How Thermal Imaging Works

Thermal Image captured with the AGM ASP-Micro TM160 Thermal Monocular

Guide to how thermal binoculars, monoculars, and other imaging devices work with links to examples, reviews & recommendations.

I think the best way to think about thermal imaging is that instead of seeing with light energy as we do normally, a thermal imaging device like a monocular or binocular enables you to see with the heat energy that all objects with a temperature of more than absolute zero give off.

For me this concept is easy enough to grasp, but how exactly does it all work, what are its advantages and shortcomings when compared to normal vision using light (including night vision) and what should you look out for when looking for a thermal imaging device?

So in this article I will go through all this, which I hope will help you decide a) if you need a thermal imaging device b) if you do, which device you should get depending on your requirements and budget.

How Thermal Imaging Works

All objects with a temperature of more than absolute zero emit thermal infrared energy and so in a nutshell thermal monoculars, binoculars and other similar devices have detectors inside them are able to convert the energy contained in the infrared wavelength into a visible light display and thus are able to “see” all objects, regardless of the level of visible ambient light.

Thermal Detectors

Thermal binoculars, monoculars, and indeed many other imaging devices have detectors inside of them made up of un-cooled focal plane arrays of Vanadium Oxide. This also goes by the name of Vanadium Pentoxide due to its chemical makeup of two parts Vanadium and five parts Oxygen.

With thermal imaging, it is the Vanadium that is important as it has a high level of thermal resistance and thus is often used as the material to make bolometers (electromagnetic radiation detectors) and the microbolometer arrays used for thermal imaging in thermal monoculars, binoculars, and cameras.

The hotter an object is, the more infrared radiation it produces. The microbolometers inside the thermal camera are able to differentiate the temperature from the amount of infrared radiation that hits it and thus it then assigns that particular pixel to show the corresponding color for the viewer.

Pixel Count

Because each pixel that you see in the view has its own microbolometer, you can understand why most thermal devices (even the very best ones) tend to have a far lower resolution than what we have become accustomed to on a digital camera but is one of the most important aspects to look out for when choosing which thermal imaging device to get:

AGM Asp-Micro TM160 Thermal Monocular

Entry Level Thermal Monoculars

So because of this, at the lower end of the market, you can expect to see resolutions of about 160x120 on popular thermal monoculars like the AGM Asp-Micro TM160 (pictured right) and the TK Scout from FLIR.

More Info & Recommendations

High-End Thermal Binoculars & Bi-Oculars

ATN BinoX-THD Thermal Digital Binoculars

At higher levels of what is available to the public, where you can expect to pay upwards of $3000 on Thermal Imaging Binoculars like the ATN BinoX-THD (pictured right), the popular FLIR BHS-X Command, and the Armasight Helios 336 these do have an improved resolution, but even then you can expect a resolution of about 640 x 480.

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