Vibration analysis using linearized fringe analysis and video speckle techniques

The amplitude and phase distributions of sinusoidally vibrating object are measured by use of phase modulation and sub-fringe detection. The resulting high sensitivity enables measurements on objects like high frequency transducers, biomedical membranes and cross sections of sound fields in air and water. For the sound recordings, tomographic reconstruction of several cross-sections produces representation of the sound field in any plane desired. The sub-fringe approach also allows analysis of objects vibrating harmonically. In shear interferometry we measure true derivatives as very small shear may be used. Used in Moire systems, large amplitude vibrations can be measured. The integration of the recording media is the main drawback of the video system when used for general vibration analysis.