Editing Backlight (section)

{{short description|Form of illumination used in liquid crystal displays}}
{{about|backlights in liquid crystal displays|the rear window of an automobile|Car glass|the lighting design practice|Backlighting (lighting design)|other uses|Backlight (disambiguation)}}
{{Use dmy dates|date=March 2023}}
[[File:Backlit LCD display.jpg|thumbnail|Views of a [[liquid-crystal display]], both with [[electroluminescence|electroluminescent]] backlight switched on (top) and switched off (bottom)]]

A '''backlight''' is a form of illumination used in [[liquid-crystal display]]s (LCDs) that provides light from the back or side of a display panel. LCDs do not produce light on their own, so they require illumination—either from [[available light|ambient light]] or a dedicated light source—to create a visible image. Backlights are commonly used in [[smartphone]]s, [[computer monitor]]s, and [[LCD television]]s. They are also used in small displays, such as [[Watch|wristwatches]], to enhance readability in low-light conditions.<ref>{{US Patent|4096550}}: W. Boller, M. Donati, J. Fingerle, P. Wild, ''Illuminating Arrangement for a Field-Effect Liquid-Crystal Display as well as Fabrication and Application of the Illuminating Arrangement'', filed 15 October 1976.</ref>

Typical light sources for backlights include [[light-emitting diode]]s (LEDs) and [[cold cathode fluorescent lamp]]s (CCFLs).

Simple types of LCDs, such as those used in [[pocket calculator]]s, are built without an internal light source and rely on external light sources to make the display image visible to the user. However, most LCD screens are designed with an internal light source. These screens consist of multiple layers, with the backlight typically being the first layer from the back.

[[Light valve]]s regulate the amount of light reaching the eye by blocking its passage in specific ways. Most LCDs use a combination of a fixed [[polarizing filter]] and a switching one to block unwanted light.

Many types of displays other than LCD generate their own light and do not require a backlight, for example, [[OLED]] displays, [[cathode-ray tube]] (CRT), and plasma (PDP) displays.

A similar type of technology is called a [[frontlight]], which illuminates an LCD from the front.

A review of some early backlighting schemes for LCDs is given in a report ''Engineering and Technology History'' by [[Peter J. Wild]].<ref>{{cite web|url=http://ethw.org/First-Hand:Liquid_Crystal_Display_Evolution_-_Swiss_Contributions#Backlit_LCDs|title=First-Hand Histories: Liquid Crystal Display Evolution - Swiss Contributions|publisher=Engineering and Technology History Wiki|access-date=30 June 2017|url-status=live|archive-url=https://web.archive.org/web/20170703123209/http://ethw.org/First-Hand:Liquid_Crystal_Display_Evolution_-_Swiss_Contributions#Backlit_LCDs|archive-date=3 July 2017}}</ref>