FAST ELECTROOPTICAL SYSTEM FOR PULSED ESPI CARRIER FRINGE GENERATION

Pulsed Electronic Speckle Pattern Interferometry (ESPI) offers the pos sibility of analysing fast transient phenomena in experimental mechani cs. However, due to the short pulse separation required, addition frin ges with very low visibility are generated. Several methods have recen tly been developed to process these data but they all suffer some limi tations. This paper presents an electro-optical system based on the us e of a Pockels cell which enables the introduction of carrier fringes between the firing of two consecutive laser pulses. This allows calcul ation of the wrapped phase distribution from a single fringe pattern u sing the Spatial Synchronous Detection method and enables the laser pu lse separation to be significantly reduced. Preliminary experimental m easurements performed using a continuous wave laser are used to illust rate the performance of this approach.