Mutual and self capacitance touch measurements in touch panel

• US 9,886,141 B2
• Filed: 11/15/2013
• Issued: 02/06/2018
• Est. Priority Date: 08/16/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Yousefpor, Marduke
• Primary Examiner(s): Cerullo, Liliana
• Application Number:
  US14/082,003
• Publication Number:
  US 20150049043A1
• Time in Patent Office: 1,544 Days
• CPC Class Codes: G06F 2203/04111 Cross over in capacitive digitiser, i.e. details of structures for connecting electrodes of the sensing pattern where the connections cross each other, e.g. bridge structures comprising an insulating layer, or vias through substrate
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/04186 Touch location disambiguation
• 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 panel capable of measuring both mutual and self capacitance is disclosed. The touch panel can measure self capacitance and mutual capacitance at various electrode patterns and, based on the self capacitance measurements, the mutual capacitance measurements, or both, calculate a touch signal indicative of an object touching or hovering over the touch panel. In some examples, the measurements can also be used to determine a correction factor, indicative of an adverse condition at the touch panel, and the correction factor used to correct the touch signal for the adverse condition. The touch panel can have a row-column electrode pattern or a pixelated electrode pattern.

Claims

1. A method for measuring mutual and self capacitance at a touch panel comprising:

measuring mutual and self capacitances at multiple touch node patterns in the touch panel;

determining one or more correction factors, the value of each correction factor being a function of both the measured mutual and self capacitances; and

calculating a touch signal based on applying the one or more correction factors to the measured mutual or self capacitances, the touch signal indicative of an object proximate to the touch panel.

2. The method of claim 1, wherein the touch panel has a row-column electrode configuration, the touch panel including multiple rows of conductive traces and multiple columns of conductive traces, the columns crossing the rows to form mutual capacitances therebetween.

3. The method of claim 1, wherein the touch signal comprises a mutual capacitance touch signal.

4. The method of claim 1, wherein the measuring comprises:

simultaneously measuring a first self capacitance of row conductive traces and a second self capacitance of column conductive traces of the touch panel at a first node pattern;

measuring a first mutual capacitance between a pair of the row conductive traces at a second node pattern; and

measuring a second mutual capacitance between a pair of the column conductive traces at a third node pattern.

5. The method of claim 1, wherein the measuring comprises:

simultaneously measuring a first self capacitance of row conductive traces and a second self capacitance of column conductive traces of the touch panel at a first node pattern; and

simultaneously measuring a first mutual capacitance between a pair of the row conductive traces and a second mutual capacitance between a pair of the row and column conductive traces at a second node pattern.

6. The method of claim 1, wherein the calculating further comprises:

calculating the touch signal corrected for at least one of the proximate object being poorly grounded, water on the touch panel, or noise introduced into the touch panel.

7. The method of claim 1, wherein the touch panel has a pixelated electrode configuration, the touch panel including an array of electrodes to form self capacitances between the electrodes and the object.

8. The method of claim 1, wherein the touch signal comprises a self capacitance touch signal.

9. The method of claim 1, wherein the measuring comprises:

measuring a self capacitance globally from electrodes of the touch panel at a first node pattern; and

measuring a mutual capacitance between a pair of the electrodes at a second node pattern.

10. The method of claim 1, wherein the measuring comprises:

simultaneously measuring a self capacitance locally from at least one of electrodes of the touch panel and a mutual capacitance between a pair of the electrodes at a first node pattern.

11. The method of claim 1, wherein the measuring comprises:

measuring a first self capacitance globally from electrodes of the touch panel at a first node pattern; and

measuring a second self capacitance locally from at least one of the electrodes at a second node pattern.

12. The method of claim 1,

wherein the correction factor is applied to the measured mutual or self capacitances to correct for one of a grounding condition of a proximate object, water disposed on the touch panel, or noise introduced into the touch panel.

13. The method of claim 12, wherein the determining comprises:

determining the correction factor based on at least one of a first measurement of a first self capacitance of row conductive traces in the touch panel, a second measurement of a second self capacitance of column conductive traces in the touch panel, a third measurement of a first mutual capacitance between pairs of the row conductive traces, a fourth measurement of a second mutual capacitance between pairs of the column conductive traces, or a fifth measurement of a third mutual capacitance between pairs of the row and column conductive traces.

