Improvement of precision of self-mixing displacement sensor based on region tracking for large displacement

Abstract

Although it appears that there have been made enough researches as regards the estimation the optical feedback factor C of a self-mixing interferometer, any method of the C estimation cannot ensure its reliability if the operation of the self-mixing displacement sensor covers the strong feedback regime with fringe loss due to large displacement of a target. That is the main reason why the precision of the sensor degenerates for the measurement of large displacement. In the paper we propose a novel C estimation method called region tracking for the C value, which is indispensable for the measurement of long-range displacement, and demonstrate its fidelity experimentally. The experimental results in the paper were given when the target distance was about 60 cm and the target displacement 25 mm. The displacement reconstruction based on the proposed region tracking method ensures a better precision than a half wavelength, depending on the method of displacement retrieval. The approach presented will make a great contribution to further improvement of the accuracy of the self-mixing displacement sensor for large displacement.