Education Is Necessary Before You Waste Your Money and Have Unprotected Employees & Visitors From COVID-19 and Other Viruses
Novel coronavirus (COVID-19) has changed our lives and is headline news no matter where you live on the globe. The demand for thermal cameras to screen for elevated body temperatures (E.B.T.) has surged in recent months. The technology is currently deployed in airports, businesses, and other public places looking for signs of fever as an indicator of COVID-19 or other viruses, such as influenza.
Firstly, discard the handheld temperature devices; they are doing nothing definitively for protecting your employees, visitors, or vendors. Handhelds are not built for this use! Marketing con-artists have jumped on the social media bandwagon to make a buck telling you outrageous lies! Stop believing what you read on Facebook and Twitter and the offers they make you. Many thermal imaging cameras currently being marketed heavily for fever screening applications are not suitable for this application. For seventeen years, we have been at the forefront globally in not only detecting but diagnosing elevated body temperatures.
Thermal imaging can provide an adjunctive temperature measurement of body surface temperatures. It has been effectively deployed to assist with fever screening applications and is far more effective than other non-contact temperature measurement devices. However, there are limitations to the technology. These are limits of bolometer detectors that apply to all makes/models/brands, as well as most handheld temp guns and non-contact thermometers. There is a lot of misinformation in the public domain. Many videos of fever screening using thermal imaging cameras are showing up on the internet and the news. These often show a camera looking at a large number of people flowing through the camera's field of view. These systems would not be providing useful scanning and give a false impression of how thermal imaging is in use. At best, this approach may highlight individuals with an elevated skin surface temperature, which is not necessarily a good indication of elevated body temperature. Factors such as if the person is sweating, wearing makeup or a hat, or moving at a fast pace, can completely invalidate skin surface temperature measurements.
Following Ebola, SARS, Swine Flu, and other infectious disease outbreaks, like influenza, international standards around fever screening using thermography had rules and applications written. If you are planning on using this technology, for this application, within your business, the standards must be used to heavily inform the design of the testing methodology that is put in place - even if you cannot follow the means to the letter. There are many so-called screening systems installed, as we speak, that are completely ineffective and will lead to a false sense of security within an organization. https://www.iso.org/standard/69346.html IEC 80601-2-59:2017 Medical electrical equipment - Part 2-59: Particular requirements for the basic safety and essential performance of screening thermographs for human febrile temperature screening https://www.iso.org/standard/69347.html ISO/TR 13154:2017 Medical electrical equipment - Deployment, implementation, and operational guidelines for identifying febrile humans using a screening thermograph Some of the significant points are:
To retrieve a reliable indication of an internal core body temperature, a measurement at the inner corner of the eye (canthus) must be taken. The canthus is known to provide an excellent indicative core body temperature reading. From a thermography standpoint, to get an accurate measurement, you will need around 4x4 pixels covering the canthus. As a guideline, for a 320x240 resolution camera, the face of the individual needs to fill >75% of the image width to ensure enough pixel density for an accurate measurement.
The camera needs to look straight on at the face, hats, glasses, sunglasses, etc. removed so that the eyes are seen clearly. A Black Body reference device must be included within the frame of the camera, at the same distance from the camera as the face, so as to both face/eyes and the Black Body reference panel are in focus at the same time. Factors are controlled in an environment such as a passport screening gate or an entry turnstile. However, they are far more challenging to manage in an open environment. There has to be a single file filter toward the camera, but not to slow the process.
Notes on camera selection There is a lot of opportunistic marketing going on at the moment. Many sellers are pushing cameras for fever screening that are fundamentally not fit for the purpose. Please keep in mind that with any camera, from any manufacturer, marketing doesn't change physics! Neither can fancy software or "A.I." for that matter. Anyone saying otherwise should be heavily scrutinized and fact-checked with reputable bodies such as professional thermography associations. Cameras are used for "thermal imaging," which are built with a different set of design objectives to cameras made for "thermography." i.e., radiometrically calibrated thermal imaging cameras that were designed to detect and measure temperatures rather than just producing a thermal image.
