3D high resolution techniques applied on small and medium size objects: from the analysis of the process towards quality assessment

The need for metric data acquisition is an issue strictly related to the human capability of describing the world with rigorous and repeatable methods. From the invention of photography to the development of advanced computers, the metric data acquisition has been subjected to rapid mutation, and nowadays there exists a strict connection between metric data acquisition and image processing, Computer Vision and Artificial Intelligence. The sensor devices for the 3D model generation are various and characterized by different functioning principles. In this work, optical passive and active sensors are treated, focusing specifically on close-range photogrammetry, Time of Flight (ToF) sensors and Structured-light scanners (SLS). Starting from the functioning principles of the techniques and showing some issues related to them, the work highlights their potentialities, analyzing the fundamental and most critical steps of the process leading to the quality assessment of the data. Central themes are the instruments calibration, the acquisition plan and the interpretation of the final results. The capability of the acquisition techniques to satisfy unconventional requirements in the field of Cultural Heritage is also shown. The thesis starts with an overview about the history and developments of 3D metric data acquisition. Chapter 1 treats the Human Vision System and presents a complete overview of 3D sensing devices. Chapter 2 starts from the enunciation of the basic principle of close-range photogrammetry considering digital cameras functioning principles, calibration issues, and the process leading to the 3D mesh reconstruction. The case of multi-image acquisition is analyzed, deepening the quality assessment of the photogrammetric process through a case study. Chapter 3 is devoted to the range-based acquisition techniques, namely ToF laser scanners and SLSs. Lastly, Chapter 4 focuses on unconventional applications of the mentioned high-resolution acquisition techniques showing some examples of study cases in the field of Cultural Heritage.