Time-Resolved Oblique Incident Interferometry for Vibration Analysis of an Ultrasonic Motor

This paper presents a technique that employs a stroboscopic oblique-incidence interferometer to visualize the motion of a vibrating object with a rough surface. An oblique-incidence interferometer is well suited to the analysis of a rough surface and micro displacement because light-scattering is reduced when a surface is rough. However, when continuous light is used, the fringe pattern on the vibrating surface in the ultrasonic region can not be observed for the analysis of a micrometer resolution profile. To overcome this problem, pulsed light synchronized with a vibrating sample is employed as a light source using an acousto-optic modulator (AOM). The timing between the vibrating sample and the observation light is controlled using a common oscillator, so that the time-resolved behavior of the stator can be measured. We successfully detect the periodic movement of a fringe pattern for a vibrating ultrasonic motor using the interferometer.