Radiant energy, irradiance and radiance

Radiant energy (W)： The energy of electromagnetic radiation , Company ：J
radiant flux (Φ)： The radiant energy flowing through an area per unit time , Company W; Radiation flux is a function of wavelength , The total radiation flux should be the sum of the radiation fluxes of each spectral segment or the integral value of the radiation flux .

Radiation flux density （ E）： Radiant energy per unit area per unit time , Company ： W/m²,S Is the area

irradiance （I）： The radiant flux per unit area of the surface of the object being radiated , The unit is W/m²,S Is the area

Emissivity of radiation （M）： The radiant flux per unit area of the surface of an object , The unit is W/m²,S Is the area

irradiance （I） And radiant emittance （M） It is the concept of radiation flux density , however I Radiation received for an object ,M Radiation emitted for an object . They are all wavelength dependent λ of .

Radiance （L）： Suppose there is a radiation source in the shape of a plane , The intensity of outward radiation varies with the direction of radiation , be L Defined as a direction of the radiation source , Unit projected surface , Radiant flux per unit solid angle , namely

L The unit of ：W/(sr·m²)
Solid angle is defined as

here S Is the area of a small bin perpendicular to the radius of the sphere ,R Is the center of the small radiant panel and the upper surface of the sphere S Distance of , That is, the radius of the ball ,
The unit of solid angle is sphericity , Dimensionless . The solid angle of the ball center to the global plane