4 Things A Thermal Camera Can Capture (And 3 It Can't)

A thermal camera captures heat signatures and converts them into a visible image. You may recognize thermal cameras for their distinct green, blue, and orange tinted images which have been portrayed innumerable times in movies and comic books. Movies — particularly Hollywood action and suspense films — often portray thermal cameras as miracle devices that can capture impossible sights. 

While thermal cameras can detect surprising details that otherwise go unnoticed, they have their limitations, especially with regards to reflective surfaces. Here's what thermal cameras can and cannot capture. Take a look around you. Everything you see is because light fell on it and certain electromagnetic wavelengths were absorbed or reflected, eventually to be captured by your eyes. However, your surroundings are packed with invisible electromagnetic waves such as infrared, radio waves, and more. 

Smartphone, film, and DSLR cameras works by capturing visible light and producing an output compatible with how our eyes perceive the world. Thermal cameras, on the other hand, capture longer, invisible infrared wavelengths emitted by any object with a heat signature. Thermal cameras interpret those heat signatures and render them into a color-coded image.

Seeing through smoke is one of the most useful features of thermal imaging. Smoke can scatter most visible light, making it an almost opaque screen to the naked eye, but infrared light passes through it without much deflection. Thermal cameras with good resolution and sensitivity can capture everything across a smoke screen with little to no loss in clarity, making them a handy tool for firefighters. Thermal cameras have been used widely in search and rescue missions to guide rescue operations in low-visibility, and smoky environments. Sensors equipped with thermal imaging and artificial intelligence were widely used in the recent California wildfires to detect trapped people and wildlife.

Apart from smoke, thermal cameras can detect heat signatures through light fog, making them a great addition to the advanced driver assistance systems in automobiles. When combined with radar and cameras, thermal imaging helps in interpreting a vehicle's surroundings even in low light conditions, enhancing the self-driving technology.

Thermal cameras shine where all conventional cameras fail — in the absence of light. Because regular cameras capture reflected light, they simply produce a pitch-black image when there's zero light. On the other hand, The heat signatures captured by thermal cameras are always present, even in the absence of visible light. For this reason, thermal cameras find use in a variety of low-light applications like night surveillance and tactical operations. Thermal CCTV cameras are the gold standard for low-light surveillance, especially in places that require heavy security.

Thermal cameras are also widely used by the military. While night vision goggles can greatly enhance visibility in low-light conditions, they need some light to function properly. Thermal cameras can function in pitch black conditions, and military personnel across the globe use thermal imaging scopes paired with their weapons to identify enemies in the darkest of nights.

Thermal cameras excel at capturing even subtle differences in temperature, making them immensely useful in fields like engineering, industry, and medicine. Industries often leverage thermal cameras to detect overheating machines and abnormal friction between moving parts. Thermal cameras are easy to use and can help in early detection of defects in machinery, which can help save on repair and maintenance costs.

The field of medicine also uses thermal imaging widely, especially in injury detection in maladies such as arthritis, circulatory diseases, and muscular pain. Infrared thermometers (working on the same principle of capturing infrared heat signatures) also came in handy when the world tried returning to normal after the COVID-19 pandemic and we needed inexpensive mass detection methods to screen people. Those in charge of some airports, malls, hospitals, and other public spaces used thermal cameras to screen for patients with abnormal body temperatures.

Whether it's "The Dark Knight" or the "Mission Impossible" movies, Hollywood has had a history of misrepresenting thermal cameras, projecting them as some magical incarnation of Odin's eyes. However, the reality is far from the popular depiction.

Most walls are thick enough to block all heat signatures coming from behind them. As thermal cameras rely on deciphering these waves, most walls completely block what's going on behind them. If you point a thermal camera at a wall, you would most likely see the heat signature of the wall and not what's behind. In some cases, thin walls may faintly leak heat signatures from behind, but walls — no matter if they're wooden, concrete, or brick — are mostly opaque to thermal cameras.

That said, some professionals use thermal imagers like Milwaukee's on walls to detect issues that may go unnoticed to the naked eye, such as pipe leaks and gaps in insulation. Professionals also use thermal cameras to detect defects in underfloor heating systems.

Thermal cameras cannot see through glass, and no, it's not just opaque glass that blocks an infrared camera's view. Interestingly, when you point a thermal camera towards a glass pane, you see your reflection in the glass, similar to how a mirror works for visible light. You can try this for yourself if you have a

thermal imaging smartphone camera

.

To understand this seemingly strange phenomenon, let's understand how mirrors show you your reflection. Mirrors have a silver painted side that makes the clear side reflect the light that falls on it. When you see this reflected light, you capture a reflection of yourself.

While glass does not reflect visible light, it reflects infrared light, thus making it behave like an infrared mirror when seen through a thermal camera.

Metals can behave like an opaque wall (showing their own heat signatures) or reflective glass, depending on their type. Most shiny metals reflect infrared light and act as infrared mirrors. Oxidized or matte-painted metals, on the other hand, accurately transmit their own heat signatures when seen through a thermal camera.