/1000&nbsp;lm ±15% @ 13.2&nbsp;V),<ref name=R37/> was released in 1971<ref name=100Hella/> and quickly became the predominant headlamp bulb throughout the world except in the United States, where the H4 is still not legal for automotive use. In 1989, the Americans created their own standard for a bulb called HB2: almost identical to H4 except with more stringent constraints on filament geometry and positional variance,<ref>{{Cite web|url=http://candlepowerinc.com/pdfs/H4_9003.pdf|title=H4, HB2, and 9003 bulbs}}</ref><ref>{{Cite book|title=Automotive Design Engineering|last=International|first=Grosvenor Press|year=1990|publisher=Century Press|pages=264}}</ref> and power consumption and light output expressed at the US test voltage of 12.8V.<ref>{{Cite web|url=https://www.regulations.gov/document/NHTSA-1998-3397-0011|title=Regulations.gov|website=www.regulations.gov}}</ref>

The first US halogen headlamp bulb, introduced in 1983, was the HB1/9004. 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 US approved [[halogen]] bulbs include the HB3 (65&nbsp;W, 12.8&nbsp;V), HB4 (55&nbsp;W, 12.8&nbsp;V), and HB5 (65/55 watts, 12.8&nbsp;V).<ref name="Docket3397">{{Cite web|url=https://www.regulations.gov/docketBrowser/NHTSA-1998-3397|title=Regulations.gov|website=www.regulations.gov}}</ref> All of the European-designed and internationally approved bulbs except H4 are presently approved for use in headlamps complying with US requirements.

==== Halogen infrared reflective (HIR) ====
A further development of the tungsten-halogen bulb has a [[dichroism|dichroic]] coating that passes [[visible spectrum|visible light]] and reflects [[Infrared#Heat|infrared radiation]]. The glass in such a bulb may be [[sphere|spherical]] or tubular. The reflected infrared radiation strikes the filament located at the center of the glass envelope, heating the filament to a greater degree than can be achieved through [[resistive heating]] alone. The superheated filament emits more light without an increase in power consumption.<ref>{{cite web |last1=Group |first1=Techbriefs Media |title=The Rebirth of the Incandescent Light Bulb |url= https://www.techbriefs.com/component/content/article/lighting-technology/lighting-technology/15641 |website=techbriefs.com |date=31 December 2012 |access-date=6 February 2019 }}</ref>

=== {{Anchor|High-intensity discharge|HID|Xenon}} High-intensity discharge (HID) ===
{{unreferenced section|date=November 2012}}
[[File:Lincoln xenon headlamp.jpg|thumb|right|HID projector low beam headlamp illuminated on a [[Lincoln MKS]]]]

[[High-intensity discharge lamp]]s (HID) produce light with an [[electric arc]] rather than a glowing filament. The high intensity of the arc comes from metallic salts that are vaporized within the arc chamber. These lamps have a higher efficacy than tungsten lamps. Because of the increased amounts of light available from HID lamps 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 HID headlamp can produce a more robust beam pattern.{{original research inline|date=November 2012}}

Automotive HID may be generically called "xenon headlamps", though they are actually [[metal-halide lamp]]s that contain [[xenon]] gas. The xenon gas allows the lamps to produce minimally adequate light immediately upon start, and shortens the run-up time. The usage of [[argon]], as is commonly done in street lights and other stationary metal-halide lamp applications, causes lamps to take several minutes to reach their full output.

The light from HID headlamps can exhibit a distinct bluish tint when compared with tungsten-filament headlamps.

