US-20260126876-A1 - TOUCH-SENSITIVE APPARATUS AND METHOD

US20260126876A1US 20260126876 A1US20260126876 A1US 20260126876A1US-20260126876-A1

Abstract

Disclosed is a touch-sensitive apparatus, the apparatus including an electrode array, comprising at least a drive electrode; drive circuitry configured to generate one or more drive signals comprising at least a first drive signal for driving the at least a drive electrode; and control circuitry. The control circuitry is configured to: identify a set of N drive electrodes comprising the at least a drive electrode; apply the one or more drive signals to the set of N drive electrodes, wherein the control circuitry is configured to apply the one or more drive signals in a plurality of discrete time periods; obtain a measurement from the electrode array in each of the plurality of discrete time periods; determine an indication of a capacitive coupling associated with the at least a drive electrode; and determine an indication of the noise for the set of N drive electrodes.

Inventors

Stephen William Roberts

Assignees

TOUCHNETIX LIMITED

Dates

Publication Date: 20260507
Application Date: 20231017
Priority Date: 20221019

Claims (20)

1 . A touch-sensitive apparatus, the apparatus comprising: an electrode array, comprising at least a drive electrode; drive circuitry configured to generate one or more drive signals comprising at least a first drive signal for driving the at least a drive electrode; control circuitry configured to: identify a set of N drive electrodes comprising the at least a drive electrode, where N is an integer greater than or equal to one; apply the one or more drive signals to the set of N drive electrodes, wherein the control circuitry is configured to apply the one or more drive signals in a plurality of discrete time periods, wherein the number of electrodes in the set of N drive electrodes is less than the number of discrete time periods; obtain a measurement from the electrode array in each of the plurality of discrete time periods; determine an indication of a capacitive coupling associated with the at least a drive electrode based on the obtained measurements from the electrode array in each of the plurality of discrete time periods; and determine an indication of the noise for the set of N drive electrodes based on the obtained measurements from the electrode array in each of the plurality of discrete time periods.
2 . The touch-sensitive apparatus of claim 1 , wherein: the electrode array additionally comprises at least one receive electrode; the one or more drive signals comprises at least a first drive signal and a second drive signal; the control circuitry is configured to: apply the one or more drive signals to the set of N drive electrodes in a plurality of discrete time periods, wherein in at least two of the discrete time periods, the control circuitry is configured to apply a different one of the first drive signal and the second drive signal to the at least a drive electrode of the set of drive electrodes; obtain a measurement from the receive electrode of the electrode array in each of the plurality of discrete time periods; determine, as an indication of a capacitive coupling associated with the at least a drive electrode, a mutual capacitive coupling between each of the set of N drive electrodes and the receive electrode based on the obtained measurements from the receive electrode of the electrode array in each of the plurality of discrete time periods; and determine an indication of the noise for the set of N drive electrodes based on the obtained measurements from the receive electrode of the electrode array in each of the plurality of discrete time periods.
3 . The touch-sensitive apparatus of claim 2 , wherein the control circuitry is configured to: apply one of the first and second drive signals to the at least a first drive electrode during a first discrete time period; obtain a first measurement from the receive electrode during the first discrete time period; apply the other of the first and second drive signals to the at least a first drive electrode during a second discrete time period; obtain a second measurement from the receive electrode during the second discrete time period; determine an indication of the mutual capacitive coupling between the at least a drive electrode and the receive electrode based at least on the obtained first and second measurements from the receive electrode; and determine the indication of the noise for the set of N drive electrodes based at least on the obtained first and second measurements.
4 . The touch-sensitive apparatus of claim 1 , wherein: the control circuitry is configured to: obtain a measurement from at least drive electrode of the electrode array in each of the plurality of discrete time periods; determine, as an indication of a capacitive coupling associated with the at least a drive electrode, a self-capacitive coupling of the at least drive electrode based on the obtained measurements from the at least drive electrode of the electrode array in each of the plurality of discrete time periods; and determine an indication of the noise for the set of N drive electrodes based on the obtained measurements from the at least drive electrode of the electrode array in each of the plurality of discrete time periods.
