Mitigating Active Stylus Cross-Coupling via Compensation Factors
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Solution Overview
Problem
Active styluses in capacitive touch systems experience cross-coupling errors when used simultaneously with touch inputs, leading to inaccurate stylus position detection due to constructive/destructive interference between the stylus drive signal and the touch-induced signal.
Innovation Solution
A method to mitigate cross-coupling by determining potentially corrupted sense lines, applying a trained compensation factor to correct sense signals, and determining the stylus location based on these corrected signals, which involves training during the LCD module blanking interval and using compensation factors calculated in the I/Q domain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an active stylus is used as a drive electrode to create an oscillating electric field for stylus sensing, then stylus position detection capability is improved, but cross-coupling errors occur when used simultaneously with touch inputs, resulting in inaccurate stylus position detection
Solution Approach 1:
The system performs preliminary training during LCD module blanking intervals to calculate compensation factors. These factors are pre-computed based on touch image information and stored for later use during normal operation, allowing the system to prepare correction data in advance without interfering with real-time stylus positioning
Solution Approach 2:
The system uses feedback from touch image information to adjust and correct stylus position detection. By continuously monitoring touch events and comparing them with stylus detection signals, the system calculates compensation factors that feedback-correct the stylus position measurements to eliminate cross-coupling errors
2Productivity
If the stylus drive signal is transmitted through sense lines for position detection, then stylus tracking is enabled, but constructive/destructive interference occurs between stylus drive signal and touch-induced signal, causing position errors
Solution Approach 1:
The system introduces compensation factors as intermediary correction values that mediate between the raw stylus detection signal and the final position calculation. These factors act as a corrective intermediary that eliminates the harmful interference effects without disrupting the primary signal transmission path
Solution Approach 2:
The system changes the parameters of the detection signal by applying compensation factors to adjust the amplitude and phase characteristics. This parameter modification transforms the corrupted signal into a corrected signal that accurately represents the stylus position without interference from touch inputs
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
The method effectively reduces errors in stylus position detection, ensuring accurate tracking of stylus movements even when used in conjunction with touch inputs, as illustrated by improved drawing precision in exemplary results.
Implementation Method 1
touch locations can be identified through changes in the stimulation signal. Typically, a touch location is sensed based on an interference of the stimulation signal
Implementation Method 2
a stylus has traditionally been finger-like in nature. A conventional stylus is often simply a conductive rod with a finger-sized rounded tip large enough to disrupt the electric field lines between the drive and sense electrodes
Implementation Method 3
If the active stylus is a drive-type active stylus, it operates to create an oscillating electric field that is sensed by the sense lines of the capacitive touch sensor panel
Implementation Method 4
applying a trained best compensation factor to the measured sense signal on each sense line that has been determined to be potentially corrupted to produce a corrected sense signal
Data Source
AI summary
In one aspect, the present disclosure relates to a method including determining which sense lines are potentially corrupted based on touch image information, measuring a sense signal on each sense line, and applying a trained best compensation factor to the measured sense signal on potentially corrupted sense lines in order to produce a corrected sense signal. The corrected sense signal eliminates active stylus signal that has cross-coupled to a touch contact (e.g., a finger or conductive stylus) and thereby mitigates errors in stylus location due to cross-coupled signal.