Like many security and surveillance technologies, thermal imaging was first introduced through military applications, where negating the need for light in order to identify potential threats had clear operational benefit for field maneuvers. What might be surprising
Today, thermal cameras are widely used in oil and gas, marine, utilities, high security and critical infrastructure settings to support everything from process safety to offshore threat detection. But what exactly are thermal cameras? Why are they popular?
Some people use thermal cameras and Infrared (IR) cameras interchangeably – are they correct in doing so?
Not really, but there is a good reason for the confusion. Thermal cameras do use radiation from the infrared spectrum. In that sense they are ‘technically’ IR cameras. But the range we are talking about is the very far end of that spectrum – well beyond the frequency range of ‘near infrared’ i.e. the area of the spectrum where most IR cameras operate.
The IR range is actually much closer to visible light on the spectrum. As a rough guide, visible light (what the human eye can easily see) spans from about 450nm to 750nm, with near infrared kicking in at approximately 700nm and going up to around 1000nm. By comparison, thermal cameras operate at wavelengths up to 14,000nm.
If thermal cameras are more expensive than IR LED cameras which can also operate in complete darkness, why use thermal imaging?
It depends on the application but in terms of threat detection – distance is probably the single biggest reason. Because they operate by measuring emissivity rather than capturing reflected light, thermal cameras can detect objects at much greater distances.
Active illumination with cameras fitted with IR LED illumination only have a limited operational range typically out to about 200m and very much depend on the reflectance of the target. As the distance increases and the camera field of view is reduced or zoomed in, the light attenuation increases and a more powerful illuminator is required, so it becomes a law of diminishing returns. On the other hand, thermal cameras passively operate in the MWIR and LWIR bands with their operational range only limited by the lens and sensitivity of the camera.
It’s also important to mention LED degradation. In as little as 5 years, LED light sources will typically degrade by approximately 30% which can significantly impact on camera capability and image quality. Thermal cameras will require a more significant initial outlay but their lifespan is much longer.