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Coordinate reading apparatus

  • US 5,025,410 A
  • Filed: 08/11/1988
  • Issued: 06/18/1991
  • Est. Priority Date: 08/12/1987
  • Status: Expired due to Term
First Claim
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1. A coordinate reading apparatus for inputting coordinate data to a computer and operable in a selected one of a relative coordinate mode and a second mode, said apparatus comprising:

  • a first member constituting a tablet defining a coordinate surface;

    a second member in the form of a coordinate designator movable across said surface so that a distance exists between said designator and said surface;

    position signal producing means associated with said members for producing a plurality of induced signals each inversely proportional to the distance between said designator and said surface so that one of the induced signals will have a value greater than the value of each other induced signal so that the value of the one of the induced signals will be a maximum induced signal value relative to the values of all of the induced signals; and

    coordinate value outputting means connected to said position signal producing means for producing coordinate value output signals representative of the coordinate value of the point designated by said designator, wherein said outputting means comprise;

    mode setting means responsive to a setting operation for generating a control signal indicative of the relative coordinate mode;

    selecting means for producing a first signal representing a predetermined value in the absence of the control signal, and responsive to the control signal for selectively producing, in place of the first signal, a second signal representing a value greater than the predetermined value;

    comparator means connected to said position signal producing means and to said selecting means for comparing the maximum induced signal value produced by said position signal producing means with the signal being produced by said selecting means and producing a comparison signal when the maximum induced signal value exceeds the value represented by the signal being produced by said selecting means; and

    coordinate value calculating means connected to said position signal producing means and to said comparator means for producing a coordinate value output signal from the induced signal value occurring in the time coincidence with the comparison signal.

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