==== Retrofitment ====
When a halogen headlamp is retrofitted with an HID bulb, light distribution and output are altered.<ref name="NHTSAR">{{cite web|url= http://www.nhtsa.gov/cars/rules/rulings/glare.html|title= Glare from Headlamps and other Front Mounted Lamps Federal Motor Vehicle Safety Standard No. 108; Lamps, Reflective Devices, and Associated Equipment|access-date= 4 November 2012|archive-date= 27 September 2011|archive-url= https://web.archive.org/web/20110927155258/http://www.nhtsa.gov/cars/rules/rulings/glare.html|url-status= dead}}</ref> In the United States, vehicle lighting that does not conform to FMVSS 108 is not street legal.<ref name="NHTSAR"/> Glare will be produced and the headlamp's type approval or certification becomes invalid with the altered light distribution, so the headlamp is no longer street-legal in some locales.<ref name="hella">{{cite web |url=http://dsl.torque.net/images/techdocs/Hella_No_Retrofit.jpg |title=Be Careful: Dangerous Products! HID kits and the law |publisher=Hella |access-date=29 May 2014 |url-status=dead |archive-url=https://web.archive.org/web/20110514023838/http://dsl.torque.net/images/techdocs/Hella_No_Retrofit.jpg |archive-date=14 May 2011 }}</ref> In the US, suppliers, importers and vendors that offer non-compliant kits are subject to civil fines. By October 2004, the [[National Highway Traffic Safety Administration|NHTSA]] had investigated 24 suppliers and all resulted in termination of sale or recalls.<ref>{{cite web |url=http://www.nhtsa.gov/About+NHTSA/Press+Releases/2004/ci.NHTSA+Illegal+Lighting+Crackdown+Continues.print |title=Nhtsa Illegal Lighting Crackdown Continues |website=Nhtsa.gov |date=19 October 2004 |access-date=29 May 2014 |archive-date=29 May 2014 |archive-url=https://web.archive.org/web/20140529232440/http://www.nhtsa.gov/About+NHTSA/Press+Releases/2004/ci.NHTSA+Illegal+Lighting+Crackdown+Continues.print |url-status=dead }}</ref>

In Europe and the many non-European countries applying [[United Nations Economic Commission for Europe#Inland Transport Committee|ECE]] Regulations, even HID headlamps designed as such must be equipped with lens cleaning and automatic self-leveling systems, except on motorcycles.<ref name="hella"/> These systems are usually absent on vehicles not originally equipped with HID lamps.

==== History ====
In 1992 the first production low beam HID headlamps were manufactured by [[Hella (company)|Hella]] and [[Robert Bosch GmbH|Bosch]] beginning in 1992 for optional availability on the [[BMW 7 Series (E32)|BMW 7 Series]].<ref name="100Hella">{{cite book |last1=Behrend |first1=Jürgen |title=Hella 1899-1999 |page=97}}</ref><ref name="Litronic">{{cite journal |title=Litronic – New Automotive Headlamp Technology with Gas Discharge lamp |journal=Automotive Design Engineering |year=1993 |last1=Neumann |first1=Rainer |last2=Woerner |first2=B. |pages=152–156}}</ref> This first system uses a built-in, non-replaceable bulb without a UV-blocking glass shield or touch-sensitive electrical safety cutout, designated D1<ref>{{cite report |chapter=Improved Projector Headlamps Using HID (Litronic) and Incandescent Bulbs |publisher=SAE International |year=1994 |last=Neumann |first=Rainer |title=SAE Technical Paper Series |volume=1 |chapter-url=http://papers.sae.org/940636/ |access-date=2014-12-13 |doi=10.4271/940636}}</ref> – a designation that would be recycled years later for a wholly different type of lamp. The AC ballast is about the size of a building brick.
In 1996 the first American-made effort at HID headlamps was on the 1996–98 [[Lincoln Mark VIII]], which uses reflector headlamps with an unmasked, integral-ignitor lamp made by [[Osram Sylvania|Sylvania]] and designated ''Type 9500''. This was the only system to operate on [[Direct current|DC]], since reliability proved inferior to the AC systems.{{citation needed|date=November 2012}} The Type 9500 system was not used on any other models, and was discontinued after [[Osram]]'s takeover of Sylvania in 1997.{{Citation needed|date=April 2012}} All HID headlamps worldwide presently use the standardized AC-operated bulbs and ballasts.
In 1999 the first worldwide HID headlights for both low and high beam were introduced on the [[Mercedes-Benz CL-Class (C215)]].<ref>http://media.daimler.com/dcmedia/0-921-614233-1-820664-1-0-0-0-0-1-11702-854934-0-1-0-0-0-0-0.html {{Webarchive|url=https://archive.today/20141230100212/http://media.daimler.com/dcmedia/0-921-614233-1-820664-1-0-0-0-0-1-11702-854934-0-1-0-0-0-0-0.html |date=30 December 2014 }} The history of the headlamp: From the candle lamp to motorway mode</ref><ref>{{Cite web|url=https://www.carsome.my/news/item/piercing-the-dark-mercedes-benzs-vehicle-lightings-have-come-a-long-way-part-1-of-2|title=Piercing the dark: Mercedes-Benz's vehicle lightings have come a long way – Part 1 of 2|access-date=28 November 2023|website=carsome.my|date=23 January 2020 }}</ref>

