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How Night-vision Cameras Work


Seeing With New Eyes
With thermal infrared, it's pretty easy to see the areas of this house that are losing heat. The brighter colors represent areas of heat loss.
With thermal infrared, it's pretty easy to see the areas of this house that are losing heat. The brighter colors represent areas of heat loss.
Alfred Pasieka/Peter Arnold/Getty Images

Night-vision cameras boast uses beyond commercial security, public safety, military operations, spy games and checking up on the hired help.

In industry, thermal infrared (TIR) can detect hot spots in circuits, pumps and other equipment, see heat loss, identify signs of water leakage and termites, and allow supervisors to check liquid levels in storage tanks without even popping the top [source: Seidner].

Ultraviolet has been kicked around as a possible night-vision source but, like near-infrared (NIR), it requires an active illuminator. In terms of active night vision, NIR covers the same bases as UV with fewer drawbacks and a longer pedigree, so it remains the standard choice. Still, UV provides an example of how looking a little beyond our visual range can reveal a great deal about our world that light amplification alone cannot.

Take coronal discharge, or corona, for example. Corona refers to a partial release of electrical energy around an energized conductor, such as an electrical transmission line. In essence, it's a visual tip-off that you're losing energy, probably because of the conductor's voltage, shape and diameter, surface irregularities such as scratches and nicks, or dust or water drops [source: California Public Utilities Commission]. Corona often blares ultraviolet; by tuning in to the Solar Blind UV band (240-280 nanometers) -- a wavelength window of opportunity created by the atmospheric absorption of solar UV in that range -- special cameras can detect this telltale UV even in daylight [source: SBUV].

Like your in-laws, thermal IR is very good at finding faults, so industry uses thermographic monitoring to examine fusion reactors, check circuitry and unravel engineering problems [source: American Society for Nondestructive Testing].

If saltwater runs through your veins, night vision can save you a few trips to the crow's nest -- and identify a few hazards your radar might miss. Night-vision cameras can help detect buoys, rocks or outcrops, as well as small vessels, whereas thermal IR can spot oil spills, icebergs or even approaching pirates [source: FLIR].

NIR cameras have infiltrated a number of fields as assaying tools, largely because, unlike typical chemical analyses, they provide nondestructive, cheap and instantaneous analyses without having to leave the site [sources: ASD; Batten]. Botanists use NIR reflectance to gauge levels of nonstructural carbohydrates in plant shoots, a sign of plant stress [source: Batten]. Rock hounds, prospectors and geologists employ shortwave NIR to analyze mineral deposits on-site [source: ASD].

As for the police, the fuzz is all abuzz with NIR. Law enforcement applies the tech to detect counterfeit drugs and to reveal altered documents and forgeries [sources: Rodionova; Somma].

Satellite instruments rely on many of the same sensors to spot key features on the Earth. Under NIR, chlorophyll sparkles like Edward Cullen in sunlight, so it provides an easy way to map vegetation [source: NASA].

When it comes to finding amazing subjects for night-vision photography, however, you don't even need to leave your backyard.


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