Thermal imaging cameras are cameras with sensors that are sensitive to heat rather than visible light. They record the heat given off by any object, person or animal and convert and reproduce it as a visual image called a thermogram. Technically, radiated heat and light are the same type of electromagnetic energy; the only difference is that heat energy is at a lower frequency than our eyes are capable of seeing. The lowest frequency of visible light is seen as the colour red, so heat energy in the frequency range just lower than red is called ‘infra red’. It’s invisible to human eyes but not to thermal imaging cameras. Originally developed for military use, modern thermal imaging cameras are now used in a huge range of situations where they prove invaluable. Here are just five of the many important uses to which thermal imaging cameras are put.
- Night rescue missions – Thermal cameras have enabled rescue teams to save countless lives of people stranded on a mountain side or lost at sea at night. Requiring no visible light, thermal cameras on board rescue helicopters can find people in situations where visually detecting them would be impossible. They’re not so useful for locating dead bodies, however, as a dead body will cool and become the same temperature as its surroundings, meaning it won’t stand out against the background.
- Criminal detection – Even in complete darkness, criminals being pursued by police can be betrayed by their own body heat and easily be seen by thermal cameras, especially from police helicopters. A celebrated case was the apprehension of the Boston Marathon bomber. He was detected by police using a thermal camera from a helicopter. Despite hiding underneath a tarpaulin that was covering a small boat parked in someone’s driveway, his body heat gave away his location.
- Fire Services – Fire services worldwide also have important uses for thermal imaging cameras. Thick smoke inside a burning building obscures light but has no effect on heat. Normal cameras are useless in that situation, so fire fighters can use thermal cameras to see through thick smoke, find people inside and detect and cool down dangerous hot spots that could easily erupt in flames.
- Disease detection and control – A more recent use of thermal imaging cameras is to limit the spread of infectious diseases across international borders. Thermal imaging cameras are used to detect raised body temperatures of people entering countries via airports or other ports and border crossings during epidemics of serious infectious diseases. It’s done unobtrusively and people are unaware that their body temperature has been checked. This practice was implemented on a large scale during the recent ebola crisis on travellers arriving from some African countries where the disease had taken hold. Of course, the camera can’t tell if someone with a raised temperature has ebola or just a harmless cold, so if a thermal camera detected a raised body temperature, the traveller would be stopped and medically checked for other tell-tale symptoms of the disease.
- Heating Efficiency – One very important use of thermal imaging cameras is to check the heating efficiency of homes, offices and other buildings. Brightly coloured areas of the image taken by the thermal camera can pinpoint areas where heat is escaping from the building. It enables house and other property owners to better insulate their buildings at those weak points to reduce heat loss and inflated energy costs.
Those five important uses of thermal imaging cameras represent just the tip of the iceberg. These specialised cameras have many more uses in industry and elsewhere, such as for checking the correct and efficient working of machinery and for detecting potential problems so they can be addressed before they become real problems. As technology advances, the cameras will become ever more sensitive and useful in an increasingly wide range of situations.