Sierra Olympic Technologies Inc.

What is Thermal Imaging?

Thermal: ther·mal; ˈTHərməl/

adjective: thermal

1. of or relating to heat.


Imaging: im·age; ˈimij/

verb: gerund or present participle

1. make a representation of the external form of.

We make images of heat.  Think about how an image is made with your smartphone camera.  Visible light reflects off the objects you want to image, that light comes into a lens, it is focused on a sensor, and an image is delivered.  We do the same thing with heat coming from the object.  We have been thermal imaging for close to 25 years, since the first solid-state thermal imagers were introduced.  You might wonder how do you focus heat?  What kind of sensor detects heat?  How do you display heat?  All good questions.

Just as in any science or technology, there are armies of brilliant people making thermal imaging products better all the time.  Just like the evolution from early PCs with C:\> to how we function with smartphones, thermal imagers have come a long way.  But very simply, thermal imaging is your thermal scene, a lens, a sensor, and a display, simple as that.


Again, thermal scene, lens, sensor, display.  The easiest way to understand thermal radiation is to understand how Sir Frederick William Herschel discovered infrared radiation in 1800.  Very basically, Hershel studied sunlight through a prism.  We all know the visible light is broken into a rainbow.  Put a thermometer on the colors, then put a second thermometer well past the red, and you will see the second thermometer’s value rise.  That is the “light” we see.  It is the light past the red in the visible spectrum, or the infrared light captured by our cameras.

More basics:  Everything always emits thermal, or infrared, radiation.  You can’t turn it off unless you are at absolute zero (-273 deg C).  You and everything around you are not the temperature of the sun, but our cameras are sensitive enough to detect typical temperatures on planet earth, and have sufficient contrast to generate great images.  Simple enough.

Fig. 1: Herschel used a prism and thermometers in his experiment that eventually led to the discovery of the infrared region of the eletromagnetic spectrum.


Our eyes see visible radiation. Thermal imagers see infrared radiation, something entirely different. You can buy a great camera with 10 megapixels that will take snapshots and videos for $200. The smartphone is now the most popular form of camera, and its sensor costs a few bucks. We aren't there, and probably never will be. We use exotic materials in our sensors that are not so common, our lenses are made from crazy materials like Germanium and Zinc Selenide, and we don't have billions of customers. But we are now offering cameras that are truly affordable. If you have a problem where you need to locate heat or image heat, our cameras make it easy and affordable.


We should put some of the most basic technical items on the table. If you are approaching thermal imaging from an experience based upon standard visible imaging, allow us to get some preliminaries out of the way.

We have 320 x 240 (QVGA) and 640 x 480 (VGA) imagers. There are larger arrays, but these are exotic and expensive. In thermal imaging, you can get a 3MP imager from a big military contractor for a million bucks, maybe.

There are billions of people on the planet, and most have a visible camera in the cell phone. Thermal imaging just does not have that large customer base to create a $200 snapshot camera, or a $50 web camera.  But compared to where we were only a few years ago, we are very low cost.

Optics 1:
Compared to the selection of optics you see in the visible world, infrared optics are very limited. Glass is opaque to thermal radiation, so we must build optics out of exotics such as Germanium or Zinc Selenide or Sapphire. This makes optics expensive and limited in selection.

High speed, windowing, triggers, binning, 3-CCD - functions commonly available in modern cameras are not available on our value priced cameras. You are back up to very high priced cameras for these functions. Think $50,000 and up.  Think $452 hammers and $640 toilet seats.

Optics 2:
With my SLR camera, I can pop one lens off and install another in seconds. No issues. Can't do this with thermal imaging. The camera and lens are designed together. When you install another lens, it doesn't work as well. There are procedures and tricks, but in general, one camera-one lens.