5 . The touch-sensitive apparatus of claim 4 , wherein the control circuitry is configured to: apply a first drive signal to the at least a drive electrode during a first discrete time period; obtain a first measurement from the at least a drive electrode during the first discrete time period; apply the first drive signal to the at least a drive electrode during a second discrete time period; obtain a second measurement from the at least a drive electrode during the second discrete time period; determine an indication of the self-capacitive coupling of the at least a drive electrode based at least on the obtained first and second measurements from the receive electrode; and determine the indication of the noise for the set of N drive electrodes based at least on the obtained first and second measurements.
6 . The touch-sensitive apparatus of claim 1 , wherein determining the indication of the capacitive coupling associated with the at least a drive electrode includes combining each of the obtained measurements from each of the plurality of discrete time periods.
7 . The touch-sensitive apparatus of claim 1 , wherein determining the indication of the noise for the set of N drive electrodes based on the obtained measurements from the electrode array includes combining each of the obtained measurements from each of the plurality of discrete time periods.
8 . The touch-sensitive apparatus of claim 7 , wherein determining the indication of the capacitive coupling associated with the at least a drive electrode includes combining each of the obtained measurements from each of the plurality of discrete time periods, and wherein the combination of each of the obtained measurements from each of the plurality of discrete time periods for determining the indication of the noise for the set of N drive electrodes is different to the combination of each of the obtained measurements from each of the plurality of discrete time periods for determining the indication of the capacitive coupling associated with the at least drive electrode.
9 . The touch-sensitive apparatus of claim 1 , wherein, when the set of N drive electrodes comprises N number of drive electrodes, the control circuitry is configured to apply the drive signals over Y number of discrete time periods, wherein Y is greater than N.
10 . The touch-sensitive apparatus of claim 9 , wherein Y is selected from the sequence of: 2, 4, 8, 12, 16, 20, 24, 28, 32, etc.
11 . The touch-sensitive apparatus of claim 10 , wherein Y is the next largest value in the sequence from N.
12 . The touch-sensitive apparatus of claim 2 , wherein the control circuitry is configured to determine combinations of the first and second drive signals to be applied to the set of N drive electrodes, wherein each electrode of the set of N drive electrodes receives one of the first and second drive signals in a given discrete time period, and wherein each one of the determined combinations of the first drive signal and second drive signals is applied in a respective one of the plurality of discrete time periods.
13 . The touch-sensitive apparatus of claim 12 , wherein each combination of the first drive signal and second drive signal is different from one another.
14 . The touch-sensitive apparatus of claim 1 , wherein the set of electrodes comprises only one drive electrode.
15 . The touch-sensitive apparatus of claim 1 , wherein the control circuitry is configured to determine the presence of a touch on the touch-sensitive apparatus by comparing the determined indication of the capacitive coupling associated with the at least a drive electrode to a corresponding indication of the capacitive coupling associated with the at least a drive electrode obtained in advance.
16 . The touch-sensitive apparatus of claim 15 , wherein determining the presence of a touch on the touch-sensitive apparatus includes determining whether the indication of the capacitive coupling associated with the at least a drive electrode differs from the corresponding indication of the capacitive coupling associated with the at least a drive electrode obtained in advance by a threshold, wherein optionally, the threshold is determined based on the determined indication of the noise for the set of N drive electrodes.
17 . (canceled)
18 . The touch-sensitive apparatus of claim 1 , wherein the control circuitry is configured to disregard the obtained measurement from the electrode array in each of the plurality of discrete time periods if the determined indication of the noise for the set of N drive electrodes indicates the noise exceeds a predetermined upper threshold.
19 . A system comprising the touch-sensitive apparatus of claim 1 , further comprising system processing circuitry communicatively coupled to the processing circuitry of the touch-sensitive apparatus.
20 . The system of claim 19 , wherein the system processing circuitry is configured to cause the system to perform a first action in response to receiving a signal output from the processing circuitry of the touch-sensitive apparatus indicating the presence of a touch on the touch-sensitive element.

