The LED brightness metering

The same with traditional light sources, LED light source of optical measurement units are uniform. In order for you the reader to understand and easy to use, the following introduce the relevant knowledge briefly:
1、luminous flux
Luminous flux refers to the light source in the unit of time given the amount of light, that radiated power can be felt by the human eye that part of radiation energy. It is equal to unit time of a band of radiation energy and the band see the rate of relative depending on the product. As the human eye to different wavelengths of light, see different rates depending on the relative, so that different wavelengths of light radiated power are equal, not equal luminous flux. The symbol for luminous flux Φ, unit lumen (Lm).
The basis of spectral radiant flux Φ (λ), so can be derived flux formula:
  Φ=Km   Φ（λ）gV（λ）dλ
In the formula, V (λ) - relative spectral luminous efficiency; Km-radiation spectrum of light depending on the performance of the maximum, the unit for Lm / W. Measured in 1977 by the International Committee to determine Km values 683Lm / W (λm = 555nm).
2、Luminous intensity
Luminous intensity is defined as per unit area per unit time through the light energy, energy and frequency proportional to the intensity of their sum (ie integral) can also be understood as the light source in a given direction, the luminous intensity I is the light source solid angle in the direction of the luminous flux dΦ yuan in transfer divided by the solid angle element dΩ of the business
The unit of luminous intensity is the candela (cd), 1cd = 1Lm/1sr. Space in all directions, and is the flux of light intensity.
3、light brightness
We are in testing and evaluation of brightness LED chips LED light radiation safety of the process, commonly used imaging method can be used for the test chip micro-imaging to measure. Brightness is the source of a light-emitting surface brightness at L, is the surface element dS in a given direction of the luminous intensity divided by the surface element in a given direction perpendicular to the plane of orthographic projection area of the business
Brightness of the unit is the candela per square meter (cd/m2). When the light is perpendicular to the surface and measurements, then cosθ = 1.
4、Light illumination
Light Illumination refers to the object is illuminated the extent received by use of luminous flux per unit area expressed. Illuminance and light source, the illuminated surface and the location of light in space, size, and light sources and light intensity is proportional to the angle of Yu Xuan, but with the light source to the illuminated surface is inversely proportional to the square of the distance. A point on the surface of the illumination E is the incident surface elements that contains the point on the luminous flux dΦ divided by the surface area dS of the yuan business.
The unit of Lux (LX), 1LX = 1Lm/m2.
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