Infrared imaging is a technique of capturing invisible infrared images and converting them into visible images. Normal human vision can see only visible light, which is a small part of the electromagnetic spectrum; the electromagnetic spectrum is a scale classifying the different forms of electromagnetic radiation like gamma rays, X-rays, ultraviolet rays, visible rays, infrared rays, microwaves and radio waves. To see in infrared light, infrared imagers and cameras are required. These have special sensors that do not need visible light to operate.
Infrared radiation is produced by all warm-blooded animals and all objects with temperatures above absolute zero; there is no atomic and molecular activity at absolute zero. As the temperature increases, atomic and molecular activity increases, more heat or thermal radiation is produced, and thereby more infrared radiation is emitted. Hot objects give out more infrared radiation than cool objects.
The radiation in the infrared imaging may be emitted from the targeted objects or may be reflected radiation. Reflected radiation may use sunlight for illumination or the imaging device may have infrared illuminator lasers with light-emitting diodes (LEDS) for this purpose. Objects coming in the range of these invisible illuminators absorb or reflect these infrared waves.
The infrared radiation emitted by or reflected from warm objects is detected and picked up by long-wave thermal infrared imagers. The thermal imager lens directs the infrared rays onto an infrared sensor array. There can be several thousand sensors on the sensor array. These transform the infrared energy into electrical signals and these electric signals are then converted into an image.
Infrared light penetrates areas that visible light cannot, and reveals obscure objects. For this reason, it has a myriad uses and new applications are being devised to further extend its scope. Developed originally by the military to produce night vision cameras, binoculars, and gun sights, infrared imaging devices are now regularly used by various civilian agencies.
Police, firefighters, and search-and-rescue teams use infrared imagers, respectively, to catch criminals in the dark, to save people, animals and property caught in a fire, and to rescue people lost at night, in dark places, and at sea. With infrared imaging, technicians can eliminate potential hazards by locating overheated or under-heated parts and leaking chemicals.
Imagers have helped wildlife researchers to study warm-blooded animals in their habitat at night, and archaeologists to examine artifacts and survey archaeological sites. Medical technicians use infrared imaging to perform body scans for diagnostic purposes. Ships, planes, and some luxury cars use infrared imaging devices for navigation, while space satellites use them to study earth conditions and astronomy telescopes use them in astronomy research.