Importance

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Abstract

In order to detect the movement of a heat source over a widened range by using a reduced number of pyroelectric type infrared sensors, a sensor section includes two infrared detecting means X and Y. The area to be observed by the infrared detecting means X is divided into two zones A and B while the area to be observed by the infrared detecting means Y is divided into two single zones a and b. The single zones A and a are overlapped on each other to form an overlap zone (A, a). The movement of the heat source between the single zone B and the single zone b, between the overlap zone (A, a) and the single zone B and between the overlap zone (A, a) and the single zone b is judged to detect the movement of the heat source over the entire area to be observed by the sensor section. In such a manner, two infrared detecting means can cover three zones to be observed.

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First Claim