Active Pen Profile Correction for Touch Interference

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The presence of a finger or palm on a capacitive sensing device interferes with the accurate detection of an active pen, causing degradation of input performance.

Innovation Solution

A method and system that adjust the active pen profile using a capacitive touch profile to obtain a corrected active pen profile, enabling precise pen detection by correcting for touch interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If capacitive sensing is used to detect active pen input, then the sensing device can provide touch input capability, but the presence of a finger or palm causes touch interference that degrades active pen detection accuracy

Engineering Contradiction:

Improvetouch input capabilityVSAvoidactive pen detection accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent segments the sensed input into separate components by identifying and isolating the capacitive profile characteristics of the active pen from those of the finger or palm. The processing system separates the active pen signal from the touch interference signal by analyzing capacitive coupling patterns specific to each input type, allowing independent detection and processing of each component.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary processing layer that acts as a mediator between the raw capacitive sensor data and the final input interpretation. This processing system uses intermediate representations (capacitive profiles) to characterize different input types and employs intermediate calculations to subtract or filter out the touch interference component before determining the final active pen position.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If multiple input objects are simultaneously detected, then the device supports multiple input modes, but touch interference from finger or palm degrades the active pen input quality

Engineering Contradiction:

Improvemultiple input objects detectionVSAvoidactive pen input quality

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent implements dynamic adjustment of detection parameters based on the detected input configuration. The processing system continuously monitors capacitive profiles and dynamically adapts its analysis method to distinguish between active pen and finger/palm inputs. When both input types are detected, the system dynamically adjusts the separation algorithm to maintain reliable active pen detection despite the presence of touch interference.

Inventive Principle:

Principle #15Dynamics

3Measurement precision

If capacitive touch profile adjustment is applied to correct active pen profile, then accurate pen position detection is achieved, but additional processing complexity is introduced

Engineering Contradiction:

Improvepen position detection accuracyVSAvoidprocessing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent performs preliminary characterization of the touch interference by obtaining a capacitive touch profile before processing the active pen detection. This pre-processing step captures the interference pattern in advance, allowing the subsequent active pen profile correction to work with a known reference rather than attempting to filter interference in real-time, thereby reducing overall processing complexity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the parameter representation of the active pen profile by adjusting it based on the capacitive touch profile. Instead of directly processing raw sensor data, the system transforms the active pen profile parameters by subtracting or compensating for the touch interference parameters, thereby simplifying the detection algorithm while improving accuracy.

Inventive Principle:

Principle #35Parameter changes

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

Enables accurate and smooth detection of an active pen's position even when a finger or palm is present, reducing jagged line artifacts and ensuring reliable input performance.

Implementation Method 1

Proximity sensor devices utilize one or more electrical techniques, such as a capacitive sensing technique, to determine the presence, location and/or motion of an input object

Methodology Applied

Scientific EffectCapacitive sensing: Capacitance

Implementation Method 2

The presence of the finger or palm may cause touch interference, resulting in a degradation of the input provided by the active pen

Methodology Applied

Scientific EffectCapacitive coupling: Parasitic Capacitance

Data Source

PatentUS12474803B2Correcting touch interference for active pen

Publication Date: 2025.11.18 SYNAPTICS INC

AI summary

A method of capacitive sensing includes obtaining a capacitive touch profile from multiple receiver electrodes disposed in a sensing region of an input device and obtaining an active pen profile, different from the capacitive touch profile, from the multiple receiver electrodes. The method also includes adjusting, using the capacitive touch profile, the active pen profile to obtain a corrected active pen profile and determining a position of an active pen in the sensing region, using the corrected active pen profile.