Thermal video, IRT (infrared thermography), and thermal imaging are all examples of infrared. Thermographic cameras typically detect radiation in the long-infrared range on the electromagnetic spectrum (about 9,000-14,000 nanometers). They produce images of the radiation called thermograms. Because infrared radiation is given off by every object with a temperature higher than absolute zero, thermography can make it possible to see an environment without visible illumination. The amount of radiation given off by an object increases the temperature. Because of this thermography lets you see the variations in temperature. When looking through a thermographic lens, warm objects will stand out against cooler backgrounds. Warm-blooded animals will become easily visible against their environment at night or during the day. Because of this, thermographic cameras are useful to the military and other surveillance cameras.
Uses and History
Certain physiological changes in warm-blooded animals can be monitored with thermal imaging during clinical diagnostics. Thermal imaging is used in veterinary medicine and allergy detection. Some alternative medicine practitioners promote this for breast screenings, despite the FDA advising against it. Airport and government personnel used thermography during the swine flu and are using it again for COVID-19.
Thermography has a big history, but its use has dramatically increased through industrial and commercial applications. The history of thermal imaging has changed drastically recently. During the past 50 years, firefighters used thermography to find people, see through smoke, and locate the base of the fire. Maintenance technicians use thermography to find overheating joints and power line sections, these are signs of impending failure. Construction technicians for buildings use thermal signatures to indicate heat leaks in faulty thermal insulation and then use the results to improve heating and air conditioning unit efficiency.
Operation and Appearance
The operation and appearance of modern thermographic cameras are similar to a camcorder. The live thermogram often reveals temperature variations, so a photograph is not always necessary for analysis. Sometimes a recording module is not built-in. Non-specialized CMOS and CCD sensors keep most of their spectral sensitivity in visible wavelength ranges. Although, by using the “trailing” area of spectral sensitivity and by using off-the-shelf CCTV cameras, it is possible to obtain accurate thermal images of objects 536 °F and higher.
Specialized thermal imaging cameras use FPAs (focal plane arrays) that respond to longer wavelengths. The most common types are InGaAs, HgCdRe, InSb, and QWIP FPA. The newer technologies use low-cost uncooled microbolometers as their FPA sensors. The resolution is lower than an optical camera, mostly at 160×120 or 320×240 pixels, up to 12800×1024 in the more expensive models. Thermal cameras are more expensive than visible-spectrum cameras, and higher-end models are often used in the military and export restricted.