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Identifier

000456689

Title

Development of a novel photoacoustic imaging prototype for the non-destructive in-depth investigation of cultural heritage items

Alternative Title

Ανάπτυξη καινοτόμου φωτοακουστικού συστήματος απεικόνισης με στόχο τη μη καταστρεπτική, εις βάθος μελέτη αντικειμένων πολιτιστικής κληρονομιάς

Author

Κληρονόμου, Ευγενία Δ.

Thesis advisor

Μακρής, Κωνσταντίνος

Reviewer

Χαραλαμπίδης, Δημήτρης
Ζαχαράκης, Ιωάννης

Abstract

During this project a novel, non-destructive, photoacoustic imaging technique was developed and optimized, for the in-depth investigation of cultural heritage items. The experimental epi-illumination apparatus presented in this work, integrates laser excitation and respective signal detection on one side, aiming to provide universal information in objects of arbitrary thickness and shape. The apparatus is not only capable of the revelation of the underdrawings which are hidden under the different paint layers, but also of the creation of a cross-section along the z-axis, that reveals the stratigraphic profile of the sample. For the development of the technique and the evaluation of its capabilities, thickly painted mock-ups were created following historically accurate methods, on which different materials were used for the covering layers. The results were compared to photographs acquired with standard near-infrared imaging. The comparison of the techniques proved that photoacoustic signals reveal underlying sketches with up to 3.5 times improved signal to noise ratio (SNR). What is more, the ratio of the SNR values of the optimized system compared to the preexisting was improved up to 12.5 times. A basic requirement for the effective ultrasound propagation is the use of a coupling medium between the immersion-type transducer and the sample’s surface. Until now, the used coupling medium has been water. For the first time during this project, agarose gel was proposed as the coupling medium for the water-immersion transducers, which is a non-invasive alternative, already used in various conservation treatments on cultural heritage objects. The results were very promising since they demonstrated that the technique’s performance in agarose gel is comparable to that in water. Finally, the experimental apparatus was altered in order to measure a historical artwork of the nineteenth-century. The photoacoustic images revealed insight about the conservation methods that had taken place over the years. Overall, the photoacoustic imaging technique has proved itself to be a very effective imaging method that can provide additional information about the measured samples, when combined with other imaging techniques. We hope that in the future it will become a useful tool in the cultural heritage diagnostics and conservation field.

Language

English

Subject

Artwork conservation

Cultural heritage

Diagnostics

Photoacoustic imaging

Underdrawings

Πολιτιστική κληρονομιά

Προσχέδια

Συντήρηση έργων τέχνης

Φωτοακουστική απεικόνιση