| 摘要 |
<p>To a desired target light-receiving level in a state where a windshield is clean, a lower normal level possibly causing a driver to have a feeling of strangeness in an operation of a wiper 21 and recognize aging degradation when a light-receiving signal is equal to or less than the lower normal level, and a calibration lower limit level which is lower than the lower normal level and has no possibility of being generated in the aging degradation, are set to define a range between the lower normal level and the calibration lower limit level as a degradation determination zone Z. When the light-receiving signal continues to be within the degradation determination zone Z for a predetermined time T0 from a point of ignition-ON when the vehicle starts in a state where the wiper is not driven, or from a point of a drive termination of the wiper when the wiper is driven, it is determined that the aging degradation occurs. Therefore the calibration is executed by increasing a drive current value of a light-emitting element 11 so that the light-receiving signal becomes equal to the target light-receiving level.</p> |
