Recent advances in self-mixing laser-doppler velocimetry: use as an in-vivo blood flow meter

In the present paper, recent experimental advances obtained with a laser Doppler self-mixing velocimeter are reported. The self-mixing effect in a semiconductor laser is used to realize the velocimeter. The velocity is calculated measuring the frequency peak of the frequency spectrum of the intensity signal generated by the laser diode when modulated by feedback light coming from the moving scattering particles. A special optical fiber version of this velocimeter to be used specifically for intra-arterial blood velocity measurement has been realized and a solution for reducing temperature influence on the semiconductor performances is proposed. The results of the in vivo tests carried out with the proposed sensor are presented.