FEBRUARY 7--Frank Fueten, an associate professor in the department of earth sciences at Brock University (St. Catharines, Ontario, Canada), has designed a fully automated polarizing stage for a petrographic microscope, which allows a thin section of rock to remain fixed while the polarizers are rotated. As a result, any point within a grain is registered to the same pixel at all positions of the polarizers, simplifying the computational requirements. The polarizing stage is used in conjunction with an off-the-shelf computer, camera, and video capture board. By selectively obtaining data from images with different polarizer positions, the polarizing stage greatly enhances the potential for petrographic image processing.
According to Fueten, full sampling of 200 frames under crosspolarized light and constructing the final data set data takes less than 30 seconds on the Pentium 4-based host. The design of the polarizing stage allows the system to identify mineral types, measure grain size and shape, and provide crystallographic orientation data.
For more information, seeVision Systems Design, February 2002.