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Lensless microscopes are simple, portable, and cost effective compared with the sophisticated microscopes of today that require high-end objectives, lenses, and filters. We demonstrate a lensless on-chip phase microscope based on the holographic principle to image 3D nanometric depth information from transparent and weakly scattering biological samples. We characterize the microscope using standard quantitative phase resolution target (PRT) charts with feature depths from 50 to 350 nm and report a signal-to-noise ratio value of 23 dB. Further, we apply a gradient descent-based constrained optimization approach for phase retrieval to eliminate the twin image and noise from the hologram. The device, operating as an inline holographic microscope, can perform quantitative phase imaging with nanometric depth sensitivity for a field of view of 29.4 mm2 using an LED-based light source butt-coupled to an optical fiber cable.

Conventional cytology is a rapid chair-side method for diagnosis, but it relies on laborious fixing and staining protocols. As cytology specimens are transparent, it is very hard to visualize them under a bright-field microscope without staining. Quantitative phase imaging techniques have opened up an interesting and potential diagnostic method for volumetric three-dimensional (3-D) visualization of the transparent specimens without any need for sample preparations. We explore the use of digital holographic microscopy in clinical application of oral cytology for the 3-D visualization of buccal cells with high contrast without any additional sample preparations. We also propose nuclear to cytoplasmic (N / C) volumes as a much more accurate parameter for identification of multinucleate and actively dividing cells. We quantify the cellular volumes, and N / C ratios for 203 buccal cells taken from five healthy volunteers to clinically validate the technique and compare them with the traditional N / C area ratios as well as the histology standards. The mean N / C area and volume ratios are found to be 0.0322 ± 0.0149 and 0.0648 ± 0.0286, respectively. Our approach highlights the dawn of a new method for a label-free/nondestructive volumetric oral cytology evaluation, with high potential for exploration of suspicious oral lesions, in subjects with chronic habits such as alcoholism and tobacco use.