Optical Curvature Sensor Using Evanescent Wave Frustrated Total Internal Reflection

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Solution Overview

Problem

Existing optically operating strain sensors face challenges in miniaturization and cost due to the need for special components and precise arrangements, making them difficult and expensive to produce, while also being susceptible to errors and failures.

Innovation Solution

A light conductor with cracks angled relative to its propagation direction, where evanescent waves are produced, allowing for frustrated total internal reflection and enabling sensitive deformation measurements with reduced component complexity and cost.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If special components and precise arrangements are used in optical strain sensors, then measurement precision is improved, but device complexity and manufacturing cost increase

Engineering Contradiction:

Improvenanometer range detection accuracyVSAvoidcomponent complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The invention extracts and eliminates the need for complex spectral analysis components by using a different measurement principle. Instead of requiring spectrometers and precise column arrangements for spectral analysis, the patent uses simple intensity measurement of light affected by evanescent waves at crack boundaries, thereby achieving nanometer precision without complex components

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention replaces the mechanical/optical system requiring precise physical arrangements with an electromagnetic field-based solution. By utilizing evanescent waves and their interaction with crack boundaries, the system achieves precise measurement through field interactions rather than mechanical precision, substituting complex mechanical arrangements with electromagnetic phenomena

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If special components and precise arrangements are used in optical strain sensors, then measurement precision is improved, but manufacturing cost increases

Engineering Contradiction:

Improvenanometer range detection accuracyVSAvoidproduction cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The invention removes the requirement for expensive spectral analysis equipment and precise column manufacturing. By measuring light intensity changes caused by evanescent wave interactions at crack boundaries rather than requiring full spectral analysis, the system achieves nanometer precision using inexpensive components

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention employs simple, inexpensive light conductors with cracks instead of expensive, precisely manufactured optical components. The light conductor with crack structure can be produced using standard fabrication techniques rather than requiring specialized expensive components, making the sensor cost-effective

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Measurement precision

If precise arrangement of columns in the light conductor is required, then measurement precision is improved, but manufacturing difficulty and susceptibility to errors increase

Engineering Contradiction:

Improvedetection accuracyVSAvoidcolumn arrangement precision

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The invention eliminates the requirement for precise column arrangements entirely by using a different measurement approach. Instead of relying on precise physical positioning of columns for spectral analysis, the system uses evanescent wave interactions at crack boundaries, removing the manufacturing precision bottleneck

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention changes the measurement parameter from spectral analysis requiring precise geometric arrangements to intensity measurement based on evanescent wave interactions. This parameter change allows measurement of nanometer-scale deformations without requiring precise column positioning, as the evanescent wave interaction is sensitive to boundary conditions rather than overall geometry

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 enables highly sensitive, miniaturizable, and cost-effective optical sensors capable of detecting nanometer-scale changes in length, with improved reliability and reduced susceptibility to errors, allowing for simultaneous measurement of strains and bends.

Implementation Method 1

wherein on the first boundary surface an evanescent wave is produced

Methodology Applied

Scientific EffectEvanescent wave: Total Internal Reflection

Implementation Method 2

wherein the second boundary surface is arranged within the evanescent wave

Methodology Applied

Scientific EffectFrustrated total internal reflection: Total Internal Reflection

Data Source

PatentUS10788339B2Optical curvature sensor

Publication Date: 2020.09.29 ZACKL WILHELM

AI summary

The invention relates to a light conductor for sensory purposes, comprising at least one crack, wherein a longitudinal direction of the crack relative to a direction of propagation of the light conductor includes an angle of incidence (θ), and wherein the crack is delimited by two boundary surfaces, each of which is substantially parallel to the longitudinal direction of the crack, the two boundary surfaces including an opening angle (α), said opening angle (α) being greater than 0°.