In 1672, it was discovered that sunlight (white light) is composed of various colors of light, and Newton concluded that monochromatic light has simpler properties than white light. By using a spectroscopic prism, sunlight (white light) is decomposed into monochromatic light of various colors such as red, orange, yellow, green, cyan, blue, and purple. In 1800, British physicist F W. When Huxle studied various colors of light from the perspective of heat, he discovered infrared radiation. When studying the heat of various colors of light, he intentionally blocked the only window of the darkroom with a dark board and opened a rectangular hole on the board, inside which he installed a splitter prism. When sunlight passes through a prism, it is decomposed into colored light bands, and a thermometer is used to measure the heat contained in different colors in the light bands. In order to compare with the ambient temperature, Herschel used several thermometers placed near the colored light band for comparison to measure the ambient temperature. In the experiment, he stumbled upon a strange phenomenon: a thermometer placed outside the red light band had a higher reading than other indoor temperatures. After repeated experiments, the so-called high-temperature zone with the most heat is always located outside the red light at the extreme edge of the light band. So he announced that in addition to visible light, there is also an invisible "hot line" in the radiation emitted by the sun, which is located outside the red light and is called infrared. Infrared is an electromagnetic wave with the same essence as radio waves and visible light. The discovery of infrared is a leap in human understanding of nature, opening up a new and broad path for the research, utilization, and development of infrared technology.

The wavelength of infrared is between 0.76-100 μ M can be divided into four categories based on wavelength range: near-infrared, mid-infrared, far-infrared, and extremely far-infrared. Its position in the continuous spectrum of electromagnetic waves is in the area between radio waves and visible light. Infrared radiation is the most widespread type of electromagnetic wave radiation that exists in nature. It is based on the fact that any object in a conventional environment will generate its own molecules and atoms in irregular motion, constantly radiating thermal infrared energy. The more intense the movement of molecules and atoms, the greater the radiation energy, and vice versa, the smaller the radiation energy.