Single particle atmospheric aerosol analysis using digital holographic microscopy

Mona Mihailescu; Ruxandra Elena Cojocaru; C. Kusko; Flori Toanca; A. Dinescu; P. Schiopu

doi:10.1117/12.886755

11 May 2011 Single particle atmospheric aerosol analysis using digital holographic microscopy

Mona Mihailescu, Ruxandra Elena Cojocaru, C. Kusko, Flori Toanca, A. Dinescu, P. Schiopu

Proceedings Volume 8074, Holography: Advances and Modern Trends II; 807403 (2011) https://doi.org/10.1117/12.886755
Event: SPIE Optics + Optoelectronics, 2011, Prague, Czech Republic

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.

Citation Download Citation

Mona Mihailescu, Ruxandra Elena Cojocaru, C. Kusko, Flori Toanca, A. Dinescu, and P. Schiopu "Single particle atmospheric aerosol analysis using digital holographic microscopy", Proc. SPIE 8074, Holography: Advances and Modern Trends II, 807403 (11 May 2011); https://doi.org/10.1117/12.886755

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