Circular electrographic touch sensor with orthogonal fields and linear response
First Claim
1. A circular position sensitive sensor having resistive electrodes which provides a linear response over substantially the entire sensor by achieving straight orthogonal equipotential lines in an X-Y coordinate system throughout said circular sensor, which comprises:
- a resistive surface of uniform electrical sheet resistivity, said surface defining a circular perimeter;
conductive tie points positioned proximate said perimeter and located at polar and equatorial points of said sensor, said tie points defining divisions between symmetrical quadrants of said sensor;
a resistance element positioned in each of said quadrants proximate said perimeter, said resistance element of each quadrant defining opposite end portions, said opposite end portions connected to adjacent of said tie points; and
a plurality of electrodes positioned on said resistive surface along an arcuate path in each of said quadrants proximate said resistance element, said electrodes being electrically attached to said surface and to said resistance element, said electrodes having a selected center-to-center spacing and effective length along said path;
wherein said selected spacing and length produce voltage gradients at each of said electrodes to compensate for non-linear potentials along said resistance element produced by an arcuate geometry of said resistance element and by any cumulative voltage drop along said resistance element due to current flow from said electrodes into said resistive surface to thereby achieve said straight X- and Y-coordinate equipotential lines within said sensor.
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Accused Products
Abstract
A circular touch sensor having very linear response in a two coordinate system. This circular sensor has four substantially identical and symmetrical quadrants, with points for the introduction of potentials being located at polar and equatorial points on the sensor. The sensor has a uniform electrical sheet resistivity, and each quadrant has a resistance element to distribute the potentials to electrodes connected thereto which are positioned along the perimeter of the circular resistive surface. Individual ends of the resistance element in each quadrant are connected to their respective "tie points" through a resistor of a size to adjust for a proper resistance value between the quadrants at these points. The size (effective length along the position path) of the electrodes in each quadrant generally increases, and the spacing between electrodes generally decreases, symmetrically from the edges of each quadrant toward the center of that quadrant. In this manner, voltage gradients are produced at each of the electrodes to compensate for any cumulative voltage drop along the resistance element due to current flow into the resistive surface and due to the circular geometric configuration. In the preferred embodiment, a "floating" conductive element is placed on the path of the electrodes proximate the tie points to further enhance linearity of the sensor near these points. A typical sensor of this type is described in detail.
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Citations
20 Claims
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1. A circular position sensitive sensor having resistive electrodes which provides a linear response over substantially the entire sensor by achieving straight orthogonal equipotential lines in an X-Y coordinate system throughout said circular sensor, which comprises:
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a resistive surface of uniform electrical sheet resistivity, said surface defining a circular perimeter; conductive tie points positioned proximate said perimeter and located at polar and equatorial points of said sensor, said tie points defining divisions between symmetrical quadrants of said sensor; a resistance element positioned in each of said quadrants proximate said perimeter, said resistance element of each quadrant defining opposite end portions, said opposite end portions connected to adjacent of said tie points; and a plurality of electrodes positioned on said resistive surface along an arcuate path in each of said quadrants proximate said resistance element, said electrodes being electrically attached to said surface and to said resistance element, said electrodes having a selected center-to-center spacing and effective length along said path; wherein said selected spacing and length produce voltage gradients at each of said electrodes to compensate for non-linear potentials along said resistance element produced by an arcuate geometry of said resistance element and by any cumulative voltage drop along said resistance element due to current flow from said electrodes into said resistive surface to thereby achieve said straight X- and Y-coordinate equipotential lines within said sensor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A circular position sensitive sensor having resistive electrodes which provides a linear response over substantially the entire sensor by achieving straight orthogonal equipotential lines in an X-Y coordinate system throughout said circular sensor, which comprises:
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a resistive surface having a uniform electrical sheet resistivity of between about 10 and about 10,000 ohms per square, said surface defining a circular perimeter; conductive tie points positioned on said sensor proximate said perimeter located at polar and equatorial points of said sensor, said tie points defining divisions between symmetrical quadrants of said sensor; a resistance element positioned in each of said quadrants proximate said perimeter, said resistance element having a uniform resistance value between about 6 and about 6,000 ohms per foot, said resistance element of each quadrant defining opposite end portions; a resistor having a resistance value of between about 10 and about 55 ohms joining each of said opposite ends of said resistance element of each quadrant to adjacent of said tie points; a plurality of electrodes positioned on said resistive surface along an arcuate path in each of said quadrants proximate said resistance element, said electrodes being electrically attached to said surface and to said resistance element, said electrodes having a selected center-to-center spacing along said path which symmetrically decreases from each edge of said quadrant toward a centerline of said path and a selected length along said path which symmetrically increases from each edge of said quadrant toward said centerline; and wherein said selected spacing and length produce voltage gradients at each of said electrodes to compensate for non-linear potentials along said resistance element produced by an arcuate geometry of said resistance element and by any cumulative voltage drop along said resistance element due to current flow from said electrodes into said resistive surface to thereby achieve said straight X- and Y-coordinate equipotential lines within said sensor. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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20. A circular position sensitive sensor having resistive electrodes which provides a linear response over substantially the entire sensor by achieving straight orthogonal equipotential lines in an X-Y coordinate system throughout said circular sensor, which comprises:
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a resistive surface having a uniform electrical sheet resistivity of between about 10 and about 10,000 ohms per square, said surface defining a circular perimeter; conductive tie points positioned on said sensor proximate said perimeter located at polar and equatorial points of said sensor, said tie points defining divisions between symmetrical quadrants of said sensor; a resistance element positioned in each of said quadrants proximate said perimeter, said resistance element having a uniform resistance value between about 6 and about 6,000 ohms per foot, said resistance element of each quadrant defining opposite end portions; a resistor having a resistance value of between about 10 and about 55 ohms joining each of said opposite ends of said resistance element of each quadrant to adjacent of said tie points; a plurality of electrodes positioned on said resistive surface along an arcuate path in each of said quadrants proximate said resistance element, said electrodes being electrically attached to said surface and to said resistance element, said electrodes having a selected center-to-center spacing along said path which symmetrically decreases from each edge of said quadrant toward a centerline of said path and a selected length along said path which symmetrically increases from each edge of said quadrant toward said centerline, said selected spacing and length produce voltage gradients at each of said electrodes to compensate for any non-linearities in potentials produced by arcuate geometry of said resistance element and by cumulative voltage drop along said resistance element due to current flow from said electrodes into said resistive surface to thereby achieve said straight X- and Y-coordinate equipotential lines throughout said circular sensor; a voltage source; switching means connected between said voltage source and said tie points at said equatorial and polar points to alternately produce said equipotential lines in said resistive surface; and means for positioning proximate said resistive surface at a selected location to obtain signals corresponding to X- and Y-coordinates of said selected location.
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Specification