PICUS: A Pocket-Sized System for Simple and Fast Non-Destructive Evaluation of the Detachments in Ancient Artifacts

Giosuè Caliano,Francesca Mariani,Paola Calicchia

doi:10.3390/app11083382

Giosuè Caliano, Francesca Mariani + Show 1 more

Open Access

https://doi.org/10.3390/app11083382

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Abstract

An innovative, robust method has been developed, based on the use of a simple, compact, expressly designed device, named PICUS (the ‘woodpecker’ in ancient Latin), and inspired by the auscultation method carried out by the experts in the field of conservation of cultural heritage. This method entails gently knocking the surface, controlling and measuring the impact time of the stroke’s force, recording the generated sound, comparing the acquired sound with a reference sound by calculating the cross-correlation function, and its maximum, as a measure of the detachment. In a nutshell, it performs an analysis similar to that carried out by a professional who performs a routine examination on the detachments by hand. The experimental apparatus consists of a probe made of an electromechanical percussion element that gently taps the surface producing a sound, a force sensor purposely developed to measure the impact force, and a microphone, all connected with an Arduino-like low cost board, to record and elaborate the sounds and the force sensor signal. The probe XY position on the scene is recognized using an infra-red (IR) system with a low-cost IR camera and an IR light-emitting diode (IR-LED) positioned on the probe. The “tapper” and the microphone replace the hand and the ear of a conservator carrying out a detachment investigation, while the comparison with a reference is the typical mind process of a professional restorer. The result is the fusion of the microphone data and the force sensor data.

Highlights

Featured Application: A simple and low-cost “tester” of the state of conservation of cultural heritage decorated coverings e.g., wall paintings, mosaics, panels, tiles
We used a probe that, performing a signal processing based on a crosscorrelation algorithm, allows us to detect the detachments between adjacent layers and published maps and institutional affiliations
Using a force sensor integrated in the system, an impact-force measurement is made that allows us to measure detachments that produce sounds that cannot be perceived by the audio part of the instrument as they are outside the useful band of the used microphone

Summary

Introduction

Featured Application: A simple and low-cost “tester” of the state of conservation of cultural heritage decorated coverings e.g., wall paintings, mosaics, panels, tiles. Robust method has been developed, based on the use of a simple, compact, expressly designed device, named PICUS (the ‘woodpecker’ in ancient Latin), and inspired by the auscultation method carried out by the experts in the field of conservation of cultural heritage This method entails gently knocking the surface, controlling and measuring the impact time of the stroke’s force, recording the generated sound, comparing the acquired sound with a reference sound by calculating the cross-correlation function, and its maximum, as a measure of the detachment. The non-destructive investigations used in a laboratory to find detachments are hardly executable in situ For this reason, traditionally, conservators rely on the technique of auscultation, which entails gently knocking with the hand, and listening to the sound produced by the surface. From a fusion of the available data, it is possible to measure a wide range of detachments

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