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Fotothek df tg Optik Instrument Dioptrik Brechung Linse konvex konkav. Scan Deutsche Fotothek dftg color MIKCenter Berlin GmbH Tabula Lib Wien Frankfurt Main Zerstreuungslinsen Linsensysteme Papier Kupferstich cm Optik Instrument Dioptrik Brechung Linse konvex konkav ppnX Druck Deutsche Fotothek gefrdert von der Deutschen