This paper reports a method for measuring flow velocity in a microscopic region using a transmission grating. The flow velocity is determined from the measurement of moving particle images on a transmission grating placed in front of a photodetector. These images, formed by a microscopic objective, correspond to particles moving in a flow. The method is used to measure the spatial distributions of the flow velocity in small glass tubes and to compare some of the results with comparable data obtained with differential laser Doppler velocimetry. The resultant distributions are compared with the theoretical flow distributions obtained using the flow rates through the tubes. The results demonstrate that the transmission grating method is useful for measurements of the flow velocity in small probe volumes.
© 1983 Optical Society of America
Tsuyoshi Ushizaka and Toshimitsu Asakura, "Measurements of flow velocity in a microscopic region using a transmission grating," Appl. Opt. 22, 1870-1874 (1983)