Blood flow detection with diode laser

The method for blood flow velocity registration is proposed. An optical coherent photodetection based on self-mixing in a diode laser has been used. An experimental device with pigtail laser diode was investigated. This device is tested by registration of flow of the liquid suspension containing polymer microspheres with spheres diameter 7.0 microns and density 1.05 g/cc was used instead of real blood and proved to be able to measure velocity of liquid suspension containing particles with size of erythrocytes. The self-mixing that occurs in diode laser cavity when the radiation scattered-back by the particles into the laser interferes with the field inside it and causes a changes of a laser pump current. National Instruments DAQ board and LabView for Windows are used for output signal digitalization and processing purposes. Described device as application of self-mixing method highlight the significant advantages of simplicity, compactness, and robustness as well as the self-aligning and self-detecting abilities of such method when compared with the use of conventional optical coherent methods