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Biodeteriogens are an important cause of the weathering of a monument, particularly those made of stone, and their detection at an early stage of development helps to protect the monument from deterioration. Frequent mapping of biodeteriogen accumulation is therefore highly necessary. The use of fluorescence lidar for this purpose was introduced in 1995 and has been developed in subsequent years. Three main aspects emerged during this research: the possibility of discriminating between different biodeteriogen strains, the minimum detectable quantity of biodeteriogens, and the control of the efficiency of biocide treatments. We describe the results of a laboratory experiment devoted to clarifying these three aspects of biodeteriogen monitoring by means of fluorescence lidar.

What is believed to be the first fluorescence imaging of the facades of a historical building, which was accomplished with a scanning fluorescence lidar system, is reported. The mobile system was placed at a distance of ~60 m from the medieval Lund Cathedral (Sweden), and a 355-nm pulsed laser beam was swept over the stone facades row by row while spectrally resolved fluorescence signals of each measurement point were recorded. By multispectral image processing, either by formation of simple spectral-band ratios or by use of multivariate techniques, areas with different spectral signatures were classified. In particular, biological growth was observed and different stone types were distinguished. The technique can yield data for use in facade status assessment and restoration planning.

Laser-induced fluorescence spectra detected with high-spectral-resolution lidar on the facades of the Baptistery and the Cathedral in Parma are presented and discussed. The data show fluorescence features that are due to the stone materials that constitute the coating of the monuments and to photosynthetically active colonizations on their surfaces. This underlines the feasibility of a remote fluorescence analysis of historic facades. The data were also compared with the fluorescence lidar spectra obtained from similar lithotypes, sampled either in historic extraction areas or in sites exploited recently. The results open good prospects for spectral characterization of historic materials and identification of their provenance.

A laboratory experiment is discussed which simulates lidar fluorosensing of oil films on the sea surface at UV wavelengths. Three different mixtures of lasing gases, KrF, XeCl and N2 , were used while a fourth wavelength was given by a dye laser. It turns out that films having a thickness as low as 0.01 microm can be detected; the limiting factor resides mainly in the background fluorescence of water. Best results have been obtained with the XeCl excimer laser.