| 摘要 |
<p>A light-receiving signal from a photo diode is inputted to a control unit for generating rain drop information through a current high pass filter circuit (20, 20A), a current to voltage conversion circuit, a voltage high pass filter circuit (40, 40A), a peak hold circuit (50), and a non-reverse amplifying circuit (60). An offset unit in the voltage high pass filter circuit offsets the light-receiving signal such that the undershoot generated by filtering is equal to or more than the minimum input voltage which can be inputted to the peak hold circuit. Therefore an expensive analogue switch is not necessary for blocking input of the undershoot. Since the non-reverse amplifying circuit (60) serves also as an output buffer function, the output buffer becomes also unnecessary. A conversion rate of the current to voltage conversion circuit (30) is high by the current high pass filter circuit (20, 20A), and the detection can be made with high accuracy.</p> |
