Quadrature demodulation based on lock-in amplifier technique for self-mixing interferometry displacement sensor

Area of Science:

• Optics and Photonics
• Measurement Science and Metrology

Background:

• Self-mixing interferometry (SMI) is a technique for measuring displacement and vibration.
• Traditional SMI methods can face challenges with signal processing and accuracy, especially with diffuse targets.

Purpose of the Study:

• To propose and validate a new quadrature demodulation method for self-mixing interferometry.
• To enhance measurement precision and reliability, particularly for diffuse targets.

Main Methods:

• Implementation of a lock-in amplifier technique for quadrature demodulation.
• Utilizing sinusoidal phase modulation via an electro-optic modulator (EOM) in the external cavity.
• Theoretical analysis and simulation of the proposed method.

Main Results:

• The proposed method successfully calculates the real phase of the external target.
• Experimental validation demonstrates high-precision measurements for harmonic and arbitrary target motions.
• The technique proves effective even when applied to diffusive targets.

Conclusions:

• The developed lock-in amplifier-based self-mixing interferometry method offers a robust solution for precise phase demodulation.
• This approach significantly improves measurement accuracy and applicability to challenging targets.