While thermal cameras have existed since the 1960s, they became widely known through Hollywood in the late 1980s. Since then, there has always been an interest in how they work, and it’s important to clarify many misconceptions as well as highlight their valuable yet often unknown capabilities.
Thermal cameras operate differently from conventional cameras. While daylight cameras and the human eye work on the same basic principle: visible light energy hits something, bounces off it, a detector receives the reflected light, and then turns it into an image.
Thermal sensors produce images from heat, not visible light. Heat (also known as infrared or thermal energy) and light are both parts of the electromagnetic spectrum, but a camera that can detect visible light won’t see thermal energy and vice versa. Thermal cameras capture infrared energy and use the data to create images through video outputs.
Inside a thermal camera, there’s a lens, a thermal sensor, processing electronics, and a mechanical housing. The lens focuses infrared energy onto the sensor. The sensor can have various pixel configurations, ranging from 80 × 60 to 1280 × 1024 pixels or more, determining the camera’s resolution.
These resolutions are low compared to visible light cameras because thermal detectors need to sense energy with much larger wavelengths than visible light, requiring each sensor element to be significantly larger. As a result, a thermal camera usually has a much lower resolution (fewer pixels) than visible sensors of the same mechanical size.
Important specifications to consider when choosing a thermal camera include resolution, range, field of view, focus, thermal sensitivity, and spectral range.
What can thermal cameras detect?
The heat detected by an infrared camera can be measured with great precision, enabling a wide variety of applications. A Teledyne FLIR thermal camera can detect minimal differences in heat, as small as 0.01°C, and display them in shades of gray or with different color palettes.
Everything we encounter in our daily lives emits thermal energy, even ice. The hotter something is, the more thermal energy it emits. This emitted thermal energy is called “heat signature.” When two adjacent objects have even slightly different heat signatures, they are clearly displayed to a thermal sensor regardless of lighting conditions. This allows thermal cameras to see in complete darkness or in smoke-filled environments.
Thermal cameras can detect many things that our eyes or conventional cameras cannot, as well as other common materials, such as glass, which do not allow the passage of thermal radiation at certain wavelengths (specifically between 7 and 14 μm).
What are thermal cameras used for?
The potential uses of thermal cameras are nearly limitless. Originally developed for surveillance and military operations, thermal cameras are now widely used for industrial inspections, early fire detection, autonomous vehicles, skin temperature measurement, scientific research, and much more.
