Fiber Optic Hole Scanning for Interface Gap Measurement

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Solution Overview

Problem

Determining the size of gaps within interface regions in fabricated parts, particularly in aerospace components, is complicated and time-consuming, often requiring manual insertion of feeler gauges and is operator-dependent, especially for parts with numerous holes.

Innovation Solution

Utilizing a fiber optic probe for interferometry to scan and measure interface gaps in holes, with an actuator to adjust the probe's position and a control unit to detect gaps based on the profile data, enabling automatic and efficient gap measurement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If manual feeler gauge insertion is used to measure interface gaps, then measurement capability is achieved, but measurement time and labor requirements increase significantly

Engineering Contradiction:
Improvegap measurement capabilityVSAvoidmeasurement speed
Core Design Contradiction:
Measurement precisionVSProductivity

Solution Approach 1:

The patent replaces the mechanical feeler gauge system with an optical interferometry system using a fiber optic probe. The probe emits light that interferes with reference light to automatically measure gap dimensions, eliminating manual mechanical insertion and reading operations. This substitution maintains measurement precision while dramatically increasing productivity by enabling rapid automated measurements across hundreds or thousands of holes.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The fiber optic probe system performs self-measurement by automatically scanning through holes and detecting interface gaps without requiring operator intervention for each measurement. The system autonomously captures interference patterns, processes the data, and generates measurements, transforming a labor-intensive manual process into an automated self-service measurement system that significantly improves productivity.

Inventive Principle:
Principle #25Self-service

2Reliability

If visual inspection of gaps at multiple holes is performed, then gap detection is possible, but time and manpower consumption increase

Engineering Contradiction:
Improvegap detection capabilityVSAvoidinspection time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The patent replaces visual inspection with optical interferometry using a fiber optic probe that emits and detects light interference patterns. This substitution enables automated, high-speed detection of interface gaps at multiple holes without requiring manual visual examination. The system maintains reliable gap detection capability while reducing inspection time by processing measurements continuously and automatically across all holes.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If iterative feeler gauge insertion is performed to find appropriate shim size, then gap measurement is achieved, but measurement process becomes time-consuming and operator-dependent

Engineering Contradiction:
Improvegap size determinationVSAvoidmeasurement process complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the iterative mechanical feeler gauge process with a single-pass optical interferometry measurement. The fiber optic probe directly measures the complete gap profile and determines the required shim size in one automated operation, eliminating the iterative trial-and-error process. This substitution maintains accurate gap size determination while simplifying the measurement process and removing operator dependency.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The fiber optic probe system performs preliminary automated scanning and profiling of the hole and interface gap before final measurement and shim specification. By pre-characterizing the gap geometry and dimensions through automated optical scanning, the system eliminates the need for iterative feeler gauge insertion and preliminary manual assessments, streamlining the entire measurement process into a single efficient operation.

Inventive Principle:
Principle #10Preliminary action

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

Substantially reduces labor and time required for gap measurement, allowing for reliable and rapid detection of interface gaps, sealant, and Foreign Object Debris (FOD) in fabricated parts.

Implementation Method 1

utilizing insertable probes that perform interferometry in order to determine the sizes of gaps between sheets of material

Methodology Applied
Scientific EffectInterferometry: Interference

Data Source

PatentEP4715323A2Non-contact measurement for interface gaps
Publication Date: 2026.03.25 THE BOEING CO
  • EP4715323A2 patent drawingFigure 1
  • EP4715323A2 patent drawingFigure 2
  • EP4715323A2 patent drawingFigure 3

AI summary

A method (200) for measuring a hole (130) comprises: driving (202) a fiber optic probe (114) into the hole; determining (204) a profile (128) by scanning walls (132) of the hole via the fiber optic probe; determining (206) whether an interface gap (140) exists at the walls of the hole based on the profile; and if the interface gap exists, identifying (220) sealant (1110) at the interface gap based on a region (1344) of the profile representing the interface gap.