Digital holography instrument for in-situ coarse-mode aerosol imaging, sizing, and classifying

Digital holography is a contact-free imaging method that can work with a naturally flowing air stream. We have built a prototype model for a lightweight, low-cost digital holography instrument that can image coarse-mode aerosol particles, sizes ranging from tens of micrometers up to millimeters, in the atmosphere. We have also developed the necessary algorithms to automatically reconstruct the particles' two-dimensional silhouettes, with some additional three-dimensional information[1]. The eventual objective is for the particle classification to be done in real time on board the instrument. The instrument will be flown on a DJI Matrice 600 Pro or another drone with a similar payload capacity.

The instrument concept will allow imaging large atmospheric particles almost anywhere in the lower boundary layer with minimal set-up required, and with very low operational costs. We expect the instrument will greatly add to the knowledge of coarse-mode aerosol particle morphology, and we hope to create an aerosol shape database that can be used to improve various atmospheric simulations and retrievals.

References [1]Kemppinen, O., Heinson, Y., Berg, M. J., 2017: Quasi-three-dimensional particle imaging with digital holography. Appl. Opt. 56, F53-F60.