System and Method for Detecting Locations of Touches on a Touch Sensor

• US 20110279409A1
• Filed: 05/13/2011
• Published: 11/17/2011
• Est. Priority Date: 05/14/2010
• Status: Active Grant

• Current Assignee: Elo Touch Solutions, Inc.
• Original Assignee: Elo Touch Solutions, Inc.
• Inventors: Lau, Francis, Quaderer, James G., Salaverry, Ricardo R., Kent, Joel C.
• Granted Patent: US 9,256,327 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• CPC Class Codes: G06F 2203/04105 Pressure sensors for measuring the pressure or force exerted on the touch surface without providing the touch position
• CPC Class Codes: G06F 2203/04107 Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds
• CPC Class Codes: G06F 2203/04108 Touchless 2D- digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface without distance measurement in the Z direction
• CPC Class Codes: G06F 2203/04112 Electrode mesh in capacitive digitiser: electrode for touch sensing is formed of a mesh of very fine, normally metallic, interconnected lines that are almost invisible to see. This provides a quite large but transparent electrode surface, without need for ITO or similar transparent conductive material
• CPC Class Codes: G06F 3/04164 Connections between sensors and controllers, e.g. routing lines between electrodes and connection pads
• 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 3/0443 using a single layer of sensing 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 projected capacitive touch sensor system includes a substrate that defines a plurality of non-overlapping areas. Each non-overlapping area includes a plurality of detection electrodes arranged in non-overlapping columns. The columns include a horizontal detection electrode that extends along substantially an entire height of a first column, and at least a second column of at least two vertical detection electrodes that are electrically isolated from one another. The system further includes a measuring circuit configured to measure a mutual capacitance between the horizontal detection electrode and each of the at least two vertical detection electrodes in a given area. A processing logic circuit of the system is configured to determine horizontal detection electrode and vertical detection electrode combinations that have a changed mutual capacitance. The processing logic is also configured to determine the touch location based on a location of the determined horizontal detection electrode and vertical electrode combinations.

Claims

1. A method for determining a touch location of a projected capacitive touch sensor, comprising:

providing a substrate that defines a plurality of non-overlapping areas, where each non-overlapping area includes a plurality of detection electrodes arranged in non-overlapping columns that include a horizontal detection electrode that extends along substantially an entire height of a first column, a second column of at least two vertical detection electrodes that are electrically isolated from one another, and a third column of at least two vertical detection electrodes formed of at least three electrode portions, wherein vertical detection electrodes in different columns are electrically isolated from one another, and wherein two vertical electrode portions separated only by the third vertical electrode portion in the third column are electrically connected;

measuring, in a given area, a mutual capacitance between the horizontal detection electrode and each of the at least two vertical detection electrodes in the second column, and between the horizontal detection electrode and each of the at least two vertical detection electrodes in the third column;

determining horizontal detection electrode and vertical detection electrode combinations that have a changed mutual capacitance;

determining the touch location based on a location of the determined horizontal detection electrode and vertical electrode combinations.

2. The method according to claim 1, further comprising:

selecting each of the plurality of non-overlapping areas individually; and

determining whether a touch has occurred in each selected area and, if so, a touch location, whereby selection of each area individually enables detection of more than one simultaneous touch locations.

3. The method according to claim 1, wherein the horizontal detection electrodes in different areas of the plurality of non-overlapping areas are electrically disconnected with respect to each other and the vertical detection electrodes.

4. The method according to claim 1, wherein measuring the mutual capacitance between the horizontal detection electrode and each of the at least two vertical detection electrodes further comprises:

driving a first of the at least two vertical detection electrodes with a first pulse to generate a first current flow through a first mutual capacitance formed between the first of the at least two vertical detection electrodes and the horizontal detection electrode; and

simultaneously driving a second of the at least two vertical detection electrodes with a second pulse to generate a second current flow through a second mutual capacitance formed between the second of the at least two vertical detection electrodes and the horizontal detection electrode, wherein the second pulse has a same shape as the first pulse and is 180 degrees out-of-phase with the first pulse.

5. The method according to claim 4, further comprising measuring, at the horizontal detection electrode, a combined current flowing through the first mutual capacitance and the second mutual capacitance.

6. The method according to claim 1, further comprising:

measuring a mutual capacitance between at least one vertical detection electrode of the second column and at least one vertical detection electrode of the third column.

7. The method according to claim 6, further comprising:

driving a first group of electrically connected vertical detection electrodes of the at least three vertical detection electrodes with a third pulse to generate a third current flow through a third mutual capacitance formed between the first group of electrically connected vertical detection electrodes and the horizontal detection electrode; and

simultaneously driving a second group of electrically connected vertical detection electrodes of the at least three vertical detection electrodes with a fourth pulse to generate a fourth current flow through a fourth mutual capacitance formed between the second group of electrically connected vertical detection electrodes and the horizontal detection electrode, wherein the third pulse has a same shape as the fourth pulse and is 180 degrees out-of-phase with the third pulse.

8. The method according to claim 7, wherein the pulse shape of the first and the second pulses match the pulse shape of the third and the fourth pulses and the phase of the third pulse matches the phase of one of the first and the second pulses.

9. The method according to claim 8, wherein the phase of the first pulse is either 0°

or 180°

, and the phase of the third pulse either 0°

or 180°

, and further comprising;

selecting all combination of phases of the first pulse and the second pulse; and

for each combination, measuring a combined current flow through the first, second, third, and fourth mutual capacitances.

10. The method according to claim 9, further comprising:

determining a pulse driver state associated with the combination of phases for which a maximum combined current flow is measured; and

determining a substrate location associated with the determine state.

