Open AccessHigh precision displacement-measuring interferometer based on phase modulation technique and modulation index effect elimination
Author(s) -
Vu Thanh Tung,
Vu Toan Thang
Publication year - 2020
Publication title -
iop conference series. materials science and engineering
Language(s) - English
Resource type - Journals
eISSN - 1757-899X
pISSN - 1757-8981
DOI - 10.1088/1757-899x/715/1/012086
Subject(s) - interferometry , optics , modulation index , physics , modulation (music) , phase modulation , astronomical interferometer , interference (communication) , michelson interferometer , amplitude modulation , interferometric visibility , signal (programming language) , frequency modulation , harmonics , laser diode , laser , voltage , pulse width modulation , acoustics , radio frequency , phase noise , telecommunications , channel (broadcasting) , quantum mechanics , computer science , programming language
A high precision displacement-measuring interferometer based on a phase modulation technique was developed. A PZT actuator was utilized to drive a mirror of a Michelson interferometer by applying a sinusoidal voltage to the PZT controller. The path difference between two arms of the interferometer was modulated leading to modulation in the phase of the interference signal with a frequency of 3 kHz. The first and second harmonics of the interference signal were detected at the modulation index of 2.63 rad, a special value when the values of the first and second orders of Bessel function are equal. The displacement was determined by the ratio of the first and second harmonic in which the effects of modulation index instability and intensity fluctuation were neglected. The phase modulation interferometer using a PZT actuator has no amplitude modulation effect compared with other modulation interferometers using EOM (electro-optics modulator) or modulation the injection current of a laser diode. Moreover, the direction of the displacement that was ambiguous of the traditional interferometers was clarified in a real time. A measurement precision of 60 nm was obtained using the phase modulation interferometer.