TOUCH PAD DEVICE AND METHOD FOR DETERMINING A POSITION OF AN INPUT OBJECT ON THE DEVICE USING CAPACITIVE COUPLING

• US 20100147600A1
• Filed: 12/11/2008
• Published: 06/17/2010
• Est. Priority Date: 12/11/2008
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Orsley, Timothy James
• Granted Patent: US 9,128,543 B2
• Time in Patent Office: Days
• US Class Current: 178/18.30
• CPC Class Codes: G06F 2203/0339 Touch strips, e.g. orthogonal touch strips to control cursor movement or scrolling; single touch strip to adjust parameter or to implement a row of soft keys
• CPC Class Codes: G06F 3/03547 Touch pads, in which fingers can move on a surface
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: H04M 2250/22 including a touch pad, a touch sensor or a touch detector

Abstract

A touch pad device and method for determining a position of an input object on the device uses multiple sensing electrodes to produce signals induced by mutual capacitive coupling that are dependent on which conductors of the device are being electrically contacted by the input object. These signals are then processed to determine the position of the input object on the touch pad device.

Claims

1. A touch pad device comprising:

a substrate having opposing first and second surfaces;

a drive electrode and multiple sensing electrodes on the second surface;

a plurality of conductors on the first surface, each of the conductors being positioned on the first surface such that portions of at least two of the multiple sensing electrodes are situated directly across that conductor on the second surface;

a drive circuit configured to generate a drive signal, the drive circuit being electrically connected to the drive electrode to supply the drive signal to the drive electrode to generate coupling signals in the multiple sensing electrodes, the coupling signals being dependent on any electrical contact between an input object and at least one of the conductors;

multiple signal measuring units electrically connected to the multiple sensing electrodes to measure the coupling signals in the multiple sensing electrodes and to produce output signals; and

a processing unit connected to the multiple signal measuring units to process the output signals to determine which of the conductors is being electrically contacted by the input object to determine a position of the input object.

2. The touch pad device of claim 1 wherein the substrate is rectangular in shape.

3. The touch pad device of claim 2 wherein the multiple sensing electrodes include first and second sensing electrodes that are in the shape of a right triangle, the first and second sensing electrodes being positioned on the second surface of the substrate such that the drive electrode is situated between the first and second sensing electrodes.

4. The touch pad device of claim 3 wherein the first and second sensing electrodes are positioned on the second surface of the substrate in a rectangular arrangement.

5. The touch pad device of claim 1 wherein the substrate is an annular-like substrate.

6. The touch pad device of claim 5 wherein the multiple sensing electrodes include first, second, third and fourth sensing electrodes that positioned on the second surface of the substrate such that the first, second, third and fourth sensing electrodes are separated from each other by the drive electrode.

7. The touch pad device of claim 6 wherein the first and second sensing electrodes are positioned on the second surface of the substrate between an outer edge of the substrate and the drive electrode and the third and fourth sensing electrodes are positioned on the second surface of the substrate between an inner edge of the substrate and the drive electrode.

8. The touch pad device of claim 1 wherein each of the multiple signal measuring units includes an analog-to-digital converter to measure current in each of the multiple sensing electrodes.

9. The touch pad device of claim 1 wherein the drive circuit is configured to generate the drive signal in the form of a rectangular wave signal.

10. A method for determining a position of a target object on a touch pad device, the touch pad device including a substrate having opposing first and second surfaces, a drive conductive electrode and multiple sensing electrodes on the second surface, and a plurality of conductors on the first surface, each of the conductors being positioned on the first surface such that portions of at least two of the multiple sensing electrodes are directly across that conductor on the second surface, the method comprising:

applying a drive signal to the drive electrode of the touch pad device to generate coupling signals in the multiple sensing electrodes, the coupling signals being dependent on any electrical contact between an input object and at least one of the conductors;

measuring the coupling signals in the multiple sensing electrodes of the touch pad device to produce output signals; and

processing the output signals to determine which of the conductors is being electrically contacted by the input object to determine the position of the input object.

11. The method of claim 10 wherein the applying the drive signal includes applying a rectangular wave drive signal to the drive electrode of the touch pad device to generate the coupling signals in the multiple sensing electrodes.

12. The method of claim 10 wherein the measuring the coupling signals in the multiple sensing electrodes of the touch pad device includes performing analog-to-digital conversion to measure current in each of the multiple sensing electrodes to produce the output signals.

13. The method of claim 10 wherein the substrate is rectangular in shape and wherein the multiple sensing electrodes include first and second sensing electrodes that are in the shape of a right triangle, the first and second sensing electrodes being positioned on the second surface of the substrate such that the drive electrode is situated between the first and second sensing electrodes.

14. The method of claim 10 wherein the substrate is an annular-like substrate and wherein the multiple sensing electrodes include first, second, third and fourth sensing electrodes that positioned on the second surface of the substrate such that the first, second, third and fourth sensing electrodes are separated from each other by the drive electrode.

15. The method of claim 14 wherein the first and second sensing electrodes are positioned on the second surface of the substrate between an outer edge of the substrate and the drive electrode and the third and fourth sensing electrodes are positioned on the second surface of the substrate between an inner edge of the substrate and the drive electrode.

16. A touch pad device comprising:

an annular-like substrate having opposing first and second surfaces;

a drive electrode and multiple sensing electrodes on the second surface;

a plurality of conductors on the first surface, each of the conductors being positioned on the first surface such that portions of at least two of the multiple sensing electrodes are situated directly across that conductor on the second surface;

a drive circuit configured to generate a drive signal, the drive circuit being electrically connected to the drive electrode to supply the drive signal to the drive electrode to generate coupling signals in the multiple sensing electrodes, the coupling signals being dependent on any electrical contact between an input object and at least one of the conductors;

multiple signal measuring units electrically connected to the multiple sensing electrodes to measure the coupling signals in the multiple sensing electrodes and to produce output signals; and

a processing unit connected to the multiple signal measuring units to process the output signals to determine which of the conductors is being electrically contacted by the input object to determine a position of the input object.

17. The touch pad device of claim 16 wherein the multiple sensing electrodes include first, second, third and fourth sensing electrodes that positioned on the second surface of the substrate such that the first, second, third and fourth sensing electrodes are separated from each other by the drive electrode.

18. The touch pad device of claim 17 wherein the first and second sensing electrodes are positioned on the second surface of the substrate between an outer edge of the substrate and the drive electrode and the third and fourth sensing electrodes are positioned on the second surface of the substrate between an inner edge of the substrate and the drive electrode.

19. The touch pad device of claim 16 wherein each of the multiple signal measuring units includes an analog-to-digital converter to measure current in each of the multiple sensing electrodes.

20. The touch pad device of claim 16 wherein the drive circuit is configured to generate the drive signal in the form of a rectangular wave signal.