In the field of the management of cultural heritage, it is well known the necessity of acquiring a documentation, the most complete and accurate as possible, on works of art belonging to the common cultural patrimony. The aim is to maintain their state of conservation under continuous control.
Besides to carry out classification tasks, this documentation would allow one to foresee and plan conservative actions by preventing the spread and worsening of degradation phenomena.
Focusing on architectonic structures and frescoes on non planar surfaces, the correlation between geometric (shape and dimension of the artefact) and colorimetric measurements assumes a great importance in the aforesaid documentation.
In this context there is a demand for a flexible instrumentation, multifunctional, easy to use and to transport, that, at the cost of a possible loss in accuracy with respect to traditional instrumentations, allows a wider and diffuse collection of these information.
In order to fulfil these requirements, within the field of the research activities of the Artificial Vision group of IEIIT in Turin, activities related to the survey and reconstruction of 3D surfaces, an Active Vision System able to carry out accurate dimensional and colorimetric measurements on volumes of some tens of cubic meters has been designed and realized.
The system is comprised of three TV cameras aligned along a horizontal axis. The central camera, equipped with a wide-angle lens, allows one to frame the scene of interest at low resolution and, through the processing of the acquired image, to drive the two lateral cameras to fixate those features that turn out being of interest for some reason. The lateral cameras, which are digital and completely controlled by a personal computer, are equipped with long focal-length lenses allowing them to examine small portions of the scene at high resolution. One of these cameras is equipped with spectral filters allowing it to carry out CIE X Y Z and L*a*b* colorimetric measurements.
On the whole, the system is provided with 3 mechanical and 5 electro-optical degrees of freedom.
A powerful and user-friendly graphical interface allows the user to control all cameras parameters, to start image acquisition and to run all system functions. The system is transportable and can operate both indoors and outdoors . The currently implemented functions are:
- extraction, fixation and 3D measurement of natural (characteristic points) and artificial targets;
- acquisition of correlated geometric and colorimetric information with high resolution, both around characteristic points and over wider regions of the scene interactively selected by the operator;
- 3D reconstruction of surfaces from pairs of high resolution stereo images;
- scene monitoring.
The activity has been carried out in cooperation with IENGF and IMGC-CNR and has been funded from both the P.F. "Beni Culturali" and the "Progetto SIINDA" of the P.N. Parnaso.
Besides its natural utilization in the Cultural Heritage field, the Active Vision System can find application in industrial production and in the cinematographic field (virtual reality) as well.
Future developments of the system concern the validation of its performances and the optimization of its functions.
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