  The effect of a random phase diffuser on fluctuations of laser light
(scintillations) is studied. Not only spatial but also temporal phase
variations introduced by the phase diffuser are analyzed. The explicit
dependence of the scintillation index on finite-time phase variations is
obtained for long propagation paths. It is shown that for large amplitudes of
phase fluctuations, a finite-time effect decreases the ability of phase
diffuser to suppress the scintillations.
