AC Ground Shield for Touch and Hover Sensing
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Solution Overview
Problem
Current capacitive touch and hover sensing technologies face limitations in hover detection range and efficiency, making it difficult to accurately detect objects near but not touching the touch surface, especially outside the direct area above the sensor array.
Innovation Solution
The implementation of an AC ground shield positioned behind the capacitive touch sensor array, stimulated with alternating current signals, enhances hover sensing by concentrating the electric field and improving detection capabilities, including the ability to determine hover positions outside the direct touch area by fitting sensor measurements to models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hover detection is performed using conventional capacitive sensor arrays, then hover events can be detected, but the hover detection range is limited and detection efficiency is poor
Solution Approach 1:
The patent extends hover detection beyond the direct area above the sensor array by detecting hover events in border areas and external regions. The system uses model-based fitting of sensor measurements to determine hover positions that may lie outside the physical sensor array boundaries, effectively expanding the detection space from 2D sensor surface to 3D space including external regions.
Solution Approach 2:
The patent introduces an AC ground shield as an intermediary component positioned behind the sensor array. This shield is driven with AC signals to generate an electric field that concentrates and extends the sensing field into the border areas and external regions, enabling detection beyond the direct sensor coverage area.
2Volume of stationary object
If the electric field extends behind the sensor array to cover internal spaces, then the sensing volume increases, but the electric field disperses and hover sensing capability decreases
Solution Approach 1:
The AC ground shield is positioned specifically behind the sensor array to create a localized electric field concentration in the border areas and external regions where hover detection is needed. The shield is driven with AC signals that are synchronized with the sensor array drive signals, creating a focused sensing field in the critical detection zones while maintaining the extended sensing volume.
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 solution significantly enhances hover sensing capabilities, allowing for more accurate detection of objects near the touch surface, even outside the direct detection area, and improves the joint operation of touch and hover sensing, enabling better user interaction with touch screens and other devices.
Implementation Method 1
An AC ground shield may be used to enhance the hover sensing capability of the sensor array. The AC ground shield can be positioned behind the sensor array and can be stimulated with signals having the same waveform as the signals driving the sensor array. As a result, the electric field extending outward from the sensor array can be concentrated.
Data Source
AI summary
Improved capacitive touch and hover sensing with a sensor array is provided. An AC ground shield positioned behind the sensor array and stimulated with signals of the same waveform as the signals driving the sensor array may concentrate the electric field extending from the sensor array and enhance hover sensing capability. The hover position and/or height of an object that is nearby, but not directly above, a touch surface of the sensor array, e.g., in the border area at the end of a touch screen, may be determined using capacitive measurements of sensors near the end of the sensor array by fitting the measurements to a model. Other improvements relate to the joint operation of touch and hover sensing, such as determining when and how to perform touch sensing, hover sensing, both touch and hover sensing, or neither.