What Is Infrared?

Electromagnetic waves with wavelengths ranging from 15 micrometers (μm) to 1 millimeter (mm) fall into the category of far infrared, which infrared cameras are designed to detect. Near infrared corresponds to even shorter wavelengths and is commonly used in devices like remote controls, but it’s not what we focus on for thermal imagery.

Blackbody Radiation

When you turn on your stove, it heats up almost immediately. If you allow it to reach a high enough temperature, it will start to glow. All objects emit electromagnetic waves, and the wavelength of this radiation is determined by their temperature.

To visualize this, consider a blackbody. Light can be perceived in two primary ways: the first is through reflection, where light bounces off an object and enters your eyes. The second method is when an object generates its own light based on its temperature. A true blackbody does not reflect light but only emits it.

To illustrate this concept, here’s a fantastic simulation from PhET demonstrating how light varies with temperature.

Infrared cameras function by detecting these wavelengths of light. Since there is a direct correlation between wavelength and temperature, these devices are often referred to as thermal cameras.

Now, let’s jump into some captivating images captured using infrared technology.

The first video showcases "AWESOME STUFF with an infrared camera," presenting various fascinating applications of infrared technology.

Section 2.1: Kitchen Appliances

Here’s an infrared image of my oven. Notice how you can see the reflection of the hot coil on the ceiling? Infrared light can reflect off shiny surfaces just as visible light does. The circle in the lower right corner represents the interior oven light.

Section 2.2: Different Camera Technologies

Most of the images in this article come from one of two infrared cameras. On the left, you’ll see an IR image of my iPhone captured with the FLIR One Pro. The image on the right was taken with the FLIR T1030sc, which, while offering much higher resolution, is also significantly more expensive. I borrowed the T1030 from FLIR—thanks to them for that!

Section 2.3: False Color Imaging Techniques

Below are two infrared images of the same parking lot featuring the same cars, but with different color representations. When infrared light is invisible to the human eye, false color images are employed to interpret the data.

The image on the right utilizes an "iron" color palette where various wavelengths (typically corresponding to different temperatures) are represented in different colors—orange indicates hotter areas, while purple signifies cooler regions. In contrast, the left image is in black and white, where lighter areas represent higher temperatures and darker areas signify lower temperatures. Personally, I prefer the iron palette for its clarity and detail.

The second video, titled "10 Cool Uses for a Thermal Camera," reveals a variety of practical applications for thermal imaging technology in everyday scenarios.

Section 2.4: Temperature Calibration

In this series of images, you can see four containers filled with water. The cup on the left holds ice water, while the beaker on the right contains boiling water. The two middle cups are close in temperature.

In the right image, the color scale is calibrated between 30.9°C for the coldest and 166°C for the hottest. This calibration makes it challenging to distinguish between the temperatures of the middle cups. By removing the ice and hot water from the frame, the camera recalibrates the scale to a range of 67.5°C to 79.3°C, making it easier to see the temperature difference.

Section 2.5: Friction Observations

After slamming on my brakes on an empty road, I captured the area warmed by the friction between the tire and the road. You can also see how heat lingers at the base of the tire.

Section 2.6: Evaporation Effects

As water transitions from liquid to gas, it absorbs energy from its surroundings, resulting in a cooling effect. The image above shows ceiling tiles in a building with a leaking AC unit, where the darker areas indicate cooler, more humid spots.