1. The luminous flux of LED light-emitting diodes (lm)
Since the human eye has different sensitivity to electromagnetic waves of different wavelengths, we cannot directly use the radiant power or radiant flux of the light source to measure light energy. We must use the unit based on the human eye's perception of light --- luminous flux. measure. Luminous flux is expressed by symbols, and the unit is lumens <lm).
2. The luminous intensity of LED light-emitting diodes (cd)
Luminous flux refers to the total light energy emitted by a light source into the surrounding space. The spatial distribution of the luminous flux emitted by different light sources is different. The unit of luminous intensity is candela, and the symbol is cd, which represents the luminous flux emitted by the light source in a certain unit sphere solid angle (the angle formed by the surface of the object to the point light source). 1cd=1lm/1sr (sr: unit of steradian of solid angle).
3. The brightness of LED light-emitting diodes (cd/m2)
Brightness refers to the intensity of light emitted from an object seen by the eyes from a certain direction. The unit is candela square meter [cd/m2], and the symbol is L, which indicates the luminous flux of the luminous body in a unit solid angle unit plane in a specific direction, which is equal to the luminous intensity of 1 candela on the surface of 1 square meter.
4. The color temperature of LED light-emitting diodes (Color Temperature)
When the color of the light emitted by the light source is the same as the color radiated by the black body at a certain temperature, the temperature of the black body is called the color temperature of the light source, expressed in absolute temperature K (Kelvin, Kelvin = Celsius t+273.15).
5. Color rendering property of LED light-emitting diodes
In principle, artificial light should be the same as natural light, so that the human eye can correctly distinguish the color of things. Of course, this depends on the location and purpose of the lighting.
The degree to which the light source presents the color of an object is called color rendering. Usually called "color rendering index" (Ra). Color rendering refers to the relationship between the true color of a thing (its own color) and the color displayed under a certain standard light source. The Ra value is determined by comparing the 8 test colors defined in the DIN6169 standard under the standard light source and the tested light source. The smaller the color difference, the better the color rendering of the tested light source.
A light source with an Ra value of 100 means that the color of things displayed under its light is the same as that under a standard light source.
