Hover Detection on Touch Sensor Panels Using Offset Signals
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Solution Overview
Problem
Touch sensor panels operating in mutual capacitance mode face challenges in detecting proximity events, such as hover, due to small changes in capacitance caused by objects interacting with the electromagnetic fields, which can be difficult to accurately sense.
Innovation Solution
The implementation of a touch sensor panel arranged in rows and columns of touch electrodes, where multiple rows and columns are driven simultaneously to increase electromagnetic field penetration, and an offset signal is injected into touch sensing circuits to offset baseline capacitance, improving detection sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple rows and columns are driven simultaneously to increase electromagnetic field penetration, then detection sensitivity for proximity events is improved, but device complexity and power consumption increase
Solution Approach 1:
The touch sensor panel is divided into multiple rows and columns of touch electrodes that can be independently driven. By segmenting the electrode structure into a matrix arrangement, the system can selectively activate specific rows and columns to create electromagnetic fields at targeted locations, improving proximity detection sensitivity without requiring all electrodes to be driven simultaneously.
Solution Approach 2:
Instead of driving all rows and columns simultaneously, the system drives only the necessary subset of electrodes required for detecting proximity events in specific regions. This partial action approach maintains high detection sensitivity where needed while reducing overall device complexity and power consumption compared to full-panel activation.
2Measurement precision
If multiple rows and columns are driven simultaneously to increase electromagnetic field penetration, then signal-to-noise ratio is improved, but power consumption increases
Solution Approach 1:
The system activates only the minimum necessary number of electrode rows and columns to achieve adequate signal-to-noise ratio for proximity detection. By driving electrodes in a scanned or selective manner rather than simultaneously across the entire panel, the system maintains detection sensitivity while significantly reducing power consumption.
Solution Approach 2:
The touch sensing system employs periodic scanning of electrode rows and columns rather than continuous simultaneous activation. Electromagnetic fields are generated in successive time periods across different electrode groups, maintaining detection capability while allowing power consumption to be distributed over time and reduced during non-activation intervals.
3Measurement precision
If an offset signal is injected into touch sensing circuits to offset baseline capacitance, then detection sensitivity is improved, but circuit complexity increases
Solution Approach 1:
An offset signal is introduced as an intermediary element in the touch sensing circuit to compensate for baseline capacitance. This offset signal acts as a mediator that cancels out the unwanted baseline capacitance component, allowing the sensing circuit to more accurately detect small changes in capacitance caused by proximity events without requiring complete circuit redesign.
Solution Approach 2:
The system dynamically adjusts the offset signal parameter to match and counteract the baseline capacitance level. By changing the offset signal parameter (amplitude, phase, or timing) based on measured baseline conditions, the system improves detection sensitivity while using a flexible, adjustable approach rather than fixed complex circuitry.
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 ability to detect proximity events by increasing the signal-to-noise ratio and improving the sensitivity of touch and hover activity detection, allowing for more accurate recognition of objects approaching or contacting the touch sensor panel.
Implementation Method 1
multiple rows and columns can be driven simultaneously (optionally with the same drive signal) to increase the field penetration of the generated electromagnetic fields
Implementation Method 2
In some examples, the sensed change in capacitance due to the object's interaction with the touch sensor panel can be small relative to the overall capacitance formed by the intersection of the touch electrodes. In some examples, an offset signal can be injected into touch sensing circuits to offset baseline capacitance.
Data Source
AI summary
Some touch screens can be formed with rows and columns of touch electrodes. In some examples, during a first time period, a first set of row electrodes are driven while a second set of row electrodes are sensed. In some examples, during a second time period, the first set of row electrodes are sensed while the second set of row electrodes are driven. In some examples, during a third time period, a first set of column electrodes are driven while a second set of column electrodes are sensed. In some examples, during a fourth time period, the first set of column electrodes are sensed while the second set of column electrodes are driven. In some examples, a touch image can be generated based on the data sensed from the first, second, third, and fourth time periods.