thermal imaging camera

How do Thermal Imaging Cameras Work?

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Kevin Jefferson

March 16, 2020

When somebody mentions cameras, most people will immediately think of ordinary cameras. Everybody is familiar with them – we know their purpose and what they’re capable of. What about thermal imaging cameras?

In recent years, these devices went from being something only seen in movies to commercially available products. Nowadays, thermal imaging cameras are used in many different sectors – construction, medical, industrial, law enforcement, and more.

How do these gadgets work? What can they detect? What features do they possess? How are they different from the night vision cameras? Keep reading – we have all the answers.

The Backstory

  • William Herschel (1738 – 1822) discovered the presence of infrared light in 1800. While studying the visible light spectrum, Herschel discovered that one form of light produces more heat than the others.
  • In 1929, Kálmán Tihanyi invented the very first infrared video camera. It was used by the anti-aircraft branch of the British Army.
  • In the 1970s, solid-state thermal-imaging arrays were invented. These were quickly upgraded to single-crystal-slice imaging appliances.
  • During the 1980s and 1990s, handheld units finally appeared. Unlike the earlier versions, these were more versatile and user-friendly.
  • However, it was only during the 2000s that these devices became cheap enough to be used by civilians. The production costs of uncooled arrays decreased, making these cameras a financially viable option.
  • As expected, this leads to a boom in popularity. Nowadays, thermal imaging cameras are used for applications such as autopiloting systems, environmental control, transport navigation, architecture analysis, emergency response, and more.

What is Thermal Imaging?

To put it simply, thermal imaging allows a person to see the heat that a particular object is radiating off itself.

Devices like thermal imaging cameras (also known as thermographic cameras) are capable of recording the temperature of the objects they’re pointed at. In order for the user to notice how much heat an object is radiating, these cameras assign different shades of color to different temperatures.

In almost all cases, warmer temperatures are given shades of yellow, orange, and red. Colder temperatures, on the other hand, are given shades of green, purple, and blue. For example, an object that radiates more heat than the surrounding objects will be redder.

Some cameras of this type use a greyscale. They can convert fine temperature variations into thousands of different shades of grey.

Read: Arc Flash

How Does Thermal Imaging Camera Work?

Thermographic cameras can recognize and capture different degrees of infrared light. In that way, they can detect temperature. Although it’s invisible to the naked eye, it is possible to feel infrared light as heat in case of high-enough intensity.

In nature, heat can be transferred in many different ways. The emanation of infrared radiation is one of them. When you’re holding hands over the fire, heat will be transferred to your hands through infrared radiation.

Objects that are hotter generate more infrared radiation. Thermographic cameras are capable of seeing this radiation. They can also convert it to images visible to the human eye. This principle of operation is similar to that of the night-vision cameras.

Much of the hardware of a thermal imaging camera consists of minute measuring devices. These are called microbolometers, and each pixel has one microbolometer assigned to it. Once the microbolometer detects the temperature, it gives its pixel an appropriate color. This is how a thermal image is created.

This complex construction is precisely why most of these devices use a low resolution. This is especially true when they’re compared to modern cameras, TVs, or smartphones. In fact, even the best thermal imaging cameras rarely go above the resolution of 640 x 480 pixels.

Types of Thermal Imaging Cameras

These types of devices can be separated into two categories:


Un-cooled thermal imaging cameras are common and widely used. The device operates at room temperature and uses batteries that are contained inside the unit. It’s a system that activates immediately and produces minimal noise.

Cryogenically Cooled

As their name suggests, these cameras have their elements sealed and cooled to subfreezing temperatures. This type of system provides better resolution and greater sensitivity. However, this also makes them more susceptible to damage, as well as more expensive.

What’s the Difference Between Thermal Imaging Cameras and Night-Vision Cameras?

Technically speaking, thermal imaging can be used to better perceive objects/persons in the dark. However, if you only want to see in the dark, a thermographic camera is overkill.

For example, thermal night vision can be of great use in police helicopters. This camera can easily discern people from the environment. As you may suspect, this makes it ideal for use in the dark, but can also be helpful for finding suspects who blended in with their surroundings in plain daylight.

However, thermal cameras capture longer wavelengths of infrared. This makes their manufacture more expensive. Night vision cameras rely on shorter wavelengths of infrared and are, therefore, cheaper to make. They can’t detect heat but allow the user to see in the dark.

Thermal Imaging Camera Applications

Originally developed for army use, these types of devices are now used for a variety of purposes. These are the most common applications:

  • Autopiloting systems
  • Animal & pest management
  • Architecture analysis
  • Firefighting
  • Law enforcement
  • Healthcare & medicine
  • Emergency response
  • Science & research
  • Security
  • Transport navigation
  • Electrical maintenance
  • Plumbing

What to Look for in a Thermal Imaging Camera?

The best thermal imaging cameras come in several varieties, ranging from personal to professional models. Their price depends on the quality of construction, as well as on bells and whistles they feature. If you’re planning to purchase one, ask yourself the following questions:

Accuracy – What level of accuracy of detection do I need?

Mass & Volume – Do I need a portable or stationary model?

Spectral Band – Which areas of the electromagnetic spectrum do I want to see?

Input Power – Will I be using batteries or AC power?

Measurement Modes – How many different measurement modes will I be using?

Screen Size – Do I need a large screen? What about touchscreen controls?

Resolution – How detailed do I need the images to be?

Image Overlay – Do I need image fusion and picture-in-picture functions?

Field of View – What angle should the lens detect?

Sensor Lifetime – How many images/hours should the sensor be rated for?

Video Storage – Live imaging only or video storage?

Wireless Connectivity – Will I be sending images to other devices?


Knowing how thermal imaging cameras work will allow you to put your model to greater use. However, these devices are much more user-friendly than before and can be operated by almost anyone. With time, they will become even more sophisticated and their applications and uses will increase further.

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