| 摘要 |
For the optical measurement of flow vectors in gas currents, two substantially parallel light beams are focused at separate focusing points. The particles traversing the one focusing point are illuminated and thus generate start pulses, while particles traversing the other focusing point produce, as they flash up, stop pulses. By means of such a process, it is possible to determine the component of the flow vector (v) extending in the normal plane to the vertical axis (OA). It is an object of the invention to detect by simple means also the flow vector component extending in parallel to the optical axis (OA). According to the invention, focusing points (FG1, FB2; FB1, FG2) of beams (S1, S2) with different focal distances are produced. In a first measurement (A), the straight line traversing the focusing points (FG1) and (FB2) is formed at an angle ( gamma A) to the normal plane of the optical axis. In a second measurement (B), the straight line traversing the focusing points (FB1, FB2) is produced at an angle ( gamma B= gamma -A) which has an index opposite to that of the first angle. By forming the difference between the two measuring rates, the flow angle ( beta ) is determined with respect to the plane normal to the optical axis (OA).
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