Mechanical deflection compensation for orthogonal electrodes
A location of contact with a touch sensitive device is determined. Output signals associated with a plurality of electrodes such as formed on a single layer of the touch sensitive device are measured to identify a first electrode positioned at an approximate location of contact with the touch sensor. An output signal associated with a different electrode that is separated from the first electrode is measured to determine an undesired signal amount, such as due to deflection. An undesired single amount associated with the first electrode may be estimated based on the undesired signal amount measured at the other electrode. The signal amount measured at the first electrode is then compensated by the estimated undesired signal amount. The location of contact with the touch sensor is then determined based on the compensated signal amount.
1. A method for determining a location of contact on a touch sensitive device, the method comprising:
measuring contact capacitances of a plurality of electrodes in a vicinity of a contact on the touch sensitive device, wherein the touch sensitive device comprises a first electrode layer orthogonal to a second electrode layer;
determining a mechanical deflection capacitance of a remote electrode positioned a distance away from an electrode of the plurality of electrodes, wherein the remote electrode and the plurality of electrodes correspond to the first electrode layer;
determining a plurality of mechanical deflection capacitances of the plurality of electrodes based at least on the mechanical deflection capacitance;
adjusting the contact capacitances based at least on the plurality of mechanical deflection capacitances; and
determining the location of the contact based on the adjustment.
2. The method according to claim 1 , wherein the contact capacitances exceed a threshold value.
3. The method according to claim 1 , wherein the mechanical deflection capacitance is based on the following:
Δ
C
i
=
1
N
[
(
N
-
i
)
m
o
+
i
m
N
]
where ΔC i is a capacitance associated with mechanical deflection of an i th electrode, N+1 is a number of electrodes of the first electrode layer, i=0, . . . , N, and m o and M N correspond to capacitance measurements of a first and an Nth electrode, respectively.
4. The method according to claim 3 , wherein the first and Nth electrodes are not in the vicinity of the contact.
5. The method according to claim 1 , wherein the mechanical deflection capacitance is determined as follows:
Δ
C
i
=
4
S
x
(
2
i
+
1
)
(
2
N
-
2
i
-
1
)
(
2
N
)
2
where ΔC i is a capacitance associated with mechanical deflection of an i th electrode, N is a number of electrodes, i=0, . . . , N−1, and where a value of S x is determined from a measurement of ΔC i for at least one electrode remote from the location of the contact.
6. The method according to claim 1 , wherein the touch sensitive device comprises a transparent surface and the plurality of electrodes are arranged on the transparent surface, wherein the transparent surface is positioned over a display surface.
7. The method according to claim 1 , wherein the plurality of electrodes terminate along a peripheral edge of the touch sensitive device.
8. A system for determining a location of contact on a touch sensitive device, the system comprising:
one or more analog-to-digital converters configured to measure output signals associated with a first electrode layer, wherein the first electrode layer is orthogonal to a second electrode layer of the touch sensitive device; and
a processor configured to:
measure contact capacitances of a plurality of electrodes in a vicinity of a contact on the touch sensitive device, wherein the touch sensitive device comprises the first electrode layer orthogonal to the second electrode layer;
determine a mechanical deflection capacitance of a remote electrode positioned a distance away from an electrode of the plurality of electrodes, wherein the remote electrode and the plurality of electrodes correspond to the first electrode layer;
determine mechanical deflection capacitance components of the plurality of electrodes based at least on the mechanical deflection capacitance;
adjust the contact capacitances based at least on the mechanical deflection capacitance components; and
determine the location of the contact based on the adjustment.
9. The system according to claim 8 , wherein the contact capacitances exceed a threshold value.
10. The system according to claim 9 , wherein the mechanical deflection capacitance is determined as follows:
Δ
C
i
=
1
N
[
(
N
-
i
)
m
o
+
i
m
N
]
where ΔC i is a capacitance associated with mechanical deflection of an i th electrode, N+1 is a number of electrodes of the first electrode layer, i=0, . . . , N, and m o and M N correspond to capacitance measurements of a first and an Nth electrode, respectively.
11. The system according to claim 10 , wherein the first and Nth electrodes are not in the vicinity of the contact.
12. The system according to claim 10 , wherein the first electrode is the remote electrode.
13. The system according to claim 8 , wherein the mechanical deflection capacitance is determined as follows:
Δ
C
i
=
4
S
x
(
2
i
+
1
)
(
2
N
-
2
i
-
1
)
(
2
N
)
2
where ΔC i is the capacitance associated with mechanical deflection of an i th electrode, N is a number of electrodes, i=0, . . . , N−1, and where a value of S x is determined from a measurement of ΔC i for at least one electrode remote from the location of the contact.
14. The system according to claim 8 , wherein the touch sensitive device comprises a transparent surface and the plurality of electrodes are arranged on the transparent surface, wherein the transparent surface is positioned over a display surface.
15. The system according to claim 8 , wherein the plurality of electrodes terminate along a peripheral edge of the touch sensitive device.
16. The system according to claim 8 , where the distance corresponds to a distance between two or more electrodes.
17. A non-transitory computer readable storage medium storing instructions that, when executed by a processor of a touch sensitive device, cause the touch sensitive device to perform operations comprising:
measuring contact capacitances of a plurality of electrodes in a vicinity of a contact on the touch sensitive device, wherein the touch sensitive device comprises a first electrode layer orthogonal to a second electrode layer;
determining a mechanical deflection capacitance of a remote electrode positioned a distance away from an electrode of the plurality of electrodes, wherein the remote electrode and the plurality of electrodes correspond to the first electrode layer;
determining a plurality of mechanical deflection capacitances of the plurality of electrodes based at least on the mechanical deflection capacitance;
adjusting the contact capacitances based at least on the plurality of mechanical deflection capacitances; and
determining the location of the contact based on the adjustment.
18. The non-transitory computer readable storage medium of claim 17 , wherein a capacitance associated with a mechanical deflection of the touch sensitive device is determined as follows:
Δ
C
i
=
1
N
[
(
N
-
i
)
m
o
+
i
m
N
]
where ΔC i is the capacitance associated with mechanical deflection of an i th electrode, N+1 is a number of electrodes, i=0, . . . , N, and m o and M N correspond to capacitance measurements of a first and an Nth electrode, respectively.
19. The non-transitory computer readable storage medium according to claim 18 , wherein the first and Nth electrodes are not in the vicinity of the contact.
20. The non-transitory computer readable storage medium of claim 17 , wherein the touch sensitive device comprises a transparent surface and the plurality of electrodes are arranged on the transparent surface, wherein the touch sensitive device surface is positioned over a display surface, and the location of the contact corresponds to a location associated with a touch on the touch sensitive device.