Active Stylus Signal Identification for Capacitive Touch Panels

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional capacitive touch panels struggle to allow simultaneous operation of active styluses and fingers due to differing sensing methods and protocols, resulting in the touch sensing circuit stopping finger detection when an active stylus approaches, preventing simultaneous use.

Innovation Solution

An active stylus signal identification method that involves the active stylus emitting signals in specific periods, allowing the touch sensing circuit to perform segmented scanning during spare periods without active stylus signals, enabling the capacitive touch panel to be operated by both the stylus and finger simultaneously by integrating sensing results from these segments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the touch sensing circuit stops finger touch sensing when an active stylus approaches the touch panel, then the active stylus signal can be detected accurately, but the finger touch sensing is interrupted and cannot operate simultaneously

Engineering Contradiction:

Improveactive stylus signal detection accuracyVSAvoidsimultaneous operation capability

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The touch sensing circuit divides the detection process into segments: during active stylus signal periods, stylus detection is performed; during idle periods between stylus signals, finger touch sensing is conducted. This segmentation allows both stylus and finger operations to be detected in different time windows without mutual interference

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The active stylus emits signals periodically according to a protocol, creating regular idle periods between signals. The touch sensing circuit utilizes these periodic idle periods to perform finger touch sensing, thereby enabling simultaneous operation capability while maintaining stylus detection accuracy

Inventive Principle:

Principle #19Periodic action

2Loss of information

If the touch sensing circuit scans the entire display region during idle periods, then complete finger touch information is obtained, but the scanning time may exceed the available idle period duration

Engineering Contradiction:

Improvefinger touch information completenessVSAvoidscanning time

Core Design Contradiction:

Loss of informationVSLoss of time

Solution Approach 1:

The display region scanning is divided into multiple segments corresponding to different idle periods. Each idle period scans a portion of the display region, and the results are integrated across multiple idle periods to achieve complete finger touch information without requiring the entire scan to complete within a single idle period

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The touch sensing circuit performs partial scanning during each idle period and continues scanning in subsequent idle periods. This preliminary action approach allows the system to start collecting finger touch information immediately during available idle periods rather than waiting for a complete scanning window

Inventive Principle:

Principle #10Preliminary action

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 simultaneous operation of active styluses and fingers on capacitive touch panels by automatically detecting and partitioning scanning to avoid active stylus signal interference, effectively preventing the touch sensing circuit from stopping finger detection.

Implementation Method 1

the active stylus emits a first active stylus signal toward the capacitive touch panel according to a protocol; the capacitive touch panel transmits the first active stylus signal to the touch sensing circuit and the touch sensing circuit processes the first active stylus signal to generate an active stylus information

Methodology Applied

Scientific EffectElectromagnetic signal emission and detection: Electromagnetic Induction

Implementation Method 2

the touch sensing circuit performs a first finger touch sensing on the capacitive touch panel; during the second period after the first period, the active stylus stops emitting the first active stylus signal and a touch sensing circuit performs a first finger touch sensing on the capacitive touch panel

Methodology Applied

Scientific EffectCapacitive sensing: Capacitance

Data Source

PatentUS10514782B2Active stylus signal identification method applied to capacitive touch panel

Publication Date: 2019.12.24 RAYDIUM SEMICON

AI summary

An active stylus signal identification method applied to a capacitive touch panel is disclosed. When an active stylus and a finger approach the capacitive touch panel at the same time, the active stylus signal identification method includes steps of: (a) during a first period, the active stylus emits an active stylus signal toward the capacitive touch panel according to a protocol; (b) during a second period after the first period, the active stylus stops emitting the active stylus signal and a touch sensing circuit performs a finger touch sensing on the capacitive touch panel; (c) during a third period after the second period, the active stylus emits the active stylus signal toward the capacitive touch panel again according to the protocol.