Thermal Imaging Guide: Types, Applications, Benefits & More

Thermal imaging has become an indispensable tool across numerous industries, offering a non-invasive method to visualise and measure heat. By detecting infrared radiation, it reveals temperature variations invisible to the naked eye, enabling proactive maintenance, quality control, and enhanced safety in diverse applications.

Thermal imaging is a non-contact technique that leverages the detection of infrared radiation to visualise and quantify temperature variations. All objects emit infrared radiation, a form of electromagnetic radiation with wavelengths longer than visible light, positioning it within the electromagnetic spectrum between visible light and microwave radiation. The intensity of this emitted radiation is directly proportional to the object’s temperature.

Thermal cameras are equipped with sophisticated infrared detectors, such as microbolometers, that capture this emitted radiation. These detectors convert the incident infrared energy into electrical signals. The signals are subsequently processed by the camera’s internal electronics, which map the intensity of the infrared radiation to corresponding temperature values. Finally, the temperature data is then translated into a visual representation, a thermogram, where different temperature levels are depicted by distinct color palettes or grayscale intensities, providing a real-time, visual map of thermal distribution.

As explained earlier, thermal imaging relies on infrared radiation, which resides within the electromagnetic spectrum and spans wavelengths from approximately 700 nanometers to 1 millimeter. Infrared radiation is emitted by all objects with a temperature above absolute zero, with the intensity of the emission directly proportional to the object's temperature. This principle allows thermal cameras to translate emitted infrared energy into measurable temperature values.

Thermal images, or thermograms, are visual representations of temperature distributions. These images employ colour scales to depict varying temperature levels. The precise colour-to-temperature mapping, or colour palette, can be adjusted within the thermal imaging camera's software to optimise visualisation for specific applications.

Here's a breakdown of typical colour scale interpretations:

• White/Brightest Yellow:
  • Represents the hottest areas within the captured scene.
  • Indicates the highest levels of infrared radiation and, therefore, the highest temperatures.
  • Often signifies points of critical heat or potential thermal anomalies.
• Red/Orange:
  • Indicates areas of significant heat, though not necessarily the absolute hottest.
  • Represents elevated temperatures and substantial infrared emission.
  • Often used to highlight areas of concern or activity.
• Yellow/Green:
  • Represents moderate temperatures and a transition between hot and cool areas.
  • Indicates a more neutral thermal state, where temperatures are within a normal operating range.
  • Can be a baseline temperature.
• Blue/Purple:
  • Represents cooler temperatures and lower levels of infrared radiation.
  • Indicates areas of minimal heat or potential cold spots.
  • Often used to identify areas of heat loss or insulation issues.
• Black/Darkest Blue:
  • Represents the coldest areas within the captured scene.
  • Indicates the lowest levels of infrared radiation and, therefore, the lowest temperatures.
  • Often signifies points of extreme cold or areas where minimal heat is present.

Several factors can influence the accuracy and interpretation of thermal images:

• Emissivity: This property describes an object's ability to emit infrared radiation. Materials with high emissivity, such as matte black surfaces, emit radiation efficiently, while materials with low emissivity, such as polished metals, emit radiation poorly.
• Reflectivity: Highly reflective surfaces can reflect infrared radiation from surrounding objects, potentially introducing inaccuracies in temperature measurements.
• Ambient Temperature: The temperature of the surrounding environment can influence the thermal radiation detected by the camera. It is therefore vital to understand and account for ambient temperature when analysing thermograms.

These are the key components of a thermal imaging camera that allows them to capture and visualise infrared radiation for a variety of uses and applications.

• Lens:
  • Specialised lenses, typically made of germanium or other infrared-transparent materials, focus the incoming infrared radiation onto the detector.
  • Unlike standard glass lenses, these materials allow infrared energy to pass through efficiently.
• Detector (Microbolometer):
  • The core of the thermal camera, the detector, or microbolometer, is an array of tiny sensors that absorb infrared radiation.
  • As the sensors absorb the radiation, their electrical resistance changes, creating an electrical signal.
• Processing Unit:
  • The processing unit receives the electrical signals from the detector and converts them into temperature values.
  • It then applies algorithms to enhance the image and map the temperature data to a color scale.
• Display:
  • The display shows the resulting thermogram, a visual representation of the temperature distribution. Typically, the display is a high-resolution LCD or OLED screen.

Here is a step-by-step breakdown of how the entire process works:

1. Infrared radiation emitted by objects within the camera's field of view enters the lens.
2. The lens focuses the radiation onto the detector array.
3. The detector sensors absorb the radiation, causing a change in their electrical resistance.
4. The processing unit converts these resistance changes into electrical signals and then temperature values.
5. The processing unit maps the temperature values to a color scale and generates a thermogram.
6. The thermogram is displayed on the camera's screen, providing a real-time visual representation of the temperature distribution.

Additionally, thermal imaging cameras are broadly categorised into two types which affect their use cases and ability to detect different temperature ranges.

The first type, cooled thermal cameras, utilise a cryocooler to reduce the detector's temperature to extremely low levels, enhancing sensitivity and accuracy, making them ideal for high-precision applications in scientific research and military operations.

Conversely, uncooled thermal cameras operate at ambient temperatures, offering greater portability and cost-effectiveness. While they may exhibit slightly lower sensitivity compared to their cooled counterparts, their practicality and versatility make them the predominant choice for a wide array of industrial and commercial thermal imaging camera applications.

