Projective Capacitive Touch Ghost Position Filtering
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Solution Overview
Problem
Conventional projective capacitive touch apparatuses struggle to accurately identify distinctive touched positions during multi-touch operations due to the generation of ghost touched positions, which prevents the device from providing a reliable multi-touch function.
Innovation Solution
The apparatus employs a method and structure that includes a projective capacitive touch panel, a controller, and a processor to generate and filter reference values, where the processor identifies real touched positions by analyzing time differences between touches and filtering out ghost values, allowing for a scanning cycle shorter than the time difference between touches to determine the touch sequence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If projective capacitive touch panel uses conventional multi-touch detection method, then multi-touch function is enabled, but ghost touched positions are generated causing inaccurate position identification
Solution Approach 1:
The system performs preliminary scanning at a first scanning rate to detect potential touch positions before conducting detailed identification at a second scanning rate. This preliminary action allows the system to prepare reference data and anticipate multi-touch scenarios, enabling accurate distinction between real and ghost touch positions without compromising identification precision
Solution Approach 2:
The scanning rate is dynamically adjusted between a first scanning rate for initial detection and a second scanning rate for precise identification. This dynamic adjustment allows the system to optimize performance for different operational phases, maintaining high measurement precision while enabling comprehensive multi-touch detection
2Speed
If scanning cycle is shortened to capture touch sequence, then touch response speed is improved, but difficulty in distinguishing real touches from ghost touches increases
Solution Approach 1:
Reference values are pre-calculated and stored during a preliminary scanning phase before the actual touch detection. This preliminary preparation allows the system to quickly compare incoming touch data against known reference patterns during fast scanning, maintaining high touch response speed while simplifying the discrimination of ghost touches through pre-established comparison criteria
Solution Approach 2:
The system uses feedback from the comparison between detected touch positions and reference values to iteratively refine touch identification. By continuously comparing new touch data against stored reference patterns and adjusting identification algorithms based on comparison results, the system maintains accurate ghost touch discrimination even during high-speed scanning operations
3Ease of operation
If conventional touch schemes like resistive or surface acoustic wave are used, then simple touch detection is achieved, but multi-touch function cannot be accomplished
Solution Approach 1:
The projective capacitive touch panel is designed to perform multiple functions: it can detect single touches with simple capacitive sensing while simultaneously supporting multi-touch detection through coordinate generation and comparison algorithms. This universal design allows the same hardware structure to handle both simple and complex touch scenarios, achieving multi-touch capability without sacrificing detection simplicity
Solution Approach 2:
The touch detection process is segmented into distinct phases: initial touch detection, coordinate generation, reference value comparison, and ghost touch filtering. By dividing the complex multi-touch detection process into manageable segments, the system maintains the simplicity of basic capacitive sensing while adding sophisticated multi-touch capabilities through structured processing stages
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 effectively distinguishes between actual and ghost touched positions, enabling accurate multi-touch functionality and preventing misidentification of touch actions, thereby enhancing the device's ability to perform complex operations.
Implementation Method 1
the coordinates of the touched position is detected by sensing a current generated at the touched position in response to the capacitance variation arising from the static induction between the transparent electrode and finger
Implementation Method 2
the capacitance variation arising from the static induction between the transparent electrode and finger
Data Source
AI summary
A projective capacitive touch apparatus and a method for identifying multi-touched positions are provided. The multi-touched positions are touched on a projective capacitive touch panel. The method comprises the following steps: generating a first set of reference values according to the first touch position; generating a plurality of second sets of reference values according to a second touch position, and filtering out at least one ghost second set of reference values from the second sets of reference values. Furthermore, the plurality of second sets of reference values comprise a real second set of reference value and at least one ghost second set of reference values, while the ghost second set of reference values comprises parts of the first set of reference values.