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Thermal Imaging Cameras

A thermal imaging camera scans a building and sees temperature variations.

Thermal imaging cameras have become invaluable tools with a wide range of applications. From finding gaps in underfloor and ceiling insulation to aiding first responders, these devices serve numerous practical purposes.

What is a Thermal Imaging Camera?

A thermal imaging camera is a device that captures infrared radiation emitted by objects and creates a visual representation of their temperature variations. Unlike traditional cameras that rely on visible light, thermal cameras work in the infrared spectrum.

What is ‘Infrared’?

So what exactly is ‘infrared’?

Infrared (IR) is a type of electromagnetic radiation that lies beyond the visible light spectrum. Since humans cannot see infrared radiation, it is experienced as heat. Infrared radiation has longer wavelengths than visible light, ranging from approximately 700 nanometres to 1 millimetre.

Who Invented the First Thermal Imaging Camera?

In 1929, Hungarian physicist Kálmán Tihanyi invented an infrared sensitive (night vision) camera for anti-aircraft defence in Britain. Initially, thermal imaging cameras could only produce one image at a time, which took an hour to generate.

The technology evolved over the years, and by the 1960s, the thermal cameras were large, complex and expensive, primarily designed for military and industrial purposes.

Since then, thermal imaging cameras have become more compact and affordable, and have been used in various fields beyond the military.

Why are Thermal Imaging Cameras Used?

Thermal imaging cameras are used for two main reasons:

1. Detecting temperature variations

These cameras can measure and identify temperature differences in objects and environments, something the human eye can’t properly do. This is capability is useful in many industries.

2. Visibility in low light or no light conditions

Unlike traditional cameras that rely on visible light, thermal cameras can “see” heat in complete darkness. This makes them very useful in situations where visibility is compromised, such as during nighttime operations, in dark roof spaces or in areas with heavy smoke.

A firefighter uses a thermal imaging camera for search and rescue.
Thermal imaging cameras measure temperatures accurately and can be used in low-light areas.

How Does a Thermal Imaging Camera Work?

Thermal imaging, or thermography, operates based on the principle of detecting and visualising infrared radiation emitted by objects. All objects with a temperature above absolute zero (-273.15°C or -459.67°F) emit infrared radiation. The amount of radiation emitted depends on the object’s temperature. Warmer objects emit more, while cooler objects emit less. 

Here’s a simple explanation of the process:

1. Optical system

The thermal camera has a special lens (usually made out of germanium) and optical system that focuses the infrared radiation onto the infrared sensor array.

2. Infrared sensor array

The heart of the thermal camera is its infrared sensor array, which is composed of thousands of tiny sensors. Each sensor in the array measures the amount of infrared radiation it receives.

3. Signal processing

The detected infrared radiation creates a temperature pattern on the sensor array. The camera’s signal processing unit converts these temperature patterns into electrical signals.

4. Image creation

The electrical signals are then translated into a thermal image, with different colours or shades representing various temperature levels. Hotter areas are typically displayed in warmer colours (such as red or yellow), while cooler areas are shown in cooler colours (like blue or purple).

5. User interpretation

The user will interpret the thermal image to identify anomalies, temperature variations or potential issues in the observed area.

Difference Between Infrared and Thermal Imaging Cameras

These two terms are often used interchangeably. All thermal cameras fall under the umbrella of infrared cameras since they operate within the infrared spectrum, but there are a few small differences.

Infrared cameras, broadly speaking, capture infrared radiation, which is not visible to the human eye. These cameras are commonly used in night vision applications, security systems like CCTV and some medical imaging processes. Infrared cameras can detect infrared radiation but will generally not provide detailed thermal information or temperature readings. They capture both still images and videos.

On the other hand, thermal imaging cameras are a specific type of infrared camera designed to visualise and quantify temperature variations in a scene. They operate based on the principle that all objects with a temperature above absolute zero emit infrared radiation. The camera’s sensor array measures this radiation, and a thermal image is created, with colours or shades representing different temperature levels. Thermal imaging cameras are widely used for insulation inspections, medical diagnostics and firefighting.

A man stands in the middle of a room, testing an infrared CCTV camera.
Example of an infrared camera's image. Image Courtesy: CCTV Camera Pros.

Can Thermal Imaging Cameras See Through Walls?

No, thermal imaging cameras cannot see through walls. Thermal imaging relies on detecting infrared radiation emitted or reflected by objects, and walls generally block or absorb this radiation.

Who Uses Thermal Imaging Cameras?

Thermal imaging cameras are used by a wide range of professionals and industries:

  • Insulation professionals. Insulation installers use thermal imaging cameras to identify areas with insufficient insulation in buildings. By detecting temperature differences, they can locate spots that require additional insulation.

