Double pulse-electronic speckle interferometry (DP-ESPI)

For the measurement of vibrations using double-pulse techniques, pulses separations between 1 and 1000 microseconds are necessary. Until now double-pulsed holographic interferometry has been extensively used to measure vibrations. This method has the disadvantage that it needs the recording and the reconstruction of a hologram. For the recording a photographic plate or a thermo-plastic camera is usually used. The hologram is then reconstructed usually with a continuous laser and viewed with a CCD camera. This process is time consuming. Double pulsed ESPI [1] enables to obtain correlation fringes corresponding to the displacement without recourse to any form of photographic processing and plate relocation.