Tomographic reconstruction of three-dimensional density fields using laser speckle photography and laser interferometry projections

The reconstruction accuracies of Fourier convolution (FC) and algebraic reconstruction technique (ART) are examined for laser speckle photography and laser interferometry. Computer synthesized phantoms are used to calculate asymmetric density fields for limited cases of 5 and 3 projections. To simulate experimental uncertainties, random noise levels are imposed on projected data before they are used for reconstruction. Experiments are also performed for a speckle photography system, a Mach-Zehnder interferometer, and an oxygen analyzer for a half-blocked nozzle and a two-hole nozzle to measure asymmetric helium density fields. Reconstructed density fields are calculated by the FC and the ART from projected data of the speckle photography and the interferometry. The reconstructed fields are compared with the results of the directly measured data using oxygen analyzer. The non-algebraic ART requires a modification for its use for laser speckle photography. Both the ART and the FC have been used for both non-algebraic speckle photography and algebraic interferometry. The present ART method shows a significant improvement in the reconstruction accuracy over the existing Fourier convolution (FC) method.