Laser diode for flow-measurement

Abstract

A simple laser diode, without lenses, is demonstrated as a flow sensor. The diode is placed directly on the edge of the duct, exploiting the natural laser divergence. The flow-measurement is based on the Doppler shift induced by the scattering particles inside the fluid, read by the self-mixing effect inside the laser diode. The proposed approach was modeled by a numerical simulation, in order to find the best signal processing algorithm. Finally, a set of measurements have confirmed the sensor performances as flow-meter.