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Moritz von Rohr

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Von Rohr's method of DOF calculation involves projecting object points to circles of confusion in the field plane (Einstellebene), with reference to the entrance pupil (Eintrittspupille) P. The caption is translated as: "Fig. 20. Concerning depth with photographic lenses. The upper and lower parts of the figure are identical in the position of the field plane, entrance pupil and the object. The only difference is the diameter of the entrance pupil, the upper being twice the size of the lower. For this reason the upper circles of confusion o1 o2 are also twice the size of the lower ones at the field plane O and the object side image o1 O o2 is twice as blurry as the lower. (By accident the print in the upper field plane O says O1 instead of o1.)"

Moritz von Rohr (1868–1940) was an optical scientist at Carl Zeiss in Jena.

A street in Jena is named after him: Moritz-von-Rohr-Straße, near Carl-Zeiss-Promenade and Otto-Schott-Straße, reminders of the proud optical heritage of the city.

Life

Moritz von Rohr was born at Lazyn near Inowraclaw, Poland. He obtained a Ph.D. at the University of Berlin in 1892.

Inventions

M. von Rohr is usually credited with the design of the first aspherical lenses, though early attempts at making aspherical lenses to correct spherical aberration were made by René Descartes in the 1620s, and by Constantijn Huygens in the 1630s. The Visby lenses produced by Vikings on the island of Gotland in the 10th or 11th century are also aspheric, but there is no evidence that the science behind the technique was known, they were 'simply' produced by craftsmen working from experience of what worked.

He invented the eyeglass lens designs that became the Zeiss Punktal® lenses.

He also developed a method of computing depth of field from a camera's entrance pupil location and diameter, without reference to focal length and f-number (see his 1904 and 1906 books). He says, "At this point it will be sufficient to note that all these formulae involve quantities relating exclusively to the entrance-pupil and its position with respect to the object-point, whereas the focal length of the transforming system does not enter into them." T. R. Dallmeyer refers to "von Rohr’s interpretation" of depth of field in his 1899 book Telephotography.

Illustration of von Rohr's method to construct front and near DOF limits from the outside-the-box parameters, aperture diameter d and angular circle of confusion limit e.

Publications

According to the Focal Encyclopedia of Photography (1965), "A bibliography of his 571 books and articles was published in Forschungen zur Geschichte der Optik, 1943."

M. von Rohr authored several books on optics, optical instruments, and photographic lenses, in German.

  • 1899 Theorie und Geschichte Des Photographischen Objecktivs, Berlin: Verl. von Julius Springer
  • 1904 (editor) Die Bilderzeugung in optischen Instrumenten vom Standpunkte der geometrischen Optik, Berlin: J. Springer
  • 1906, 1911 Die optischen Instrumente, Leipzig: B. G. Teubner
  • 1920 Die binokularen Instrumente, Berlin: J. Springer

The 1899 book was reprinted: Sources of Modern Photography series, New York: Arno Press, 1979.

The 1904 book was translated into English:

  • 1920 Geometrical Investigation of the Formation of Images in Optical Instruments, London: H. M. Stationery Office

In 1936 he published a retrospective "The First Jena Catalogue of Optical Glasses Published in 1886" in Supplement to "Current Science", which is available online.

Photos

Photos of, and more information about, Herr Dr. Prof. von Rohr are available on the Zeiss site and the AntiqueSpectacles site .

References

  1. Rudolf Kingslake (1989). A History of the Photographic Lens. Elsevier. ISBN 0124086403.

External links

  • Page images: "The First Jena Catalogue of Optical Glasses Published in 1886", Supplement to "Current Science", Vol. 5, July 1936.
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