Windshield moisture sensing control circuit

  • US 4,859,867 A
  • Filed: 04/19/1988
  • Issued: 08/22/1989
  • Est. Priority Date: 04/19/1988
  • Status: Expired due to Term
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First Claim
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1. A vehicle windshield rain sensor comprising:

  • emitter means for periodically emitting light radiation;

    first sensor means for detecting a portion of the radiation refracted and reflected by a windshield and producing a first signal indicative thereof;

    second detector means for detecting a portion of the radiation from said emitter means and producing a second signal indicative thereof;

    signal-processing means for processing the first signal, said signal-processing means including first amplifier means for amplifying the first signal, filter means for removing the noncyclical component from the amplified signal, and second amplifier means for amplifying the filtered signal, whereby the noncyclical portion of said signal due to ambient light impinging on said first sensor means is removed from the first signal and the cyclical portion is amplified; and

    control means for processing the first amplified signal from said signal-processing means and the second signal to provide a decision signal indicative of the amount of moisture on the windshield.

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