Description

BACKGROUND OF THE INVENTION The present invention relates to the field of touch sensors, for example touch sensors for overlying a display screen to provide a touch-sensitive display (touch screen). In particular, embodiments of the invention relate to techniques for measuring the mutual capacitance at a plurality of intersections between drive electrodes and receive electrodes for sensing the presence of one or more touching objects within a two-dimensional sensing area. A capacitive touch sensor can be generalised as one that uses a physical sensor element comprising an arrangement of electrically conductive electrodes extending over a touch sensitive area (sensing area) to define sensor nodes (or intersection points) and controller circuitry connected to the electrodes and operable to measure changes in the electrical capacitance of each of the electrodes or the mutual-capacitance between combinations of the electrodes. The electrodes are typically provided on a substrate. Some of these electrodes may be referred to as drive electrodes (which are driven with a suitable signal, such as a time-varying voltage signal) and some may be referred to as receive electrodes (which are coupled to receiver circuitry and generate a signal in response to a driven drive electrode coupling to the receiver electrode at the sensor node). For capacitive touch sensors in which the mutual capacitance is measured between combinations of electrodes, to perform a complete scan of the mutual capacitance over the touch sensitive surface, each sensor node or intersection point for the electrodes must be individually measured. This may be done by driving each drive electrode individually and sequentially with a suitable signal and measuring the signal generated in each receiver electrode that forms an intersection point with that drive electrode. The performance of touch sensors may be characterised in accordance with at least two characteristics; namely the sensitivity of the touch sensor (i.e., how easily the touch sensor can detect a touch) and the responsiveness of the touch sensor (i.e., how quickly the touch sensor can detect/register a touch on the sensing surface from the moment a touch is present). In mutual capacitance measurement techniques, the sensitivity is broadly proportional to the time taken to measure the mutual capacitance at each intersection point between combinations of electrodes (or more particularly, on the number of samples of the mutual capacitance for each intersection point that can be taken in that time period)—generally, the greater the measurement time period, the better the sensitivity. Conversely, the responsiveness is broadly proportional to the total time required to measure the mutual capacitance at all the intersection points of an electrode array-generally, the shorter the time period, the better the responsiveness. Most applications for touch sensors require both good sensitivity and good responsiveness, but as evident from above, a balance must be struck between the two parameters. One way to help improve the sensitivity and/or responsiveness is to employ faster electronics which can sample a signal (the mutual capacitance) at a higher sample rate. However, faster electronics are usually expensive and may be relatively large, and are thus are not practical for all commercial applications. Additionally, such capacitive touch sensors can be subject to noise (e.g., from sources external to the capacitive touch sensor). By measuring the capacitive coupling in the absence of any drive signal applied to the electrodes, an indication of the noise that the (or parts of the) electrode array is exposed to can be determined. This determined noise can subsequently be used to determine to what extent the capacitive coupling at a particular node/intersection point was influenced by noise, and thus the relative confidence in each of the measurements. Because such a measure of the noise requires that the electrodes are not driven by a drive signal, measurement of the noise may occur after each complete scan of the electrode array. That is to say, the capacitive touch sensor may be operated on a time division basis in which the capacitive touch sensor is operated in one of two frames—a measurement frame in which the capacitive touch sensor is configured to provide signals for each of the intersection points of the electrode array as described above, and a noise frame in which the capacitive touch sensor is configured to provide signals indicative of the noise of the electrode array. Operating in this way has an impact on the responsiveness of a touch sensor. For instance, the additional time required for the noise frame increases the time between measurement frames. While the capacitive touch sensor may not necessarily operate according to a noise frame between each measurement frame (for example the noise frame may be performed after every one, two, three, etc. measurement frames), the inclusion of a noise