Whole field in-plane vibration analysis using pulsed phase-stepped ESPI

Electronic speckle pattern interferometry has been used to study resonant in-plane vibrations of a thin square metal plate. An in-plane sensitive arrangement is used with dual-beam illumination from a pulsed laser. Fringe patterns are formed which show a cosinusoidal intensity profile. These fringe patterns inherently carry phase information, which is extracted using the single phase step technique and analyzed to determine the amplitude and phase for the horizontal and vertical components of in-plane vibration. These are automatically combined to yield the total in-plane vibration mode. The final result is displayed as vectors drawn over an image of the object.