System and method for detecting locations of touches on a touch sensor

• US 9,256,327 B2
• Filed: 05/13/2011
• Issued: 02/09/2016
• Est. Priority Date: 05/14/2010
• Status: Active Grant

• Current Assignee: Elo Touch Solutions, Inc.
• Original Assignee: Elo Touch Solutions, Inc.
• Inventors: Salaverry, Ricardo R., Quaderer, James G., Lau, Francis, Kent, Joel C.
• Primary Examiner(s): NATALINI, JEFF WILLIAM
• Application Number:
  US13/107,565
• Publication Number:
  US 20110279409A1
• Time in Patent Office: 1,733 Days
• US Class Current: 1/1
• 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 with a plurality of non-overlapping areas, wherein each non-overlapping area includes a horizontal detection electrode in a first column and a second column with a plurality of vertical detection electrodes;

measuring a first mutual capacitance between the horizontal detection electrode and a vertical detection electrode from the plurality of vertical detection electrodes;

measuring a second mutual capacitance between the horizontal detection electrode and another vertical detection electrode from the plurality of vertical detection electrodes;

determining one or more horizontal detection electrode and vertical detection electrode combinations based on a change in the first mutual capacitance and the second mutual capacitance;

determining a digitized capacitance value based on the change in the first and the second mutual capacitances; and

determining the touch location based on a location of the one or more determined horizontal detection electrode and vertical electrode combinations and the digital capacitance value.

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 a touch location within the selected area, whereby selection of each area individually enables detection of more than one simultaneous touch location.

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 plurality of vertical detection electrodes.

4. The method according to claim 1, wherein:

measuring the first mutual capacitance further comprises driving the vertical detection electrode from the plurality of vertical detection electrodes with a first pulse to generate a first current flow through the first mutual capacitance; and

measuring the second mutual capacitance further comprises simultaneously driving the another vertical detection electrode from the plurality of vertical detection electrodes with a second pulse to generate a second current flow through the second mutual capacitance, wherein the second pulse has a same first 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 4, wherein the substrate includes a third column with a plurality of vertical detection electrodes, the method further comprising:

measuring a third mutual capacitance by driving a vertical detection electrode from the plurality of vertical detection electrodes in the third column with a third pulse to generate a third current flow through a third mutual capacitance formed between the vertical detection electrode from the plurality of vertical detection electrodes in the third column and the horizontal detection electrode; and

measuring a fourth mutual capacitance by simultaneously driving another vertical detection electrode from the plurality of vertical detection electrodes in the third column with a fourth pulse to generate a fourth current flow through a fourth mutual capacitance formed between the another vertical detection electrode from the plurality of vertical detection electrodes in the third column and the horizontal detection electrode, wherein the third pulse has a same second shape as the fourth pulse and is 180 degrees out-of-phase with the fourth pulse.

7. The method according to claim 6, wherein the first shape of the first and the second pulses match the second 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.

8. The method according to claim 7, 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 combinations 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.

9. The method according to claim 8, further comprising:

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

determining a substrate location associated with the pulse driver state.

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

measuring a mutual capacitance between at least two vertical detection electrodes from the plurality of vertical detection electrodes.

11. The method according to claim 1, wherein the substrate includes a third column with a plurality of vertical detection electrodes, the method further comprising:

measuring a third mutual capacitance between the horizontal detection electrode and a vertical detection electrode from the plurality of vertical detection electrodes in the third column;

measuring a fourth mutual capacitance between the horizontal detection electrode and another vertical detection electrode from the plurality of vertical detection electrodes in the third column; and

determining the digital capacitance value based on the change in the third mutual capacitance and the fourth mutual capacitance.

12. The method according to claim 11, wherein:

the determining the one or more horizontal detection electrode and vertical detection electrode combinations is based on the third and the fourth mutual capacitances; and

the determining the touch location is based on the digital capacitance value.

13. The method according to claim 11, wherein at least two of the vertical detection electrodes from the plurality of vertical detection electrodes in the third column are electrically connected.

14. The method according to claim 1, wherein at least two of the vertical detection electrodes from the plurality of vertical detection electrodes in the second column are electrically connected.

