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LED Lens Terminology

Views: Date: 2015-7-14

1.LEDs Terminology

1.Luminous Flux
Symbol Φ
Unit Lm(Lumen) 
Description Light source shot in total amount per second.
Formula 
2.Illuminance
Symbol
Unit Lm/m²(Lux)
Description Illuminance means in one lighted area, the density of the luminous flux
on a surface, per unit area.(Illuminance is inverse ratio to the square of
distance from one illuminant. And it expresses the brightness of one place.)
Formula Illuminance(E)=Luminous Flux(Φ) / Area (A)
3.Luminous Intensity
Symbol I
Unit Cd(Candela)
Description The Luminous Flux in certain direction of light source of solid angle(Ω)
Formula Luminous Intensity(I)=Luminous Flux(Φ) / Solid angle (Ω)
4.Luminance
Symbol L
Unit Cd/m²
Description Luminance means the luminous intensity(I) per unit of one illuminated area
which light radiates or passes through in a given direction.
Formula Luminance(L)=Luminous Intensity(I) / Area (A)
2.Definition of Beam Angle