Simulation of simultaneous surface morphology and subsurface shape measurement based on dual-wavelength dual-refractive-index digital holography

We present a new dual-wavelength dual-refractive-index digital holographic (DWDRIDH) technique that can be employed for simultaneously measuring the surface and subsurface three-dimensional topographies and does not involve the usual phase unwrapping by detection of phase discontinuity thanks to the resulting synthetic beat wavelength. The reconstructed unambiguous phase images for the synthetic beat wavelength are achieved by subtraction of the independent phase maps, which were obtained using four-phase step algorithm for each wavelength separately, and then both surface topography and subsurface shape can be decoupled from the phase maps on the beat wavelength by use of two separate refractive indices. By simulation technology, the feasibility of this method is demonstrated by the results concerning the surface and subsurface heights of a homocentric sphere and a simulated monocyte, respectively. (C) 2016 Elsevier GmbH. All rights reserved.