The Development and Applications of Amplitude Fluctuation Electronic Speckle Pattern Interferometry Method

In vibration measurement, traditional time averaged (TA) electronic speckle pattern interferometry (ESPI) method was essentially used for obtaining modal shapes rather for quantitative analysis. In 1996, the authors first reported that the driving force acting on the specimen would be fluctuated due to environmental disturbances and vibration fringe patterns obtained by TA ESPI method can be significantly improved if both the reference and object images were captured under vibration load. This new TA ESPI method was named as amplitude fluctuation (AF) ESPI method. In this paper, the development and successive improvement of the AF ESPI method was first introduced. The effects of environmental noise and vibration characteristics on the ESPI fringe pattern were then investigated. Theoretical derivation on the effect of environmental noise was performed and the time varying brightness of the traditional time averaged (TA) ESPI fringe patterns was successfully explained. In addition, applications of the AF ESPI method were briefly reviewed.