Assessment on Self-mixing Laser Interferometry for Blood flow Measurement over Skin Surface

We study self-mixing laser diode (SM-LD) as a low-cost and compact optical sensor for non-invasive blood flow measurement and profiling over the skin surface. By making in-vivo and in-vitro measurements, we compare the SM-LD based sensor with the commercially available flowmeters to assess the accuracy and feasibility of SM-LD sensors for such applications. For the SM-LD based sensor, we apply two different signal processing methods: (i) counting the intensity fluctuations of the signal from the SM-LD to obtain a frequency value; and (ii) the autocorrelation of the signal. In-vitro measurements show good agreement with the commercially available flowmeters. In-vivo measurements performed on test subjects revealed that autocorrelation technique shows much better results than the counting technique in blood flow profiling and SM-LD based sensor suffers from errors caused by external artifacts during measurements