Speckle decorrelation influence on measurements quality in vortex metrology

LUCIANO ANGEL TORRO; DANIEL SIERRA SOSA; MYRIAN TEBALDI; NESTOR BOLOGNINI

OPTICS COMMUNICATIONS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2012 vol. 285 p. 4312 - 4316

0030-4018

We study speckle decorrelation effects in connection with conventional vortex metrology techniques. Our proposal is based on processing speckled images recorded by using two different experimental set- ups. In both schemes two laterally displaced patterns are generated: one scheme allows for obtaining undecorrelated speckle distributions and the other for decorrelated ones. Vortex networks associated with speckle patterns are analyzed by employing the usual tools developed for vortex metrology. For each  recorded image, a 2D pseudo-phasemap is generated on the basis of the Reisz transform. Then the vortices are located, and parameterized in terms of their topological charge, eccentricity, vorticity and angles between the zero crossing lines from the real and the imaginary parts of the analytical signal. After tracking the homologous vortices onto the maps, the histograms corresponding to the coordinate displacements are analyzed. We show that histograms interpretation is prone to failure due to its high sensitivity to decorrelation. Experimental evidences are presented to support there strictions imposed by decorrelation of actual speckles due to uniform in-plane displacements.