Absolute Vibration Displacement of Piezoelectric Resonators on Polished Surfaces Measured using Laser Speckle Interferometer

We investigated the absolute vibration displacement of a piezoelectric resonator on a polished surface measured using a laser-speckle interferometer. There are various types of piezoelectric resonators, and crystal resonators are mainly used in mobile phones. Laser-speckle interferometry can simplify devices by using a CCD camera, instantly capture an image, and visualize in-plane vibration in about 20 seconds for all pixels. There have been papers on methods for measuring polished surfaces, and we present a development method that uses ultraviolet rays and a correlation function for a laser light source. This method is superior in that the angle of incidence can be freely selected, whereas the angle of incidence must be constant with other methods because an ultraviolet laser is used.