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Holographic particle characterization uses in-line holographic microscopy and the Lorenz-Mie theory of light scattering to measure the diameter and the refractive index of individual colloidal particles in their native dispersions. This wealth of information has proved invaluable in fields as diverse as soft-matter physics, biopharmaceuticals, wastewater management, and food science but so far has been available only for dispersions in transparent media. Here, we demonstrate that holographic characterization can yield precise and accurate results even when the particles of interest are dispersed in turbid media. By elucidating how multiple light scattering contributes to image formation in holographic microscopy, we establish the range conditions under which holographic characterization can reliably probe turbid samples. We validate the technique with measurements on model colloidal spheres dispersed in commercial nanoparticle slurries.
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Aberration compensation for enhanced holographic particle characterization
Holographic particle characterization treats holographic microscopy of colloidal particles as an inverse problem whose solution yields the diameter, refractive index and three-dimensional position of each particle in the field of view, all with exquisite precision. This rich source of information on the composition and dynamics of colloidal dispersions has created new opportunities for fundamental research in soft-matter physics, statistical physics and physical chemistry, and has been adopted for product development, quality assurance and process control in industrial applications. Aberrations introduced by real-world imaging conditions, however, can degrade performance by causing systematic and correlated errors in the estimated parameters. We identify a previously overlooked source of spherical aberration as a significant source of these errors. Modeling aberration-induced distortions with an operator-based formalism identifies a spatially varying phase factor that approximately compensates for spherical aberration in recorded holograms. Measurements on model colloidal dispersions demonstrate that phase-only aberration compensation greatly improves the accuracy of holographic particle characterization without significantly affecting measurement speed for high-throughput applications.
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- Award ID(s):
- 2104837
- PAR ID:
- 10467990
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Express
- Volume:
- 31
- Issue:
- 21
- ISSN:
- 1094-4087; OPEXFF
- Format(s):
- Medium: X Size: Article No. 35200
- Size(s):
- Article No. 35200
- Sponsoring Org:
- National Science Foundation
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