| 摘要 |
<p>PURPOSE:To reduce an erroneous operation due to a change in a disturbance light or a back ground temperature by a construction wherein a human body is judged to be present only when outputs of positive and negative polarities of an infrared ray detecting element exceed prescribed threshold values within a prescribed time. CONSTITUTION:A processing decision unit 4 sets prescribed threshold values V1 and V2 above and below an output bias value VB of an amplifier unit 3 so that V1 < VB < V2, and makes an output onto the positive polarity side only for a prescribed time T0 when VS < V2 in regard to a signal output VS of the amplifier unit 3, while making the output onto the negative polarity side when VS < V1, and the composite output of them is taken as an output of detection of a human body. Outputs of an infrared ray detecting element 2 and the amplifier unit 3 are delivered to be above and below the bias value VB, corresponding to an incident power. While the output is made onto the positive polarity side when the human body enters a detection area and onto the negative polarity side when it gets out of it, in other words, the output occurs on the positive polarity side in the case of a disturbance light only when the light enters the detection area. Next, the decision unit 4 detects the human body only when the output of the amplifier unit 3 occurs on the positive and negative polarity sides within the prescribed time. Accordingly, an erroneous operation can be prevented with regard to the disturbance light or a change in a background temperature.</p> |
