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 Carl Zeiss AG. Zeiss gathered a group of gifted practica ...

Jena Jena () is a German city 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 inhabitants, while the city itself has a po ...

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwee ...

. 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: ''Prūsa'' or ''Prūsija'' was a German state on the southeast coast of the Baltic Sea. It formed the German Empire under Prussian rule when it united the German states in 1871. It was ''de facto'' dissolved by an e ...

Grand Duchy of Posen The Grand Duchy of Posen (german: Großherzogtum Posen; pl, Wielkie Księstwo Poznańskie) was part of the Kingdom of Prussia, created from territories annexed by Prussia after the Partitions of Poland, and formally established following the ...

, but now in

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It is divided into 16 administrative provinces called voivodeships, covering an area of . Poland has a population of over 38 million and is the fifth-most populou ...

and known as Łążyn, near Inowrocław. He obtained a

doctorate of philosophy A Doctor of Philosophy (PhD, Ph.D., or DPhil; Latin: or ') is the most common degree at the highest academic level awarded following a course of study. PhDs are awarded for programs across the whole breadth of academic fields. Because it is ...

at the

University of Berlin Humboldt-Universität zu Berlin (german: Humboldt-Universität zu Berlin, abbreviated HU Berlin) is a German public research university in the central borough of Mitte in Berlin. It was established by Frederick William III on the initiative ...

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 (optics), lens whose surface profiles are not portions of a sphere or Cylinder (geometry), cylinder. In photography, a camera lens, lens assembly that includes an aspheri ...

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 furthest objects that are in acceptably sharp focus in an image captured with a camera. Factors affecting depth of field For cameras that can only focus on one object dis ...

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 front (the object side) of the lens system. The corresponding image of the aperture as seen through the back of the lens system ...

location and diameter, without reference to

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

and

f-number In optics, the f-number of an optical system such as a camera lens is the ratio of the system's focal length to the diameter of the entrance pupil ("clear aperture").Smith, Warren ''Modern Optical Engineering'', 4th Ed., 2007 McGraw-Hill Pro ...

(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