×

Method and apparatus for calibration of a charge ratio digitizer

  • US 4,831,566 A
  • Filed: 03/20/1987
  • Issued: 05/16/1989
  • Est. Priority Date: 03/20/1987
  • Status: Expired due to Fees
First Claim
Patent Images

1. In a digitizer comprising:

  • a digitizer tablet having a generally planar top surface and first and second electrodes lying in a plane parallel to said top surface, said first electrode having a first geometric pattern, said first pattern varying with a first coordinate in a two-coordinate system, and said second electrode having a second geometric pattern, said second pattern varying with the second coordinate in said two-coordinate system, said first and second electrodes being made of electrically conductive material; and

    a coupling means movable on said digitizer tablet top surface, said coupling means including a coupling electrode for electrostatic coupling with said first and second electrodes;

    the improvement comprisinga phantom cursor electrode fixedly arranged in said digitizer tablet and electrostatically coupled to said first and second electrodes, said phantom cursor electrode being arranged on the side of said plane opposite from said digitizer tablet top surface and having a point with predefined first and second coordinates;

    signal generating means for outputting a driving electrical signal to one of said coupling electrode and said phantom cursor electrode, application of said driving signal causing electrostatic coupling of the driven electrode with said first and second electrodes;

    electronic means for receiving and processing signals generated in said first and second electrodes in response to said driving signal to determine the first and second coordinates of a point on said coupling means when said coupling means is in proximity to said tablet; and

    switching means for sequentially connecting said phantom cursor electrode and said coupling electrode to said signal generating means for causing electrostatic coupling of first said phantom cursor electrode and then said coupling electrode with said first and second electrodes.

View all claims
  • 6 Assignments
Timeline View
Assignment View
    ×
    ×