DEVELOPMENT OF PHASE RETRIEVAL TECHNIQUES IN DISPLACEMENT AND DISPLACEMENT DERIVATIVES MEASUREMENT

Abstract

This thesis proposes several novel techniques for full-field displacement and displacement derivatives measurement using coherent optical methods. A Teager-operator based algorithm called DHODA and a novel fringe orientation and density map based fringe analysis technique are proposed for phase derivatives determination. A derivative based simplified phase tracker model is proposed for phase demodulation from a single fringe pattern. In time-average speckle interferometry, novel amplitude varied refreshing reference frame technique is proposed to improve the contrast and visibility of a Bessel fringe pattern. A novel ensemble of hybrid genetic algorithm for two-dimensional phase unwrapping method, is also proposed for phase unwrapping of a noisy phase map. A method to determine material properties of a small cantilever beam using DSPI is also developed which overcomes the influence of rigid body movement in the out of plane displacement measurement. All methods are verified with numerical simulations and validated by experiments.