Electronic speckle pattern interferometry used to characterize monolayer films

Abstract

Electronic speckle pattern interferometry (ESPI) can detect micro displacements and deformation of optically rough surfaces. — Experiments have been performed on pure liquid surfaces and Langmuir films at the airwater interface to determine whether ESPI can be implemented to study liquid surface properties. — Mechanically induced resonant modes of liquid surfaces have been visualized as interference patterns similar to Chladni figures. Oscillation amplitudes on the order of a few microns have also been measured. — The resonance frequency depends only slightly on surface tension and surface pressure, while there is greater correlation between vibration amplitude and the characteristics of the liquid surface. — On the basis of these preliminary results it may be possible to use this technique to detect short wavelength oscillations (<1 mm) and to measure the damping of capillary ripples to obtain the viscoelastic parameters of liquid surfaces.