Video-based vibration analysis using projected fringes

We analyze the sensitivity of a video-based moiré technique used to measure vibrations. By use of modulated projected fringes, full-field distributions are mapped for both the vibration amplitude and the vibration phase. We also show methods for visual interpretation of the vibration fringe pattern, and we describe phase-stepping algorithms for full-field calculations of the distributions by use of digital image-processing equipment. Implementation of these methods makes it possible to measure vibration amplitude and phase over a large range of amplitudes, from < 1 µm to several millimeters. We show that the method bridges the traditional gap between holographic interferometry and moiré methods.