There are many considerations when choosing the operating waveband of a thermal infrared camera.

An important parameter to consider is the estimated temperature range of the object to be measured. The Planck emission curve dictates that solid objects over approximately 150 °C will have their maximum emission in the midwave region of the IR spectrum, with fainter signal in the LW. Conversaly, solid objects closer to room temperature will almost exclusively emit in the longwave region of the IR spectrum, with only faint emissions in the MW region. Nevertheless, a MW camera can still be used for measuring an object close to room temperature with an appropriate exposure time. And in the same way, a LW camera can still be used to measure hot solid targets.

Care must also be given to the spectral requirements of the envisioned application. Objects under measurement can feature varying spectral emission and absorption behaviours (referred to as signature) that can be better matched with a camera’s spectral range. Combustion, for example, shows varying signal across the MW spectral range, and minerals can have varying signature in the LW that can help in distinguishing them. Prior knowledge of the spectral signatures of the target material of interest is essential when choosing the spectral range of an infrared imager.

In general, LW cameras feature a larger dynamic range and are better suited for experiments that involve a large temperature range. They are also well suited for low-smear measurement of fast-moving objects that require shorter exposure time.

Contact a Telops expert if you need help when choosing your infrared camera to make sure it is well-suited for your application.