Reflection suppression by polarization in backscatter LDA measurements near walls and in two-phase flows

A method is proposed and verified by experiments to suppress disturbing reflections in laser Dodppler anemometer (LDA) measurements. Disturbing reflections occur in a variety of practical applications of LDA, such as backscatter measurements near walls or in two-phase fluid or particle velocity measurements. The method uses circularly polarized light that changes the handedness when reflected and is quenched by a suitably oriented polarization analyzer. Scattered light, however, is partially transmitted by the analyzer to give undisturbed seeding particle signals. Verification experiments have been performed to demonstrate the method; systems for practical applications are proposed.