Radiant Energy (光能). An amount of light energy can be thought ofas the total energy of a collections ofphotons (光子), the quantity is referred to asradiant energy. Radiant energy is denoted by Q andmeasured in Joule (J)RadiantenergyQ
Radiant Energy (光能) • An amount of light energy can be thought of as the total energy of a collections of photons (光子), the quantity is referred to as radiant energy. • Radiant energy is denoted by Q and measured in Joule (J)(焦耳)
Radiant Flux (光通量). Radiant energy does not stay fixed in oneposition, but moves Radiant Flux describes:- The flow of energy through an area per unit time- To represent radiant energy in motion, we havedQΦ=dt- Measure in watt (W)(瓦特)- 1 watt (W) is equivalent tooneJoule(焦耳）persecondRadiantflux p
Radiant Flux (光通量) • Radiant energy does not stay fixed in one position, but moves • Radiant Flux describes: – The flow of energy through an area per unit time – To represent radiant energy in motion, we have – Measure in watt (W)(瓦特) – 1 watt (W) is equivalent to one Joule(焦耳) per second dQ dt
(辉度)Irradiance. To describe interactions of radiantenergy and a surface- We represent the incoming radiant flux perunitsurfacearea(单位面积的光通量)asddEdA2measuredinW/mIrradianceE
Irradiance （辉度） • To describe interactions of radiant energy and a surface – We represent the incoming radiant flux per unit surface area(单位面积的光通量) as – measured in W/m d E dA 2
（发光强度）Intensity·Radiant Flux（光通量）through a pointcan't be described by irradiance, since apoint consists of Zero area.: So we use Intensity, described as:- Radiant flux with respected to solid angled@doIntensity I
Intensity （发光强度） • Radiant Flux （光通量） through a point can’t be described by irradiance, since a point consists of Zero area. • So we use Intensity, described as: – Radiant flux with respected to solid angle d I d
（光亮度）Radiance. Radiant flux is always described in terms ofboth surface area and solid angle The measure of flux entering or leavinga surface per solid angleper unit foreshorteneddosurface area is calledRadiance which can bemeasured bydAW /(sr ·m2)Radiance L
Radiance （光亮度） • Radiant flux is always described in terms of both surface area and solid angle • The measure of flux entering or leaving a surface per solid angle per unit foreshortened surface area is called Radiance which can be measured by 2 W sr m /( )