Improvement of a glass integrated optical displacement sensor interferometer using acousto-optic effect

摘要

Optical interferometer displacement sensors are well known for their high resolution, up to 10~(-7) m in a stabilized environment, over a wide measuring range which can reach several metres. Moreover, the measurements are carried out without any mechanical contact with the target object. Two optical outputs are however needed to determine the displacement sign. A glass integrated sensor with only one optical output that still measures the displacement sign is proposed here. It is derived from a Michelson interferometer but is realized by ion exchange on a glass substrate. A piezoelectric element placed over the reference arm produces a longitudinal acoustic wave that creates a small phase modulation in the reference light beam at a high frequency (1.28 MHz). A small modulation of the output signal is thus produced. The direction determination is based on the comparison between the phases of the excitation acoustic signal and of the high frequency part of the sensor's output signal after proper signal processing. A theoretical and an experimental demonstration of that principle are presented. A precision of 158 nm was obtained with simple numerical signal processing.