Heterodyne Holography for Vibration Analysis.
Final technical rept. 1 Sep 79-1 Aug 80,
BROWN BOVERI RESEARCH CENTER BADEN (SWITZERLAND)
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The basic problems of quantitative determination of mechanical strain of vibrating object through holographic interferometry are discussed. Time-average holography, which is most commonly used for holographic vibration analysis, can not be combined with heterodyne evaluation, since the interference fringes are already frozen in the hologram. Synchronized double-pulse holography can be employed in the same manner as pulsed double exposure holography. Moreover, real-time holography allows to investigate the temporal behaviour of vibrations, but only at one or a few points sitaneously, depending on the number of detectors employed. Both methods were tested. The method uses essentially heterodyne holographic interferometry for the quantitative determination of the surface displacement from the fringe pattern in the image plane. Finally, a nearly fully automated camera with photothermoplastic film is presented to achieve fast and dry in-situ recording and processing of holograms with high diffraction efficiency. Author
- Test Facilities, Equipment and Methods