Moritz von Rohr (4 April 1868 – 20 June 1940) was an optical scientist at

Carl Zeiss Carl Zeiss (; 11 September 1816 – 3 December 1888) was a German scientific instrument maker, optician and businessman. In 1846 he founded his workshop, which is still in business as Zeiss (company), Zeiss. Zeiss gathered a group of gifted p ...

Jena Jena (; ) is a List of cities and towns in Germany, city in Germany and the second largest city in Thuringia. Together with the nearby cities of Erfurt and Weimar, it forms the central metropolitan area of Thuringia with approximately 500,000 in ...

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

. A street in Jena is named after him: Moritz-von-Rohr-Straße, near Carl-Zeiss-Promenade and Otto-Schott-Straße.

Life

Moritz von Rohr was born in Lonzyn near Hohensalza, then part of the

Prussia Prussia (; ; Old Prussian: ''Prūsija'') was a Germans, German state centred on the North European Plain that originated from the 1525 secularization of the Prussia (region), Prussian part of the State of the Teutonic Order. For centuries, ...

Grand Duchy of Posen The Grand Duchy of Posen (; ) was part of the Kingdom of Prussia, created from Prussian Partition, territories annexed by Prussia after the Partitions of Poland, and formally established following the Congress of Vienna in 1815. On 9 February 1 ...

, but now in

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It extends from the Baltic Sea in the north to the Sudetes and Carpathian Mountains in the south, bordered by Lithuania and Russia to the northeast, Belarus and Ukrai ...

and known as Łążyn, near Inowrocław. He obtained a doctorate of philosophy at the

University of Berlin The Humboldt University of Berlin (, abbreviated HU Berlin) is a public research university in the central borough of Mitte in Berlin, Germany. The university was established by Frederick William III on the initiative of Wilhelm von Humbol ...

in 1892.

Inventions

Von Rohr is usually credited with the design of the first

aspheric lens An aspheric lens or asphere (often labeled ''ASPH'' on eye pieces) is a lens whose surface profiles are not portions of a sphere or cylinder. In photography, a lens assembly that includes an aspheric element is often called an aspherical lens. ...

es for eyeglasses. He invented the eyeglass lens designs that became the Zeiss Punktal lenses. He also developed a method of computing

depth of field The depth of field (DOF) is the distance between the nearest and the farthest objects that are in acceptably sharp focus (optics), focus in an image captured with a camera. See also the closely related depth of focus. Factors affecting depth ...

from a camera's

entrance pupil In an optical system, the entrance pupil is the optical image of the physical aperture stop, as 'seen' through the optical elements in front of the stop. The corresponding image of the aperture stop as seen through the optical elements behin ...

location and diameter, without reference to

focal length The focal length of an Optics, optical system is a measure of how strongly the system converges or diverges light; it is the Multiplicative inverse, inverse of the system's optical power. A positive focal length indicates that a system Converge ...

and

f-number An f-number is a measure of the light-gathering ability of an optical system such as a camera lens. It is calculated by dividing the system's focal length by the diameter of the entrance pupil ("clear aperture").Smith, Warren ''Modern Optical ...

(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''.

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." Von Rohr wrote several books on optics, optical instruments, and photographic lenses, in German. * 1899 ''Theorie und Geschichte Des Photographischen Objecktivs'', Berlin: Verlag 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.

Photographs

Photographs of von Rohr and more information about him are available on the Zeiss website and the AntiqueSpectacles site.Honor Roll of Distinguished Persons
at www.antiquespectacles.com

References

External links

Prof. Dr. Moritz von Rohr, "The First Jena Catalogue of Optical Glasses Published in 1886", ''Supplement to "Current Science"'', Vol. 5, July 1936. {{DEFAULTSORT:Rohr, Moritz von 1868 births 1940 deaths Scientists from Jena People from Toruń County People from the German Empire