A slice-integral method for calculating wave propagation through volumetric objects, and its application in digital holographic tomography

A novel slice-integral (SI) method to investigate wave propagation in three-dimensional (3D) volumetric objects, and its application in tomographic image formation in digital holographic microscopy is proposed. The SI method simplifies 3D volumetric objects as compositions of a series of thin slices, to calculate optical wave propagation through thick specimens, based on the Born approximation. A comparison of transmitted wave propagation for tomographic image reconstructions for specimens with different sizes and refractive index (RI) contrasts, based on the SI and the finite-difference time-domain (FDTD) methods, is given and analyzed. Simulation results show that the SI method performs tomographic reconstruction more conveniently than that using the FDTD method, especially for specimens with diameters smaller than the illumination wavelength. The sampling grid condition based on the thin grating model is derived to determine the appropriate separation of the slices, which shortens the computation time of tomographic reconstruction.