Joseph Braat is Emeritus Professor of Optics at Technische Universiteit Delft, The Netherlands, and a Fellow of the Dutch Royal Academy of Arts and Sciences. Previously he was based at the Philips Research Laboratories in Eindhoven where he worked on optical disc systems for video and audio recording and on high-resolution optical lithography. He was Co-Founder of the European Optical Society and his further research interests are diffraction theory, astronomical imaging and optical metrology.