The principle of infrared detection and infrared thermometer
The essence of infrared detection (infrared radiation detection) in non-destructive testing technology is to use the characteristics of infrared radiation from objects for non-contact infrared temperature recording.
Infrared is an electromagnetic wave with the same essence as radio waves and visible light, with a wavelength between 0.76 and 100 μ m. It can be divided into four categories based on the 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 a widely used electromagnetic wave radiation that exists in nature. It is based on the irregular movement of molecules and atoms generated by any object in a conventional environment, 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.
All objects with temperatures above zero degrees (-273.15K °) will continuously emit infrared radiation into the surrounding space due to their molecular motion. The magnitude and distribution of infrared radiation energy by wavelength of an object are closely related to its surface temperature. By using an infrared radiation detector to convert the power signal radiated by an object into an electrical signal (measuring the infrared energy radiated by the object itself), the surface temperature of the object can be accurately measured, or the spatial distribution of the surface temperature of the scanned object can be simulated one-to-one through the output signal of the imaging device. After processing by the electronic system, it is transmitted to the display screen to obtain a thermal image corresponding to the surface temperature distribution of the object. By using this method, it is possible to achieve remote thermal state image imaging and temperature measurement of targets, and analyze and judge them, which is the basic principle of infrared radiation detection.
Planck's blackbody radiation law: A blackbody is an idealized radiator that absorbs radiation energy of all wavelengths, without any reflection or transmission of energy. Its surface emissivity is 1. Although there is no real blackbody in nature, in order to understand and obtain the distribution law of infrared radiation, it is necessary to choose a suitable model in theoretical research. This is the quantum oscillator model of body cavity radiation proposed by Planck, which derives the law of Planck blackbody radiation, which is the spectral radiance of blackbody represented by wavelength. This is the starting point of all infrared radiation theories, and is therefore abbreviated as the blackbody radiation law.
