The following terms and definitions are provided by IEC Infrared Systems as a service to our thermal infrared imaging customers. Feel free to call us with any questions you may have about thermal infrared cameras, night vision equipment, or surveillance systems.
α: Greek symbol (pronounced “alpha”), typically used to symbolize absorptance (defined later). Within the limits of Kirchoff’s Law, absorptance is equal to emittance. See Conservation of Energy.
δ: Greek symbol (pronounced “delta”), typically used to indicated a very small quantity. Sometimes the mathematical symbol ∆ (also pronounced “delta”) is used for the same purpose.
ε: Greek symbol (pronounced “epsilon”), typically used to symbolize emittance. Within the limits of Kirchoff’s Law, emittance is equal to absorptance. See Conservation of Energy.
λ: Greek symbol (pronounced “lamda”), typically used to symbolize wavelength (defined later).
μ: Greek symbol (pronounced “mu”) for ‘micro’, meaning 10-6. For example, a micro-meter (also called a ‘micron’) is 10-6 meters.
ρ: Greek symbol (pronounced “row”), typically used to symbolize reflectance, when used in the context of thermal imaging. See Conservation of Energy. Also used (other applications) to symbolize density (mass per unit volume).
σ:Greek symbol (pronounced “sigma”), typically used to represent the Stefan-Boltzmann constant radiometry calculations, the value of which is 5.6704×10−8 W·m-2·K-4, where W is Watts, m is meters, and K is Kelvin.
τ: Greek symbol (pronounced “tau”), typically used to symbolize transmittance. See Conservation of Energy.
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