Capacitive Touch Sensor Layout for Uniform Threshold on Curved Surfaces

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Solution Overview

Problem

Non-flat touch surfaces in capacitive touch sensing devices present challenges in setting a uniform capacitance threshold for touch indication due to varying distances and dielectric constants, leading to nonlinearity in analog capacitive touch sensing.

Innovation Solution

A capacitive touch sensor layer is configured to provide a uniform capacitance threshold level by maintaining a substantially uniform distance or using a gradient of dielectric constants between the non-flat touch surface and the sensor layer, allowing for consistent sensing across the surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a capacitive touch sensor uses a non-flat touch surface, then the device can accommodate complex structural designs and space constraints, but the capacitance threshold varies across different locations leading to nonlinearity in sensing

Engineering Contradiction:

Improvestructural design flexibilityVSAvoidcapacitance threshold uniformity

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent applies local quality by varying the dielectric constant of the material between the touch surface and sensor layer at different locations. Specifically, the dielectric material has a first dielectric constant in a first region and a second dielectric constant in a second region, where these constants are specifically chosen to compensate for the non-flat geometry and achieve uniform capacitance threshold across all locations.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the dielectric parameter (dielectric constant) of the material between the touch surface and sensor layer to compensate for geometric variations. By adjusting the dielectric constant spatially, the system maintains uniform capacitive coupling despite non-flat surface geometry, thereby achieving consistent capacitance threshold across different touch locations.

Inventive Principle:

Principle #35Parameter changes

2Shape

If the distance between the non-flat touch surface and capacitive touch sensor layer varies across locations, then the sensor can follow the surface geometry, but the capacitance values become location-dependent causing nonlinearity

Engineering Contradiction:

Improvesurface geometry conformityVSAvoidcapacitance threshold consistency

Core Design Contradiction:

ShapeVSMeasurement precision

Solution Approach 1:

The patent addresses this contradiction by making the dielectric material's properties location-specific. The dielectric constant is varied spatially so that regions with larger distances have higher dielectric constants and regions with smaller distances have lower dielectric constants, thereby compensating for the distance variations and achieving uniform capacitance threshold.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent introduces asymmetry in the dielectric material properties to counterbalance the asymmetry in the geometric distance distribution. By creating a deliberately asymmetric dielectric constant distribution that mirrors and compensates for the geometric asymmetry, the system achieves symmetric (uniform) capacitive response across all locations.

Inventive Principle:

Principle #4Asymmetry

3Device complexity

If overlaying materials and structures on the touch pad are non-flat, then the device can achieve compact design and integration, but it becomes difficult to set a uniform capacitive threshold value for touch indication

Engineering Contradiction:

Improveintegration compactnessVSAvoidthreshold setting uniformity

Core Design Contradiction:

Device complexityVSEase of operation

Solution Approach 1:

The patent changes the dielectric parameter of the overlaying materials to compensate for the non-flat geometry. By carefully selecting and positioning materials with appropriate dielectric constants, the system maintains uniform capacitive coupling through the overlaying structures, enabling both compact integration and uniform touch threshold response.

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

This configuration ensures consistent sensor signals regardless of location on the non-flat touch surface, enhancing the accuracy and linearity of capacitive touch sensing.

Implementation Method 1

capacitive touch sensor layer, configured to provide a sensor signal using a uniform capacitance threshold level

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

a gradient of a dielectric constant of materials between the non-flat touch surface and the capacitive touch sensor layer

Methodology Applied

Scientific EffectDielectric: Dielectric

Data Source

PatentUS8063330B2Uniform threshold for capacitive sensing

Publication Date: 2011.11.22 NOKIA TECHNOLOGIES OY

AI summary

The specification and drawings present a new apparatus and method for providing and using a uniform threshold for capacitive touch sensing in a user interface having a non-flat touch surface. The capacitive touch sensor can to provide a sensor signal using the uniform capacitance threshold level as a function of a location of an object (e.g., finger, stylus, etc.) on or near the non-flat touch surface of a user interface module using a substantially uniform distance between the non-flat touch surface and a capacitive touch sensor layer, and/or using a gradient of a dielectric constant of materials between the non-flat touch surface and the capacitive touch sensor layer according to a predetermined criterion.