Quantitative phase imaging by automated Cepstrum-based interferometric microscopy (CIM)

Digital holographic microscopy (DHM) is a very popular interferometric technique for quantitative phase imaging (QPI). In DHM, an interferometer is combined with a microscope to create interference between an imaging beam containing information about the analysed sample and a clear reference beam carrying no sample information. To exploit the capability of reference beam in terms of useful sample information, we have recently proposed Cepstrum-based Interferometric Microscopy (CIM) [Opt. Las. Tech. 174, 110,626 (2024)] as a novel methodology involving the interference of two imaging beams carrying different sample information and to accurately retrieve quantitative phase data of both beams. In the earlier implementation, proof-of-concept of CIM was demonstrated for a Michelson-based layout requiring manual adjustments during the CIM methodology and validated only for low numerical aperture (NA) microscope lenses. In this contribution, we present a new CIM arrangement that provides precise QPI with medium NA microscope lenses and avoids manual intervention of the user during the hologram recording. This new approach incorporates a compact quasi-common-path Mach-Zehnder configuration at the output port of an infinity corrected microscope system to interfere two imaging beams containing information from different regions of the sample. By sequentially recording three off-axis holograms and applying the Spatial-Shifting Cepstrum (SSC) algorithm, decoupled QPI of both complex fields are retrieved, doubling the accessible field of view (FOV). The effectiveness of the approach is experimentally validated using two medium NA microscope lenses with distinct features (20x/0.42NA and 50x/0.55NA). The approach is first validated with calibrated phase objects, and then assessed for imaging of various biological samples.