Guido (Augustus J.E.M.) Janssen received his Engineering and PhD degree in Mathematics from the Eindhoven University of Technology, The Netherlands, in 1976 and 1979, respectively. From 1979 to 1981 he was a Bateman Research Instructor at the Mathematics Department of California Institute of Technology. From 1981 until 2010 he worked with Philips Research Laboratories, Eindhoven, where he was a Research Fellow since 1999 and recipient of the Gilles Holst award in 2003. His principal responsibility at Philips Research was to provide high-level mathematical service and consultancy in mathematical analysis. He continues his research and consultancy activities from his current affiliations TU/e, EURANDOM (LG 1.39) and Department EE, with further contacts with TU-Delft (Optics) and ASML. In 2003, he was elected Fellow of the IEEE for his contributions to mathematical time-frequency analysis and signal processing. Dr. Janssen has published over 170 papers in the fields of Fourier Analysis, Signal Analysis, Time-Frequency Analysis, Electron Microscopy, Optical Diffraction Theory, Acoustics, and Queueing Theory, and his current interests include the application of mathematical techniques as used in the theory of optical aberrations to the characterization of acoustical radiators.