Touch Sensor Signal Subtraction for Floating-State Touch Detection
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Solution Overview
Problem
Touch input devices with touch sensors struggle to accurately detect touch inputs and positions when in a floating state, particularly when multiple touches or cross touches occur, due to signal interference from Low Ground Mass (LGM) effects.
Innovation Solution
The touch input device incorporates a touch sensor with a plurality of driving and receiving electrodes, along with dummy electrodes, utilizing signal subtraction methods to differentiate between mutual capacitance and LGM-induced noise, enabling accurate touch detection even in floating states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a touch sensor uses driving and receiving electrodes in the same layer or dual layers to detect touch input, then the touch detection function is enabled, but in floating state the signal is split or disappears due to Low Ground Mass (LGM) effect
Solution Approach 1:
The receiving electrodes are divided into two types: regular receiving electrodes that form mutual capacitance with driving electrodes for touch detection, and dummy receiving electrodes that do not form mutual capacitance with driving electrodes. The dummy electrodes are used to measure and subtract LGM noise from the signals of regular electrodes, enabling accurate touch detection in floating state.
Solution Approach 2:
Dummy receiving electrodes serve as intermediary elements that measure the LGM noise component without being affected by touch input. These dummy electrodes mediate between the LGM interference and the regular receiving electrodes, allowing the system to separate and remove the noise component from the touch detection signal.
2Ease of operation
If the touch input device is in floating state, then portability and ease of use are improved, but signal detection accuracy deteriorates due to LGM effect causing signal splitting or disappearance
Solution Approach 1:
The system performs preliminary measurement of LGM noise using dummy receiving electrodes before processing the touch detection signal. By measuring the noise component in advance and subtracting it from the regular electrode signals, the system prepares a cleaned signal for accurate touch detection in floating state.
Solution Approach 2:
The system uses feedback from dummy receiving electrodes to continuously monitor and compensate for LGM noise. The noise measurement from dummy electrodes feeds back into the signal processing pipeline, enabling real-time correction of touch detection signals to maintain accuracy in floating state.
3Adaptability or versatility
If multiple receiving electrodes are used to detect multi-touch, then multi-touch recognition capability is enabled, but in floating state the LGM effect causes false multiple touch points or signal loss
Solution Approach 1:
The receiving electrode array is segmented into regular and dummy electrodes. This segmentation allows the system to separately measure LGM noise affecting all electrodes and subtract it from individual electrode signals, preventing false multi-touch detections caused by noise while preserving genuine multi-touch capability.
Solution Approach 2:
The LGM noise that causes false multi-touch signals is converted into a useful measurement by using dummy receiving electrodes. The noise signal measured from dummy electrodes is subtracted from regular electrode signals, transforming the harmful LGM effect into a correctable interference that can be removed to reveal genuine touch information.
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
The solution allows for reliable detection of single and multiple touches, including cross touches, in floating conditions, improving the accuracy and functionality of touch input devices.
Implementation Method 1
a first detection signal output from a predetermined receiving electrode that forms mutual capacitance with a predetermined driving electrode
Implementation Method 2
a second detection signal output from a predetermined receiving electrode that does not form mutual capacitance with a predetermined dummy driving electrode
Data Source
AI summary
An input device includes a touch sensor, which is capable of accurately detecting whether a touch input to a touch surface is input by an object or/and a touch position even in a situation where the touch input device is in a floating state. The touch input device includes a touch surface, including: a touch sensor which is disposed under the touch surface and includes a plurality of driving electrodes, a plurality of receiving electrodes, and a plurality of dummy receiving electrodes; and a touch detection unit configured to detect a touch position of an object input to the touch surface based on a detection signal output from the plurality of receiving electrodes of the touch sensor, in which the touch detection unit detects the touch position of the object input to the touch surface.