Touch Sensor Force Response Normalization via Compressible Foam Cushion

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Solution Overview

Problem

Existing touch sensors face challenges in providing uniform capacitance responses across different locations due to varying force applications, leading to inconsistent touch detection and proximity sensing.

Innovation Solution

A touch screen device comprising a controller, a force sensing layer, a cushion layer made of compressible foam material, and a reference layer with discrete raised areas, which normalizes capacitance responses by ensuring uniform distance between the force sensing and reference layers across the touch-sensitive area, using a cushion layer that compresses and returns to its original thickness and a reference layer with varying density and dimples to distribute force uniformly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a traditional touch sensor structure is used, then the device is simple in structure, but the capacitance response varies across different locations leading to inconsistent touch detection

Engineering Contradiction:

Improvetouch detection consistencyVSAvoidsensor structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The reference layer incorporates discrete raised areas with varying heights and densities across different regions of the touch-sensitive area. These localized structural variations compensate for non-uniform force distribution, ensuring consistent capacitance responses across all locations without requiring complete structural redesign

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

A cushion layer comprising compressible foam material is introduced between the force sensing layer and the reference layer. This intermediary layer distributes applied forces more uniformly across the reference layer, reducing location-dependent variations in capacitance response while maintaining overall system simplicity

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the reference layer has uniform structure, then the manufacturing is simple, but the capacitance response is not normalized across different locations

Engineering Contradiction:

Improvecapacitance response normalizationVSAvoidreference layer manufacturing

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The reference layer features discrete raised areas with spatially varying heights and densities - higher density and greater heights in center regions, lower density and smaller heights in peripheral regions. This localized differentiation normalizes capacitance responses across the touch surface while using standard manufacturing techniques

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The reference layer structure utilizes variations in the physical parameters of the raised areas (height, density, spacing) to achieve capacitance normalization. By adjusting these parameters across different regions, the system compensates for non-uniform force application without changing the fundamental layer structure

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If the cushion layer is made rigid, then the structural stability is high, but the force distribution across locations is non-uniform

Engineering Contradiction:

Improvelayer structure stabilityVSAvoidforce sensing uniformity

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The cushion layer uses compressible foam material that changes its mechanical properties under applied force. This material allows dynamic adjustment of force distribution - remaining stable in structure while becoming more compliant during operation to achieve uniform force transmission across all locations

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

The solution ensures uniform capacitance responses across the touch screen, enhancing the accuracy and reliability of touch and proximity detection by normalizing the force sensing across all locations, thereby improving user interaction with touch-sensitive devices.

Implementation Method 1

a cushion layer between the force sensing layer and the reference layer, the cushion layer comprising a foam material that is configured to compress under applied force and to expand toward an original thickness when the applied force is released

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

the processor configured to detect a capacitance between locations of a force sensing layer and corresponding locations of a reference layer spaced from the force sensing layer responsive to an initiated voltage

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS10649595B2Touch sensor with force sensor response normalization, and related method and apparatus

Publication Date: 2020.05.12 ATMEL CORP

AI summary

In one embodiment, a touch screen device includes a controller, a force sensing layer, a cushion layer, and a reference layer. The controller includes a processor to determine a distance between the force sensing layer and the reference layer. The cushion layer is between the force sensing layer and the reference layer. The cushion layer may include a plurality of holes at selected locations devoid of material of which the cushion layer is made. The reference layer may include a plurality of raised areas at selected locations.