Touch Screen EFT Noise Detection Using Adaptive Thresholds
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Solution Overview
Problem
Touch screen systems are prone to false finger touches due to electrical fast transient (EFT) noise interference, which existing technologies struggle to effectively mitigate, leading to inaccurate touch detection and system noise contamination.
Innovation Solution
A method and apparatus that scan a touch screen panel with sensors arranged in rows and columns, identifying and distinguishing EFT noise influences by using absolute or percentage thresholds to differentiate between genuine touch signals and noise-induced signals, thereby designating frames as noise-influenced and preventing false touch registrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If EFT noise tests are conducted under IEC 61000-4-4 conditions, then the touch screen system can identify noise patterns, but false finger touches are still triggered by EFT noise
Solution Approach 1:
The patent segments the touch screen panel into multiple scanning zones (first corner to second corner diagonally opposite) and analyzes noise patterns in each zone separately. By dividing the panel into regions and evaluating EFT noise impact in each region, the system can identify localized noise patterns without triggering false touches across the entire panel.
Solution Approach 2:
The patent changes the detection parameters by introducing frame-based noise evaluation. Instead of treating each sensor reading independently, the system evaluates the total number of affected sensors across multiple frames and compares against a noise threshold. This parameter change allows the system to distinguish between transient EFT noise and genuine touch events.
2Object-affected harmful factors
If noise thresholds are applied to identify EFT noise, then false touches can be prevented, but genuine touch signals may be missed
Solution Approach 1:
The patent performs preliminary scanning of the touch screen panel from one corner to another before making touch detection decisions. This preliminary action establishes a baseline of normal operation and allows the system to prepare noise evaluation criteria in advance, reducing the risk of misclassifying genuine touches as noise.
Solution Approach 2:
The system implements feedback by continuously monitoring the total number of sensors affected by EFT noise and comparing this against a noise threshold. When the noise level exceeds the threshold, the system adjusts its touch detection behavior accordingly. This feedback mechanism ensures that genuine touches are not mistakenly rejected while maintaining false touch prevention.
Data Source
AI summary
A method comprises during a frame period finding a first EFT noise influenced sensor of a touch screen panel, determining whether the first EFT noise influenced sensor is located at a last transmitting/driving line of the touch screen panel, designating the frame period as a noise influenced frame period using an absolute value threshold if the first EFT noise influenced sensor is not located at the last transmitting/driving line and designating the frame period as the noise influenced frame period using a percentage threshold if the first EFT noise influenced sensor is located at the last transmitting/driving line.