Digital Holographic Microscopy Research Papers (original) (raw)

2025, Micron (Oxford, England : 1993)

Platelet activation and aggregation have been conventionally evaluated using an aggregometer. However, this method is suitable for short-term but not long-term quantitative evaluation of platelet aggregation, morphological changes, and/or adhesion to specific materials. The recently developed digital holographic microscopy (DHM) has enabled the quantitative evaluation of cell size and morphology without labeling or destruction. Thus, we aim to validate its applicability in quantitatively evaluating changes in cell morphology, especially in the aggregation and spreading of activated platelets, thus modifying typical image analysis procedures to suit aggregated platelets. Freshly prepared platelet-rich plasma was washed with phosphate-buffered saline and treated with 0.1% CaCl. Platelets were then fixed and subjected to DHM, scanning electron microscopy (SEM), atomic force microscopy, optical microscopy, and flow cytometry (FCM). Tightly aggregated platelets were identified as single ...

2025

Noise reduction and image quality improvement by the use of partial coherence illumination will be shown in digital holographic microscopy (DHM). The DHM will be compared to other techniques providing the quantitative phase contrast... more

2025

This paper presents a detailed proof of concept and hardware design for a novel optical fractal processor, an innovative approach to Artificial General Intelligence (AGI) inspired by complex wave dynamics and the inherent self-similarity found in natural phenomena. Moving beyond traditional binary computing, this system proposes modulating coherent light using specially configured quartz crystals and a Spatial Light Modulator (SLM) to generate intricate fractal patterns described by the complex wave function (f(\lambda, t) = I_0 \sin(\omega t + \alpha \lambda) e^{i(\omega t-k\lambda + \beta\lambda^2)}). The hardware integrates advanced optical components with a robust computational interface to process these optical patterns adaptively, aiming for superior energy efficiency, generalization, and a more natural form of intelligence compared to current silicon-based paradigms. We detail the theoretical foundation, hardware components, operational principles, and expected outcomes, alongside identified limitations, offering a comprehensive overview of this groundbreaking computational paradigm.

2025

An experimental setup for super-resolution microscopy by structured illumination is presented, preliminary experiments of nano-beads and living cells with a resolution around 100 nm are described, and further requirements for live cell... more

2025, Medical research archives

Commonly trans-illumination or epi-illumination techniques are used in optical microscopy, e.g. phase microscopy, fluorescence microscopy or inelastic light scattering (Raman microscopy). However, an increasing number of applications requires optical excitation perpendicular or under a certain angle to the optical axis. Methods include Mie Scattering Microscopy with angular resolution for label-free studies of cell or tissue morphology as well as Total Internal Reflection Fluorescence (TIRF) Microscopy with an evanescent electromagnetic field penetrating only about 100 nm into a sample and permitting selective studies of cell surfaces, e.g. membranes. Presently, conventional wide field or confocal microscopy are often replaced by Light Sheet Fluorescence Microscopy (LSFM) where individual planes of a specimen are illuminated from the side without any light exposure or phototoxic damage of adjacent parts of the sample. Finally, Axial Tomography permits samples to be observed from var...

2025, Applied Sciences

Additive manufacturing has acquired a global industrial panorama for being an alternative to redirect the industry towards sustainability. However, previous studies have indicated that fused deposition modelling (FDM) techniques are potential sources of particles that are harmful to health. For this reason, this work is focused on exploring the behaviour and distribution of FDM resultant nanoparticles from the most commonly used printable materials through alternative methods as digital holographic microscopy (DHM). In this paper, we present the feasibility of using DHM to determine the presence of nanoparticles in the FDM process. Experimental results validate this technology’s precision and provide extensive knowledge about the implications of the FDM on health. The measure of the thin films deposited in glass substrates was between a minimum of 9 nm to a maximum of 200 nm, in agreement with the previous studies.

