Ultrasonic holography free from phase turbulence

It is well known in the field of ultrasonic holography that the formation of a hologram is affected seriously by the presence of turbulence inside the medium in which ultrasonic waves propagate; especially in case of large phase turbulence, it becomes almost impossible to reconstruct the image from the hologram. In this paper, a principle of a new method of reducing the effect of the fluctuation on the detected hologram by using a stochastic processing of the signal is proposed. The basic idea is to estimate the mean values of the phase and the amplitude of the ultrasonic signal separately and then combine these two averaged values to get the ultrasonic signal which would be obtained in the absence of turbulence. By constructing models of a turbulent medium, the effect of this processing is studied and the result of computer simulation which demonstrates the usefulness of this method is presented. In addition, such usefulness is shown by the experimental result obtained by using a device which was constru...