THERMAL IMAGING


The tear ducts have been shown to be the area on the face most closely correlated with body temperature


g


thermal cameras cannot detect someone with elevated body temperature in a crowd. Termal cameras have low


spatial resolution – typically 320 x 240 or 640 x 480 pixels for this type of application – which means that the person has to be directly in front of the camera to get a reliable measurement from such a small area on the face as the tear ducts. Tarin told Imaging and


Machine Vision Europe: ‘Due


to the very small size of the inner canthus [tear duct], several pixels are required to measure that region accurately. We have determined that the approximate pixel size – projected onto the face – should not be much larger than 1.5mm/pixel. With thermal cameras having a relatively low spatial resolution of maybe 320 x 240 or 640 x 480 pixels, this implies that the image size should not be larger than about


500 to 600mm in width for a 320 x 240 pixel detector – twice that for the 640 x 480 resolution camera at most.’ Flir recently released its A400/A700 camera with a resolution of 320 x 240 pixels, which the company says it is prioritising for tasks that combat the spread of Covid-19. Andreas Zinssmeister, head of EMEA sales at Flir Systems, said Flir’s A-series, T-series or E-series are suitable for elevated skin temperature measurements. Te distance the camera can


be positioned from the subject depends on having enough pixels to get a reading across the tear ducts, but also on the lens. ‘As long as our application meets the minimum pixel over the smallest area of interest requirement, we can move further away,’ Tarin explained. ‘For example, with a 24d lens and a resolution of 320 x 240 pixels, I can achieve a scanning distance of about six to eight feet, or thereabout. Using a 14d lens, I can stretch that to 10 to 12 feet,’ adding that these are


Stuttgart’s Robert Bosch Hospital trials people-screening tech


A non-contact method to monitor people entering the Robert Bosch Hospital in Stuttgart for signs of coronavirus is being trialled by Fraunhofer IPA and Fraunhofer IAO. The Fraunhofer institutes


have set up an infrared camera to look for fever, in combination with a radar module that measures heart and breathing rates using microwaves. The equipment screens individuals at the entrance to the Robert Bosch Hospital. The research team is now


examining how precisely the testing procedure correlates with the data collected from staff in the entrance to the hospital, and whether the procedure is practical. It is hoped the new testing equipment will simplify the controls set up by the hospital


for those entering. It also minimises risk for staff as the measurements can be made at a two-metre distance. Along with screening people


for signs of Covid-19, the Fraunhofer scientists are using their equipment to analyse the movement patterns of people entering the hospital. The aim is to integrate this technology into the hospital’s admission process. Other institutes such as


Tübingen University Hospital and several coronavirus screening checkpoints in the area are also keen to use the new test method. Dr Urs Schneider, a medical


professional who works at Fraunhofer IPA, said: ‘We are convinced that we have developed a sound concept that can also be used when the coronavirus crisis is over.’


14 IMAGING AND MACHINE VISION EUROPE JUNE/JULY 2020 @imveurope | www.imveurope.com


‘It also has the advantage that it allows staff to pull the person aside to run further tests’


approximate figures and will depend on factors such as the pixel pitch of the detector. All of this means that it is best


to scan people one at a time in an airport security-style check to get an accurate reading, which also has the advantage that it allows staff to pull the person aside to run further tests if the camera does detect an elevated skin temperature. According to Tarin,


there are really only two legitimate screening set-ups for measuring elevated skin temperatures accurately with thermal cameras. Te first is to use a camera that uses a baseline reference and then compares all future subjects to the average temperature


Flir Systems


Fraunhofer-


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