Such as Entrical Eyes Elevated Body Thermal/Radiometric Cameras. Let’s run through some thermography basics! The instantaneous field of view (iFoV) of a camera is the size of a single-pixel at a given distance from the camera. The measurement field of view (mFoV) of a camera is typically around 4 x iFoV, i.e. 4 x 4 pixels. The smallest object that the camera can measure the temperature accurately. A hot item smaller than this will appear cooler than its actual temperature. Note, the mFoV = 4 x iFov specification is for a thermal camera that has exceptional optics. Most thermal cameras do not have excellent optics.
? Tightly focusing the lens on an object is vital for getting an accurate temperature reading. Many cameras designed for security applications or lower-cost cameras designed for thermography applications have a "focus-free" design. Maybe fantastic for the camera ease of use. However, to achieve focus-free operation, compromises in the optical design need to be made. For example, focus-free lenses provide a complete depth of field so that objects close to the camera and far away can all be in "acceptable" focus at the same time. This may require an increase in f-number or similar design changes that reduce the quality of the image that can be achieved. In short, a thermal camera that does not have an adjustable focus lens is probably not suitable for thermographic screening applications.
? Manufacturing tolerances are not controlled that tightly in many facilities. Resulting in variation from the optical properties that the optical engineer intended during the design process, plus further variability between each lens produced. This is often paired with loose quality assurance and calibration standards. A lens that has an acceptable image to the eye may be perfectly suitable for security applications. Still, if it is not within tight design parameters, then it is likely not ideal for temperature measurement applications.
? Longwave infrared (LWIR) thermal imaging lenses have traditionally manufactured of germanium, with high-quality antireflective coatings. Germanium is an expensive raw material, and machining costs are high. The adoption of thermal imaging within the security industry has seen a dramatic fall in thermal camera prices. A large part of this has been as a result of the move away from germanium lenses to lenses made of chalcogenide or other similar materials, which can be mass-produced for much lower costs. These materials often don't refract longwave infrared radiation as well as germanium, meaning there can be more dispersion between the 7μm and 14μm wavelengths that the microbolometer is sensitive to. Making the image focus "soft." The impact from a thermography standpoint is that the requirement for mFoV can become 5 x iFoV or larger.
Now let’s discuss the application. First, let’s assume the canthus of the eye is the “hot spot” that we need to measure. The canthus is at most 0.118 inches (3mm) across as a measurement spot size. Then let's assume that our camera has perfect optics, and we need an mFoV of 3x3 pixels to get an accurate temperature measurement. Giving us an iFoV of 0.039 inches x 0.039 inches (1mm x 1mm,), i.e., each pixel is a 1mm high and 1mm wide square at the distance of the face we are measuring. Since the mFoV is non-negotiable, this means that the cameras field of view will vary with the resolution of the camera, for example:
? A 640x480 resolution camera can have a field of view no more extensive than 25.196 inches (640mm) (horizontal) by 18.897 inches (480mm) (vertical).
? A 12.598 inches x 9.448 inches (320x240) resolution camera can have a field of view no more extensive than 12.598 inches (320mm) (horizontal) by 9.448 inches (240mm) (vertical).
? A 10.078 inches x 7.559 inches (256mmx192mm) resolution camera can have a field of view no more extensive than 10.078 inches (256mm) (horizontal) by 7.559 inches (192mm) (vertical).
Keep in mind that the above is a best-case scenario, assuming perfect optics, which will not be the case in the real world. This is the reason that accurately screening multiple people from across a room is just not possible, irrespective of the amount of snake oil in the sales pitch. As a minimum, a camera with 320x240 resolution and focusable optics should be used. The face of the person being screened should fill most of the camera's field of view. This aligns with the statements buried deep in the user manual for cameras like the FLIR C2/C3 Tempscreen that states, “The distance to the face should be adapted so that the face covers more than 75% of the image width”, even if this is not the workflow that is portrayed in many videos and photos of these cameras in use. Camera measurement accuracy The same rules that apply to standard thermography applications apply to fever screening. It is straightforward to enter incorrect values for emissivity, or other settable parameters, into a camera. Sticking to the fever screening application, there are two approaches to temperature measurement used, each addresses the error in measurement accuracy of the camera in a different way: ? Absolute temperature threshold, e.g., a measurement of >99.32°F (>37.4°C) detected ? The average rolling method, e.g., an individual’s temperature is >33.8 >1°C higher than the average of the last ten people screened Both have different camera requirements and configurations, which are discussed separately below. The absolute temperature threshold method.
