Capacitive Touch Position Detection Under Foreign Object Interference
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Solution Overview
Problem
Existing position detection systems fail to accurately detect finger movements when a foreign object, such as a coin, is pressed against the touch surface, leading to inflexible position detection.
Innovation Solution
A position detection circuit and method that utilizes a capacitive touch sensor with two-dimensionally arranged line electrodes, employing different touch detection conditions for areas with and without foreign objects, to accurately detect touch positions and areas even when foreign objects are present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If uniform touch detection conditions are applied across the entire touch sensor area, then the detection system remains simple and consistent, but it cannot accurately distinguish between finger touches and foreign objects, leading to detection errors
Solution Approach 1:
The patent applies different touch detection conditions to different regions of the touch sensor. Specifically, when a foreign object is detected in a first area, the system switches to first touch detection conditions for that area, while maintaining second touch detection conditions for other areas. This allows the system to optimize detection accuracy locally without complicating the entire detection system.
Solution Approach 2:
The patent dynamically adjusts touch detection conditions based on the presence of foreign objects. The control circuit switches between different detection conditions in real-time according to the detected state, making the detection system adaptive rather than static. This dynamic adjustment improves measurement precision without requiring a permanently complex system architecture.
2Reliability
If the system invalidates all coordinate values when a foreign object is detected, then operation errors from foreign objects are prevented, but legitimate finger movements are also missed, reducing detection flexibility
Solution Approach 1:
The patent applies different validity rules to different areas. Coordinate values from areas where foreign objects are detected are invalidated, while coordinate values from areas without foreign objects remain valid. This selective validation approach maintains reliability by preventing errors from foreign objects while preserving detection flexibility for legitimate user interactions in unaffected areas.
Solution Approach 2:
The touch sensor area is segmented into multiple regions, and the system independently manages detection validity for each region. When a foreign object is detected in one area, only that specific area's coordinate values are invalidated, while other areas continue normal operation. This segmentation allows the system to maintain high reliability locally without sacrificing overall detection flexibility.
3Measurement precision
If different touch detection conditions are applied to different areas based on foreign object presence, then detection accuracy is improved, but the control and management of detection conditions becomes more complex
Solution Approach 1:
The patent implements a feedback mechanism where the control circuit continuously monitors for foreign objects and automatically adjusts detection conditions based on the detected state. When a foreign object is detected in a first area, the system automatically switches to appropriate detection conditions for that area. This feedback-based automatic adjustment improves measurement precision while minimizing the complexity of manual condition management.
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 flexible and accurate position detection by distinguishing between touch signals from fingers and foreign objects, enhancing the detection of finger movements and reducing interference from foreign objects like coins or water drops.
Implementation Method 1
a capacitive touch sensor formed with a plurality of line electrodes that are two-dimensionally arranged
Data Source
AI summary
A position detection method performed using a capacitive touch sensor with line electrodes two-dimensionally arranged. The method includes: acquiring first two-dimensional data indicating a first distribution of detection values of capacitance on the touch sensor; recognizing that a foreign object is present in an area on the touch sensor based on the first two-dimensional data; in response to the recognizing that the foreign object is present in the area on the touch sensor based on the first two-dimensional data, using a first threshold that is lower than a second threshold for detecting a first touch position or touch area inside of the area on the touch sensor in which the foreign object is present; and detecting the first touch position or touch area inside of the area on the touch sensor in which the foreign object is present based on the first two-dimensional data and the first threshold.