Characterizing and monitoring respiratory aerosols by light scattering

The elastic-scattering intensity pattern from a single particle as a function of spherical coordinate angles $\theta$ and $\varphi$ provides detailed information on the pattern’s morphology. By use of an ellipsoidal reflector and a CCD camera, a single-laser-shot intensity pattern from a large angular range ($\theta$ from 90° to 168° and $\varphi$ from 0° to 360°) was detected from a single aerosol (e.g., a Bacillus subtilis spore, a $1‐\mathit{\mu }\mathrm{m}$-diameter polystyrene latex sphere, or a cluster of either of these) flowing through the reflector’s focal volume at 5 m/s. Noticeable differences in the large-angle-range two-dimensional angular optical scattering (LATAOS) suggest that the LATAOS pattern could be useful in differentiating and classifying life-threatening aerosols from normal background aerosols.