PHASE-MEASURING FIBER OPTIC ELECTRONIC SPECKLE PATTERN INTERFEROMETER - PHASE STEP CALIBRATION AND PHASE DRIFT MINIMIZATION

A phase-measuring fiber optic electronic speckle pattern interferometer (ESPI) was recently constructed and demonstrated. In this arrangement, phase stepping is introduced by stretching the fiber wrapped around a piezoelectric transducer. Calibration of the phase step is critical in phase measurement techniques for obtaining good phase plots. Methods used for calibrating the stretcher are outlined and the drifts in the phase caused by fluctuations in temperature and mechanical stresses are discussed. Ways to minimize this drift are also presented.