2025, IEEE Journal of Selected Topics in Signal Processing

Three-dimensional representations in light microscopy are important for accurate shape assessment of model systems in biosciences. The computational multi-view 3D reconstruction seems feasible in obtaining the 3D representations in particular for high-throughput. The specimen for imaging can have properties, i.e. transparency and translucency, that impede the detection of well-defined boundaries. Consequently, 3D reconstruction and measurements i.e. volume and surface area will be inaccurate. The motivation in this work is therefore to develop a two-phase 3D reconstruction approach for light microscopy axis-view imaging that can deal with these properties. In phase I of this approach, we develop an improved 3D volumetric representation defined as the confidence map. This is derived from texture-augmented axial-view images of the specimen. In phase II, the 3D reconstruction is accomplished by searching the optimal surface for the specimen over the confidence map. Subsequently, from the obtained 3D reconstruction, 3D measurements can be extracted. We present a high-throughput axial-view imaging architecture in light microscopy based on the Vertebrate Automated Screening Technology device. Using this imaging architecture, we present three typical datasets using different imaging modalities, which includes zebrafish larvae in bright-field and zebrafish liver in fluorescence. In the experiments, we have applied our approach on these datasets. We find that our approach yields precise 3D shape representation and natural visualization. In comparison with a groundtruth setup, we have obtained accurate 3D measurements both for the organism and the organ, which holds a promising shape assessment for model systems in biosciences.

2025

Dust explosibility data are a critical input to the design of equipment and strategies for reducing the risk of a combustible dust deflagration or explosion. These data, which include minimum explosible concentrations, deflagration indices, and explosion overpressures, are obtained using formally accepted, standard techniques, and are known to be sensitive to the particle size characteristics of the dust being evaluated. Published literature demonstrates that the standard techniques can alter the particle size distribution during dispersion, making interpretation of the explosibility data challenging because the particle characteristics are altered from their original, raw state. Digital in-line holography (DIH) presents a novel method for measuring airborne dust particle size distributions and imaging three-dimensional particle flows during dispersion to characterize the changes to the particle size characteristics and to investigate the underlying mechanisms. In this work, a DIH i...

2025, Applied Optics

This paper considers some of the most important optical parameters that characterize a digital holographic microscope (DHM) and presents their mathematical derivation based on geometrical and diffraction-based models. It supports and justifies the use of the out-of-focus recording of holograms by showing that the field of view can be increased when recording the hologram in front of the in-focus image plane. In this manner a better match between the space-bandwidth product (SBP) of the microscope objective and that of the reconstructed hologram can be obtained. Hence, DHM offers a more cost-efficient way to increase the recorded SBP compared to the application of a high-quality microscope objective (large numerical aperture and low magnification) used in conventional microscopy. Furthermore, an expression for the imaging distance (distance between hologram and image plane), while maintaining the optical resolution and sufficient sampling, is obtained. This expression takes into account all kinds of referencewave curvature and can easily be transferred to lensless digital holography. In this context it could be demonstrated that an object wave matched reference wave offers a significantly smaller imaging distance and hence the largest recoverable SBP. In addition, a new, to our knowledge, approach, based on the influence of defocus on the modulation transfer function, is used to derive the depth of field (DOF) for a circular aperture (lens-based system) and a rectangular aperture (lensless system), respectively. This investigation leads to the finding that a rectangular aperture offers an increased resolution combined with an increased DOF, when compared to a circular aperture of the same size.

2025, SPIE Proceedings

We have applied wide-field digital interferometric techniques to quantitatively image sickle red blood cells (RBCs) in a noncontact label-free manner, and measure the nanometer-scale fluctuations in their thickness as an indication of their stiffness. The technique can simultaneously measure the fluctuations for multiple spatial points on the RBC and thus yields a map describing the stiffness of each RBC in the field of view. Using this map, the local rigidity regions of the RBC are evaluated quantitatively. Since wide-field digital interferometry is a quantitative holographic imaging technique rather than one-point measurement, it can be used to simultaneously evaluate cell transverse morphology plus thickness in addition to its stiffness profile. Using this technique, we examine the morphology and dynamics of RBCs from individuals who suffer from sickle cell disease, and find that the sickle RBCs are significantly stiffer than healthy RBCs. Furthermore, we show that the technique is sensitive enough to distinguish various classes of sickle RBCs, including sickle RBCs with visibly-normal morphology, compared to the stiffer crescent-shaped sickle RBCs.

