Phase-stepped additive stroboscopic fiber optic TV holography for vibration analysis

Abstract

A novel technique for out-of-plane vibration analysis combining synchronous phase-stepping with additive stroboscopic TV holography and its implementation on a fiber optic electronic speckle pattern interferometer (FOESPI) are presented. Stroboscopic pulse-to-pulse (high frequency) as well as TV frame-to-frame (low frequency) phase-stepping of the reference arm are combined, with this scheme position of additive fringes is shifted yielding a series of frames (correlograms) which are then processed using conventional phase-stepping algorithms to obtain a phase-map of the vibrating object. A restriction of this technique, taking only two contrast-inverted correlograms for sequential subtraction, is also demonstrated for real-time visibility enhancement of additive fringes.