MEASUREMENT OF MINUTE VIBRATIONAL DISPLACEMENT BY MEANS OF LASER INTERFEROMETER COMPOSED OF OPTICAL DIRECTIONAL-COUPLER.

A measurement system for minute vertical vibrational displacement has already been developed by the laser interferometer. This system is applied to an investigation regarding the vibrational mode of quartz crystal resonators. In a system mentioned in this paper, an optical directional coupler is adopted for simplifying the optical system as well as for minimizing fluctuation. Moreover, two dimensional measurement can be carried out easily and accurately by means of computer aided fine adjustment stages. In this system, the obtained resolution is reached to 0. 02 Angstrom. The experimental results are shown concerning quartz crystal resonators, for example, an X cut bar (f//s equals 64 kHz), a CT cut (f//s equals 154 kHz) and a DT cut (f//s equals 103 kHz) rectangular plates, respectively.