Editing Headlamp (section)

=== {{Anchor|Automatic beam switching|Automatic high beam}} Automatic beam switching ===
Even when conditions would warrant the use of high-beam headlamps, drivers often do not use them.<ref>{{cite report |last1=Mefford |first1=M.L. |last2=Flannagan |first2=M.J. |last3=Bogard |first3=S.E. |title=Real-world use of high-beam headlamps |publisher=University of Michigan Transportation Research Institute |year=2006 |hdl=2027.42/58716 |hdl-access=free}}</ref> 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 Corporation|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.<ref>{{Cite web|url=http://www.lov2xlr8.no/brochures/olds/53olds/53olds.html|title = Hot Cars}}</ref><ref>[http://www.lov2xlr8.no/brochures/olds/53olds/bilder/20.jpg Brochure] lov2xlr8.no</ref> 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 By the early 1970s, this option was withdrawn from all GM models except [[Cadillac]], on which GuideMatic was available through 1988.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|date=May 2011}}

[[Ford Motor Company|Ford]]- and [[Chrysler Corporation|Chrysler]]-built vehicles were also available with the GM-made dimmers from the 1950s through the 1980s.{{Citation needed|date=May 2011}} A system called "AutoDim" was offered on several [[Lincoln (automobile)|Lincoln]] models starting in the mid-1950s, and eventually the [[Ford Thunderbird]] and some [[Mercury (automobile)|Mercury]] models{{Vague|date=May 2011}} offered it as well.{{Citation needed|date=May 2011}} Premium [[Chrysler Corporation|Chrysler]] and [[Imperial (automobile)|Imperial]] models offered a system called ''Automatic Beam Control'' throughout the 1960s and early 1970s.{{Citation needed|date=May 2011}}

==== Rabinow dimmer ====
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 distinguish 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,<ref>{{cite web |url=http://museum.nist.gov/exhibits/rabinow/patents.html |title=Jacob Rabinow - patent 2917664 |website=Museum.nist.gov |access-date=20 May 2014 |archive-url= https://web.archive.org/web/20140530000016/http://museum.nist.gov/exhibits/rabinow/patents.html |archive-date=30 May 2014 |url-status=dead}}</ref> but no automaker purchased the rights, and the problematic photoresistor type remained on the market through the late 1980s.<ref>{{cite book |last=Rabinow |first=Jacob |author-link=Jacob Rabinow |title=Inventing for Fun and Profit |publisher=San Francisco Press |date=May 1990 |isbn=978-0-911302-64-6 |url-access=registration |url= https://archive.org/details/inventingforfunp00rabi }}</ref>

==== Bone-Midland lamps ====
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.<ref>{{cite journal|url= https://books.google.com/books?id=TOEDAAAAMBAJ&pg=PA70 |title=Built in Visor Shades Headlamps |journal=Popular Mechanics |volume=106 |issue=2 |date=August 1956 |page=70 |access-date=29 May 2014}}</ref>

==== Camera-based dimmer ====
{{unreferenced section|date=November 2012}}
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 [[Automobile safety#Driver assistance|driver assistance]] systems by automakers worldwide. The headlights will dim when a bright reflection bounces off of a street sign.