From Light Emitting Diode three LED are abbreviations for Chinese, translated as " led", just as its name implies LED is a kind of can transform electrical energy into light energy electronic device having a diode characteristics. At present the different light emitting diode can be emitted from the infrared to the ultraviolet light of a different wavelength, in addition to the Blu-ray LED coated with fluorescent powder, the blue light into white light white LED.
LED color and process:
    Manufacture of LED materials is different, can produce with photons of different energies, which can control the LED light wavelength, orspectrum or color. The first in the history of the LED by the use of the material is gallium arsenic ( As ) ( Ga ), its forward PN junction voltage drop ( VF, can be understood as light or voltage ) is 1.424V, emits light for infrared spectroscopy. Another commonly used LED material for the phosphorus ( P ) gallium ( Ga ), the positive voltage2.261V PN junction, light green.
    Based on the two kinds of materials, early LED industrial use GaAs1-xPx materials structure, theoretically can be produced from infrared light to green light within any wavelength of LED subscript X, on behalf of phosphorus arsenic replacing the percentage. General pressure drop can be determined through the PN junction LED wavelength color. As is typical of the red LED GaAs0.6P0.4, GaAs0.35P0.65LED GaAs0.14P0.86orange light, yellow light LED. Due to manufacturing using gallium, arsenic, phosphorus of three elements, so called the LED luminous tube for three elements. While GaN ( GAN ) blue LED, GaP green LED and GaAs infrared LED, known as the two elements led. But at present most new technology is mixed with aluminium ( Al ), calcium ( Ca ), indium ( In ) and nitrogen ( N ) of four kinds of elements in the AlGaInN element of the four materials to manufacture the four elements of LED, can cover all visible light and ultraviolet spectral range.
    Luminous intensity:
    Luminous intensity measurement unit has a unit of illuminance ( Lux Lux ), luminous flux unit ( lumen Lumen ), luminous intensity ( Candle power candle )
1CD ( candle ) refers to the radiation from the object, at a temperature of freezing, every 1/60square centimeter luminous intensity. ( previously referred to2.2 cm in diameter, mass is 75.5 grams oil candle, burning 7.78grams per hour, flame height is 4.5cm, along the horizontal direction of the luminous intensity )
1L ( lumen) of1 CD candle light irradiation at a distance of 1 cm, with an area of 1 square centimeters in the plane of the luminous flux.
1Lux ( Lux ) refers to the 1L flux evenly distributed in the area of 1 square meters of the illumination.
General active luminous body adopts the luminous intensity unit candle CD, such as an incandescent lamp, LED; reflection or transmission of objects using a luminous flux lumen L units, such as the LCD projector; and the unit of illuminance lux Lux, generally used for photography and other fields. Three kinds of unit of measure in numerical value is equivalent, but needs from different angles to understand. For example: if a LCD projector brightness ( luminous flux of1600 lumens ), its projection onto the total reflection screen size is 60 inches (1square meters ), the illumination of 1600 lux, assuming that the light output from the light source1 cm, port area is 1 squares centimetre, then a light mouth luminous intensity is1600CD. But the real LCD projector as light propagation loss, reflection or film loss and light distribution is not uniform, the brightness will be greatly reduced, generally have50% efficiency is very good.
In practical use, often using intensity calculation easier to surveying and mapping data unit or changed to use. For the LED display this active luminous bodies generally use CD / square meter as the unit of luminous intensity, and in line with the angle of observation for the auxiliary parameter, which is equivalent to the screen surface of the unit of illuminance lux; the numerical and screen the effective display area is multiplied, get the whole screen body at the best angle of luminous intensity, assuming that the screen body each pixel in the luminous intensity in the corresponding space constant, this value can be considered but also the entire screen body of the luminous flux. General outdoor LED display is required to achieve a4000CD / square meters above the brightness can be in daylight was an ideal display effect. Common indoor LED, maximum brightness in 700~ 2000 CD / square meters.
A single LED luminous intensity in CD as a unit, at the same time with the angle parameter, light intensity and LED color it doesn't matter. Single luminous intensity from several to tens of thousands of mCD ranging from mCD. LED manufacturers in the luminous intensity refers to LED in20mA current under light, the best angle of view and center position of the point of maximum intensity. Package LED top lens shape and LED chip from the top to the position of the lens determines the LED perspective and light intensity distribution. In general the same LED angle is bigger, the maximum luminous intensity is small, but in the entire three-dimensional hemispherical total luminous flux constant.
When more than one LED more compact rule emissions, the luminous sphere superimposed on each other, resulting in the luminescence of luminous intensity distribution is more uniform plane. In the calculation of display luminous intensity, according to the LED angle and LED emission density, the manufacturers to provide the maximum point of luminous intensity values are multiplied by 30% to 90%, as a single average luminous intensity.
General LED luminous life is very long, manufacturers are generally marked for more than 100000 hours, should also pay attention to the actual LED brightness decay cycles, such as most used car taillight UR red tube lighting a dozen to several hours later, only half of the original brightness. Brightness attenuation cycle with LED production materials technology has the very big relations, the general economic conditions permit should choose brightness decays slower than the four element LED.
Color, white balance:
    White is the color of red and green and blue brightness proportion, when the light is green with 69% luminance brightness, red21%, blue brightness is 10%, color mixing human eyes feel is pure white. But LED red green and blue chromaticity coordinates for process reasons cannot reach the chromatographic effect, while the control colors comprises a deviation of the color brightness gets white light, known as color.
    When the full color LED display screen color, in order to achieve the best brightness and the lowest cost, should choose trichromatic luminous intensity into roughly3:6:1 ratio of LED devices
    Composition of pixel.
    White balance requirements of three primary colors in the same tone gray value synthesis is still pure white.
Colors, primary colors:
Color refers to the synthesis of a variety of colors of the basic color. Light of red, green, and blue primary colors for the spectrum, table, table three vertex as the ideal primary color wavelength. If the color deviation can be synthesized, the color of the region can be reduced, the spectral form in the triangle will be reduced, from the visual point of view, the color will not only have deviation, rich degree of reduction.
    LED issued a red, green, blue lines according to their different characteristics of wavelength and can be divided into pure red, purple, orange, orange, orange, yellow, green, green, green, blue and green, blue, purple, blue, orange, green, blue and purple. The three primary colors of green is most important, because green took white in 69% brightness, color and transversely arranged in the center of the table. Therefore in weighing the color purity and price relationship between the two, the green is considered on the object.