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Thermopile Arrays for IR Imaging and body temperature screening applications
Schieferdecker, J.; Schnorr, M., Forg, B.; Herrmann, F., Schmidt, C.; Leneke, W.; Simon, M.:
Heimann Sensor GmbH, Maria-Reiche-Str. 1, 01109 Dresden, Tel. +49-351-888885-0; info@heimannsensor.com;
In first part of this paper we describe, how fast the lower resolution thermopile arrays could be integrated into body temperature screeners to fight against COVID-19 pandemic spread. Second part will introduce first thermopile arrays with 60 µm pixel size, which allow to extend the application range into thermal Imaging and surveillance. All necessary signal conditioning and readout electronics including SPI interface are monolithically integrated on the sensor chip and allow thermopile arrays up to 120x84 pixels to fit in a standard TO-8 housing.
Most thermopile arrays going into the body temperature screeners using simple 32x32 arrays with a single Ge lens using special coating for the 8-14 µm range. Due to small chip, simple fix focus optics and no need for vacuum packaging, they could be produced in very high volumes. Due to low pixel count, the screening was only for one person in narrow range up to about 1 m or so – sufficient for building entrance control. 80x64 arrays were bigger and more costly, but could be used to measure temperatures at up to 3 or 4 persons simultaneously.
The digital output via SPI interface reduces the number of necessary connections of both 80x64 and the new 120x84 arrays to 6-pin only. Thanks to integrated 16 Bit AD converters on-chip the sensor arrays can be operated with Frame Rates up to 12 Hz (full resolution) and allow a very wide dynamic range with object temperatures up to 1000 °C. Higher frame rates are possible with setting the ADC resolution to 15 or 14 Bit.
Since the new 120x84 array chip has 60 µm pixels vs the 90 µm pixels of the 80x64, both chips come with similar focal plane and chip sizes. Due to their identical SPI interface both chips can be mounted in same housing with same optics, giving rise to a “drop in” solution.
Thermopile arrays are low cost but quite efficient sensors in 2020 fighting the COVID-19.
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