Touch Panel Signal Processing Noise Rejection
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Solution Overview
Problem
The existing signal processing methods for capacitive touch panels in touch-sensitive displays suffer from reduced accuracy due to noise-like electric fields generated during image data writing operations, leading to misjudgment of touch events, especially during heavy touches, and fail to distinguish between soft and heavy touches effectively.
Innovation Solution
A signal processing method that amplifies the first sensing signal by the number of adjacent second touch sensing units, generates a difference signal by subtracting the sum of second sensing signals from the amplified first signal, and compares it with thresholds to accurately determine touch events, thereby avoiding average calculation and reducing noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the average of second sensing signals is calculated for touch event judgment, then the signal processing can be simplified, but the signal processing accuracy is reduced
Solution Approach 1:
The patent extracts and eliminates the averaging operation from the signal processing method. Instead of calculating the average of second sensing signals, the invention directly uses the first sensing signal after amplification and compares it with the sum of second sensing signals, thereby removing the source of accuracy reduction while maintaining processing simplicity.
Solution Approach 2:
The patent inverts the conventional approach by not averaging the second sensing signals but rather summing them directly and comparing with the amplified first sensing signal. This inversion of the processing logic eliminates the accuracy penalty associated with averaging while keeping the computational complexity low.
2Reliability
If the first threshold value is increased to avoid misjudging touch events, then false positive reduction is achieved, but soft touch event detection capability is lost
Solution Approach 1:
The patent changes the threshold comparison parameter from a single fixed threshold to a dynamic threshold based on the sum of second sensing signals. The first threshold value is adjusted according to the signal strength from adjacent units, allowing the system to distinguish between soft touches (lower threshold) and heavy touches (higher threshold), thereby resolving the contradiction between reliability and detection accuracy.
3Object-affected harmful factors
If noise-like electric field interference is present during heavy touch, then the interference affects the sensing accuracy, but increasing the threshold value cannot eliminate the interference effect
Solution Approach 1:
The patent introduces the sum of second sensing signals as an intermediary reference value. By comparing the amplified first sensing signal with this sum, the system can distinguish between genuine touch events and noise-like electric field interference, even during heavy touch conditions, thereby eliminating the harmful interference effect without requiring threshold adjustment.
Data Source
AI summary
A signal processing method is employed to operate a touch panel having a first touch sensing unit and plural second touch sensing units adjacent to the first touch sensing unit. In the operation of the method, a first signal is generated through amplifying the first sensing signal of the first touch sensing unit by N times with N equal to the number of the second touch sensing units, a second signal is generated through summing up the second sensing signals of the second touch sensing unit, a difference signal is generated through subtracting the second signal from the first signal, a comparison result is generated through comparing the difference signal with a difference threshold, and finally the comparison result is utilized for judging whether a touch event is occurring to the first touch sensing unit.