Most thermal cameras will have an absolute measurement accuracy stated as something like “the greater of ±35.6°F / ±1% (±2°C / ±2%) of reading”. When we are talking about an E.B.T. tolerance of around 1°C, this accuracy is not sufficient. To utilize these cameras, we can place a Black Body reference panel within the field of view of the camera. This Black Body is a near perfect emitter of thermal energy that the camera can measure the temperature of very accurately. Camera focus is essential to temperature measurement accuracy. It is crucial to make sure that the Black Body is at the same distance from the camera as the face of the screened individual. It is ensuring that both the face and the Black Body can be in sharp focus at the same time. It is also vital that the Black Body reference panel is large enough for the camera to measure very accurately; size larger than 10x10 pixels should be used as a minimum guideline.
The measured temperature of the Black Body can then be used to provide a temperature correction offset to the camera. If this approach is taken, then the measurement accuracy of the camera will be in the order of 5x-10x the NETD specification. Thermal sensitivity or Noise Equivalent Temperature Difference (NETD) describes the smallest temperature difference you can see with the camera. The lower the number, the better the thermal sensitivity of the infrared system. https://www.flir.com.au/support-center/Instruments/how-is-nedt-measured/ Thermal cameras designed for security applications often have a NETD as high as 150mK. To be suitable for a screening application, the NETD of the camera should be no greater than 50mK. Even if a camera with 100mK NETD is used with a Black Body reference panel, the measurement error will be around 10x100mK = 33.8°F (1°C,) which is before we factor for any variability in the Black Body itself. This is not suitable for screening applications. It is also worth noting that the way this is calculated varies between manufacturers. Cameras from low-cost manufacturers may be hiding low sensitivity by taking NETD at 122°F (50°C) instead of the industry-standard 86°F (30°C.) There are some other considerations that need to be factored. ? Linearity across the detector is essential. Thermography cameras correct themselves with a non-uniformity correction (NUC) shutter. https://www.flir.com.au/discover/professional-tools/what-is-a-non-uniformity-correctionnuc/ Cameras designed for security applications minimize the number of NUC cycles, as this causes the image to freeze for a few seconds each time it occurs, which is not ideal if that is the moment when the bad guys are sneaking past the guard. However, for temperature measurement applications, it's essential that NUC cycles are performed regularly to optimize the linearity of the image and minimize measurement drift over time. If the temperature of a Black Body is tracked between NUC cycles, there will be some drift in the measurement over time; this will result in a "sawtooth" pattern in the temperature measurement. With a high-quality thermography camera, the peak-to-peak change in this sawtooth will be <0.32.18°F (<0.1°C.) With a camera that is optimized for security applications with "radiometry" functionality added on, the peak-to-peak sensor drift over time can be <0.32.18°F (<0.1°C.) This is not suitable for screening applications where repeatability across individuals is critical. As a thermography camera is coming up to steady-state operating temperature, it will NUC more frequently; it is recommended that for screening applications, the camera is running for around 10 minutes before screening commences. ? Optical artefacts, such as vignetting, can cause temperatures at the edge of the frame to differ from temperature measurements at the centre of the frame. Good quality thermal camera optics should minimize this.
