Multi-frequency laser beam using in an interferometer vibration measuring system

摘要

It was discussed the using multi-frequency YAG:Nd infrared laser for long range non-destructive acoustic vibration measuring system for structural modal analysis. It was shown both theoretically and experimental that a coherent function of a laser with acoustooptic device has an oscillations with the period depending on a laser cavity length and a number of resonator modes. The advantages of using the acoustooptic devices in a tandem scheme were discussed. The adjustment of such system due to on-axis shift is suitable for object selection. It was shown that the coherence function has optimal form for selecting a transparent object on light beam trace and optical delay line for semiconductor laser with short resonator can tune on maximum of coherent function at long distance. Accordingly the mutli-frequency laser can be used in heterodyne optical scheme instead of more costly stable one-frequency laser. A simple scheme of velocity measuring based on a semiconductive two-mode laser was proposed. Conclusions regarding the possibility using the resonator with acoustooptic device inside with a frequency chirp beam using for interferometer phase modulation measure system are arrived at. The application of a frequency-shifted laser beam to practical optical measuring system may improve the processing efficiency without additional adjustments.