Estimation of absolute distance and high-frequency vibration from the modulated SM-OFI signal using compound mutated genetic algorithm

Abstract

Contactless measurement of absolute distance or high-frequency vibration is a prominent factor for many industrial & scientific applications like predictive maintenance, non-destructive testing, and reverse engineering, etc. In recent years, self-mixing optical feedback interferometry (SM-OFI) has proven its superiority over other conventional optical methods because of its simple, compact and less expensive structure. Typically, the extraction of the sensing parameters from the modulated SM-OFI signal relies on the analysis of interferometric fringes that often leads to a non-optimal solution for weak feedback conditions. In this paper, the authors introduce a novel method to process the SM-OFI signal that employs a multi-objective compound mutated genetic algorithm to search for optimum solutions. To the author's knowledge, this is the first attempt to measure the vibrating frequency and the absolute distance between the laser-diode front facet and the vibrating target, simultaneously using a multi-objective global optimization method instead of frequency analysis. The validity of the proposed method was experimentally tested on a vibrating object located 2 to 20 cm away from the laser diode and having a vibration frequency between 2 and 10 kHz. The proposed method exhibits an excellent accuracy of 1% & 0.98% with an SNR of 42 dB & 19 dB for absolute distance & vibration-frequency measurement, respectively. The method also possesses a resolution of 0.6 mm during absolute distance measurement and a percentage of error ranging between 2.3 to 8% during high-frequency vibration measurement, both under the weak feedback conditions. The comparison with other methods also supports the potential of the proposed method for the applications where absolute distance and frequency of the vibrations are required to measure simultaneously.