2025, Biophysical Journal

2025

Introduction: A future Europa Lander mission, will play a crucial role in achieving NASA’s long standing goals – to determine whether or not we are alone in the universe. Searching for life on Europa is one of the highest-level science goals for the mission. The detection of life on Europa should not rely on a singular measurement. Instead, multiple lines of evidence detected on a variety of spatial scales from different instruments should be used to provide sufficient evidence of life detection on Europa [1]. Atomic force microscopy (AFM) is a high potential technique to reveal the topographic information for biosignatures detection of biogenic microstructures at the nanoscale level. However, it suffers from false positive risk mitigated by AFM mechano-sensing capability and has slow throughput since it is a scanning technique [1]. Quantitative phase imaging (QPI) is an alternative approach to measure the microstructures topography reconstructed through phase information. It is a o...

2025, Optical Engineering

The modulus of the gradient of the color planes (MGC) is implemented to transform multichannel information to a grayscale image. This digital technique is used in two applications: (a) focus measurements during autofocusing (AF) process and (b) extending the depth of field (EDoF) by means of multifocus image fusion. In the first case, the MGC procedure is based on an edge detection technique and is implemented in over 15 focus metrics that are typically handled in digital microscopy. The MGC approach is tested on color images of histological sections for the selection of in-focus images. An appealing attribute of all the AF metrics working in the MGC space is their monotonic behavior even up to a magnification of 100×. An advantage of the MGC method is its computational simplicity and inherent parallelism. In the second application, a multifocus image fusion algorithm based on the MGC approach has been implemented on graphics processing units (GPUs). The resulting fused images are evaluated using a nonreference image quality metric. The proposed fusion method reveals a high-quality image independently of faulty illumination during the image acquisition. Finally, the three-dimensional visualization of the in-focus image is shown.

2025, Chinese Optics Letters

We outline the use of digital holographic tomography to determine the three-dimensional (3D) shapes of falling and static objects, such as lenslets and water droplets. Reconstruction of digitally recorded inline holograms is performed... more

2025

Biologists use optical microscopes to study plankton in the lab, but their size, complexity and cost makes widespread deployment of microscopes in lakes and oceans challenging. Monitoring the morphology, behavior and distribution of plankton in situ is essential as they are excellent indicators of marine environment health and provide a majority of Earth's oxygen and carbon sequestration. Direct in-line holographic microscopy (DIHM) eliminates many of these obstacles, but image reconstruction is computationally intensive and produces monochromatic images. By using one laser and one white LED, it is possible to obtain the 3D location plankton by triangulation, limiting holographic reconstruction to only the voxels occupied by the plankton, reducing computation by several orders of magnitude. The color information from the white LED assists in the classification of plankton, as phytoplankton contains green-colored chlorophyll. The reconstructed plankton images are rendered in a 3D interactive environment, viewable from a browser, providing the user the experience of observing plankton from inside a drop of water.

2025, Journal of Biomedical Photonics & Engineering

Polarization diffraction gratings are formed by one-step polarization holographic recording in azopolymer thin films. The evolution of the gratings parameters, such as the modulation of diffraction efficiency and relief depth with regard to different exposure dose is analyzed. Phase-shifting digital holographic microscopy is applied for the measurement of the light-induced polarization diffraction gratings. For the accurate hologram acquisition and reconstruction of the complex amplitude transmitted by the gratings, we performed all-optical (without moving components) phase-shifting implemented within in the imaging system of the digital holographic microscope. The experimental measurement results and theoretical predictions were compared and analyzed.

2025, Optics express

Crucial benefits provided by partially coherent light microscopy such as improved spatial resolution, optical sectioning and speckle-noise suppression are exploited here to achieve 3D quantitative imaging: reconstruction of the object refractive index (RI). We present a partially coherent optical diffraction tomography technique (PC-ODT) that can be easily implemented in commercially available bright-field microscopes. We show that the high numerical apertures of the objective and condenser lenses, together with optical refocusing, are main issues for achieving fast and successful 3D RI reconstruction of weak objects. In particular, the optical refocusing is performed by a high-speed focus tunable lens mounted in front of the digital camera enabling compatibility with commercial microscopes. The technique is experimentally demonstrated on different examples: diatom cells (biosilica shells), polystyrene micro-spheres and blood cells. The results confirm the straightforward 3D-RI reco...

