Optical Fiber Defect Detection Using Phase-Shifted Interferometry

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Solution Overview

Problem

Current methods for inspecting fiber optic connector endfaces require separate instruments or processes for geometry and surface quality analysis, with interferometric devices generating obscured images that necessitate additional visual inspections for defect detection.

Innovation Solution

A computing system that uses an interferometer to generate phase-shifted images, processes them to create 3D surface and phase modulation data, and applies 2D image processing techniques to detect defects, potentially eliminating the need for separate visual inspections.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If an interferometric device is used to measure fiber endface geometry, then measurement precision is improved, but the generated images are obscured with optical fringe patterns making defect detection difficult

Engineering Contradiction:

Improvegeometry measurement precisionVSAvoiddefect detection difficulty

Core Design Contradiction:

Measurement precisionVSDifficulty of detecting and measuring

Solution Approach 1:

The patent segments the interferometric measurement process into distinct computational stages: acquiring multiple phase-shifted images, generating intermediate data sets through phase unwrapping, and performing defect detection on processed data. This segmentation allows the geometry measurement function to operate independently while the processed data is separately used for defect detection, resolving the contradiction between measurement precision and defect detectability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces intermediate data sets as a mediator between the raw interferometric images and the final defect detection results. These intermediate data sets (phase-unwrapped data, slope data, curvature data) serve as a bridge that preserves the high precision geometry information while eliminating the obscuring fringe patterns, enabling both precise measurement and clear defect detection.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If separate instruments are used for geometry measurement and defect inspection, then measurement precision and defect detection capability are improved, but device complexity increases

Engineering Contradiction:

Improvegeometry and defect measurement precisionVSAvoidinstrumentation complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent merges the geometry measurement and defect detection functions into a single integrated system. By using one interferometric device to capture phase-shifted images and then applying computational processing to extract both geometric parameters and defect information, the system achieves the functionality of multiple instruments while reducing device complexity and coordination requirements.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent makes the interferometric device universal by enabling it to perform multiple functions: measuring endface geometry (sagitta, radius of curvature, apex offset) and detecting surface defects (scratches, digs, contaminants). The single device processes images to generate various intermediate data sets that serve different measurement purposes, eliminating the need for separate specialized instruments.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Ease of operation

If visual microscope inspection is used for defect detection, then ease of operation is improved, but measurement precision and sensitivity decrease

Engineering Contradiction:

Improveinspection operation easeVSAvoiddefect detection precision

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent replaces the mechanical visual inspection system with an automated optical-interferometric system. Instead of relying on operators to visually examine magnified images, the system uses interferometric imaging combined with automated computational processing (phase unwrapping, slope calculation, curvature analysis) to detect and characterize defects, thereby replacing manual mechanical inspection with automated optical measurement while improving precision.

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

This approach enhances defect detection sensitivity and accuracy, providing higher resolution and reducing computational intensity, allowing for efficient detection of small defects on fiber optic endfaces.

Implementation Method 1

The interferometer is configured to generate at least two phase shifted images of an optical fiber specimen... an interferometric device which uses various optical interference techniques to generate a three-dimensional map of the fiber endface

Methodology Applied

Scientific EffectOptical interference: Interference

Data Source

PatentUS8306760B1Defect detection on optical fiber specimen using 3D surface data

Publication Date: 2012.11.06 PROMET INT

AI summary

A computing system includes an interferometer and a processor. The interferometer is configured to generate at least two phase shifted images of an optical fiber specimen. The processor is configured to acquire the at least two phase shifted images from the interferometer, generate a first intermediate data set based on the at least two acquired phase shifted images and perform two-dimensional defect detection on the first intermediate data set.