Profiling of an object using a time-frequency analysis method in digital holographic interferometry

Abstract

In recent years, temporal analysis methods have become popular in the processing of fringe patterns. In the conventional temporal phase unwrapping method, each pixel is processed independently of other pixels. Thus good data can be effectively preserved. However, the errors may still accumulate along the time axis for the bad data. In this paper, a timefrequency analysis method i.e., short time Fourier transform (STFT) algorithm, is employed to process wrapped phase maps in digital holographic interferometry (DHI). In the proposed STFT method, phase unwrapping operations are effectively avoided in both spatial and temporal domains and the errors along the time axis can be more effectively suppressed. In addition, the continuous phase distributions obtained can characterize the shape of a test object. An experiment is conducted to show the validity of STFT algorithm in DHI. © 2009 SPIE.