Adaptive feedback control in self-mixing interferometry using active optical elements

Abstract

A voltage-controlled liquid lens has been used as an adaptive optical element integrated in a conventional self-mixing interferometry setup. The lens is used to control the optical feedback level and the focus position of the laser beam enabling the system to find automatically the good measurement condition for vibration measurements. The system has been set to work in closed loop having as input the coupling coefficient of the self-mixing signal, and as control parameter the voltage of the liquid lens, enabling to enhance the measurement capabilities of the technique.