Optical Diagnostics in Epigraphy

This work is the result of a collaboration between the University of Graz, Department of Classics, Section of Ancient History and Epigraphy, and the Graz University of Technology, Institute of Experimental Physics and the Institute of Thermal Turbomachinery and Machine Dynamics, Working Group Metrology in Turbomachinery - Laser Optical Metrology.

ABSTRACT: In 1990, the late ancient historian Mortimer Chambers presented a work in which a weathered inscription was made visible by a laser beam shining through a 19 cm thick marble slab from behind. Criticism was not long in coming and read: “Through a laser beam darkly”. But was the criticism justified? This work attempts to answer the question of whether and how it was possible thirty years ago to make the invisible visible using a laser beam, but now with the help of various methods of highly developed modern measurement technology, with a special focus on methods that can also be used in field research. For this purpose, a marble stone with an epitaph from the 4th century A.D. was examined under laboratory conditions. This research led to the conclusion that in 1990 it was possible to make a weathered inscription visible by shining a laser beam through a block of marble, and that it is probably color pigments deep within the object that are seen as shadows when the marble is backlit by a laser beam.

本研究成果由格拉茨大学古典学系古代史与铭文学教研室，与格拉茨工业大学实验物理研究所、热力涡轮机与机器动力学研究所下属涡轮计量学——激光光学计量学（Laser Optical Metrology）工作组合作完成。

摘要：1990年，已故古代史学家莫蒂默·钱伯斯（Mortimer Chambers）发表了一项研究，其中通过从后方照射穿过19厘米厚大理石板的激光束，使一处风化铭文显现出来。批评之声很快接踵而至，称其“透过激光，朦昧难明”。但该批评是否合理？本研究旨在解答如下问题：三十年前，借助激光束使不可见之物显现的方法是否可行、又是如何实现的；而如今，我们可依托高度成熟的现代测量技术各类手段开展相关研究，其中特别聚焦于可应用于野外研究的技术方法。为此，我们在实验室环境下对一块带有公元4世纪墓志铭的大理石试样进行了检测。本研究得出结论：1990年，通过激光束穿透大理石块使风化铭文显现的方法确实可行；当激光从背面照射大理石时，物体内部深处的彩色颜料会以阴影的形式被观测到，这大概率是该现象的成因。