Fast electro-optical system for pulsed ESPI carrier fringe generation

Pulsed Electronic Speckle Pattern Interferometry (ESPI) offers the possibility of analysing fast transient phenomena in experimental mechanics. However, due to the short pulse separation required, addition fringes with very low visibility are generated. Several methods have recently been developed to process these data but they all suffer some limitations. This paper presents an electro-optical system based on the use of a Pockels cell which enables the introduction of carrier fringes between the firing of two consecutive laser pulses. This allows calculation of the wrapped phase distribution from a single fringe pattern using the Spatial Synchronous Detection method and enables the laser pulse separation to be significantly reduced. Preliminary experimental measurements performed using a continuous wave laser are used to illustrate the performance of this approach.