Variable grid decomposition for ill-posed interferometric tomography: Comparison of algorithms

Abstract

An algorithm, termed the variable grid method (VGM), has been developed to provide enhanced reconstruction by interferometric tomography under the ill-posed problems of restricted angular scanning and incomplete projection that frequently arise in flow measurements. The algorithm is based on variable grid decomposition of a field. The performances of the two versions of the VGM are compared to investigate the effects of the redundancy criteria in generating variable grid elements. Performance comparison is also made with a conventional fixed grid method. The testing is conducted through computer simulation of experiments and reconstruction with a known three-dimensional field that has been produced by computational fluid dynamics. The reconstruction through computer simulation demonstrates the superiority of the two VGMs to the conventional method. Both the maximum and average reconstruction errors are reduced appreciably. The VGM version with stricter parameter contro performs best. The technique can reflect spatial information contained in measured data. Thus, improvement is noticeable in the regions with dense scanning of probing rays. These regions are usually of interest in engineering applications.