Symmetric wide-angle lenses with meniscus elements facing the object and image had been developed in the 1930s, including the Schneider Kreuznach Angulon (Tronnier, 1930) with two outer negative menisci, derived from the Goerz Dagor (Emil von Höegh, 1892); and the Zeiss Topogon (Richter, 1933) with two outer positive menisci, derived from the Goerz Hypergon (1900). These concepts were combined in a symmetric super-wide angle lens design using mirrored inverted telephoto lenses, as patented by Roosinov in 1946.
