Interference fringe-patterns association to defect-types in artwork conservation: an experiment and research validation review

摘要

The paper is directed to all classes of optical inspection technologies that are causing a fringe pattern like output, such as interferometry, fringe projection, holography, speckle techniques. The explanations given here are also valid for incoherent fringe projection, moire, and short-coherent techniques, which are producing fringe-like output correlated with the surface structure and the surface change, respectively. Identification of interference fringe patterns with defect type is a long-standing engineering problem with the ambiguities in cause-effect relation dominating the Cultural Heritage structural diagnosis. The ambiguities refer to fringe-pattern formation in regard to a hidden defect cause in the subsurface and the effect on the surface of the size or depth of the defect. In order to solve the concerned ambiguities, a review is made here to be confirmed a correlation of fringe pattern appearance to defect cause. The methodology is employed in the paper to achieve a generalized description of fringe morphology for a common type of inner defect as in-terlayer de-cohesion termed in art conservation as detachment and crack. The objective is to provide the required concept and procedure through which the validation of any defect-indicative fringe-pattern can serve as a direct-visual-control of structural condition in artwork examination. In this context, theoretical and experimental results starting from simulation algorithms, through knowledge based experiments and experimental verification to correlation procedures and mathemati- cal analysis are combined to allow fringe pattern generalized validation. The result allows performing by means of modern optical metrology direct artwork documentation of structural diagnosis in complex art conservation problems. It helps to utilize it in other research objectives targeting in automated defect-recognition and multisensory technology. It helps to advance theoretical and practical routines in everyday practices of art conservation applications, to confirm the direct fringe pattern concept in a new diagnostic field, and develop associations to cause-effect relations in other art conservation problems.