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1. Assessment of holographic microscopy for quantifying marine particle size and concentration

   https://doi.org/10.1002/lom3.10379  

   Walcutt, Noah L.; Knörlein, Benjamin; Cetinić, Ivona; Ljubesic, Zrinka; Bosak, Suncica; Sgouros, Tom; Montalbano, Amanda L.; Neeley, Aimee; Menden‐Deuer, Susanne; Omand, Melissa M. (August 2020, Limnology and Oceanography: Methods)

   Abstract Holographic microscopy has emerged as a tool for in situ imaging of microscopic organisms and other particles in the marine environment: appealing because of the relatively larger sampling volume and simpler optical configuration compared to other imaging systems. However, its quantitative capabilities have so far remained uncertain, in part because hologram reconstruction and image recognition have required manual operation. Here, we assess the quantitative skill of our automated hologram processing pipeline (CCV Pipeline), to evaluate the size and concentration measurements of environmental and cultured assemblages of marine plankton particles, and microspheres. Over 1 million particles, ranging from 10 to 200 μm in equivalent spherical diameter, imaged by the 4‐Deep HoloSea digital inline holographic microscope (DIHM) are analyzed. These measurements were collected in parallel with a FlowCam (FC), Imaging FlowCytobot (IFCB), and manual microscope identification. Once corrections for particle location and nonuniform illumination were developed and applied, the DIHM showed an underestimate in ESD of about 3% to 10%, but successfully reproduced the size spectral slope from environmental samples, and the size distribution of cultures (Dunaliella tertiolecta,Heterosigma akashiwo, andProrocentrum micans) and microspheres. DIHM concentrations (order 1 to 1000 particles ml⁻¹) showed a linear agreement (r²= 0.73) with the other instruments, but individual comparisons at times had large uncertainty. Overall, we found the DIHM and the CCV Pipeline required extensive manual correction, but once corrected, provided concentration and size estimates comparable to the other imaging systems assessed in this study. Holographic cameras are mechanically simple, autonomous, can operate at very high pressures, and provide a larger sampling volume than comparable lens‐based tools. Thus, we anticipate that these characterization efforts will be rewarded with novel discovery in new oceanic environments. 

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2. Genetically Encoded Phase Contrast Agents for Digital Holographic Microscopy

   https://doi.org/10.1021/acs.nanolett.0c03159  

   Farhadi, Arash; Bedrossian, Manuel; Lee, Justin; Ho, Gabrielle H.; Shapiro, Mikhail G.; Nadeau, Jay L. (November 2020, Nano Letters)

   null (Ed.)
3. Biodynamic digital holographic speckle microscopy for oocyte and embryo metabolic evaluation

   https://doi.org/10.1364/AO.404298  

   Li, Zhe; Lorenzo-Lorenzo, Ilka_M; An, Ran; Turek, John; Nolte, David_D; Machaty, Zoltan (November 2020, Applied Optics)

   Assisted reproductive technologies seek to improve the success rate of pregnancies. Morphology scoring is a common approach to evaluate oocyte and embryo viability prior to embryo transferin utero, but the efficacy of the method is low. We apply biodynamic imaging, based on dynamic light scattering and low-coherence digital holography, to assess the metabolic activity of oocytes and embryos. A biodynamic microscope, developed to image small and translucent biological specimens, is inserted into the bay of a commercial inverted microscope that can switch between conventional microscopy channels and biodynamic microscopy. We find intracellular Doppler spectral features that act as noninvasive proxies for embryo metabolic activity that may relate to embryo viability. 

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4. Accurate and Fast Phase Compensation of Dynamic Samples in Digital Holographic Microscopy

   Obando-Vasquez, Sofia; Doblas, Ana; Trujillo, Carlos (November 2023, Optica Imaging Congress (3D, COSI, DH, FLatOptics, IS, pcAOP))

   We present a fast algorithm for accurate phase compensation of holographic videos of dynamic phenomena recorded in a digital holographic microscope. The proposal is tested with human sperm and red blood cell samples. 

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5. Inverse scattering for reflection intensity phase microscopy

   https://doi.org/10.1364/BOE.380845  

   Matlock, Alex; Sentenac, Anne; Chaumet, Patrick_C; Yi, Ji; Tian, Lei (January 2020, Biomedical Optics Express)

   Reflection phase imaging provides label-free, high-resolution characterization of biological samples, typically using interferometric-based techniques. Here, we investigate reflection phase microscopy fromintensity-only measurements under diverse illumination. We evaluate the forward and inverse scattering model based on the first Born approximation for imaging scattering objects above a glass slide. Under this design, the measured field combineslinearforward-scattering and height-dependentnonlinearback-scattering from the object that complicates object phase recovery. Using only the forward-scattering, we derive a linear inverse scattering model and evaluate this model’s validity range in simulation and experiment using a standard reflection microscope modified with a programmable light source. Our method provides enhanced contrast of thin, weakly scattering samples that complement transmission techniques. This model provides a promising development for creating simplified intensity-based reflection quantitative phase imaging systems easily adoptable for biological research. 

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