All digital sliding mode observer of a feedback-free interferometer for high dynamic range detection.

Area of Science:

• Optics and Photonics
• Control Systems Engineering
• Metrology

Background:

• Traditional interferometry often requires complex optical setups and feedback mechanisms for accurate phase detection.
• Open-loop interferometers typically lack the precision and dynamic range needed for complex displacement measurements.

Purpose of the Study:

• To present a passive interferometry phase detection method that emulates closed-loop techniques using digital control.
• To enable demodulation of optical phase in feedback-free interferometer hardware.
• To measure complex displacements with enhanced accuracy and robustness.

Main Methods:

• Development of an all-digital closed-loop observer based on variable structure and sliding modes nonlinear control theory.
• Implementation of a passive interferometry system without feedback phase modulators or reset circuits.
• Conducting a proof-of-concept experiment measuring displacements from a piezoelectric actuator.

Main Results:

• Successful demodulation of optical phase in an open-loop, feedback-free interferometer.
• Measurement of complex displacements, including both magnitude and angle.
• Demonstrated simplification of optical hardware compared to traditional methods.
• Achieved increased dynamic range and high robustness in phase detection.

Conclusions:

• The presented passive interferometry method offers a simplified yet effective approach to optical phase detection.
• This digital observer-based technique enhances interferometer performance, eliminating the need for feedback components.
• The method shows significant potential for precise complex displacement metrology.