How does thermal imaging work

How does thermal imaging work?

Thermal imaging is a technology that enables us to visualise heat emitted by objects, converting otherwise invisible infrared radiation into a visible image. This is done by recording the temperature of various objects in the frame, and then assigning each temperature a shade of a colour, which lets you see how much heat it’s radiating compared to objects around it.

This capability has revolutionised various industries, from building inspections to medical diagnostics, by providing insights into temperature variations that are undetectable by the human eye.

Understanding infrared radiation

Infrared radiation is a type of electromagnetic radiation with wavelengths longer than visible light but shorter than microwaves. While invisible, this radiation can be perceived as heat when its intensity is high enough. All objects, regardless of temperature, emit infrared radiation—a phenomenon governed by Planck’s Law of blackbody radiation. The hotter an object is, the more infrared energy it radiates.

Thermal cameras detect temperature by recognising and capturing different levels of infrared light. This light is invisible to the naked eye, but can be felt as heat if the intensity is high enough. All objects emit some kind of infrared radiation, and it’s one of the ways that heat is transferred. The hotter an object is, the more infrared radiation it produces. Thermal cameras can see this radiation and convert it to an image that we can then see with our eyes.

How do thermal cameras detect heat?

Each thermal camera has an internal measuring device that captures infrared radiation, called microbolometers, and each pixel has one. The microbolometer records the temperature and then assigns that pixel to an appropriate colour, which then shows the findings on the camera screen.

Each microbolometer pixel absorbs infrared radiation and experiences a change in resistance proportional to the energy absorbed. This resistance change is then translated into an electrical signal, which the camera’s processor converts into a temperature reading.

Converting data into visual images

To create a thermal image, the camera assigns a specific colour or shade to each temperature range. This process, known as false colour imaging, maps temperature gradients onto a visible colour spectrum, often ranging from blue (cooler temperatures) to red or white (hotter temperatures). By displaying these colours on the screen, thermal cameras provide an intuitive visualisation of heat distribution.

Where did thermal imaging camera originate?

It is unclear the origins of thermal imaging. There have been numerous accounts of thermal imaging by other names from the 1800’s but no confirmed inventor. The thermal imaging cameras used today are based on technology that was originally developed for the military. In 1929, Hungarian physicist Kálmán Tihanyi invented the infrared-sensitive (night vision) electronic television camera for anti-aircraft defense in Britain. The first American thermographic cameras developed were infrared line scanners. Thermal imaging in its present form was originally developed for military use during the Korean War.

Where do we use thermal imaging?

Thermal imaging cameras have migrated into other fields and have found many uses.

Electrical maintenance uses for thermal imaging are extensive. For example, power line technicians use thermal imaging to locate and pinpoint joints and parts that are at risk of overheating as they’re already emitting more heat than the stronger sections. They can also help spot loose connections or devices that are starting to fail.

Animal and Pest management is a field which has a surprising number of uses for thermal imagers. They can help spot pests or animals in dark roof areas without having to climb up into them, and they can detect potential termite activity. Also, they’re commonly used to more easily conduct wildlife surveys in a totally non-invasive, non-intrusive manner.

Transport navigation gets significant benefits from thermal imaging, particularly when traveling at night. For example, maritime navigation uses it for clearly seeing other vessels, people and obstructions during the night while out at sea. In recent years, cars have begun incorporating infrared cameras to alert drivers of people or animals beyond streetlights or the reach of their headlights.

Healthcare and medicine also have practical uses, such as to spot fevers and temperature anomalies. This has proven to be especially important in airports where these thermal imaging cameras can quickly and accurately scan all incoming or outgoing passengers for higher temperatures, which was crucial during recent outbreaks of diseases like SARS and Ebola. Additionally, thermal imagers have been proven to help diagnose a range of disorders associated with the neck, back and limbs, as well as circulatory problems.

Fire-fighters use thermal imaging to help them see through smoke, particularly in rescue missions when they’re searching for people in an otherwise obscured and dangerous environment. They also use thermal cameras for rapid identification of spot fires, so they can intervene before they spread.

Police and law enforcement agencies incorporate thermal imagers into their surveillance equipment, used for locating suspects especially at night, as well as to investigate crime scenes and also for search and rescue operations. They’re superior to night-vision devices, as they don’t require any ambient light and are unaffected by bright lights, which is essential for tactical missions.

Science and research are undoubtedly sectors that draw significant benefits from using thermal imagers, for accurate and precise visualisations of heat patterns such as dark side of the moon.

Other applications which use a thermal imaging camera include heating, ventilation and air conditioning installations, mold detection, quality assurance in processes such as glass manufacturing and many more.

How is thermal imaging used for leak detection?

