Applying the pulse laser to speckle methods, nonuniformities of the laser beam profiles and the intensities between each laser pulse have unpleasant consequences on the intensity distribution of the recorded images and following on the expected fringes of the corresponding subtractive result. This contribution introduces a computer based technique for compensating this technical and physical problem, so that the fringe quality is improved, even if the homogeneity of the laser beam profiles is on such low level, that the conventional (subtractive) technique fails. The solution is based on algorithms, which refines each intensity distribution and is comparable with the known shading correction. After this refinement the interferogram can be processed by the well known Fourier transform evaluation of the relative phase distribution. Applying the FFT, practical problems arise when it comes to the step of automatic sign corrections. The contribution will discuss an approach of automatic sign correction. The methods for refinement and automatic sign correction following the Fourier transform evaluation is explained in detail and demonstrated on selected interferograms.

Date Published: 21 September 1999
PDF: 11 pages
Proc. SPIE 3824, Optical Measurement Systems for Industrial Inspection, (21 September 1999); doi: 10.1117/12.364246

Published in SPIE Proceedings Vol. 3824:
Optical Measurement Systems for Industrial Inspection
Malgorzata Kujawinska; Wolfgang Osten, Editor(s)