==== Operation ====
HID headlamp bulbs do not run on low-voltage DC current, so they require a [[ballast (electrical)|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 part of the ballast in D2 and D4 systems. The ballast controls the current to the bulb. The ignition and ballast operation proceeds in three stages:
# Ignition: a [[high voltage]] pulse is used to produce an [[electrical arc]] – in a manner similar to a [[spark plug]] – which ionizes the xenon gas, creating a conducting channel between the tungsten electrodes. Electrical resistance is reduced within the channel, and current flows between the electrodes.
# 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 vaporize, and the arc is intensified and made [[spectral power distribution|spectrally]] more complete. The resistance between the electrodes also falls; the electronic ballast control gear registers this and automatically switches to continuous operation.
# Continuous operation: all metal salts are in the vapor 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 [[volt]]s [[alternating current|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.
[[File:High Beam Indicator.svg|alt=high beam indicator example|thumb|Headlight indicator example]]
The command is often near the steering wheel and a specific indicator is shown on the dashboard.

==== Bulb types ====
[[File:2014 Toyota Avalon Quadrabeam Headlamp.jpg|thumb|2014 [[Toyota Avalon]] headlamp with "Quadrabeam"-styled HID low beams, halogen high beams, and [[Light-emitting diode|LED]] [[daytime running light]]s that also illuminate at a lower intensity to provide the [[Automotive lighting#Front position lights|front position light]] function]]

HID headlamps 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&nbsp;V.<ref name=R37>{{cite web|url= http://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/R037r7e.pdf |title=ECE Regulation 37 for motor vehicle filament bulbs }}&nbsp;{{small|(1.78&nbsp;MB)}}</ref><ref>{{cite web|url= https://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/2015/R099r3e.pdf |title=ECE Regulation 99 for motor vehicle HID bulbs }}&nbsp;{{small|(268&nbsp;KB)}}</ref><ref>{{cite web|url=http://fmvss108.tripod.com/light_source_list.htm |title=49CFR564 Replaceable Bulb Headlamp Light Source List |website=Fmvss108.tripod.com |access-date=2010-12-29}}</ref>

Current-production bulb 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" lamps – D1S, D2S, D3S, and D4S – have a plain glass shield and are primarily used in projector-type optics. "R" lamps – 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 lamps emit considerable near-UV light, despite the shield.

[[File:2014 Toyota Corolla LED Headlight.jpg|thumb|2014 [[Toyota Corolla]] The low beam features LED lighting, halogen high beams, and [[Light-emitting diode|LED]] [[daytime running light]]s that also illuminate at a lower intensity to provide the [[Automotive lighting#Front position lights|front position light]] function]]

