Development of Spatial and Temporal Phase Evaluation Techniques in Digital Holography

Abstract

This thesis is to develop new spatial and temporal phase evaluation techniques in digital holography, and to overcome the existing problems in some applications with digital holographic technique. In the spatial domain, a novel method using the concept of complex phasor is proposed to determine the phase difference map (or wrapped phase map). Not only a deformation distribution is obtained, but higher-order displacement derivatives are also determined. In addition, in the spatial domain, a new algorithm using an advanced analysis approach is also proposed to effectively and accurately estimate the fringe density which can facilitate the subsequent filtering operation and phase unwrapping. In the temporal domain, an improved short-time Fourier transform is proposed to process a series of reconstructed phase maps pixel by pixel. In this case, continuous deformation of a cantilever beam and profiling of an object with height steps are studied. In addition, several new methods for the detection and compensation of phase-shifting errors in phase-shifting digital holography are also proposed. In some applications with digital holographic technique, extended depth of focus for a particle field, complex-valued object reconstruction and optical image encryption are investigated. The research work in this thesis can contribute to a better understanding of digital holographic principles, and may also shed some light on the further development of digital holography in practical applications.