2025

Lens-free on-chip microscopy (LFOCM) is a powerful computational imaging technology that combines high-throughput capabilities with cost efficiency. However, in LFOCM, the phase recovered by iterative phase retrieval techniques is generally wrapped into the range of-π to π, necessitating phase unwrapping to recover absolute phase distributions. Moreover, this unwrapping process is prone to errors, particularly in areas with large phase gradients or low spatial sampling, due to the absence of reliable initial guesses. To address these challenges, we propose a novel biplane phase retrieval (BPR) method that integrates phase unwrapping results obtained at different propagation distances to achieve accurate absolute phase reconstruction. The effectiveness of BPR is validated through live-cell imaging of HeLa cells, demonstrating improved quantitative phase imaging (QPI) accuracy when compared to conventional off-axis digital holographic microscopy. Furthermore, time-lapse imaging of COS-7 cells in vitro highlights the method's robustness and capability for long-term quantitative analysis of large cell populations.

2025, Journal of the Optical Society of Korea

Red blood cells (RBCs) are customarily adhered to a bio-functionalised substrate to make them stationary in interferometric phase-imaging modalities. This can make them susceptible to receive alterations in innate morphology due to their own weight. Optical tweezers (OTs) often driven by Gaussian profile of a laser beam is an alternative modality to overcome contact-induced perturbation but at the same time a steeply focused laser beam might cause photo-damage. In order to address both the photo-damage and substrate adherence induced perturbations, we were motivated to stabilize the RBC in OTs by utilizing a laser beam of 'arbitrary intensity profile' generated by a source having cavity imperfections per se. Thus the immobilized RBC was investigated for phase-imaging with sinusoidal interferograms generated by a compact and robust Michelson interferometer which was designed from a cubic beam splitter having one surface coated with reflective material and another adjacent coplanar surface aligned against a mirror. Reflected interferograms from bilayers membrane of a trapped RBC were recorded and analyzed. Our phase-imaging set-up is limited to work in reflection configuration only because of the availability of an upright microscope. Due to RBC's membrane being poorly reflective for visible wavelengths, quantitative information in the signal is weak and therefore, the quality of experimental results is limited in comparison to results obtained in transmission mode by various holographic techniques reported elsewhere.

2025, Holography - Recent Advances and Applications [Working Title]

Digital holographic interferometry (DHI) is used worldwide for many scientific and industrial applications. In DHI, two digital holograms; one in the reference/ambient state of the object and another in changed state of object are recorded by electronic imaging sensors (such as CCD/CMOS) as reference holograms and object holograms, respectively. Phase of object wavefronts in different states of the object is numerically reconstructed from digital holograms. The interference phase is reconstructed by subtracting the phase of reference hologram from the phase of object hologram, without performing any phase-shifting interferometry. Thus, no extra effort is needed in DHI for calculating the interference phase. Apart from direct reconstruction of interference phase from two digital holograms, the recent development, availability of recording devices at video rate, and high-performance computers make the measurements faster, reliable, robust, and even real-time. In this chapter, DHI is p...

2025, Applied Optics

A generalized sequential four-step phase-shifting color digital holography is proposed. As an arbitrary phase-shift quantity is independent from wavelengths, it can be used for four-step phase-shifting color digital holography. Furthermore, no constraint on the phase-shifting quantities or statistical property on the hologram is required in the proposed method. Experimental results using a reflective object are shown to confirm the proposed phase-shifting digital holography.

2025, Applied Optics

A single-shot three-dimensional (3D) shape measurement by low-coherent optical path difference digital holography with small energy consumption is proposed. The use of a superluminescent diode makes it possible. Weighting of the single hologram and numerical reconstruction give the 3D shape of an object. Experimental results using a simple object (the surface of a button cell battery) are given. By comparison with experimental results using a vertical scanning method, the proposed method is confirmed. The effects of a shift interval of the hologram and a zero-order component on a measurement result are also discussed.

