Backlight - Wikipedia, the free encyclopedia


** Backlight **

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This article is about backlights in liquid crystal displays. For the rear
window of an automobile, see Car glass. For the lighting design practice,
see Backlighting (lighting design). For the Portuguese film, see Backlight
Animation of an LCD, both unlit and with electroluminescent backlight
switched on.

A *backlight* is a form of illumination used in liquid crystal displays
(LCDs). As LCDs do not produce light by themselves (unlike for example
Cathode ray tube (CRT) displays), they need illumination (ambient light or
a special light source) to produce a visible image. Backlights illuminate
the LCD from the side or back of the display panel, unlike frontlights,
which are placed in front of the LCD. Backlights are used in small displays
to increase readability in low light conditions such as in
wristwatches,^[1] and are used in smart phones, computer displays and LCD
televisions to produce light in a manner similar to a CRT display. A review
of some early backlighting schemes for LCDs is given in a report
/Engineering and Technology History/ by Peter J. Wild^[2] under its section
/Backlit LCDs/.

Simple types of LCDs such as in pocket calculators are built without an
internal light source, requiring external light sources to convey the
display image to the user. Most LCD screens, however, are built with an
internal light source. Such screens consist of several layers. The
backlight is usually the first layer from the back. Light valves then vary
the amount of light reaching the eye, by blocking its passage in some way.
Most use a fixed polarizing filter and a switching one, to block the
undesired light.


· 1 Light source types
· 2 Usage

· 2.1


how are lcd screens backlit

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