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Digital in-line holography is a versatile method to obtain lens-less images of small particles, such as aerosol particles, ranging from several to over one hundred microns in size. It has been shown theoretically, and verified by measurement, that a particle’s extinction cross section can also be obtained from a digital hologram. The process involves a straightforward integration, but if noise is present it fails to give accurate results. Here we present a method to reduce the noise in measured holograms of single particles for the purpose of rendering the cross-section estimation more effective. The method involves masking the complex-valued particle image-amplitude obtained from a noisy hologram followed by a Fresnel transformation to generate a new noise-reduced hologram. Examples are given at two wavelengths, 440 nm and 1040 nm, where the cross section is obtained for a micro-sphere particle and several non-spherical particles approximately 50 microns in size.
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Imaging micrometer-sized aerosol particles with digital holography
Small particles that are trapped, deposited, or otherwise fixed can be imaged by digital holography with a resolution approaching that of optical microscopy. When such particles are in motion as an aerosol, a comparable resolution is challenging to achieve. Using a simplified bi-telecentric lens system, we demonstrate that 1µm free-flowing aerosol particles can be imaged at the single-particle level using digital in-line holography. The imaging is demonstrated with an aerosol of 1µm polystyrene latex microspheres and a ragweed pollen aerosol.
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- Award ID(s):
- 2107715
- PAR ID:
- 10505496
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Letters
- Volume:
- 49
- Issue:
- 10
- ISSN:
- 0146-9592; OPLEDP
- Format(s):
- Medium: X Size: Article No. 2653
- Size(s):
- Article No. 2653
- Sponsoring Org:
- National Science Foundation
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