2025, Optics and Lasers in Engineering

The structured illumination (SI) architecture can be adopted in a digital holographic (DH) microscope to enhance the spatial resolution. In this paper, we propose and demonstrate a compact and simple SI method in a self-referencing common-path configuration of DH microscopy. The combination of SI pattern generated by a compact disk and common-path off-axis geometry formed by Fresnel biprism introduces a low-cost and highly stable system to image both amplitude and phase objects with a twofold improvement of the spatial resolution. Experimental results for the case of a standard test sample validate the predicted resolution enhancement compared to that of the conventional imager. The presented DH method allows for imaging living cells with strikingly improved clarity compared to the conventional DH microscopes.

2025, Optics and Photonics Society of Iran

In this paper we repor t the effect of phase modulation on increasing the threshold of non-linear Brillouin Scatter ing effect in fiber amplifier s. We theoretically and experimentally show that, applying phase modulation generates numerous new side-bands around the central frequency. This technique results in immense enhancement on SBS threshold. The effect of frequency and amplitude var iation on SBS threshold is investigated . We obtain 280 W output power by optimizing the frequency to 60 MHz and the amplitude to 30 dBm, in a 3-stage fiber amplifier with nar row line-width.

2024, 振动工程学报

介绍了一种基于计算机视觉的结构模态参数辨识方法，对于连续、长时间的采样视频，该方法通过设置局部 “虚拟”测点、放大视频切片的处理方式，保证了测量结果的精度和分辨率，同时显著提高了数据处理效率。该方法具体步骤包括:拍摄被测结构在外激励下响应历程的一段视频;通过图像边缘检测算法在结构边缘处设置若干“虚拟”测点;通过光流法提取测点的表观运动响应，并利用随机子空间法辨识结构的模态参数;依次截取与每一阶模态对应的整周期运动视频，通过运动放大算法获得结构的全场工作模态振型。开展了模型飞机的单频振动试验，结果表明视觉测振的频率误差小于频率分辨率。开展了悬臂梁的模态分析试验，利用相机和激光多普勒测振仪同时进行动力学响应测量，结果显示提出的视觉方法与激光多普勒测振仪对悬臂梁结构前五阶模态频率的测量误差不超过 0.35%，阻尼比的测量误差不超过 14.6%，两者振型的 MAC 值高于 94%，测量结果基本吻合。

2024, Journal of biomedical optics

In the last few years, classification of cells by machine learning has become frequently used in biology. However, most of the approaches are based on morphometric (MO) features, which are not quantitative in terms of cell mass. This may result in poor classification accuracy. Here, we study the potential contribution of coherence-controlled holographic microscopy enabling quantitative phase imaging for the classification of cell morphologies. We compare our approach with the commonly used method based on MO features. We tested both classification approaches in an experiment with nutritionally deprived cancer tissue cells, while employing several supervised machine learning algorithms. Most of the classifiers provided higher performance when quantitative phase features were employed. Based on the results, it can be concluded that the quantitative phase features played an important role in improving the performance of the classification. The methodology could be valuable help in refi...

2024

Gas bubbles smaller than 1 micrometre in water, commonly referred to as nanobubbles, is a growing field of research and innovation. Applications range from medical imaging and drug delivery to mining industry and environmental remediation. Despite much activity, important questions remain -which are the mechanisms that allow small gas bubbles to be stable against dissolution and are stable nanobubbles really as common and easily generated as is often claimed? This work demonstrates that several common nanobubble generation methods can generate particle agglomerates or oil droplets which can be mistaken for bubbles, whereas stable nano-and microbubbles are less easy to generate than commonly believed. The results further suggest that stable bubbles are normally stable due to a shell of surface-active organic compounds, whereas other proposed stability mechanisms are less likely. An unexpected finding was that sorbitan surfactant stabilized air nanobubbles can form long-lived bubble agglomerates. Holographic Nanoparticle Tracking Analysis (H-NTA) is demonstrated as a powerful new method to detect and differentiate between bubbles and particles in the same dispersion. As H-NTA determines the refractive index of tracked objects, bubbles will differ very significantly from solid particles or oil droplets. The method also enables detection of different populations of particles, agglomerates and oil droplets in the same dispersion.

