Phasor-Difference Method for Measuring the Amplitude and the Phase of Small-Amplitude Vibrations with TV Holography.
A new, to the author's knowledge, method for time-averaged TV holography measurements of small-amplitude vibrations is presented. In time-averaged TV holography with sinusoidal phase modulation of the reference arm of the interferometer, two phasors describe the object vibration and the modulation of the reference arm. By inversion of the squared zero-order Bessel function of the first kind, it is possible to measure the distance between these two phasors. The distances from an object-vibration phasor to a number of known reference phasors are measured to determine the amplitude and the phase of the object vibration. The method is demonstrated by the measurement of a vibration mode of a circular metal disk. The results are compared with theoretical data and with data obtained by a commonly used method in phase-modulated TV holography.
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