Multiplexed, multi-wavelength 3D digital holographic imaging methods with range unwrapping

Abstract

Multi-wavelength digital holography is an imaging modality by which one collects multiple 2D coherent images of an object with different illumination wavelengths and digitally processes them in order to obtain a 3D coherent image. For conventional 3D imaging, the image formation process requires a fixed-phase relationship between the 2D coherent images, and, as such, object motion and/or vibration between 2D image collections can prevent the formation of a 3D image. One previously studied method compensates for object motion through the use of a second illumination frequency, or pilot tone. In this paper, we explore two altered 3D imaging modalities, dual-tone 3D imaging and stairstep 3D imaging, both of which, like pilot-tone 3D imaging, make use of holographic multiplexing. We compare conventional, pilot-tone, dual-tone, and stairstep 3D imaging in simulation. The results indicate that the stairstep approach offers the best performance for range imaging overall. Additionally, we employed a range unwrapping algorithm to unwrap ranges images for the modalities studied here. The results show that range unwrapping is usually successful if the measured discontinuities in the range dimension are no larger than half the range ambiguity interval.