Low-Coherence Interferometry for Optical Element Positioning

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Solution Overview

Problem

In industrial processes, particularly in laser processing and measurement, accurately determining the relative position of optical elements and the separation distance between processing tools or measuring instruments and objects is challenging due to variations in temperature, mechanical deformation, and positioning errors.

Innovation Solution

The method employs low-coherence interferometry, using a low-coherence optical measurement beam and a reference beam to determine the relative position of optical elements and the separation distance by analyzing interference fringes, which allows for precise and robust measurements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional measurement methods are used to determine the position of optical elements, then the device complexity is low, but the measurement precision deteriorates due to temperature variations and mechanical deformation

Engineering Contradiction:

Improveposition determination accuracyVSAvoidmeasurement system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces mechanical position sensing methods with optical interferometry. A measurement beam and reference beam are used to create interference fringes, where the position of optical elements is determined by analyzing fringe patterns rather than mechanical encoders or sensors. This substitution achieves high measurement precision while being insensitive to temperature variations and mechanical deformation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the measurement parameter from direct mechanical position reading to optical path difference analysis. By measuring the interference fringe patterns resulting from the superposition of measurement and reference beams, the system determines position through optical parameter changes rather than mechanical parameter changes, achieving higher precision and environmental stability.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If sequential measurement methods are used, then the device complexity is low, but the productivity deteriorates due to time-consuming individual measurements

Engineering Contradiction:

Improvemeasurement speedVSAvoidmeasurement system complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent merges multiple measurement functions into a single interferometric system. The same measurement beam and reference beam configuration is used to simultaneously determine the positions of multiple optical elements (such as lenses and mirrors) and the separation distance between the processing tool and workpiece. This consolidation enables parallel measurements, significantly improving productivity without requiring separate measurement systems for each parameter.

Inventive Principle:

Principle #5Merging (Combining)

3Measurement precision

If high-precision position sensing is implemented, then the measurement precision improves, but the reliability deteriorates due to sensitivity to environmental perturbations

Engineering Contradiction:

Improveposition determination accuracyVSAvoidmeasurement stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent introduces an interferometric measurement system as an intermediary between the optical elements and the position determination process. The interference fringes act as a mediator that translates physical position changes into measurable optical patterns. This intermediary approach provides high precision while being inherently stable against environmental perturbations, as the differential measurement between measurement and reference beams compensates for common-mode disturbances.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 enables accurate and real-time monitoring of processing or measurement processes, compensating for measurement perturbations and allowing for parallel measurements of multiple elements or surfaces, thereby improving the precision and efficiency of industrial processes.

Implementation Method 1

Methodology Applied

Scientific EffectInterference: Interference

Data Source

PatentUS12298131B2Method and system for determining the position of an element of an optical system in an assembly for processing or measuring an object, as well as the position of said object relative to said assembly, by parallel interferometric measurements

Publication Date: 2025.05.13 ADIGE SPA

AI summary

A method and a system for determining relative position of an element of an optical system of an assembly for processing or measuring an object along a measurement line, involve generating a measurement beam and a reference beam of low coherence optical radiation. The measurement and reference beams, alternately or in combination, have a main beam and a multiplexed additional beam. The measurement beam, led toward the element of the optical system, and back-reflected, is superimposed on the reference beam in a region of common incidence of an interferometric optical sensor arrangement. Position or frequency of a main interference fringe pattern and an additional interference fringe pattern is detected.