What is Thermal Imaging?

Michael Anissimov
Michael Anissimov
Pit vipers, like the Northern Pacific rattlesnake, can see infrared.
Pit vipers, like the Northern Pacific rattlesnake, can see infrared.

Thermal imaging, also called thermography or thermal video, is the means by which humans may see in the infrared portion of the spectrum. Since every object gives off some amount of thermal radiation, thermal imaging is ideal for observing a scene in conditions of extreme darkness or when obscured by smoke, fog, rain, or snow. Some types of night vision use thermal imaging, and thermal imaging is considered the best form of night vision, as it can reveal objects in the blackest of nights. Thermal imaging is used widely in security, the military, navigation, surveillance, firefighting, industry, medicine, and science.

Thermal cameras commonly use false colors in displays to make images easier for people to interpret.
Thermal cameras commonly use false colors in displays to make images easier for people to interpret.

The main tool for thermal imaging is the thermographic camera, which is similar in appearance and operation to a conventional camcorder. Thermal cameras pick up electromagnetic waves with a wavelength between roughly 0.9 and 14 micrometers. In contrast, electromagnetic waves in the visible portion of the spectrum have a wavelength between about 380 to 750 nanometers, significantly shorter than infrared. Though humans are not biologically capable of seeing infrared light unaided, some animals can, notably rattlesnakes and other pit vipers, which have a well-developed pair of organs for the task. Using these organs, rattlesnakes can accurately strike at an object, with their sight and smell cut off, just 0.2 degrees C higher in temperature than its background.

Firefighters can use thermal cameras to examine the site of a fire before going in to look for hot spots.
Firefighters can use thermal cameras to examine the site of a fire before going in to look for hot spots.

To make thermal imaging easier for humans to interpret, thermal cameras often use false color in their displays, ranging from white for the hottest areas to purple and black for the coldest. The hotter an object is, the more thermal waves it emits. Some of the hottest known objects are stars, and astronomers can infer an enormous amount of information about a star with little else than the electromagnetic energy it emits and its mass. Scientists also use thermal imaging to study how animals emit heat. For instance, polar bears are practically invisible in infrared photography, excepting only their nose, as their bodies have adapted to retain heat in the extreme cold.

Michael Anissimov
Michael Anissimov

Michael is a longtime contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

Michael Anissimov
Michael Anissimov

Michael is a longtime contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

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    • Pit vipers, like the Northern Pacific rattlesnake, can see infrared.
      By: fivespots
      Pit vipers, like the Northern Pacific rattlesnake, can see infrared.
    • Thermal cameras commonly use false colors in displays to make images easier for people to interpret.
      By: Ingo Bartussek
      Thermal cameras commonly use false colors in displays to make images easier for people to interpret.
    • Firefighters can use thermal cameras to examine the site of a fire before going in to look for hot spots.
      By: ftfoxfoto
      Firefighters can use thermal cameras to examine the site of a fire before going in to look for hot spots.
    • Many combat aircraft, including the Russian Su-25, are fitted with infrared arrays for the detection and tracking of enemy targets.
      By: Alexander Maksimov
      Many combat aircraft, including the Russian Su-25, are fitted with infrared arrays for the detection and tracking of enemy targets.
    • A thermographic video camera looks similar to a conventional camcorder.
      By: nikkytok
      A thermographic video camera looks similar to a conventional camcorder.