Capacitive Input Surface With Movable Electrode for Sensitive Touch Detection
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Solution Overview
Problem
Conventional input devices using pressure sensors have limited sensitivity in detecting proximity and touch, particularly when a finger is used, as the capacitance changes are not effectively captured, leading to reduced detection accuracy.
Innovation Solution
The input device incorporates a movable electrode and fixed electrodes with a direct-connection line that allows for sensitive detection of capacitance changes between the electrode and the operation body, enhancing the detection of proximity and touch by using a capacitive sensor configuration with a movable electrode that is capacitively coupled to the fixed electrode, and outputs electric signals containing changes in capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional pressure sensor with movable electrode and fixed electrode is used, then the device structure is simple, but the detection sensitivity for proximity and touch is limited
Solution Approach 1:
The electrode system is segmented into multiple fixed electrodes (first fixed electrode, second fixed electrode) and a movable electrode, with each electrode pair serving distinct detection functions. The first fixed electrode detects capacitance changes for proximity detection, while the second fixed electrode detects capacitance changes for touch detection, thereby enhancing overall detection sensitivity through functional segmentation
Solution Approach 2:
A capacitor is introduced as an intermediary element in the signal transmission path between the movable electrode and the output terminal. This capacitor couples the capacitance change signals from the movable electrode to the output, enabling sensitive detection of both proximity and touch operations while isolating the electrode system from direct electrical connection to external circuits
2Measurement precision
If the movable electrode is directly connected to the output terminal via a direct-connection line, then the detection sensitivity is improved, but the device complexity increases
Solution Approach 1:
The direct connection between the movable electrode and output terminal is extracted as a separate direct-connection line, distinct from the capacitive coupling path. This allows the capacitance change signals to be transmitted directly to the output terminal with minimal interference, improving detection accuracy while maintaining a manageable device structure through clear separation of signal paths
Solution Approach 2:
The movable electrode serves multiple functions simultaneously: it acts as one element of the capacitor for capacitive coupling to fixed electrodes, forms a direct connection path to the output terminal for signal transmission, and responds to both proximity and touch operations. This multi-functionality enhances detection capabilities without proportionally increasing device complexity
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 significantly improves the sensitivity of detecting proximity and touch, allowing for accurate and reliable input operations by effectively capturing capacitance changes, thereby enhancing the overall performance of the input device.
Implementation Method 1
The movable electrode has a lower surface facing an upper surface of the first fixed electrode to be capacitively coupled to the first fixed electrode. The movable contact is displaceable to approach the first fixed electrode in response to a pressing of the detection surface by the operation body.
Implementation Method 2
The second terminal is configured to output, from the movable electrode to the outside of the input device, a second electric signal containing a change in a capacitance between the operation body and the movable electrode.
Data Source
AI summary
An input device includes a detection surface configured to be operated by an operation body, a first fixed electrode, a movable electrode, first and second terminals configured to be connected to an outside of the input device, and a direct-connection line electrically connecting the movable electrode to the second terminal via no capacitor. The movable electrode has a lower surface facing an upper surface of the first fixed electrode to be capacitively coupled to the first fixed electrode. The movable contact is displaceable to approach the first fixed electrode in response to a pressing of the detection surface by the operation body. The first terminal is configured to output, to the outside of the input device, a first electric signal containing a change in a capacitance between the first fixed electrode and the movable electrode. The second terminal is configured to output, from the movable electrode to the outside of the input device, a second electric signal containing a change in a capacitance between the operation body and the movable electrode. This input device improves the detection sensitivity to detect approximating or contacting the input device by the operation body.