The infrared section of the electromagnetic spectrum includes wavelengths between 740nm and 300 µm. It sits between visible and microwave on the spectrum and is undetectable by the naked eye. All objects release infrared radiation. The intensity of the infrared radiation emitted determines how the objects appears on an infrared camera system. A greyscale is often used to show the thermal properties of the object.
Infrared camera systems are essential for information gathering in low light conditions. They have been largely utilised in several industries as they provide more information on an object or scene, at any time of day, and in any weather condition. They have become a critical payload for aircraft, UAVs and marine vessels.
Long Wavelength Infrared (LWIR) and Medium Wavelength Infrared (MWIR) sensors are used to detect heat. LWIR sensors show information in the long wave infrared spectral band of between 8 and 14 microns, whereas a MWIR lens reveals information in the mid-wave infrared spectral band of between 3 and 5 microns. Both sensor types can be used to detect animate objects, such as humans, animals and vehicles.
MWIR sensors perform better in high humidity and high heat conditions. They can reveal more information at longer distances than LWIR sensors. It is necessary that MWIR sensors are cooled to be able to operate effectively. LWIR sensors perform better in smoky conditions and at lower temperatures. At such wavelengths, there is less variation between temperatures from the energy radiated by the object. Therefore, LWIR sensors are not affected by radiation from the sun.