Touch Sensor Electrode Polarity Inversion for Stylus Detection
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Solution Overview
Problem
Capacitive touch sensors face challenges in accurately detecting the proximity of a stylus due to inverted signal polarities caused by external events, such as a user's palm, which can incorrectly identify the stylus position.
Innovation Solution
The touch sensor controller applies an inverted drive signal to the electrodes when an inverted polarity is sensed, ensuring that signals from a stylus are not ruled out as non-proximity candidates, and returns to a non-inverted drive signal when the causing event is removed, allowing for accurate detection of stylus proximity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a non-inverted drive signal is applied to the touch sensor electrodes, then the system can detect normal capacitive changes, but external events like palm contact cause inverted signal polarities that lead to false stylus position identification
Solution Approach 1:
The system dynamically adjusts the drive signal polarity based on detected signal conditions. When an inverted polarity is detected (indicating palm or other external contact), the system switches to applying an inverted drive signal to compensate. This dynamic adaptation allows the system to maintain reliable stylus detection under varying contact conditions without increasing false positives.
Solution Approach 2:
The system changes the polarity parameter of the drive signal in response to detected inverted capacitance changes. By inverting the drive signal polarity when palm contact is detected, the system compensates for the inverted response and restores accurate stylus position measurement, thereby maintaining measurement precision while reducing false positives.
2Measurement precision
If the system applies an inverted drive signal to compensate for external interference, then stylus detection accuracy improves, but the system complexity increases due to additional signal inversion logic
Solution Approach 1:
The system uses feedback from the sensed capacitance changes to control the drive signal polarity. The controller monitors the polarity of capacitance changes and automatically adjusts the drive signal accordingly - applying inverted drive signals when inverted changes are detected. This feedback mechanism maintains high detection accuracy while keeping the control logic relatively simple and systematic.
Solution Approach 2:
The system self-adjusts by automatically detecting inverted polarities and switching to inverted drive signals without external intervention. This self-service capability allows the system to maintain accurate stylus detection under various conditions while minimizing the need for complex external control logic or manual adjustment mechanisms.
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 method effectively differentiates stylus proximity from external interference, enhancing the accuracy of stylus detection and preventing false positives, thereby improving user interaction with touch-sensitive devices.
Implementation Method 1
a change in capacitance may occur within the touch screen at a position of the touch sensor of the touch screen that corresponds to the position of the object within the touch sensitive area of the touch sensor
Data Source
AI summary
In one embodiment, a controller includes a processor and a memory, the memory storing logic. The logic is configured to perform, when executed by the processor, operations including detecting, in response to driving a plurality of electrodes of a touch sensor with a first drive signal having a first polarity, a first sense signal. The first sense signal has a second polarity, the second polarity being an inverse of the first polarity. The logic is further configured to perform operations including driving, in response to detecting the first sense signal, the plurality of electrodes with a second drive signal having the second polarity.