Microlenses for Calibrating Phase Doppler Particle Analyzers

Simple optical devices called "scattering reticles" have been invented for calibrating Phase Doppler Particle Analyzers (PDPAs), which are optical instruments that analyze scattered light to determine the sizes and velocities of droplets. A scattering reticle comprises a polymeric plano-convex microlens, typically with a diameter of about 60 μm, on a glass substrate about 4 mm thick. In operation, a three-axis positioning stage is used to hold the substrate and move the microlens into the intersection of laser beams that defines the probe volume of a PDPA. The PDPA collects and analyzes the light scattered from the microlens.