Theoretical analysis for moiré effect of circular gratings for volume optical computerized tomography

Obtaining the radial derivatives of wavefronts in projections is a critical step for volume optical computerized tomography. In this paper, the moire effect of two identical circular gratings in acquiring the first-order radial derivative of a wavefront is analyzed. Based on scalar diffraction theory, the formation mechanism of circular gratings’ moire fringes is derived. A more explicit analytical relation between moire fringes of different diffraction orders and tested wavefront is obtained. The involved results will be useful for extracting the projection information that is used in three-dimensional reconstruction by volume OCT.