11. A touch sensor system, comprising:

a substrate that defines a plurality of non-overlapping areas, where each non-overlapping area includes a plurality of detection electrodes arranged in non-overlapping columns that include a horizontal detection electrode that extends along substantially an entire height of a first column, and at least a second column of at least two vertical detection electrodes that are electrically isolated from one another;

a measuring circuit configured to measure a mutual impedance between the horizontal detection electrode and each of the at least two vertical detection electrodes in a given area;

processing logic configured to determine horizontal detection electrode and vertical detection electrode combinations that have a changed mutual impedance, wherein the processing logic is further configured to determine the touch location based on a location of the determined horizontal detection electrode and vertical electrode combinations.

12. The system according to claim 11, determination of the changed mutual impedance comprises determining a changed mutual resistance.

13. The system according to claim 11, determination of the changed mutual impedance comprises determining a changed mutual capacitance.

14. The system according to claim 11, further comprising:

a selector configured to select each of the plurality of non-overlapping areas individually; and

wherein the processing logic is configured to determine whether a touch has occurred in each selected area and, if so, a touch location, whereby selection of each area individually enables detection of more than one simultaneous touch locations.

15. The system according to claim 11, wherein the horizontal detection electrodes in different areas of the plurality of non-overlapping areas are electrically disconnected with respect to each other and the vertical detection electrodes.

16. The system according to claim 11, wherein the measuring circuit further comprises:

a pulse driver circuit that comprises;

a first output configured to drive a first of the at least two vertical detection electrodes with a first pulse to generate a first current flow through a first mutual capacitance formed between the first of the at least two vertical detection electrodes and the horizontal detection electrode; and

a second output configured to simultaneously drive a second of the at least two vertical detection electrodes with a second pulse to generate a second current flow through a second mutual capacitance formed between the second of the at least two vertical detection electrodes and the horizontal detection electrode, wherein the second pulse has a same shape as the first pulse and is 180 degrees out-of-phase with the first pulse.

17. The system according to claim 16, further comprising:

an integrator circuit configured to measure, at the horizontal detection electrode, a combined current flowing through the first mutual capacitance and the second mutual capacitance.

18. The system according to claim 17, further comprising:

a third column of at least three vertical detection electrodes, wherein adjacent vertical detection electrodes are electrically isolated from one another and vertical electrodes on either side of a given electrode in the third column are electrically connected, wherein the measuring circuit is configured to measure a mutual capacitance between the horizontal detection electrode and each of the at least three vertical detection electrodes in the third column.

19. The system according to claim 18, further comprising:

a second pulse driver circuit that comprises;

a first output configured to drive a first group of electrically connected vertical detection electrodes of the at least three vertical detection electrodes with a third pulse to generate a third current flow through a third mutual capacitance formed between the first group of electrically connected vertical detection electrodes and the horizontal detection electrode; and

a second output configured to simultaneously drive a second group of electrically connected vertical detection electrodes of the at least three vertical detection electrodes with a fourth pulse to generate a fourth current flow through a fourth mutual capacitance formed between the second group of electrically connected vertical detection electrodes and the horizontal detection electrode, wherein the third pulse has a same shape as the fourth pulse and is 180 degrees out-of-phase with the third pulse.

20. The system according to claim 19, wherein the pulse shape of the first and the second pulses match the pulse shape of the third and the fourth pulses and the phase of the third pulse matches the phase of one of the first and the second pulses.

21. The system according to claim 20, wherein the phase of the first pulse is either 0°

or 180°

, and the phase of the third pulse either 0°

or 180°

, and further comprising;

selection logic configured to select all combination of phases of the first pulse and the second pulse; and

for each combination, the measuring circuit is configured to measure a combined current flow through the first, second, third, and fourth mutual capacitances.

22. The system according to claim 21, wherein the processing logic is further configured to determine a pulse driver state associated with the combination of phases for which a maximum combined current flow is measured, and determine a substrate location associated with the determined state.

23. A touch sensor system, comprising:

a substrate that defines a plurality of non-overlapping areas, where each non-overlapping area includes a plurality of detection electrodes, the plurality of detection electrodes including;

a horizontal detection electrode that extends along substantially an entire height of an area, and

P pairs of vertical detection electrodes that are electrically isolated from one another, where P is at least 2, and where the P pairs of vertical detection electrodes define 2^P non-overlapping vertical detection zones in the area.

24. The touch sensor system according to claim 23 further comprising a controller configured to select each of the plurality of non-overlapping areas individually and to determine whether a touch has occurred in each selected area and, if so, a touch location, whereby selection of each area individually enables detection of more than one simultaneous touch locations.

25. The touch sensor system according to claim 23 further comprising a controller configured to measure the mutual capacitance between the horizontal detection electrode and each of at least two vertical detection electrodes by driving a first of the at least two vertical detection electrodes with a first pulse to generate a first current flow through a first mutual capacitance formed between the first of the at least two vertical detection electrodes and the horizontal detection electrode, and by simultaneously driving a second of the at least two vertical detection electrodes with a second pulse to generate a second current flow through a second mutual capacitance formed between the second of the at least two vertical detection electrodes and the horizontal detection electrode, wherein the second pulse has a same shape as the first pulse and is 180 degrees out-of-phase with the first pulse.

26. The touch sensor system according to claim 23, wherein the horizontal detection electrode is in a first column, and further comprising a controller configured to measure a mutual capacitance between at least one vertical detection electrode in a second column and at least one vertical detection electrode in a third column.

27. The touch sensor system according to claim 23, wherein the vertical detection electrodes of each pair are not in the same column.