Hover Position Calculation in Capacitive Touchscreen Devices
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Solution Overview
Problem
Current touchscreen technologies face challenges in accurately calculating the position of a conductive object hovering above a capacitive touch surface, particularly due to noise and edge zone inaccuracies, which affect the precision of hover detection and position calculation.
Innovation Solution
A method is disclosed that involves measuring capacitance on a plurality of mutual capacitance sensors, identifying a peak unit cell, calculating an edge cutoff value, and selecting unit cells within a defined range to determine the position of a hovering conductive object, using a controller configured to process capacitance data and apply correction factors for edge zone detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitance measurement is performed on all unit cells in the array, then complete coverage of the sensing area is achieved, but noise and edge zone inaccuracies increase
Solution Approach 1:
The patent segments the unit cells into different groups based on their distance from the peak unit cell. Unit cells within a calculated distance (determined by the edge cutoff value) are selected for position calculation, while those beyond this distance are excluded. This segmentation reduces the influence of noisy edge zone measurements while maintaining accuracy for relevant cells.
Solution Approach 2:
The patent applies different selection criteria to different regions of the unit cell array. Unit cells near the peak (within the cutoff distance) are included in position calculations with full weight, while unit cells at the edges or far from the peak are excluded. This local quality approach ensures that measurements from reliable regions contribute to the calculation while noisy regions are filtered out.
2Area of stationary object
If edge zone unit cells are included in position calculation, then sensing coverage is maximized, but position accuracy deteriorates due to edge effects
Solution Approach 1:
The patent extracts and excludes unit cells from the edge zones that would introduce inaccuracies into the position calculation. By calculating a distance threshold from the peak unit cell and excluding cells beyond this threshold, the method removes the harmful edge zone contributions while retaining the beneficial coverage from valid unit cells within the threshold.
3Ease of operation
If a fixed threshold is used for unit cell selection, then processing simplicity is maintained, but adaptability to different hover positions is reduced
Solution Approach 1:
The patent implements a dynamic threshold mechanism where the selection distance cutoff is calculated based on the specific hover position detected (the peak unit cell location). Rather than using a fixed threshold, the system adapts the cutoff distance to the current peak position, allowing the selection window to move and resize dynamically as the hover position changes across the sensing array.
Solution Approach 2:
The patent changes the parameter of the selection threshold from a fixed value to a dynamic value that depends on the peak unit cell position. The cutoff distance is recalculated for each hover detection event based on the detected peak location, enabling the system to adapt to different positions while maintaining a consistent methodology for selecting relevant unit cells.
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 accuracy of hover position calculation and reduces noise-related errors, improving the reliability of hover detection and user interaction recognition on capacitive touchscreens.
Implementation Method 1
Capacitance sensing systems can sense electrical signals generated on electrodes that reflect changes in capacitance. Such changes in capacitance can indicate a touch event (e.g., the proximity of an object to particular electrodes).
Data Source
AI summary
A method calculates the position of a conductive object hovering above a plurality of mutual capacitance sensors, where each mutual capacitance sensor is represented as a unit cell in an array of unit cells. The method measures the capacitance of each sensor. The method identifies a peak unit cell based on the measured capacitances and calculates an edge cutoff value. A plurality of unit cells with measured capacitances within a range defined by the edge cutoff value are selected and the position of the hovering object is calculated. In some embodiments, the array comprises a first plurality of capacitance sensing electrodes disposed along a first axis and a second plurality of capacitance sensing electrodes disposed along a second axis. In some embodiments, the array and a controller form a user interface device, and the controller is configured to calculate the position of the conductive object using the method described above.