Abstract
Volume optical computerized tomography (VOCT) combining moiré deflectometry is superior in studying the spatial characteristics of flow field for its strong anti-disturbing capability, wide measurement range and three-dimensional (3D) measurement. However, 3D filtered back-projection (FBP) reconstruction algorithm of reconstructing the refractive index distribution requires the radial second-order derivative of projection wave front. Taking it into account, the moiré effect of two identical concentric circular gratings is utilized to obtain the radial first-order derivative of wave front directly. Besides, based on the explicit analytical relation between moiré fringes and tested wave front, a modified Fourier-transform method is applied to extract the wave front's radial first-order derivative from moiré fringes. These methods are approved efficient by measuring the 3D refractive index distribution of an axial symmetry flame.
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