Integrated in-plane switching

• US 20080309627A1
• Filed: 06/13/2007
• Published: 12/18/2008
• Est. Priority Date: 06/13/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Zhong, John Z., Hotelling, Steve Porter
• Granted Patent: US 8,040,326 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
• 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 2203/04112 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 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/04184 Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes

Abstract

This relates to adding multi-touch functionality to a display without the need of a separate multi-touch panel or layer overlaying the display. Instead, embodiments of the invention can advantageously utilize existing display circuitry to provide multi-touch functionality while adding relatively little circuitry that is specific to the multi-touch functionality. Thus, by sharing circuitry for the display and the multi-touch functionalities, embodiments of the invention can be implemented at a lower cost than the alternative of superimposing additional multi-touch related layers onto an existing display panel. Furthermore, since the display and multi-touch functionality can be implemented on the same circuit, they can be synchronized so that noise resulting from the display functionality does not detrimentally affect the multi-touch functionality and vice versa.

Claims

1. A method for providing multi-touch functionality for a display having a plurality of cells, each cell comprising two electrodes, the method comprising:

creating a plurality of different voltage differentials between the two electrodes of one or more excited cells of the plurality of cells in order to cause an image to appear at the display;

discharging the voltage differentials between the two electrodes of one or more touch enabled cells of the one or more excited cells; and

sensing a plurality of mutual capacitances between cells of the one or more touch enabled cells in order to sense touch events at the display.

2. The method of claim 1, wherein sensing of the plurality of mutual capacitances includes sensing changes of the mutual capacitance.

3. The method of claim 1, wherein the sensing of the plurality of mutual capacitances includes:

defining one or more stimulus regions of the display, each stimulus region including one or more adjacent cells;

defining one or more sensor regions of the display, each sensor region including one or more adjacent cells;

stimulating each stimulus region with a stimulation signal.

4. The method of claim 3, wherein the sensing the plurality of mutual capacitances further includes:

sensing the amount of charge collected at one or more of the respective sensor regions as a result of the capacitive coupling of said sensor regions with adjacent stimulus regions and the stimulation of the adjacent stimulus regions.

5. The method of claim 4, wherein:

the sensing the amount of charge collected at one or more of the sensor regions further includes connecting the two electrodes of cells of the one or more sensor regions to one or more charge amplifiers; and

stimulating each stimulus region with a stimulation signal further includes stimulating the two electrodes of each cell within each stimulus region with the stimulation signal.

6. The method of claim 5, wherein each cell is connected to a color data line and a counter data line, the color data line, the color data line being connected to a first electrode and the counter data line being connected to a second electrode of the cell'"'"'s electrodes and wherein:

creating the voltage differentials between pairs of electrodes further includes connecting the counter data line connected to a cell to ground and applying a voltage to the color data line connected to the cell.

7. The method of claim 6, wherein stimulating each stimulus region with a stimulation signal further includes sending a stimulation signal to the counter and color data lines of one or more cells within the stimulus regions.

8. The method of claim 6, wherein sensing the amount of charge collected at one or more of the respective sensor regions further includes connecting the counter and color data lines of one or more cells within the one or more of the sensor regions to a charge amplifier.

9. The method of claim 6, wherein each data line is connected to a respective electrode through a transistor, each transistor being also connected to a select line.

10. The method of claim 6, wherein each data line is connected to the electrodes of a plurality of cells.

11. The method of claim 5, further including dynamically changing one or more of the stimulus and the sensor regions by dynamically changing the state of one or more cells vis-à

-vis the regions said cells belong to.

12. The method of claim 5, further including defining one or more guard regions, each guard region being placed between adjacent stimulus and sensor regions.

13. The method of claim 12, further including connecting both electrodes of each cell belonging to a guard region to ground during a touch sensing period.

14. The method of claim 13, further including dynamically changing one or more of the stimulus, sensor and guard regions by dynamically changing the state of one or more cells vis-à

-vis the regions said cells belong to.

15. A multi-touch display system, comprising:

a display containing a plurality of cells, each cell having two electrodes;

a plurality of color data lines, a first electrode of each cell being connected to at least one color data line;

a plurality of counter data lines, a second electrode of each cell being connected to at least one counter data line; and

a plurality switching elements associated with respective counter and color data lines and configured to selectively connect one or more of the plurality of counter and color data lines to ground or to a connection different than ground.

