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New Optical Method to Determine Vibration-Induced Strains with Variable Sensitivity after Recording,
OAKLAND UNIV ROCHESTER MICH SCHOOL OF ENGINEERING
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A steady-state vibrating object is illuminated with coherent light and its image is slightly misfocused in the film plane of a camera. The resulting processed film is called a time-integrated specklegram. When the specklegram is Fourier filtered, its exhibits fringes depicting derivatives of the vibrational amplitude. The direction of the spatial derivative, as well as the fringe sensitivity may be easily and continuously varied during the Fourier filtering process. Besides the above mentioned advantages, this new method is also much less demanding than holographic interferometry with respect to vibration isolation, optical set-up time, illuminating source coherence, required film resolution, etc. Author
APPROVED FOR PUBLIC RELEASE