Automatic System for Annual Ring Width Measurement and Application to Ancient Wooden Cultural Properties

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The basis of any dendrochronologic research is to measure annual ring width to an accuracy of 10 μm. Conventional annual ring readers were stationary devices with a binocular microscope and often stationed in research labs, therefore they presented certain limitations in measuring actual specimens. Accordingly, in order to expand the scope of application to a wider and more diverse range of ancient wooden cultural properties. it is necessary to consider other methods of measuring annual ring width.Our objective was, in this regard, to build a semi-automatic system for measuring annual ring width. In this project, we developed such as system that uses the latest optical technology to indirectly obtain an image of the annual rings rather than directly measure ring width on the actual object. The tested equipment included a silver salt camera, digital camera, scanner and soft X-ray photography. It was learned that, of these devices, the most suitable for a wide range of ancient wooden cultural properties was a high resolution digital camera.The method we employed to measure annual ring width was to import the ring image captured with a digital camera into a computer and perform measurements with purpose-specific software that was developed in this project. The method was very effective and, though some corrections are needed with the software, we expect this to become the mainstream in annual ring width measurement.As part of this project, the age of honden (main shrine) and haiden (altar) of Ujigami-jinja Shrine, a National Treasure located in Uji, Kyoto, was measured using a single lens reflex digital camera of 11 M effective pixels. Results confirmed that the main shrine had been built in about 1060 A.D. and the altar around 1290 A.D.The fruits of this research project can be applied to many old architectural members, wooden sculptures of all sizes and a diversity of artworks, and should play a major role in research into architectural and art history.