==== Color ====
The [[correlated color temperature]] of factory installed automotive HID headlamps is between 4200K while tungsten-halogen lamps are at 3000K to 3550K. The [[spectral density#Applications|spectral power distribution]] (SPD) of an automotive HID headlamp is discontinuous and spikey while the SPD of a filament lamp, like that of the sun, is a continuous curve. Moreover, the [[color rendering index]] (CRI) of tungsten-halogen headlamps (98) is much closer than that of HID headlamps (~75) to standardized sunlight (100). Studies have shown no significant safety effect of this degree of CRI variation in headlighting.<ref>{{cite journal|title=Mercury-free HID headlamps: glare and color rendering|journal=University of Michigan Transportation Research Institute|year=2006 |first1=M. |last1=Sivak |first2=Michael J. |last2=Flannagan |first3=B. |last3=Schoettle |url= http://deepblue.lib.umich.edu/bitstream/2027.42/55201/1/UMTRI-2004-37.pdf|access-date=2009-08-03 }}</ref><ref>{{cite journal |title=Ranges of stop sign chromaticity under tungsten-halogen and high-intensity discharge illumination |journal=University of Michigan Transportation Research Institute |year=1992 |first1=Michael J. |last1=Flannagan |first2=Juha |last2=Luoma |first3=A.W. |last3=Gellatly |first4=M. |last4=Sivak |url=http://mirlyn-classic.lib.umich.edu/F/?func=direct&doc_number=005511681&local_base=UMTRI_PUB |access-date=2009-08-03 |archive-date=19 October 2015 |archive-url=https://web.archive.org/web/20151019013407/http://mirlyn-classic.lib.umich.edu/F/?func=direct&doc_number=005511681&local_base=UMTRI_PUB |url-status=dead }}</ref><ref>{{cite journal |title=Colors of retroreflective traffic sign materials when illuminated by high-intensity-discharge headlights |journal=University of Michigan Transportation Research Institute |year=1989 |first1=Michael J. |last1=Flannagan |first2=M. |last2=Sivak |url=http://mirlyn-classic.lib.umich.edu/F/?func=direct&doc_number=005505889&local_base=UMTRI_PUB |access-date=2009-08-03 |archive-date=19 October 2015 |archive-url=https://web.archive.org/web/20151019013407/http://mirlyn-classic.lib.umich.edu/F/?func=direct&doc_number=005505889&local_base=UMTRI_PUB |url-status=dead }}</ref><ref>{{cite journal |title=In-traffic evaluations of high-intensity discharge headlamps: overall performance and color appearance of objects |journal=University of Michigan Transportation Research Institute |year=1993 |first1=M. |last1=Sivak |first2=T. |last2=Sato |first3=D.S. |last3=Battle |first4=E.C. |last4=Traube |first5=Michael J. |last5=Flannagan |url=http://mirlyn-classic.lib.umich.edu/F/?func=direct&doc_number=005512803&local_base=UMTRI_PUB |access-date=2009-08-03 |archive-date=19 October 2015 |archive-url=https://web.archive.org/web/20151019013407/http://mirlyn-classic.lib.umich.edu/F/?func=direct&doc_number=005512803&local_base=UMTRI_PUB |url-status=dead }}</ref>

==== Advantages ====

===== Increased safety =====
Automotive HID lamps offer about 3000 [[lumen (unit)|lumen]]s and 90 [[Candela|Mcd]]/m<sup>2</sup> versus 1400 lumens and 30 Mcd/m<sup>2</sup>{{disputed inline|date=November 2012}} offered by halogen lamps. In a headlamp optic designed for use with an HID lamp, it produces more usable light. Studies have demonstrated drivers react faster and more accurately to roadway obstacles with good HID headlamps compared to halogen ones.<ref>{{cite web|url= http://www.lrc.rpi.edu/programs/transportation/pdf/PAL/PAL2001-vanderlofske.pdf |title=Evaluation of High Intensity Discharge Automotive Forward Lighting |access-date=2010-12-29}}</ref> Hence, good HID headlamps contribute to driving safety.<ref>{{cite web|url= http://www.drivingvisionnews.com/index.php?option=com_content&view=article&id=index.php?option=com_content&view=article&id=947 |title=VISION Congress report |website=Drivingvisionnews.com |date=2008-09-02 |access-date=2010-12-29}}</ref> The contrary argument is that glare from HID headlamps can reduce traffic safety by interfering with other drivers' vision.

===== Efficacy and output =====
[[Luminous efficacy]] is the measure of how much light is produced versus how much energy is consumed. HID lamps give higher efficacy than halogen lamps. The highest-intensity halogen lamps, H9 and HIR1, produce 2100 to 2530 lumens from approximately 70 watts at 13.2 volts. A D2S HID bulb produces 3200 lumens from approximately 42 watts during stable operation.<ref name=R37/> 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 an engine running time is with the lights on).

