Reflections about holographic and non-holographic acquisition of surface topography

Recording and (computational) processing of complex wave fields offers a vast realm of new optical methods. Also for optical 3D-metrology. We discuss fundamental similarities and differences of holographic surface topography measurement versus non-holographic principles, such as triangulation, classical interferometry, rough surface interferometry and slope measuring methods. Key features are the physical origin of the ultimate precision limit and how the topographic information is encoded and decoded. We demonstrate that the question "is holography just interferometry?" has different answers, depending on how we exploit holograms or interferograms for metrology. The answers will help users to find out if their measurement results could be improved or if they already hit the ultimate limit of what physics allows.