In order to measure the local velocity field in opaque fluid flows like blood flow, a new laser Doppler velocimeter having a pickup consisting of a small distributed index lens attached at the tips of two fibers which are joined side by side in parallel has been newly developed. The distributed index lens is in the shape of a truncated cone. The flow field around this sensor has been measured very precisely by means of an ordinary LDV. The effect of turbidity of fluid on the quality of the laser Doppler signal from this sensor has been examined by experiments. As a result, it has been shown that this LDV sensor has a high signal-to-noise ratio, and that the disturbance against flow by the sensor is very small, and it is very promising as a velocity sensor for opaque or semi-opaque fluid flow like blood flow.

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