| 摘要 |
<p>PURPOSE:To perform stable, high-accuracy detection by providing a comparing means which decides whether or not there is a heat body in a prescribed area and a means which gives hysteresis to a threshold level. CONSTITUTION:Background temperature varies corresponding to ambient temperature and when the ambient temperature approximates the temperature of the surface (cloth surface) of a human body, the S/N of the background and human body decreases and it becomes difficult to detect the stationary human body. Specially, when threshold level width VTH is fixed and large although the difference between, for example, background temperature and human body surface temperature is small, there is the possibility of misdetection. For the purpose, a circuit shown in a figure is used instead of a hysteresis circuit 14 provided to a comparing circuit 13 and the threshold level width VTH is decreased automatically when the difference between the background temperature and human body surface temperature is small and decreased when the difference is large. Consequently, even if a detection signal level varies, its influence is eliminated.</p> |
