Car Rear-view mirror explained
A rear-view mirror is a mirror in automobiles and other vehicles, designed to allow the driver to see rearward through the vehicle's backlight (rear windshield or windscreen).
In cars, the rear-view mirror is usually affixed to the top of the windshield on a double-swivel mount allowing it to be adjusted to suit the height and viewing angle of any driver and to swing harmlessly out of the way if impacted by a vehicle occupant in a collision.
The rear-view mirror is augmented by one or more side-view mirrors, which serve as the only rear-vision mirrors on motorcycles and bicycles.
The rear-view mirror's earliest known use and mention is by Dorothy Levitt in her 1906 book The Woman and the Car which noted that women should "carry a little hand-mirror in a convenient place when driving" so they may "hold the mirror aloft from time to time in order to see behind while driving in traffic", thereby inventing the rear view mirror before it was introduced by manufacturers in 1914. The earliest known rear-view mirror mounted on a motor vehicle appeared in Ray Harroun's Marmon racecar at the inaugural Indianapolis 500 race in 1911. Although Harroun's 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. Harroun also claimed that the mirror vibrated constantly due to the rough brick surface, rendering it largely useless.
Elmer Berger is usually credited with inventing the rear-view mirror, though in fact he was the first to develop it for incorporation into production streetgoing automobiles
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. As many as 50 small children are killed by SUVs every year in the USA because the driver cannot see them in their rear-view mirrors. Camera systems are usually mounted to the rear bumper or lower parts of the car, allowing for better rear visibility.
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.
A prismatic rear-view mirror—sometimes called a "day/night mirror"—can be tilted to reduce the brightness and glare of lights, mostly for high-beam headlights of vehicles behind which would otherwise be reflected directly into the driver's eyes at night. This type of mirror is made of a piece of glass that is wedge-shaped in cross section—its front and rear surfaces are not parallel.
On manual tilt versions, a tab is used to adjust the mirror between "day" and "night" positions. In the day view position, the front surface is tilted and the reflective back side gives a strong reflection. When the mirror is moved to the night view position, its reflecting rear surface is tilted out of line with the driver's view. This view is actually a reflection off the low-reflection front surface; only a much-reduced amount of light is reflected into the driver's eyes.
"Manual tilt" day/night mirrors first began appearing in the 1930s and became standard equipment on most passenger cars and trucks by the early 1970s.
In the 1950s, American inventor Jacob Rabinow developed a light-sensitive automatic mechanism for the wedge-type day/night mirror. Several Chrysler Corporation cars offered these automatic mirrors as optional equipment as early as 1959, but few customers ordered them for their cars and the item was soon withdrawn from the option lists.Several automakers began offering rear-view mirrors with automatic dimming again in 1983, and it was in the late 1980s that they began to catch on in popularity
Current systems usually use photosensors mounted in the actual rear-view mirror to detect light and dim the mirror by means of electrochromism. This electrochromic feature has been also incorporated into side-view mirrors allowing them to dim and reduce glare as well.