In the use of infrared thermal camera for human body temperature measuring, we often see the words "blackbody calibration", so what is the role of black body in infrared thermal camera? How does it work?

All objects in nature whose temperature is higher than absolute zero (-273.15℃) have the ability to continuously radiate, absorb and emit red radiation. The electromagnetic waves radiated out are different in each band and have a certain spectral distribution. This spectral distribution is related to the properties of the object itself and its temperature, so it is called thermal radiation. In order to study the laws of thermal radiation that do not depend on the physical properties of a substance, physicists have defined an ideal object, a black body, as the standard object for the study of thermal radiation. The so-called blackbody refers to the incident electromagnetic waves are all absorbed, neither reflected, nor penetrating. According to Kirchhoff's radiation law, the ratio of energy to absorption of an object in thermal equilibrium has nothing to do with the property of the object itself, only with the wavelength and temperature. According to Kirchhoff's radiation law, at a certain temperature, a blackbody is the body with the greatest radiation power, with a surface emissivity of 1. Therefore, in infrared thermal imaging, the blackbody is used as a reference, which is equivalent to a zero point. The emissivity is defined as the ratio between the radiation capacity of an object and that of a blackbody at the same temperature.

In the process of using the infrared thermal imager, the data received by the detector is likely to be affected by external factors such as the object's own radiation, air, temperature and so on, resulting in temperature drift. Therefore, the temperature needs to be calibrated. There are two different methods of blackbody calibration, built-in blackbody and external blackbody. In the products of Yoseen Infrared, the built-in blackbody, namely the baffle, eliminates the temperature drift, ensures the temperature measurement accuracy, and at the same time, ensures the measurement temperature will not deteriorate, the picture will not appear obvious noise. At the same time, the external blackbody can be used at a fixed distance to set different temperatures of the blackbody, and the temperature obtained by thermal imager test and the precise temperature value of the black body can be calibrated and fitted with software. In this way, infrared thermal camera can ensure the accuracy of temperature measurement through the law of blackbody radiation.