Semi-automatic system for UV images analysis of historical musical instruments

Abstract

The selection of representative areas to be analyzed is a common problem in the study of Cultural Heritage items. UV fluorescence photography is an extensively used technique to highlight specific surface features which cannot be observed in visible light (e.g. restored parts or treated with different materials), and it proves to be very effective in the study of historical musical instruments. In this work we propose a new semi-automatic solution for selecting areas with the same perceived color (a simple clue of similar materials) on UV photos, using a specifically designed interactive tool. The proposed method works in two steps: (i) users select a small rectangular area of the image; (ii) program automatically highlights all the areas that have the same color of the selected input. The identification is made by the analysis of the image in HSV color model, the most similar to the human perception. The achievable result is more accurate than a manual selection, because it can detect also points that users do not recognize as similar due to perception illusion. The application has been developed following the rules of usability, and Human Computer Interface has been improved after a series of tests performed by expert and non-expert users. All the experiments were performed on UV imagery of the Stradivari violins collection stored by "Museo del Violino" in Cremona.

Color‐based automatic detection of worn out varnishes on Stradivari's “Scotland University” violin back plate

“…Results obtained by analyzing the same UVIFL images of “Scotland University” back plate with the present and the previously reported systems are compared in Fig. .…”

“…1. We choose this violin because it was also analyzed by the previously described program, 11 thus it was possible a comparison between the two outcomes. We focused only on back plate, because, as mentioned in the introduction section, this is the area of the instrument more subject to mechanical consumption and to decay induced by sweat.…”

“…In one of our previous works we developed a program for speed up the analysis of UVIFL images, aiming to provide an interactive tool for helping the researchers in the retrieval of similar colors (a clue of similar material) on the surface of an instrument. In that case, the user selects a small sample region on the image, then the program extracts the main color features of that area in terms of Hue, Saturation, and Value, and finally all the regions of the surface with a color “close” to the chosen one are automatically highlighted.…”

“…Varnish wear is usually more evident on the back plates because they are directly in contact with the players, and therefore they are more subject to mechanical wear. The proposed approach extends one of our previous works using its results as input of a new program able to detect the presence of wear automatically, searching for specific UV fluorescence colors. The new application was tested on UVIFL photographs of Stradivari's “Scotland University” violin (1734).…”

A Silicon Carbide 256 Pixel UV Image Sensor Array Operating at 400 °C

“…Many applications, not limited to astronomy, clinics, combustion detection and art, have a strong demand in UV-only photography [1], [2], [3]. Some of them also request the durability of the hardware (e.g., image sensor) in extremely high temperature environments [4], [5], [6], [7], [8].…”