A Portable Multi-Resolution Holographic Particle Imaging System to Improve Awareness of Icing Potential for AAM Operation

This proposed research aims to develop a portable multi-resolution holographic particle imaging system (MHPIS) to achieve real-time, in-situ measurements of shapes and size distributions of airborne supercooled water droplets and ice crystals for improved awareness of icing potential for AAM operation. For the proposed MHPIS, a small-scale, portable 632 nm laser is utilized as the light source, passing a neutral density filter, a spatial filter and a collimation lens to generate a magnified collimated laser beam. The laser beam then illuminates the airborne water droplets/ice particles in the measurement region to form a magnified diffraction pattern on the image plane of a camera. If the scattered wave from the airborne droplets/particles is small compared with the unscattered reference laser wave, the interference pattern on the image plane forms a hologram. The hologram is stored as 2D digital images and then will be reconstructed to generate 3D information of the droplets/particles by Kirchhoff–Helmholtz transform. The multi-resolution is achieved by changing the distance between the measurement region and the camera. The in-situ measurement data can be fed into icing prediction modules to realize real-time icing prediction. Due to its compact size, lightweight and cost-effective characteristics, the proposed MHPIS can be easily integrated into any AAM vehicle to measure the airborne supercooled water droplets and ice crystals in the icing clouds up to 3,000 feet in altitude to collect spatially dense observation data within a cubic region of width of 300 feet. As a result, the MHPIS can provide a set of enriched statistical data on icing-related parameters for more accurate icing prediction. Compared to traditional icing observation systems and icing sensors, the proposed MHPIS is a breakthrough technique for evaluating icing potential to ensure safer and more efficient AAM operation under all weather conditions.