Later he quit Rollei and worked as an independent designer. He worked on the ideas of Hans Domnick who was proposing a system of cassettes, interchangeable in mid film, and made a prototype of a cassette SLR with the Rolleiflex SL35 lens mount.
At the same time, he was working on various design concepts for Minox, among which the Minox 645 GL (a 4.5x6 folding rangefinder camera), a 35mm interchangeable lens rangefinder camera and evolutions of the Minox 35 with interchangeable lenses. For Carl Zeiss he developed a film cassette for the Axiophot microscopes. His latest developments were automatic room control cameras for film.