Integrated optical microsystem based on Talbot interferometry for the measurement of particle concentration in tubes

We demonstrate an integrated system for the measurement of partilce volume concentration in flowing suspenstions of water and test dust. The measurement is based on Talbot interferometry and we show an analytical model to determine suitable system parameters. We show the realization of the microsystem that consists of two parts: a planar emitter-receiver-unit comprising a VCSEL at 850 nm as light source and photodiodes and a PMMA-module. A flexible tube is embedded therein and the optical functionalitiy is realized by a micromilled lens surface for light collimation and a Ronchi grating for the generation of the interfering diffraction orders. We discuss the multiplexing of the system for the determination of particle size distributions.