| Summary: | 碩士 === 國立臺灣大學 === 應用力學研究所 === 87 === An innovative optical metrology instrument, called “Multifunctional Dual Focal Point Laser Doppler Anemometer (LDA),” is the main focus of this dissertation. Tasks intended for this newly developed instrument include measuring turbulence scale, velocity gradient, and rotational velocity, etc.
Ease of use, low cost, and maintain maximum common light-beams paths are some of the primary design features of this new breed of instrument. Another innovation lies on the fact that the distance between the two measurement points can be adjusted at ease anywhere from 0 to 10mm continuously.
In summary, the multifunctional dual focal point laser doppler anemometer invented within the course of this dissertation possesses four measuring modes. The first mode measures the difference of x-axis velocity between two measurement points located along the x-axis. The second mode measures the difference of x-axis velocity between two measurement points located along the y-axis. The third mode measures the difference of y-axis velocity between two measurement points located along the x-axis. The fourth mode measures the difference of y-axis velocity between two measurement points located along the y-axis.
Furthermore, this dual focal point LDA was shown to be able to accommodate the de-polarization effect induced by the measurement surface on the incident light beam. The performance of the dual focal point LDA prototype was experimentally verified to satisfy all major intended design features of the system. The fundamental design thinking, practical implementation limitations and trade-off are all detailed throughout the dissertation as well.
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