This Phase I Small Business Innovative Research Award is for analytical and experimental work on a technique to determine the size and shape of individual gas bubbles suspended in liquids from the measured variation in phase for light scattered at different angles from a single bubble. The analysis will be based on geometrical optics for scattering from spheroidal bubbles. Experiments will attempt to verify the analytical predictions and to validate the deduced bubble size and aspect ratio by comparison with measurement by high speed photography. An instrument for rapidly characterizing bubble sizes, shapes, velocities, and concentrations would find use in studying cavitation in turbomachinery as well as in gas-liquid contacting devices such as fermentors and flotation ponds.