The Color of Aerosols: In Situ Imaging with Color Digital Holography

MATTHEW BERG, Kansas State University

     Abstract Number: 250
     Working Group: Aerosol Physics

Abstract
Light-scattering techniques are commonly used to characterize micron and submicron particulate matter, such as aerosols, in a rapid and contact-free way. A typical objective is to infer the size and shape of particles from their light-scattering patterns. While this approach can be useful for simple shapes, difficulties arise for large irregularly shaped particles. An alternative, well-suited for large particles, is digital holography. A particle is illuminated by a beam and the interference pattern produced by unscattered and scattered light is recorded by a sensor. The pattern is the hologram, and from it, an image of the particle can be rendered computationally. Using red, green, and blue lasers along with a color sensor enables color holograms of particles, from which color images can then be generated. We have applied the method to an aerosol of mineral dust particles and can categorize different minerals according to the colors observed at the single particle level. The method shows promise as a means to encode aerosol-particle material information into a digital hologram, which could advance our aerosol characterization capabilities.