Pointing device using capacitance sensor

• US 20080078590A1
• Filed: 09/24/2007
• Published: 04/03/2008
• Est. Priority Date: 09/29/2006
• Status: Active Grant

• Current Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Sequine, Dennis R.
• Granted Patent: US 8,902,173 B2
• Time in Patent Office: Days
• US Class Current: 178/18.06
• CPC Class Codes: G06F 3/03548 Sliders, in which the moving part moves in a plane
• 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

Apparatuses and methods for determining a deflection of a moveable conductive plate that is moved over a capacitive sensing device. The method may include moving the moveable conductive plate over sensor elements of the capacitive sensing device, and determining the deflection of the moveable conductive plate. In determining the deflection, a deflection magnitude and a deflection direction may be determined by calculating a vector of x- and y-directions or a vector of a radius and an angle.

Claims

1. A method, comprising:

moving a moveable conductive plate over a capacitive sensing device; and

determining a deflection of the moveable conductive plate.

2. The method of claim 1, wherein determining the deflection comprises determining a deflection magnitude and a deflection direction.

3. The method of claim 2, wherein determining the deflection magnitude and deflection direction comprises calculating a vector in at least one of x- and y-directions, or of a radius and an angle.

4. The method of claim 2, wherein determining the deflection magnitude and deflection direction comprises computing a two-sided centroid.

5. The method of claim 4, wherein computing the two-sided centroid comprises:

computing a minimum centroid and a maximum centroid; and

combining the minimum and maximum centroids to compute the deflection magnitude and the deflection direction.

6. The method of claim 1, further comprising:

measuring a first capacitance and a second capacitance on a first sensor element and a second sensor element, respectively, while the moveable conductive object is located in a known position relative to the first and second sensor elements; and

measuring a third capacitance and a fourth capacitance on the first and second sensor elements, respectively, while the moveable conductive object is located in a second position, wherein determining the deflection comprises determining the deflection based on the first, second, third, and fourth capacitances.

7. The method of claim 6, wherein determining the deflection comprises computing a magnitude and direction vector that is representative of the change in capacitance on the first and second sensor elements from the known position to the second position.

8. The method of claim 6, further comprising automatically centering the moveable conductive object to the known position after the moveable conductive object is moved from the known position to the second position.

9. A pointing device, comprising:

a plurality of sensor elements disposed in a first plane; and

a moveable object configured to move in a second plane that is substantially parallel to the first plane, wherein a portion of the surface of the moveable object is a conductive surface.

10. The pointing device of claim 9, further comprising a self-centering device coupled to the moveable object, wherein the self-centering device is configured to center the moveable object to a known position after being moved, wherein the self-centering device comprises a spring mechanism.

11. The pointing device of claim 9, further comprising:

a housing coupled to the moveable object and the plurality of sensor elements; and

a spring mechanism coupled between the housing and the moveable object, wherein the spring mechanism is configured to return the moveable object to a known position.

12. The pointing device of claim 11, further comprising a plurality of posts disposed to surround the outer circumference of the moveable object, wherein the spring mechanism is a circumferential linear spring disposed around the plurality of posts.

13. The pointing device of claim 11, further comprising a plurality of posts disposed to surround the outer circumference of the moveable object, wherein the spring mechanism is an O-ring of elastic material that is disposed around the plurality of posts.

14. The pointing device of claim 9, further comprising an insulating layer between the first and second planes.

15. The pointing device of claim 9, wherein the plurality of sensor elements are disposed in a substantially circular pattern, wherein the moveable object comprises a conductive trace, wherein the outer diameter of the plurality of sensor elements in the substantially circular pattern is substantially aligned with the center of the conductive trace when the moveable object is in a known position, and wherein each of the plurality of sensor elements comprises a tapered shape that tapers towards the center of the substantially circular pattern.

16. The pointing device of claim 9, wherein the plurality of sensor elements are disposed in a ring configuration, wherein the plurality of sensor elements from an outer sensing area, wherein the moveable object comprises a conductive trace, wherein the outer diameter of the plurality of sensor elements in the ring configuration is substantially aligned with the center of the conductive trace when the moveable object is in a known position, and wherein the pointing device further comprises a button disposed in an inner sensing area that is within the outer sensing area.

17. An apparatus, comprising

a processing device configured to receive a plurality of signals from a plurality of sensor elements and to determine a deflection of a moveable conductive plate that is moved relative to the plurality of sensor elements based on the plurality of signals.

18. The apparatus of claim 17, further comprising a plurality of sensor elements disposed in a first plane of a circuit board, wherein the processing device is coupled to the circuit board, and wherein the moveable conductive plate is configured to move in a second plane that is substantially parallel to the first plane.

19. The apparatus of claim 18, further comprising:

a housing coupled to the circuit board, wherein circuit board is stationary relative to the housing;

an insulating layer disposed between the plurality of sensor elements and the moveable conductive plate; and

the moveable conductive plate coupled to the housing by a spring mechanism, wherein the spring mechanism is configured to return the moveable conductive plate to a known position after being moved.

20. The apparatus of claim 19, wherein the housing, circuit board, and moveable object are disposed in a joystick of a keyboard.