Application of three-beam holographic interferometry to the study of a thermal turbulent wake

Abstract

A Q-switch ruby laser supplying two pulses, has been used to carry out high speed holographic interferometry for the study of a thermal turbulent wake considered as a phase object. The duration of time separating the two pulses can be varied from 5 to 250 mu s. Using a hologram recorded in a parallel beam of light, one can obtain either lines of equal phase at a given instant of time or lines of equal phase shift between two close instants of time. The temperature fall and spread of the wake as a function of distance from the thermal source can be deduced from measurements made on interferograms with background fringes. In diffuse light, time differential interferograms have shown the existence of a threshold of detection for the smallest turbulences and give an aspect of the evolution of the wake in time.