A method for measuring, in an extended range, the linear velocity of a movi
ng rough surface is proposed. To this end, two image speckle patterns origi
nated by the coherently illuminated surface are detected and processed as a
set of speckle sub-patterns, each one obtained from a partition of both de
tected intensity distributions along the motion direction. A quasi-real-tim
e fast spatial correlation operation between the speckle sub-patterns is ca
rried out in order to find the maximum correlation value. Its localisation
determines the velocity of the surface, while the shape of the correlation
peak allows to evaluate the uncertainty of the measuring procedure. An expe
rimental verification is performed to illustrate the feasibility of this ap
proach. (C) 1999 Elsevier Science B.V. All rights reserved.