16. The multi-touch display system of claim 15, further comprising a plurality of transistors, wherein the pluralities of counter and color data lines are connected to respective electrodes through respective transistors.

17. The multi-touch display system of claim 15, wherein the switching elements are further configured to selectively connect the one or more of the plurality of counter and color data lines to a driver circuit configured to produce a stimulation signal.

18. The multi-touch display system of claim 16, wherein the switching elements are further configured to selectively connect the one or more of the plurality of counter and color data lines to one or more charge amplifier circuits configured to sense the charge present the electrodes of the cells connected to the charge amplifier circuits through the counter and color data lines.

19. The multi-touch display system of claim 18, further comprising a control circuit connected to the plurality of switching elements and configured to:

during a display update mode of operation, cause the plurality of switching elements to connect one or more of the plurality of counter data lines to ground and to connect one or more of the plurality of color data lines to a display data generation circuit;

during a touch sense mode of operation,

cause the plurality of switching elements to connect to one or more of the plurality of color data lines and counter data lines to ground in order to discharge one or more cells;

for a touch stimulus group of cells, cause switching elements associated with cells of said touch stimulus group of cells to connect counter and color data lines associated with cells of said touch stimulus group of cells to the driver circuit; and

for a charge sensor group of cells, cause switching elements associated with cells of said charge sensor group of cells to connect counter and color data lines associated with cells of said touch stimulus group of cells to the one or more charge amplifier circuits.

20. The multi-touch display system of claim 19, wherein the touch stimulus group of cells comprises a plurality of touch stimulus regions, and the charge sensor group of cells comprises a plurality of charge sensor regions, the charge sensor regions being positioned in proximity to touch stimulus regions.

21. The multi-touch display system of claim 20, wherein the control circuit is further configured to, for a guard group of cells, connect cause switching elements associated with cells of said guard group of cells to connect counter and color data lines associated with cells of said guard group of cells to the driver circuit.

22. The multi-touch display system of claim 21, wherein the guard group of cells comprises a plurality of guard regions, each guard region being positioned between an adjacent touch stimulus region and an adjacent charge sensor region.

23. The multi-touch display system of claim 19, further including a plurality of scan lines intersecting the counter and color data lines, each cell being associated with intersections of a scan line with a color data line and a counter data line, wherein a switch is associated with a cell if a counter data line or a color data line connected to the switch is connected to the cell and a select line intersecting said color or data line at said cell is excited.

24. A multi-touch enabled device comprising the multi-touch display system of claim 15.

25. A multi-touch enabled mobile phone comprising the multi-touch display system of claim 15.

26. A multi-touch enabled audio player comprising the multi-touch display system of claim 15.

27. A method for providing multi touch functionality for a device comprising the steps of:

dividing the cells of a display into plurality of regions;

dividing the regions into first and second type regions;

driving cells of the display with display data signals during a display update period;

driving the regions of a first type with a stimulus signal;

connecting the regions of the second type to a sensing circuit during a touch sense period; and

alternating the display update and touch sense periods.

28. A multi-touch enabled device comprising:

a display comprising a plurality of cells, the cells being grouped in a plurality of regions, the regions being of a first type or a second type;

a control circuit configured to,

drive cells of the display with display data signals during a display update period;

drive the regions of a first type with a stimulus signal;

connect the regions of the second type to a sensing circuit during a touch sense period; and

alternate the display update and touch sense periods.

29. A method for providing multi-touch functionality for a display, comprising a plurality of cells, each cell comprising two electrodes, the method comprising:

creating voltage differentials between the two electrodes of one or more excited cells of the plurality of cells in order to cause an image to appear at the display;

sensing a plurality of mutual capacitances between one or more touch enabled cells in order to sense touch events at the display, without substantially changing the voltage differentials of between the electrodes of said touch enabled cells.

30. The method of claim 29, further including the step of dividing the cells of the display into type A cells and type B cells and wherein the sensing of a plurality of mutual capacitances comprises:

during a first touch sense period,

exciting type A cells with a stimulus signal, wherein the two electrodes of each type A cell are excited with substantially the same stimulus signal, as to keep the voltage differential between the electrodes substantially the same, and

connecting type B cells to sensing circuits; and

during a second touch sense period,

exciting type B cells with a stimulus signal, wherein the two electrodes of each type B cell are excited with substantially the same stimulus signal, as to keep the voltage differential between the electrodes substantially the same, and

connecting type A cells to sensing circuits.

