Mechanical vibration measurement by high-resolution time-averaged digital holography

摘要

In digital holography, a challenge inherited from speckle interferometry is the quantitative data processing of time-averaged holograms in view of estimating the full field of vibration amplitudes. Fundamentally, the greatest obstacle comes from the orthogonal components of time-averaged digital holograms, corrupted by multiplicative, high-frequency phase noise covering the deterministic vibration-related phase. The paper describes a novel method of obtaining through digital holography high-resolution time-averaged fringe patterns. The three-level approach includes the elimination of the multiplicative high-frequency phase noise by synchronous detection followed by low-pass filtering. The high-frequency information needed by this procedure is taken from the digital hologram of the object at rest. The complete procedure includes an automatic correction of the environmental phase drift introduced by the synchronous detection. The different stages of data processing are illustrated by experimental results.