Abstract
An automatic ice fabric analyzer has been developed to determine individual c-axis orientations by image-analysis technique. The analyzer consists of four major components: a sample stage, a pair of crossed polaroids, a CCD (Charge Coupled Device) camera and a light source. Both the sample stage and the crossed polaroids can be rotated independently by the stepping motors controlled by a personal computer. Measurements are conducted as follows: an ice thin-section is set on the sample stage, then the crossed polaroids are rotated while the thin section images are fed into the personal computer at intervals of 2 degrees of rotation. From the image intensity (gray value) data set of each crystal in the thin-section, the extinction angles of individual crystals are determined. Similarly, eight other extinction angles of individual crystal are obtained from eight CCD camera positions with respect to the thin section. Finally, the c-axis orientation of individual crystal is calculated from these extinction angles. With this technique, c-axes of all crystals inside the view of the CCD camera are automatically analyzed within a short time (about 20 min.), together with the data of grain size, grain shape and other parameters.