Plumbers use thermal imagers to inspect sites of possible leaks, mainly through walls and pipes. Since the devices can be used at a distance, they’re ideal for finding potential problems in equipment that is either hard to reach or might otherwise pose safety issues to workers.

Mechanical and building construction technicians who work with thermal insulation use imaging to quickly identify leaks, which is important to maintain efficient temperature regulation in a building. At a glance, they can analyse a building’s structure and spot faults. Heat loss from walls, HVAC equipment, doors and windows are common thermal performance issues that are easily picked up by a thermal imager.

Money saving is something you wouldn’t necessarily expect from a thermal imaging device, but when you think about everything it can do, it definitely makes sense. After the upfront cost of purchasing the device, they can undoubtedly save your business or home thousands of dollars or more in potential maintenance and repair costs that might incur if faults, leaks or weaknesses were not identified earlier.

However, it’s important to recognise that while thermal imaging has all these applications, it’s often best to use additional instruments or tools when appropriate to confirm what you’re seeing. Additionally, it’s worth noting that thermal imaging cameras are unable to see through walls and objects, but rather, they only pick up what’s reflected off them.

Choosing and purchasing a high-quality thermal imaging

It’s crucial to use a high-quality product to ensure that you detect and record accurate measurements. A big difference between different types of thermal imagers are the resolution and clarity of the images they provide.

1. Understand Resolution and Image Clarity

One of the most significant differences between thermal imaging cameras lies in their resolution and image clarity. The resolution of a thermal camera is determined by the number of pixels in its detector array, commonly expressed as dimensions (e.g., 320 x 240).

• Higher resolution cameras capture more data points, resulting in sharper images and greater accuracy in detecting small temperature differences. These are ideal for detailed inspections, such as detecting electrical faults or medical diagnostics.
• Lower resolution cameras, while more affordable, may produce blurry images and struggle to distinguish fine temperature gradients.

For tasks requiring precision, such as industrial maintenance or scientific research, investing in a camera with a higher resolution, such as 640 x 480 or above, is recommended.

2. Evaluate Thermal Sensitivity

Thermal sensitivity, or Noise Equivalent Temperature Difference (NETD), measures a camera’s ability to detect minute temperature differences. Cameras with a lower NETD value (e.g., <50 mK) provide more detailed and accurate images, which is crucial for identifying subtle issues like small leaks or insulation defects.

3. Opt for a Wide Temperature Range

Different applications require cameras with varying temperature ranges:

• For general building inspections, a range of -20°C to 150°C might suffice.
• For industrial applications, such as monitoring machinery or kilns, a camera capable of measuring up to 2000°C could be necessary.

Ensure the camera’s range aligns with your specific use case.

4. Check Lens Options and Field of View (FOV)

Thermal cameras often come with interchangeable lenses:

• Wide-angle lenses are ideal for surveying large areas, such as building facades.
• Telephoto lenses are better for focusing on distant or small targets.

The field of view (FOV) is equally important, as it determines how much of the scene the camera captures in one image.

5. Analyze Display and Software Features

A high-resolution screen and intuitive interface can significantly enhance usability. Additionally, ensure the camera comes with software that allows for advanced image analysis, reporting, and integration with other tools.

6. Consider Durability and Build Quality

For fieldwork or harsh environments, select a thermal camera with:

• Rugged, waterproof housing.
• Shock resistance to withstand drops or vibrations.
• Compliance with standards such as IP67 or MIL-STD-810.

7. Compare Calibration and Accuracy

High-quality thermal cameras undergo rigorous factory calibration to ensure measurement accuracy. Look for models that provide an accuracy of ±2°C or better for reliable results.

8. Factor in Connectivity and Data Storage

Modern thermal cameras often include features like:

• Wi-Fi or Bluetooth for wireless data transfer.
• Ample onboard storage and compatibility with external memory devices.
• Cloud integration for real-time data sharing.

9. Budget and Manufacturer Reputation

While high-quality thermal imagers may come with a higher price tag, their reliability and accuracy often justify the cost. Trusted brands are renowned for producing durable and high-performing devices. Investing in a well-known manufacturer also ensures better customer support and access to spare parts.

10. Evaluate Post-Purchase Support

Finally, consider the manufacturer’s warranty, repair services, and software updates. These aspects can significantly extend the life of your thermal camera and ensure it remains a valuable tool for years to come.

Thermal imaging is an impressive and compact method of identifying, measuring and visualising heat patterns, particularly in environments where there’s a lack of visible light. Armed with an effective and high-quality thermal imaging camera, there are a broad range of applications available, from industrial to health to research and science and so much more.

Here at Pyrosales we are proud to offer a wide range of thermal imaging cameras suitable for all kinds of applications, whether they be professional or hobbyist. Our suite of top-range thermal imagers are made by InfiRay, a globally active, high-tech company with an expertise in innovative measurement solutions that are guaranteed to meet your needs.