Split sense lines for negative pixel compensation

• US 9,081,442 B2
• Filed: 02/27/2012
• Issued: 07/14/2015
• Est. Priority Date: 02/27/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Yousefpor, Marduke, Grunthaner, Martin Paul
• Primary Examiner(s): Mengistu, Amare
• Assistant Examiner(s): STEPP JONES, SHAWNA T
• Application Number:
  US13/406,338
• Publication Number:
  US 20130222324A1
• Time in Patent Office: 1,233 Days
• Field of Search: 345/173
• US Class Current: 1/1
• 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 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/044 by capacitive means
• 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 configured to compensate for negative pixel effect is disclosed. The panel can be configured to increase a capacitive sense signal, indicative of a touching or hovering object, in order to compensate for an increase in negative capacitance when the object is poorly grounded. To perform the compensation, the panel can be configured to have split sense lines so as to increase the number of electric fringe fields forming the sense signal, thereby providing a sense signal that is substantially stronger than the negative capacitance signal. Each sense line can be split into two or more strips.

Claims

1. A touch panel comprising:

a sense line split into multiple strips, the strips configured to form a first capacitance indicative of a proximity of an object to the panel and a second capacitance indicative of a grounding condition of the object, the first capacitance being substantially larger than the second capacitance so as to compensate for negative pixel effect at the panel, wherein the strips of the sense line are directly coupled together at distal ends.

2. The panel of claim 1, wherein the sense line is split lengthwise into the strips.

3. The panel of claim 1, wherein the number of strips is at least two.

4. The panel of claim 1, wherein the strips have substantially the same width.

5. The panel of claim 1, wherein the strips are configured to form the first capacitance with a drive line for driving the panel and the strips are configured to form the second capacitance with the drive line and the object.

6. The panel of claim 1 incorporated into at least one of a mobile telephone, a digital media player, or a portable computer.

7. A touch panel comprising:

a sense line split into multiple strips, the strips configured to form a first capacitance indicative of a proximity of an object to the panel and a second capacitance indicative of a grounding condition of the object, the first capacitance being substantially larger than the second capacitance so as to compensate for negative pixel effect at the panel, wherein the strips of the sense line are directly coupled at one distal end and separate at the other distal end, the panel comprising a multiplexor directly coupled to the strips at the other distal end and configured to select between the strips to output a signal therefrom.

8. A touch panel comprising:

a sense line split into multiple strips, the strips configured to form a first capacitance indicative of a proximity of an object to the panel and a second capacitance indicative of a grounding condition of the object, the first capacitance being substantially larger than the second capacitance so as to compensate for negative pixel effect at the panel, wherein the multiplicity of the strips causes the first capacitance to have an increased value so as to compensate for the negative pixel effect, wherein the strips of the sense line are directly coupled together at distal ends.

9. A touch panel comprising:

a drive line configured to drive the touch panel to sense a proximate object; and

a sense line divided lengthwise into multiple strips directly coupled at a distal end, the multiple strips configured to sense the proximate object, wherein the drive line and the strips form a capacitance for compensating for negative pixel effect at the panel.

10. The panel of claim 9, wherein the drive line and the strips form electric fringe fields, the number of fields related to the number of strips.

11. The panel of claim 10, wherein the fringe fields are configured to be interfered with by the proximate object, the amount of interference corresponding to the capacitance.

12. The panel of claim 9, wherein a second capacitance forms between the drive line, the strips, and the proximate object to create the negative pixel effect.

13. A touch sensitive device comprising:

a cover having a touchable surface; and

a touch panel proximate to a surface of the cover opposite the touchable surface, the touch panel including

multiple drive lines configured to drive the panel to detect an object proximate to the touchable surface, and

multiple sense lines configured to sense the proximate object, each sense line divided into multiple strips to form multiple capacitances for compensating for negative pixel effect at the panel,

wherein strength of the negative pixel effect is a function of thinness of the cover.

14. The device of claim 13, wherein the multiple capacitances are mutual capacitances.

15. The device of claim 13, wherein the multiple capacitances form between the drive lines and the strips, indicative of a proximity of the object, wherein second capacitances form between the drive lines, the strips, and the proximate object, indicative of the negative pixel effect, and wherein the multiple capacitances are substantially larger than the second capacitances so as to compensate for the negative pixel effect at the panel.

16. A method to reduce negative pixel effect in a touch panel, comprising:

forming a first capacitive path between a drive line of the panel and a sense line of the panel, the sense line split into multiple strips;

forming a second capacitive path between the drive line, the strips of the sense line, and the proximate object;

providing a first capacitance, indicative of a proximity of the object, along the first capacitive path and a second capacitance, indicative of a grounding condition of the object, along the second capacitive path, and

maintaining a ratio between the first and second capacitances in which the first capacitance is substantially larger than the second capacitance, regardless of a proximity of the object to the panel,

wherein the first capacitance is substantially larger than the second capacitance so as to compensate for negative pixel effect at the panel caused by the grounding condition.

17. The method of claim 16, wherein forming the first capacitive path comprises capacitively coupling the drive line and the sense line together to create the first capacitance.

18. The method of claim 16, wherein forming the second capacitive path comprises:

forming a third capacitive path capacitively coupling the drive line and the proximate object;

forming a fourth capacitive path capacitively coupling the strips and the proximate object; and

coupling the third and fourth capacitive paths together to form the second capacitive path for the second capacitance.

19. The method of claim 16, wherein maintaining the ratio comprises dynamically increasing the first capacitance in conjunction with the second capacitance as the proximate object approaches the panel so as to maintain the ratio at a predetermined level to compensate for the negative pixel effect.

20. The method of claim 16, wherein the negative pixel effect is a function of the grounding condition indicated by the second capacitance and wherein the negative pixel effect is compensated for by reducing the effect of the second capacitance at the panel.