Background Temperature, Instrument - The apparent temperature of the radiant energy impinging on an object that is reflected off the object and enters the instrument. Originates from the scene behind and surrounding the instrument, as viewed from the target. The reflection of this background appears in the image and affects temperature measurements. Good quality quantitative thermal sensing and imaging instruments provide a means for correcting measurements for this reflection.

Background Temperature, Target - Apparent ambient temperature of the scene behind and surrounding the target, as viewed from the instrument. When the FOV of a point sensing instrument is larger than the target, the target background temperature will affect the instrument reading. Also called surroundings temperature or foreground temperature.

Blackbody, Blackbody Radiator - A perfect radiator, one that radiates the maximum number of photons in a unit time from a unit area in a specified spectral interval into a hemisphere that any body in thermodynamic equilibrium at the same temperature can radiate. It follows that a blackbody absorbs all radiant energy impinging on it and reflects and transmits none; thus a surface with emissivity of unity (1.0).

More information on blackbody radiation.

More information on blackbody types and emissivity.

Blackbody Curves - Plots of radiant power spectral exitance (W/m²/mm) vs. wavelength for various temperatures according to the Planck equation. These curves show the maximum amount of energy at any given wavelength that can be radiated by an object due solely to its temperature. Also called Planck curves.

Bolometer, Infrared [Micro-Bolometer] - A type of thermal detector commonly used in uncooled radiometers.