Reducing bending effects in touch sensor devices

• US 9,134,396 B2
• Filed: 03/13/2013
• Issued: 09/15/2015
• Est. Priority Date: 04/17/2012
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Solven, Derek, Dattalo, Tracy Scott
• Primary Examiner(s): Phan, Huy Q
• Assistant Examiner(s): CLARKE, ADAM S
• Application Number:
  US13/798,936
• Publication Number:
  US 20130271160A1
• Time in Patent Office: 916 Days
• US Class Current: 1/1
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G01R 35/00 Testing or calibrating of apparatus covered by the other groups of this subclass
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• 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 3/0447 Position sensing using the local deformation of sensor cells

Abstract

A capacitive image sensor for detecting an input object includes a first substrate and a second substrate. A compressible region is defined between the first substrate and the second substrate. The first substrate is deflectable towards the second substrate. A transmitter electrode, receiver electrode, and bending effect electrode are disposed on the first substrate. The bending effect electrode is disposed between the transmitter electrode and receiver electrode and is configured to reduce a change in resulting signals detected from the receiver electrode caused by deflection of the first substrate towards the second substrate.

Claims

1. A capacitive image sensor for detecting an input object, comprising:

a first substrate having a first side;

a second substrate displaced from the first substrate to define a compressible region between the first substrate and the second substrate, wherein the first substrate is deflectable relative to the second substrate between a first position in which the compressible region has a first thickness and a second position in which the compressible region has a second thickness that is less than the first thickness;

a transmitter electrode disposed on the first substrate, the transmitter electrode configured to transmit a transmitter signal;

a receiver electrode disposed on the first substrate and configured to receive a resulting signal comprising effects corresponding to the transmitter signal; and

a bending effect electrode disposed on the first substrate and disposed between the transmitter electrode and the receiver electrode,

wherein when the first substrate is in the first position, a plurality of field lines associated with the resulting signal extends from the transmitter electrode through the compressible region and terminates on the bending effect electrode, and when the first substrate is in the second position, the plurality of field lines extends from the transmitter electrode through the compressible region and terminates on the second substrate.

2. The capacitive image sensor of claim 1, wherein the compressible region is an air gap.

3. The capacitive image sensor of claim 1, wherein the second substrate is a ground plane.

4. The capacitive image sensor of claim 1, wherein the second substrate is a surface of a display.

5. The capacitive image sensor of claim 1, wherein the second substrate is a common voltage electrode.

6. The capacitive image sensor of claim 1, wherein no shield layer is disposed between the second substrate and the transmitter electrode, the receiver electrode, and the bending effect electrode.

7. The capacitive image sensor of claim 1, wherein:

the transmitter electrode has a near edge and a far edge,

the bending effect electrode has a first edge disposed proximate to the near edge of the transmitter electrode and a second edge disposed proximate to the receiver electrode, and

the bending effect electrode is configured such that a distance between the far edge of the transmitter electrode and the second edge of the bending effect electrode is less than or equal to a distance from the transmitter electrode to a touch surface.

8. The capacitive image sensor of claim 1, wherein:

the transmitter electrode has a near edge and a far edge,

the bending effect electrode has a first edge disposed proximate to the near edge of the transmitter electrode and a second edge disposed proximate to the receiver electrode, and

the first thickness of the compressible region is less than or equal to a distance between the far edge of the transmitter electrode and the second edge of the bending effect electrode.

9. The capacitive image sensor of claim 1, wherein:

the transmitter electrode has a near edge and a far edge,

the bending effect electrode has a first edge disposed proximate to the near edge of the transmitter electrode, a second edge disposed proximate to the receiver electrode, and a width defined as a distance from the first edge to the second edge, and

the width of the bending effect electrode is at least 25 percent of a distance between the transmitter electrode and the receiver electrode.

10. The capacitive image sensor of claim 1, wherein a number of field lines in the compressible region that extend from the transmitter electrode to the receiver electrode is substantially constant when the first substrate is in the first position as compared to when the first substrate is in the second position.

11. An input device comprising:

a first substrate having a first side;

a second substrate displaced from the first substrate to define a compressible region between the first substrate and the second substrate, wherein the first substrate is deflectable between a first position in which the compressible region has a first thickness and a second position in which the compressible region has a second thickness that is less than the first thickness;

a plurality of sensing elements, each sensing element comprising a transmitter electrode disposed on the first substrate, a receiver electrode disposed on the first substrate and spaced apart from the transmitter electrode, and a bending effect electrode disposed on the first substrate and disposed between the transmitter electrode and the receiver electrode; and

a processing system communicatively coupled to the transmitter electrodes and to the receiver electrodes, and configured to drive the transmitter electrodes with transmitter signals for capacitive sensing and to receive resulting signals the receiver electrodes when the transmitter electrodes are driven for capacitive sensing, the resulting signals comprising effects corresponding to the transmitter signals,

wherein each bending effect electrode is configured such that when the first substrate is in the first position, a plurality of field lines associated with the resulting signals extends from the transmitter electrode through the compressible region and terminate on the bending effect electrode, and when the first substrate is in the second position, the plurality of field lines extends from the transmitter electrode through the compressible region and terminate on the second substrate.

