Thermal Imaging Devices, Pro’s and Con’s

thermal imaging

A few months ago, I posted an article on hiding from thermal imaging devices, since then I learned a bit more about them.  So I decided to post a second article with some new information.  I see a number of people purchasing various infrared imaging devices instead of night vision.  Now there is nothing wrong with infrared imaging devices, they serve a good purpose.  But be sure you understand the pro’s and con’s of them prior to spending your money.

An infrared device or thermal imaging camera forms images using infrared radiation, similar to a common camera that forms an image using visible light.  Understand that IR is not X-ray.  Regardless of what Hollywood shows, it can’t detect a differential heat image through common solid materials such as wood, concrete or metal.

However, a good imaging device will see through plastic film, clear or black and holes in any cover, you are hiding behind.

A good example is if you are hiding in a dumpster and are not leaning against the side, the camera will not see a hot spot.  However, if you are touching the side he can see the hot spot created by your body heat.

Your thermal signature will not pass through glass, as long as you are not in contact with it.  Because of this, the lenses of IR imagers are not made of glass.

The best way to hide from IR detection is get behind or under what is already there, remember mass counts.  If you have to look out, choose the spot that will expose the smallest portion of your body.  If they detect this hot spot it can be mistaken for a small animal or may not be noticed from a distance.

I have heard some people say that space blankets will work to hide your heat signature.  The problem with this is that the heat signature of the space blanket will not match the surrounding area and may create a obvious abnormality.

Thermals are an amazing tool to detect the body heat of an enemy, but like night vision goggles they have their limitations.  Fog that is warmer than the surrounding air looks like a wall through thermals, and in the summer months, rocks get so hot that they glow and everything looks like a person.

Thermals work best in areas where there is wide differences in temperature, 30 degrees F or more.  In the cold winter weather you could see the heat left in the snow from a person’s tracks.  In snowy conditions your heat signature will stand out. But if you are hiding from thermal imaging, those conditions can also be used to your advantage. Hiding in a snow cave or just covering oneself in snow is enough to hide one’s heat signature.

Lighting fires to mask thermal signatures is common practice among the Taliban.  They also carry heavy wool blankets to hide under, when they suspect thermal imaging devices.

Here are the answers to a couple of questions regarding thermal imaging.

Can thermal imaging see through clothing?

No but, if, for example, a suspect had a gun under their shirt, its exterior area would appear “cooler” to the camera and indicate to police that someone may be carrying a gun.

How is law enforcement using this technology?

First, it helps police officers stay safe by spotting suspects hiding in bushes or in dark alleys, it can “see” someone hiding behind an object like a box or trash can if that person radiates enough heat to cast a thermal image around the object.

It assists police in pursuit.  Thermal cameras can see people running in the night, even through the cover of trees. These cameras are also used to identify a recently driven car (by the warmth of the hood), or in some cases even the warmth of the skid marks left by a fleeing car.

After executing a search warrant, police may sometimes use these cameras to look for objects hidden in interior walls, like drugs or money.  These objects act like insulation in the walls, and may produce a different thermal image in that section of the wall compared with the surrounding wall space and studs.

Thermal imaging devices are a good tool and have their uses, but they are not perfect.  Think about how many times they are used in searches to find lost hikers.  They don’t always work.  If you purchase a unit, don’t become dependent on it.


4 thoughts on “Thermal Imaging Devices, Pro’s and Con’s”

  1. Your article presents a decent introduction, however you have not made a distinction between IR and thermal.

    IR is infra-red, and is part of the light spectrum. Thermal imaging, as you stated, is based on temperature differences. The two are not related.

    Anyone purchasing a night vision device, will be able to see artificial IR light, and filters are available for candescent bulb flashlights just for this purpose. Anyone purchasing a thermal device will not be able to see this, nor will a night vision device be able to see thermal.

  2. Infrared imaging can refer to any imaging system that operates in the infrared, which extends from about .7 to 300 microns wavelength. Thermal imaging, as the term is commonly used, refers to an infrared imaging system designed specifically for the portion of the infrared range which is emitted by object at or just above room temperature. This is typically in the neighborhood of 10 microns. At this wavelength you will see images that people typically associate with “thermal vision.” People will be brighter than room temperature objects, running car engines will stand out, etc.

    Infrared imaging is useful as well, of course. Most “night vision” goggles work by imaging visible and infrared light, and amplifying the resulting image to a level that the user can detect. Using infrared in addition to visible simply means that the goggles have a stronger signal to work with before amplification, because they are sensitive to a broader range of wavelengths.

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