A method is described for measuring flow velocity in a microscopic region by means of a differential-type laser velocimeter with a transmission grating. The principle of this velocimeter is described on the basis of spatial filtering of the transmission grating. The filtering characteristics are theoretically analyzed using a power spectral density function. The velocimeter is used to measure flow velocities and their spatial distributions in a small (700-µm diam) glass tube. The theoretical and experimental results show that this differential-type velocimeter is more suitable and practical than the conventional one for measuring the flow velocity in a small probe.
© 1985 Optical Society of America
Yoshihisa Aizu, Tsuyoshi Ushizaka, and Toshimitsu Asakura, "Measurements of flow velocity in a microscopic region using a transmission grating: a differential type," Appl. Opt. 24, 627-635 (1985)