Directional people counting arrangement

Abstract

An arrangement for detecting the passage of living beings through a surveillance region into and out of a controlled-access space includes at least one pyroelectric detector device that includes two detector elements which have active areas that are directly exposed to thermal radiation from the surveillance region and convert the thermal radiation energy received thereby into electrical signals with opposite polaritites. The detector elements are situated in succession in the direction of passage into the controlled-access space. The surveillance region is optically subdivided into two surveillance zones arranged in succession as considered in the passage direction, for instance by a mask that masks an intervening zone situated between the surveillance zones to prevent thermal radiation from the intervening zone from reaching either one of the detector elements. Thus, the thermal radiation energy from a living being passing through the surveillance region reaches initially only one and subsequently only the other of the detector elements when such living being is entering, and initially only the other and subsequently only the one detector element when such living being is leaving, the controlled-access space. The opposite polarity electrical signals are then evaluated on the basis of their then existing lead/lag relationship.