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Jan 09, 2020 | 11:17 pm 544 0

How Does Thermal Imaging Work?

How Does Thermal Imaging Work?

Thermal cameras have long been considered the best way to detect people in the outdoors. At one time, they were used primarily only for the most critical sites. But innovations and advancements, along with price reductions, now make them available for more common security applications, like for preventing theft and vandalism. Thermal imaging is used in all sorts of different scenarios—utility and energy companies use it to see where a house might be losing heat through door and window cracks. Police helicopters use it to locate suspects at night. Weather stations use it to track storms and hurricanes. It’s used in the medical field to diagnose different disorders and diseases. Also it is one of the favorite types of equipment for hunters and outdoorsmen. We’ve written this article to help explain how a thermal imaging camera works and why it represents a great choice for outdoor security.

What Is Thermal Imaging?

In the most basic of terms, thermal imaging allows you to see an object’s heat radiating off itself. Thermal cameras more or less record the temperature of various objects in the frame, and then assign each temperature a shade of a color, which lets you see how much heat its radiating compared to objects around it.

Colder temperatures are often given a shade of blue, purple, or green, while warmer temperatures can be assigned a shade of red, orange, or yellow. For example, in the image at the top of this post, you’ll notice the person is covered in shades of red, orange, and yellow, while other areas are blue and purple. That’s because she’s radiating more heat than surrounding objects.

Some thermal cameras use a grayscale instead. Police helicopters, for instance, use a grayscale to make suspects stand out.

How Does Thermal Imaging Work?

Thermal cameras detect temperature by recognizing and capturing different levels of infrared light. This light is invisible to the naked eye, but can be felt as heat if the intensity is high enough.

All objects emit some kind of infrared radiation, and it’s one of the ways that heat is transferred. If you hold your hand over some hot coals on the grill, those coals are emitting a ton of infrared radiation, and the heat is transferring to your hand. Furthermore, only about half of the sun’s energy is given off as visible light—the rest is a mix of ultraviolet and infrared light.

How Is It Different Than Night Vision?

Thermal night vision is great to have, since it can easily differentiate a person from the rest of the environment. This not only makes it easier to spot suspects in the dark, but even in broad daylight it makes it much easier to find someone who may have blended in with their surroundings.

However, most thermal cameras rely on longer wavelengths of infrared, whereas your typical night vision security camera captures shorter wavelengths of infrared, and is much cheaper to manufacturer. Thermal cameras, on the other hand, have the ability to capture longer wavelengths of infrared, allowing it to detect heat.

To make things simpler we've put together the following comparative chart of thermal and night vision devices. 


Thermal vision

     Used at day and night

     See through smoke/fog/dust/sand

     Does not require light source

     See through leaves and thin materials

     Track residual heat (handprints, footprints) Image requires some training to interpret

     More expensive



Night vision

     Used only at Night, can be damaged if used at day

     Fog, smoke and dust obscures the image

     Requires a little amount of light provided by natural source or IR illuminator

     Camouflage is often still effective. Does not see through leaves or materials

     Shows more natural picture, easier to recognize the objects

     More affordable



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