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Proceedings Paper

Single particle atmospheric aerosol analysis using digital holographic microscopy
Author(s): Mona Mihailescu; Ruxandra Elena Cojocaru; C. Kusko; Flori Toanca; A. Dinescu; P. Schiopu
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Paper Abstract

The aim of this research is to calculate the refractive index of transparent atmospheric aerosols, which have biological origin, using a digital holographic microscopy technique (DHM). The samples are collected on filters, using miniature impactors for particles with dimensions smaller than 10μm (on even one axis), from a height of over 20 meters, in Magurele, a rural location near the urban and industrial agglomeration of the capital city, Bucharest. Due to their organic or inorganic origin, each atmospheric aerosol particle has different size, shape and optical properties which have a determinant role in LIDAR measurements. We record on a CCD camera hundreds of holograms which contain the diffraction pattern from every aerosol particle superposed with the reference wave. Digitally, we scan the entire volume of one particle with nanometric resolution (using an algorithm based on the Fresnel approximation). The calibration was done using an object with known dimensions fabricated by e-beam lithography and some complementary measurements were done in confocal microscopy. Our analysis separates four main classes of atmospheric aerosols particles (wires, columns, spherical fragments, and irregular). The predominant class in the investigated period is the first one, which has biological origin and the refractive index was calculated starting from the phase shift introduced by them in the optical path and models for their cylindrical shape. The influence of spatial filtering in the reconstructed object images was investigated.

Paper Details

Date Published: 11 May 2011
PDF: 10 pages
Proc. SPIE 8074, Holography: Advances and Modern Trends II, 807403 (11 May 2011); doi: 10.1117/12.886755
Show Author Affiliations
Mona Mihailescu, National Institute for Research and Development in Microtechnologies (Romania)
Politehnica Univ. from Bucharest (Romania)
Ruxandra Elena Cojocaru, Politehnica Univ. from Bucharest (Romania)
C. Kusko, National Institute for Research and Development in Microtechnologies (Romania)
Flori Toanca, National Institute of Research and Development for Optoelectronics (Romania)
A. Dinescu, National Institute for Research and Development in Microtechnologies (Romania)
P. Schiopu, Politehnica Univ. from Bucharest (Romania)

Published in SPIE Proceedings Vol. 8074:
Holography: Advances and Modern Trends II
Miroslav Hrabovský; Miroslav Miler; John T. Sheridan, Editor(s)

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