S.V. Mikhlyaev (Russia)
Image processing, diameter measurement, crystal growth
In this paper the approach for measuring the diameter of a Czochralski growing crystal based on digital image processing is considered. The diameter of a crystal is determined as a result of digital processing of image sequence formed by video camera during the rotation of a crystal. The method includes detection of boundary points between a melt and a crystal, compensation of perspective distortions of the images and approximating of boundary points by a circle. We use a few improving estimations of the diameter and the centre of a crystal and apply filtration of boundary points appropriate to crystal facets. By modeling and analytical calculations it is shown that the offered method of the diameter measurement is more preferable in comparison with the usual one based on detection of three boundary points and their approximation by a circle. The measurement errors produced by three-dimensional nature of the analyzable scene and by parallax of optical system are considered.
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