Laser speckle using smartphone LiDAR

BSTRACTIn this MobiSys demo we present a system to determine fluid properties using the LiDAR sensors present on modern smartphones, as presented in our ACM IMWUT 2022 paper [1]. Traditional methods of measuring properties like viscosity require expensive laboratory equipment or a relatively large amount of fluid. In contrast, our smartphone-based method is accessible, contactless and works with just a single drop of liquid. Our design works by targeting a coherent LiDAR beam from the phone onto the liquid. Using the phone's camera, we capture the characteristic laser speckle pattern that is formed by the interference of light reflecting from light-scattering particles. By correlating the fluctuations in speckle intensity over time, we can characterize the Brownian motion within the liquid which is correlated with its viscosity. Our demo will allow MobiSys attendees to distinguish between liquids of different viscosities, milks of different fat contents, and adulterated milk.