Abstract

Determination of the shape of a liquid surface is an accurate method of measuring the coefficient of surface tension. Françon was the first to show that a shearing interferometer provides a convenient method for the measurement of such liquid surface deformations. Hinsh measured these deformations by holographic real-time interferometry. However water surface deformation has a sharp curvature, so that small f/No. lenses must be used to avoid shadows. Then interferograms of the lens aberration distort the correct evaluation of the deformation. Moreover with large deformations of the liquid surface, too many fringes occur. We therefore need a method that cancels the aberration of the lenses and reduces the number of fringes. A new method to satisfy these conditions is proposed for the real-time measurement of large liquid surface deformation. In this method, a holographic lateral shear interferometer with two three-beam holograms is used. In the experiment, for example, the shearing interferogram was produced when a water strider floated. From the experimental results, it is shown that we can cancel the aberration of the optical system and can change the amount of shear by movement of the hologram.

© 1985 Optical Society of America