| 摘要 |
<p>The appts. to measure the speed of a liq. in anisotropic flow with a free surface working on the basis of the doppler effect difference between two coherent light beams emitted by the same lazar. The appts. includes a diffraction grating in the form of a rotating disc placed in the path of the slightly divergent primary beam from the laser. The disc is driven by a motor at a predetermined speed. The two secondary beams emerging from the diffraction grating are rendered parallel by a bi-prism. The beams enter a water-tight pipe which terminates in a converging lens. The focal point of the lens where the beams cross is the measuring point. A fibre optic placed at this focal point and connected to a detector enables the light at the focal point to be determined and hence the flow rate. The trajectories of the light beams in the liq. are very short, close together and constant. All the elements necessary for the direction of the beam are fixed solidly in one easily orientable block. The lasar (1), the rotating disc(5), the bi-prism (10) and the water-tight tube (13) are all fixed rigidly to a frame which can be positioned and orientated easily in relation to the liquid.</p> |
