Abstract
Measurements of flow velocities using optical techniques have advantages to measure flow velocity in a microscopic region without disturbing it. However the improvement of the spatial resolution in the direction of the optical axis (the depth of the measuring region) is difficult for even the optical techniques.
In this study a new velocimeter with high spatial resolution is proposed. The velocimeter is based on a laser two focus velocimeter (L 2 F) and its optical system is constructed with a confocal system to improve the spatial resolution in the direction of the optical axis. The advantage of the confocal optical system is that the light from the only part within the focal region is detected strongly. The depth of the measuring region of the proposed L 2 F is about 8.2μm. The reliability of the proposed L 2 F is confirmed by velocity measurements of moving a tungsten wire. The results of the experiments show that the proposed L 2 F with the confocal optical system achieves velocity measurements with high spatial resolution and it is extremely effective instrument to measure the flow velocities in microscopic regions.
