Structured light (SL) scanners have been commercially available for over a decade and some commercial scanners are evaluated using one of two German guidelines VDI/VDE 2634 parts 2 and/or 3. Several other research groups and NMIs have developed physical artifacts that are agnostic to instrument construction and are purpose driven. The use of such guidelines and artifacts is not well understood for instruments which have variety of sensor configurations, projected patterns, sensor/work volumes, point densities, triangulation angles and targets of varying size & form. It is also not clear if these guidelines/artifacts are sensitive to all the sources of errors that are present in these systems. The two VDI/VDE 2634 guidelines for evaluating the performance of the SL scanners use artifacts of known mechanical and optical characteristics, but the real-world usage of these scanners may involve objects of varying characteristics. The end user may not be able to make informed decisions if an instrument is specified based on these guidelines/standards but is used for an application that deviates from the test conditions. This can cause an enormous financial burden for organizations that intend to invest in the technology, but do not have appropriate standards to aid in selecting an instrument that meets their needs. In this context, this paper will describe the ongoing activities at NIST to study various sources of errors in SL scanners with an objective of characterizing their performance. The paper will first give some background information on the principle of operation of SL scanners, the state-of-the-art of documentary standards/artifacts and describe some scanners available to the authors. The paper will then discuss the various sources of errors in SL scanners that influence their measurements and describe a few experiments that were performed to understand some of these errors.
April 16-18, 2019
SPIE Defense and Commercial Sensing 2019
Structured light scanners, Optical triangulation 3D scanners, documentary standards, imaging systems