Multimode Waveguide Displacement Sensor

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Solution Overview

Problem

Current displacement measurement technologies face challenges in achieving nanometer precision without contact, especially in non-metallic objects and environments with electromagnetic interference, and are unsuitable for sub-nanometer scale measurements due to size and material limitations.

Innovation Solution

A system utilizing a multimode waveguide and a light source to direct light onto an object, capturing the reflected light's modal power distribution, and comparing it with predetermined characteristics to determine displacement, allowing for non-contact, high-precision measurements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If capacitance probe is used for non-contact displacement measurement, then measurement precision is improved, but it requires electrode plate attachment which increases device complexity and is unsuitable for non-metallic objects

Engineering Contradiction:

Improvedisplacement measurement precisionVSAvoidelectrode plate attachment

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical/electrical capacitance probe system with an optical system. Instead of using electrode plates and electrical fields to measure displacement, the invention uses light sources, optical waveguides, and photodetectors to detect displacement through optical interference patterns, eliminating the need for electrical contacts and electrode attachments.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an optical waveguide as an intermediary between the light source and the displacement measurement point. The waveguide transmits light to the measurement location and carries the reflected light back to the detector, enabling non-contact measurement without requiring direct electrical contact with the object being measured.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If capacitance sensor is used in electromagnetic environment, then displacement measurement is achieved, but reading accuracy deteriorates due to electromagnetic radiation noise

Engineering Contradiction:

Improvedisplacement measurement accuracyVSAvoidelectromagnetic radiation noise

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the electrical capacitance sensing system that is vulnerable to electromagnetic interference with an optical measurement system. Optical signals are immune to electromagnetic radiation, allowing accurate displacement measurement in environments with strong electromagnetic fields where electrical sensors would fail.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If fiber Bragg grating sensor is used for displacement measurement, then measurement capability is achieved, but design fabrication complexity increases

Engineering Contradiction:

Improvedisplacement measurement capabilityVSAvoiddesign fabrication complexity

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent extracts the measurement function from complex integrated sensors like fiber Bragg grating and implements it through a separate, modular optical waveguide system. This allows the measurement capability to be achieved without the fabrication complexities of writing gratings into optical fibers, simplifying the manufacturing process.

Inventive Principle:

Principle #2Taking out (Extraction)

4Measurement precision

If Fabry-Perot sensor is used for displacement measurement, then measurement function is achieved, but reliability decreases due to high stress and liquid contact

Engineering Contradiction:

Improvedisplacement measurement functionVSAvoidsensor durability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the mechanical Fabry-Perot cavity structure with an optical waveguide-based measurement system. This eliminates the need for flexible membranes and liquid fills that are prone to stress and leakage, improving the reliability and durability of the sensor while maintaining displacement measurement capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 precise displacement measurement with sub-nanometer accuracy, overcoming limitations of existing technologies by providing a non-contact method suitable for small, non-metallic objects and environments with electromagnetic interference.

Implementation Method 1

propagating the reflected light through different propagation modes

Methodology Applied

Scientific EffectLight propagation through waveguide modes: Waveguide (optics)

Implementation Method 2

directing a light onto the object resulting in a reflected light

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 3

a modal power distribution sensor capturing the exited reflected light at the second end, and extracting a characteristic of the modal power distribution

Methodology Applied

Scientific EffectOptical detection: Photoelectric Effect

Data Source

PatentUS10156433B1System and method for measuring displacement

Publication Date: 2018.12.18 THE CHINESE UNIVERSITY OF HONG KONG

AI summary

A method and a system for determining a displacement of an object are provided. The method includes: providing a predetermined modal power distribution characteristic; directing a light onto the object resulting in a reflected light; propagating the reflected light through different propagation modes, receiving a resulting modal power distribution characteristic; and comparing the resulting modal power distribution characteristic with the predetermined modal power distribution characteristic to determine the displacement of the object.