Analysis of blood flow covering a wide region of velocity in laser speckle image sensing

•Selection of blood flow estimation parameter depends on user’s experience.•A novel method for automatic selection of a proper parameter is proposed.•Experimental results show the feasibility of the proposed method.

Imaging technique based on bio-speckles is useful for visualizing blood flow distribution. We have proposed so far temporal contrast factor (TCF) and inversed temporal contrast factor (ITCF) for imaging of slow and fast blood flows, respectively. However, selection of TCF and ITCF depends on user’s experience. Additionally, these parameters are significantly influenced by the speckle contrast and random noises. In the present study, we propose a method for automatic selection of a proper parameter for imaging blood flow in an unknown velocity region with reduced effects of speckle contrast and random noises. Experiments are conducted for a sample model using ground-glass plates, human wrist, and human finger to confirm the feasibility of the proposed method.