USING OPTICAL COHERENCE TOMOGRAPHY TO EXAMINE THE SUBSURFACE MORPHOLOGY OF CHINESE GLAZES

Optical coherence tomography (OCT), a new method for ceramics research, is a nondestructive, three‐dimensional tomography system, which provides subsurface morphology visualization of samples based on the refractive index or dielectric constant differences in the target specimen. In this study, seven shards from different Chinese kilns of Song and Yuan dynasties (10–14th centuries) were scanned to visualize the subsurface morphology of their glazes. The images revealed unique phase assemblage modes in different samples. The results suggest OCT may be used to identify ceramics and provide information about their manufacturing technology.     

AN APPRAISAL OF THE PROBLEMS INVOLVED IN THREE-DIMENSIONAL GROUND PENETRATING RADAR IMAGING OF ARCHAEOLOGICAL FEATURES

There are a number of problems that are due to the physics involved in the ground penetrating radar (GPR) technique which result in the recorded data giving a distorted representation of the true subsurface structure. Many of these problems are reduced by the experience of the person interpreting the data. This paper is an attempt to remove some of the subjectivity from this process by considering how the distortion in the data could be reduced by applying a migration routine. The amount of data, and the time needed to collect it, place a restriction on the use of the migration process to two dimensions only and result in a compromise approach to the use of GPR. This compromise may, however, result in better integration of GPR with the other geophysical techniques available.     

The Use of Optical Coherence Tomography for Monitoring the Subsurface Morphologies of Archaic Jades

We demonstrate the use of the Optical Coherence Tomography (OCT) technique for non‐invasive scanning of the subsurface morphologies of jade objects. The two‐dimensional tomography images show the refractive index or dielectric constant variations in the samples, reflecting their structures. Three samples of archaic jade objects from the Qijia and Liangzhu cultures in China are scanned in order to understand the subsurface morphologies of the naturally whitened jades. Also, two jade objects with artificial treatments (burning) are scanned and compared with the original materials in subsurface structures. In the original objects, the jade materials can generally be quite transparent, such that the backscattering intensity is weak, although the large‐scale (tens of microns or larger) subsurface morphology can be clearly observed. After burning, small‐scale (smaller than a few microns) structures are formed and the backscattering intensity is enhanced. In this situation, the large‐scale structures may be preserved or even newly generated. On the other hand, in an archaic object with natural whitening, small‐scale structures are also formed. Hence, the deeper distributions of significant backscattering intensity are observed, when compared with the unwhitened objects. Nevertheless, the large‐scale features diminish during the whitening process. With OCT scanning, such differences in subsurface morphology can provide us a valuable reference for authenticating archaic jade objects.