Vol. 41, Issue 1, pp. 109-119

Abstract

Various methods of liquids refractive index measurements were previously developed by others. They differ however in the measurement accuracy, the used light wavelength, the measurement range and the sensitivity to the temperature and pressure. In this work, we present and discuss an acousto-optic technique for measuring the index of refraction of transparent liquid materials. In the proposed technique, a diffraction pattern produced by an acousto-optic interaction is imaged by a liquid lens placed between an optical flat glass and a convergent glass lens. The diffraction pattern consists of two symmetrical dots that are digitized by a CCD camera. The focal shift, which is induced by the liquid sample, produces changes in the position of the diffracted orders. The spatial frequency measurement of the diffractive pattern leads to determine the sample refractive index. The current method presents the advantage to have an adjustable measurement range and can be easily interpreted geometrically.