Development of optical phase evaluation techniques: Application to fringe projection and digital speckle measurement

Abstract

This thesis proposed optical phase evaluation techniques that covered three stages of the optical fringe analysis process, namely wrapped phase extraction, phase quality identification, and post-processing of an unwrapped phase map. The proposed techniques were applied on fringe projection and digital speckle measurement. They provided solutions to existing problems, such as simplification of the data-recording process, discontinuous surface profile measurement, automation enhancement of digital filtering algorithms, and elimination of nonlinearity in phase-to-height conversion. Mathematical principles including phase-shifting, least squares method, continuous wavelet transform, and series analysis were used in the theoretical development. Validity and reliability of the reported algorithms were tested on various specimens. It was concluded from the results that the proposed phase evaluation techniques could facilitate an advanced integration of optical metrology with computer technology.