ANALYSIS OF A DATA-BASED TV-HOLOGRAPHY SYSTEM USED TO MEASURE SMALL VIBRATION AMPLITUDES

We present a system that measures the full-field amplitude and phase distributions of objects that vibrate with small amplitudes. The system is based on TV-holography combined with sinusoidal phase modulation, discrete vibration-phase shifts, and digital image processing. Different new algorithms, based on a linear approximation of the fringe function, are discussed. Averaging techniques, used to reduce the effects of noise sources and to increase the resolution of the system, are also introduced. For one of the algorithms, tested in combination with the averaging techniques, the amplitude threshold was approximately 1/3000 of the wavelength of the applied laser light. The amplitude resolution was of the same magnitude. The phase accuracy is amplitude dependent and was about 3-degrees for amplitudes greater than 5 nm.