Refers to the light-emitting surface luminescence intensity of physical quantities called luminance, luminance, physics in L said, the unit of candela per square meter or square candle CD/m2. Brightness is one of the important indicators to measure plasma display luminous intensity, for plasma, plasma for its high brightness means higher anti-interference ability of the working environment. Plasma since the structure of the lighting units are identical, the screen brightness is very uniform, no bright area and dark area. Generally, the brightness of the plasma are above 500 CD/m2, clear gorgeous images, some high-grade plasma brightness can reach more than 1000 CD/m2.
Brightness is to express the degree of shiny surface bright, refers to the surface in the direction of the luminous intensity and vertical and specify the ratio of the direction of the light-emitting surface area, the unit is candela per square meter. For a diffuse scattering surface, although different luminous intensity and luminous flux in all directions, but the brightness of all directions are equal. The TV screen is similar to the diffuse scattering surface, so images from all directions, all have the same brightness.
Different objects have different reflection coefficient to light
The intensity of light can be used according to the amount of light on the plane to measure, this is called incident light (inci - dent light) or the intensity of illumination (illuminance). If use from reflecting to the amount of light in the eye, to measure the intensity of the light, this light is called the reflected light (the reflection light) or luminance (brightness). For example, generally white paper about 20% the amount of absorption of incident light, the amount of reflected light is 80%; Black paper only reflects 3% of the amount of incident light. So, white and black paper on the brightness difference is very big.
Brightness and intensity of illumination
Brightness and the relationship between the intensity of illumination as shown in figure 6-2 (a), is the most commonly used unit of illuminance foot-candle (footcandle). 1 foot candle is a foot away from standard candle of the luminous flux plane to accept a square foot. If the metric unit, with rice as standard, intensity of illumination is candle (metrecandle) rice, which is 1 m standard candle candle is distance meter far illumination on each square meter area. 1 meter candle candle is equal to 0.0929 ft. From figure 6 and 2, it is easy to understand the relationship between the brightness and intensity of illumination, the relationship is: L = R * E] [formula 6-1 type of L for brightness, R for the reflection coefficient, E for illumination. Therefore, when we know the surface of an object on the surface of the reflection coefficient and the intensity of illumination, its brightness can be calculated.
Brightness also has several units of measurement
Brightness also has several units of measurement. The brightness of the unit is defined with an idealized standard state (as shown in figure 6-2 b). With a standard candle as a light source, in a radius of 1 meter of the center of the sphere. Assume that all light this candle will be evenly spread it falls on the sphere surface all the light on the surface area of one square meter for a lumen (lumen). Practical applications, the brightness of the unit with lumens is too small, so usually take its units -- ten times as much as Millie lambert (millilambert). Unit is slightly bigger than a fine long hair Lambert foot Lambert (footlambert), 1 mL "lambert is equal to 0.929 ft. British standard foot lambert is to use number of candle light from the light source to the footage and surface deflection of the surface of the rules. In some countries, is the widespread use of metric units, is based on fine long hair lambert [1 milli lambert lambert (mL) = 0.929 feet (ftL) = 3.183 candle/m2 (c/m2) = 10 apostilb (apostilbs)]. The brightness of the units are: candela per square meter (namely nita, Nit = 1 CD/m2), etc.