Differential Force and Touch Sensing via Anti-Guarding
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Solution Overview
Problem
Existing input devices face challenges in distinguishing between touch and force signals, leading to increased manufacturing costs, thickness, and reduced functionality due to the need for dedicated force sensor electrodes and routing, which complicates simultaneous touch and force sensing.
Innovation Solution
The implementation of an input device with sensor electrodes that deflect towards force electrodes, using anti-guarding and in-phase/quadrature demodulation techniques to differentiate between touch and force signals, allowing for accurate and simultaneous touch and force sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dedicated force sensor electrodes and routing are added to enable force sensing, then force sensing capability is improved, but manufacturing cost, device thickness, and complexity increase
Solution Approach 1:
The sensor electrodes serve dual functions: they detect touch input through capacitive coupling and simultaneously detect force through their deflection toward force electrodes. This eliminates the need for separate dedicated force sensor electrodes and routing, reducing device complexity while maintaining both touch and force sensing capabilities
Solution Approach 2:
The patent combines touch sensing and force sensing into a single integrated system where sensor electrodes perform both functions. The sensor electrodes are positioned between the input surface and force electrodes, allowing them to detect both capacitive changes from touch and mechanical deflection from force, thereby merging two sensing modalities into one component
2Measurement precision
If sensor electrodes are deflected toward force electrodes for force sensing, then force sensing accuracy is improved, but distinction between touch and force signals becomes more difficult
Solution Approach 1:
The system applies periodic modulation signals to the sensor electrodes and force electrodes at different phases. By modulating the sensor electrodes with a reference signal and the force electrodes with a phase-shifted signal, the system creates distinct temporal patterns that allow the processing system to differentiate between touch-induced capacitive changes and force-induced deflection through phase-sensitive detection
Solution Approach 2:
The patent changes the phase parameter of the modulation signals applied to different electrode groups. The sensor electrodes are driven with a modulated reference voltage while force electrodes receive signals with different phase characteristics, creating distinguishable signal patterns that enable the processing system to separate touch and force components even though both affect sensor electrode deflection
3Loss of time
If narrow bandwidth sensing is implemented to reduce latency, then reporting speed is improved, but signal processing complexity increases
Solution Approach 1:
The system performs preliminary modulation of the electrode signals before measurement, embedding the sensing signals with known phase relationships. This preliminary action allows the processing system to use simpler demodulation and phase-comparison operations rather than requiring complex real-time analysis, reducing both latency and processing complexity
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 reduces latency and increases accuracy in signal correlation, enabling fast and precise differential touch and force sensing without the need for additional costly components, thereby enhancing the functionality and efficiency of input devices.
Implementation Method 1
the plurality of sensor electrodes configured to deflect toward the at least one force electrode in response to a force applied to the input surface
Implementation Method 2
receive resulting signals comprising effects of user input upon the coupling of at least one of the modulated reference voltage, the guarding voltage, or the anti-guarding voltage, the effects indicative of changes in capacitance of the plurality of sensor electrodes
Implementation Method 3
drive the plurality of sensor electrodes with a modulated reference voltage
Implementation Method 4
drive the at least one force electrode by alternating between a guarding voltage modulation and an anti-guarding voltage modulation, wherein the guarding voltage modulation is in-phase with respect to the modulated reference voltage, and wherein the anti-guarding voltage is out of phase with respect to the modulated reference voltage
Data Source
AI summary
An input device is configured to detect force being applied to an input region of the device by an input object, in addition to the position of the input object using touch sensing methods. Aspects include driving a force sensing electrode of the input device using an anti-guarding voltage alternating with a ground or guard voltage, while driving the touch sensing electrodes with a reference voltage, to obtain touch measurements, force measurements, interference measurements, double the force signal, and/o double the touch signal for differential touch and force detection. Aspects also include driving sensor electrodes using orthogonal signals and performing in-phase and quadrature demodulation of the received signal for simultaneous and independent touch and force measurements.