Active Stylus Location Prediction for Faster Capacitive Scanning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Touch sensors face a tradeoff between stylus location accuracy and touch scanning frequency, leading to latency issues in interactions with active styluses due to increased scanning durations for accuracy or reduced accuracy with faster scans.
Innovation Solution
Implementing a mechanism to determine a motion vector for an active stylus, allowing the touch sensor to selectively operate based on this vector to predict future stylus locations and focus listening operations in the predicted area, thereby enhancing accuracy and reducing latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the touch sensor increases scanning duration to improve stylus location accuracy, then measurement precision is improved, but productivity deteriorates due to reduced update frequency and increased latency
Solution Approach 1:
The system performs preliminary actions by determining a motion vector for the active stylus and using it to predict future stylus locations. The touch sensor is configured in advance to focus scanning on predicted locations, so when the stylus arrives at the predicted position, the sensor is already prepared to detect it accurately and immediately, eliminating the need for exhaustive full-surface scanning.
Solution Approach 2:
Instead of uniformly scanning the entire touch sensor surface, the system applies local quality by concentrating scanning resources on specific regions predicted to contain the stylus. The touch sensor operates in different modes: full-surface scanning when the stylus is not detected, and focused scanning on predicted locations when the stylus is detected, thereby improving both accuracy and update frequency.
2Measurement precision
If the touch sensor increases scanning duration to improve stylus location accuracy, then measurement precision is improved, but loss of time worsens due to increased latency in interactions
Solution Approach 1:
The system determines motion vectors and predicts stylus locations in advance, configuring the touch sensor beforehand to scan only the predicted regions. This preliminary configuration eliminates the time delay that would otherwise occur during full-surface scanning, allowing immediate detection and response when the stylus reaches the predicted position.
Solution Approach 2:
The scanning strategy dynamically adapts based on stylus motion characteristics. The system transitions from static full-surface scanning to dynamic focused scanning that follows the predicted stylus trajectory, adjusting the scan region in real-time based on motion vector calculations from previous frame data.
3Productivity
If the touch sensor reduces scanning duration to improve productivity, then update frequency is improved, but measurement precision deteriorates
Solution Approach 1:
The system applies local quality by concentrating scanning efforts on specific predicted regions rather than distributing scan time uniformly across the entire surface. This allows the touch sensor to maintain high update frequency through focused scanning while achieving accurate stylus location detection in the regions where the stylus is actually present.
Solution Approach 2:
The system uses feedback from motion vector determination and previous stylus location data to continuously refine scanning strategy. By analyzing stylus motion patterns and updating predictions based on detected position changes, the system ensures that focused scanning remains accurate even as the stylus moves across the surface.
4Loss of time
If the touch sensor reduces scanning duration to reduce loss of time, then interaction latency is reduced, but measurement precision deteriorates
Solution Approach 1:
The system performs preliminary motion vector determination and stylus location prediction before scanning occurs. By pre-configuring the scan region based on predicted stylus position, the system eliminates the time penalty of exhaustive scanning while maintaining accurate detection, thus reducing interaction latency without sacrificing measurement precision.
Solution Approach 2:
The scanning system dynamically adjusts its behavior based on stylus motion characteristics, transitioning between full-surface and focused scanning modes. This dynamic adaptation allows the system to maintain precision during focused scanning by using motion-based predictions while achieving lower latency through reduced scan duration compared to static full-surface scanning.
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
Improves stylus location accuracy and reduces interaction latency by preemptively configuring the touch sensor to receive stylus transmissions in the predicted location, optimizing scanning frequency and power consumption.
Implementation Method 1
The active stylus transmits, in response to a request from the sensor controller, a signal including stylus capability information
Implementation Method 2
A capacitive touch sensor may scan a plurality of electrodes for capacitive influence from a proximate stylus
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Examples are disclosed herein that relate to capacitive touch sensor operation. An example provides a method for operating a display system having a capacitive touch sensor comprising operating the touch sensor over a plurality of successively repeating touch frames, with the touch sensor, determining a motion vector for an active stylus in relation to the touch sensor, and in each of the touch frames, for a stylus-interaction sub-frame of that touch frame allocated for performing electrostatic interaction between an active stylus and the touch sensor, selecting a portion of the touch sensor based on the motion vector. In each of the stylus-interaction sub-frames, the selected portion of the touch sensor may be operated differently than other portions of the touch sensor to carry out the electrostatic interaction.