What is thermal imaging?

The human eye is a wonderfully complicated and intricate organ. Our eyes are made to see visible light. This is the light that reflects off of objects and makes them visible to us. Light is a type of radiation and radiation itself comes in more variations than just the visible type.

Infrared thermography and thermal imaging is the process of visually depicting thermal radiation within the field of view of thermal imaging cameras and thermography devices. Thermal imaging allows us to see an otherwise invisible portion of the infrared spectrum.

Infrared and thermal imaging

Thermal imaging is a way of detecting heat signatures that are emitted from physical objects. By understanding infrared, thermal imaging devices can be used to detect the heat signatures of just about any objects.

Objects which are very hot can sometimes put off visible light. For example, consider a fork held over a flame until glowing red hot. At a lower temperature, the fork will not glow red but the heat can still be felt. This heat that can be felt is called infrared radiation. To describe infrared radiation from a human perspective, infrared radiation cannot be seen with our eyes but can be sensed by our skin.

There is some science involved when learning to better understand thermal imaging camera systems. Infrared radiation is part of the electromagnetic spectrum. This spectrum covers a wide range of items all the way from gamma rays and visible light (what humans can actually see) to infrared and even radio.

All objects in the universe emit infrared radiation at some level. Thermal imaging and thermography is essentially the science of seeing temperature by measuring the thermal radiation emitted from an object and converting the data to a visual image. Simply put, thermal imaging converts infrared information into a visible picture. This allows us to see things that we normally would not be able to. 

Our eyes see reflected light and are sensitive to specific parts of the electromagnetic spectrum (the visible part). Whereas thermal imaging cameras are sensitive to a portion of the infrared range of the electromagnetic spectrum. Thermal imaging cameras do not look in the visible portion of the spectrum. 

What is the difference between infrared and thermal imaging?

Infrared is a color that humans cannot detect. To see infrared light, infrared imagers and cameras are required. Infrared light has longer wavelengths than visible light and is emitted or absorbed by molecules when they change rotational movements. 

Infrared imaging refers to any imaging systems that operate in the infrared. Thermal imaging refers to an infrared imaging system designed specifically for the portion of the infrared range which is emitted by objects at or above room temperature (Wavelength of about 10 microns). At this wavelength, you see images typically associated with the term “thermal vision”. For example, people will be brighter than room temperature objects and running car engines will stand out etc.  

In the context of imaging devices, thermal cameras use radiation from the far-infrared region of the electromagnetic spectrum while IR night vision cameras use light from the much higher frequency near-infrared region. Both may seem like minor variants of “infrared” but the spectral ranges are quite different. Near-infrared is the light closest in wavelength to visible light and far-infrared is closer to the microwave region of the electromagnetic spectrum.

What is a thermal imaging camera?

A thermal imaging camera is simply a means of capturing and storing visually interpreted thermal radiation information. There are various types of infrared imaging solutions available depending on your application type. 

Although we refer to them as “cameras”, these devices are actually thermal imaging sensors. 

Thermal imaging camera sensors are a contact-free means of capturing and visually translating thermal infrared imagery.  These thermal imaging sensors are designed to be sensitive only to the far-infrared portion of the electromagnetic spectrum.

For precise quantitative data, infrared thermography cameras can be employed to measure and display temperatures within the field of view of the thermal imaging sensor. The best handheld thermal imaging camera systems are useful for general electrical or mechanical infrared thermography inspections. These devices are typically lightweight and resistant to the elements. 

Permanently installed (fixed) infrared thermography inspection cameras can be employed as an always-on industrial thermal imaging and condition monitoring solution. 

For simple detection using infrared thermal imagery without temperature measurements. High resolution thermal imaging cameras are available for general portable outdoor or for fixed installation security purposes. For example, the best thermal monoculars are widely used by security professionals or anti-poaching organizations as a lightweight, mobile thermal detection solution. Additionally, fixed thermal imaging security cameras are fast becoming the standard for long-distance perimeter intrusion detection.

What are thermal imaging cameras used for?

How can thermal imaging or thermography help? Most electrical or mechanical defects cause an increase in temperature. Thermal imaging is a very fast and clear means of capturing these temperature variations. Another consideration is safety, thermal imaging is a contact-free means of inspection and can be done at a safe distance and without disrupting production lines (equipment does not need to be shut down). Most importantly, anybody can take a picture using a thermal imaging camera system.

Below a shortlist of some applications for thermal imaging. However, note that thermal imaging is useful for any application where measuring thermal radiation is advantageous. 

• Plumbing professionals may use a thermal imaging camera for water leak detection.
• The use of thermal imagers for hunting.
• Anti-poaching organizations swear by the use of a thermal imaging camera for wildlife preservation.
• Businesses, airports, and other high-traffic establishments make use of fever screening human thermal imaging cameras.
• Although not required in South Africa (yet). Building inspection professionals often make use of a thermal imaging camera for home inspections and building inspections.
• Infrared imagery can also be used for thermal roof inspections.
• Thermal camera fire detection. Thermal imaging cameras can be used to detect fires at an early stage and thus prevent wildfires.
• Residential housing estates and agricultural installations are increasingly utilizing thermal imaging security cameras for perimeter protection.
• Thermal imaging camera sensors are being used as part of sensor suites in autonomous vehicles.

What blocks thermal imaging?

There are some instances where thermal imaging doesn’t work. At least not in the way you’d expect. You cannot use thermal imaging through walls or most surprisingly, glass. Glass allows visible light to pass right through but is opaque to thermal imaging. 

Much like glass, polished metal or Mylar surfaces act as a mirror for infrared radiation. Using a thermal imaging camera here will only show the reflected temperature of objects. This makes shiny metal is a very tricky material in the thermography industry. Metal that has been painted with a matte material or that has oxidized is much easier to measure using a thermal imaging camera system. 

Rain and fog can severely reduce the range of a thermal imaging camera due to scattering radiation from water droplets. However, in many circumstances, thermal imaging cameras penetrate fog much better than optical cameras and even the human eye.

What can thermal imaging see through?

Unlike in some science fiction movies, thermal imaging cameras are not x-ray cameras and they do not look through solids (No, you cannot use thermal imaging through walls). Interestingly enough, if you point a thermal imaging camera at a wall, it will detect heat from the wall. However, if something inside the wall causes a significant temperature difference, a thermal imager will be able to sense it.

Firefighters widely make use of thermal imaging equipment because it allows them to see through smoke. Due to the presence of soot particles, smoke is opaque to visible light but allows thermal radiation to pass right through. Much like glass, but in reverse.

Infrared thermal cameras may not be able to detect objects through the trunk of a tree but they are extremely useful when spotting people or animals in forested areas. Often employed to detect heat signatures in dense wilderness, search and rescue operations make extensive use of the capabilities of infrared thermal cameras.

Thinner opaque and transparent plastics also allow the passage of thermal radiation. However, this is only the case with thin plastic. Thicker plastics will block thermal radiation.

Most importantly, thermal imaging camera systems require no visible light to visualize heat. Making them completely impervious to darkness. 

More about Cape Thermal

Infrared and thermal imaging is not without limitation. However, thermal imaging camera systems present significant opportunities and potential usage cases across multiple industries.

Are you looking for the perfect device for your application or to further explore the capabilities of what infrared and thermal imaging have to offer? Cape Thermal offers a wide range of handheld thermal imaging devices to suit your needs.

Cape Thermal offers nationwide delivery on all purchases. All handheld thermal imaging device purchases are fully supported by the Cape Thermal technical team.

Visit our online store and shop for the best handheld thermal imaging.