Hybrid flow velocimeter measurements of transparent and turbid liquids in a microchannel using a transmission grating.

A Doppler velocimeter with a transmission grating was developed for flow rate measurements inside a microchannel. This velocimeter has the same optical setup as a recently developed flow velocimeter for transparent liquids, in which two beams (pump and probe) optically coupled to a fiber were used. Although the principle of the flow velocity measurement was quite different between the two methods, the optical setups used were almost similar; the differences are that only the probe beam is used and fast Fourier transform analysis is utilized for the signal processing in the new technique. This development offers hybrid flow velocimeter for both transparent and turbid liquids.