Michelson interferometer vibrometer using self-correcting synthetic-heterodyne demodulation.

Area of Science:

• Optical Metrology
• Signal Processing
• Interferometry

Background:

• Synthetic-heterodyne demodulation offers drift-immune dynamic displacement and velocity detection in interferometric sensors.
• Advancements in real-time signal processing make complex interferometric signal analysis more feasible.
• Accurate dynamic measurements require knowledge of interferometer visibility and Bessel function arguments.

Purpose of the Study:

• To present a method for determining interferometer visibility and setting Bessel function arguments for maximum sensitivity in synthetic-heterodyne demodulation.
• To develop a demodulation technique independent of the unknown phase difference between local oscillators and the interferometric signal.
• To validate the proposed method through experimental measurements of a piezoelectric mirror shifter.

Main Methods:

• A novel synthetic-heterodyne demodulation approach utilizing two additional quadrature local oscillators.
• Implementation of a Michelson interferometer with a sinusoidally modulated visible single-mode laser.
• Real-time signal acquisition using a 250 kHz analog-to-digital converter and subsequent processing.

Main Results:

• The proposed method yields a demodulated signal independent of the phase difference between local oscillators.
• Experimental measurements of displacement sensitivity, frequency response, and linearity were performed.
• Results demonstrated good agreement with independent validation techniques, including the signal coincidence and n-commuted Pernick method.

Conclusions:

• The developed synthetic-heterodyne demodulation technique enhances accuracy and simplifies dynamic displacement measurements.
• The use of quadrature local oscillators effectively eliminates phase ambiguity, improving system robustness.
• This method provides a reliable approach for precise vibration analysis in interferometric sensing applications.