PHASOR-DIFFERENCE METHOD FOR MEASURING THE AMPLITUDE AND THE PHASE OFSMALL-AMPLITUDE VIBRATIONS WITH TV HOLOGRAPHY

A new, to the author's knowledge, method for time-averaged TV holograp hy measurements of small-amplitude vibrations is presented. In time-av eraged 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 z ero-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 t o determine the amplitude and the phase of the object vibration. The m ethod is demonstrated by the measurement of a vibration mode of a circ ular metal disk. The results are compared with theoretical data and wi th data obtained by a commonly used method in phase-modulated TV holog raphy. (C) 1998 Optical Society of America.