Touch Slider-Position Sensing

BACKGROUND

Mobile/portable personal communications and computing devices can use touch (touch-on-surface) technology for input. For example, touch buttons and touch sliders can be integrated into a device case. Such touch input elements/apparatus are distinguished from, for example, capacitive touch buttons defined on a device display panel. These touch input elements/apparatus are commonly located on a case edge, but also can be located on a bezel area of the display surface, or on the back of the device case.

For such touch input elements (for example, sliders or buttons), touch sensing is used for touch sensing to detect, for example, touch-press (button) or a touch-position (slider). Touch sensing can be based on capacitive/inductive sensing of physical deflection/deformation of the touch surface, or capacitive human body (finger) touch/presence. Touch sensing technologies can be used with different touch surfaces, including metal (conductive), and glass/plastic (nonconductive), which depending on the application/technology can include a conductive coating.

Touch sensing technologies can be used to detect both XY touch position on a touch surface, and touch force, such as based on the amount of surface deflection, or a change in sensed human body capacitance as finger pressure expands a touch contact area.

BRIEF SUMMARY

This Brief Summary is provided as a general introduction to the Disclosure provided by the Detailed Description and Drawings, summarizing aspects and features of the Disclosure. It is not a complete overview of the Disclosure, and should not be interpreted as identifying key elements or features of, or otherwise characterizing or delimiting the scope of, the disclosed invention.

The Disclosure describes apparatus and methods for touch slider-position sensing based on calibration/touch vector processing.

According to aspects of the Disclosure, a touch slider-position sensing method is useable with a capacitive touch sensor that includes multiple capacitive electrodes arranged to define a slider track. The touch slider-position sensing methodology includes: (a) generating a set of calibration vectors for points of the slider track; (b) determining a touch slider-position based on (i) measuring a measurement/data vector associated with the touch-press slider-location, (ii) determining an angle between the measurement/data vector and a subset of the calibration vectors, and (iii) determining touch slider-position based on the angles between the measurement data vectors and the subset of calibration vectors.

In other aspects of the disclosure the touch slider-position methodology can include performing a quadratic or higher order interpolation of the angles between the measurement/data vector and the subset of the calibration vectors.

Other aspects and features of the invention claimed in this Patent Document will be apparent to those skilled in the art from the following Disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2A/2B illustrate example physical structures for a touch slider [10, 20] configured with multiple interdigitated touch sensors/electrodes, such as for implementing a touch slider element of a device case, with touch slider-position sensing according to this Disclosure: FIG. 1A illustrates an example two channel configuration with two interdigitated sensor electrodes [12A, 12B]; and FIGS. 2A/2B illustrate an example four channel configuration with four interdigitated sensors configured from five electrodes [22A-22E], with end electrodes [22A and 22E] coupled in series as a single end-point sensor.

FIGS. 3A and 3B are an example plots illustrating calibration data collection for defining calibration vectors for use in touch slider-position sensing based on calibration/touch vector processing according to the Disclosure, for an example a touch slider with four touch sensors [FIGS. 2A/2B].

FIG. 4 is an example plot illustrating touch slider-position sensing based on calibration (R) and touch (D) vector processing according to aspects of the Disclosure.

FIGS. 5A and 5B are example plots illustrating an aspect of touch slider-position sensing based on calibration/touch vector processing according to this Disclosure, using interpolation (in this example, quadratic) to identify a local maximum corresponding to touch slider-position.

DETAILED DESCRIPTION

This Description and the Drawings constitute a Disclosure for touch slider-position sensing based on calibration/touch vector processing, including describing design examples (example implementations), and illustrating various technical features and advantages.

This Disclosure uses the following nomenclature. A “touch slider” is a linear position sensor for sensing touch position along a linear slider/track defined by touch-slider element integrated into a device.

In an example application, the touch slider-position sensing methodology according to the Disclosure based on calibration/touch vector processing can be used to implement a touch slider element integrated into the case of a mobile communications device, such as on an edge panel/wall of the case.

