How Do Thermal Image Cameras Work?

To understand how thermal imaging cameras work, it is essential to understand how the human eye works. The human eye operates by virtue of seeing all the objects illuminated by the sun or any other source of light. The contrast between objects illuminated by the sources of light enables the human eye to distinguish between two objects. In contrast, thermal imaging cameras work by seeing the heat energy that the objects in the frame emit. As mentioned earlier, all objects (whether living or not) have heat energy. Thermal imaging cameras detect this energy and provide an image accordingly. The ability to detect infrared energy makes these cameras highly accurate. This is so even in conditions of complete darkness.
 
Unlike digital cameras that work by using reflected light, thermal cameras work by seeing heat. As such, the images these cameras produce will be very different from those produced by regular cameras. It is evident that each object will emit varying levels of infrared energy or heat. Thus, thermal imaging cameras have the ability to convert the temperature of objects into shades of grey. These shades will typically be lighter or darker than the background. For instance, the picture of a person will be lighter than the background on a cold day. This is because the person is hotter than the background. Similarly, on a hot day, a person will appear to be darker than the background. This is because the person is cooler than the background