Simultaneous registration of in- and out-of-plane displacements in modified grating interferometry

We recently presented a novel approach using high-sensitivity grating interferometry to measure in- and out-of-plane displacements. The interference of each of the specimen grating diffraction orders with the reference beam was recorded separately but not simultaneously. Computer subtraction and addition of the phase maps obtained from the interferograms yielded the in-plane and out-of-plane displacements (u and w). This article presents our continuing work with this interferometric setup, extending the application of this method to include the simultaneous registration of interferograms for analyzing time dependent events, The spatial separation of interferograms, accomplished by means of polarization techniques, allows for the simultaneous registration of interference patterns. The methods, employing two different sets of linear polarizations for the diffraction orders acid two different polarizing beamsplitting elements, are described, and the experimental results are presented, Further modifications for sequential and simultaneous monitoring of all three displacements u, v, and w are suggested. (C) 1997 Society of Photo-Optical Instrumentation Engineers.