Effects of diffraction and nonlinear photographic emulsion characteristics on the performance of deferred electronic heterodyne moiré deflectometry are investigated. The deferred deflectometry is used for measurements of nonsteady phase objects for which it is difficult to complete the analysis of the field in real time. The sensitivity, the accuracy, and the resolution of the system are calculated, and it is shown that they are weakly affected by diffraction and by nonlinear recording. The features of the system are significantly improved compared with those of the conventional deferred intensity moiré technique and are comparable with those of the on-line heterodyne moiré. The system was evaluated experimentally by deferred measurements of the refractive-index gradients of a weak phase object consisting of a large KD*P crystal. This has been done by photographing the phase object through a Ronchi grating and analyzing the transparency with the electronic heterodyne readout system. The results are compared with the measurements performed on the same phase object with on-line heterodyne moiré deflectometry and with heterodyne holographic interferometry methods. Good agreement was observed. Some practical considerations for system improvement are discussed.
© 1987 Optical Society of AmericaFull Article | PDF Article
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