Single Lens Based Schlieren Microscope for Investigation of Buoyancy-Induced Convective Field Around a Crystal Growing from its Aqueous Solution

ABSTRACT

The present work describes the development of a single lens schlieren microscopic system for imaging of convective field around a crystal growing from its aqueous solution at a microscopic level. The system differs from the conventionally employed schlieren method in a way that it employs a spreading beam of light to scan the area of interest and a high magnification objective lens with a very short focal length to get magnified images of the test objects. The applicability of the method has been demonstrated by imaging the buoyancy-induced convection currents around a Sodium chlorate (NaClO₃) crystal growing from its aqueous solution in free convection regime insitu. Coupled with the imaging technique, principles of tomography have been employed to quantitatively determine the three-dimensional distribution of concentration field around the growing crystal. Results have been presented in the form of schlieren images of the convective field around the growing crystal recorded using the developed optical set up, path-averaged salt concentration distribution as deduced from the microscopic schlieren images and local concentration distribution at various horizontal planes above the growing crystal using the principles of tomography.

Keywords: Schlieren, Microscopic imaging, Growth from aqueous solution, Computed tomography, Fanbeam configuration.

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