 In 1900, he was invited to join the Zeiss Optical Works company in Jena, Germany, by Siegfried Czapski based on his earlier work on improving microscope illumination.He stayed with Zeiss as a physicist for 45 years and became instrumental to the development of modern light microscope design.From 1922 until his retirement in June 1945, he was also professor for microphotometry at the University of Jena.