INTEGRATED IN-PLANE SWITCHING

• US 20120026132A1
• Filed: 10/07/2011
• Published: 02/02/2012
• Est. Priority Date: 06/13/2007
• Status: Active Grant

• Current Assignee: John Z. Zhong, Steve Porter Hotelling
• Original Assignee: John Z. Zhong, Steve Porter Hotelling
• Inventors: Hotelling, Steve Porter, Zhong, John Z.
• Granted Patent: US 8,274,492 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• 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, 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 between the electrodes of said touch enabled cells.

2. The method of claim 1, 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.

3. The method of claim 2 wherein the sensing circuits comprise charge amplifier circuits.

4. The method of claim 3 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.

5. A multi-touch enabled display comprising:

a plurality of data lines;

a plurality of cells, each cell including a driven electrode and a counter electrode, the driven electrodes of the plurality of cells being connected to the plurality of data lines during a first time period;

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;

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; and

control circuitry configured to;

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

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

connect the plurality of second lines connected to the type B cells with one or more sensor circuits during the second time period;

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

connect the plurality of first lines connected to the type A cells with one or more sensor circuits during the third time period.

6. The multi-touch enabled display of claim 5, wherein the sensor circuits comprise charge amplifier circuits.

7. The multi-touch enabled display of claim 5, wherein the control circuit is further configured to perform gamma correction during the second and third time periods in order to compensate for minor changes in the voltage differentials between the electrodes of the type A cells during the second time period and the type B cells during the third time period.

8. The multi touch enabled display of claim 5, wherein the plurality of first lines are substantially parallel common column lines and the plurality of second lines are substantially parallel common row lines which are substantially perpendicular to the common column lines.

9. A multi-touch enabled device comprising the multi-touch display of claim 5.

10. A multi-touch enabled mobile phone comprising the multi-touch display of claim 5.

11. A multi-touch enabled audio player comprising the multi-touch display of claim 5.

12. The multi-touch enabled display of claim 5 further comprising:

a plurality of switches for connecting the plurality of driven electrodes of the plurality of cells to the plurality of data lines during the first time period.

13. The multi-touch enabled display of claim 12 wherein the control circuitry is operative to:

actuate the plurality of switches to connect data lines in sequence to groups of the driven electrodes of the plurality of cells disposed along a given direction.

14. The multi-touch enabled display of claim 13 wherein the control circuitry is operative to

actuate the plurality of switches to disconnect the data lines from the driven electrodes of the plurality of cells during the second and third time periods.

15. The multi-touch enabled display of claim 5 wherein the plurality of cells each comprise a storage capacitor and the control circuitry is operative to disconnect the driven electrodes of the plurality of cells from the plurality of data lines during the second and third time periods.

16. The multi-touch enabled display of claim 15 wherein the storage capacitor is disposed between each of the plurality of driven and counter electrodes, and a common mode voltage is established between the driven and counter electrodes of the type A and type B cells when the driven electrodes are driven during the second and third time periods respectively.

17. The multi-touch enabled display of claim 5, wherein the control circuitry is configured to ground the data lines during the second and third time periods.

18. The multi-touch enabled display of claim 12, wherein the control circuitry is configured to ground the data lines during the second and third time periods.

19. The multi-touch enabled display of claim 5 wherein the driven and counter electrodes of each of the plurality of cells are disposed in an in-plane switching arrangement.

20. The multi-touch enabled display of claim 19, wherein the driven and counter electrodes of each of the plurality of cells are disposed in an interdigitated comb-shaped arrangement.

21. A method of operating a display for displaying data and providing touch sensing, the display having a plurality of cells, each cell having a driven electrode and a counter electrode, some of the plurality of cells comprising type A cells having their counter electrodes connected to ones of a first plurality of lines and others of the plurality of cells comprising type B cells having their counter electrodes connected to ones of a second plurality of lines, the method comprising:

connecting a plurality of data lines to the driven electrode of the plurality of cells during a first time period to thereby display data on the display;

driving the plurality of data lines with data signals during the first time period in order to create voltage differentials between the driven and counter electrodes of one or more cells of the plurality of cells;

driving the plurality of first lines connected to the type A cells with a stimulation signal during a second time period, such that the stimulation signal does not significantly change the voltage differentials between the electrodes of the type A cells;

connecting the plurality of second lines connected to the type B cells with one or more sensor circuits during the second time period;

driving the plurality of second lines connected to the type B cells with a stimulation signal during a third time period, such that the stimulation signal does not significantly change the voltage differentials between the electrodes of the type B cells; and

connecting the plurality of first lines connected to the type A cells with one or more sensor circuits during the third time period.

22. The method of claim 21, further comprising grounding the data lines during the second and third time periods.

23. The method of claim 21, further comprising disconnecting the data lines from the driven electrodes of the plurality of cells during the second and third time periods.

