3D laser Imagery with focal plan

Controlling the speed of motorists, taking topographic measurements, characterizing forests, mapping industrial sites from a drone, inspecting power lines from a helicopter, or providing 3D vision for a robot or autonomous vehicle.... All these applications use the same technique, 3D LiDAR, which measures the distance between an object and the instrument. This laser-based detection system has become indispensable in a wide range of applications, particularly in the field of autonomous vehicles, whose advent could mark its golden age. The associated measurement methods are usually classified into three categories: interferometry, triangulation methods and time-of-flight. This article will not deal with interferometric or triangulation methods, which are not suited to the distance domain covered by this article. For the use of 3D methods based on interferometric techniques, the authors recommend [R 1 320] and [R 1 332] for triangulation methods.

Significant advances in laser sources, detectors and processing capabilities in recent years have made time-of-flight measurement methods an attractive option. Indeed, 3D LiDAR is an active imaging technique that enables rapid, accurate acquisition of three-dimensional spatial information about an object. Over the last 20 years, this technology has evolved considerably in terms of the richness of the information it delivers, the compactness of its instruments and the quality of its processing. The aim of this article is to provide an understanding of the measurement physics associated with this technique, its operating modes linked to source types, and the detection methods used. The three main operating principles of such a LiDAR are based on direct time-of-flight measurement, amplitude or frequency modulation. This is followed by a presentation of the technologies used. Finally, two applications are detailed to illustrate the potential of this technique. The first focuses on short/medium-range telemetry for navigation (a few tens of meters) and the second on long-range telemetry for mapping (beyond the kilometer).