Still, cameras designed for applications where some vignetting does not matter (like cameras for security purposes) often have terrible optical artefacts present. They can measure >35.6°F (>2°C) different between the centre of the image and a corner of the picture. This is problematic if the Black Body is placed at the edge of the image, and the face is in the centre. In recent weeks there have been numerous thermal imaging systems entering the market targeted at COVID-19 screening applications. Many of these cameras have incredibly high accuracy, stated on their datasheets, for example, ±0.1°C. These types of statements raise alarm bells for most professional thermographers. The way that some manufacturers are justifying these accuracy claims is by using the NETD of the camera, as the accuracy, for cases where an in-frame Black Body reference panel is present. This is not correct for several reasons. For example, NETD is calculated using an average of all pixels and may not be representative of any individual pixel, including the pixels that are located over the target being measured. It also assumes that the Black Body reference panel has perfect stability and no temperature uncertainty, this is not the case in the real world. It is worth highlighting that the calibration of the camera varies with the ambient temperature and the temperature of the sensor and optics. High-quality thermography cameras are calibrated across their operating temperature range to ensure the calibration is valid under all operating conditions. Many cameras are not and will be calibrated at a single operating temperature only. The calibration certificate provided with your camera should state the testing conditions and limitations for the calibration. It should reference traceable standards (NIST, etc.) for any radiation sources used during calibration.
Screening system configuration: ? We mount the camera at head height and mark the floor where people can stand 4’6” inches (1.4m) in front of the camera. Giving us a mFoV of 0.507 inches (2.9mm) and a horizontal field of view 24.016 inches (61cm) wide with the lens stated.
? We mount the black body reference panel on a stand next to where the individual's face will be at 4’6” inches (1.4m) distance from the camera. The Black Body is pointed directly at the camera.
? A measurement spot within the camera software is placed in the centre of the Black Body reference panel, and appropriate local parameters adjusted (emissivity, distance, etc.).
? A measurement area box covering the area of the face is then configured.
? Individuals are asked to step up to the screening location one by one, remove hats, glasses, goggles, etc. and then stand still while an image is captured. This is fast, with less than a second required.
? The camera logic is then configured something like: o ?T = T(Area Max) - T(Spot) o Alarm if ?T > 2.4°C It will alarm on the condition that any person’s temperature measurement is above 99.32°F (37.4°C.) A temperature of 99.5°F (37.5°C) at the canthus is typically recommended as an excellent point to start screening for potential fever. The error in the measurement is <0.7°C (10x 30mK NETD + 0.4°C B.B. uncertainty); with a good quality camera, lens, and Black Body, the error should be significantly less than this. It is essential to understand that all the camera is indicating is the presence of elevated body temperature (E.B.T.). The camera is not diagnosing an individual as having a fever, COVID-19, or any other medical condition. Once the system indicates an E.B.T., procedures need to be put in place to allow an appropriately qualified and licensed medical practitioner to assess the individual. How to use the “Rolling Average” average screening method All of the same requirements regarding iFoV, mFoV, and working distance discussed above are valid to the average rolling method. The most crucial factor, mainly if using a handheld camera, is consistency, i.e., distance to the person, measurement parameters, etc. Summary Thermal imaging technology is brilliant. It has many great applications and can be used effectively for Elevated Body Temperature (E.B.T.) screening applications. However, it is vital to understand the limitations of the technology. There are a lot of thermal cameras that were never designed for accurate temperature measurement, which are being hastily rebranded and marketed as a “coronavirus detection camera.” No camera can detect coronavirus. The camera can only detect and measure surface temperature differences, which can be an indication of elevated body temperature and issue with that person. Only a licensed medical professional can determine if a “hot” individual is experiencing an abnormal medical condition. Entrical Eyes Frontline Elevated Body Temperature Thermal Radiometric Cameras measure the ‘Canthus,’ the tear duct, which is the most stable relative core temperature externally.
For accurate E.B.T. applications, a ‘Blackbody’ is necessary. "The blackbody instrument is a calibration device," states Nicholas Ashton, E.V.P., Strategy, Entrical. “Entrical Eyes E.B.T. calibrates every second to ensure the accuracy of the device and readings.” “A blackbody device is required, as it provides a constant reference temperature to assure accurate temperature monitoring during continuous operation,” Ashton adds. “To assure the cameras focus on the correct part of the body the tear ducts (Canthus), it is crucial that the camera and blackbody are both mounted at the recommended height and distance. It’s also essential that the person faces the camera straight on and removes any facial or headgear such as glasses, hats, hair, or anything else that obscures the eye area. Keeping the eye area free from accessories is important because the inner canthus is the most accurate way of measuring a person’s internal body temperature.” Also, people should walk through a stanchion in a single-file line, Ashton notes. “We think there’s a responsibility to make sure that performs timely and accurately, and we take that very seriously,” Casey Roussel, C.E.O., Entrical states. What is essential to know, Roussel says, is when it comes to thermographic radiometric temperature detection, there is a global standard — the I.E.C. 80601-2-59: 2017. “This standard is what drives the level of accuracy necessary to obtain what you’ll see in many specifications as a plus or minus 0.3 degrees C level of accuracy or just over 0.5 degrees F. No matter what you’re looking at in terms of thermographic radiometric detection, that is as good as it gets.
