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Proximity sensor

  • US 6,445,294 B1
  • Filed: 07/14/2000
  • Issued: 09/03/2002
  • Est. Priority Date: 07/15/1999
  • Status: Expired due to Term
First Claim
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1. A proximity sensor for sensing an electric-field-influencing media within a region of space, comprising:

  • a. a first electrode, wherein said first electrode is conductive;

    b. a first oscillatory signal operatively coupled to said first electrode;

    c. at least one second electrode, wherein said at least one second electrode is conductive and said at least one second electrode is separated from said first electrode;

    d. a second oscillatory signal operatively coupled to said at least one second electrode, wherein said second oscillatory signal comprises a state, said state is selected from a first state and a second state, when in a first state said second oscillatory signal has a first phase relative to said first oscillatory signal, when in a second state said second oscillatory signal has a second phase relative to said first oscillatory signal;

    e. a means for controlling said state of said second oscillatory signal;

    f. a means for measuring a third signal from said first electrode when said second oscillatory signal is in said first state;

    g. a means for measuring a fourth signal from said first electrode when said second oscillatory signal is in said second state;

    h. a means for forming a difference of said third and fourth signals; and

    i. a means for generating a measure of proximity of an object to said proximity sensor responsive to said difference.

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