Infrared vision

Infrared vision is the capability of biological or artificial systems to detect infrared radiation. The terms thermal vision and thermal imaging^[1][2] are also commonly used in this context since infrared emissions from a body are directly related to their temperature: hotter objects emit more energy in the infrared spectrum than colder ones.

The human body, as well as many moving or static objects of military or civil interest, are normally warmer than the surrounding environment. Since hotter objects emit more infrared energy than colder ones, it is relatively easy to identify them with an infrared detector, day or night. Hence, the term night vision is also used (sometimes misused) in the place of "infrared vision", since one of the original purposes in developing this kind of systems was to locate enemy targets at night.^[3] However, night vision concerns the ability to see in the dark although not necessarily in the infrared spectrum. In fact, night vision equipment can be manufactured using one of two technologies:^[4] light intensifiers or infrared vision. The former technology uses a photocathode to convert light (in the visible or near infrared portions of the electromagnetic spectrum) to electrons, amplify the signal and transform it back to photons. Infrared vision on the other hand, uses an infrared detector working at mid or long wavelengths (invisible to the human eye) to capture the heat emitted by an object.