Author:
Giri Ramesh,Berg Matthew J.
Abstract
AbstractDigital in-line holography (DIH) is an established method to image small particles in a manner where image reconstruction is performed computationally post-measurement. This ability renders it ideal for aerosol characterization, where particle collection or confinement is often difficult, if not impossible. Conventional DIH provides a gray-scale image akin to a particle’s silhouette, and while it gives the particle size and shape, there is little information about the particle material. Based on the recognition that the spectral reflectance of a surface is partly determined by the material, we demonstrate a method to image free-flowing particles with DIH in color with the eventual aim to differentiate materials based on the observed color. Holograms formed by the weak backscattered light from individual particles illuminated by red, green, and blue lasers are recorded by a color sensor. Images are reconstructed from the holograms and then layered to form a color image, the color content of which is quantified by chromaticity analysis to establish a representative signature. A variety of mineral dust aerosols are studied where the different signatures suggest the possibility to differentiate particle material. The ability of the method to resolve the inhomogeneous composition within a single particle in some cases is shown as well.
Funder
Air Force Office of Scientific Research
National Science Foundation
Army Research Office
Publisher
Springer Science and Business Media LLC
Reference60 articles.
1. Kulkarni, P., Baron, P. A. & (eds.), K. W. Aerosol Measurement: Principles, Techniques, and Applications (Wiley, 2011).
2. Sorensen, C. M., Flagan, R. C., Baltensperger, U. & Pui, D. Y. H. Grand challenges for aerosol science and technology. Aerosol Sci. Tech. 53, 731 (2019).
3. Stocker, T. F. et al. IPCC, 2013: Climate change 2013: The physical science basis. in Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (2013).
4. Mahowald, N. et al. The size distribution of desert dust aerosol and its impact on the earth system. Aeolian Res. 15, 53 (2014).
5. Haywood, J. & Boucher, O. Estimates of the direct and indirect radiative forcing due to tropospheric aerosols: A review. Rev. Geophys. 38, 513 (2000).