Passive infrared detector

摘要

A passive infrared detector that enables the extent of the field to be 360 degrees in circumference with a simple arrangement and allows the field range in the vertical direction to be adjusted wholly or partially. A plurality of sensor units are circumferentially arranged on a sensor mounting plate. Each sensor unit has a reflecting mirror and a sensing element placed at the focus position of the mirror. Each sensor unit is rotatable in the vertical direction. A slot is formed radially in the sensor mounting plate opposite to each sensor unit. A rotating plate is rotatably mounted on the sensor mounting plate. A circumferential slit is formed circumferentially in the rotating plate such that the distance from the center of the rotating plate to the circumferential slit gradually decreases. An adjusting rod is connected at one end thereof to each sensor unit. The other end of the adjusting rod extends through the slot and the circumferential slit.