Automatic headlight dimmer
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An automatic headlight dimmer (also called automatic beam control) is a system to automatically switch between the low and high headlight beams on an automobile.
Drivers could also use standard headlight dimmers (such as foot-operated devices) to override the automatic headlight dimmer on cars so equipped.
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[edit] Early systems
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General Motors introduced the first automatic headlight dimmer called the Autronic Eye in 1952, on their Cadillac and Oldsmobile models; Buick, Pontiac and Chevrolet models began offering this feature in 1953. The system's photoresistor and associated circuitry were housed in a gunsight-like tube on the dashboard.
GM discarded the troublesome Autronic Eye after 1958 in favor of a system called GuideMatic in reference to GM's Guide lighting division. The GuideMatic had a more compact dashtop housing than the Autronic Eye, and a switch that allowed drivers 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 By the mid-1960s, this option was withdrawn from all GM models except Cadillac, on which GuideMatic was available through 1988.
Ford- and Chrysler-built vehicles were also available with automatic headlight dimmers from the 1950s through the 1980s. An automatic headlight dimmer called AutoDim was offered on several Lincoln models starting in the mid-1950s, and eventually the Ford Thunderbird and some Mercury models had it available as well. Premium Chrysler and Imperial models offered a system called Automatic Beam Control throughout the 1960s and early 1970s.
Though these electric eye-based systems evolved, growing more compact and moving from the dashboard to a less conspicuous location behind the radiator grill, they remained unable to accurately 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 spuriously dipped to low beam in response to road sign reflections of the vehicle's own headlamps.
[edit] Rabinow dimmer
American inventor Jacob Rabinow devised and refined a scanning automatic dimmer system impervious to streetlights and reflections[1], but no automaker purchased the rights, and the problematic electric-eye type remained on the market through the late 1980s[2].
[edit] Camera-based systems
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.
[edit] References
- ^ Jacob Rabinow - patent 2917664
- ^ Rabinow, Jacob (1990-5). Inventing for Fun and Profit. San Francisco, CA: San Francisco Press. ISBN 978-0911302646.
