Edge positioning accuracy in a mutual capacitive sense array

• US 8,593,431 B1
• Filed: 03/28/2011
• Issued: 11/26/2013
• Est. Priority Date: 08/24/2010
• Status: Active Grant

• Current Assignee: Parade Technologies, Ltd.
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Mandziy, Vasyl, Karpin, Oleksandr
• Primary Examiner(s): OSORIO, RICARDO
• Application Number:
  US13/073,141
• Time in Patent Office: 974 Days
• Field of Search: 345173-177, 178 1801- 1807, 178 1901- 1905
• US Class Current: 345/174
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• 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 mutual capacitive sense array configured to improve edge performance in tracking user inputs is described. A mutual capacitive sense array comprises a first and second plurality of sense elements and a visual display configured below the sense array. The display is configured to contact the first plurality of sense elements, where each of the first and second plurality of sense elements has a first area and second area, respectively, and wherein the second area is less than the first area. A method is described to scan a mutual capacitive sense array for a user input, the array comprising a first, second, and third plurality of sense elements, wherein the third plurality of sense elements are arranged in parallel along the exterior edge of the mutual capacitive sense array. The third plurality of sense elements effectively reduces the tracking error occurring at the edges of the mutual capacitive sense array.

Claims

1. A mutual capacitive sense array, the array comprising:

a first plurality of sense elements;

a second plurality of sense elements; and

a visual display disposed below the mutual capacitive sense array, wherein the visual display is aligned over the first plurality of sense elements, wherein the first plurality of elements are aligned wholly within a visual display area of the visual display, wherein the second plurality of elements are aligned wholly outside of the visual display area, wherein each of the first plurality of sense elements has a first area, and wherein each of the second plurality of sense elements has a second area, wherein the second area is less than first area.

2. The mutual capacitive sense array of claim 1, wherein the first plurality of sense elements are substantially diamond shaped.

3. The mutual capacitive sense array of claim 1, wherein the second plurality of sense elements are substantially half-diamond shaped.

4. The mutual capacitive sense array of claim 1, wherein the second plurality of sense elements are located substantially along the edges of the mutual capacitive sense array.

5. The mutual capacitive sense array of claim 1, wherein the second area is substantially 50% of the total area of the first area.

6. The mutual capacitive sense array of claim 1, wherein the visual display is a liquid crystal display (LCD).

7. The mutual capacitive sense array of claim 1, wherein the visual display is selected from the group consisting of a light emitting diode (LED) display, organic light emitting diode (OLED) display, plasma display, and flat panel display.

8. The mutual capacitive sense array of claim 1, wherein the plurality of capacitive sense elements comprises a third plurality of sense elements, wherein each of the third plurality of sense elements has a third area, wherein the second area is greater than 50% of the first area, and wherein the third area is less than 50% of the first area, and wherein the third plurality of sense elements are aligned along the edges of the visual display area.

9. The mutual capacitive sense array of claim 8, wherein the second area is substantially 75% of the first area, and wherein the third area is substantially 25% of the first area.

10. A mutual capacitive sense array, the array comprising:

a first plurality of sense elements;

a second plurality of sense elements; and

a third plurality of sense elements, wherein the second plurality of sense elements are disposed substantially along the interior edges of the mutual capacitive sense array, and wherein the third plurality of sense elements are disposed substantially along the exterior edges of the mutual capacitive sense array.

11. The mutual capacitive sense array of claim 10, further comprising connection lines, wherein the connections lines are configured to connect the mutual capacitive sense array to a capacitance sensor, and wherein the plurality of sense elements are substantially linear sense elements and are formed from the connections lines.

12. The mutual capacitive sense array of claim 10, wherein the third plurality of sense elements are comprised of a same type of material as the first and second plurality of sense elements.

13. A method to improve position tracking in a touch sense device, the method comprising:

scanning a mutual capacitive sense array for a user input, the mutual capacitive sense array comprising;

a first plurality of sense elements;

a second plurality of sense elements; and

a third plurality of sense elements arranged in parallel along the exterior of the mutual capacitive sense array; and

calculating the position of the user input based on the mutual capacitance of the first, second and third plurality of sense elements, wherein each of the second plurality of sense elements introduces a reduced accuracy in the calculation, and wherein the third plurality of sense elements improves the accuracy in the calculation.

14. The method of claim 13, wherein the reduced accuracy is caused by a non-centered center-of-mass for each of the second plurality of sense elements.

15. The method of claim 13, further comprising connection lines, wherein the connections lines are configured to connect the mutual capacitive sense array to a capacitance sensor, and wherein the third plurality of sense elements are formed from the connections lines.

16. The method of claim 13, wherein the third plurality of sense elements are comprised of a same type of material as the first and second plurality of sense elements.

17. The method of claim 13, wherein the first plurality of sense elements are substantially diamond shaped.

18. The method of claim 13, wherein the second plurality of sense elements are substantially half-diamond shaped.

19. The method of claim 13, wherein the second plurality of sense elements are located substantially along the edges of the mutual capacitive sense array.

20. The method of claim 13, wherein the third plurality of sense elements are comprised of a same type of material as the first and second plurality of sense elements.