| 摘要 |
An improved infrared intrusion detector (S0) is provided which conveniently and expeditiously monitors two fields (F1, F2) of view by use of a single sensor (52). In a preferred embodiment, the improved intrusion detector (S0) monitors fields of views (F1, F2) which are substantially orthogonal in a nonobvious manner. It is nonobvious in that an aperture (62) is provided in a housing (60) which permits radiation from a second field of view (F2) to enter the housing (60). Internal optical elements (64) are provided to direct this incident radiation from the second field of view (F2) onto a sensor (52) used for the first field of view (F1). The internal optical elements (64) are protected from the environment and do not give advance warning that a second field of view (F2) is monitored. Generally, the second field of view (F2) is below the intrusion detector (50) to detect unauthorized activity in a dead zone below the detector (50).
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