Fabry-Perot Interferometer Spectral Calibration via Notch Filter

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Solution Overview

Problem

Existing spectrometers using Fabry-Perot interferometers face challenges in maintaining spectral calibration stability due to factors like temperature changes, aging, and mechanical impacts, which affect the accuracy of spectral analysis.

Innovation Solution

Incorporating a notch filter to create a stable spectral notch that matches the transmittance notch of the notch filter, allowing for calibration and verification of spectral data by correlating measured intensity distributions with the notch filter's transmittance, thereby stabilizing the spectral scale.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If spectral calibration is performed using gas discharge lamps, then spectral scale can be determined, but calibration stability deteriorates due to temperature changes, aging, and mechanical impacts

Engineering Contradiction:

Improvespectral calibration accuracyVSAvoidcalibration stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent introduces a notch filter as an intermediary reference element with a stable transmittance notch that serves as a mediator between the light source and the Fabry-Perot interferometer. This notch filter provides a fixed spectral reference that is insensitive to temperature, aging, and mechanical impacts, thereby stabilizing the calibration process while maintaining measurement precision

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the calibration reference from gas discharge lamps (which have unstable spectral lines due to temperature and aging) to a notch filter with a stable transmittance notch. By matching the interferometer transmission peaks to the notch filter's transmittance notch, the calibration parameters become resistant to environmental changes and aging effects

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If Fabry-Perot interferometer is used for spectral analysis, then spectral resolution is improved, but spectral scale stability deteriorates under environmental conditions

Engineering Contradiction:

Improvespectral resolutionVSAvoidspectral scale stability

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The notch filter acts as a stable intermediary reference that provides fixed spectral markers (transmittance notch) for the Fabry-Perot interferometer to lock onto. This mediator enables the interferometer to maintain its high spectral resolution while achieving stability against temperature changes, aging, and mechanical impacts by continuously referencing the notch filter's invariant transmittance characteristics

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent implements a feedback mechanism where the spectral position of the interferometer transmission peaks is continuously compared with the notch filter's transmittance notch. This feedback loop allows real-time correction of drift in the interferometer's spectral scale, maintaining both high resolution and long-term stability under varying environmental conditions

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

This approach ensures accurate and stable spectral analysis, maintaining spectral scale integrity even in harsh environments and reducing the impact of temperature changes, aging, and mechanical stress.

Implementation Method 1

forming a spectral notch (NC2) by filtering input light (LB1) with a notch filter (60) such that the spectral notch (NC2) corresponds to a transmittance notch (NC1) of the notch filter (60)

Methodology Applied

Scientific EffectOptical filtering: Filter (optical)

Implementation Method 2

measuring a spectral intensity distribution (M(Sd)) of the spectral notch (NC2) by varying the mirror gap (dFP) of the Fabry-Perot interferometer (100)

Methodology Applied

Scientific EffectFabry-Perot interference: Fabry-Perot Interferometer

Data Source

PatentUS10545049B2Method for stabilizing a spectrometer using single spectral notch

Publication Date: 2020.01.28 SPECTRAL ENGINES

AI summary

A method for determining spectral calibration data (λcal(Sd), Sd,cal(λ)) of a Fabry-Perot interferometer (100) comprises:forming a spectral notch (NC2) by filtering input light (LB1) with a notch filter (60) such that the spectral notch (NC2) corresponds to a transmittance notch (NC1) of the notch filter (60),measuring a spectral intensity distribution (M(Sd)) of the spectral notch (NC2) by varying the mirror gap (dFP) of the Fabry-Perot interferometer (100), and by providing a control signal (Sd) indicative of the mirror gap (dFP), anddetermining the spectral calibration data (λcal(Sd), Sd,cal(λ)) by matching the measured spectral intensity distribution (M(Sd)) with the spectral transmittance (TN(λ)) of the notch filter (60).