Vibration induced phase-shift interferometer

Abstract

This paper presents the concept and the experimental setup of an interferometric system that is designed to work without vibration isolation and uses the random mechanical vibrations as phase shifter. An additional high temporal resolution detector system consisting of three photodiodes is used for the determination of the phase shifts that occur at the recording of the interference images. Two orthogonally polarized laser beams of different wavelengths, a continuous He-Ne laser and a pulsed laser diode, are coupled and expanded to the test and reference plates. To resolve the ambiguity problem of the profile orientation, additional information is obtained from the signals of two adjacent optical fibers placed in the He-Ne interference field. The laser beams are also split and expanded to a plate with tilted surfaces. The fringes that occur at the reflection on the surfaces are used to analyze the wavelength stability of the laser diode, taking the He-Ne wavelength as reference. An adequate PSI algorithm for random phase shifts is proposed.