Guarded Capacitive Interface with Display Integration for Longer Range

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Solution Overview

Problem

Capacitive technologies struggle to detect objects at a distance beyond a few centimeters due to stray capacitances and electromagnetic disturbances, and are not well-suited for non-planar surfaces or integrating additional electronic functions without degrading sensitivity.

Innovation Solution

A capacitive detection device with a guard electrode excited to an alternating electric potential identical to the measurement electrodes, combined with floating bridge electronics that integrate additional functions referenced to the guard potential, reducing stray capacitances and allowing for enhanced sensitivity and range.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If capacitive sensors are used for proximity detection, then sensitivity to finger approach is improved, but detection range is limited to a few centimeters due to stray capacitances

Engineering Contradiction:

ImprovesensitivityVSAvoiddetection range

Core Design Contradiction:

Measurement precisionVSLength of stationary object

Solution Approach 1:

The patent extracts and eliminates the harmful stray capacitances from the measurement circuit by using a guard electrode that is kept at the same potential as the measurement electrode, effectively removing the parasitic capacitance effect and enabling longer detection range while maintaining sensitivity

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a guard electrode as an intermediary element between the measurement electrode and the surrounding environment. This guard electrode, maintained at the same potential as the measurement electrode, mediates the electric field distribution and prevents stray capacitance from affecting the measurement, thereby extending detection range

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If additional electronic functions are integrated adjacent to measurement electrodes, then device functionality is enhanced, but capacitive measurement performance degrades due to electromagnetic disturbances

Engineering Contradiction:

Improvedevice functionalityVSAvoidcapacitive measurement performance

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent applies equipotentiality by maintaining the guard electrode and additional electronic functions at the same electric potential as the measurement electrode. This eliminates potential differences that would cause electromagnetic interference, allowing additional functions to be integrated without degrading measurement performance

Inventive Principle:

Principle #12Equipotentiality

3Adaptability or versatility

If capacitive sensors are used on non-planar surfaces, then integration flexibility is improved, but measurement accuracy deteriorates due to irregular electric field distribution

Engineering Contradiction:

Improveintegration flexibilityVSAvoidmeasurement accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent applies local quality by adapting the guard electrode configuration to match the local geometry of the measurement surface. The guard electrode is shaped and positioned to follow the non-planar surface contours, ensuring that the equipotential condition is maintained locally across the irregular surface, thereby preserving measurement accuracy

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

Enables accurate detection of objects up to several centimeters without interference from stray capacitances, and allows integration of additional electronic functions like lighting and displays without degrading capacitive measurement performance.

Implementation Method 1

Capacitive technologies are frequently used because... they are well-adapted to the meshing of the screen surface by a sensor network directly integrated to the surface thereof

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS9151791B2Capacitive control interface device having display integration

Publication Date: 2015.10.06 QUICKSTEP TECHNOLOGIES LLC

AI summary

A capacitive detection control interface device is provided, including at least one measurement electrode including an active surface, a guard made from an electrically conductive material placed adjacent to the measurement electrodes, the guard is excited up to an alternating electric potential substantially identical to that of the measurement electrodes, a first electronic component for exciting the electrodes and processing the measurement signals from the capacitive coupling of the electrodes with an object laced adjacent thereto, the electronic component is at least partly referenced to the electric potential of the guard, and a second electronic component for performing another functional display, placed adjacent to the active surface which second electronic component is at least partly referenced to the electric potential of the guard.