Touch Detection Device Using Variable Line Capacitance for Noise Reduction
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Solution Overview
Problem
Touch detection devices, particularly in mobile devices, face challenges with signal-to-noise ratio degradation due to noise from wiring lines, especially in electrostatic capacitance type touch panels, which affects the accuracy of detecting touch or proximity events.
Innovation Solution
The implementation of a touch detection device with sensor lines of different lengths and line capacitances, where an operational circuit uses line capacitance ratios to generate detection signals, effectively removing noise components from the detection signal by selecting and processing outputs from neighboring sensor lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple wiring lines are arranged in a matrix shape to determine positional information, then touch detection capability is improved, but signal-to-noise ratio of the detection signal deteriorates due to noise from wiring lines
Solution Approach 1:
The sensor lines are divided into two groups: first sensor lines with first line capacitance and second sensor lines with second line capacitance. This segmentation allows differential processing to separate the touch signal from noise, as the noise affects both groups equally while the touch signal creates a differential response that can be extracted by comparing the groups.
Solution Approach 2:
The invention changes the line capacitance parameter by creating sensor lines with different capacitance values (first line capacitance vs. second line capacitance). This parameter differentiation enables the operational circuit to distinguish between noise (which affects all lines equally) and actual touch signals (which create differential changes), thereby improving signal-to-noise ratio while maintaining touch detection capability.
2Object-affected harmful factors
If sensor lines with different line capacitance are used, then noise removal capability is improved, but device structure becomes more complex
Solution Approach 1:
The invention changes the line capacitance parameter by creating sensor lines with different capacitance values (first line capacitance vs. second line capacitance). This parameter differentiation enables the operational circuit to distinguish between noise (which affects all lines equally) and actual touch signals (which create differential changes), thereby improving signal-to-noise ratio while maintaining touch detection capability.
Solution Approach 2:
The sensor lines with different line capacitances serve multiple functions: they act as both noise sensors and touch detection sensors. By using the same physical structures (sensor lines) for both noise detection and touch signal detection, the invention avoids adding separate dedicated noise cancellation components, thereby limiting the increase in device complexity.
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 signal-to-noise ratio, improving the accuracy of touch detection and reducing noise interference, thereby enhancing the performance of touch detection devices in mobile and display applications.
Implementation Method 1
a plurality of sensor lines which are formed from a plurality of types of wiring lines having a different line capacitance
Implementation Method 2
an operational circuit which generates a detection signal representing the electric variation by performing an operation process using a line capacitance ratio for a plurality of outputs from a plurality of types of the sensor lines
Data Source
AI summary
A touch detection device includes: a detection surface; a plurality of sensor lines formed from a plurality of types of wiring lines having a different line capacitance; and a touch detection unit which detects an electric variation generated in a plurality of the sensor lines in response to touch or proximity of a detection target object to the detection surface, wherein the touch detection unit has an operational circuit for generating a detection signal representing the electric variation by performing an operation process using a line capacitance ratio for a plurality of outputs from a plurality of types of the sensor lines neighboring to one another with a different line capacitance.