Atomic electrons have a lot of energy levels, when the electrons from the high power level to low power level transitions, the energy of the electron is reduced, while reducing the energy converted Photon emission out. A large number of these photon laser. LED principle similar. However different, LED to light not by the electronic transitions of atoms within, but by applying voltage to the LED Both ends of the PN junction, the PN junction itself to the formation of an energy level (in fact, is a series of energy level), and then the electronic transitions in the energy levels and generate light The sub to light. New LED display pieces of low power consumption, high brightness, long life, small size, etc., from the LED display pieces hair Development Brief History began to explore the surface mount LED, LED and lighting with LED trends, engaged in the development of display devices in automotive applications State engineers have a certain reference value. The world's first commercial light-emitting diode (LED) is made with germanium material in 1965, priced at 45 U.S. Yuan. In 1968, the research and development of LED breakthrough GaAsP devices efficient use of nitrogen-doping process reaches the lumens / watt, and And is able to glow red, orange and yellow light. In 1971, the industry has introduced the GaP green die LED with the same efficiency. Began in 1972 A small amount of the LED display used in watches and calculators. The world's first LED watch was originally sold or expensive jewelry stores, its price Up to $ 2,100. Almost at the same time, Hewlett-Packard and Texas Instruments have also introduced a calculator with a 7-segment red LED display. 1970s As the LED devices in the home and office Public equipment in the large number of applications, LED prices plummet. In fact, LED is the main figures of that era with text display technology. However in many cases Multiple commercial equipment, LED display gradually by the fierce competition from other display technologies such as LCD, plasma and vacuum fluorescent tube display Indicator.