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Object position detector

  • US 5,861,583 A
  • Filed: 07/15/1996
  • Issued: 01/19/1999
  • Est. Priority Date: 06/08/1992
  • Status: Expired due to Term
First Claim
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1. An object proximity sensor, including:

  • a capacitive touch-sensitive transducer including row conductive lines disposed in a first direction insulated from column conductive lines disposed in a second direction generally perpendicular to the first direction to form a matrix, and an insulating layer disposed over the matrix and having a thickness selected to achieve significant capacitive coupling between an object placed on its surface and the matrix;

    means for first driving each of said row conductive lines to a fixed voltage and then for simultaneously injecting a known amount of charge onto each of said row conductive lines, and then sensing for each row conductive line a row-sense voltage created by said known amount of charge injected onto each of said row conductive lines, and, simultaneous with injecting said known amount of charge, changing the voltage on all of said column conductive lines in the same direction as said row-sense voltage of said each row conductive line by an amount no greater than about twice the difference between said fixed voltage and an average of all row-sense voltages in said transducer;

    means for first driving each of said column conductive lines to a fixed voltage and then for simultaneously injecting a known amount of charge onto each of said column conductive lines, and then sensing for each column conductive line a column-sense voltage created by said known amount of charge injected onto each of said column conductive lines, and, simultaneous with injecting said known amount of charge, changing the voltage on all of said row conductive lines in the same direction as said column-sense voltage of said each column conductive line by an amount no greater than about twice the difference between said fixed voltage and an average of all column-sense voltages in said transducer; and

    means for producing a set of object-sensed electrical signals related to all of said row-sense voltages and said all of said column-sense voltages.

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