辐射测量是量化和测量电磁辐射基本属性的科学和技术。这包括可见光、红外线和紫外线，以及无线电波和X射线，例如。与光度测量不同的是，辐射的可见度和它的感知亮度在这个领域不感兴趣；我们处理的是纯粹的物理量，不涉及人眼的属性。
辐射测量提供精确定义的数量，作为进一步工作的基础。各种辐射测量仪器已经被开发出来用于测量这些量。
辐射测量的数量
辐射测量学的发展已经导致了一个相当系统和定义明确的辐射测量量系统。为此，一些使用的术语和它们的精确定义不得不被修改。然而，旧的术语和偏离的含义仍然普遍存在，不仅是在旧的文献中，而且还因为许多主要从事光学和激光技术的专业人员，例如，而不是专门从事辐射测量的专业人员，没有（或没有完全）采用建议的术语和定义。下表还具体说明了特别用于光学和激光技术的此类替代术语：
technology:
| Quantity | Symbol | Alternative term | Units | Remarks |
|---|---|---|---|---|
| radiant energy | ?e | optical energy, pulse energy | joule (J) | total radiated energy, e.g. of a light pulse |
| radiant energy density | ?e | optical energy density | J/m3 | applied e.g. to blackbody radiation |
| radiant flux | Φe | radiant power, optical power | W = J/s | radiant energy per unit time |
| spectral flux | or | optical power spectral density | W/Hz or W/nm | radiant flux per unit frequency or wavelength |
| radiant intensity | ?e,\Omega | W/sr | radiant flux per unit solid angle | |
| spectral intensity | or | W sr?1 Hz?1 or W sr?1 nm?1 | radiant intensity per unit frequency or wavelength | |
| radiance | ?e,\Omega | brightness (not recommended) | W sr?1 m?2 | radiant flux per unit area and unit solid angle |
| spectral radiance | or | W sr?1 m?2 Hz?1 or W sr?1 m?2 nm?1 | radiance per unit frequency or wavelength | |
| irradiance | ?e | flux density | W/m2 | received radiant flux on a surface |
| spectral irradiance | or | W m?2 Hz?1 or W m?2 nm?1 | irradiance per unit frequency or wavelength | |
| radiosity | ?e | W/m2 | radiant flux per unit area, leaving a surface (by emission, reflection or transmission) | |
| spectral radiosity | or | W m?2 Hz?1 or W m?2 nm?1 | radiosity per unit frequency or wavelength | |
| radiant exitance | ?e | W/m2 | like radiosity, but counting only emitted radiation | |
| spectral exitance | or | W m?2 Hz?1 or W m?2 nm?1 | radiant exitance per unit frequency or wavelength | |
| radiant exposure | ?e | J/m2 | received radiant energy per unit area, equal to the time-integrated irradiance | |
| spectral exposure | or | J m?2 Hz?1 or J m?2 nm?1 | radiant exposure per unit frequency or wavelength | |
| hemispherical emissivity | ? | radiant exitance relative to that of a blackbody at the same temperature | ||
| hemispherical absorptance | ? | fraction of absorbed radiant flux on a surface | ||
| hemispherical reflectance | ? | fraction of reflected radiant flux on a surface | ||
| hemispherical transmittance | ? | fraction of transmitted radiant flux on a surface | ||
| hemispherical attenuation coefficient | ? | m?1 | fraction of absorbed or scattered radiant flux per unit length |
The
