Off-axis holographic tomography for diffracting scalar wavefields

Inverse scattering theories are available that permit tomographic reconstruction of the complex-valued refractive index distribution of weakly scattering objects from knowledge of intensity measurements. These imaging methods are valuable in applications that involve high-frequency optical wavefields, in which direct wavefield phase measurements can be difficult experimentally. The so-called in-line holographic imaging geometry has been well-studied, in which two measurements of the forward scattered wavefield intensity are acquired on distinct parallel detector planes that are perpendicular to the direction of the illuminating wavefields. In this work, based on the principles of intensity diffraction tomography, a reconstruction theory for off-axis holographic tomography with diffracting scalar wavefields is developed and investigated. A distinct feature of the method is that, at each tomographic view angle, the object is illuminated by use of two plane waves that propagate in different directions. The intensities of the forward scattered wavefields are measured on a single detector behind the object. This permits the direction of the probing wavefield to be varied for acquisition of the necessary measurement data, rather than the detector placement as required by conventional in-line holographic methods. The developed image reconstruction method is validated and investigated by use of computer-simulation studies.