Laser doppler field sensor for two dimensional flow measurements in three velocity components

The laser Doppler field sensor presented in this paper is suited for high resolution flow velocity field imaging on the micro scale without use of a camera. The field sensor is constructed by the superposition of two laser Doppler velocity profile sensors. The profile sensor is based on the principle of Laser Doppler Anemometry (LDA). However, instead of one parallel fringe system one divergent and one convergent fringe system are employed. Utilizing a total number of four fringe systems the field sensor can determine the tracer particle position two-dimensionally in the measurement volume. The spatial resolution and velocity accuracy are increased compared to conventional LDA by more than one order of magnitude. Since no camera is used, the resolution of the sensor is not influenced by pixel size effects. Two-dimensional velocity field measurements of an injection nozzle flow and of a micro channel flow with quadratic cross section are presented.