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Backlight is a category of illumination used in monitors utilizing liquid crystal display (LCD) technology. Liquid crystal display monitors cannot produce light by themselves, and must depend on light sources to provide visible images. Apart from being used in computer displays, LCD televisions and smartphones, backlights are also used in small displays such as wristwatches and pocket calculators for improving the readability in low-light conditions.
Unlike front lights which illuminate from the front, backlights usually produce illumination from the sides or from the back of the screen. Most liquid crystal display screens consist of several layers, with backlight being the layer farthest back. The light valves help in changing the amount of light reaching the human eyes, usually by blocking light's passage with the help of a polarizing filter.
There are five main categories of light sources used for backlights:
Among these, only electroluminescent panels are capable of providing uniform light across the entire surface. For other light sources, a diffuser needs to be used for providing uniform light. White backlighting is much more predominant than colored backlighting.
Backlights help in achieving thinner, lighter and more efficient displays. LCD screens making use of backlighting have a longer lifespan compared to existing monitor technologies, including OLED. However, compared to devices such as ones based on OLED technology, displays making use of backlight consume more power.