Edge linearization device for a contact input system

• US 5,041,701 A
• Filed: 03/15/1988
• Issued: 08/20/1991
• Est. Priority Date: 03/15/1988
• Status: Expired due to Fees

• Current Assignee: MicroTouch Systems, Inc. (3M Company), Anton Ness, Gunze Electronics USA Corporation (Gunze Limited)
• Original Assignee: Carroll Touch Incorporated
• Inventors: Wolfe, Andrew L., Barrett, Gary L.
• Primary Examiner(s): Schreyer, Stafford D.
• Application Number:
  US07/168,292
• Time in Patent Office: 1,253 Days
• Field of Search: 178/18, 178/19, 178/20
• US Class Current: 178/18.05
• CPC Class Codes: G06F 2203/04113 Peripheral electrode pattern in resistive digitisers, i.e. electrodes at the periphery of the resistive sheet are shaped in patterns enhancing linearity of induced field
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

An edge linearization device for linearizing the electric fields in a resistive surface is described. A plurality of electrodes are disposed on the perimeter of an area on a surface having a substantially uniform resistivity. The device utilizes the geometry of the spaces between adjacent conductive elements to provide resistive elements. At least one of the electrodes has an extension. The extension or extensions of the electrodes are progressively inwardly displaced into the area from the perimeter so that there is at least one center-most extension on a first portion of said perimeter and also on a second, opposing portion of said perimeter. In a preferred embodiment, the invention utilizes a surface with a substantially rectangular area having four sides and four corners. Disposed along the sides are a plurality of electrodes and corner electrodes and disposed in the corners of the surface are corner connectors. The use of T-shaped extensions of the electrodes on such a surface is also disclosed. When an electric potential is selectively applied across the surface, a unique electric potential exists which corresponds to the location of a movable object on the surface. A contact input system utilizing such an edge linearization device is disclosed. The contact input system utilizes the surface with the electrodes, corner electrodes, and corner connectors disposed thereon with a movable object for selectively contacting the surface, means responsive to the object for determining the object'"'"'s location on the surface, and means for selectively applying an electric potential across the surface.

Claims

1. An edge linearization device, which comprises:

a surface having a substantially uniform resistivity and defining a substantially rectangular area with four sides and four corners;

a plurality of electrodes disposed on said surface on each side of said area and electrically connected to said surface, with at least one of said electrodes having an extension wherein said extension of at least one of said electrodes on each side of said area is inwardly disposed into said area so that at least one extension is more inwardly disposed into said area than said electrodes and said electrodes have a greater conductivity than said surface so that, when an electric potential is selectively applied between said electrodes on a side and said electrodes on an opposing side, a unique electric potential exists corresponding to an object'"'"'s location on said surface;

at least one corner electrode disposed on said surface and located on each side of said surface and electrically connected thereto, wherein said corner electrode has a greater conductivity than said surface;

a plurality of corner connectors disposed on said surface and electrically connected thereto and positioned adjacent said corners of said area;

said electrodes, said corner electrodes, and said corner connectors are selectively disposed on said surface and include edges laterally therealong defining gaps therebetween and further include projections extending laterally therefrom and corresponding projection-receiving recesses extending thereinto with said edges thereof maintaining a constant selected distance from each other, said gaps thereby having a width equal to said constant distance and a length greater than the length of said electrodes, said corner electrodes and said corner connectors, to create gaps selectively shaped and dimensioned to define preselected resistivities between said electrodes, said corner electrodes, and said corner connectors,

whereby the lengths of said electrodes protrude only minimally into the surface from sides thereof while defining separate resistors of greater length, thereby optimizing the active area of said surface, and no resistive elements are otherwise connected between said electrodes, said corner electrodes, and said corner connectors.

2. The edge linearization device according to claim 1 wherein said extension is T-shaped.

15. The edge linearization device according to any one of claims 2-4, wherein said surface comprises a glass substrate with a thin film coating and said electrodes comprise a metal ink with a resistivity of less than about 1 ohm per square.

