Wet Touch Panel Finger Positioning via Capacitance Segmentation
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Solution Overview
Problem
Capacitive touch panels struggle to accurately determine the relative position of a finger in relation to a wet region, leading to inaccurate responses due to the presence of water or moisture, which affects normal operation.
Innovation Solution
A method and apparatus that search for suspect wet regions on a touch panel using spacing coding, determine the wet region using self-capacitive coding, and assess detection channels to establish the relative position of the finger by analyzing feature data differences within and outside the wet region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional capacitive touch detection is used on a wet touch panel, then the touch panel can operate in wet environments, but the accuracy of finger position detection deteriorates due to interference from water conductivity
Solution Approach 1:
The touch panel detection is divided into two distinct phases: wet region detection phase and finger touch detection phase. During the wet region detection phase, the system identifies and segments the wet region boundaries using capacitance threshold methods. During the finger touch detection phase, the system only processes touch signals within the dry region, effectively segmenting out the interfering wet region signals. This segmentation allows the system to maintain both wet environment adaptability and finger position detection accuracy.
Solution Approach 2:
The system performs preliminary detection of wet regions before processing finger touch signals. By first identifying the wet region boundaries and storing this information, the system prepares in advance for accurate finger position detection by excluding wet region areas from subsequent touch calculations. This preliminary action ensures that finger position accuracy is not compromised by the presence of water on the panel.
2Device complexity
If the system processes all detection channels uniformly, then the processing logic remains simple, but the system cannot distinguish between wet regions and actual touch positions
Solution Approach 1:
The system applies different processing qualities to different regions of the touch panel. Wet regions are identified using specific capacitance threshold criteria and are then excluded from finger touch detection processing. Dry regions continue to use standard touch detection algorithms. This local differentiation allows the system to maintain simple overall logic while achieving accurate touch position identification by treating wet and dry regions differently.
Solution Approach 2:
The system introduces an intermediary wet region mask that acts as a mediator between the raw detection signals and the final touch position calculation. This mask is generated by comparing detection channel capacitance values against thresholds to identify wet regions, and then it is used to filter or weight the touch detection calculations. This intermediary structure enables accurate touch identification without requiring complete redesign of the processing logic.
3Device complexity
If the system uses only self-capacitive coding for wet region detection, then the detection method remains simple, but the system cannot accurately determine the relative position of the finger in wet conditions
Solution Approach 1:
The system merges two detection approaches: self-capacitive coding for wet region detection and mutual-capacitive coding for finger touch detection. The self-capacitive phase identifies wet region boundaries by detecting capacitance changes caused by water. The mutual-capacitive phase then uses these boundaries to accurately locate finger touches in the remaining dry regions. This combination maintains relative simplicity while achieving accurate finger positioning in wet conditions.
Solution Approach 2:
The system dynamically switches between different detection modes based on environmental conditions. When water is detected on the panel, the system activates the wet region detection mode using self-capacitive coding, identifies the wet boundaries, then transitions to finger touch detection mode using mutual-capacitive coding in the dry regions. This dynamic adaptation allows accurate finger position measurement despite changes in panel moisture conditions.
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
Enables accurate finger positioning and response in wet conditions by distinguishing between wet and pseudo-wet regions, ensuring reliable touch operations even when the panel is exposed to moisture.
Implementation Method 1
When a user touches the CTP, due to the electric field of the human body, a finger of the user forms a coupling capacitor with a working surface of the CTP, and a series of touch operation functions are implemented by detecting the capacitance value of the coupling capacitor
Data Source
AI summary
A method and apparatus for positioning a finger on a touch panel in a wet state and a touch detection apparatus are provided. The method includes: searching out suspect wet regions on the touch panel in a spacing coding manner, and determining a wet region from the suspect wet regions in a self-capacitive coding manner; traversing detection channels in the self-capacitive coding manner, and judging whether the detection channels satisfy a first condition; and if the detection channels in the wet region satisfy the first condition, determining a relative position relationship between a touch position of a finger and the wet region according to variations of feature data differences of the detection channels on the entire touch panel; or determining a relative position relationship between a touch position of a finger and the wet region according to variations of feature data differences of the detection channels outside the wet region.