What is the temperature measuring principle of Fluke infrared thermal imager?

The principle of temperature measurement by Fluke's infrared thermal imager is to passively receive the infrared radiation (heat) of the measured target through the infrared detector in the thermal imager and convert this heat into a visual image with temperature data (objects above absolute zero (-273℃) will emit infrared radiation). Fluke has a unique patent, which is IR-FUSION infrared and visible light fusion technology. Personally, it is quite awesome to photograph the heat map and visible light image at the same time and show them together, which is especially convenient for comparison.