Reliable people counter based on object characterization using an infrared light array

The concept and realisation of a simple infrared sensor array based on intensity evaluation of the reflected light to determine properties of moving objects like direction(trajectory), size, velocity is described. In particular, the problem of reliably counting persons entering or leaving a room has been examined. Contrary to common impression, this is not at all a simple task: Incidental counting errors e.g. of commonly used double-beam light barriers are cumulated over time, making such devices almost useless for certain applications like occupancy-dependent air-conditioning, lighting or heating of rooms. With the proposed modeling and array processing, the persons are reliably detected and well separable from other echoes (motion of hands etc.).