Interferometric measurements of nanometric displacements in a Piezoelectric Flextensional Actuator by using the new J1…J5 method

In this work, nanometric displacement amplitudes of a Piezoelectric Flextensional Actuator (PFA) designed using the topology optimization technique and operating in its linear range are measured by using a homodyne Michelson interferometer. A new improved version of the J₁...J₄ method for optical phase measurements, named J₁...J₅ method, is presented, which is of easier implementation than the original one. This is a passive phase detection scheme, unaffected by signal fading, source instabilities and changes in visibility. Experimental results using this improvement were compared with those obtained by using the J₁...J₄, J₁...J₆(pos) and J₁...J₆(neg) methods, concluding that the dynamic range is increased while maintaining the sensitivity. Analysis based on the 1/f voltage noise and random fading show the new method is more stable to phase drift than all those methods.