31. The method of claim 30 wherein the sensing circuits are charge amplifier circuits.

32. The method of claim 31 further comprising, during both touch sense periods, performing a gamma correction at the display to correct for artifacts caused by minor voltage differential changes appearing as a result of exciting type A or type B cells.

33. A multi-touch enabled display comprising:

a plurality of data lines;

a plurality of cells, each cell being connected to a data line and including a driven electrode connected to the data line and a counter electrode;

a plurality of first lines wherein a plurality of type A cells of the plurality of cells is such that the counter electrode of each type A cell is connected to a first line of the plurality of first lines; and

a plurality of second lines wherein a plurality of type B cells of the plurality of cells is such that the counter electrode of each type B cell is connected to a first line of the plurality of second lines.

34. The multi-touch enabled display of claim 33, further comprising control circuitry configured to:

drive the plurality of data lines with color data signals during a first period in order to create voltage differentials between the electrodes of one or more cells of the plurality of cells;

drive the plurality of first lines and one or more data lines connected to cells of type A with a stimulation signal during a second period, so that the stimulation signal does not significantly change the voltage differentials between the electrodes of the cells of type A;

connect the plurality of second lines and one or more data lines connected to cells of type B with one or more censor circuits during the second period;

drive the plurality of second lines and one or more data lines connected to cells of type B with a stimulation signal during a third period, so that the stimulation signal does not significantly change the voltage differentials between the electrodes of the cells of type B; and

connect the plurality of first lines and one or more data lines connected to cells of type a with one or more censor circuits during the third period.

35. The multi-touch enabled display of claim 34, wherein the sensor circuits are charge amplifier circuits.

36. The multi-touch enabled display of claim 34, wherein the control circuit is further configured to perform gamma correction during the second and third period in order to compensate for minor changes in the voltage differentials between the electrodes of the cells of type A during the second period and the cells of type B during the third period.

37. The multi touch enabled display of claim 34, wherein the plurality of first lines are substantially parallel common row lines and the plurality of second lines are substantially parallel common column lines which are substantially perpendicular to the common row lines.

38. A multi-touch enabled device comprising the multi-touch display of claim 33.

39. A multi-touch enabled mobile phone comprising the multi-touch display of claim 33.

40. A multi-touch enabled audio player comprising the multi-touch display of claim 33.

41. A mobile telephone including a multi-touch display system, the multi-touch display system comprising:

a display containing a plurality of cells, each cell having two electrodes;

a plurality of color data lines, a first electrode of each cell being connected to at least one color data line;

a plurality of counter data lines, a second electrode of each cell being connected to at least one counter data line; and

a plurality switching elements associated with respective counter and color data lines and configured to selectively connect one or more of the plurality of counter and color data lines to ground or to a connection different than ground.

42. An audio player including a multi-touch display system, the multi-touch display system comprising:

a display containing a plurality of cells, each cell having two electrodes;

a plurality of color data lines, a first electrode of each cell being connected to at least one color data line;

a plurality of counter data lines, a second electrode of each cell being connected to at least one counter data line; and

a plurality switching elements associated with respective counter and color data lines and configured to selectively connect one or more of the plurality of counter and color data lines to ground or to a connection different than ground.

43. A multi-touch enabled display comprising:

a plurality of display pixels, each display pixel comprising a display pixel circuit; and

a sensing circuit connected to the display pixel circuits and configured to sense changes in the mutual capacitance between two or more of the display pixel circuits.

44. A mobile telephone including a multi-touch enabled display comprising:

a plurality of display pixels, each display pixel comprising a display pixel circuit; and

a sensing circuit connected to the display pixel circuits and configured to sense changes in the mutual capacitance between two or more of the display pixel circuits.

45. An audio player including a multi-touch enabled display comprising:

a plurality of display pixels, each display pixel comprising a display pixel circuit; and

a sensing circuit connected to the display pixel circuits and configured to sense changes in the mutual capacitance between two or more of the display pixel circuits.

46. A method for sensing user input at a device comprising:

providing a display comprising a plurality of display pixels, each display pixel comprising a display pixel circuit; and

sensing changes in the mutual capacitance between two or more of the display pixel circuits,

wherein the changes of the mutual capacitance are indicative of touch events at the display.