Physically-based digital restoration using volumetric scanning

Digitization has become critical to preservation, dissemination and even restoration of damaged artifacts of cultural history. There are a number of priceless documents of cultural heritage that are preserved in museums and libraries with content that is still difficult for modern scholars to see. Their opaque surfaces in rolled or folded forms, such as scrolls and bound manuscripts, prevent their content from being accessed. Physical unwrapping is usually not considered as a solution due to its destructive nature, especially for the aged and damaged materials that are in fragile condition.This thesis develops a general approach for building a readable image of an opaque, rolled or folded document from a non-destructive volumetric scan. We use a custom high-resolution Computed Tomography (CT) scan to solve the problem of opaque document acquisition, based on an extensive analysis of the important issues specifically related to this application.The post-processing problem is framed by localizing, constructing and manipulating a texture image induced by a surface embedded in a 3D voxel space. Algorithms are developed to localize the surface present in a scan, construct a texture map that reproduces the ink on the surface, and parameterize the convoluted surface over a 2D domain that enables a complete reading. The “virtual unwrapping”, based on simulation of mass-spring system dynamics that is found on classical mechanics, preserves geometric features, such as angles and lengths, thus minimizes the distortion of text.For preliminary testing and empirical analysis of the restoration method, we conduct a series of simulation experiments based on a CT scanner simulator. Satisfactory experimental results on replica scrolls and a real 15th manuscript from the University of Michigan's Library promise feasibility of this method. The content of the ancient manuscript revealed by our method is confirmed by posterior physical manipulation, which permanently altered the object. This research presents novel contributions that are expected to benefit the scholarship that studies human history and culture. The vision is to apply the proposed method ultimately to precious documents and allow complete analysis of them while enforcing continued physical preservation.Keywords. Computer Graphics, Computer Vision, Historic Preservation, Digital Restoration, Opaque Documents