Robust laser self-mixing displacement demodulation via continuous wavelet-Hilbert transform for high-precision...

Area of Science:

• Metrology and Instrumentation
• Optical Physics
• Signal Processing

Background:

• Laser self-mixing grating interferometers offer compact, accurate accelerometer calibration.
• High line density gratings (4700 l/mm) create signal outliers, hindering conventional demodulation.
• Phase jumps and noise complicate displacement demodulation in interferometric systems.

Purpose of the Study:

• To develop a robust displacement demodulation algorithm for laser interferometry under high-noise conditions.
• To enhance the accuracy of accelerometer calibration using Cr gratings.
• To overcome limitations of derivative-based methods in dense grating interferometry.

Main Methods:

• A hybrid algorithm combining continuous wavelet transform and Hilbert transform was developed.
• The algorithm was applied to demodulate interferometric signals from Cr gratings.
• Experimental validation was performed using a commercial MEMS accelerometer.

Main Results:

• The hybrid algorithm achieved robust displacement demodulation despite dense grating outliers.
• 100 data segments were successfully demodulated with a high fitting goodness (R²=0.9964).
• Derived accelerometer sensitivity showed a minimal deviation of 0.1% from the nominal value.

Conclusions:

• The proposed hybrid algorithm enables high-accuracy dynamic calibration of inertial sensors.
• This method provides a paradigm for field applications requiring precise sensor measurements.
• The technique effectively addresses noise and phase jump issues in grating interferometry.