White Light Interferometry for Rotating Clearance Measurement

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Solution Overview

Problem

Conventional measurement systems for clearance gaps between rotating nonmetallic components and fixed structures are inadequate, as they rely on electric or magnetic field variations that do not work with nonmetallic materials, making it difficult to measure radial growth and potential collisions during operation.

Innovation Solution

A white light interferometer system using a high-speed camera and beam splitter to measure clearance by reflecting white light off rotating components, combined with laser detection for precise alignment and control, enabling accurate determination of clearance and radial growth in nonmetallic structures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional measurement instruments relying on electric or magnetic field variations are used, then measurement capability is provided for metallic components, but measurement is impossible for nonmetallic components

Engineering Contradiction:

Improvemeasurement capability for different material typesVSAvoidmeasurement reliability for nonmetallic components

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent replaces electric and magnetic field-based measurement systems with an optical measurement system using white light interferometry. This substitution enables measurement of nonmetallic rotating components by using light reflection and interference patterns instead of electromagnetic field interactions, thereby extending measurement capability to nonconductive materials while maintaining measurement reliability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the measurement parameter from electromagnetic field variations to optical path length differences. By using white light interferometry, the system measures clearance gaps through changes in optical path length as light reflects off the rotating component surface, enabling accurate measurement of nonmetallic components where electromagnetic methods fail

Inventive Principle:

Principle #35Parameter changes

2Loss of information

If white light interferometer circuitry continuously measures clearance, then real-time monitoring is achieved, but energy consumption and system complexity increase

Engineering Contradiction:

Improvereal-time clearance dataVSAvoidenergy consumption of measurement system

Core Design Contradiction:

Loss of informationVSUse of energy by moving object

Solution Approach 1:

The patent implements periodic measurement action by triggering the white light interferometer only when the rotating component passes through a specific angular position detected by the position detector. This periodic triggering ensures real-time monitoring of clearance at critical moments while avoiding continuous operation, thereby reducing energy consumption and minimizing information loss

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent uses a feedback mechanism where the position detector monitors the rotational position and generates trigger signals to activate the white light interferometer at appropriate moments. This feedback-controlled periodic measurement ensures that clearance data is captured at critical rotation positions without requiring continuous measurement, optimizing both information acquisition and energy efficiency

Inventive Principle:

Principle #23Feedback

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 measurement of clearance gaps and radial growth in nonmetallic rotating components, preventing collisions and damage by providing real-time monitoring and analysis of geometric changes under rotating stresses.

Implementation Method 1

A white light interferometer circuitry reflects a white light beam off of at least one portion of the rotating structure responsive to the actuation signal to determine a clearance

Methodology Applied

Scientific EffectInterference: Interference

Implementation Method 2

A detector detects a reflection of the laser beam from the reflector when the reflector reflects the laser beam responsive to rotation of the reflector past the fixed position of the laser beam

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS12535312B2White light interferometer for measuring radial growth in components experiencing rotating stresses

Publication Date: 2026.01.27 RTX CORP

AI summary

An apparatus measures clearances between a rotating structure within a fixed surrounding structure. A position detector determines when at least one portion of the rotating structure rotates past a hole defined in the fixed surrounding structure and generates an actuation signal responsive to rotation of the at least one portion of the rotating structure past the hole defined in the fixed surrounding structure. White light interferometer circuitry reflects a white light beam off of at least one portion of the rotating structure responsive to the actuation signal to determine a clearance between the at least one portion of the rotating structure and an inner surface of the fixed structure. The actuation signal actuates the white light interferometer circuitry to reflect the white light beam off of the at least one portion of the rotating structure through the hole defined in the fixed surrounding structure.