2024, Journal of Biophotonics

We report results on unsupervised organization of cervical cells using microscopy of Pap‐smear samples in brightfield (3‐channel color) as well as high‐resolution quantitative phase imaging modalities. A number of morphological parameters are measured for each of the 1450 cell nuclei (from 10 woman subjects) imaged in this study. The principal component analysis (PCA) methodology applied to this data shows that the cell image clustering performance improves significantly when brightfield as well as phase information is utilized for PCA as compared to when brightfield‐only information is used. The results point to the feasibility of an image‐based tool that will be able to mark suspicious cells for further examination by the pathologist. More importantly, our results suggest that the information in quantitative phase images of cells that is typically not used in clinical practice is valuable for automated cell classification applications in general.

2024, Assay and Drug Development Technologies

We introduce a label-free technology based on digital holographic microscopy (DHM) with applicability for screening by imaging, and we demonstrate its capability for cytotoxicity assessment using mammalian living cells. For this first high content screening compatible application, we automatized a digital holographic microscope for image acquisition of cells using commercially available 96-well plates. Data generated through both label-free DHM imaging and fluorescence-based methods were in good agreement for cell viability identification and a Z 0-factor close to 0.9 was determined, validating the robustness of DHM assay for phenotypic screening. Further, an excellent correlation was obtained between experimental cytotoxicity dose-response curves and known IC 50 values for different toxic compounds. For comparable results, DHM has the major advantages of being label free and close to an order of magnitude faster than automated standard fluorescence microscopy.

2024, Applied Optics

We apply a wide-field quantitative phase microscopy technique based on parallel two-step phase-shifting on-axis interferometry to visualize live biological cells and microorganism dynamics. The parallel on-axis holographic approach is more efficient with camera spatial bandwidth consumption compared to previous off-axis approaches and thus can capture finer sample spatial details, given a limited spatial bandwidth of a specific digital camera. Additionally, due to the parallel acquisition mechanism, the approach is suitable for visualizing rapid dynamic processes, permitting an interferometric acquisition rate equal to the camera frame rate. The method is demonstrated experimentally through phase microscopy of neurons and unicellular microorganisms.

2024, arXiv (Cornell University)

2024, Optics and Lasers in Engineering

2024, Applied Optics

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

2024

Large amounts of lipids are stored inside lipid droplets by some microalgae. Since these lipids can be used to produce nutraceuticals and biodiesel in a sustainable way, research is developing on fast non-destructive methods to quantify and monitor the amount of lipids within microalgal cultures. In this paper, we have developed with digital holographic microscopy a fast quantitative method to assess the evolution of the lipid content inside the diatom Phaeodactylum tricornutum living cells. The method uses a specific processing of recorded hologram sequences based on the refocusing capability in digital holographic microscopy. In representative samples of the culture, inside living cells, each lipid droplet volume is evaluated. In those experiments, for each sample, more than one thousand lipid droplets are automatically analysed from a sequence of one hundred recorded holograms. We have validated the method thanks to correlative quantitative phase contrast-fluorescence imaging and extrapolated it to larger calibrated spherical refractive particles, to demonstrate the flexibility of the method.

2024, Holography - Recent Advances and Applications [Working Title]

In this chapter, we describe several configurations of digital holographic microscopes operating with partially coherent illumination, including the implementation of color holography. The different ways of implementing partially coherent illumination are described and discussed, as well as the respective improvements they provide depending on the properties of the observed objects. Several significant applications in the biomedical and environmental fields are presented. In particular, we carry out researches on correlative quantitative phase-contrast-fluorescence imaging on blood with a special focus on the behavior of platelets in relation to relevant pathologies. In the environmental domain, we demonstrate the use of high-throughput digital holographic microscopy to monitor and analyze plankton and microalgal cultures.

2024, arXiv (Cornell University)

Some microalgae store large amounts of neutral lipids inside lipid droplets. Since these lipids can be used to produce biodiesel in a sustainable way, research is developing on fast nondestructive methods to quantify and monitor the amount of lipids in microalgal cultures. In this paper, we have developed with digital holographic microscopy a fast quantitative method to assess the evolution of the lipid content inside the diatom Phaeodactylum tricornutum living cells. The method uses a specific processing of recorded hologram sequences based on the refocusing capability of digital holographic microscopy. Each lipid droplet volume is evaluated inside the cells on representative samples of the culture. We have validated the method thanks to correlative quantitative phase contrastfluorescence imaging and extrapolated it to larger calibrated spherical refractive particles, to demonstrate the flexibility of the method.

