Capacitive Touch Edge Accuracy via Local Rectangular Array Smoothing
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Solution Overview
Problem
Existing touch-sensitive surfaces face challenges in accurately determining the location of touches near the edge of a sensor array due to insufficient sensor coverage, resulting in poor performance in terms of accuracy and precision.
Innovation Solution
A touch sensing system that includes a two-dimensional capacitive sense array with a capacitance measurement circuit and a processing unit, which applies a smoothing algorithm and edge correction techniques to calculate the x and y coordinates of a touch by summing capacitance values across a local rectangular array and adjusting for edge conditions, thereby improving edge accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional centroid construction methods are used for edge touches, then the method is simple to implement, but the accuracy and precision of touch location determination deteriorates due to insufficient sensor coverage
Solution Approach 1:
The patent divides the touch sensing array into multiple zones (edge zones and non-edge zones) and applies different processing algorithms to each zone. For touches in edge zones, a specialized algorithm using available sensors is applied, while non-edge touches use conventional centroid methods. This segmentation allows improved edge accuracy without unnecessarily complicating the entire system.
Solution Approach 2:
The patent applies different processing approaches based on the local characteristics of the sensing array at different positions. Edge sensors have different coverage properties than center sensors, so the system adapts the touch location calculation method to match the local sensor availability and geometry, optimizing performance for each region.
2Reliability
If a local rectangular array of sensors is used for centroid construction, then the measurement coverage is improved, but the calculation complexity increases due to multiple column sum operations and conditional smoothing
Solution Approach 1:
The patent implements dynamic algorithm selection based on touch location. The system determines whether a touch occurs in an edge zone or non-edge zone and dynamically selects the appropriate processing algorithm. This dynamic approach improves reliability for edge touches while maintaining efficiency for center touches, avoiding unnecessary computational complexity.
Solution Approach 2:
The system uses the measured capacitance data itself to determine the appropriate processing method. By analyzing the pattern of capacitance changes across sensors, the system automatically identifies edge versus non-edge touches and applies the corresponding algorithm, making the complexity management self-directed rather than requiring external control.
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 system enhances the accuracy and precision of touch calculations near the edges of the sensor array by applying smoothing algorithms and edge corrections, effectively addressing the limitations of existing methods.
Implementation Method 1
Capacitive sensing typically involves measuring, through sensor signals (e.g., increases or decreases in electrode responses), a change in capacitance associated with the capacitive sensor elements to determine a presence of a conductive object (e.g., a user's finger or a stylus) relative to the capacitive sensor elements.
Data Source
AI summary
A method is performed at a touch sensing system that includes a two-dimensional capacitive sense array. The process measures the capacitance of the capacitive sensors, and identifies a first sensor whose measured capacitance is a local peak. The local peak is within a local rectangular array. The process computes column sums for each column of the rectangular array and determines whether to apply a smoothing algorithm. When the smoothing algorithm is not applied, the process computes an x-coordinate of a touch using a plurality of the column sums. When applying the smoothing algorithm, the process computes the x-coordinate of the touch as an average of two x-coordinate calculations. Each of the two x-coordinate calculations conditionally performs a horizontal shift of the local rectangular array based on comparing the peak measured capacitance to an adjacent measured capacitance and computes a respective x-coordinate using a respective plurality of the column sums.