Sub-λ/2 Displacement Sensor With Nanometric Precision Based on Optical Feedback Interferometry Used as a Non-Uniform Event-Based Sampling System

Abstract : In this paper, a method based on the inherent event-based sampling capability of the laser optical feedback interferometry (OFI) is proposed to recover sub-λ/2 displacement with a nanometric precision. The proposed method operates in open-loop configuration and relies on OFI's fringe detection, thereby improving its robustness and ease of use. The measured white noise power spectral density is less than 100 pm/ √ Hz with a corner noise frequency of approximately 80 Hz for a laser diode emitting wavelength λ0 of 785 nm placed at 30 cm of the target.