2024

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et a ̀ la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Noname manuscript No. (will be inserted by the editor) Dynamics of vesicle suspensions in shear flow between walls

2024, Limnology and Oceanography: Methods

Phytoplankton are a vital component of all aquatic ecosystems, as they play key roles in the biogeochemical cycling of oceans, rivers, and lakes, and sustain the higher trophic levels in the food web of these ecosystems (Culverhouse 2007). The phytoplankton encompass a diverse group of organisms, including diatoms, cyanobacteria, dinoflagellates, and coccolithophorids, which serve as indicators of environmental and climate change, whether natural or human-induced . Quantitative information on the abundance, diversity, and dynamics of these different taxonomic groups within the phytoplankton is therefore essential . Apart from ecological questions targeting bloom dynamics, species succession, and spatial and temporal patchiness, the monitoring of phytoplankton composition is also crucial for many economically important applications, such as the analysis of ballast water , the development of algalbased biofuels (Singh and Gu 2010), and the monitoring of harmful algal blooms . Techniques for the determination of phytoplankton composition are inherently characterized by a trade-off between processing speed (i.e., the number of cells that can be classified per unit of time) and taxonomic resolution (i.e., the lowest taxonomic level to which cells can be classified). Historically, the determination of phytoplankton composition has been based on detailed microscopic analysis, which is capable of high taxonomic resolution down to cell sizes of approximately 5 μm. Microscopy can be performed in a variety of modes (transmitted light, scattered light, fluorescence, phase contrast, etc.), and each of these "imaging" modes provides distinct and complementary information about the morphology and

2024, Imaging and Applied Optics 2016

A fast refocusing criterion using the phase in the frequency domain is presented, suitable for applications providing polychromatic complex field imaging, like color interferometric digital holographic microscopy. Simulations and... more

2024, Biomedical Optics Express

Platelet spreading and retraction play a pivotal role in the platelet plugging and the thrombus formation. In routine laboratory, platelet function tests include exhaustive information about the role of the different receptors present at the platelet surface without information on the 3D structure of platelet aggregates. In this work, we develop, a method in Digital Holographic Microscopy (DHM) to characterize the platelet and aggregate 3D shapes using the quantitative phase contrast imaging. This novel method is suited to the study of platelets physiology in clinical practice as well as the development of new drugs.

2024, Biomedical Optics Express

In this paper we investigate the use of a digital holographic microscope, with partial spatial coherent illumination, for the automated detection and tracking of spermatozoa. This in vitro technique for the analysis of quantitative parameters is useful for assessment of semen quality. In fact, thanks to the capabilities of digital holography, the developed algorithm allows us to resolve in-focus amplitude and phase maps of the cells under study, independently of focal plane of the sample image. We have characterized cell motility on clinical samples of seminal fluid. In particular, anomalous sperm cells were characterized and the quantitative motility parameters were compared to those of normal sperm.

2024, Microgravity Sci. Technol.

The behaviour of a vesicle suspension in a simple shear flow between plates (Couette flow) was investigated experimentally in parabolic flight and sounding rocket experiments by Digital Holographic Microscopy. The lift force which pushes deformable vesicles away from walls was quantitatively investigated and is found to be rather well described by a theoretical model by Olla . At longer shearing times, vesicles reach a steady distribution about the center plane of the shear flow chamber, through a balance between the lift force and shear induced diffusion due to hydrodynamic interactions between vesicles. This steady distribution was investigated in the BIOMICS experiment in the MASER 11 sounding rocket. The results allow an estimation of selfdiffusion coefficients in vesicle suspensions and reveal possible segregation phenomena in polydisperse suspensions.

