Fast derivation of phase in computer-aided photoelasticity

Phaseshifting and spectral analysis techniques have been successfully implemented to yield the retardation phase from intensity modulated fringe patterns in computer-aided photoelasticity. In many tests, however, it is necessary to derive the retardation phase instantaneously as the birefringent model is subjected to loading. The direct use of existing phaseshift and spectral analysis schemes will not yield this result. In this paper, an alternative technique of object pre-load phaseshift followed by look-up-table programming on the image processing board is outlined and demonstrated to derive the measurements rapidly.