Infrared thermometer consists of optical system, photodetector, signal amplifier, signal processing, display output and other parts. The optical system concentrates the target's infrared radiation energy within its field of view, the size of which is determined by the thermometer's optics and their location. The infrared energy is focused on a photodetector and converted into a corresponding electrical signal. The signal is converted into the temperature value of the measured target after being corrected by the amplifier and signal processing circuit according to the internal treatment algorithm of the instrument and the target emissivity.
In nature, all objects with a temperature above absolute zero are constantly emitting infrared radiant energy into the surrounding space. The magnitude of the infrared radiation energy of an object and its distribution by wavelength are very closely related to the surface temperature of the object. Therefore, by measuring the infrared energy radiated by the object itself, its surface temperature can be accurately determined, which is the objective basis for infrared radiation temperature measurement.