What is luminous flux?
Luminous flux is a parameter used to assess the total amount of visible light emitted from an illuminating object, such as a lamp. There is a parameter here called radiant flux, which is similar to optical flux. Radiant flux is a measure of all emitted electromagnetic radiation (including infrared, ultraviolet, and visible light) and is the total amount of objective light. Luminous flux, on the other hand, is the amount of light perceived by the human eye and reflects the sensitivity of the human eye by weighting the luminous effect of each wavelength. Therefore, the luminous flux can be regarded as a polymerization agent for the wavelength intensity of all visible wavelengths except infrared and ultraviolet.
What is luminous efficiency?
Luminous efficiency is the relative sensitivity of the human eye to different wavelengths of light by subjectively judging the brightness of different colors of light. The luminous efficiency should not be considered completely accurate, but it is considered a reference value, as a baseline for experimental purposes, as a parameter that can express the visual sensitivity of the human eye.
Above picture shows:Spectral luminous efficiency of bright vision (black line) and dark vision (green line)
The unit of luminous flux - Lumen
Lumen Lumen (lm) is a unit of luminous flux in the International System of Units (SI), defined by Candela, the SI unit of luminosity, according to the following formula.
1 lm = 1 cdsr
Therefore, when the luminous Angle of the light source is a solid Angle and the luminous flux is one lumen, the luminous intensity is one candela. When the luminous flux is 1 lumen and the light Angle is 1/2 solid Angle, the luminous intensity is 2 Candela.
Conversely, when a point source that emits light in all directions has an intensity of 1 candella, the luminous flux of that source is 4π lumens and 12.56 lumens, because its solid Angle is 4π sphericity.
What is illuminance?
In photometry, illuminance is the total luminous flux of incident light per unit area. That is, the luminous flux represents the total amount of light emitted by the light source, and the illuminance represents the total amount of light received by the object.
The relationship between illuminance and luminous flux is similar to the relationship between irradiance and radiation flux received per unit area, except that illuminance is weighted according to the sensitivity of the human eye to different wavelengths of light and is perceived by the human eye. Represents light intensity.
Illuminance unit - Lux
The SI unit of illumination is Lux (lx). One lux is equal to one lumen per square meter.
1 lx = 1 lm/m 2 = 1 cd·sr/m 2.
