Variable Frequency Touch Detection Reducing LCD Noise Interference
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Solution Overview
Problem
Current touch detection methods, particularly capacitive touch screens, face challenges in accurately detecting multi-touch inputs due to noise interference from sources like LCD displays and environmental factors, leading to errors in touch coordinate detection and increased power consumption during signal processing.
Innovation Solution
A touch detection method and apparatus that utilize a variable frequency signal applied to driving electrodes, allowing sensing electrodes to modulate and demodulate touch signals, and accumulate these signals to reduce noise effects, enabling accurate multi-touch detection with reduced power consumption and noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitance method is used for touch detection, then multi-touch detection capability and durability are improved, but noise interference from LCD displays and environmental factors causes errors in touch coordinate detection
Solution Approach 1:
The patent applies parameter changes by varying the driving signal frequency dynamically. The frequency is changed based on detected touch conditions and environmental noise levels, allowing the system to distinguish between valid touch signals and noise interference. This frequency modulation approach enables the touch detection system to maintain accuracy despite the presence of noise from LCD displays and environmental factors.
2Measurement precision
If signal processing operations such as noise filtering and demodulation are performed, then touch coordinate accuracy is improved, but power consumption increases
Solution Approach 1:
The patent implements periodic action by performing signal processing operations in periodic cycles rather than continuously. The system alternates between signal acquisition phases and processing phases, where noise filtering and demodulation are performed only when necessary. This periodic processing reduces overall power consumption while maintaining touch coordinate accuracy through efficient signal handling.
3Reliability
If multiple frequency signals are used to drive the touch panel, then noise rejection capability is improved, but device complexity increases
Solution Approach 1:
The patent applies dynamics by using a single variable frequency signal that adapts its frequency based on detected conditions, rather than employing multiple fixed frequency signals simultaneously. The frequency is dynamically adjusted according to touch detection results and environmental noise characteristics. This dynamic approach achieves noise rejection capability while reducing device complexity compared to using multiple independent signal sources.
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 effectively reduces noise interference, especially from frequencies adjacent to the driving signal, allowing for precise touch coordinate detection with reduced power consumption and improved stability in multi-touch input recognition.
Implementation Method 1
A touch screen of the capacitance method recognizes a user input by detecting changes in an electric charge amount that is charged into capacitive sensors on a touch screen panel by user interference
Implementation Method 2
When a user approaches the sensor, interference with respect to an electric field formed between the two electrodes occurs to prevent electric charge from being stored in the sensor
Data Source
AI summary
Disclosed are an apparatus for detecting touch and a method for detecting touch with reduced effect of noise. The apparatus includes a signal source configured to generate a variable frequency signal changed from a starting frequency to an ending frequency, a touch panel including a plurality of driving electrodes and a plurality of sensing electrodes, wherein the variable phase signal is applied to one of the plurality of driving electrodes, and the sensing electrode outputs a touch signal that is modulated by the variable frequency signal, a demodulation unit configured to demodulate the touch signal using the variable frequency signal, and an accumulation unit configured to accumulate the demodulated touch signal to detect the touch.