Before you can even begin to understand how thermal cameras work, you need to nail down an understanding of exactly what infrared is, and why it is important for use in thermal cameras.
The Sciency Bit
Chances are you’ve probably heard of infrared at some point. Many devices use it to communicate between themselves or do other tasks, but have you ever stopped to ask exactly just what is infrared?
Infrared, at its most basic level, is a type of light. It’s completely invisible to the human eye, and we can only see infrared by use of tools just like a thermal imaging camera.
The reason we can’t actually see infrared lies in the fact that the wavelengths of infrared radiation lie outside of the spectrum human eyes can see. Other types of light such as radio also lie outside the spectrum our eyes can see.
Although we can’t actually see it, we can actually feel infrared. The heat we feel is actually infrared, and this is because our nerves are sensitive to the heat generated by infrared. It may be invisible, but it’s what keeps us nice and toasty in the winter when you crank up the central heating!
The main form of infrared we see on Earth comes from infrared radiation. Any object above a temperature that is defined as ‘absolute zero’ has molecules that move inside it; as these molecules move, infrared radiation is produced, giving the object a higher IR reading depending entirely on how fast the molecules are moving within that particular object.
Basically this works with temperature – the higher it is, the more the molecules move and the more infrared radiation is produced. Only when an object hits absolute zero, which is defined as the point where atomic and molecular motion ceases, is there no infrared radiation emitted by an object.
This means that, although you may only think hot items emit infrared, colder items such as ice cubes or even snow can emit infrared, as long as their temperature is above absolute zero.
Absolute zero is, naturally, extremely cold indeed. If you think winters are chilly, imagine how cold it’d be down at absolute zero! It is defined as −273.15° on the Celsius scale, which works out at -459.67 on the Fahrenheit scale!
Not many examples of objects being found at this temperature can be found on Earth, which is how practically everything on the planet emits some kind of infrared radiation.
Detecting Infrared with a Thermal Camera
Every object emits thermal radiation if it is above absolute zero in temperature. The level of IR given off by an object is known as that object’s emissivity.
By use of complex algorithms, the thermal imaging camera is able to pick up on the emissivity of any given object, and replicate the amount of IR being given off by that object as a thermal image known as a thermogram.
