Capacitive Touch Driving Electrode Segmentation for Resolution and S/N Ratio
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Solution Overview
Problem
Capacitance-type touch panels face a trade-off between signal-to-noise ratio (S/N ratio) and detection accuracy, with small driving electrode areas resulting in low S/N ratio and large areas reducing detection resolution due to increased driving electrode width, which affects the minimum detectable object size.
Innovation Solution
The implementation of a contact detecting device with a detection drive scanning unit that selectively AC-drives a subset of driving electrodes, shifting the selection to include common electrodes before and after the shift operation, and using detection circuits to compare potentials with a threshold, thereby enhancing the AC potential change and position detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the area of driving electrodes is made small, then detection resolution is improved, but S/N ratio deteriorates
Solution Approach 1:
The patent divides the driving electrodes into multiple groups (first driving electrodes and second driving electrodes) that are driven alternately in a time-division manner. This segmentation allows each group to have smaller area for high resolution while the combined operation of multiple groups maintains sufficient S/N ratio through cumulative signal strength.
Solution Approach 2:
The patent implements periodic alternating driving of the first and second driving electrode groups. By periodically switching between the two groups, the system maintains continuous detection capability while distributing the signal load, thereby preserving both resolution and S/N ratio.
2Reliability
If the width of driving electrodes is increased, then S/N ratio is improved, but detection accuracy deteriorates
Solution Approach 1:
Instead of using a single large driving electrode, the patent segments the driving function into multiple smaller electrode groups. Each group has appropriate width for S/N ratio, while the segmented structure enables finer position detection through the alternating activation pattern, thus resolving the contradiction between electrode width and detection accuracy.
Solution Approach 2:
The patent introduces a time dimension to the electrode driving scheme by alternating between first and second driving electrode groups. This temporal dimension allows the system to achieve both sufficient S/N ratio (through multiple electrodes) and high detection accuracy (through precise temporal positioning of signal changes).
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach maintains high S/N ratio and detection accuracy by optimizing the number of driving electrodes and their width, allowing for precise detection of objects regardless of integration with or attachment to a display device.
Implementation Method 1
Capacitors are formed between the plural detection electrodes and the respective n driving electrodes
Data Source
AI summary
A contact detecting device includes: n driving electrodes that are arranged in a scanning direction; a detection drive scanning unit that selects continuous m (2≦m<n) driving electrodes out of the n driving electrodes, simultaneously AC-drives the selected m driving electrodes, and repeats shift operation for changing selection targets of the m driving electrodes in the scanning direction such that one or more driving electrodes common before and after the shift operation performed each time are included in the selection targets; plural detection electrodes that form capacitors, between which and the respective n driving electrodes capacitors are formed; plural detection circuits that are connected to the plural detection electrodes and compare potentials of the detection electrodes corresponding thereto with a predetermined threshold every time the detection drive scanning unit performs the shift operation.