===== Longevity =====
The average service life of an HID bulb is 2000 hours, compared to between 450 and 1000 hours for a halogen lamp.<ref>{{cite web |url=http://www.friarsmarketing.com/Resources/Lighting%20Programme%20Autom%2367.pdf |title=Osram Automotive Lamps Lighting Programme 2005–06 |website=Friarsmarketing.com |access-date=2010-12-29 |url-status=dead |archive-url= https://web.archive.org/web/20080612073847/http://www.friarsmarketing.com/Resources/Lighting%20Programme%20Autom |archive-date=12 June 2008}}</ref>

==== Disadvantages ====

===== Glare =====
Vehicles equipped with HID headlamps (except motorcycles) are required by [[World Forum for Harmonization of Vehicle Regulations|ECE regulation 48]] also to be equipped with [[headlamp lens cleaning system]]s and automatic beam leveling control. Both of these measures are intended to reduce the tendency for high-output headlamps to cause high levels of [[Glare (vision)|glare]] to other road users. In North America, ECE R48 does not apply and while lens cleaners and beam levelers are permitted, they are not required;<ref>{{cite web |url=http://www.motivemag.com/pub/feature/tech/Motive_Tech_The_Difference_Between_US_and_European_Lights.shtml |title=The Difference Between US and European Lights |website=Motivemag.com |access-date=2010-12-29 |url-status=dead |archive-url=https://web.archive.org/web/20090501102913/http://www.motivemag.com/pub/feature/tech/Motive_Tech_The_Difference_Between_US_and_European_Lights.shtml |archive-date=1 May 2009 }}</ref> HID headlamps are markedly less prevalent in the US, where they have produced significant glare complaints.<ref name="NHTSA_8885"/> 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.<ref name=Vanderlofske>{{cite web |url=http://www.nhtsa.gov/DOT/NHTSA/NVS/Public%20Meetings/Presentations/2004%20Meetings/VanDerlofske.pdf |title=What Is Glare? p. 24 |website=Webcitation.org |access-date=2012-01-31 |url-status=dead |archive-url= https://web.archive.org/web/20111021132641/http://www.nhtsa.gov/DOT/NHTSA/NVS/Public%20Meetings/Presentations/2004%20Meetings/VanDerlofske.pdf |archive-date=21 October 2011}}</ref>

===== Mercury content =====
HID headlamp bulb types D1R, D1S, D2R, D2S and 9500 contain the toxic [[heavy metals|heavy metal]] [[mercury (element)|mercury]]. The disposal of mercury-containing vehicle parts is increasingly regulated throughout the world, for example under [https://web.archive.org/web/20101229225232/http://www.epa.gov/epawaste/hazard/wastetypes/universal/lamps/index.htm US EPA regulations]. Newer HID bulb designs D3R, D3S, D4R, and D4S which are in production since 2004 contain no mercury,<ref>{{cite web |url=http://www2.prnewswire.com/cgi-bin/stories.pl?ACCT=105&STORY=/www/story/07-27-2004/0002218858 |title=KOITO and DENSO Develop World's First Mercury-Free High-Intensity Discharge Headlamp System |website=Prnewswire.com |access-date=2010-12-29 |url-status=dead |archive-url=https://web.archive.org/web/20210308004434/http://www2.prnewswire.com/cgi-bin/stories.pl?ACCT=105&STORY=%2Fwww%2Fstory%2F07-27-2004%2F0002218858 |archive-date=8 March 2021 }}</ref><ref>{{cite web |url= http://goliath.ecnext.com/coms2/gi_0199-538206/KOITO-and-DENSO-Develop-World.html |title=HID headlamp system has a newly developed mercury-free discharge bulb |website=Goliath.ecnext.com |date=2004-07-27 |access-date=2010-12-29 |url-status=dead |archive-url= https://web.archive.org/web/20090528162933/http://goliath.ecnext.com/coms2/gi_0199-538206/KOITO-and-DENSO-Develop-World.html |archive-date=28 May 2009}}</ref> but are not electrically or physically compatible with headlamps designed for previous bulb types.

