Shield Electrode Pattern Matching for Touch Sensor Accuracy
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Solution Overview
Problem
In self-capacitance touch panels, variations in the resistance of the shield electrode and differences in the distance to the power supply circuit cause in-plane variations in the detection signal output, affecting the accuracy of detecting objects, particularly in hover sensors that require height direction coordinate detection.
Innovation Solution
A detection device is designed with a shield layer and a sensor layer, where the shield electrode and sensor electrode have the same planar pattern, overlapping each other, and their connection wirings also match, reducing parasitic capacitance and in-plane variations by adjusting the wiring lengths and using materials like transparent conductive oxides or metals, and incorporating a correction processing to adjust the timing of the detection signal amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the shield electrode is provided to suppress influence from the non-detection surface, then the detection accuracy is improved, but in-plane variations in detection signal occur due to resistance variations and distance differences to power supply circuit
Solution Approach 1:
The patent creates a dummy electrode that copies the pattern and electrical characteristics of the sensor electrode. This dummy electrode is connected to the same power supply circuit through wiring with matched length and material, creating an identical electrical path. By measuring the potential distribution on this copied electrode structure, the system can predict and correct in-plane variations that would otherwise affect the actual sensor electrode, thereby resolving the contradiction between detection accuracy and in-plane uniformity.
Solution Approach 2:
The dummy electrode acts as an intermediary that experiences the same electrical conditions (power supply distance, resistance, potential distribution) as the sensor electrode but is not used for actual detection. This intermediary structure allows the system to measure and characterize the in-plane variations caused by the power supply circuit layout, and use this information to correct the actual detection signals, thus resolving the contradiction without modifying the shield electrode structure.
2Ease of manufacture
If different wiring lengths are used for sensor electrode and shield electrode, then connection to power supply is simplified, but parasitic capacitance increases affecting detection precision
Solution Approach 1:
The patent applies different wiring configurations to different parts of the electrode structure based on their specific functions. The sensor electrode wiring is optimized for detection sensitivity, while the shield electrode wiring is designed to match the sensor electrode's electrical characteristics (length, material, capacitance) rather than prioritizing power supply connection simplicity. This localized optimization resolves the contradiction by allowing simplified power connection where needed while maintaining precise electrical matching where it affects detection accuracy.
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 configuration improves the positional accuracy of object detection by minimizing in-plane variations and parasitic capacitance, enabling precise detection of objects in both contact and non-contact states, including height coordinates.
Implementation Method 1
the electrostatic capacitance method, particularly a self-capacitance method, is adopted when detecting an object to be detected in proximity
Implementation Method 2
variations in the resistance of the shield electrode and differences in the distance to the power supply circuit cause in-plane variations in the detection signal output
Data Source
AI summary
A detection device includes a shield layer provided with a shield electrode and a shield electrode connection wiring connected to the shield electrode, and a sensor layer located over the shield layer and provided with a sensor electrode and a sensor electrode connection wiring connected to the sensor electrode. The shield electrode has the same planar pattern as the sensor electrode and overlaps the sensor electrode. The shield electrode connection wiring has the same planar pattern as the sensor electrode connection wiring and overlaps the sensor electrode connection wiring.