Self-Compensation for the Influence of Working Distance and Ambient Temperature on Thermal Imaging-Based Temperature Measurement

Nowadays, body temperature screening is very important especially in the current global coronavirus disease (COVID-19) epidemic. It can be considered as the first step in monitoring the fever symptom if the body temperature is checked regularly. Aiming at alleviating the influence of working distance and ambient temperature disturbance, this article proposes and demonstrates a self-compensation technique that is built into our low-cost thermal imaging-based temperature screening system. The key idea relies on a combination of a 3-D depth sensor, an electronic temperature sensor, and a reference temperature for realtime data feedback and control. In addition, we obtain simple mathematical models for compensating the influence of ambient temperature and measuring distance variations. Experimental demonstration using a blackbody radiation source as an object confirms that the measured temperature under our self-compensation agrees very well with the blackbody radiation source, showing a very low standard deviation of 0.10 °C under 21.0 °C–40.0 °C ambient temperature. In addition, an improved standard deviation of 0.18 °C and a low 0.020 °C/m for the measured temperature are obtained under the variation in measuring the distance from 0.50 to 2.00 m.