| 摘要 |
PROBLEM TO BE SOLVED: To accurately detect raindrops by effectively reducing an external light component and the other noise component, in a raindrop detecting device using a light emitting element and a light receiving element. SOLUTION: This raindrop detecting device comprises two sets of light emitting elements 11a and 11b and light receiving elements 12a and 12b for radiating pulse light towards a windshield and receiving the reflected light. The optical axes of both light receiving elements are arranged in parallel. The output of each light receiving element is converted by current-voltage converting circuits 13a and 13b, the external light components included in both outputs of the current-voltage converting circuits are canceled and removed by a differential amplifier 16, then the peak value of a pulse light component is held by a signal processing circuit 18. A raindrop information creating section 32 of a control section 30 detects raindrops based on the peak value. Low-pass filters 14a and 14b are attached to respective current-voltage converting circuits, and reduce the external light components having come into respective light receiving elements. Thus, the raindrops can be detected without being affected by the external light without saturating the outputs of the current-voltage converting circuits. COPYRIGHT: (C)2009,JPO&INPIT
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