Capacitive Touch Sensor Non-Uniform Cover Thickness
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Solution Overview
Problem
Capacitive touch sensors embedded behind insulating covers of varying thickness face challenges in maintaining consistent sensitivity and signal-to-noise ratio (SNR) due to thickness variations, leading to inaccurate touch position detection and increased noise in high electrical noise environments.
Innovation Solution
A two-dimensional capacitive sensor design with varying edge lengths of receiver electrodes at sensing nodes to compensate for thickness variations, ensuring consistent sensitivity and SNR across the sensor area, achieved by increasing edge lengths where the cover is thicker and reducing them where it is thinner, while maintaining constant overlap areas to balance capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the sensor uses a uniform electrode pattern, then the manufacturing is simple, but the sensitivity varies across the sensor area due to thickness variations
Solution Approach 1:
The patent applies local quality by varying the edge lengths of receiver electrodes at different sensing nodes according to the local thickness of the insulating cover. Nodes under thicker regions have longer edge lengths to compensate for reduced capacitance coupling, while nodes under thinner regions have shorter edge lengths. This localized adaptation ensures uniform sensitivity across the entire sensor area despite thickness variations.
Solution Approach 2:
The patent changes the geometric parameters of the electrode pattern, specifically the edge lengths of receiver electrodes, to compensate for thickness variations. By adjusting these parameters based on the local thickness profile, the patent maintains consistent sensitivity and signal-to-noise ratio across different regions of the sensor.
2Measurement precision
If the edge lengths are increased to compensate for thicker regions, then the sensitivity is improved in those regions, but the overlap areas increase causing capacitance imbalance
Solution Approach 1:
The patent applies local quality by selectively adjusting only the edge lengths of receiver electrodes while keeping the overlap areas constant. This localized modification allows sensitivity compensation in thicker regions without disrupting the overall capacitance balance, as the constant overlap areas ensure that the capacitive coupling remains uniform across all sensing nodes.
Solution Approach 2:
The patent segments the electrode pattern into transmitter electrodes and receiver electrodes with distinct functional roles. By varying only the edge lengths of receiver electrodes and maintaining constant overlap areas, the patent independently controls sensitivity and capacitance balance, allowing optimization of one parameter without compromising the other.
3Adaptability or versatility
If the sensor operates behind a non-uniform cover, then the design flexibility is improved, but the signal-to-noise ratio varies across the sensor area
Solution Approach 1:
The patent changes the geometric parameters of receiver electrodes to adapt to varying insulating cover thickness. By adjusting edge lengths according to the local thickness profile, the patent maintains consistent signal-to-noise ratio across the sensor area, enabling reliable operation behind non-uniform covers while preserving design flexibility.
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 design provides uniform touch sensitivity and improved SNR across the sensor area, reducing noise and enhancing accurate touch position detection even in environments with varying cover thickness and high electrical noise.
Implementation Method 1
a two-dimensional capacitive sensor of the mutual-capacitance type comprising a cover panel of varying thickness and an electrode panel arranged under the cover panel, the electrode panel comprising a plurality of transmitter electrodes extending in a first direction and a plurality of receiver electrodes extending in a second direction, wherein an array of sensing nodes is formed between edge portions of the receiver electrodes and adjacent portions of the transmitter electrodes
Implementation Method 2
the length of the edge portions per sensing node is varied with the thickness of the cover panel so that the edge portion length per sensing node increases as the thickness increases, so as to provide part or substantially complete compensation for variation in node sensitivity across the sensor
Data Source
AI summary
A two-dimensional capacitive touch sensor having a cover layer of varying thickness arranged on top of its electrode structure. An array of sensing nodes is formed between edge portions of the receiver electrodes and adjacent portions of the transmitter electrodes. To compensate for the varying thickness of the cover layer, the length of the edge portions per sensing node is varied to equalize node sensitivity across the sensor and thus suppress the systematic variation in node sensitivity which would otherwise arise as a result of the varying thickness of the cover layer.