15. A touch sensor system, comprising:

a substrate with a plurality of non-overlapping areas, wherein each non-overlapping area includes a horizontal detection electrode in a first column and a second column with a plurality of vertical detection electrodes;

a measuring circuit configured to measure a first mutual impedance between the horizontal detection electrode and a vertical detection electrode from the plurality of vertical detection electrodes and to measure a second mutual impedance between the horizontal detection electrode and another vertical detection electrode from the plurality of vertical detection electrodes; and

processing logic configured to;

determine one or more horizontal detection electrode and vertical detection electrode combinations based on a change in the first mutual impedance and the second mutual impedance;

determine a digitized capacitance value based on the change in the first and the second mutual impedances; and

determine the touch location based on a location of the determined horizontal detection electrode and vertical electrode combinations and the digital capacitance value.

16. The system according to claim 15, wherein the processing logic is further configured to determine a change in mutual resistance.

17. The system according to claim 15, wherein the processing logic is further configured to determine a change in mutual capacitance.

18. The system according to claim 15, 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 a touch location within the selected area, whereby selection of each area individually enables detection of more than one simultaneous touch locations.

19. The system according to claim 15, 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 plurality of vertical detection electrodes.

20. The system according to claim 15, wherein the measuring circuit further comprises a first pulse driver circuit that comprises:

a first output configured to drive the vertical detection electrode from the plurality of vertical detection electrodes with a first pulse to generate a first current flow through a first mutual capacitance; and

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

21. The system according to claim 20, 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.

22. The system according to claim 21, further comprising:

a plurality of vertical detection electrodes in a third column; and

a second pulse driver circuit that comprises;

a third output configured to drive a vertical detection electrode of the plurality of vertical detection electrodes in the third column with a third pulse to generate a third current flow through a third mutual capacitance formed between the vertical detection electrode of the plurality of vertical detection electrodes in the third column and the horizontal detection electrode; and

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

23. The system according to claim 22, wherein the first shape of the first and the second pulses match the second 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.

24. The system according to claim 23, 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 combinations 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.

25. The system according to claim 24, wherein the processing logic is further configured to determine a pulse driver state associated with a combination of phases for which a maximum combined current flow is measured, and determine a substrate location associated with the pulse driver state.

26. A touch sensor system, comprising:

a substrate with a plurality of non-overlapping areas, where each non-overlapping area includes a plurality of detection electrodes, the plurality of detection electrodes configured in at least three columns and including;

a horizontal detection electrode in a first column;

P pairs of vertical detection electrodes that are electrically isolated from one another, wherein P is at least 2, and wherein the P pairs of vertical detection electrodes define (2*P) non-overlapping vertical detection zones in the area, a second column comprising at least one pair of vertical detection electrodes and a third column comprising at least one pair of vertical detection electrodes;

a controller configured to measure a first mutual capacitance between the horizontal detection electrode and a vertical detection electrode in the pair of vertical detection electrodes in the second column, and configured to measure a second mutual capacitance between the horizontal detection electrode and another vertical detection electrode in the pair of vertical detection electrodes in the second column; and

processing logic configured to;

determine horizontal detection electrode and vertical detection electrode combinations based on a change in the first mutual capacitance and the second mutual capacitance;

determine a digitized capacitance value based on the change in the first mutual capacitance and the second mutual capacitance; and

determine a touch location based on a location of the horizontal detection electrode and vertical electrode combinations and the digitized capacitance.

27. The touch sensor system according to claim 26, wherein the controller is further 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 within the selected area, whereby selection of each area individually enables detection of more than one simultaneous touch locations.

28. The touch sensor system according to claim 26, where the controller is further configured to measure the first mutual capacitance by driving the vertical detection electrode in the pair of vertical detection electrodes in the second column with a first pulse to generate a first current flow through the first mutual capacitance, and by simultaneously driving the another vertical detection electrode in the pair of vertical detection electrodes in the second column with a second pulse to generate a second current flow through the second mutual capacitance, wherein the second pulse has a same first shape as the first pulse and is 180 degrees out-of-phase with the first pulse.

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