Touch sensor with electrode array

• US 7,973,771 B2
• Filed: 04/12/2007
• Issued: 07/05/2011
• Est. Priority Date: 04/12/2007
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Geaghan, Bernard O.
• Primary Examiner(s): Mengistu; Amare
• Assistant Examiner(s): ZUBAJLO, JENNIFER L
• Application Number:
  US11/734,553
• Publication Number:
  US 20080252608A1
• Time in Patent Office: 1,545 Days
• Field of Search: 345/173
• US Class Current: 345/173
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G06F 3/0448 Details of the electrode shape, e.g. for enhancing the detection of touches, for generating specific electric field shapes, for enhancing display quality

Abstract

A touch sensor is provided that includes an array of discrete electrodes disposed over a touch sensitive area, the electrodes being elongated in a first direction and having a variable width measured in a second direction that is perpendicular to the first direction. A touch location can be determined by simultaneously applying an electrical signal to a plurality of positions on the touch sensor, the touch location along the first direction being determined by comparing a capacitive coupling between the touch implement and the plurality of positions in the touch sensor, and the touch location along the second direction being determined by comparing a resistive coupling between the touch implement and the plurality of positions in the touch sensor.

Claims

1. A capacitive touch sensor comprising a plurality of discrete elongated electrically resistive electrodes disposed in a touch sensitive area, each discrete electrode having a length along a first direction and a width along a second direction orthogonal to the first direction, the width of each elongated electrode varying along the first direction, wherein when a touch implement is applied to a touch location in the touch sensitive area, the touch location is determined by simultaneously applying an electrical signal to a plurality of positions on the touch sensor, the touch location along the first direction being determined by comparing a capacitive coupling between the touch implement and the plurality of positions in the touch sensor, and the touch location along the second direction being determined by comparing a resistive coupling between the touch implement and the plurality of positions in the touch sensor.

2. The capacitive touch sensor of claim 1, wherein the width of each elongated electrode varies linearly along the length of the electrode.

3. The capacitive touch sensor of claim 1, wherein at least one elongated electrode has a wedge shape.

4. The capacitive touch sensor of claim 1, wherein each elongated electrode has a triangular shape with two sides connecting a tip to a base.

5. The capacitive touch sensor of claim 4, wherein a first plurality of bases are arranged along a first linear sequence and a second plurality of bases are arranged along a second linear sequence.

6. The capacitive touch sensor of claim 5, wherein each of the first and second linear sequences includes a plurality of tips from the plurality of elongated triangular electrodes.

7. The capacitive touch sensor of claim 5, further comprising first and second electrically resistive edge bars disposed to have lengths that extend along the first and second linear sequences of bases, respectively.

8. The capacitive touch sensor of claim 7, wherein each of the first and second resistive edge bars comprises two discrete tapered segments, the two segments being arranged to taper oppositely along the length of the edge bar.

9. The capacitive touch sensor of claim 7, wherein the first and second edge bars are not resistively connected to the plurality of discrete elongated electrodes.

10. The capacitive touch sensor of claim 7, wherein the first edge bar is electrically connected to the second edge bar.

11. The capacitive touch sensor of claim 7, wherein the first and second edge bars are in the touch sensitive area.

12. The capacitive touch sensor of claim 7, wherein signals are applied to the edge bars to that capacitive coupling of a touch input to the edge bars can be determined.

13. The capacitive touch sensor of claim 12, wherein the degree of capacitive coupling of a touch input to the edge bars is used to correct errors in touch position determination.

14. The capacitive touch sensor of claim 5, wherein the first plurality of bases are electrically connected to a first subset of the plurality of positions in the touch sensor, and the second plurality of bases are electrically connected to a second subset of the plurality of positions in the touch sensor.

15. The capacitive touch sensor of claim 1, wherein the plurality of electrodes includes a first electrode located at one end of the touch sensitive area along the second direction, a last electrode located at an opposing end of the touch sensitive area along the second direction, and middle electrodes located between the first and last electrodes, and further wherein the first and last electrodes each cover a smaller area than any of the middle electrodes.

16. The capacitive touch sensor of claim 1, wherein a wider width of a first elongated electrode is adjacent to a narrower width of a second elongated electrode, and wherein a narrower width of the first elongated electrode is adjacent to a wider width of the second elongated electrode.

17. The capacitive touch sensor of claim 1, wherein a spacing between at least two elongated electrodes is substantially a constant along the first direction.

18. The capacitive touch sensor of claim 1, wherein the plurality of positions in the touch sensor are along a periphery of the touch sensitive area.

19. A capacitive touch sensor comprising a plurality of discrete electrodes disposed in a touch sensitive area, each discrete electrode having a length along a first direction and a width along a second direction, the width of each electrode varying along the first direction, wherein a touch location of a touch implement is determined for the first direction when a plurality of positions along a periphery of the touch sensitive area are electrically energized, wherein a ratio of a capacitive coupling between the touch implement and a first pair of positions in the plurality of positions changes when the touch location is changed along the first direction but the ratio remains essentially unchanged when the touch location is changed along the second direction, and wherein a ratio of a resistive coupling between the touch implement and the first pair at positions in the plurality of positions changes when the touch location is changed along the second direction but the ratio remains essentially unchanged when the touch location is changed along the first direction.

20. A capacitive, touch sensor comprising at least one sensor array, the sensor array comprising:

a first plurality of triangular electrodes interdigitated with a second plurality of triangular electrodes, the electrodes in the first and second plurality being elongated and having a length in a first direction and a width in a second direction orthogonal to the first direction, the width of each triangular electrode varying along the first direction, and disposed in a touch sensitive area such that a side of each triangular electrode faces and is substantially parallel to a side of an adjacent triangular electrode; and

a third plurality of triangular electrodes oriented orthogonally to the first direction and electrically connected to the first plurality of triangular electrodes through a first resistive divider,

wherein when a touch implement is applied to a touch location in the touch sensitive area, the touch location is determined by electrically energizing both ends of the first resistive divider and comparing signals generated by capacitive and resistive coupling between the touch implement and the first and second resistive dividers, wherein the signals generated by capacitive coupling determine the touch location along the first direction, and the signals generated by the resistive coupling determine the touch location along the second direction.

21. The capacitive touch sensor of claim 20, further comprising a fourth plurality of triangular electrodes oriented orthogonally to the first direction and electrically connected to the second plurality of triangular electrodes through a second resistive divider.

22. The capacitive touch sensor of claim 20, wherein the at least one sensor array comprises four sensor arrays tiled together so that each sensor array has two edges adjacent to other sensor arrays.