Depth discrimination of polarized light is used in investigating laser Doppler measurement of the superficial
microcirculation in tissue. Using polarization Monte Carlo simulation, temporal point spread function and power spectral
distribution of backscattered polarization remaining light firstly are used to prove polarized light to be valid in measuring
moving blood cell perfusion and mean flow velocity. Then simulation of layered medium model demonstrate that
relationships between blood flow perfusion and mean frequency shift are linear to medium flowing velocity, and the Doppler
shift information in polarization remaining light mainly comes from lower layer medium up to about 14 times of mean free
path (MFP) of medium investigated and can be considered that Doppler effects come only from lower layer of the medium.
Simulations in three-layer tissue model show that moving blood cell perfusion and mean blood cell moving velocity
calculated from polarization remaining are much more sensitive to lower layer flow velocity variation, and more irrelevant to
deeper layer flow rate fluctuations, that further confirms Doppler measurement from polarization remaining light to be
effective for superficial microcirculation in tissue. Factors affecting Laser Doppler measurement like medium absorption,
percentage of moving particles in blood detector size are discussed.