How do you see what you can’t see? With thermal imaging, you view the radiation or infrared wavelengths emitted by objects.
Infrared wavelengths — too long for the human eye to detect — are part of the electromagnetic spectrum perceived as heat. Thermal imaging technology converts this temperature information into images called thermograms, which use a color palette to indicate the range of temperatures present.
Interest in thermography and its many applications has exploded. Infrared technology has been engaged for surveillance purposes in the military and law enforcement. Infrared cameras have helped to detect people infected with viral diseases at an early stage. According to a report from FLIR, infrared cameras used at airports helped identify arriving travelers contaminated with the swine flu in 2009. Medical professionals employ thermography to expose possible tumors, inflamed tissue, and more. Dentists use thermal imaging to diagnose temporomandibular joint disorder, or TMJ. Emergency responders, such as firefighters, use thermography to find people trapped in fires by providing an image through the smoke. More recently, luxury car brands have placed the cameras in their front grilles or bumpers so that drivers can see more safely at night.
For industrial purposes, thermal imaging is used by building inspectors and maintenance personnel to assess loss of energy, both internally and externally. Building cameras are also used to reveal moisture and ventilation leaks. Industrial cameras spot issues in electrical or mechanical applications and help troubleshoot processes.
The versatility of thermal imaging is amplified by its ability to capture moving objects in real time and create images in dark areas. Because it is a noncontact technology, it can measure areas that may be hazardous or difficult to access. In comparison to infrared thermometers, which only measure one spot, thermal imagers scan the entire room or environment to determine, for example, if a circuit is overloaded.
Trends in Thermal Imaging
Emerging capabilities are expanding thermal imaging much further. FLIR’s André Rebelo, Global PR manager, explained where current research and development is headed.
“FLIR looks at the thermal imager as part of a diagnostic ecosystem. Rather than working in isolation to sense temperature abnormalities only, our latest technology integrates electrical test measurements to display a fuller diagnostic picture,” he said. “In many settings, if we can identify the source of the problem and communicate that information via images to decision-makers — managers and clients — repairs can be initiated much sooner. With connectivity now available to transfer this key data via Wi-Fi to an iPhone®, iPad®, Android®, or other personal device, work flow is accelerated. This increases efficiency and ultimately lowers costs resulting from potential downtime and hazards to employees.”
Just a few years ago, thermal imagers resided firmly in the domain of specialists with advanced training. Now, with the lower price points of many imagers, the technology is accessible to non-specialists.
“Like GPS devices, which use military-derived technology distilled into a consumer market, thermal imaging is becoming more and more available. Cameras previously priced at $10,000 are now a quarter of that. They’re easier to use out of the box and free introductory training is also available,” said Rebelo.
Refinements in resolution also continue. Resolution directly translates to image quality. Higher resolutions provide precise and reliable measurements of smaller targets from further distances, creating sharper images. The quality of the thermal image and its data is always determined by the detector resolution rather than the display resolution. As the thermal detector resolution increases, the image detail becomes clearer and the temperature at a single point is more accurate.
Similarly, Multi-Spectral Imaging (MSX) blends the built-in thermal image with a visible image.
“Our MSX functionality enhances clarity to display details such as labels or signage in an environment, providing necessary context. This helps to communicate malfunctions to nontechnical decision-makers because they can look at the image and reference exactly where the problem is occurring,” said Rebelo.
As with most technology, making it smaller and even more portable is on the horizon. Also, “in the future, we may see thermal imaging cameras appearing on smart phones. A user could use this camera to check a tire for possible overheating, which may cause it to burst, or perhaps to discover where heat is leaking out of windows and crevices at home.”
As potential functionality expands, so do the opportunities.
“Emerging technology — even more sophisticated cameras — are creating possibilities for other uses. Canine and equine veterinarians may use thermography to detect inflammation. In marine applications, infrared technology enhances night vision on ships so that operators can see through fog and smoke,” said Rebelo. “With advanced calibration for Optical Gas Imaging, the thermal imager can detect gases such as natural gas and carbon monoxide as well. Utilities can identify leaks of greenhouse gases used in high voltage equipment. This may reduce equipment failure and outage liabilities, not to mention preserving the environment. Miners can use the imagers to see the concentration of carbon monoxide in a confined area. This may prevent potentially fatal health hazards. Some utilities and petrochemical companies are adopting this advanced technology. The applications for it are expanding dramatically.”
Current Options in Functionality
Thermal imaging cameras vary in temperature range, thermal sensitivity (NETD), and resolution. Their temperature range is especially critical for industrial uses, which need a wider range to accommodate high-temperature equipment such as boilers, steam systems, and blast furnaces.
Thermal sensitivity or noise-equivalent temperature difference (NETD) measures the smallest temperature difference that a thermal imaging camera can detect in the presence of electronic circuit noise. Those with a low NETD can detect smaller differences and provide higher resolution images with increased accuracy. Thermal sensitivity is measured in milliKelvins (mK).
For a thermal imaging camera to be fully functional for an identified application, it requires specific functionality. All thermal imagers offer a full-screen infrared view for troubleshooting and analysis and are fully radiometric by measuring and storing temperatures at every point in the image. Other options include:
Visible Light Imaging for a digital photographic image to offer a reference to the equipment or environment being measured.
Picture-in-Picture (PiP) Imaging combines thermal and visible-light images by placing a framed thermal image over its corresponding visible-light photo. Some cameras have fixed Picture-in-Picture functionality while others provide more flexibility. With some, the frame is movable and sizeable.
Fusion/Blending Imaging blends the visible and thermal images together with a partial overlay of the equipment. This allows the user to choose how much of the image to reveal in enhanced detail. MSX takes blending to the next level by digitally processing a thermal image with crisp details from a visual image.
Infrared/Color Alarms display a visual image with infrared highlights for temperatures between, above, below, or outside of a user-programmed range. This allows for easy detection of trouble areas during inspections.
What is really necessary for a particular application? With so many options and price points, invest time in determining which model is the best fit. How does it rate in terms of accuracy? Does it include the type of reporting software that will expedite maintenance and prevent losses? Review the specifications and contact a technical specialist for guidance.
