synonymlight intensity(Light intensity) generally refers to luminous intensity
Luminous intensity(Luminous intensity), inPhotometryChinese abbreviationlight intensityorluminosity。Used to indicatelight sourceWithin unit solid angle in given directionLuminous fluxPhysical quantity of,International unitbyCandela, symbol: cd, formerly known as candlelight or candlelight.
The definition of luminous intensity takes into account human visual factors and optical characteristics, and is based on human vision.
Confused, in optics,light intensityUsually refers toRadiant power, because the human eyeRelative visibilityDifferent, so when the radiation power of light of different wavelengths is equal, its luminous flux is not equal.
In 1948, the 9th International Metrology Conference decided to use an absolute blackbody radiator as the standard, and gave the luminous intensity the current name:candela(cd, Candela).
Definition of the 13th International Conference on Metrology in 1967 (now obsolete):pressureAt platinum freezing point temperatureBlackbody1/600000 square meters of surface in the vertical direction. "
In 1979, the 16th International Conference on Metrology adopted a resolution abolishing the above definition and stipulating that the new definition is:
"Candela is the luminous intensity in a given direction of a monochromatic radiation source emitting light of 540 x 10 ^ 12Hz frequency, and the radiation intensity in that direction is 1/683 W/sr."
Physical expression of luminous intensity
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The luminous intensity of the illuminant in a given direction isSolid angleYuan dΩInternally transmittedLuminous fluxdΦThe quotient obtained by dividing this solid angle element is the luminous flux per unit solid angle. The formula is:
The unit is candela (cd), the unit of luminous flux is lumen (lm), and the unit of solid angle is sr, so 1cd=1 lm/sr.
