Secondary envelope extraction based on multiple Hilbert transforms for laser self-mixing micro-vibration measurement

Area of Science:

• Optics and Photonics
• Measurement Science and Metrology
• Vibration Analysis

Background:

• Self-mixing interference (SMI) is a phenomenon in laser systems where light fed back from a target interferes with the laser source.
• Accurate reconstruction of micro-vibrations from SMI signals is challenging due to factors like optical feedback levels and fringe shifts.
• Existing methods often struggle with weak or moderate feedback regimes, limiting their applicability.

Purpose of the Study:

• To develop and validate a robust method for micro-vibration measurement using self-mixing interference.
• To address the limitations of current techniques in handling weak and moderate optical feedback.
• To enable accurate target motion displacement reconstruction irrespective of fringe shift effects.

Main Methods:

• A novel signal processing technique involving secondary envelope extraction and multiple Hilbert transforms is proposed.
• The method is applied to analyze self-mixing interference signals under varying optical feedback conditions.
• Simulations and experimental validations were conducted for micro-vibration measurements.

Main Results:

• The proposed method successfully reconstructs target motion displacement from self-mixing interference signals.
• Experimental results align with theoretical predictions across different optical feedback factors.
• The technique effectively mitigates the influence of fringe shifts on micro-vibration reconstruction.

Conclusions:

• The developed method offers a reliable approach for micro-vibration measurement in self-mixing interference systems.
• It demonstrates effectiveness in both weak and moderate optical feedback scenarios.
• This advancement enhances the precision and applicability of laser-based vibration sensing.