Please see <this explanation> of the electromagnetic spectrum before reading this post.
Thermal optics, also known as thermal imaging systems, work by detecting the infrared radiation emitted by objects and converting it into a visible image. This is accomplished through the use of a specialized camera that is able to detect the heat signatures given off by objects, even in complete darkness. Thermal imaging systems typically use a lens to focus the infrared radiation emitted by objects onto a detector array, which is made up of a large number of tiny sensors. Each sensor detects the amount of heat energy emitted by the object in its field of view and converts it into an electrical signal. These signals are then processed by a computer, which assigns a color or shade of gray to each pixel in the image based on the amount of heat detected.
In general, warmer objects emit more infrared radiation than cooler objects, so the resulting image will show variations in temperature as differences in color or shades of gray. This can be useful in a variety of applications, such as military and law enforcement operations, and search/rescue efforts, where the ability to detect heat signatures can be critical for identifying potential threats or hazards.