Thermal cameras have a multitude of uses across diverse sectors, providing critical insights into thermal behaviour safely and efficiently. Here are some of the benefits of infrared imaging:

• Non-invasive: Thermal imaging allows for the inspection of equipment and structures without requiring physical contact or disruption.
• Real-time imaging: Thermal cameras provide instantaneous visual representations of temperature distributions.
• Preventative maintenance: Thermal imaging enables the early detection of potential failures in electrical and mechanical systems.
• Enhanced safety: Thermal imaging can detect hidden hazards, such as overheating electrical components or gas leaks.
• Improved efficiency: Thermal imaging helps optimise energy usage by identifying heat loss in buildings and equipment.
• Cost-effective: By preventing failures and optimising energy usage, thermal imaging leads to significant cost savings.

There are many types of thermal imaging cameras in various form factors, which affects their uses, applications and what they can detect. Here’s how they can be categorised:

Based on Cooling

• Cooled Infrared Cameras:
  • Pros: Extremely high sensitivity and accuracy, capable of detecting minute temperature differences.
  • Cons: Higher cost, require a cryocooler, and are typically larger and less portable.
  • Applications: Scientific research, military applications, high-end industrial inspections, and specialised applications requiring maximum sensitivity.
• Uncooled Infrared Cameras:
  • Pros: Lower cost, more portable, and operate at ambient temperatures.
  • Cons: Lower sensitivity compared to cooled cameras.
  • Applications: Industrial maintenance, building inspections, security, and a wide range of commercial applications.

Based on Wavelength

• Long-wave Infrared (LWIR):
  • Pros: Excellent for general-purpose thermal imaging, effective in various environmental conditions.
  • Cons: Lower resolution compared to shorter wavelengths.
  • Applications: Building inspections, security, and general industrial maintenance.
• Mid-wave Infrared (MWIR):
  • Pros: Higher resolution and sensitivity compared to LWIR, effective for detecting higher temperature variations.
  • Cons: More expensive than LWIR, and can be affected by atmospheric conditions.
  • Applications: High-temperature industrial processes, gas detection, and specialized military applications.
• Short-wave Infrared (SWIR):
  • Pros: High resolution and sensitivity, useful for specific material analysis and high-temperature applications.
  • Cons: Most sensitive to atmospheric conditions, and most expensive.
  • Applications: Semiconductor inspection, laser beam profiling, and high-temperature process monitoring.

Based on Form Factor

• Handheld Thermal Cameras:
  • Pros: Portable and versatile, suitable for on-site inspections and field applications.
  • Cons: Limited range and resolution compared to fixed-mount cameras.
  • Applications: Maintenance inspections, building diagnostics, and field service.
• Fixed-mount Thermal Cameras:
  • Pros: Continuous monitoring, high resolution, and integration with automated systems.
  • Cons: Less portable, require installation and integration.
  • Applications: Process monitoring, security surveillance, and automated inspection systems.
• Smartphone Thermal Cameras:
  • Pros: Highly portable and convenient, integrates with mobile devices.
  • Cons: Limited resolution and range, primarily for basic thermal imaging.
  • Applications: Quick inspections, DIY projects, and personal use.
• Drone-Mounted Thermal Cameras:
  • Pros: Aerial inspections, access to hard-to-reach areas, and wide-area coverage.
  • Cons: Requires drone operation skills, subject to drone regulations, and can be affected by weather conditions.
  • Applications: Infrastructure inspections, search and rescue, and agricultural monitoring.

Thermal imaging camera applications are widespread in industrial settings, providing invaluable insights that enhance efficiency, safety, and productivity. Here are some common uses of thermal cameras across different sectors:

• Building Inspections: Thermal imaging is crucial for detecting insulation deficiencies, air leaks, moisture intrusion, and structural issues in buildings. This helps improve energy efficiency, prevent damage, and ensure occupant comfort.
• Healthcare: Thermal imaging camera medical applications include detecting inflammation, circulatory problems, and even certain types of tumors. This non-invasive diagnostic tool aids in early detection and treatment planning.
• Industrial Applications: In manufacturing and industrial settings, thermal imaging is used for predictive maintenance, quality control, process monitoring, and electrical inspections. This ensures smooth operations, prevents costly downtime, and enhances safety.
• Security and Surveillance: Thermal imaging enhances security by detecting intruders in low-light or no-light conditions, monitoring perimeters, and identifying potential threats.
• Firefighting: Thermal imaging allows firefighters to see through smoke, locate victims, and identify hotspots, enabling them to navigate safely and effectively in hazardous conditions.
• Research and Development: Thermal imaging aids in research and development across various fields, from material science to aerospace engineering. It enables the visualisation and analysis of thermal phenomena, facilitating innovation and product development.
• Law Enforcement: Thermal imaging assists law enforcement agencies in search and rescue operations, surveillance, and evidence collection. It is a tool potentially used to locate suspects, track movements, and identify hidden objects.

Selecting the appropriate thermal camera is crucial for ensuring effective and efficient use across various applications. Consider these key features to match the thermal imaging camera's capabilities with specific needs.

• Resolution: Higher resolution cameras provide more detailed images, allowing for better identification of thermal anomalies.
• Temperature Range: The camera's temperature range should be suitable for the intended application, ensuring accurate measurements within the expected temperature span.
• Thermal Sensitivity: Higher thermal sensitivity allows for the detection of smaller temperature differences, which is crucial for certain applications like medical diagnostics or scientific research.
• Image Quality: Image quality factors, such as sharpness, contrast, and noise levels, impact the clarity and interpretability of thermal images.
• Features: Additional features, such as image analysis software, reporting capabilities, and connectivity options, can enhance the functionality and usability of the camera.
• Budget: Thermal cameras range in price, so it's important to establish a budget that fits your desired features and capabilities.
• Application: The specific application, whether it's building inspections, industrial maintenance, or medical diagnostics, will dictate the necessary features and specifications of the camera.