Improved synthetic-heterodyne Michelson interferometer vibrometer using phase and gain control feedback

Area of Science:

• Optics and Photonics
• Metrology and Measurement Science

Background:

• Synthetic-heterodyne demodulation is crucial for dynamic displacement and velocity measurement using interferometric sensors, offering immunity to drift.
• Conventional methods require knowledge of interferometer visibility and Bessel function arguments, complicating dynamic measurements.
• Advancements in real-time signal processing make complex interferometric signal analysis more feasible.

Purpose of the Study:

• To introduce a novel synthetic-heterodyne demodulation method that minimizes sensitivity to received optical power.
• To develop an expression for dynamic displacement and velocity less dependent on optical power variations.
• To enhance signal acquisition by compensating for non-ideal anti-aliasing filter responses using feedback loops.

Main Methods:

• Developed a new synthetic-heterodyne demodulation algorithm.
• Implemented independent phase and gain feedback loops to correct for anti-aliasing filter imperfections.
• Utilized the improved system to measure the dynamic characteristics of a Piezoelectric Mirror-Shifter (PMS).

Main Results:

• The new method yields dynamic displacement and velocity expressions with significantly reduced sensitivity to optical power.
• Feedback loops effectively compensated for non-ideal filter responses, improving signal acquisition.
• Experimental measurements of the PMS (200 Hz–9 kHz) showed excellent agreement with industry-standard calibration methods.

Conclusions:

• The proposed synthetic-heterodyne demodulation technique offers a more robust and simplified approach for dynamic displacement and velocity measurements.
• The system demonstrates high accuracy and reliability, validated against established calibration procedures.
• This advancement is valuable for precise metrology applications requiring dynamic motion analysis.