OLED Touch Screen Scanning for Zebra Noise and Ghost Touches
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Solution Overview
Problem
Conventional touchscreen displays using organic light emitting diodes (OLEDs) suffer from zebra noise, which causes ghost touches due to high background noise and the inability to accurately detect touch frequencies, especially when zebra patterns are present, leading to false touch detections.
Innovation Solution
Simultaneously performing mutual and noise sampling scans on different portions of the touchscreen, adjusting the frequency threshold based on real-time noise profiles to minimize noise interference, and dynamically adapting to changing noise environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional touchscreen displays use OLED technology with sequential row updates, then display performance and refresh rate are improved, but zebra noise and ghost touches occur due to high background noise
Solution Approach 1:
The touchscreen is divided into multiple portions (first portion and second portion), with different scanning methods applied to each. The first portion uses mutual sampling scan for touch detection, while the second portion uses noise sampling scan for noise characterization. This segmentation allows simultaneous optimization of both touch detection accuracy and noise reduction without compromising refresh rate.
Solution Approach 2:
The system dynamically adjusts the predetermined frequency value based on real-time noise detection. When noise values exceed the threshold, the frequency is adjusted to minimize noise interference. This dynamic adaptation allows the system to maintain high refresh rate while compensating for zebra noise conditions, preventing ghost touches.
2Measurement precision
If noise sampling scan is performed on the entire touchscreen, then noise detection accuracy is improved, but scanning time increases
Solution Approach 1:
The touchscreen is segmented into a first portion (for mutual sampling) and a second portion (for noise sampling). By restricting noise sampling to only the second portion, the system achieves accurate noise detection for zebra noise characterization while reducing the overall scanning time compared to sampling the entire display.
Solution Approach 2:
Instead of performing noise sampling on the entire touchscreen (excessive action), the system applies noise sampling only to the second portion where zebra noise is detected (partial action). This partial approach provides sufficient noise characterization to prevent ghost touches while minimizing time consumption.
3Device complexity
If frequency threshold is fixed, then system complexity is reduced, but ability to adapt to changing noise environments is lost
Solution Approach 1:
The frequency threshold is transformed from a fixed value to a dynamic parameter that adjusts based on real-time noise detection. The touch controller continuously monitors noise values from the second portion and modifies the predetermined frequency value accordingly. This dynamic adjustment enables adaptation to changing noise environments while maintaining manageable system complexity through automated control.
Solution Approach 2:
The system implements feedback by comparing detected noise values to the predetermined frequency value and adjusting the frequency threshold accordingly. When noise values exceed the threshold, the frequency is adjusted to minimize noise interference. This feedback mechanism enables the system to adapt to varying noise conditions automatically, enhancing versatility without requiring complex manual configuration.
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
Prevents ghost touches by accurately detecting touch events, enhancing multi-touch accuracy, and ensuring consistent performance across varying noise levels, even in environments with high electromagnetic interference.
Implementation Method 1
Each pixel may include an OLED configured to generate light based on the current driven through it. During operation the touchscreen may be refreshed (e.g., updated) in each of a plurality of display frames defined by a vertical synchronization signal (Vsync).
Implementation Method 2
OLED display provide a high contrast self-illuminating display with a low driving voltage and high luminous efficiency. Each pixel may include an OLED configured to generate light based on the current driven through it.
Data Source
AI summary
A method for operating an electronic device comprising simultaneously performing a mutual sampling scan on a first portion of a touchscreen and performing a noise sampling scan on a second portion of the touchscreen that is larger than the first portion, detecting noise values from the second portion of the touchscreen, comparing the noise values to a predetermined frequency value of a touch controller, and adjusting the predetermined frequency value when at least one of the noise values exceed the predetermined frequency value.