Cross-Correlation-Based Optical Flowmeter

In this paper, an optical flowmeter based on the cross-correlation technique is proposed. Two parallel laser beams are made to cross a transparent pipe wherein a turbulent air flows. The laser beams are detected by two position-sensitive detectors (PSDs) whose output signals are processed by software. The cross-correlation function between the signals is calculated, which yields the time delay between them. The flow velocity is then obtained by the ratio of the distance between the laser beams to the time delay. The flowmeter is applicable for measuring human respiratory flow in a noninvasive way. An experimental prototype is built, and results are provided. A detailed description of the experimental setup and of measurement procedures are presented and discussed. Results have been very promising and have shown the potential of the system developed here in performing human respiratory flow measurements, particularly those suitable for neonates.