===== Cost =====
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 bulb relative to halogen bulbs.

=== {{Anchor|LED|Light-emitting diode}}LED ===<!-- This section is linked from [[Lexus]] -->

[[File:LED Headlamp inside.jpg|thumb|right|LED headlamp inside]]
[[File:2015 Audi A4 B9 S line Tangorot LED-Matrix-Scheinwerfer Detail.jpg|thumb|right|Digitally controlled adaptive non-glare multi-LED headlamp technology, on the [[Audi A4]]]]

====Timeline====
Audi showed the [[Audi Nuvolari]] concept car with LED headlights in 2003.<ref>{{Cite book|chapter-url=https://www.spiedigitallibrary.org/conference-proceedings-of-spie/5941/594101/LEDs-for-solid-state-lighting-and-other-emerging-applications/10.1117/12.625918.full|chapter=LEDs for solid state lighting and other emerging applications: status, trends, and challenges|first=M. George|last=Craford|editor-first1=Ian T. |editor-first2=John C. |editor-first3=Tsunemasa |editor-first4=Ian E. |editor-last1=Ferguson |editor-last2=Carrano |editor-last3=Taguchi |editor-last4=Ashdown |title=Fifth International Conference on Solid State Lighting |date=2 September 2005|publisher=SPIE|volume=5941|pages=594101|via=www.spiedigitallibrary.org|doi=10.1117/12.625918}}</ref><ref>{{Cite web|url=https://www.auto123.com/en/news/2003-audi-nuvolari-concept/43740/|title=2003 Audi Nuvolari Concept &#124; Car News &#124; Auto123|date=23 August 2003|website=auto123.com}}</ref><ref>{{Cite web|url=https://www.autopista.es/noticias-motor/audi-nuvolari-quattro_80682_102.html|title=Audi Nuvolari quattro|website=Autopista}}</ref> Automotive headlamp applications using [[light-emitting diode]]s (LEDs) have been undergoing development since 2004.<ref>{{cite press release |url= http://www.germancarfans.com/news.cfm/newsid/2050418.005/general/1.html |title=Hella LED Headlamp Study |website=Germancarfans.com |date=18 April 2005 |access-date=29 May 2014 |url-status=dead |archive-url= https://web.archive.org/web/20050913034114/http://www.germancarfans.com/news.cfm/newsid/2050418.005/general/1.html |archive-date=13 September 2005}}</ref><ref>{{cite web |url= http://www.fourtitude.com/cgi-bin/artman/exec/view.cgi/6/1113/printer |title=New-generation LED headlamp prototype with performance equal to HID |website=Fourtitude.com |access-date=2010-12-29 |url-status=dead |archive-url= https://web.archive.org/web/20101224205023/http://www.fourtitude.com/cgi-bin/artman/exec/view.cgi/6/1113/printer |archive-date=24 December 2010}}</ref> In 2004, [[Audi]] released the first car with LED daytime running lights and directionals, the 2004 [[Audi A8]] W12.<ref>{{Cite web|url=https://compoundsemiconductor.net/article-gen/83185|title=Lumileds LEDs used in Audi headlights - News|website=Compound Semiconductor}}</ref><ref>{{Cite web|url=https://www.photonics.com/Articles/Hella_Develops_Audi_LEDs/a18248|title=Hella Develops Audi LEDs|website=www.photonics.com}}</ref>

In 2006 the first series-production LED low beams were factory-installed on the [[Lexus LS (XF40)#LS 600h|Lexus LS 600h / LS 600h L]]. The high beam and turn signal functions used filament bulbs. The headlamp was supplied by [[Koito Industries Ltd]].