14. The method of claim 12, wherein the determining comprises:

determining the correction factor based on at least one of a first measurement of a first self capacitance globally from electrodes of the touch panel, a second measurement of a second self capacitance locally from at least one of the electrodes, or a third measurement of a mutual capacitance between a pair of the electrodes.

15. A touch device comprising:

a touch panel having a set of touch nodes capable of measuring a mutual capacitance touch and a self capacitance touch; and

a processor capable of

receiving at least one set of mutual capacitance touch measurements and at least one set of self capacitance touch measurements taken from multiple patterns of the touch nodes,

determining one or more correction factors, the value of each correction factor being a function of both the at least one set of mutual capacitance touch measurements and the at least one set of self capacitance touch measurements; and

calculating a touch signal at the touch panel based on applying the one or more correction factors to at least one of the set of mutual capacitance touch measurements and the set of self capacitance touch measurements.

16. The device of claim 15, wherein the set of touch nodes comprises:

multiple rows of conductive traces, each row trace having alternate wide and narrow portions, the wide portions tapering at distal ends to couple to the narrow portions; and

multiple columns of conductive traces, each column trace having wide portions tapering at distal ends and bridges connecting the tapered distal ends of the wide portions,

wherein the rows and columns cross each other at the narrow portions of the row traces and the bridges of the column traces.

17. The device of claim 15, wherein a first pattern of the touch nodes comprises rows and columns of conductive traces of the touch panel stimulated simultaneously to provide the set of self capacitance measurements,

wherein a second pattern of the touch nodes comprises a pair of the row conductive traces, one of the row pair being stimulated to drive the other of the row pair to transmit at least some of the set of mutual capacitance measurements,

wherein a third pattern of the touch nodes comprises a pair of the column conductive traces, one of the column pair being stimulated to drive the other of the column pair to transmit at least others of the set of mutual capacitance measurements, and

wherein the processor receives the sets of mutual and self capacitance measurements from the first, second, and third patterns of the nodes.

18. The device of claim 15, wherein the set of touch nodes comprises:

an array of electrodes, each electrode having shaved corners to provide a distance from another electrode.

19. The device of claim 15, wherein a first pattern of the touch nodes comprises electrodes of the touch panel stimulated simultaneously to provide the set of self capacitance measurements,

wherein a second pattern of the touch nodes comprises a first of the electrodes being a drive electrode, a second of the electrodes being a ground electrode, a third of the electrodes being a sense electrode, and a fourth of the electrodes being a ground electrode, the first electrode being stimulated to drive the third electrode to transmit the set of mutual capacitance measurements, and

wherein the processor receives the sets of mutual and self capacitance measurements from the first and second patterns of the nodes.

20. The device of claim 15, wherein a first pattern of the touch nodes comprises a first electrode of the touch panel being a drive electrode, a second electrode being a ground electrode, a third electrode being a sense electrode, and a fourth electrode being a ground electrode, the first electrode being stimulated to provide the set of self capacitance measurements and to drive the third electrode to provide the set of mutual capacitance measurements simultaneously, and

wherein the processor receives the sets of mutual and self capacitance measurements from the first pattern of the nodes.

21. The device of claim 15, wherein a first pattern of the touch nodes comprises electrodes of the touch panel stimulated simultaneously to provide some of the set of self capacitance measurements,

wherein a second pattern of the touch nodes comprises a first of the electrodes being a drive electrode, a second of the electrodes, a third of the electrodes being a ground electrode, and a fourth of the electrodes, the first electrode, second electrode, and fourth electrode being stimulated with stimulation signals, the first electrode being sensed to provide others of the set of self capacitance measurements, and the second electrode and fourth electrode not being sensed, and

wherein the processor receives the set of self capacitance measurements from the first and second patterns of the nodes.

22. The device of claim 15 comprising at least one of a mobile phone, a media player, or a portable computer.

23. A method for using mutual and self capacitance measurements at a touch panel, comprising:

measuring a self capacitance and a mutual capacitance at touch nodes of the touch panel, the measurements indicative of an object proximate to the touch panel;

determining one or more correction factors, the value of each correction factor being a function of both the self and mutual capacitance measurements; and

calculating a touch signal based on applying the one or more correction factors to the self or mutual capacitance measurements, the touch signal corrected for at least one of a grounding condition of the object, water disposed on the touch panel, or noise introduced into the touch panel.