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Control system for a phacoemulsification handpiece

  • US 5,938,677 A
  • Filed: 10/15/1997
  • Issued: 08/17/1999
  • Est. Priority Date: 10/15/1997
  • Status: Expired due to Term
First Claim
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1. A method of controlling an ultrasonic handpiece having a variable series resonance frequency, comprising the steps of:

  • a) generating a drive signal having,i. a first signal at a first frequency substantially equal to a known current value of a series resonance frequency,ii. a second signal at a second frequency greater than the first frequency andiii. a third signal at a third frequency less than the first frequency;

    b) exciting the handpiece with the drive signal;

    c) measuring a first admittance at the first frequency, a second admittance at the second frequency, and a third admittance at the third frequency;

    d) predicting a future series resonance frequency based on the relative values of the first admittance, the second admittance, and the third admittance; and

    e) changing the first frequency by a dithering increment equal to the absolute value of the difference between the second frequency and the first frequency.

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