As government and business leaders start to talk about “returning to normal,” and looking to thermal cameras to help, questions remain about how and whether the latest technology can help prevent the spread of COVID-19.
Across industries, everyone is looking for the right tools to help detect, slow and eventually stop SARS-CoV-2, the virus that causes COVID-19. By now we’ve all come to recognize that resuming operations in any way will require demonstrating measures to protect the health and wellbeing of people in a variety of situations, including travel and work.
One proposed solution is thermal scanners. Unlike most medical imaging approaches, infrared (IR) thermography doesn’t require irradiation or expensive equipment, and presents no health hazard. Infrared radiation emitted from our skin can be detected and used along with information about the ambient environment to estimate core body temperature — which may indicate someone is running a fever, a common early symptom of COVID-19. While thermal cameras can’t detect a virus or a specific infection, they can help by quickly narrowing down a large pool of possibly infected individuals. And today, this represents the only viable non-contact mass screening approach for fever. The accuracy of the infrared system can, however, be affected by human, environmental and equipment variables. Understanding this multitude of variables — including the ways in which the science, technology and applications themselves interact — will help both users and system makers deliver the best results.
Consideration #1: Think about the method
Thermal detection has been used for fever detection for 20 years now. While older thermometers and thermal cameras, including the type used to detect a different coronavirus, severe acute respiratory syndrome (SARS), had their weaknesses, newer generations deliver significant performance improvements. More intelligent systems now offer features such as real-time calibration to ambient temperature with sub-degree °C accuracy, providing more accurate readings far more quickly than older generations.
Newer camera systems are also more user-friendly and more reliable, featuring automated target recognition, improved resolution, pairing with a visible-light camera, automated alarms for febrile cases, and clearer outlining of hot spots. This higher degree of granularity improves insight, allowing for a more efficient and faster screening process, and provides on-site health professionals with necessary information to take additional steps when required.
Advanced image processing features in new radiometric thermal cameras.
Consideration #2: Know your baselines
Because the environment can influence temperature measurements, some system makers have devised different ways to establish functional baselines. An early approach, recording a population baseline at each site on each day, proved too time- and resource-intensive. A newer approach, using a reference temperature source, or black body, offers evolutionary improvement. Designed to maintain itself at a specific temperature, the black body device allows the thermal camera system to automatically calibrate. Even better is a radiometric camera, which can intepret the intensity of an infrared signal reaching the camera. This requires more rigorous design and testing by the manufacturer, but it delivers much more precise measurements.
Diagram of a fever detection system with black body emitter
Consideration #3: Looking in the right place
While thermal cameras can only detect surface temperatures, different parts of the human body more closely correlate with body temperature. Based on recent scientific research, the most reliable spot in the human face is the canthus, the small corners over the tear duct of your eye where the upper and lower eyelids meet. This kind of precise targeting requires accurate pixel calibration capabilities.
The best surface target for estimating core body temperature: the canthus at the inner eye
Consideration #4: Checking your performance
Operating an IR fever screening system in the lab is one thing, but out in the field, the situation becomes more complex. Users need a camera system that is reliable and stable when it comes to critical performance factors like resolution, sensitivity and frame rate. Understanding the performance considerations when imaging a subject at a distance, for example, and realizing the minimum number of pixels required to get an accurate measurement are both essential in staging a fully optimal fever-detection platform.
Consideration #5: Finding your way in the “wild west” of thermal imaging in early 2020
People from the many industries that have been devastated by this pandemic – including travel, sports, manufacturing, food and hospitality, and entertainment — are looking for ways to reopen businesses safely while reducing the probability of a second wave of COVID-19. Deploying technology such as IR fever screening systems as part of a range of preventative measures will hopefully support that effort.
As is the case with any promising emergent technology, there is a fair degree of chaos around the nuanced considerations of system design and performance. What standards apply to IR fever-screening devices? Which are being enforced? Who makes them? Will they work? IR camera manufacturers such as Teledyne DALSA and the expert system integrators we work with can play an important role in helping manufacturers and integrators to navigate this chaos, enabling us to work together to potentially save lives.
Jean Brunelle, product manager for infrared imaging, is a technical leader in sensor integration at Teledyne DALSA. He works on developing new image correction and calibration algorithms as well as qualification and production tests for the company’s visible and LWIR lines of digital cameras. Having earned a bachelor’s degree in engineering physics and a masters in surface chemistry, he has a passion for all things sensors, from how they work to how they are fabricated and used. His focus for the past few years has been on micro-bolometer-based LWIR cameras. Most recently, he was involved in the development and testing of Teledyne’s very own WLP micro bolometer and its integration into a thermal camera.
Teledyne DALSA is a member of MEMS & Sensors Industry Group (MSIG), a SEMI technology community that enables the MEMS and sensor industry to address common challenges, innovate and accelerate business results.