Digital carrier superposition by Hilbert–Huang transform for optical phase recovery in speckle shearing interferometry

Abstract

Industrial production constraints often require technical tests and controls. Optical metrology methods allow a non destructive test of wide range of parameters, such as defects and displacements, with very good accuracy. The phase retrieval is an effective way that allows three-dimensional profile reconstruction from intensity shearograms. This research work focuses on the extraction of the phase from one uncarrier shearogram using the Hilbert-Huang transform. An algorithm for the phase calculation based on the bidimensional empirical mode decomposition, Hilbert transform (HT), and Fourier transform (FT) is presented. A spatial digital carrier has been superimposed before the application of the FT or HT which uses two π 2 shifted shearograms, to get access to the phase map via a global analysis of intensity images. An evaluation was made through a numerical simulation to validate and confirm the performance of the proposed algorithm. The main advantage of this technique is its ability to provide a metrological solution for fast dynamic analysis.

Digital Shearography for NDT: Phase Measurement Technique and Recent Developments

“…At the same time, however, some limitations exist for digital shearography, and research in the past few years has Based on the above introduction, the two methods are summarized in Table 2. In recent years, some new phase extraction algorithms and optimizations have been proposed [36][37][38][39]. In 2014, Albertazzi et al proposed an alternative approach for retrieving phase information from a sequence of images with unknown phase shifts [40].…”