Transcapacitive Sensing Motion Artifact Suppression
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Solution Overview
Problem
Capacitive sensing technologies face challenges in accurately detecting input objects due to motion artifacts, which can result in false reporting and jitter, especially when input objects move rapidly or codes are run for extended periods, leading to decreased signal-to-noise ratios and increased motion artifacts.
Innovation Solution
The method involves performing two or more different types of transcapacitive scans to acquire sub-frame images and combining them to suppress motion artifacts, using techniques such as complementary low-off-peak correlation scanning codes and varying signal-to-noise ratio techniques to construct a combined capacitive image with reduced motion artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transcapacitive scans are performed for extended periods or with longer codes to improve signal-to-noise ratio, then measurement precision improves, but motion artifacts increase and reliability decreases
Solution Approach 1:
The sensing frame is divided into multiple sub-frames, each acquired with different transmitter electrode driving patterns. By segmenting the scan into multiple passes with varied excitation patterns, the system can combine results to suppress motion artifacts while maintaining adequate signal-to-noise ratio.
Solution Approach 2:
The system performs periodic scanning with alternating or complementary coding patterns across different sub-frames. This periodic variation in excitation patterns allows the system to distinguish between stationary objects and motion artifacts through differential analysis of the periodic responses.
2Productivity
If input objects move rapidly during scanning, then productivity increases, but measurement precision decreases due to motion artifacts and false reporting
Solution Approach 1:
The system dynamically adapts the transmitter electrode driving patterns between sub-frames to account for object motion. By varying the excitation patterns and timing, the system can track and compensate for rapid movements, maintaining measurement precision even at higher scanning speeds.
Solution Approach 2:
The system uses feedback from multiple sub-frame acquisitions with different patterns to identify and correct for motion-induced errors. By comparing results across sub-frames and analyzing inconsistencies, the system can distinguish true signal from motion artifacts and adjust accordingly.
3Reliability
If multiple different transcapacitive scans are performed and combined, then motion artifact suppression improves, but device complexity increases
Solution Approach 1:
The system changes parameters such as transmitter electrode driving patterns and scanning sequences across sub-frames to suppress motion artifacts. By systematically varying these parameters and using predetermined combination rules, the system achieves motion artifact suppression without requiring complex real-time processing.
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 enhances the accuracy of input object detection by suppressing motion artifacts, improving signal-to-noise ratios, and providing a more reliable capacitive image, thereby improving the usability and precision of capacitive sensing systems.
Implementation Method 1
transcapacitive sensing frame... plurality of transmitter electrodes... plurality of receiver electrodes... capacitive image
Data Source
AI summary
In a method of input object sensing, a plurality of transmitter electrodes are driven in a first way to acquire a first sub-frame image with the plurality of transmitter electrodes and a plurality of receiver electrodes of a sensor electrode pattern during a first sub-frame of a transcapacitive sensing frame. The plurality of transmitter electrodes is also driven in a second way to acquire a second sub-frame image with the plurality of transmitter electrodes and the plurality of receiver electrodes during a second sub-frame of the transcapacitive sensing frame, wherein the first way and the second way differ. A capacitive image is determined by combining the first sub-frame image with the second sub-frame image such that a motion artifact associated with an input object and present in at least one of the sub-frame images is suppressed by the combining.