In brief overview, a method suitable for touch slider-position sensing with a capacitive touch sensor that includes multiple capacitive electrodes arranged to define a slider track, includes: (a) generating a set of calibration vectors for points of the slider track; (b) determining a touch slider-position based on (i) measuring a measurement/data vector associated with the touch-press slider-location, (ii) determining an angle between the measurement/data vector and a subset of the calibration vectors, and (iii) determining touch slider-position based on the angles between the measurement data vectors and the subset of calibration vectors. To improve resolution, the method can include performing a quadratic or higher order interpolation of the angles between the measurement/data vector and the subset of the calibration vectors.

FIGS. 1 and 2A/2B illustrate example physical embodiments/structures for a capacitive touch slider, each with multiple capacitive interdigitated sensor electrodes, such as for implementing a touch slider element of a device case with touch slider-position sensing according to the Disclosure.

Touch slider position-sensing for sensing linear slider-position on a touch-slider according to the Disclosure, is based on calibration/touch vector processing, which is independent of sensor electrode configuration. In particular, touch slider position-sensing according to the Disclosure and can be scaled to different sensor electrode configurations, with different multi-electrode configurations and layouts, as required to achieve a desired performance/resolution for the touch slider.

FIG. 1 illustrates an example touch-slider sensor 10 in a two channel sensor configuration, with two interdigitated sensor electrodes 12A and 12B.

FIGS. 2A/2B illustrate (different views) an example four channel touch-slider sensor configuration 20A/20B, with four sensors configured from five interdigitated electrodes 22A-22E, with end electrodes 22A and 22E coupled in series as a single end-point sensor (this configuration is designated 22A/22E-22D).

An example touch slider implementation based on capacitive touch slider-position sensing according to the Disclosure, includes a touch slider sensor configuration with multiple capacitive sensor electrodes in a defined configuration/layout, and capacitive sensor electronics coupled to the each sensor electrode.

The design of the sensor electronics is not important to the touch slider-position sensing methodology, which is based on calibration/touch vector processing according to the Disclosure. For the example touch slider implementation based on capacitive touch slider-position sensing, a multi-channel capacitance-to-data converter (CDC) can be used, with each excitation/acquisition channel coupled to an associated slider sensor electrode (such as slider sensor electrodes 22A/22E-22D in FIG. 1B).

The following description of an example implementation of touch slider-position sensing based on calibration/touch vector processing according to the Disclosure is in the context of the example capacitive touch slider configuration of FIGS. 2A/2B, with four sensor channels (five interdigitated sensor electrodes 22A/22E-22D, where end point sensor electrodes 22A and 22E are series connected to provide a single end position sensor/channel). The example four channel touch slider sensor includes N=5 interdigitated sensor electrodes (five separate electrode sections/areas defining a linear slider/track).

During operation, capacitive data is collected from these N sensors to determine linear slider-position (X) of a finger, hand, or other capacitive object relative to the touch-slider element/track.

A initial calibration is performed, prior to touch slider operation, to collect calibration vector data. For example, calibration can be performed as follows.

- Pre-determined positions on the slider are touched, and capacitive calibration data for each sensor electrode is measured. The example plots in FIGS. 3A/3B illustrate response averaging based on touching a slider-position 10 times.
- Then the calibration data is post-processed to eliminate a DC component. For example, DC elimination can be based on removing a long-term moving average, or using a baseline tracking technique.
- Then, a maximum delta-capacitance SC response is determined for each of the four sensor electrodes.

Alternatively, a delta-capacitance response SC can be measured as follows: (a) measure 0-level (no touch) capacitances of the N=5 sensor electrodes (22A/22E-22D in FIGS. 2A/2B); (b) measure capacitances for a touch-press at known slider-position X; and (c) then take the difference to derive delta-capacitance response δC.

This procedure is repeated at several known slider-positions X, for example, every 1 cm starting from end position 0 to end position L (for example, 10 cm) on the slider/track.

