What is the role of blackbody in infrared thermometers
(1) An object that completely absorbs external radiation of any wavelength without any reflection under any conditions.
(2) An object with an absorption ratio of 1
(3) An object that absorbs all radiation of any wavelength incident at any temperature. Any object has the ability to continuously radiate, absorb, and emit electromagnetic waves. The radiated electromagnetic waves are different in various bands, which means they have a certain spectral distribution. This spectral distribution is related to the characteristics of the object itself and its temperature, hence it is called thermal radiation. In order to study the thermal radiation law that does not depend on the specific physical properties of matter, physicists have defined an ideal object - a black body, as the standard object for thermal radiation research. The so-called blackbody refers to the fact that all incident electromagnetic waves are absorbed, neither reflected nor transmitted (of course, blackbody radiation still needs to radiate outward).
Kirchhoff's radiation law states that the ratio of energy radiated by an object in a thermal equilibrium state to its absorption rate is not related to the physical properties of the object itself, but only to its wavelength and temperature. According to Kirchhoff's radiation law, at a certain temperature, a blackbody must be an object with large radiation power, which can be called a complete radiator. The electromagnetic waves emitted by different substances in infrared thermal imaging never intersect, and this blackbody is only a reference object, equivalent to a zero point. But there is no such ideal blackbody in the real world, so what is used to depict this difference? For any wavelength, the emissivity is defined as the ratio of the radiation energy of a real object to the radiation energy of a blackbody at the same temperature within a small wavelength interval of that wavelength. Obviously, the emissivity is a positive number between 0 and 1, and generally depends on material properties, environmental factors, and observation conditions. If the emissivity is independent of wavelength, the object can be called a gray body, otherwise it is called a selective radiator.
Infrared thermal imagers may be affected by external factors during long-term use, resulting in errors, so blackbody calibration is necessary
