Describe the principles of infrared thermometers

Technology has developed to the point where it can scan and measure the temperature of surfaces with thermal changes, determine their temperature distribution images, and quickly detect hidden temperature differences. This is the infrared thermometer. Infrared thermometers were first used in the military. In 19, the American TI company developed the world's first infrared scanning reconnaissance system. Later, infrared thermal imaging technology was used in Western countries in aircraft, tanks, warships and other weapons as a thermal aiming system for reconnaissance targets, greatly improving the ability to search and hit targets.

　　Principle of infrared thermometer

　　A black body is an idealized radiator that absorbs radiation energy of all wavelengths, has no energy reflection or transmission, and its surface emissivity is 1. However, almost all real objects in nature are not black bodies. In order to clarify and obtain the law of infrared radiation distribution, a suitable model must be selected in theoretical research. This is the quantized oscillator model of body cavity radiation proposed by Planck, which leads to Planck's law of black body radiation, that is, the black body spectral radiance expressed in wavelength. This is the starting point of all infrared radiation theories, so it is called the black body radiation law. In addition to the radiation wavelength and the temperature of the object, the radiation amount of all real objects is also related to factors such as the type of material constituting the object, the preparation method, the thermal process, the surface state and the environmental conditions. Therefore, in order to make the black body radiation law applicable to all real objects, a proportional coefficient related to the material properties and surface state must be introduced, namely the emissivity. This coefficient indicates the degree of closeness between the thermal radiation of the real object and the black body radiation, and its value is between zero and a value less than 1. According to the radiation law, as long as the emissivity of the material is known, the infrared radiation characteristics of any object can be known. The main factors affecting emissivity are: material type, surface roughness, physical and chemical structure and material thickness.