De-correlation Effects in Speckle-pattern Interferometry

A theoretical analysis of de-correlation effects in plane strain sensitive speckle-pattern interferometry is presented. Experimental results supporting the theoretical model are summarized and it is shown that in-plane translations and out-of-plane rotations typically of order 102 μm and 10-3 radians respectively may be tolerated before fringe visibility becomes unacceptable. The results also indicate how the interferometer may be optimized. Interferograms which show the strain fields resulting from machining are presented.