3. An edge linearization device, which comprises:

a surface having a substantially uniform resistivity and defining a substantially rectangular area with four sides and four corners;

a plurality of electrodes having extensions disposed on said surface on each side of said area and electrically connected to said surface, wherein said extensions of said electrodes on each side of said area are progressively inwardly disposed into said area from said corners so that at least one center-most extension is most inwardly disposed of said extensions of said electrodes on each side of said area, said progressively inwardly disposed extensions of said electrodes being disposed in the approximate shape of a parabola having a vertex which is near the location of said center-most extension, and said electrodes have a greater conductivity than said surface so that, when an electric potential is selectively applied between said electrodes on a side and said electrodes on an opposing side, a unique electric potential exists corresponding to an object'"'"'s location on said surface;

at least one corner electrode disposed on said surface and located on each side of said surface and electrically connected thereto, wherein said corner electrode has a greater conductivity than said surface; and

a plurality of corner connectors disposed on said surface and electrically connected thereto and positioned adjacent said corners of said area,

said electrodes, said corner electrodes, and said corner connectors are selectively disposed on said surface and include edges laterally therealong defining gaps therebetween and further include projections extending laterally therefrom and corresponding projection-receiving recesses extending thereinto with said edges thereof maintaining a constant selected distance from each other, said gaps thereby having a width equal to said constant distance and a length greater than the length of said electrodes, said corner electrodes and said corner connectors, to create gaps selectively shaped and dimensioned to define preselected resistivities between said electrodes, said corner electrodes, and said corner connectors,

whereby the lengths of said electrodes need protrude only minimally into the surface from sides thereof to define separate resistors of greater length, thereby optimizing the active area of said surface, and no resistive elements are otherwise connected between said electrodes, said corner electrodes, and said corner connectors.

4. The edge linearization device according to claim 3 wherein said extensions of said plurality of electrodes are T-shaped.

5. An apparatus for producing a potential field having a prescribed geometry comprising:

a surface having a substantially uniform sheet resistivity;

a plurality of discrete electrodes disposed in contact with the surface in at least one row along at least one side of the surface, each electrode having a greater conductivity than the surface;

said electrodes are selectively disposed on said surface and include edges laterally therealong defining gaps therebetween and further include projections extending laterally therefrom and corresponding projection-receiving recesses extending thereinto with said edges thereof maintaining a constant selected distance from each other, said gaps thereby having a width equal to said constant distance and a length greater than the length of said electrodes, said corner electrodes and said corner connectors, to create gaps selectively shaped and dimensioned to define separate resistors having preselected resistivities between said electrodes proportional to the sheet resistivity of the surface;

a plurality of the electrodes include an extension extending transversely to each row of electrodes, an integrated resistor being formed between each extension; and

a voltage supply connectable to a first electrode located at one end of the potential field to establish a potential difference between the first electrode and a second electrode located at an opposite end of the potential field, a plurality of intervening electrodes being positioned between the first and second electrodes,

whereby the geometry of the potential field is a function of the resistance of the separate resistors between adjacent electrodes, and whereby the lengths of said electrodes need protrude only minimally into the surface from sides thereof to define separate resistors of greater length, thereby optimizing the active area of said surface, and no resistive elements are otherwise connected between said electrodes.

6. The apparatus of claim 5 wherein each electrode is formed of a screen printable conductive ink.

7. The apparatus of claim 6 wherein the surface is formed of a sputtered indium tin oxide layer.

8. An edge linearization device, which comprises:

a surface having a substantially uniform resistivity and defining a substantially rectangular area with four sides and four corners;

a plurality of electrodes disposed on said surface on each side of said area and electrically connected to said surface, each electrode having a greater conductivity then the surface;

at least one corner electrode disposed on said surface on each side of said surface and electrically connected thereto, wherein said corner electrode has a greater conductivity than said surface;

a plurality of corner connectors disposed on said surface and electrically connected thereto and positioned adjacent said corners of said area;

said electrodes, said corner electrodes, and said corner connectors are selectively disposed on said surface and include edges laterally therealong defining gaps therebetween and further include projections extending laterally therefrom and corresponding projection-receiving recesses extending thereinto with said edges thereof maintaining a constant selected distance from each other, said gaps thereby having a width equal to said constant distance and a length greater than the length of said electrodes, said corner electrodes and said corner connectors, to create gaps selectively shaped and dimensioned to define preselected resistivities between said electrodes, said corner electrodes, and said corner connectors proportional to the sheet resistivity of the surface,

such that, when an electric potential is selectively applied between said electrodes and corner electrodes on a first side and a second side and between said electrodes and said corner electrodes on a third side and a fourth side, an electric potential field exists having a geometry which is a function of the resistance of said resistors between said electrodes, said corner electrodes, and said corner connectors, and whereby the lengths of said electrodes need protrude only minimally into the surface from sides thereof to define separate resistors of greater length, thereby optimizing the active area of said surface, and no resistive elements are otherwise needed to be connected between said electrodes, said corner electrodes, and said corner connectors.