In 2007 the first headlamps with all functions provided by LEDs, supplied by [[Magneti Marelli|AL-Automotive Lighting]], were introduced on the V10 [[Audi R8 (Type 42)|Audi R8]] sports car (except in North America).<ref>http://www.magnetimarelli.com/excellence/technological-excellences/the-full-led-technology The Full-LED Technology for Automotive Lighting</ref>

In 2009 [[Hella (company)|Hella]] headlamps on the 2009 [[Cadillac Escalade]] Platinum became the first all-LED headlamps for the North American market.<ref>{{cite journal |title=LEDing the way |journal=Automotive Engineering International |date=2008 |volume=116 |page=20 |url= https://books.google.com/books?id=wV5KAQAAIAAJ&q=First+production+led+headlights |access-date=22 November 2021 |publisher=SAE International |quote=The 2008 Cadillac Escalade Platinum has earned the distinction of being the first production vehicle in the world with all - LED forward lighting}}</ref>

In 2010 the first all-LED headlamps with [[Headlamp#Adaptive highbeam|adaptive high beam]] and what [[Mercedes-Benz|Mercedes]] called the "Intelligent Light System" were introduced on the 2011 [[Mercedes-Benz CLS-Class (W218)|Mercedes CLS]].

In 2013 the first digitally controlled full-LED glare-free "Matrix LED" adaptive headlamps were introduced by [[Audi]] on the facelifted [[Audi A8#2014 model year facelift|A8]], with 25 individual LED segments.<ref>{{Cite web |date=2014-10-16 |title=Audi Matrix LED Headlights |url=https://www.audi.com/com/brand/en/vorsprung_durch_technik/content/2013/10/audi-a8-in-a-new-radiant-light.html |access-date=2022-12-15 |archive-url=https://web.archive.org/web/20141016191416/https://www.audi.com/com/brand/en/vorsprung_durch_technik/content/2013/10/audi-a8-in-a-new-radiant-light.html |archive-date=16 October 2014 }}</ref> The system dims the light that would shine directly onto oncoming and preceding vehicles, but continues to cast its full light on the zones between and beside them. This works because the LED high beams are split into numerous individual light-emitting diodes. High-beam LEDs in both headlights are arranged in a matrix and adapt fully electronically to the surroundings in milliseconds. They are activated and deactivated or dimmed individually by a control unit. In addition, the headlights also function as a cornering light. Using predictive route data supplied by the [[MMI navigation plus]], the focus of the beam is shifted towards the bend even before the driver turns the steering wheel. In 2014: [[Mercedes-Benz]] introduced a similar technology on the facelifted [[Mercedes-Benz CLS-Class (W218)|CLS-Class]] in 2014, called Multibeam LED, with 24 individual segments.<ref>{{cite press release |url= http://media.daimler.com/dcmedia/0-921-1708962-1-1712129-1-0-0-0-0-0-0-0-0-1-0-0-0-0-0.html |archive-url= https://web.archive.org/web/20160304060021/http://media.daimler.com/dcmedia/0-921-1708962-1-1712129-1-0-0-0-0-0-0-0-0-1-0-0-0-0-0.html |archive-date=2016-03-04 |date=4 March 2016 |title=Multibeam LED headlamps: The future of light}}</ref>

As of 2010, LED headlamps such as those available on the [[Toyota Prius]] were providing output between halogen and HID headlamps,<ref name="DVN_Dorissen">{{cite web|url= http://www.drivingvisionnews.com/index.php?option=com_content&view=article&id=1397:interview-with-hans-theo-dorissen-&catid=38:previous-news&Itemid=191 |title=DVN Interview with Hella's Hans-Theo Dorissen, 2 June 2009 |website=Drivingvisionnews.com |access-date=2010-12-29}}{{registration required|date=November 2012}}</ref> with system power consumption slightly lower than other headlamps, longer lifespans, and more flexible design possibilities.<ref>{{cite web |url= http://www.al-lighting.de/index.php?id=984 |title=Production LED headlamp technology & design as of 2007 |website=Al-lighting.de |access-date=2010-12-29 |url-status=dead |archive-url= https://web.archive.org/web/20101123164242/http://www.al-lighting.de/index.php?id=984 |archive-date=23 November 2010}}</ref><ref>{{cite web |url=http://www.treehugger.com/files/2006/10/led_headlights.php |title=LED Headlights Introduced |publisher=TreeHugger |access-date=2009-11-29 |archive-date=1 July 2009 |archive-url=https://web.archive.org/web/20090701091040/http://www.treehugger.com/files/2006/10/led_headlights.php |url-status=dead }}</ref> As LED technology continues to evolve, the performance of LED headlamps was predicted to improve to approach, meet, and perhaps one day surpass that of HID headlamps.<ref>{{cite web|url= http://www.drivingvisionnews.com/index.php?option=com_content&view=article&id=1474:interview-with-michael-hamm-&catid=1:latest-news |title=DVN Interview with AL's Michael Hamm, 8 July 2009 |website=Drivingvisionnews.com |access-date=2010-12-29}}</ref> That occurred by mid-2013, when the Mercedes S-Class came with LED headlamps giving higher performance than comparable HID setups.<ref>{{cite web|url= https://www.drivingvisionnews.com/index.php?option=com_content&view=article&id=4897&Itemid=46
 |title=All-LED Projectors for Merc S-Class, 29 July 2013 |website=Drivingvisionnews.com |access-date=2018-05-09}}</ref>

