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High resolution system for sensing spatial coordinates

  • US 6,175,773 B1
  • Filed: 11/23/1998
  • Issued: 01/16/2001
  • Est. Priority Date: 10/19/1987
  • Status: Expired due to Fees
First Claim
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1. An apparatus for determining the spatial position of an object with respect to a surface, comprising:

  • drive circuitry connected to the surface providing alternating electrical current in the surface in predetermined directions and at predetermined intervals of time;

    a detector/amplifier detecting and amplifying alternating electrical signals produced in the surface, the detected and amplified signals varying depending upon the position of the object with respect to the surface;

    a rectifier connected to the detector/amplifier controllably rectifying the detected and amplified alternating electrical signals during periodic intervals and for providing rectified electrical output signals;

    an integrator periodically integrating the rectified electrical output signals output from the rectifier and producing output signals in response to the rectified electrical output signals;

    an analog-to-digital converter producing digital signals in response to the output signals of the integrator, a processor connected to the analog-to-digital converter, wherein the processor calculates the spatial position of the object with respect to the surface based on the digital signals produced by the analog-to-digital converter; and

    control circuitry generating control signals for controlling the drive circuitry, rectifier, integrator and processor, wherein the control circuitry comprises circuitry establishing a substantially fixed phase relationship between the control signals and the alternating electrical current, wherein the integrator operates synchronously with respect to the control signals.

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