As a result, L+1 (for example, L=10 plus the zero position) sets of SC responses are measured for each of the N sensor electrodes (22A/22E-22D in FIG. 1B) at the known X position. That is, L+1 response calibration vectors are determined, where each response calibration vector {right arrow over (R)} is given by the SC response as measured by the sensor channel for the associated sensor electrode, {right arrow over (R)} (X)=(R₀, R₁, . . . , R_N) where R_iis a δC response of each of the N sensor electrodes at position X.

FIG. 4 is an example plot illustrating touch slider-position sensing based on calibration/touch vector processing with calibration (R) and touch (D) vectors according to aspects of the Disclosure.

During touch slider operation, sensor data is continuously measured within pre-defined sensing periods (i.e., at a predefined sensing frequency). The DC component is subtracted from the data (for example, by removing long-term moving average, or using a baseline tracking technique). The remaining AC signal is a vector {right arrow over (D)}=(D₀, D₁, . . . , D_N), where D_iis a capacitance δC response of each sensor electrode. To determine if a touch-press is occurring, the touch slider-position sensing methodology calculates, in each sensing period, the length of data vector

{right arrow over (D)}:|{right arrow over (D)}|=√{square root over (Σ_i=0^ND_i²)}

and compares it to a predefined threshold value T.

If the data vector magnitude D is greater than the threshold T, a touch-press is detected, and the methodology proceeds to determine touch slider-position.

Touch slider-position sensing according to the Disclosure is based on calibration/data vector processing. For each of the response calibration vectors {right arrow over (R)}, the cosine is determined between the measurement/data vector {right arrow over (D)} and {right arrow over (R)}:

$Cos (α) \frac{\sum_{i = 0}^{N} R_{i} * Di}{\langle \vec{D} \rangle * : \langle \vec{R} \rangle},$

where

|{right arrow over (R)}| is the length of the calibration vector:

$\langle \vec{R} \rangle = \sqrt{\sum_{i = 0}^{N} R_{i}^{2}}$

These determinations obtain Cos(α) as an angle between the measurement/data vector {right arrow over (D)} and the calibration vector {right arrow over (R)} associated with each of the calibration positions X.

FIG. 4 provides an example plot for this dependency, for an example slider 23 cm-long.

If the touch-press occurs at slider-position X, the current measurement/data vector will align well with calibration response vectors close to position X, i.e. the angle between measurement/data vector {right arrow over (D)} and calibration vectors {right arrow over (R)} will be close to 0, and cosine of the angles will be close to 1. The plot demonstrates this relationship for cosines around 4 cm are close to 1, indicating good alignment between current measurement/data vector and calibration vectors around X=4.

FIGS. 5A and 5B are example plots illustrating an aspect of touch slider-position sensing based on calibration/touch vector processing according to the Disclosure, using interpolation to identify a local maximum corresponding to touch slider-position. In this example, quadratic interpolation is used. Cubic or higher order interpolation can be used.

Resolution can be increased by using interpolation to determine a local maximum point for Cos(α) vs X. For example, to identify a touch slider-position, the methodology can proceed to identify a peak position for Cos(α) vs X. Points surrounding the maximum (X=4 in this example) are identified, and a quadratic interpolation is performed, using measurements at X=3, 4, and 5. For higher order interpolations, more surrounding points are used.

Using interpolation, a formula can be identified that gives a fit on the measurement/data points. A maximum of this function can be identified, around an initial measured maximum position, to find an interpolated maximum position with higher resolution (limited only by the noise in the measurement system). For example, in FIG. 5B, a touch position of X=3.7565 can be identified.

Note that the cosine did not go to 1, because of noise, so that the four dimensional vectors do not align exactly.

The Disclosure provided by this Description and the Figures sets forth example designs and applications illustrating aspects and features of the invention, and does not limit the scope of the invention, which is defined by the claims. Known circuits, connections, functions and operations are not described in detail to avoid obscuring the principles and features of the Disclosed example designs and applications. This Disclosure can be used by ordinarily skilled artisans as a basis for modifications, substitutions and alternatives, including adaptations for other applications.

Touch Slider-Position Sensing

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