Deformation Method of Self-Mixing Laser Sensor’s Feedback Phase for Estimation of Optical Feedback Coupling Factor and Displacement

Junaid Iqbal Khan, Usman Zabit

Abstract: This paper, while focusing on post-perturbed phase processing of optical feedback based self-mixing laser displacement sensor, rigorously derives a general strategy to achieve the particular task of retrieving displacement from perturbed (feedback based) phase based on a proposition, which has been proved separately. From this, a new algorithm has been derived for estimation of optical feedback coupling factor and corresponding displacement over weak-, moderate-, and strong-optical feedback regimes, by using the concept of deformation. This method can work on all displacements so long as these are sufficiently smooth, i.e, have enough continuous derivatives. The algorithm's steps are shown to be mathematically consistent. Furthermore, its performance has also been verified, and compared with a previous method, by using simulated and experimental signals for an SM sensor with emission wavelength of 785 nm. Displacement measurement precision has also been quantified by using a commercial transducer with 2 nm resolution showing that the proposed method provides comparable displacement precision even for fringe-loss affected, strong-feedback regime signals.