Laser Doppler measurements of blood flow in skin tissue

Measurements of blood flow in skin tissue have been made using a low power helium neon laser, with a pair of multi-modal plastic optic fibres to transmit the laser radiation to the skin, one similar fibre to collect the scattered laser radiation, and photodiode detection. Before transmission to the skin surface one of the laser beams is frequency shifted by reflection from a moving corner cube, enabling the experimenter to distinguish between low frequency blood flow dependent signals having a Doppler shift origin, and those low frequency signals generated by other sources of intensity fluctuation such as fibre movement, number fluctuations and laser amplitude modulation.