Air Gap Force Sensing in Touch Displays

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Solution Overview

Problem

Existing touch-sensitive displays in portable electronic devices face challenges in accurately detecting force applied by users due to limited space and the need for precise input recognition, which affects the functionality and usability of these devices.

Innovation Solution

The implementation of a touch sensor and a force-sensing electrode separated by an air gap, where changes in capacitance between the touch sensor and the electrode are used to determine the force applied, allowing for accurate detection and differentiation of touch forces on the display.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If a touch sensor and electrode are placed close together to save space, then device portability is improved, but measurement precision of force detection deteriorates

Engineering Contradiction:
Improvedevice sizeVSAvoidforce detection accuracy
Core Design Contradiction:
Volume of moving objectVSMeasurement precision

Solution Approach 1:

An air gap is introduced as an intermediary space between the touch sensor and the electrode. This air gap acts as a mediator that transmits force-induced bending to the touch sensor while maintaining sufficient separation for accurate force detection, thus resolving the contradiction between compact device size and measurement precision.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent utilizes changes in capacitance as a parameter to detect force applied to the display. By monitoring capacitance variations between the touch sensor and electrode through the air gap, the system can precisely measure force magnitude while maintaining a compact form factor, addressing both device size and measurement accuracy requirements.

Inventive Principle:
Principle #35Parameter changes

2Measurement precision

If the air gap between touch sensor and electrode is increased to improve force detection accuracy, then measurement precision is improved, but device complexity increases

Engineering Contradiction:
Improveforce detection accuracyVSAvoidstructural complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The air gap structure serves multiple functions simultaneously: it provides the necessary separation for accurate capacitance-based force detection, acts as a mechanical spacer to maintain electrode positioning, and enables the touch sensor to detect both touch location and force magnitude. This multi-functionality reduces overall device complexity despite the increased measurement precision.

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 enables precise detection of force values applied to the touch-sensitive display, enhancing user input recognition and improving the overall usability and functionality of portable electronic devices by accurately determining the force and location of touches, thereby enabling better interaction with the device.

Implementation Method 1

a change in capacitance between the touch sensor and the electrode is utilized to determine a value related to a force causing bending of the touch sensor

Methodology Applied
Scientific EffectCapacitance: Capacitance

Data Source

PatentEP2732361B1Electronic device and method of controlling a touch-sensitive display
Publication Date: 2018.05.23 BLACKBERRY LTD
  • EP2732361B1 patent drawingFigure 1
  • EP2732361B1 patent drawingFigure 2~5
  • EP2732361B1 patent drawingFigure 6~8

AI summary

A device includes a touch sensor, and at least one electrode spaced from touch sensor by an air gap, wherein a change in capacitance between the touch sensor and the electrode is utilized to determine a value related to a force imparted on the device.