Fast Atmospheric Aerosol Size and Shape Imaging Instrument: Design, Calibration, and Intelligent Interaction

Abstract

Atmospheric aerosol particles have a significant impact on radiation, climate, and human health, with their size and shape being fundamental physical parameters for atmospheric change research. Due to the widespread effects and applications of aerosol particles, the direct measurement of aerosol size and shape has become crucial. Nevertheless, several challenges persist in aerosol measurement instruments, including limited resolution, complex operation, poor synchronization, and inaccurate inversion methods. Therefore, we developed a new scientific instrument and corresponding image intelligent interaction system, whose name is the fast atmospheric aerosol size and shape imaging instrument (FASI). The instrument is designed for transmission imaging that contains a light source, imaging chamber, microscope objective, tube lens, extension tube, camera, etc. Before the operation, the FASI calibrates background field, pixel size, characteristic gray value (CGV), and depth of field (DOF) based on image processing. During intelligent interaction, the FASI extracts aerosol particles by image denoising and edge detection, and then uses our proposed defocus and duplicate particle detection algorithms for secondary screening of aerosols. Aerosol size and shape parameters are measured in parallel by the central processing unit (CPU) and the graphics processing unit (GPU) using heterogeneous computation. Polystyrene latex (PSL) calculations and quantitative experiments indicate that FASI can accurately detect 0.5– $20~\mu $ m aerosol particles. In particular, the FASI measures aerosol particles supplied by an aerosol generator, dryer, and neutralizer, demonstrating that the aerosol size distribution range of oil solutions (0.5– $3.5~\mu $ m) is narrower than that of aqueous solutions (0.5– $7.5~\mu $ m). For all samples, 92.12% of aerosols have an aspect ratio (AR) exceeding 1, and the shape of these nonspherical aerosols varies greatly from each other. The evaluations of computational efficiency indicate that the FASI is capable of near-real-time operation at 20–35 frames per second (FPS). This instrument has the advantages of noncontact, stable, fast, accurate, and simultaneous automatic measurement of aerosol particle size and shape, which can help solve some key scientific problems related to climate and environmental effects.