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 J
₁
...J
₄
method for optical phase measurements, named J
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...J
₅
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 J
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...J
₄
, J
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...J
₆
(pos) and J
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...J
₆
(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.