Touch Panel Water Detection via Capacitance Variation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Electrostatic capacitance type touch panel devices struggle to distinguish between water droplets and finger or pen inputs, leading to malfunctions and incorrect responses, due to similar signal variations, and complicate the structure with resistive electrodes for prevention.

Innovation Solution

A touch panel device with an electrostatic capacitance touch panel of mutual capacitance type, using transmission-side and reception-side electrodes, includes a detecting unit, signal variation calculator, and determining unit that sets negative and positive thresholds to differentiate between water and other objects based on signal variations and peripheral area analysis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If resistive electrodes are used to prevent malfunction due to water drops, then reliability is improved, but device complexity increases

Engineering Contradiction:

Improveprevention of malfunction due to water dropsVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the detection parameter from resistance value (in resistive touch panels) to electrostatic capacitance. By monitoring capacitance variations at touch panel positions, the system can distinguish between water drops and finger touches based on the different capacitance characteristics, thereby preventing malfunctions without adding structural complexity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical/resistive electrode system with an electrostatic capacitance-based detection system. This substitution eliminates the need for physical resistive electrodes while achieving water drop detection through electrical field measurements, reducing structural complexity while maintaining or improving reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If electrostatic self-capacitance type touch switch is used, then device complexity is reduced, but measurement precision deteriorates due to inability to distinguish water drops from finger touches

Engineering Contradiction:

Improvestructure simplicityVSAvoiddetection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent transitions from self-capacitance measurement (single dimension) to mutual capacitance measurement between transmission and reception electrodes (two-dimensional matrix). This dimensional change enables spatial resolution of capacitance variations across the touch panel surface, allowing distinction between water drops and finger touches based on their different spatial capacitance patterns.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent implements a feedback mechanism where the operation determination unit continuously monitors capacitance variations, compares them against predetermined thresholds, and adjusts its determination logic accordingly. This feedback loop enables accurate distinction between water drops and valid touch inputs by analyzing the characteristics and patterns of capacitance changes.

Inventive Principle:

Principle #23Feedback

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

This solution simplifies the structure by accurately distinguishing between water and other objects without complicating the design, preventing malfunctions and ensuring correct responses by using signal thresholds and peripheral analysis.

Implementation Method 1

an electrostatic capacitance touch panel of mutual capacitance type which includes a plurality of transmission-side electrodes and a plurality of reception-side electrodes

Methodology Applied

Scientific EffectElectrostatic capacitance: Capacitance

Implementation Method 2

when a peak value of the variation distribution of the detection signals is a predetermined negative threshold or less... determines that an object contacting the electrostatic touch panel is a drop of water

Methodology Applied

Scientific EffectElectrostatic induction: Electrostatic Induction

Data Source

PatentUS8976153B2Touch panel device detecting water

Publication Date: 2015.03.10 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A touch panel device includes: an electrostatic capacitance touch panel of mutual capacitance type which includes transmission-side electrodes and reception-side electrodes; a detecting unit which detects a contact with the electrostatic touch panel and outputs contact information; and a detection signal variation calculating unit which calculates and outputs detection signal variations of the transmission-side electrodes and the reception-side electrodes based on the contact information. The touch panel device further includes: a variation distribution calculating unit which calculates and outputs a variation distribution of the detection signals based on the detection signal variations; and a determining unit which determines that an object contacting the electrostatic touch panel is a drop of water when a peak value of the variation distribution of the detection signals is a predetermined negative threshold or less.