A backlight is the set of optoelectronic components responsible for generating light in a liquid crystal display (LCD), which does not emit light by itself. The backlight is placed behind (in transmissive displays) or beside (in some transflective displays) the panel to provide image visibility under various lighting conditions.
The most commonly used light sources are LEDs, which have replaced older CCFL tubes. A typical backlight system includes LEDs, light-guiding elements (light pipes, diffusers, prisms), and reflective or directional layers. Advanced designs use local dimming, i.e. zone-based brightness control, to improve contrast and reduce power consumption.
Key parameters of the backlight are brightness (cd/m²), uniformity, color temperature, and lifetime. A properly chosen backlight system is especially important in outdoor, industrial, medical and military applications, where screen readability must be maintained regardless of ambient conditions.
