A selective diffraction order based lens plane grating shearing interferometer for the study of bent plates

A simple, elegant and flexible technique for the determination of partial slope, curvature and twist contours of bent plates is proposed. A single frequency cross‐grating (SFCG) placed just ahead of the field lens collects the light reflected by the smooth plate model. From the resultant diffraction pattern formed at the Fourier transform (FT) plane, based on the desired contours, only a few orders are permitted selectively to pass through to the recording plane. This manner of real time in‐situ filtering of the diffraction orders is new. While slope contours require double exposures, curvature and twist contours are obtained from single exposures. © 1987 Blackwell Publishing Ltd