Visualization of mode shapes in piezoelectric devices using two-dimensional correlation filter

The method described here, based on laser speckle interferometry, applies a two-dimensional correlation filter to speckle image data for driven and resting phases, to visualize the mode shapes of piezoelectric devices. Laser speckle interference, a periodic resonator excitation, charge coupled device (CCD) image captures and correlation filtering are effectively combined in this method. Even with a small amount of data, this method gives very clear, high-contrast mode shape images. We also show that both in-plane and out-of-plane vibrational images can easily be separated by choosing the proper incident angle of a collimated laser beam. We used a fully plated, rectangular AT-cut quartz resonator and a partially plated circular AT-cut quartz resonator to demonstrate the proposed method. The experimental results show that this method effectively visualized the mode shapes of the resonator in a short time.