Rear-view mirror
From Wikipedia, the free encyclopedia
A rear-view mirror is a functional type of mirror found on automobiles and other vehicles, designed to allow the driver to see the area behind the vehicle through the back window.
Rear-view mirrors are sometimes confused with side-view mirrors, a different type of mirror found on the left- and right-hand sides of most modern vehicles. Though these mirrors do face backwards, they are meant to show the driver the traffic to the left- and right-hand sides of the automobile. Inside rear-view mirrors (and driver-side side-view mirror) are specifically mandated by legislation to have 'unit magnification' and thus are not convex[1]. The driver is close enough to both these mirrors for simple head motion to be sufficient signficantly to expand the field of view. The passenger side side-view mirror is far enough away for the field of view to be fixed, despite movement of the driver and a convex mirror is desirable to expand the field of view.
Typically, the rear-view mirror is affixed to the top of the windshield on a swivel mount allowing it to be freely rotated. Certain car models have the rear-view mirror mounted on top of the dashboard. When adjusting the mirror, it is advised to sit in the driver's seat in the same manner that you will be sitting while driving. Their utility may be diminished in cars with large spoilers or tiny back windows, obstructions in the back seat or trailer. Vanity mirrors attached to sun visors do not meet the adjustment requirements of rear-view mirrors and cannot be used as such. Inside rear-view mirrors are designed to break away upon collision to minimize injury to occupants who are thrown against it.
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[edit] History
Although many people imagine the rear-view mirror was designed for safety, in fact its origins are much more exciting. The earliest known semblence of a rear-view mirror on a motor vehicle appeared in Ray Harroun's Marmon racecar at the inaugural Indianapolis 500 race in 1911. According to Al Binder of Ward's Auto World:
- As per the custom of the day, all cars except Harroun's carried riding mechanics who, among other things, helped the driver keep track of other vehicles during the race. Unable to find a mechanic to ride with him, Harroun installed a mirror on his car so he could view what was happening behind him and be alert to any cars overtaking him. Automotive historians credit this as the first use of a rear view mirror on an automobile.[2]
Although Harroun's use is the first known use of such a mirror on a motor vehicle, Harroun himself claimed he got the idea from seeing a mirror used for the same purpose on a horse-drawn vehicle in 1904. [1]
The invention seems to have worked — Harroun won the race, netting a US$14,250 prize, equivalent to about US$270,000 in 2003 dollars.
However, the rear-view mirror had to wait for Elmer Berger, the man usually credited with inventing the rear-view mirror, to first develop them for street use.
[edit] Power mirrors
Side-view mirrors have the mirror's face mounted on a swivel, while the encasement is usually fixed. They are adjusted by various devices, ranging from simple direct manipulation of the mirror to sticks or knobs inside the vehicle to motorized controls inside the vehicle ("power mirrors").
In nowadays vehicles (e.g. Saab 9-5), the side-view mirrors can be power-adjusted and are linked into the electrically adjustable driver's seat memory controls, so that different drivers can store individual settings, restoring them at the push of a button. This same model has an extra control, for depressing the passenger door mirror (for viewing the curb when parking) and a further control for retracting the side-view mirrors, out of harm's way, when entering a very narrow space or when leaving the car parked.
Also, exterior mirror can be power-folded.
[edit] Augmentations and alternatives
Recently, rear-view video cameras have been built into many new model cars. This was partially in response to the rear-view mirrors' inability to show the road directly behind the car, due to the rear deck or trunk obscuring as much as 3-5 metres (10-15 feet) of road behind the car. For example, as many as 50 times a year, small children are killed by SUVs in America because the driver cannot see them in their rear-view mirrors [3]. These camera systems are usually mounted to the bumper or lower parts of the car allowing for better rear visibility. In addition, rear-facing sonar arrays and back up beepers help avoid accidents while reversing.
Aftermarket secondary rear-view mirrors are available. They attach to the main rear-view mirror and are independently adjustable to view the back-seat. This is useful to parents to monitor their children in the backseat.
Aftermarket mirrors can be attached as extensions to the door mirrors, that allow a driver to see behind when towing a caravan.
A similar device can be fitted to the rear of a van or SUV, to allow viewing down behind the vehicle, for close parking.
[edit] Dimming
A traditional rear-view mirror can be tilted to reduce the brightness and glare of lights, mostly for headlights shining directly on the eye level at night. This manual tilt mirror is made of a piece of glass that is wedge-shaped in cross section- its front side and back (silvered) side are not parallel, unlike normal mirror glass. In the default day view, the front side is tilted and the back side (which has a reflective coating, usually with silver like a mirror) is head-on and will give a strong reflection. When the mirror is tilted, its front side is head-on and the back is tilted. This view is actually a reflection off the clear, front piece of the glass rather than the back silver-coated part. Since the front part allows most of the light to go through, only a small amount of light is now reflected into your eyes.
Some rear-view mirrors have electronic auto-dimming features built in (mirrors with automatic anti-glare function) while others are adjustable so that a lower light level setting may be used. Because of this it is advisable to set the darker setting to be aimed lower in the car than the lighter setting. This is mostly because at night when you readjust the mirror to use the darker setting the lighter angles will be pointed to the lower contrast roof of the vehicle instead of the higher contrast areas such as the backs of the seats.
[edit] Bicycles
Some bicycles have rearview mirrors. However, motorcycles carry that feature more frequently than pedal bikes.
[edit] In Art
In modern art, particularly music and poetry, the rear-view mirror has become a common metaphor for reflecting upon the past, whether upon one's own memories or a time even more distant. For example, Jane Sequoya's "Scene Through the Rear-View Mirror" expresses a woman's regret for a lost love partly by comparison with the lost Native American people of the prairies [4].
In popular music, artists ranging from Alicia Keys to Meat Loaf to the Starland Vocal Band as well as Pearl Jam have written songs with "Rear View Mirror" in the title. The metaphor is particularly prominent in country music, where it's featured in hits such as Jo Dee Messina's "Bye Bye", Chely Wright's "Shut Up and Drive", Doug Supernaw's "She Never Looks Back", and Julie Roberts' "Break Down Here".
In the Gang Related (film) sound track, Tupac Shakur's song "Staring Through my Rear View" indeed the rear view is a metaphor to the past.
[edit] References
- ^ Davidson, Donald. (2006). "The Talk of Gasoline Alley" [Radio program]. WIBC, May 28, 2006.