24. The method of claim 23, further comprising grounding the data lines during the second and third time periods.

25. A touch screen comprising an in-plane-switching (IPS) liquid crystal display with integral touch sensing, the touch screen comprising:

a pair of electrodes for each of a plurality of display pixels, the pair of electrodes disposed in an in-plane-switching arrangement;

a driven electrode being one of the pair of electrodes;

a counter electrode being the other of the pair of electrodes;

a plurality of data lines for transmitting display data to the driven electrodes of the plurality of display pixels; and

a plurality of switches, operative in a display mode of operation, for connecting the data lines to the driven electrodes of the plurality of display pixels;

a first plurality of display pixels having common terminals electrically connected together to form a plurality of touch sense rows, the common terminal of each of the first plurality of display pixels being electrically connected to the counter electrode;

a second plurality of display pixels having common terminals electrically connected together to form a plurality of touch sense columns, the common terminals of each of the second plurality of display pixel being electrically connected to the counter electrode; and

during a touch sensing mode of operation,

a stimulation signal is alternately applied to the plurality of touch sensing rows and the plurality of touch sensing columns;

a capacitance sensing circuitry is alternately coupled to the plurality of touch sensing columns and the plurality of touch sensing rows; and

the plurality of switches operative to disconnect the data lines from the driven electrodes.

26. The touch screen of claim 25, wherein the data lines are held at a constant potential during the touch sensing mode of operation.

27. A touch screen comprising an in-plane-switching liquid crystal display with integral touch sensing, the touch screen having a plurality of touch pixels responsive to a touch or near touch of the touch screen wherein the touch screen comprises:

a plurality of display pixels each having first and second electrodes disposed adjacent one another in an in-plane switching arrangement;

a select terminal, a data terminal and a common terminal, the display pixels used during a display mode of operation;

type A pixels, each having first and second electrodes disposed adjacent one another in an in-plane switching arrangement;

a select terminal, a data terminal and a common terminal with common terminals of adjacent type A pixels electrically connected together to form touch sensing columns, the type A pixels used at least during a touch sensing mode of operation;

type B pixels each having first and second electrodes disposed adjacent one another in an in-plane switching arrangement;

a select terminal, a data terminal and a common terminal with common terminals of adjacent type B pixels electrically connected together to form touch sensing row, the type B pixels used at least during a touch sensing mode of operation s;

a first column group formed by type A pixels and display pixels disposed in one or more columns, wherein a ratio of display pixels to type A pixels is X;

1, where X is an integer greater than 1;

a second column group formed by type B pixels and display pixels disposed in one or more columns, wherein a ratio of display pixels to type B pixels is X;

1, where X is an integer greater than 1 the second column group disposed adjacent the first column group;

wherein during a touch sense mode of operation,

a stimulation signal is alternately applied to the plurality of touch sensing rows and the plurality of touch sensing columns; and

a capacitance sensing circuitry alternately coupled to the plurality of touch sensing columns and the plurality of touch sensing rows.

28. A touch screen comprising a liquid crystal display with integral touch sensing, the touch screen having a plurality of touch pixels responsive to a touch or near touch of the touch screen wherein the touch screen comprises:

type A pixels, each having first and second electrodes disposed adjacent one another in an in-plane switching arrangement;

a select terminal, a data terminal and a common terminal with common terminals of adjacent type A pixels electrically connected together to form touch sensing columns;

type B pixels each having first and second electrodes disposed adjacent one another in an in-plane switching arrangement;

a select terminal, a data terminal and a common terminal with common terminals of adjacent type B pixels electrically connected together to form touch sensing rows;

a plurality of switches operative in a display mode to connect the data terminals of the type A and type B pixels to data lines;

a first group of type A pixels disposed in one or more columns;

a first group of type B pixels disposed in one or more columns, adjacent the first group of type A pixels;

a second group of type A pixels disposed in one or more columns adjacent the first group of type B pixels;

a second group of type B pixels disposed in one or more columns adjacent the second group of type A pixels; and

wherein the first group of type A pixels, the adjacent first group of type B pixels, the adjacent second group of type A pixels and the adjacent second group of type B pixels form alternating type A and type B pixels columns; and

the plurality of switches operative in a touch sensing mode to disconnect the data terminals of the type A and type B pixels from the data lines.

29. The touch screen as recited in claim 28 wherein the common terminals of the type B pixels are connected together with a common row line, and the common row line interconnects the first and second groups of type B pixels while electrically bypassing the type A pixels.

30. The touch screen as recited in claim 29 further comprising:

during a touch sensing function, the second electrodes of the type A pixels alternately connected to an alternating voltage touch stimulation signal and a capacitance measurement circuit, and the second electrode of the type B pixels alternatively connected to the capacitance measurement circuit and the alternating voltage touch stimulation signal;

wherein the capacitance measurement circuit enables capacitance measurements which change when a touch object approaches the first and second electrodes.

31. The touch screen as recited in claim 30 wherein the common terminals of the type B pixels are connected together with a common row line, and the common row line interconnects the first and second groups of type B pixels while electrically bypassing the type A pixels.