Sinuous Interdigitated Touchscreen Electrodes for Moiré Reduction
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Solution Overview
Problem
Current capacitive sensing technologies for touchscreens face challenges in distinguishing between multiple touches, absorbing excessive light, and maintaining a small footprint, especially when used with LCD displays, leading to issues like Moiré patterns and increased volume.
Innovation Solution
A mutual capacitance touchscreen design featuring interdigitated electrically conductive traces arranged at angles with sinuous boundaries, reducing the need for additional layers and minimizing optical interference, while maintaining sensitivity to small touch objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a mutual capacitance grid arrangement with crossed electrodes is used, then multi-touch measurement accuracy is improved, but light absorption increases and display brightness decreases
Solution Approach 1:
The touchscreen is divided into multiple sensing zones defined by the intersecting trace patterns. Each intersection point represents a discrete sensing location, allowing the system to segment the measurement area into distinct regions that can be independently measured, thereby enabling accurate multi-touch detection without requiring a dense grid of electrodes across the entire surface.
Solution Approach 2:
The patent transitions from traditional orthogonal grid patterns to angled trace arrangements where the second set of traces intersects the first set at non-90-degree angles. This dimensional change in the trace geometry reduces the visual impact on the display while maintaining the capacitive sensing function, thereby improving brightness without sacrificing measurement precision.
2Reliability
If stacked layers of ITO are used for electrode rows and columns, then capacitive sensing functionality is achieved, but device thickness increases
Solution Approach 1:
The patent combines the drive and sense electrode functions into a single integrated trace structure. The first set of conductive traces serves as drive electrodes while the second set serves as sense electrodes, and their intersections define the sensing points. This merging eliminates the need for separate stacked ITO layers for different electrode types, thereby reducing overall device thickness while maintaining full capacitive sensing functionality.
3Ease of manufacture
If orthogonal grid patterns are used for touchscreen electrodes, then manufacturing is simplified, but Moiré patterns appear when overlaid on LCD displays
Solution Approach 1:
The patent employs asymmetric trace arrangements where the second set of conductive traces intersects the first set at angles other than 90 degrees. This asymmetric geometry disrupts the regular periodic pattern that causes Moiré interference when overlaid on LCD pixel grids, while still maintaining sufficient structural regularity for straightforward manufacturing processes.
Solution Approach 2:
The patent utilizes curved or sinusoidal trace paths instead of straight linear segments. These curved trajectories eliminate the sharp angles and straight lines that create Moiré patterns when overlaid on rectangular LCD pixels, while the continuous curved geometry remains compatible with standard photolithographic fabrication methods.
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
The design effectively distinguishes multiple touches, reduces light absorption, and minimizes optical interference, resulting in a thinner, more sensitive, and brighter touchscreen solution.
Implementation Method 1
mutual capacitance measurement, where measurements are performed using a crossed grid of electrodes
Implementation Method 2
some of the electric field lines emanating from or near the grid point are deflected, thereby decreasing the mutual capacitance of the two electrodes at the grid point
Data Source
AI summary
According to one embodiment, there is provided a mutual capacitance touchscreen comprising a first set of electrically conductive traces arranged in rows or columns and a second set of electrically conductive traces arranged in rows or columns arranged at right angles with respect to the rows or columns of the first set, where the first and second sets of traces are electrically insulated from and interdigitated respecting one another, and gaps between the first and second sets of traces form boundaries between the first and second sets of traces that undulate and that are not straight or linear. Other embodiments of a mutual capacitance touchscreen are also disclosed, such as “mini-diamond” sensor array patterns and sensor array patterns that may be manufactured at low cost.