9. An apparatus for producing a potential field having a prescribed geometry comprising:

a surface having a substantially uniform sheet resistivity;

a plurality of discrete electrodes disposed in contact with the surface, each electrode having a greater conductivity than the surface,

said electrodes are selectively disposed on said surface and include edges laterally therealong defining gaps therebetween and further include projections extending laterally therefrom and corresponding projection-receiving recesses extending thereinto with said edges thereof maintaining a constant selected distance from each other, said gaps thereby having a width equal to said constant distance and a length greater than the length of said electrodes, said corner electrodes and said corner connectors, to create gaps selectively shaped and dimensioned to define separate resistors having preselected resistivities between said electrodes proportional to the sheet resistivity of the surface;

a voltage supply connectable to a first electrode located at one end of the potential field to establish a potential difference between the first electrode and a second electrode located at an opposite end of the potential field, a plurality of intervening electrodes being positioned between the first and second electrodes, wherein electrodes are disposed about the perimeter of the surface and the voltage is alternately applied to electrodes in the corners of the surface,

whereby the geometry of the potential field is a function of the resistance of the separate resistors between adjacent electrodes, and whereby the lengths of said electrodes need protrude only minimally into the surface from sides thereof to define separate resistors of greater length, thereby optimizing the active area of said surface.

10. The apparatus of claim 9 wherein a plurality of electrodes between the electrodes in the corners of the surface include inwardly extending portions, the inwardly extending portions being parabolically disposed along each side.

11. An apparatus for producing a linearized potential field comprising:

a surface having a substantially uniform sheet resistivity;

a plurality of discrete electrodes disposed in contact with the surface in a row along at least one side of the surface, each electrode having a greater conductivity than the surface, a plurality of electrodes having a base and a projection extending transversely of the side along which the electrodes are disposed;

said electrodes are selectively disposed on said surface and said bases thereof include edges laterally therealong defining gaps therebetween and further include projections extending laterally therefrom and corresponding projectionreceiving recesses extending thereinto with said edges thereof maintaining a constant selected distance from each other, said gaps thereby having a width equal to said constant distance and a length greater than the length of said electrodes, said corner electrodes and said corner connectors, to create gaps selectively shaped and dimensioned to define separate resistors having preselected resistivities between said electrodes proportional to the sheet resistivity of the surface;

a voltage supply connectable to an electrode located at one end of the row of electrodes to establish a potential difference between opposite ends of each row of electrodes,

whereby the geometry of the potential field is a function of the resistance of the separate resistors between adjacent electrodes, and whereby the lengths of said bases of said electrodes need protrude only minimally into the surface from sides thereof to define separate resistors of greater length, thereby optimizing the active area of said surface.

12. A contact input system for determining the location of an object in selective contact with a surface having a substantially uniform resistivity and defining a substantially rectangular area with four sides and four corners, which comprises:

a plurality of electrodes having extensions disposed on said surface on each side of said area and electrically connected to said surface, wherein said extensions of said electrodes along each side of said area are progressively inwardly disposed into said area from said corners so that at least one center-most extension is most inwardly disposed of said extensions of said electrodes along each side of said area, said electrodes having a greater conductivity than said surface so that, when an electric potential is selectively applied between said electrodes on a side and said electrodes on an opposing side, a unique electric potential exists for a corresponding location of an object touching said surface;

a plurality of corner electrodes disposed on said surface and electrically connected thereto, wherein said corner electrodes are positioned near said corners of said area;

a plurality of corner connectors disposed on said surface and electrically connected thereto and positioned adjacent said corners of said area;

