Luminous flux definition: The number light that emitted by 1 luminous intensity light source in a solid angle.
Luminous flux refers to the human eye can feel the radiation power, which is equal to the radiation energy multiplied by the relative visible rate in unit time. Different light the wavelength relative visible rate is different by human eye, so the different wavelengths even radiate same power, the luminous flux not the same.
The unit of luminous flux is “lumens”. Luminous flux symbol by Φ, in theory, the unit is equivalent to the electrical unit watt. “Lumens” by standard light source and the unit of measure symbol: lm.
1. Luminous flux means light energy arrival, departure, or through the surface per unit time.
2. Luminous flux is the ratio that the diode emit light.
The formula expression of the light flux:
In formula:
K: photosensitivity, sensitivity (analogy: the sensitivity of the film), the human eye percept for color K = 683.002 lm / W. K value make the luminous flux radiated power units to be harmonized.
λ: wavelength, in fact the human eye only react on the wavelength of visible light from 380nm to 780nm, customary the lightwave less than 380 nm is called UV (Ultraviolet, referred to as UV), higher than 780 nm of the light waves known as infrared (IR).
V (λ): referred to as the relative spectral sensitivity curve of the human eye, also called the viewing function curve, it is the sum of the human eye testing experience, which describes the strength of the reaction of the human eye to light with different wavelengths.
Sources: http://www.lednews.org/whats-luminous-flux-definition/