  • Firefighters. Firefighters use thermal imaging cameras to navigate through smoky environments, locate individuals in rescue operations and identify hotspots in fires.

  • Law enforcement. Police and other law enforcement agencies use thermal imaging for surveillance, tracking suspects in low-light conditions and locating hidden objects or individuals.

  • Building inspectors. They use thermal imaging to identify issues such water leaks or electrical problems that may not be visible to the naked eye.

  • Industrial maintenance technicians. Maintenance technicians use thermal imaging cameras to detect overheating components in machinery, electrical systems and other equipment, preventing potential failures.

  • Search and rescue teams. Search and rescue teams utilise thermal imaging cameras to locate missing people, especially during nighttime.
  • Energy auditors. Energy auditors use thermal imaging to assess the efficiency of buildings by identifying areas of heat loss or air leakage.

  • Medical professionals. In the medical field, thermal imaging is used for diagnostic purposes, such as detecting inflammation, measuring a fever and monitoring blood flow.

  • Pest control professionals. Pest control workers use thermal imaging to identify pest infestations by detecting variations in temperature caused by the presence of pests.
  • Hunters. Avid hunters may use thermal imaging to track and locate animals in low-light conditions.

  • Military and defence. The military will often use thermal imaging cameras for reconnaissance, surveillance and targeting purposes.

Can I Use My Phone as a Thermal Imaging Camera?

It is possible to use your phone as a thermal imaging camera, but it typically requires an external thermal camera attachment or a specialised phone with built-in thermal imaging capabilities.

External thermal camera attachment

Some companies offer external thermal camera attachments that connect to your phone via USB or through the phone’s charging port. These attachments come with their dedicated apps and allow your smartphone to capture and display thermal images. Keep in mind that the quality and features may vary based on the attachment and the smartphone compatibility.

Phones with built-in thermal imaging

Certain smartphone models are designed with integrated thermal imaging cameras. Cat (or Caterpillar) is a well-known company that sells phones with this function. These devices often have an additional sensor alongside the regular camera, allowing users to switch between traditional and thermal imaging modes within the phone’s camera app. These smartphones are purpose-built for applications like building inspections and industrial maintenance.

It’s important to note that using your phone as a thermal imaging camera will not provide the same level of accuracy and functionality as professional-grade thermal cameras. The thermal resolution and sensitivity of dedicated thermal cameras are generally much higher, offering more detailed and precise thermal images.

A woman tests a CAT thermal imaging camera, built into a mobile phone.
CAT sells mobile phones with built-in thermal imaging capabilities. Image Courtesy: CAT.

What Are the Disadvantages of Thermal Imaging Cameras?

While thermal imaging cameras offer valuable benefits in many different scenarios, they also have some disadvantages. Some notable drawbacks include:

  • Cost. High-quality thermal imaging cameras are expensive. This cost can be a barrier for individuals or smaller businesses.

  • Limited detail. Thermal images generally lack fine details compared to standard visual images, which may be a downside during specialised tasks.

  • Less functional during adverse weather conditions. Wild weather, such as heavy rain, snow or fog, can impact the performance of thermal imaging cameras. The thermal radiation from objects may be obstructed or distorted.

  • Affected by reflective surfaces. Shiny or reflective materials can bounce off infrared radiation, leading to inaccurate temperature readings and compromised image quality.

  • Inaccurate readings of certain materials. Some materials, like glass, do not emit thermal radiation effectively. Thermal imaging cameras may not be able to capture accurate temperature readings through such materials.

How Much Does a Thermal Imaging Camera Cost?

There’s a thermal imaging camera for almost any budget. Generally:

  • an entry-level thermal imaging camera is approximately $500-$1,000
  • an intermediate camera is around $3,000-$6,000
  • an advanced or specialised model can range anywhere from $10,000 to $30,000+!

Best Thermal Imaging Cameras

Some of the best handheld thermal imaging cameras (in various price ranges) include:

  • HIKMICRO B Series (entry-level)
  • TOPDON TC004 (entry-level)
  • FLIR TG267 (entry-level)
  • Seek Thermal Reveal Pro (intermediate)
  • FLIR E5 Pro (intermediate)
  • FLIR E8 Pro (advanced)
  • FLIR E96 (advanced).
Some of the best thermal imaging cameras are made by FLIR, lined up in this image.
FLIR makes many professional thermal imaging cameras.

Does Every Insulation Installer Need a Thermal Imaging Camera?

While these cameras can be useful, they’re not a must-have for every installer. However if the installer is required to assess the level of insulation in a physically inaccessible area (for example a wall cavity, or ceilings in multi-level apartment blocks) then a thermal imaging camera is a great tool to have.