Recent developments in 3D multi-modal laser imaging applied to cultural heritage

This paper proposes a novel multi-modal three-dimensional (3D) laser scanning system that combines high-accuracy 3D laser imaging, very high-resolution perspective color projection, and on-site geometric calibration of the intrinsic and extrinsic parameters. Motion compensation directly from the range measurements using ICP and a 6-DOF self-built model tracking is also used to eliminate the need for stable mechanical structures and external positioning sensors. We show that scanner performances, modeling, and visualization are intimately linked and must be considered as an integral part of the modeling chain. This is particularly important in the field of heritage where the acquisition must adapt to the environment. Equations and charts are presented to compute the optimum color camera and laser scanner configuration for a given 3D modeling application in terms of camera settings such as optimum lens aperture, focal length, optimum range, and total range depth. These equations are general and can be used for most 3D acquisition systems including time-of-flight laser scanners. Experimental results are presented to demonstrate the validity of the approach.