A new automatic ice-fabric analyzer which uses image-analysis techniques

Abstract

AbstractAn automatic ice-fabric analyzer has been developed, which can determine individual ,-axis orientations by image-analysis techniques. The analyzer consists of four major components: a sample stage, a pair of crossed polaroids, a charge coupled device (CCD) camera and a light source. Both the sample stage and the crossed polaroids can be rotated independently of each other by the stepping motors controlled by a personal computer (PC). Measurements are conducted as follows. An ice thin section is set on the sample stage and then the crossed polaroids are rotated. Thin-section images are recorded by the PC at intervals of 2° of rotation. From the image-intensity (gray value) dataset of each crystal in the thin section the extinction angles of individual crystals can be determined. Similarly, eight other extinction angles of individual crystals are obtained from eight other CCD camera positions with respect to the thin section: Finally, the .-axis orientation of individual crystals is calculated by using these extinction angles. With this technique, all crystals within the view of the CCD camera can be analyzed at the same time. In addition, with image-processing techniques the individual crystals are recognized automatically and other parameters, such as grain-size and grain shape, can be measured simultaneously. Textural studies of Dome Fuji (Antarctica) ice cores have been conducted with this analyzer.