Quantitative assessment of noise reduction with partial spatial coherence illumination in digital holographic microscopy

Dohet-Eraly, Jérôme; Yourassowsky, Catherine; Mallahi, Ahmed El; Dubois, Frank

doi:10.1364/ol.41.000111

“…The second limitation is that only fluids with distinct RI values can be visualized; fluids with similar RI values may be difficult to image with quantitative phase microscopes, which have a limited phase sensitivity, especially when speckle noise exists. However, this phase sensitivity issue can be remedied by exploiting low-coherent light, such as white light illumination or speckle illumination [34][35][36][37]. Third, different fluids with the same RI values cannot be distinguished with the present method because this approach does not provide molecular specificity.…”

Section: Discussionmentioning

confidence: 97%

Visualization and label-free quantification of microfluidic mixing using quantitative phase imaging

Park

¹

,

Han

²

,

Kim

³

et al. 2017

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Microfluidic mixing plays a key role in various fields, including biomedicine and chemical engineering. To date, although various approaches for imaging microfluidic mixing have been proposed, they provide only quantitative imaging capability and require exogenous labeling agents. Quantitative phase imaging techniques, however, circumvent these problems and offer label-free quantitative information about concentration maps of microfluidic mixing. We present the quantitative phase imaging of microfluidic mixing in various types of polydimethylsiloxane microfluidic channels with different geometries; the feasibility of the present method was validated by comparing it with the results obtained by theoretical calculation based on Fick's law.

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“…The second limitation is that only fluids with distinct RI values can be visualized; fluids with similar RI values may be difficult to image with quantitative phase microscopes, which have a limited phase sensitivity, especially when speckle noise exists. However, this phase sensitivity issue can be remedied by exploiting low-coherent light, such as white light illumination or speckle illumination [34][35][36][37]. Third, different fluids with the same RI values cannot be distinguished with the present method because this approach does not provide molecular specificity.…”

Section: Discussionmentioning

confidence: 97%

Visualization and label-free quantification of microfluidic mixing using quantitative phase imaging

Park

¹

,

Han

²

,

Kim

³

et al. 2017

Preprint

0

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Microfluidic mixing plays a key role in various fields, including biomedicine and chemical engineering. To date, although various approaches for imaging microfluidic mixing have been proposed, they provide only quantitative imaging capability and require for exogenous labeling agents. Quantitative phase imaging techniques, however, circumvent these problems and offer label-free quantitative information about concentration maps of microfluidic mixing. We present the quantitative phase imaging of microfluidic mixing in various types of PDMS microfluidic channels with different geometries; the feasibility of the present method was validated by comparing it with the results obtained by theoretical calculation based on Fick's law. IntroductionMicrofluidic devices that control micrometre-sized samples in fluids are essential tools in various research fields such as analytical chemistry, biology and medicine [1,2]. Mixing in microfluidic channels has great potential due to the capability of controlling droplet volume, chemical concentration, and sorting of fluids [3]. Recently, microfluidic mixing has been used for pharmaceutical developments and medical diagnostics [4,5].In order to monitor microfluidic mixing, various optical imaging techniques have been proposed and used [6]. For example, phase contrast microscopy, differential interference contrast microscopy, and confocal microscopy have been employed to observe the mixing and extract information of fluid mixture. Among various methods, bright-field and fluorescence microscopy are well-established and readily available [7]. However, existing techniques have limitations in providing quantitative imaging information. Most fluids are transparent and thus do not provide enough imaging contrast. Although the use of exogenous fluorescent or dye molecules can enhance imaging contrast, these techniques provide only qualitative information on the local concentrations of fluids and also raise the issues of altering intrinsic fluid conditions. This imaging constraint is unfortunate because when microfluidic mixing can be quantified, microfluidic devices have much to offer with their unique control capabilities, high flexibility, and avoidance of the use of large amounts of samples. Despite the many challenges, there is a strong motivation to provide quantitative imaging of microfluidic mixing, especially if that imaging can be achieved without introducing exogenous labeling agents. Refractive index (RI) variation in microfluidic mixing can be detected by various optical methods including schlieren microscopy, speckle photography, and surface plasmon resonance [8][9][10][11][12][13][14]. However, these techniques do not provide quantitative measurements of microfluidic concentration.To overcome the limitations in the imaging of microfluidic mixing, quantitative phase imaging (QPI) techniques can be employed. QPI is based on interferometric microscopy; this process quantitatively and precisely measures the optical phase delay maps introduced by a sample. Recently, QPI has been...

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“…By using a low-coherent light source instead of a coherent laser, the image degradation is eliminated and the image quality is improved. 17,18 The light beam emitted from the light-emitting diode first passes a Köhler illumination path and then passes through the sample, which is located in the back focal plane of the microscope objective ( Fig. 6, Appendix A).…”

Section: Digital Holographic Microscopymentioning

confidence: 99%

Impact of sample preparation on holographic imaging of leukocytes

Klenk

¹

,

Heim

²

,

Ugele

³

et al. 2019

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The label-free analysis of leukocytes by holographic microscopy has the potential to overcome the extensive labeling procedures of conventional analysis by automated hematology analyzers and manual blood smear analysis. For the enrichment of leukocytes, selective lysis of erythrocytes is applied in flow cytometry to minimize the background. In the case of quantitative phase measurements, lysis procedures may affect the morphology of leukocytes inducing refractive index changes, which can deteriorate the specificity and sensitivity of the method. To study the effects of selective erythrocyte lysis on phase measurements of leukocytes, we compared two widespread methods: lysis by hypotonic shock followed by magnetic depletion of erythrocytes and lysis with a commercial lysis buffer containing ammonium chloride and potassium bicarbonate. We observed that lymphocytes were less affected than granulocytes and monocytes by both methods and that the intracellular changes increased with increasing incubation times. These findings indicate a significant effect of erythrocyte lysis on leukocytes and need to be studied for future hematology applications. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Quantitative assessment of noise reduction with partial spatial coherence illumination in digital holographic microscopy

Cited by 40 publications

References 16 publications

Visualization and label-free quantification of microfluidic mixing using quantitative phase imaging

Visualization and label-free quantification of microfluidic mixing using quantitative phase imaging

Visualization and label-free quantification of microfluidic mixing using quantitative phase imaging

Impact of sample preparation on holographic imaging of leukocytes

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