means connected to said corner connectors for selectively applying an electric potential thereto so that an electric potential exists between a first side of said area and a second opposing side of said area and for selectively applying an electric potential thereto so that an electric potential exists between a third side of said area and a fourth side opposing said third side, wherein said third side and said fourth side are substantially perpendicular to said first side and said second side;

a movable object for selectively contacting said surface; and

means responsive to said movable object for determining the location of said movable object on said surface corresponding to an electric potential between said movable object and said electrodes and said corner electrodes and providing an output thereof, wherein said electrodes, said corner electrodes, and said corner connectors are selectively disposed on said surface and include edges laterally therealong defining gaps therebetween and further include projections extending laterally therefrom and corresponding projection-receiving recesses extending thereinto with said edges thereof maintaining a constant selected distance from each other, said gaps thereby having a width equal to said constant distance and a length greater than the length of said electrodes, said corner electrodes and said corner connectors, to create gaps selectively shaped and dimensioned to define preselected resistivities between said electrodes, said corner electrodes, and said corner connectors,

whereby the lengths of said electrodes protrude only minimally into the surface from sides thereof while defining separate resistors of greater length, thereby optimizing the active area of said surface, and no resistive elements are otherwise connected between said electrodes, said corner electrodes, and said corner connectors.

13. The contact input system according to claim 12, wherein said progressively inwardly disposed extensions of said electrodes are disposed in the approximate shape of a parabola having a vertex which is near the location of said center-most extension.

14. The contact input system according to claim 12 wherein said extensions of said electrodes on each side of said area are T-shaped.

16. An apparatus for producing a potential field having a prescribed geometry comprising:

a surface having substantially uniform sheet resistivity;

a plurality of discrete electrodes disposed in contact with the surface, each electrode having a greater conductivity than the surface;

a plurality of separate resistors, wherein adjacent electrodes are spaced apart by a gap having prescribed dimensions such that the portion of the surface in the gap between adjacent electrodes defines a separate resistor between adjacent electrodes having a resistance proportional to the sheet resistivity of the surface, at least a portion of the gap forming each resistor extending parallel to an axis joining the adjacent electrodes and another portion of each gap extending transverse to said axis; and

a voltage supply connectable to a first electrode located at one end of the potential field to establish a potential difference between the first electrode and a second electrode located at an opposite end of the potential field, a plurality of intervening electrodes being positioned between the first and second electrodes, whereby the geometry of the potential field is a function of the resistance of the separate resistors between adjacent electrodes.

17. An edge linearization device, which comprises:

a surface having substantially uniform resistivity and defining a substantially rectangular area with four sides and four corners, said surface comprising a glass substrate with a thin film coating;

a plurality of electrodes disposed on said surface on each side of said area and electrically connected to said surface, said electrodes comprising a metal ink with a resistivity of less than about 1 ohm per square, with at least one of said electrodes having an extension wherein said extension of at least one of said electrodes on each side of said area is inwardly disposed into said area so that at least one extension is more inwardly disposed into said area than said electrodes and said electrodes have a greater conductivity than said surface so that, when an electric potential is selectively applied between said electrodes on a side and said electrodes on an opposing side, a unique electric potential exists corresponding to an object'"'"'s location on said surface;

at least one corner electrode disposed on said surface and located on each side of said surface and electrically connected thereto, wherein said corner electrode has a greater conductivity than said surface; and

a plurality of corner connectors disposed on said surface and electrically connected thereto and positioned adjacent said corners of said area; and

said electrodes, said corner electrodes, and said corner connectors are selectively disposed on said surface and include edges laterally therealong defining gaps therebetween and further include projections extending laterally therefrom and corresponding projection-receiving recesses extending thereinto with said edges thereof maintaining a constant selected distance from each other, said gaps thereby having a width equal to said constant distance and a length greater than the length of said electrodes, said corner electrodes and said corner connectors, to create gaps selectively shaped and dimensioned to define preselected resistivities between said electrodes, said corner electrodes, and said corner connectors,

whereby the lengths of said electrodes need protrude only minimally into the surface from sides thereof to define separate resistors of greater length, thereby optimizing the active area of said surface, and no resistive elements are otherwise connected between said electrodes, said corner electrodes, and said corner connectors.