Development of miniaturized FDM and WDM Laser-Doppler velocity profile sensors

We report about a novel Laser-Doppler velocity profile sensor with high spatial resolution in the micrometer range. The sensor can be used for applications in fluid mechanics, e.g. flow measurements. Miniaturized sensors are often necessary to measure outside the laboratory. One approach utilizes a diffractive optical element (DOE) in order to reduce the number of optical elements. Another approach utilizes a frequency division multiplexing, where the frequency of multiple laser diode beams are controlled and superposed. Both approaches are discussed and compared.