The fifth edition of the optical metrology conference devoted to cultural heritage methods, also third edition of O3A, is focused on advanced optical methodologies for the study, documentation, safeguard, preservation and conservation of cultural heritage. The symposium will be an ideal place for exchanging ideas and discussing best practices for the optical analysis of artworks. Submissions will be targeted on general studies, new techniques as well as experimental applications on relevant case-studies. Major applications and studies are expected in today's most active research fields such as terahertz imaging, optical coherence tomography, imaging spectroscopy, luminescence imaging, 3D analyses, laser-based methods and many more.