Topogon

Topogon is a wide field (originally 100 degrees field of view), symmetrical photographic lens designed by Robert Richter in 1933 for Zeiss Carl FA.[1] Lenses produced under the name Metrogon also cite the US patent of the Topogon design. The initial design patented by Richter was for a f=66mm f/6.3 lens, although the patent also contains two other refinements to the basic design, including one that used parallel elements to minimize vignetting.[1]

Topogon
Introduced in1933
AuthorRobert Richter
Construction4 elements in 4 groups
Aperture6.3

Topogon lenses have been produced with maximum apertures ranging from f/3.5 to f/15 in various focal lengths.[2] According to Richter, the Topogon was developed from the earlier Hypergon.[3][4] Although the Hypergon covered a wide angle of view (140°) and had good flatness of field and distortion characteristics, the maximum aperture was limited to f/22 to control longitudinal spherical aberration and chromatic aberration. A new computation of a "fast" Hypergon was made by limiting the angle of view to 90°, increasing maximum aperture to f/6.3. The Topogon was then derived from the "fast" Hypergon by adding a second set of strongly curved meniscus elements inboard of the larger spherical elements to correct longitudinal spherical aberration.[5]

The Topogon was later developed into the Pleogon lens by Richter and Friedrich Koch in 1956.[6] The Pleogon, used for photogrammetry, used a cemented achromatic lens just ahead of the central stop and added two meniscus groups on either side to maintain lens symmetry.[5]

References
  1. US 2031792, Robert Richter, "Anastigmatic objective for photography and projection", issued February 25, 1936, assigned to Carl Zeiss
  2. Cavina, Marco. "Hypergon - Topogon - Russar - Biogon - Aviogon - Hologon: La storia definitiva dei super-grandangolari simmetrici" [Hypergon - Topogon - Russar - Biogon - Aviogon - Hologon: The definitive history of the super-wide angle symmetric lenses]. Retrieved 8 November 2018.
  3. In the paper, Richter attributed the Hypergon design to Emil von Höegh; the 1900 patent for the Hypergon is credited to Carl Paul Goerz, a frequent collaborator with von Höegh.
  4. US Grant 706640, Carl Paul Goerz, "Astigmatically-corrected wide-angle objective", issued 12 August 1902, assigned to Carl Paul Goerz
  5. Richter, Robert (December 1956). "Development and Perfection of the Topogon Lens" (PDF). Photogrammetric Engineering & Remote Sensing. XXII (5): 868–874. Retrieved 9 November 2018.
  6. DE Application 1097710, Dr Robert Richter & Friedrich Koch, "Anastigmatisches lens", assigned to Carl Zeiss SMT GmbH
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