SENSING CIRCUIT AND INFRARED DETECTION DEVICE WITH THE SAME

PROBLEM TO BE SOLVED: To provide a sensing circuit whose reduction in sensitivity of a low frequency component can be suppressed, and an infrared detection device with the same.SOLUTION: A sensing circuit 1 comprises: an input terminal 11; a filter circuit 3; and a control unit 8. A detection signal is input to the input terminal 11 from a pyroelectric element 2. The filter circuit 3 forms between the input terminal 11 and an output terminal 12, one route 30 through which the detection signal is caused to pass, and attenuates or amplifies a specific frequency component of the detection signal passing through the route 30. The control unit 8 changes a frequency characteristic of a gain in the filter circuit 3. An operation mode of the control unit 8 includes an intrusion detection mode in which the presence or absence of intrusion of a person into a detection zone is detected by a determination unit 71 based on the detection signal, and a stay detection mode in which the presence or absence of existence of the person in the detection zone is detected by the determination unit 71 based on the detection signal. The control unit 8 changes the frequency characteristic in accordance with the operation mode.SELECTED DRAWING: Figure 1 【課題】低周波成分の感度の低下を抑えることができる検知回路、及びそれを備えた赤外線検出装置を提供する。【解決手段】検知回路１は、入力端子１１と、フィルタ回路３と、制御部８とを備えている。入力端子１１は、焦電素子２から検知信号が入力される。フィルタ回路３は、入力端子１１と出力端子１２との間に検知信号を通過させる一の経路３０を形成し、経路３０を通過する検知信号の特定の周波数成分を減衰又は増幅する。制御部８は、フィルタ回路３における利得の周波数特性を変化させる。制御部８の動作モードは、検知信号に基づいて検知領域への人の侵入の有無が判定部７１にて検知される侵入検知モードと、検知信号に基づいて検知領域内の人の存在の有無が判定部７１にて検知される滞在検知モードとを含んでいる。制御部８は、動作モードに応じて周波数特性を変化させる。【選択図】図１