Techniques for Effective Optical Noise Rejection in Amplitude-Modulated Laser Optical Radars for Underwater Three-Dimensional Imaging

Amplitude-modulated (AM) laser imaging is a promising technology for the production of accurate three-dimensional (3D) images of submerged scenes. The main challenge is that radiation scattered off water gives rise to a disturbing signal (optical noise) that degrades more and more the quality of 3D images for increasing turbidity. In this paper, we summarize a series of theoretical findings, that provide valuable hints for the development of experimental methods enabling a partial rejection of optical noise in underwater imaging systems. In order to assess the effectiveness of these methods, which range from modulation/demodulation to polarimetry, we carried out a series of experiments by using the laboratory prototype of an AM 3D imager ( = 405 nm) for marine archaeology surveys, in course of realization at the ENEA Artificial Vision Laboratory (Frascati, Rome). The obtained results confirm the validity of the proposed methods for optical noise rejection

Improving underwater imaging in an amplitude-modulated laser system with radio frequency control technique

We present the results of an experiment aimed to demonstrate the low-pass filter dependence of water backscattered power in an amplitude-modulated laser scanner for underwater 3D imaging. We also demonstrate that improvements in target imaging are obtained by allowing the device to operate in the stop-band region. A simple model is described to account for the physics underlying the effect and suggesting future experimental schemes based on demodulated detection techniques

Two-wavelength infrared heterodyne transceiver (TWIHT) with a continuous phase tracking system

Submitted to Rev. Sci. InstrumSIGLEITItal

3D remote colorimetry and watershed segmentation techniques for fresco and artwork decay monitoring and preservation

One of the most crucial problems in cultural heritage environment is the remote monitoring of the state of monuments, especially of large surfaces (e.g. frescos, chapels). In 2011 a complete 3D colour digitization of the Sistine Chapel was executed by the RGB-ITR (Red Green Blue - Imaging Topological Radar) laser scanner prototype, developed by the UTAPRAD-DIM (Technical Unit for the development of APplications of RADiations - Diagnostics and Metrology) lab of C.R. ENEA Frascati. The preservation of the frescos is put at risk by the salt efflorescence (e.g., calcium carbonate) due to physical and chemical agents. These outcrops showing colours deterioration appear on the fresco as whitish areas of variable size. Within this framework, the scientific challenge is to provide a starting point for the non-invasive diagnosis of fresco degradation in order to contribute to the design and realization of innovative solutions for the restoration and conservation of the paintings, especially in presence of extended surfaces with difficult access. The present work shows the results obtained by the integration of two techniques, based on the RGB-ITR hyper-photos and the watershed algorithm for a semi-automatic detection of defects on fresco. The study case concerns the fresco located inside the Sistine Chapel known as "Temptations of Christ" by Sandro Botticelli

Test del laser range finder per il RAS effettuati durante la campagna al Passo del Tonale (Aprile 2001)

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal