| CPC G01J 5/0846 (2013.01) | 11 Claims |

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1. An apparatus configured to count objects, comprising:
a power source;
a radio transceiver;
two or more passive infrared sensors, comprising a first passive infrared sensor and a second passive infrared sensor, each passive infrared sensor comprising at least two infrared-sensitive elements;
a mechanical field of view limiting structure configured to limit the field of view of each infrared-sensitive element, wherein the field of views of each infrared-sensitive element within each passive infrared sensor are adjacent to each other, and the field of views between each passive infrared sensor are side by side;
one or more memories including computer program code; and
a processor configured to execute the computer program code to cause the apparatus to perform at least the following:
detecting, by the first passive infrared sensor, a first motion of an object based on signal differential changes between its two infrared-sensitive elements;
detecting, by the second passive infrared sensor, a second motion of the object based on signal differential changes between its two-infrared-sensitive elements;
if the second motion is detected within a predetermined time period after the first motion, increasing an inward count of objects moving to a direction from the first passive infrared sensor to the second passive infrared sensor, or if the first motion is detected within a predetermined time period after the second motion, increasing an outward count of objects moving to a direction from the second passive infrared sensor to the first passive infrared sensor; and
transmitting, using the radio transceiver, the inward count of objects and/or the outward count of objects,
wherein the mechanical field of view limiting structure is a solid block with a separate cut-out for each infrared-sensitive element configured as a chamber configured to limit the field of view of each infrared-sensitive element so that sides of the cut-out surround the infrared-sensitive element, and sides of the cut-out towards the objects are wider apart than sides of the cut-out towards the infrared-sensitive element so that slanted walls between the cut-out surrounding the infrared-sensitive element and the cut-out towards the objects are configured to funnel infrared radiation emitting from the objects to each infrared-sensitive element from different locations, each chamber acting as a directing waveguide.
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