A Bessel beam laser Doppler velocimeter

We present a laser Doppler velocimeter that is based on the use of two intersecting Bessel beams instead of the conventionally used Gaussian beams. Due to the quasi non-divergent nature of the Bessel beams, a short effective measurement volume of about 40 μm length could be realized with a low fringe spacing variation of 0.3%. Both of these advantageous values were experimentally verified in flow measurements.