12. The input device of claim 11, wherein for each sensing element, the transmitter electrode has a near edge and a far edge, the bending effect electrode has a first edge disposed proximate to the near edge of the transmitter electrode and a second edge disposed proximate to the receiver electrode, and the bending effect electrode is configured such that a distance between the far edge of the transmitter electrode and the second edge of the bending effect electrode is less than or equal to a distance from the transmitter electrode to a touch surface.

13. The input device of claim 11, wherein for each sensing element, the transmitter electrode has a near edge and a far edge, the bending effect electrode has a first edge disposed proximate to the near edge of the transmitter electrode and a second edge disposed proximate to the receiver electrode, and the first thickness of the compressible region is less than or equal to a distance between the far edge of the transmitter electrode and the second edge of the bending effect electrode.

14. The input device of claim 11, wherein for each sensing element, the transmitter electrode has a near edge and a far edge, the bending effect electrode has a first edge disposed proximate to the near edge of the transmitter electrode and a second edge disposed proximate to the receiver electrode, the bending effect electrode has a width that is equal to a distance from the first edge to the second edge, and the width of the bending effect electrode is at least 25 percent of a distance between the transmitter electrode and the receiver electrode.

15. The input device of claim 11, wherein for each sensing element, a number of field lines in the compressible region that extend from the transmitter electrode to the receiver electrode is substantially constant when the first substrate is in the first position as compared to when the first substrate is in the second position.

16. The input device of claim 11, wherein no shield layer is disposed between the second substrate and the transmitter electrodes, the receiver electrodes, and the bending effect electrodes.

17. The input device of claim 11, wherein the processing system is configured to drive the bending effect electrode at a ground voltage while receiving a resulting signal with the receiver electrode.

18. The input device of claim 11, wherein the processing system is configured to drive the bending effect electrode is at a reference voltage while receiving a resulting signal with the receiver electrode.

19. The input device of claim 11, wherein the processing system is configured to drive the bending effect electrode with a varying voltage while receiving a resulting signal with the receiver electrode.

20. The input device of claim 11, wherein the compressible region is an air gap.

21. A capacitive image sensor for detecting an input object, comprising:

a first substrate having a first side;

a second substrate displaced from the first substrate to define a compressible region between the first substrate and the second substrate, wherein the first substrate is deflectable relative to the second substrate between a first position in which the compressible region has a first thickness and a second position in which the compressible region has a second thickness that is less than the first thickness;

a transmitter electrode disposed on the first substrate, the transmitter electrode configured to transmit a transmitter signal;

a receiver electrode disposed on the first substrate and configured to receive a resulting signal comprising effects corresponding to the transmitter signal; and

a bending effect electrode disposed on the first substrate and disposed between the transmitter electrode and the receiver electrode,

wherein the bending effect electrode is configured to reduce an amount of change in capacitive coupling associated with the resulting signal between the transmitter electrode and the receiver electrode that occurs when the first substrate is deflected from the first position to the second position.

22. The capacitive image sensor of claim 21, wherein:

the transmitter electrode has a near edge and a far edge,

the bending effect electrode has a first edge disposed proximate to the near edge of the transmitter electrode and a second edge disposed proximate to the receiver electrode, and

the bending effect electrode is configured such that a distance between the far edge of the transmitter electrode and the second edge of the bending effect electrode is less than or equal to a distance from the transmitter electrode to a touch surface.

23. The capacitive image sensor of claim 21, wherein:

the transmitter electrode has a near edge and a far edge,

the bending effect electrode has a first edge disposed proximate to the near edge of the transmitter electrode and a second edge disposed proximate to the receiver electrode, and

the first thickness of the compressible region is less than or equal to a distance between the far edge of the transmitter electrode and the second edge of the bending effect electrode.

24. The capacitive image sensor of claim 21, wherein:

the transmitter electrode has a near edge and a far edge,

the bending effect electrode has a first edge disposed proximate to the near edge of the transmitter electrode, a second edge disposed proximate to the receiver electrode, and a width defined as a distance from the first edge to the second edge, and the width of the bending effect electrode is at least 25 percent of a distance between the transmitter electrode and the receiver electrode.