Advanced Imaging

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Advanced Imaging Magazine

Updated: January 12th, 2011 09:49 AM CDT

From Home Security to Homeland Security

Day or night, thermal security cameras keep watch on the borders and in your neighborhoods
FLIR Systems
Thermal security cameras make video images from heat, not reflected light, so they can see clearly night and day.
Figure 2: Right:Security lights and infrared illuminators (image on left)leave large areas uncovered that intruders can exploit to gain access to sensitive facilities.
Thermal security cameras are available in dome, fixed-site, pan/tilt, and handheld configurations.
Fixed-site thermal security cameras provide constant surveillance over fixed points like access areas and sensitive facilities. This one is watching over a sensitive harbor entrance.
Inexpensive hand-held thermal cameras provide 24-hour vision to homeowners and security professionals alike.
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By David Lee

At night, for instance, when there isnít much visible light to work with, we are limited to starlight, moonlight, and artificial lights to help us see. If there isnít enough light, we canít see.

Another limitation of cameras that create images from reflected visible light is contrast. Just like the human eye, these cameras create better images if the object they are looking for has lots of contrast compared to its background. If it doesnít, they wonít be able to see it. Thatís how camouflage works; itís essentially a way of decreasing the visible contrast between an object and its surroundings.

Thermal cameras donít suffer from these basic limitations of visible-light imaging. First, thermal cameras make pictures from heat, not light, having nothing whatsoever to do with reflected light energy. They see the heat given off by everything under the sun. Everything we encounter in daily life creates heat energy, called a ďheat signature,Ē that thermal cameras can see clearly.

Not only does everything have a heat signature, but these heat signatures create their own contrast, so the thermal energy seen by thermal cameras generally creates a better image at night than during the day. They work just fine during the dayóas long as there is the tiniest bit of temperature contrast between an object and its background you can see itóbut they work best at night.

An important tactical distinction to understand is that security operators, law enforcement officers, and federal agents arenít using thermal cameras to identify suspected criminals and terrorists. They use thermal cameras to detect the presence of people in restricted or suspect areas, assess the tactical situation, and respond accordingly. Because no one can hide their heat, thermal security cameras are the best tools officers and agents can use to know how many intruders theyíre facing, and consequently how many officers or agents should respond to meet the threat.



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