Quadrature signal construction by vector composition for laser self-mixing interferometry.

Area of Science:

• Optics and Photonics
• Metrology and Measurement Science
• Signal Processing

Background:

• Laser self-mixing (SM) interferometry is crucial for ultra-precise measurements.
• Traditional quadrature phase unwrapping methods (QPUM) require strict quadrature signals, and mismatches introduce errors.
• Existing methods face challenges with signal accuracy and computational efficiency.

Purpose of the Study:

• To present a novel vector composition quadrature construction algorithm for SM signals.
• To enable strictly quadrature signal construction using simple addition and subtraction operations.
• To improve the accuracy and efficiency of SM interferometry measurements.

Main Methods:

• Developed a vector composition algorithm for constructing quadrature signals from two SM signals with a phase shift.
• Implemented and tested the algorithm in a multi-longitudinal laser SM phase-shifting generation system.
• Validated the method through experimental and simulation studies, including conditions with speckle interference.

Main Results:

• Achieved a displacement reconstruction error of 65 nm for a non-stationary target with 3.193 µm peak-to-peak displacement.
• Demonstrated significant reduction in computational cost, requiring only 1/34.2 of the time of conventional methods (97% reduction).
• The algorithm shows robustness against speckle interference.

Conclusions:

• The vector composition algorithm provides simple, efficient, and accurate quadrature signal construction for SM interferometry.
• This technique offers computational simplicity, rapid processing, precise phase shifting, speckle immunity, and zero calibration.
• It is an ideal solution for robust, high real-time SM demodulation in online measurements and low-power applications.