Touch Sensor Panel Dummy Ground Conductors Noise Filtering
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Solution Overview
Problem
Touch sensor panels face issues with electrical noise from liquid crystal displays (LCDs) causing erroneous signal values and non-uniform spacing of sense elements leading to errors in touch detection, which can result in 'dead zones' and decreased performance.
Innovation Solution
The implementation of reference elements to detect and subtract common noise from sense elements, and the use of dummy ground elements to achieve more uniform spacing between sense elements, thereby correcting signal values and improving touch detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conductive shield is deposited upon the back side of the touch sensor panel to filter out noise from the LCM, then noise filtering is improved, but manufacturing cost and device complexity increase due to deposition and patterning requirements for both sides of the substrate
Solution Approach 1:
The patent extracts the noise filtering function from a full conductive shield and implements it through reference elements that are selectively placed only where needed. Instead of covering the entire back side of the substrate, the reference elements are positioned at specific locations to intercept and neutralize electromagnetic noise from the LCM, thereby reducing manufacturing complexity while maintaining noise filtering effectiveness.
Solution Approach 2:
The patent applies local quality by placing reference elements only at specific locations on the touch sensor panel where noise interference is most problematic, rather than applying a uniform conductive shield across the entire substrate. This localized approach allows noise filtering to be implemented where needed while preserving manufacturing simplicity and reducing overall device complexity.
2Object-affected harmful factors
If reference elements are added to the touch panel layout to filter out noise by subtracting signals, then noise filtering is improved, but the space consumed by reference elements increases pixel sizes or reduces sense element size leading to decreased performance
Solution Approach 1:
The patent applies partial action by using reference elements that are smaller than full sense elements and by not requiring reference elements for every sense element. The reference elements are designed to provide sufficient noise filtering with minimal space occupation, allowing the touch detection performance to be maintained while still achieving effective noise cancellation.
Solution Approach 2:
The patent uses reference elements as simplified copies or representations of sense elements that are specifically designed for noise measurement rather than touch detection. These reference elements replicate the essential function of capturing electromagnetic noise without requiring the full functionality and space of actual sense elements, thereby maintaining measurement precision while reducing space consumption.
3Ease of manufacture
If sense elements are non-uniformly spaced due to asymmetric distribution or common routing requirements, then routing flexibility is improved, but touch detection accuracy decreases due to errors in algorithms that assume uniform spacing
Solution Approach 1:
The patent introduces dummy ground conductors as intermediary elements positioned between non-uniformly spaced sense elements. These dummy grounds act as mediators that compensate for the irregular spacing by providing additional reference points for the touch detection algorithm. The algorithm can then account for the non-uniform spacing by using the dummy grounds as reference markers, thereby maintaining routing flexibility while improving touch region calculation accuracy.
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 and enhances touch detection accuracy by preserving physical space and maintaining touch sensitivity, while minimizing 'dead zones' and improving centroid calculation precision.
Implementation Method 1
Each sense element is separated from an associated set of drive elements by a distance sufficient to enable the sense element to detect when a stimulating voltage has been applied to a particular drive element. When a finger, stylus, or other conductive element is situated proximate to a particular region of the touch sensor panel, a portion of the charge driven by the stimulating voltage escapes via the conductive pathway formed by the finger, stylus, or other conductive element.
Implementation Method 2
The reference elements are spaced far enough from the drive elements so that the capacitive coupling between the reference elements and the drive elements is small or negligible. Signals detected by the reference elements are subtracted from signals detected from associated sense elements in order to filter out the noise common to both elements.
Implementation Method 3
In some devices, for example, a conductive shield is deposited upon the back side of the touch sensor panel. The conductive shield adequately filters out noise generated by the LCM
Data Source
AI summary
Methods and apparatus for correcting electrical noise coupling from a liquid crystal module to a plurality of sense elements disposed within a touch sensor panel, and for reducing errors in touch detection algorithms. Erroneous signal values detected by the sense elements may be corrected by utilizing a set of reference elements for detecting noise common to both the sense elements and the reference elements, and a correction module for effectively subtracting out the noise from the sensed values. Errors in touch detection algorithms may be reduced by providing a more uniform spacing between successive sense elements. In some embodiments, one or more dummy ground elements may be inserted between adjacent sense elements in order to reduce signal interference.