LED basic knowledge

Leds are Light Emitting Diode three words from the abbreviations, Chinese translated as "light-emitting diodes", just as its name implies leds is a kind of can convert electric power into light energy electronic device has diode characteristics. At present different leds can issue between from infrared to different wavelength of light blue, currently emit violet and ultraviolet light emitting diode also had been born. Besides still painted blue leds in blu-ray into a phosphor, will the white white LED.

LED colour and craft:

Making LED different, can produce the material with different energy photons, take this can control LED the wavelength of light emitted, namely spectrum or color. History first LED by use of material is arsenic (As) the gallium arsenide (Ga), its positive PN junction pressure drop (VF, can be understood As light or working voltage) for 1.424 V, issued a light for infrared spectrum. Another common LED material for phosphorus (P) the gallium arsenide (Ga), its positive PN junction 2.261 V, pressure drop out for the light is green.

Based on these two materials, early GaAs1 - xPx LED industrial use can theoretically freely structure, material production from green light range until the infrared wavelengths LED, the subscript any X represents p element the percentage of replacing arsenic elements. Usually by PN junction pressure drop may determine the wavelength of color. LED One typical have GaAs0.6 P0.4 red leds, GaAs0.35 P0.65 of orange light, the P0.86 GaAs0.14 LED wall LED etc. Because manufacturing used gallium, arsenic, phosphorus three elements, so called these three elements glowing LED tube light for. And GaN (gallium nitride) blu-ray leds, the GaP of the green light, LED and GaAs infrared leds luminous tube called two elements. Currently the newest technology is using mixed aluminum (Al), calcium (Ca), indium (In) and nitrogen (N) of the four elements of the four elements AlGaInN LED four elements of materials to make, can cover all visible and partially ultraviolet spectrum.

The luminous intensity:

The luminous intensity of measurement unit have illumination units (+ fc Lux), flux unit (Lumen), luminous intensity lumens unit (candlelight Candlepower)

1CD (candlelight) refers to the object, in complete radiation temperature freezing point, platinum every six one-tenth of the luminous intensity of square centimeter of area. (before refers to 2.2 cm in diameter, quality as the whale oil candle, 75.5 grams per hour 7.78 grams, burning flame height is 4.5 centimeters, along the horizontal luminous intensity)
1L (lumen) refers to 1CD candle shining on the distance to 1 cm, area of 1 square centimeters of plane of the flux.

1Lux (no) refers to the flux 1L evenly distributed in 1 square meters area intensity of illumination.

General active luminous adopts the luminous intensity, such as unit of incandescent lamp, candlelit CD LED etc; Reflection or penetrates the type of object using flux units, such as LCD projector lumens L; And intensity of illumination unit commonly used for photography Lux + fc, etc. Three kinds of measurement unit in the numerical are equivalent, but need to understand from different angles. For example: if a LCD projector brightness (flux) for 1600 lumens, its projection for refraction-such screen size to 60 inches (1 square meters), the intensity of illumination for 1600 + fc, assuming its out of light from the light source 1 cm, mouth to mouth area of the light, the 1 square centimeter luminous intensity of a light for 1600CD mouth. And the real LCD projector caused by the loss, reflection or spread light loss and light membrane uneven distribution, the brightness of the discount, generally have 50% efficiency is very good.

In actual use, light intensity calculation often use easy mapping of data units or change to use.
For the LED display this active luminous generally USES CD/square metre as luminous intensity, and coordinates the view unit for auxiliary parameter, its equivalent to screen the intensity of illumination unit no body; Will this numerical and screen body effective factors, get the whole display area in the best Angle of screen body, assuming the luminous intensity on each pixel LCD body the luminous intensity in the corresponding Spaces, then the constant numerical can be thought also is whole screen body flux. General outdoor LED display must reach the brightness of the 4000CD/square meters in sunlight can only be a more ideal display effect. Common indoor LED, maximum brightness in 700 ~ 2000CD/square metre.

The luminous intensity of single LED to CD, and equipped with unit of perspective, the luminous intensity parameter with LED colour no relationship. The luminous intensity of single pipe from several mCD to 5,000 mCD dollars. LED manufacturers have given in LED the luminous intensity 20mA electricity means shed light, the best Angle and the central position on the biggest points of luminous intensity. When the package LED top lens shapes and LED away from the top position of chip lens decided the light intensity distribution LED Angle. Generally speaking the same LED perspective is larger, the smaller the maximum luminous intensity, but in the whole stereo hemisphere accumulated flux on remains unchanged.

When multiple leds more closely rules, the glow discharge spherical stack with each other, causing the glow of the luminous intensity distribution was homogeneous plane. The luminous intensity in the calculation of the screen, should be based on the LED perspective and LED emissions density, will the biggest point manufacturers to provide the luminous intensity value multiplied by 30% ~ 90% differ, as a single pipe average luminous intensity.

General LED light-emitting life is very long, manufacturers are usually labelled 100,000 hours, actual should also pay attention to the brightness of the attenuation cycle LED, such as most used in automobile taillights UR red tube lit the teens to dozens of hours, half of their original brightness is only. Brightness attenuation cycle and LED production material technology has the very big relations, general economic conditions permit in the case should choose brightness attenuation slower four elements LED.

Match colors, and white balance:

White is red, green, blue press brightness scale, when a mixture of the brightness of light green, red brightness 69 percent for 21%, blue brightness to 10%, the posterity eye feel mixed color is pure white. But red, green, blue LED the color product coordinates for process of reason cannot reach the effect, and coded primary colors including deviation control the brightness of the primary color spectrum, called obtained.

As for full-color LED display on before, in order to achieve the best color, brightness and the lowest cost should be chosen for the luminous intensity three-color 3:6:1 proportion of into roughly LED parts pixels.

White balance required three primary colors in the same tone grey value of synthesized under the pure white still.

Primary colors, gezer:

Unbleached refers to all sorts of color can synthesize basic color. The primary color shade for red, green, blue, below the table that for spectrum for ideal primary-color three vertices wavelength. If the primary is a deviation, the area will reduce synthetic color the triangle, spectral table would narrow, from visual Angle, color not only will have deviation, rich degree decrease.

LED out of red, green and blue line according to its different wavelength characteristics and roughly divided into amaranthine, pure red, orange red, orange, orange, yellow, green and yellow, pure green, green, blue, green, pure blue, blue purple, orange red, green and yellow, violet than pure red, pure green, pure blue is a lot cheaper prices. The three most important primary medium green, because the green occupied white brightness, and be in 69 percent of the center of transverse arrangement color table. So in weigh color purity and price of the relationship between the, green is into consideration on the object.