What is Thermal Imaging? A Beginner's Guide

What is Thermal Imaging?

Thermal imaging is a field of photography, taken from thermography: the study of infrared (IR) radiation. First discovered by Sir William Herschel, infrared is part of the electromagnetic spectrum with wavelengths ranging between 9 and 14 micrometers (µm) or 9000 and 14000 nanometres. (1 centimetre is equivalent to 10 000 micrometers) Herschel’s original experiment was to find the temperatures of different colours within the visible light spectrum. He used a prism to split white light into all its many colours and noticed that the red end was noticeably hotter than the violet end. He then measured the temperature below the red light and found that section to be significantly hotter than all the visible light. From this he made the breakthrough discovery that there were other types of radiation that we couldn’t see. He named this new, hot radiation infrared, where infra is derived from the Latin for “below”.

How we use Thermal Imaging

When we come round and service your equipment or tell you what’s wrong with your horse or even where those pesky mice are hiding, we are looking at thermograms which are effectively images of IR radiation, colour coded with visible light so that we can see the patterns. You may think to yourself that that sounds easy but you’d be surprised! As a thermographer we must deal with a lot of elements before we can even start telling you what the problem is. The most complicated element is emissivity. Emissivity is the reciprocal reflectance of an object, which, put simply, means that the higher the emissivity, the less IR radiation that object reflects and so the truer the values presented on the thermal imaging camera. When there is a low emissivity the object appears hotter than it is as it not only shows the emission of IR radiation but the reflection too and so these objects appear to be much hotter than they really are. Therefore, it’s best to call out an expert like us!