Touch Sensor Ghost Input Reduction via Dynamic Scan States
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Solution Overview
Problem
Touch sensors often experience 'ghost inputs' where a touch input is detected at a location that is not actually receiving a touch, leading to inaccurate input detection.
Innovation Solution
The implementation of a touch sensor system that uses a matrix of row and column traces with piezoresistive material, employing different scan states to distinguish between actual and ghost inputs by measuring resistance changes at intersections, allowing for accurate detection of touch location and force through the use of driver and reader signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a touch sensor uses a matrix of row and column traces to detect touch location, then touch location detection capability is provided, but ghost inputs are detected at locations not actually receiving touch
Solution Approach 1:
The patent applies dynamics by implementing multiple scan states (with-floating and without-floating) that dynamically change the electrical configuration of the touch sensor matrix. By switching between different scan states, the system can differentiate between actual touch inputs and ghost inputs, as real touches respond differently to state changes compared to ghost inputs. This dynamic scanning approach resolves the contradiction by maintaining location detection capability while eliminating false detections.
Solution Approach 2:
The patent utilizes parameter changes by varying the scan state parameters (floating vs. non-floating conditions) to detect touch inputs. By changing the electrical parameters of the row and column traces between different scan states, the system can identify genuine touches based on their consistent response across state changes, while ghost inputs show inconsistent or absent responses. This parameter variation resolves the technical contradiction between detection capability and accuracy.
2Adaptability or versatility
If a touch sensor detects touch input at multiple intersections simultaneously, then multi-touch capability is enabled, but ghost inputs increase due to current paths between touches
Solution Approach 1:
The patent applies dynamics by using different scan states that change the electrical configuration during multi-touch detection. When multiple touches are detected, the system switches between with-floating and without-floating scan states to trace current paths and identify which detected inputs are genuine versus ghost inputs. This dynamic approach enables multi-touch capability while maintaining reliability by filtering out false detections caused by current leakage between simultaneous touches.
Solution Approach 2:
The patent implements feedback by analyzing the response of each intersection across different scan states. The system uses the differential response between with-floating and without-floating states as feedback to determine whether a detected touch is real or a ghost input. This feedback mechanism allows the touch sensor to accurately distinguish genuine multi-touch inputs from false detections, resolving the contradiction between multi-touch versatility and detection accuracy.
3Device complexity
If a touch sensor uses conventional scanning methods, then device complexity is minimized, but ghost inputs cannot be distinguished from actual touches
Solution Approach 1:
The patent applies dynamics by implementing a multi-state scanning method that cycles between with-floating and without-floating conditions. This dynamic scanning approach enhances measurement precision by allowing the system to differentiate ghost inputs from real touches based on their differential responses to state changes. The method maintains reasonable device complexity by using systematic state transitions rather than requiring complex additional hardware, resolving the contradiction between scanning simplicity and detection accuracy.
Solution Approach 2:
The patent utilizes periodic action by implementing a scanning sequence that periodically switches between different scan states. The systematic alternation between with-floating and without-floating states creates a periodic measurement pattern that enables ghost input detection. This periodic scanning approach improves measurement precision while maintaining manageable device complexity through structured, repeating measurement cycles.
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 reduces the detection of ghost inputs by differentiating current values obtained during 'with-floating' and 'without-floating' scan states, ensuring precise identification of touch inputs and their locations, enhancing the accuracy of touch input detection.
Implementation Method 1
The touch sensor includes a matrix of row traces, a matrix of column traces and piezoresistive material intersecting at multiple intersections
Data Source
AI summary
A method and apparatus for detecting touch input at a touch sensor is provided. The touch sensor comprises a plurality of row traces, a plurality of column traces and an intersection corresponding to an identified row trace of the plurality of row traces and an identified column trace of the plurality of column traces. The touch sensor also includes at least one driver for driving the plurality of column traces and at least one reader for reading the plurality of row traces. The drivers and the readers scan the identified intersection by entering into a with-floating scan state, reading a first value for the identified row trace, entering into a without-floating scan state and reading a second value for the identified row trace. The presence of a touch input is accordingly determined based on the first and second values.