Amplitude-modulated laser range-finder for 3D imaging with multi-sensor data integration capabilities

摘要

A high performance Amplitude Modulated Laser Rangefinder (AM-LR) is presented, aimed at accurately reconstructing 3D digital models of real targets, either single objects or complex scenes. The scanning system enables to sweep the sounding beam either linearly across the object or circularly around it, by placing the object on a controlled rotating platform. Both phase shift and amplitude of the modulating wave of back-scattered light are collected and processed, resulting respectively in an accurate range image and a shade-free, high resolution, photographic-like intensity image. The best performances obtained in terms of range resolution are ～100 μm. Resolution itself can be made to depend mainly on the laser modulation frequency, provided that the power of the backscattered light reaching the detector is at least a few nW. 3D models are reconstructed from sampled points by using specifically developed software tools, optimized so as to take advantage of the system peculiarities. Special procedures have also been implemented to perform precise matching of data acquired independently with different sensors (LIF laser sensors, thermographic cameras, etc.) onto the 3D models generated using the AM-LR. The system has been used to scan different types of real surfaces (stone, wood, alloys, bones) and ca be applied in various fields, ranging from industrial machining to medical diagnostics, vision in hostile environments cultural heritage conservation and restoration. The relevance of this technology in cultural heritage applications is discussed in special detail, by providing results obtained in different campaigns with an emphasis on the system's multi-sensor data integration capabilities.