Capacitive sensing multi-pattern scan thick overlays
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Solution Overview
Problem
Capacitance sensing systems face challenges in detecting touch events under thick overlays or through thick gloves due to signal degradation, resulting in low signal-to-noise ratios.
Innovation Solution
The implementation of a multi-pixel scan method, where multiple transmit and receive electrodes are concurrently selected to form larger unit cells, increasing mutual capacitance and sensitivity, thereby enhancing the signal-to-noise ratio and improving touch detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single-pixel scan method is used, then the device complexity is low, but the signal-to-noise ratio is low resulting in poor touch detection sensitivity
Solution Approach 1:
The patent combines multiple transmit electrodes and multiple receive electrodes to form a single virtual pixel unit cell. Instead of scanning individual electrode intersections, the system concurrently activates multiple TX electrodes and multiple RX electrodes together, merging their capacitive signals into a single measurement. This merging approach increases the signal-to-noise ratio by aggregating capacitive coupling from multiple electrode pairs while maintaining relatively simple scan control logic.
2Measurement precision
If multiple transmit and receive electrodes are concurrently selected to form larger unit cells, then the signal-to-noise ratio is improved, but the device complexity increases
Solution Approach 1:
The patent segments the electrode array into groups of transmit electrodes and groups of receive electrodes that can be concurrently activated. The controller divides the scanning process into discrete steps where specific groups of TX and RX electrodes are selected and activated together. This segmentation allows systematic management of multiple electrodes through organized grouping and sequential scanning patterns, reducing the complexity burden of handling individual electrodes separately.
Solution Approach 2:
The system employs periodic scanning patterns where groups of electrodes are activated in repeating cycles. The controller systematically progresses through different electrode groups in a periodic sequence, activating predetermined sets of TX and RX electrodes, measuring their combined capacitance, then moving to the next group. This periodic action provides a structured, predictable scanning rhythm that simplifies control logic while achieving comprehensive coverage of the touch-sensitive surface.
3Measurement precision
If larger unit cells are formed by grouping electrodes, then the mutual capacitance and sensitivity are increased, but the resolution of touch detection may be reduced
Solution Approach 1:
The patent applies segmentation by dividing the electrode array into multiple smaller groups that can be scanned in sequence. Each group forms a virtual pixel with enhanced sensitivity, but by systematically scanning across multiple such groups covering the entire surface, the system reconstructs a high-resolution touch map. The segmentation enables each measurement to be sensitive while the collection of measurements across segments maintains overall spatial resolution.
Solution Approach 2:
The system transitions from measuring individual electrode intersections (2D grid points) to measuring combined capacitance of electrode groups (expanded unit cells). This dimensional change in the measurement unit allows each measurement to capture stronger capacitive signals from multiple interactions, while the systematic arrangement and scanning of these expanded units across the surface preserves spatial information through the pattern of measurements taken across different positions.
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 effectively increases the sensitivity of touch detection systems, allowing for reliable detection of touch events even under thick overlays or through thick gloves by enhancing the signal-to-noise ratio and improving resolution.
Implementation Method 1
Capacitance sensing systems can sense electrical signals generated on electrodes that reflect changes in capacitance. When an object comes into contact with, or is in close proximity to a touch sensor, the capacitance change caused by the object is detected.
Implementation Method 2
multiple transmit and receive electrodes are concurrently selected to form larger unit cells, increasing mutual capacitance and sensitivity
Data Source
AI summary
The sensing circuit includes including first input of a first electrode, a first set of inputs of a first set of two or more electrodes forming a first intersection and a second intersection, and a second set of inputs of a second set of two or more electrodes forming the second intersection and a third intersection. The sensing circuit includes a scan control circuit, coupled to the touch panel of electrodes, to concurrently select the sets of electrodes via a multiplexer. The touch sensing circuit includes an analog front end configured to generate digital values representative of mutual capacitances of a first and second unit cell, wherein the first unit cell comprises the first and second intersections and the second unit cell comprises the second and third intersections, and a channel engine configured to generate capacitance values corresponding to the unit cells.