Reconstruction of Aerosol Properties from Forward-scattering Intensities

摘要

This work describes the design and application of an apparatus to image aerosol particles using digital holography in a flowthrough, contact-free manner. Particles in an aerosol stream are illuminated by a triggered, pulsed laser and the pattern produced by the interference of this light with that scattered by the particles is recorded by a digital camera. The recorded pattern constitutes a digital hologram from which an image of the particles is computationally reconstructed using a fast Fourier transform. This imaging is validated using a cluster of ragweed pollen particles. Examples involving mineral-dust aerosols demonstrate the technique's in situ imaging capability for complex-shaped particles over a size range of roughly 15-500 micrometer. The focusing-like character of the reconstruction process is demonstrated using a sodium chloride (NaCl) aerosol particle and is compared to a similar particle imaged with a conventional microscope.