Errors of the shadow image of a lying drop of melt caused by the divergence of illuminating rays

Abstract

With the use of optical digital systems, we analyze the errors in determining the size of a lying liquid drop of melt by its shadow image that are caused by the divergence of illumination rays. Complete elimination or compensation of such errors is impossible. We determine conditions under which one can neglect these errors in comparison with the errors of discretization of the image by the array photodetectors of video cameras. On the optimal use of the array of 2048 x 2048 pixels, the divergence angle of illuminating rays should not exceed 1‡ and, for the array of 512x512 pixels, it should not exceed 2‡. To satisfy these conditions, one should use an optical system with resolving power at the edges of the image two times higher than that of the array photodetector. namely, at least 143 lpmm for the 14 x 14 Μm pixel size, or 250 lpmm for the 8x 8 Μm pixel size.