Harthmuth says: My background is in physics and optical engineering (Optical Institute in Berlin, Germany) with an overall experience of more than 30 years in development and manufacture of various optics (VIS, NIR), e.g. lenses (with spherical and/or aspherical surfaces) for cameras, photocopiers, projectors, laser diodes, LEDs, endoscopes, microscopes, optical and opto-electronical sensors, spectrometers, interferometers. After an activity in optics industry in Germany and at a Research and Technology Center in Switzerland, I founded OCB Sàrl in 1991 as a small independant consultancy company, offering its services in optical design and engineering. Since 1993 I am using Zemax for my work, meanwhile Zemax became my principal tool for virtually all optical design tasks. So I am quite experienced to use the different functions and options that Zemax offers, like sequential and non-sequential mode for raytracing and performance analysis, tolerancing, stray light analysis and so on.