Detection of Human Position and Motion by Thermopile Infrared Sensor

Devices such as pyroelectric infrared sensors, ultrasonic sensors, cameras can be used to detect the presence of human-beings, but their systems have some problems related to low detection ability, low resolution, privacy, and high cost. We propose the use of thermopile infrared sensors without focus lenses and with high-gain amplifiers to detect the position and movement of human subjects. The system can detect even people that are not moving. This paper presents an approach that uses two thermopile sensors mounted on the ceiling to detect in 2D the position and orientation of human bodies. After each sensor takes measurements, we can build an approximate equation set that takes into account the output voltage, distance, and orientation of the human presence. The equation set can be solved, using the steepest descent method for the outputs of the two sensors, to obtain in real-time the position of a human-being in 2D. Body orientation can also be basically obtained by detecting slight changes in some positions while the human subject is moving. Tests are carried out to confirm that the proposed system works.