Fast, mems-based, phase-shifting interferometer

Abstract

We demonstrate a MEMS-based, phase-shifting interferometer (MBPSI) that is much faster than conventional phase-shifting interferometers (PSI). For phase shifting, our system employs a comb-driven vertically resonating micromachined mirror illuminated by synchronized laser pulses (y=660nm). Our MBPSI employs a four-frame phase-shifting technique (four CMOS-imager frames per one profile measurement), at a rate of 23 profile measurements-per-second (23Hz, 43.5msec per measurement). At this rate, the MBPSI can continuously capture more than 500 profile measurements of a transient phenomenon over 21.7 seconds. The MBPSI in Twyman-Green configuration has accurately tracked in real time the fast-changing, transient motion of a PZT actuator, within +y/110 (+6nm).