The multi-point laser Doppler velocimetry (MLDV) is an established method for measuring the microcirculatory blood flow. The LDV can noninvasive measure the absolute blood flow velocity in measurement region in skin. In general, the fringe pattern was created in intersection region [i.e., measurement region] by two laser beams. However, the influence of skin structure to give the laser beams and measurement results was not discussed. In this paper, we observed photographs of the interference fringes formed in subcutaneous tissue of chicken. In the case of narrow position in skin, fringe pattern was almost kept but it becomes an interference pattern like a laser speckle pattern in deeper position. It is shown that the fringe pattern including speckle pattern is formed at the intersection point. As these results, we can show the limit of depth in the skin related to the fringe or speckle pattern and intensity of Doppler signals.
