Extraction of interference phase in frequency-scanning interferometry based on empirical mode decomposition and...

Area of Science:

• Optics
• Metrology
• Signal Processing

Background:

• Nonlinear optical frequency scanning in tunable lasers introduces significant errors in frequency scanning interferometry.
• Inaccurate phase extraction from interference signals limits the precision of optical measurement systems.
• Existing methods struggle to fully compensate for the detrimental effects of frequency scanning nonlinearity.

Purpose of the Study:

• To develop a robust phase-extraction algorithm for frequency scanning interferometry.
• To effectively mitigate the impact of nonlinear optical frequency scanning on measurement accuracy.
• To enhance the precision of interference signal phase extraction in tunable laser systems.

Main Methods:

• Proposed a novel phase-extraction algorithm integrating empirical mode decomposition (EMD) and Hilbert transformation.
• Utilized EMD to decompose the interference signal into intrinsic mode functions.
• Applied Hilbert transformation to extract the instantaneous phase, effectively removing nonlinear scanning influences.

Main Results:

• The proposed algorithm successfully eliminated the influence of optical frequency scanning nonlinearity.
• Simulations and experimental verifications confirmed the method's validity and stability.
• Achieved a single-cycle relative phase error of 0.6% and a standard deviation of 0.7 μm at a 5 MHz sampling rate.

Conclusions:

• The EMD and Hilbert transformation-based algorithm provides a significant advancement in accurate phase extraction for frequency scanning interferometry.
• This method offers a reliable solution for improving measurement precision in systems employing tunable lasers.
• The demonstrated improvements in relative error and standard deviation highlight the practical utility of the developed algorithm.