Active Pen Signal Phase Matching for Palm Rejection
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Solution Overview
Problem
Existing palm rejection methods in active pen systems rely on touch detection processes, which fail to accurately distinguish palm contacts from pen inputs, especially when touch is light or narrow, and cannot function in pen-only modes.
Innovation Solution
A sensor controller determines the phase of the downlink signal from an active pen to differentiate between pen tip and palm signals, using a predetermined waveform shared between the pen and controller, allowing palm rejection without requiring touch detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If touch detection is used for palm rejection, then palm contact can be distinguished from pen contact, but the system cannot operate in 'pen only' mode and requires additional detection processes
Solution Approach 1:
The patent extracts the phase information from the downlink signal to create a new discrimination criterion that is independent of touch detection. By using phase matching between the downlink signal and a reference signal, the system can distinguish palm contacts from pen contacts without requiring separate touch detection processes, thus enabling 'pen only' mode operation.
Solution Approach 2:
The patent introduces phase information as an intermediary parameter to bridge the gap between signal detection and palm rejection. The phase of the downlink signal serves as a mediator that carries information about the contact type (palm vs. pen) without requiring direct analysis of touch detection results, allowing the system to operate independently of touch detection processes.
2Measurement precision
If touch detection area is made wide to distinguish palm from finger contact, then palm rejection improves, but light or narrow touch contacts cannot be properly detected
Solution Approach 1:
The patent changes the parameter used for discrimination from touch detection area size to signal phase. Instead of relying on the spatial extent of touch detection (which fails for light or narrow contacts), the system uses the phase of the downlink signal as a new parameter that can reliably distinguish palm contacts from pen contacts regardless of touch area size or pressure level.
Data Source
AI summary
A method of palm rejection is executed by a sensor controller that is connected to a plurality of sensor electrodes and that detects a downlink signal transmitted from an active pen. The method includes determining whether or not a phase of the detected downlink signal matches a phase shared in advance between the sensor controller and the active pen, and outputting, when it is determined that the phases match, a position of the active pen derived on the basis of a distribution of levels of the downlink signal in the plurality of sensor electrodes.