LED headlamps in recent vehicles have been widely criticized for being too bright and blinding other drivers. [[Federal Motor Vehicle Safety Standard 108]] has not been updated since the introduction of LEDs, and some manufacturers have reportedly engineered headlamps to have a dark spot where they are measured according to the regulation while being over-illuminated in the rest of the field.<ref>{{Cite web |date=2024-12-03 |title=Asleep at the Wheel in the Headlight Brightness Wars |url=https://www.theringer.com/2024/12/03/tech/headlight-brightness-cars-accidents |access-date=2024-12-06 |website=www.theringer.com |language=en}}</ref>

====Cold lenses====
Before LEDs, all light sources used in headlamps (tungsten, halogen, HID) emitted [[infrared]] energy that can thaw built-up snow and ice off a headlamp lens and prevent further accumulation; LEDs do not. Some LED headlamps move heat from the heat sink on the back of the LEDs to the inner face of the front lens to warm it up,{{Citation needed|date=May 2018}} while on others no provision is made for lens thawing.

===Laser===
[[File:Audi at CES 2014 (11891990375).jpg|thumb|Audi Matrix Laser headlamp at [[Consumer Electronics Show]] 2014]]
A laser lamp uses mirrors to direct a [[laser]] on to a [[phosphor]] that then emits a light. Laser lamps use half as much power as [[LED lamp]]s. They were first developed by [[Audi]] for use as headlamps in the [[24 Hours of Le Mans]] in 2014.<ref>{{cite web|first=Virginia |last=Herndon |url=https://www.audiusa.com/newsroom/news/press-releases/2014/01/laser-light-assists-audi-drivers-le-mans |title=Laser light assists Audi drivers at Le Mans |website=Audiusa.com |date=2014-01-20 |access-date=2017-07-18}}</ref>

In 2014, the [[BMW i8]] became the first production car to be sold with an auxiliary high-beam lamp based on this technology.<ref>http://www.autocar.co.uk/car-news/new-cars/bmw-i8-will-be-first-offer-new-laser-lighting-tech BMW i8 will be first to offer new laser lighting tech</ref> The limited-production [[Audi R8]] LMX uses lasers for its spot lamp feature, providing illumination for high-speed driving in low-light conditions. The [[Rolls-Royce Phantom VIII]] employs laser headlights with a high beam range of over 600 meters.<ref name=officialPR1>{{cite web |url= https://www.press.rolls-roycemotorcars.com/rolls-royce-motor-cars-pressclub/article/detail/T0273206EN/the-new-rolls-royce-phantom |title=The new Rolls-Royce Phantom |website=Rolls-Royce Motor Cars PressClub |date=2017-07-27 |access-date=2017-07-27 |url-status=live |archive-url= https://web.archive.org/web/20170730014804/https://www.press.rolls-roycemotorcars.com/rolls-royce-motor-cars-pressclub/article/detail/T0273206EN/the-new-rolls-royce-phantom |archive-date=2017-07-30 }}</ref>