Ian Hunt, Entrical, Facial, and Thermal Radiometric Camera V.P., states, “We looked at the FDA 510(k) guidelines for thermographic solutions, which clearly state the use cases to which a device would be considered medical. And there are three criteria. The first two have to do with use in healthcare settings, like hospitals and clinics. But the third is if you’re using this device for diagnostic purposes in a non-healthcare setting, and the example they give specifically is a place like an airport, schools, hospitals, or arenas.” Many of these solutions get tied up on the words ‘diagnostic purposes’ and try to stay away from saying that, Hunt explains. “When the use case itself is using it for screening — at which point you would then send somebody to a next-level screening for confirmation of a fever? Which is what most customers are asking for today — clearly by the [U.S. Food & Drug Administration (F.D.A.)] that makes this a medical device. We comply with the F.D.A. stipulation, especially under the Emergency Covid-19 rules. Hunt adds that a concerning element is the F.D.A.’s specific guidance document, released in April 2020, which defines the COVID-19 thermographic device guidance. “Under that directive, it gives permission and relaxes the 510(k) approval so that people can start shipping thermograph solutions without the need to apply for a specific emergency use act from the F.D.A.,” he says. “That guidance will eventually expire, and the F.D.A. will go back to its routine enforcement of the 510(k) once the state of emergency changes if it ever does.
How many of them will be able to pass a 510(k) and meet the accuracy standards of a medical device? That is an essential consideration of customers who are investing in the security and safety of employees and visitors alike.” The confusion of what people have or have signs of, with a rise in temperature, is key to protecting the facility. Stop letting the fox in the hen house. Hunt points to resolution, camera stability (meaning the camera measures consistently and accurately over different environmental ranges), focus, and distance of the subject from the camera. “Some systems measure temperatures on foreheads, but we know, and research backs up that those are very susceptible to environmental factors,” Hunt says. He describes a scenario in which a person is wearing a hat and then removes their hat for screening. Otherwise, it would produce a warm band on their forehead that can read hotter and create a false positive. “How you take the measurement impacts the accuracy of the system,” Hunt says. “Studies show the best correlation of core body temperature is measuring the temperature at the inner corner of the eye, the ‘Canthus’ or tear duct.” “Our global clients wish to bring about some peace of mind when they decide to reopen the business,” says Ashton. “They understand that fever is not always present, known to be present 70% in people with the coronavirus, but it brings other levels of security such as the face recognition and no-mask indicator.” Additionally, to recognizing the elevated temperature, Entrical can detect if the user is wearing a mask and knows the face (even with the mask on) to gain approved entry to the facility. It was in March 2020; we knew we had to develop a new camera solution that could be mobile, static, and cost-effective. Entrical Eyes Frontline Elevated Body Temperature Thermal Radiometric Cameras are now released. Over the coming days, we shall demonstrate, invite new and existing clients on how Entrical Eyes has changed the demands of health security today. “We do think the security industry must pivot and provide solutions for the new world,” says Roussel. Many businesses are in various stages of reopening; Entrical has raced methodically for a secure solution that exceeds the guidelines which are in demand today. “We believe that there is going to be a fundamental change in people’s behaviour in the future,” Ashton foresees. “Even when COVID-19 is under control, there will continue to be an elevated perception of risk to infectious disease. A significant demand has emerged for this technology, which brings you into line with your Duty of Care. Buy Cheap, You Buy Twice, Buying Cheap Now Costs You Lives! Please contact us for a full virtual Zoom demonstration of this unique, cost-effective solution and how you must increase your frontline protection. The front and back doors are the keys!