Non-linear speckle phase changes in the image plane caused by out of planedisplacement

The speckle phase changes which occur in the image plane when the illuminat ed object is displaced along the optical axis are investigated. This is don e by means of simulations and measurements. The object displacement is divi ded into a number of smaller displacement steps and by simulating the speck le phase for each step the behaviour of the phase can be visualized. It is shown how phase singularities arise and disappear during the displacement. These results obtained by numerical generation of the speckle phase are ver ified experimentally. The physical model used for the generation of subject ive speckle fields as well as the experimental setup are described. (C) 199 9 Published by Elsevier Science B.V. All rights reserved.