HGH infrared - Infrared blackbody radiation

    The infrared radiation is the electromagnetic radiation where wavelengths are between 700 nanometres and 1 millimetre. Thus, it is located between the red limit of visible spectrum and the shortest microwaves. All bodies at a temperature above the absolute zero emit infrared radiation.

    However, at any given temperature and wavelength, there is a maximum amount of radiation that any surface can emit. If a surface emits this maximum amount of radiation, it is known as a blackbody.

    Usual objects are not blackbodies. They do not absorb 100% of the incident energy and usually select the absorbed wavelengths. Consequently, they cannot re-emit all the incident energy. The ratio between the emitted energy and the incident energy is called emissivity. This ratio sometimes depends on wavelength.

    Theoretically, a blackbody has an emissivity of 1.0 at all temperatures and wavelengths.

    A blackbody is compared to an idealized radiator that absorbs all incident energy upon its surface, regardless of direction and wavelength. It re-emits this electromagnetic radiation with 100 % efficiency according to Planck's law (see Planck's curve). The emission curves only depend on the temperature of the blackbody.

Planck's law:

The Wien law gives the wavelength (in microns) corresponding to the maximum spectral radiance of a blackbody at given temperature T (in Kelvin):

Wien's law:

The wavelength of maximal infrared radiation decreases if the blackbody temperature increases.

The total amount of emitted radiation (in Watt) of a blackbody is given by the Stefan-Boltzman law. It also only depends on the blackbody temperature T (in Kelvin):

Practically, an infrared reference source is designed to have the highest emissivity as possible (>0.9) whatever the wavelength. This source is usually called blackbody.

All infrared sensors for thermography (pyrometers, thermal cameras…) convert thermal radiation received into an electrical signal to give a temperature measurement. These sensors need to be calibrated with a blackbody infrared reference source in order to ensure the temperature measurement accuracy.

test metrology :	blackbody \| differential blackbody \| high temperature blackbody \| extended blackbody \| Low temperature blackbody \| vacuum blackbodies \| infrared radiation \| infrared collimator
	\| optronic maintenance \| Infrared Focal Plane Array detectors \| infrared radiometer \| infrared imaging spectroradiometer
thermography for industry :	scanner \| scanner for thermography \| kiln scanner for cement \| scanner float glass \| scanner for industry \| infrared camera \| infrared thermal imager \| system for tunnel inspection
	pyrometric Camera \| electrical cable overheating \| water infiltration detection
optronic for security :	security perimeter control \| infrared panoramic surveillance
optronic engineering :	specific collimator \| customised blackbodies \| specific optronic design

Blackbody infrared radiation