2024, EPL (Europhysics Letters)

The dynamics of a vesicle suspension in a shear flow between parallel plates has been investigated under microgravity conditions, where vesicles are only submitted to hydrodynamic effects such as lift forces due to the presence of walls and drag forces. The temporal evolution of the spatial distribution of the vesicles has been recorded thanks to digital holographic microscopy, during parabolic flights and under normal gravity conditions. The collected data demonstrates that vesicles are pushed away from the walls with a lift velocity proportional toγR 3 /z 2 whereγ is the shear rate, R the vesicle radius and z its distance from the wall. This scaling as well as the dependence of the lift velocity upon vesicle aspect ratio are consistent with theoretical predictions by Olla [

2024, Applied Optics

We investigate the use of a digital holographic microscope working with partially coherent spatial illumination to study concentration profiles inside confined deformable bodies flowing in microchannels. The studied phenomenon is rapidly changing in time and requires the recording of the complete holographic information for every frame. For this purpose, we implemented one of the classical methods of off-axis digital holography: the Fourier method. Digital holography allows one to numerically investigate a volume by refocusing the different planes of depth, allowing one to locate the objects under investigation in three dimensions. Furthermore, the phase is directly related to the refractive index, thus to the concentration inside the body. Based on simple symmetry assumptions, we present an original method for determining the concentration profiles inside deformable objects in microconfined flows. Details of the optical and numerical implementation, as well as exemplative experimental results are presented.

2024

Digital Holography Microscopy (DHM) is a new 3D measurement technique that exists since Charge Coupled Devices (or CCD cameras) allow to record numerically high resolution images. That opens a new door to the theory of holography... more

2024, Applied Optics

We describe the implementation of the automatic spatial-frequency-selection filter for recognition of patterns obtained with a digital holographic microscope working with a partially coherent source. The microscope provides the complex-optical-amplitude field that allows a refocusing plane-by-plane of the sample under investigation by numerical computation of the optical propagation. By inserting a correlation filter in the propagation equation, the correlation between the filter and the propagated optical field is obtained. In this way, the pattern is located in the direction of the optical axis. Owing to the very weak noise level generated by the partially coherent source, the correlation process is shift invariant. Therefore the samples can be located in the three dimensions. To have a robust recognition process, a generalized version of the automatic spatial-frequency-selection filters has been implemented. The method is experimentally demonstrated in a two-class problem for the recognition of protein crystals.

2024, AIMS Biophysics

Digital Holographic Microscopy (DHM) is an emerging technique for three-dimensional imaging of microorganisms due to its high throughput and large depth of field relative to traditional microscopy techniques. While it has shown substantial success for use with eukaryotes, it has proven challenging for bacterial imaging because of low contrast and sources of noise intrinsic to the method (e.g. laser speckle). This paper describes a custom written MATLAB routine using machinelearning algorithms to obtain three-dimensional trajectories of live, lab-grown bacteria as they move within an essentially unrestrained environment with more than 90% precision. A fully annotated version of the software used in this work is available for public use.

2024, Bulletin of the American Physical Society

the polymer concentration in the electro spun solution, the applied voltage, the injection pressure and the needle-electrode distance. The micro jet near the nozzle exit was observed in-flight using digital holographic microscopy and the collected nanofibers were examined using Scanning Electron Microscopy (SEM). The measurements include initial liquid jet diameter and the wave lengths of the jet instabilities. The present results show a strong relationship between the initial jet instability (near the injector exit) and the bead formation on the collected nanofibers.

2024, IEEE Robotics and Automation Letters

Three-dimensional (3-D) tracking of microrobots is demonstrated using stereo holographic projections. The method detects the lateral position of a microrobot in two orthogonal in-line holography images and triangulates to obtain the 3-D position in an observable volume of 1 cm 3. The algorithm is capable of processing holograms at 25 Hz on a desktop computer and has an accuracy of 24.7 µm and 15.2 µm in the two independent directions and 7.3 µm in the shared direction of the two imaging planes. This is the first use of stereo holograms to track an object in real time and does not rely on the computationally expensive process of holographic reconstruction.

2024, Conference on Automation Science and Engineering

Digital holography is used to track the threedimensional (3D) position of a magnetic microrobot maneuvered in real-time by means of an electromagnetic manipulation system. The method presented is able to process holograms at 40 Hz with a position accuracy in the imaging plane and in depth of ±23 and ±180 µm, respectively. As this method does not require magnification, microrobots can be tracked in significantly larger working volumes than conventional optical methods. The performance of this tracking method is demonstrated by visually servoing a magnetic bead around a cubic trajectory.