LED v. LCD

LED

LED throwies. Image courtesy of Instructables.com. An LED (light-emitting diode) is a small semiconductor device that emits light of a single wavelength when a current is passed through it. LEDs come in a variety of colors; infrared and ultraviolet models are also produced. Visible LEDs are used in indicator lights, dynamic signs and displays, traffic and vehicle lighting, flashlights, and increasingly, as an efficient replacement for general purpose incandescent lights. LEDs have non-visual communications and sensor applications in fiber optics, remote controls, computer mice, and UV sterilization systems.

LCD

A typical printer LCD message. An LCD (liquid crystal display) is a thin, flat electronic display used in televisions, computers, digital clocks and watches, calculators, and instrument panels. Because of their reduced size and superior efficiency, LCDs have almost completely supplanted cathode ray tubes as the dominant technology in TV and computer monitors.

An LCD blocks polarized light when a voltage is applied, making it black, and admits light when it’s off. Color LCDs can be made with the addition of color filters. LCDs don’t produce their own light; inexpensive monochrome readouts, such as those found in calculators, reflect ambient light. Some monochrome LCDs and high-resolution color screens require a separate backlight.

LED and LCD technologies can coexist or be used interchangeably. In many devices, LEDs are used as status lights, while LCDs display messages or video. Either technology can be used in seven-segment displays. For example, early digital watches used red LEDs, but these were soon replaced by lower-power LCDs. New, slim, high-contrast LCD televisions actually employ LED backlights.