Capacitive Sensor Electrode Segmentation for Impedance Control

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Solution Overview

Problem

Transparent capacitive touch sensors face challenges due to the high resistance of transparent conductors like Indium Tin Oxide, which makes it difficult to implement reliable sensors with low impedance nodes, leading to susceptibility to walk-by interference and circuit design issues when combined with low-resistance wiring.

Innovation Solution

A capacitive sensor design featuring a substrate with resistive electrodes and shorting connections between them, reducing impedance and minimizing walk-by interference, allowing for efficient charge coupling and improved sensitivity, even with resistive transparent conductors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If transparent conductors like Indium Tin Oxide are used for electrodes, then transparency is achieved, but electrical resistance increases making it difficult to implement reliable sensors with low impedance nodes

Engineering Contradiction:

ImprovetransparencyVSAvoidimpedance control

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The electrode is divided into multiple segments with different resistance characteristics. A first electrode region has higher resistance optimized for transparency, while a second electrode region has lower resistance optimized for signal detection. This segmentation allows each region to perform its specialized function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the electrode structure are assigned different electrical properties. The first electrode region uses transparent conductor material with higher resistance for transparency-critical areas, while the second electrode region uses material or structure optimized for lower resistance in signal-critical areas. This local differentiation resolves the contradiction between transparency and reliability.

Inventive Principle:

Principle #3Local quality

2Illumination intensity

If high resistance transparent conductors are used, then transparency is maintained, but susceptibility to walk-by interference increases

Engineering Contradiction:

ImprovetransparencyVSAvoidwalk-by interference

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The sensor is segmented into two electrode regions with different resistance characteristics. The first region maintains transparency with higher resistance, while the second region provides low-impedance signaling with lower resistance, thereby reducing susceptibility to walk-by interference while preserving transparency.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The electrode structure uses a composite arrangement of different conductor materials or configurations. One region uses transparent conductor material (higher resistance) and another region uses material or structure optimized for lower resistance, creating a composite electrode system that achieves both transparency and resistance to walk-by interference.

Inventive Principle:

Principle #40Composite materials

3Illumination intensity

If resistive transparent conductors are used, then transparency is achieved, but charge detection efficiency decreases

Engineering Contradiction:

ImprovetransparencyVSAvoidcharge detection efficiency

Core Design Contradiction:

Illumination intensityVSMeasurement precision

Solution Approach 1:

The electrode is segmented into a first region optimized for transparency and a second region optimized for charge detection. The second region has lower resistance and is specifically configured to efficiently detect charge changes, while the first region maintains transparency. This segmentation allows charge detection efficiency to be improved without sacrificing transparency.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the electrode have different electrical properties tailored to their specific functions. The second electrode region has local quality optimized for charge detection with lower resistance, while the first region has local quality optimized for transparency with higher resistance, resolving the contradiction between these two requirements.

Inventive Principle:

Principle #3Local quality

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

The sensor design effectively reduces walk-by interference and maintains sensitivity, enabling reliable operation of transparent capacitive touch sensors by reducing impedance and enhancing charge detection efficiency.

Implementation Method 1

The degree of capacitive coupling of this drive signal to the sense electrode is determined by measuring the amount of charge transferred to the sense electrode in response to changes in the drive signal

Methodology Applied

Scientific EffectCapacitive coupling: Capacitance

Implementation Method 2

Methodology Applied

Scientific EffectElectrical resistance: Electrical Resistance

Data Source

PatentUS9250751B2Touch sensitive screen

Publication Date: 2016.02.02 NEODRON LTD

AI summary

One embodiment provides a capacitive sensor for determining the presence of an object, such as a user's finger or a stylus. The sensor includes a substrate on which electrodes are deposited. A resistive drive electrode is arranged on one side of the substrate and a resistive sense electrode is arranged on the other side of the substrate. A shorting connection connects between two locations on one of the electrodes. The electrodes are connected to respective drive and sense channels.