"Laser scanning technologies for 2D and 3D imaging and characterization of decorated monumental surfaces"
Résumé
Laser scanning prototypes, formerly developed in active remote sensing systems and in remote
vision and metrology devices based on the amplitude modulation technique, have been specialized
for high resolution multispectral applications suitable to be used in the characterization of large
surfaces relevant to monumental Cultural Heritage.
A three colour imaging topologic radar (RGB-ITR) has been developed for high resolution 3D
imaging of frescos and successfully utilized in chapels of churches dating back to the Renaissance
period. The high resolution 3D models reconstructed have allowed the hyper-realistic rendering of
coloured features and the identification of surface irregularities, either in the layers or in the
thickness of the underlying plaster, possibly related to otherwise undetectable damages.
A laser induced fluorescence scanning system, capable of 2D monochromatic images acquisition
on up to 90 different spectral channels in the visible/UV range has been developed and utilized in
field campaigns in order to investigate the presence and the aging of consolidants as well as the
occurrence of bio degradation. Its utilization in combination with the RGB-ITR on the same field
campaign is reported. A new prototype with a line scanner facility for high speed data acquisition
has been recently realized and is currently under laboratory tests.
Different methods for image classification are presented, examining the possibilities offered for
data fusion from different active and passive sensors, based on both optical and acoustical
techniques. Two methods have been selected for LIF data processing software, one based on
spectral angle mapper and the other one on principal component analysis. Both methods have
been implemented to extract the information relevant to conservation strategy and visualize
damaged areas in suitable false colour combinations of the collected images.
Eventually, an augmented reality system with the possibility of projecting the image
reconstruction on the real target has been realized as a tool for accurate surface study and for
better fruition.
Results on data collected in preliminary laboratory investigations on reference materials and
during a recent field campaign on frescos and are reported and discussed
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