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Thermal Imaging Sensors for Fever Detection

individuals at the same time, from a distance, Typical systems for temperature scanning HkOpenLab/solutions/2021E001.pdf.
without stopping them — but is it really include both visual and thermal imaging sen- At the reference design’s core is the novel
enough? Clearly not. sors. The visual image stream is analyzed for thermal imager by Meridian Innovation
For starters, the detectors can sense only the face detection and face-mask detection, and the (meridianinno.com). The imager is mass-
temperature on the surface of the skin. Sim- resulting regions of interest are mapped to the produced via a CMOS/MEMS technology and
ilarly to the forehead thermometer, the core thermal data stream for temperature analysis. is a hybrid between conventional microbo-
body temperature must be calculated based on The result of such processing is shown lometers and bulk thermopile in terms of
some biophysical model of the human body. in Figure 5, where three people are iden- pixel design. Other than the thermal imager,
The question that now arises is which pixel to tified in a given pair of visual and thermal the reference design includes an ambient
take as representative of the skin temperature frames, and each person’s estimated core sensor and a time-of-flight sensor to estimate
of interest. This is a non-trivial matter because body temperature is annotated on the visual the distance to subjects. It benefits from AI-
the thermal imager resolves the face of a frame. However, scanning for fever becomes enhanced application software, which
human in multiple pixels, with temperature significantly more difficult when the privacy improves the accuracy of the thermal readout
readouts that can vary by more than 1°C. of the individuals must be preserved and a and core body temperature calculation, as
Additionally, factors such as imperfections visual image sensor therefore cannot be used well as the quality of the thermal image for
in the lens; the viewing angle between the on the system. In that case, the entire process visualization. The choice of cost-effective
camera and the subject; and the presence of a of subject detection and subsequent core body components together with the software
face mask, a face-occluding hair style, glasses, temperature estimation must be based solely development kit, which helps with the most
etc., all contribute to some inaccuracy in the on the thermal video stream. significant hurdles — including the calcula-
temperature readout and make its interpreta- More details on the principle of how it tion of core body temperature — lowers the
tion a lot more complex than in the case of a works can be found in the “Research Note on barrier for adoption of the design and helps
simple forehead or in-ear IR thermometer. Fever Detection,” by Dr. Stanislav Markov of to meet the demands for thermal imaging
Here is where the crucial role of thermal Meridian Innovation, at erp.meridianinno.com/ cameras that can detect a fever.
image processing and analytics comes into documents/On_Fever_Detection_english.pdf.
play. The various inaccuracies are mostly of CONCLUSION
systematic character and can be compen- REFERENCE DESIGNS Thermal imaging sensors are now readily avail-
sated for, taking into account the “excess” The imperative for a timely delivery of a able and affordable for mass-market products.
information available in the thermal image. thermal imaging camera for the detection of Accessible reference hardware designs and
This, however, makes the design of a thermal elevated temperature and the complexity of software solutions facilitate adoption of the
imaging camera for fever detection a rather building a good solution, as described above, technology and enable a fast development
complex endeavor, requiring a detailed have led to joint efforts to provide a number cycle for thermal imaging cameras, including
understanding of the thermal imaging sensor of reference designs for OEMs and ODMs. An cameras for automatic fever detection. Such
properties, a good grasp of thermography and example of such a reference design is pro- products can help manage the pandemic and
some biophysics, and, of course, a proficiency vided by Arrow Electronics and is presented present a compelling story in which innovative
in image and data analytics. in greater detail at www.arrowopenlab.com/ technology fosters safer and better living. ■

www.eetimes.eu | NOVEMBER 2021