Development of people-counting system with human-information sensor using multi-element pyroelectric infrared array detector

A people-counting system with a human-information sensor which can be used for detecting the number of people passing a door and their directions of movement has been developed. The sensor head module of this sensing system consists of a one-dimensional eight-element array detector made from pyroelectric PbTiO3 ceramics, an IR-transparent spherical lens and a cylindrical mechanical chopping part. This compact sensor is set at the top of the door with the element array parallel to the movement direction of the passersby. The electrode size of the detector and the lens characteristics have been determined to optimize the sensing area. The movement directions and the number of continuously passing people can be obtained promptly based on digital output from the signal-processing circuits. The data are processed in real time by a new algorithm: (1) background sequential mean method; (2) ternarizing method with two threshold values above and below the mean value; (3) differential detecting method; (4) compensation method. By using this people-counting system, the number of passersby at a door can be detected with more than 98% accuracy. In the case of a 2 m wide door, the multisensor system using human-information sensors can be adopted.