Touch Detection Using Complex Gradients for Noise Immunity
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Solution Overview
Problem
Touch-sensitive devices with floating ground conditions experience electrical noise interference, making it difficult to accurately detect touch inputs, especially distinguishing between multiple small inputs and a single larger input.
Innovation Solution
Driving subsets of touch-sensing electrodes with drive signals of different phases, calculating complex gradients between output signals, and identifying touch locations based on gradient magnitudes to improve signal-to-noise ratio and accuracy of touch input detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If touch-sensing electrodes are driven with a single phase signal, then the device structure is simple, but electrical noise from floating ground conditions interferes with touch input detection accuracy
Solution Approach 1:
The electrode array is divided into multiple groups, with each group driven by a separate drive signal with a different phase. This segmentation allows the system to process multiple phases simultaneously, improving touch detection accuracy by reducing the impact of electrical noise from floating ground conditions while maintaining a relatively simple overall device structure.
2Measurement precision
If multiple phases are used to reduce noise, then touch detection accuracy improves, but device complexity increases
Solution Approach 1:
The system uses periodic drive signals with different phases (e.g., 0°, 120°, 240°) to drive different electrode groups in a repeating cycle. This periodic multi-phase approach reduces electrical noise from floating ground conditions and improves touch detection accuracy while keeping the signal processing methodology systematic and manageable.
3Measurement precision
If electrical noise is present, then it becomes difficult to distinguish multiple small inputs from a single larger input, but using complex gradients increases processing requirements
Solution Approach 1:
Complex gradients are calculated between neighboring electrodes to serve as an intermediary measure that highlights touch input locations. By computing the gradient magnitude and phase between adjacent electrodes driven by different phases, the system can differentiate between multiple small touches and single larger touches more effectively, reducing the direct difficulty of detecting and measuring touch inputs in noisy conditions.
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
Enhances the accuracy of touch input detection in devices with floating ground conditions, improving human-computer interaction and reducing user input burden by distinguishing touch inputs more effectively.
Implementation Method 1
A touch-sensitive device may include a plurality of touch-sensing electrodes configured to detect proximity of an input object, such as a stylus or human finger
Data Source
AI summary
A method for touch detection includes, at a touch-sensitive device having a plurality of touch-sensing electrodes, driving a first subset of the plurality of touch-sensing electrodes with a drive signal having a first phase. A second subset of the plurality of touch-sensing electrodes are driven with a drive signal having a second phase, different from the first phase. Output signals for each of the plurality of touch-sensing electrodes are measured. For each touch-sensing electrode of the plurality of touch-sensing electrodes, a complex gradient is determined between the measured output signal for the touch-sensing electrode and the measured output signal for a neighboring touch-sensing electrode, the neighboring touch-sensing electrode driven with a different phase of a drive signal from the touch-sensing electrode. A location of a touch input is identified based at least in part on magnitudes of the determined complex gradients.