We propose a simple real-time system and demonstrate its use for measuring dynamic optical phase perturbation. In this system we used a 0.1-wt.% Fe:LiNbO3 to record the self-interference grating with incident light. The system is a new kind of real-time holographic interferometer. After rise time in the interferometer, the speed for showing the fringes is as fast as that of dynamic phase perturbations. Characteristics of the interferometer are proposed and examined. (C) 1997 Optical Society of America.