Cheap thermal sensor operates at high temperatures

Thermal-imaging sensors have been in demand since the beginning of the Covid-19 pandemic to examine the thermal profile of human bodies and detect people who may have elevated temperatures: a symptom of the disease.

The smartphone industry is considering incorporating such sensors as portable features to in order to allow them to measure temperature in real time. Additionally, the application of such technology to autonomous vehicles could facilitate safer autonomous driving.

Researchers at the Korea Institute of Science and Technology have developed a new sensor that can operate at temperatures up to 100°C without a cooling device and is expected to be more affordable than standard sensors on the market.

Many of the thermal imaging sensors currently available cannot operate above 35°C. But to be integrated with the hardware of smartphones and autonomous vehicles, sensors must operate stably without any difficulties at high temperatures of 85°C and 125°C, respectively. For conventional thermal-imaging sensors to meet this criterion, an independent cooling device would be required. High-end cooling devices can be very expensive and still do not make the sensor suitable for operations at temperatures as high as 85°C.

The new device uses a vanadium dioxide-B film that is stable at 100°C. This device detects and converts the infrared light generated by heat into electrical signals and eliminates the need for cooling devices, which account for over 10 per cent of the cost of thermal-imaging sensors and consume large amounts of electricity. The device was able to obtain the same level of infrared signals at 100°C as it was at room temperature.

Due to fabricating and using an infrared absorber that can absorb as much infrared light as possible, it could also detect heat signatures with three times greater sensitivity.

The device has a response time of around 3ms even at 100 °C, which is about three to four times times faster than conventional ones. These speeds allow the device to capture thermal images at 100 frames per second, exceeding the conventional level of 30-40 frames per second (a particularly useful feature for use in autonomous vehicles).

Dr Won Jun Choi said: “By means of our work with convergence research in this study, we have developed a technology that could dramatically reduce the production cost of thermal-imaging sensors. Our device, when compared to more conventional ones, has superior responsivity and operating speed. We expect this to accelerate the use of thermal-imaging sensors in the military supply, smartphone, and autonomous vehicle industries.”